2005 Highlights

2006 Highlights

2008 Highlights

December 21, Dec. 28, 2007 & January 4, 2008

Theory Group

A new version of the DG code was released this week to seven users at various institutions around the world. DG is a graphical user interface program used to define computational grids input to tokamak scrape-off layer and edge plasma simulation codes. Current applications of DG include B2-EIRENE simulations of the ITER divertor (Andre Kukushkin, ITER) and DEGAS 2 neutral transport simulations of NSTX experiments (Daren Stotler). The new release incorporated improvements made by Alan Chin, a SULI intern at PPPL the past two summers, and a complete update of the User's Manual by Daren Stotler.

Jay Johnson & Eun-Hwa Kim attended AGU fall meeting and GEM workshop on 12/9 - 12/14 in San Francisco, CA. Jay Johnson organized a session on "Entropy Constraints on Plasma Entry, Tail Transport, and Magnetospheric State Transitions" at the American Geophysical Union Meeting. The session highlighted the following important science questions: why is entropy not conserved along field lines during earthward convection?; what are the dynamics of entropy bubbles and what is their role in ring current injections?; what does non-conservation of entropy during substorms tell us about the dynamical transition between growth phase and expansion phase?; how does plasma entry from the solar wind and loading from the ionosphere affect total and local measurements of entropy and what transport processes are responsible for the significant changes in entropy observed in the magnetospheric system? Eun-Hwa Kim presented two papers, which were Kinetic Alfven wave at the low latitude boundary layer by Eun-Hwa Kim and Jay R Johnson and Mode Conversion of Langmuir to Electromagnetic Waves at Oblique Density Inhomogeneities by Iver H Cairns, Eun-Hwa Kim, and Peter A. Robinson.

CPPG Group

The M3D-C1 development effort has met a major milestone by completing and demonstrating an initial 3D toroidal linear stability capability. The linear option of the M3D-C1 code initializes from a steady state toroidal equilibrium computed by either a Grad-Shafranov solver, or by the 2D M3D-C1 code: a comprehensive 2-fluid non-linear 2D toroidal evolution code with flow. The linear option then uses an efficient implicit time advance to evolve a given toroidal harmonic in time in order to find any unstable eigenmodes. The linear code contains full 2-fluid physics described by 9 scalar 3D fields, including the Hall term and the gyroviscous tensor. A feature of the M3D-C1 approach is that there are several well-posed non-trivial subsets of equations that can be solved instead of the full set of 9 scalar variables. These are: (1) 2-variable reduced MHD and (2) the 4-field 2-fluid equations of [Hazeltine, et al. PF 28 2466 (1985)] and [Fitzpatrick et al, PoP 11 p4713 (2004)]. This capability is invaluable in both debugging the full code and in better understanding the results. The initial capability verification tests are with the 2-variable option. Future development effort will include verifying the 4 and 9 variable options, adaptive meshing, a resistive wall capability, and active feedback. The 2D M3D-C1 code and the linear 3D option both have demonstrated good scaling on parallel computing platforms. The structure of the software is such that it leads directly into a scalable nonlinear 3D capability. This work was done in collaboration with the CEMM SciDAC team, the SCOREC team at RPI, and with Princeton University graduate student N. Ferraro.

December 14, 2007

Theory Group

An article titled "Charge and Current Neutralization of an Ion-Beam Pulse Propagating in a Background Plasma along a Solenoidal Magnetic Field" by I. D. Kaganovich, E. A. Startsev, A. B. Sefkow, and R. C. Davidson has been published in December issue of Physical Review Letters. The paper describes that the presence of the solenoidal field introduces the possibility of exciting a wide range of collective excitations, whose effects must be minimized/controlled for beam focusing schemes.

Leonid Zakharov visited Culham Science Center (December 2-12, 2007) for a Meeting on disruptions forces in ITER as they are scaled from JET data.  He has worked out a theory explaining existence of the kink mode during disruptions even when the safety factor q is greater than unity. The model seems to be consistent with the toroidal asymmetry in magnetic measurements, values of vertical and sideway forces observed on JET, and it motivates numerical simulations of the effect for understanding and resolving the issue for ITER.

CPPG Group

An "equilibration module" has been developed and tested for TRANSP/PTRANSP which can turn off recalculation of heating and current drive sources if the target plasma equilibrium and parameters have been unchanging for "long enough".  In a standard ITER discharge simulation test case, the runtime for sources was reduced by ~40% by using this option whereas the macroscopic results compared to a simulation without this option invoked appear to be equivalent.  This option is presently available, and should also work for TSC/TRANSP combined runs.   For additional details please see:  TRANSP HELP. http://w3.pppl.gov/~pshare/help/transp.htm -- search for the keyword "equilibration".

The TORIC ICRF full wave solver code has been brought up-to-date in TRANSP.  This work was carried out as collaboration between PPPL CPPG and the JET TRANSP team, in consultation with the TORIC authors at IPP/Garching and MIT.  This update is a step in the direction of using in TRANSP a version of TORIC which can use detailed distribution function data in computation of wave field damping on non-Maxwellian target ion species.

December 7, 2007

Theory Group

Wei-Li Lee and Daren Stotler as well as Ravi Samtaney, Eliot Feibush, and Stephane Ethier (CPPG) attended the Center for Plasma Edge Simulation (CPES) All Hands Meeting at Oak Ridge National Laboratory on December 3 and 4.  Samtaney presented an overview of the applied math work being done as part of the CPES project, including the effort to couple the XGC edge plasma turbulence code to the M3D nonlinear MHD code.   Stotler provided a progress report on his efforts to replace the neutral particle transport routines in XGC with ones based on the DEGAS 2 Monte Carlo neutral transport code.  Feibush gave an introduction to the MDSplus database system and suggested an initial approach to storing XGC data in MDSplus to facilitate comparison with experimental data.  Lee described the effects of profile relaxation in steady state delta-f simulations of ITG modes.

Wei-li Lee gave a Theory Seminar entitled "Nonlinear Effects in Steady State Ion Temperature Gradient Drift Turbulence Simulation." The talk, which was based on his recent collaborations with R. Ganesh (IPR, India), S. Ethier, R. Kolesnikov, W. X. Wang, J. Manickam and W. M. Tang, focused on the nonlinear physics associated steady ion temperature gradient (ITG) drift turbulence using global delta-f gyrokinetic particle simulation. The relative importance between the nonlinearly generated zonal flows and the velocity space nonlinearity was found to be dependent on the size of the simulation plasma due to the global nature of the flow in the presence of the velocity space nonlinearity. The simulation also showed that profile relaxation in the simulation had negligible effect on the steady state turbulence. Instead, the nonlinear fluctuations and the ion thermal diffusivity were closely related to the zeroth-order plasma inhomogeneities.  Understanding these properties of the steady state turbulence will be essential for the design of the algorithms for the multiscale integrated simulation of the Fusion Simulation Project (FSP) in the future.

CPPG Group

S. Jardin and J. Breslau (Theory) attended a special SWIM project meeting at the University of Wisconsin.  The focus of the meeting was a progress report and further planning for the SWIM "slow MHD" campaign in which the interaction of the heating systems with the plasma during the course of the instability is of interest.  The focus is on two events: (1) the stabilization of the neoclassical tearing mode with electron cyclotron current drive, and (2) a 3D hybrid simulation of the effect of an energetic ion component on the sawtooth for the complete cycle.  The sessions included a description of recent progress in these areas, an update of the theoretical framework for framing the interaction of heating systems with the MHD code, and a discussion of the computational issues related to code coupling and data exchange.

A one-day TRANSP/PTRANSP collaboration meeting was held at PPPL on December 6.  Participants included Drs. Irina Voitsekhovitch and Laurent Laborde (JET), Glenn Bateman, Alexei Pankin, and Federico Halpern (Lehigh University), and Robert Budny and Doug McCune (PPPL).  The meeting focused on simulation of JET experiments, and included several participant-led demonstrations of data preparation and visualization software on the PPPL Display Wall.

November 30, 2007

Theory Group

At the 12th Workshop on MHD Stability Control, held on November 18 -
20 at Columbia University, talks were given by Dr. A. Reiman
("Passive stabilization of the vertical mode in tokamaks by
parallelogram-shaped nonaxisymmetric coils") and by Dr. M. Chance
("Multi-mode analysis of RWM feedback with NMA code").
COMPUTATIONAL PLASMA PHYSICS GROUP (D. MCCUNE/S. JARDIN):

CPPG Group

Stephane Ethier gave an invited talk at the DOE/DOD Workshop on
Emerging High Performance Architectures and Applications held in
Washington on Nov 29-30. The title was "Computational Challenges in
Large-Scale Gyrokinetic Particle-in-Cell Simulations of Fusion
Plasmas.” The goal of the workshop was to discuss the challenges of
porting DOE and DOD-relevant applications to new architectures such
as the multi-threading Cray XMT and the IBM Cell-BE.

November 23, 2007

Theory Group

Costanza Zucca, a graduate student at CRPP-EPFL, Association EURATOM,
visited PPPL on November 19. Dr. T. S. Hahm was her host.. Costanza
gave a Theory Seminar entitled "Effects of local ECCD driven by the
optimized Equatorial and Upper EC Launchers on ITER." The present
ITER base-line design has the EC launchers providing only co-ECCD. A
variant of the EC system was recently proposed to enlarge the physics
programs covered by the Upper (UL) and Equatorial (EL) Launchers.
This study aims to provide the potential range of the q profile
control achievable by this optimization, including the possibility to
drive counter-ECCD and central ECH. Since the EL can only drive co-
ECCD, if ECH power is needed to assist the L-H transition during ramp-
up, it can have detrimental effects on the final profiles, such as
removing the reverse shear. Counter-ECCD offers greater control of
the plasma current density and provides, when balanced with co-ECCD,
pure ECH with no net driven current. The performance of the EL in
tailoring the q profile by adding co-/counter-ECCD was analyzed.
Effects of current drive and deposition width on sawtooth control by
UL were also discussed. The modeling was carried out with both
equilibrium and transport codes.

Sebastien Jolliet, a graduate student at CRPP-EPFL, Association
EURATOM, visited PPPL on November 19, which was also hosted by Dr. T.
S. Hahm. Sebastien gave a Theory Seminar entitled "Nonlinear global
gyrokinetic PIC simulations of collisionless TEM turbulence." Micro-
instabilities, such as Ion Temperature Gradient modes (ITG) and
Collisionless Trapped Electrons Modes (CTEM), are commonly held
responsible for anomalous transport observed in tokamaks. While there
have been a wide range of nonlinear studies on ITG turbulence, very
little is known about the nonlinear physics of CTEM. This work
presents the first linear and nonlinear simulations of ITG-CTEM
turbulence performed with the global PIC code ORB5. A linear
benchmark of ORB5 against other gyrokinetic codes was shown. The
implementation of a nonlinear CTEM model, where special care is put
on detrapped electrons, was presented. The simulations results
focused on nonlinear phenomena including detrapping, toroidal
coupling, zonal flows, profiles evolution and heat transport.

Gianlucca Spizzo from Consorzio RFX is visiting PPPL for three weeks
working with Roscoe White on nonlocal transport in the RFX.

CPPG Group

Stephane Ethier visited the Scientific Computing and Imaging (SCI)
Institute at the University of Utah in Salt Lake City (http://
www.sci.utah.edu/). This is part of an on-going collaboration with
visualization scientists of the SciDAC Visualization and Analytics
Center for Enabling Technologies (VACET) and aims at exploring
different methods to visualize the particles and fields in 5D
Gyrokinetic particle-in-cell simulations. Ethier also participated in
the SC'07 Supercomputing conference in Reno, NV.

Dr. Richard Gerber of NERSC presented a CPPG seminar on high
performance computing at NERSC. He presented an overview of the NERSC
computing environment, with an emphasis on the new CRAY XT4 machine
(FRANKLIN). Among the things discussed were compiling and running
jobs on Franklin, data backup systems, and data transfer to/from
NERSC including grid-based transfers.

November 16, 2007

Theory Group

Researchers from the Theory department contributed to 79
presentations at the 49th Annual Meeting of the APS Division of
Plasma Physics, November 12 - November 16 in Orlando, FL. There was
one review and two other invited talks. There were 22 contributed
first author papers and 54 co-authored papers.

CPPG Group

S. Jardin and D. McCune held satellite meetings in conjunction with
the APS-DPP meeting in Orlando Fl last week. Brief summaries of the
meetings are as follows:

For the fifth year in a row, a TRANSP Users' Group Meeting was held
as a satellite session at the APS-DPP conference. This year's
meeting was attended by 15 scientists with representation from PPPL,
MIT, General Atomics, Lehigh University, and JET (Culham, England).
Status and plans for TRANSP production and code development were
reviewed. There was considerable interest in TRANSP MPI-parallel
services (now available for production use) for computation of beam
and fusion product heating sources. A strong desire was expressed
for greater flexibility in the modeling of RF heating scenarios.
Attendees expressed appreciation for PPPL support of the Fusion Grid
TRANSP production system, which had a record year, over 4000 runs
produced in FY-2007.

The SciDAC Center for Extended Magnetohydrodynamic (MHD) Modelling
(CEMM) held an all day meeting on the Sunday preceding the APS-DPP
meeting as they have for every year since 2001. The meeting,
attended by about 30 physicists, was open to the public, but
concentrated on Extended MHD areas related to the new proposal
period, FY08-10. Topics included code development activities,
improved MHD closures, new analysis and test problems, and progress
on applications in the following areas: 2-fluid equilibrium,
sawtooth, disruptions, energetic particles, ELMs, RMPs. Copies of
the viewgraphs can be found on the "workshops" page on the site:
http://w3.pppl.gov/cemm.

November 9, 2007

Theory Group

Leonid Zakharov visited LANL, GA, UCLA and LLNL with a talk on "Lithium Wall Fusion and its 3 Step Program toward a Reactor Development Facility" (available at http://w3.pppl.gov/~zakharov) as a response to the Orbach/Bodman initiative for domestic fusion. In particular, the proposed program includes short term experiments on plasma pumping with a lithium loaded plate on NSTX and conversion of this machine into a spherical tokamak ST0 with a mission to demonstrate feasibility of the LiWall regime with 2-3 times better confinement than at present on NSTX.

Prof. Ronald C. Davidson and Dr. Hong Qin visited the Wilson Synchrotron Laboratory at Cornell University on the subject of collective dynamics of high intensity electron beams in the Energy Recovery Linac (ERL) that is currently being designed at Cornell. They presented a seminar titled "Kinetic theory and nonlinear perturbative particle simulation of high intensity charged particle beams", and discussed with Profs. Maury Tigner and Georg Hoffstaetter the possible deleterious two-stream interactions between the energetic beam electrons and the background ion species at Cornell's Energy Recovery Linac. Future collaboration with Cornell University on this subject will create opportunities for us to advance our understanding of this important physics phenomena characteristic of many high intensity beam systems.

Dr. G. Fu gave a Theory seminar entitled "Nonlinear Hybrid Simulations of Multiple Energetic Particle driven Alfven Modes in Toroidal Plasmas". Recent advances in self-consistent nonlinear simulations of fast beam ion-driven Alfven modes in NSTX and DIII-D using the extended MHD code M3D were reported. In the hybrid model, the thermal electrons and ions are treated as an ideal fluid while the energetic species is described by either drift-kinetic equation or gyrokinetic equation. The effects of energetic particles are coupled to the MHD equations via the stress tensor term in the momentum equation. The hybrid code has been recently applied to study nonlinear dynamics of fishbone instability. The code was also used to simulate nonlinear evolution of a single beam-driven TAE mode in NSTX. The result showed a weak frequency chirping about 20% consistent with experimental measurement. In this work, we use the M3D code to simulate beam ion driven Alfven modes in NSTX plasmas with multiple unstable Alfven modes. It is found that mode saturation level of each mode can be enhanced significantly by presence of other unstable modes indicating strong nonlinear interaction between different modes. It is also found that a linearly stable n=2 mode can be nonlinearly driven by an n=1 mode at significant mode amplitude. These results together with simulation results of beam ion-driven Alfven modes in DIII-D reversed shear plasmas were presented.

November 2, 2007

CPPG Group

The production version of TRANSP/PTRANSP has been upgraded to include an "equilibration feature."  When activated, this feature suspends re-calculation of (normally time dependent) neutral beam and RF heating after multiple slowing down times, declaring the sources equilibrated if the target plasma is sufficiently stationary and unchanging.  This option will improve the performance of predictive simulations with long stable flat tops; its applicability to ITER scenarios is being investigated.

Stephane Ethier and other members of the gyro-kinetic particle simulation group successfully achieved the FY07 JOULE Milestones set by the Office of Management and Budget (OMB) for the GTC-S particle code.  Every year for the past few years, OMB has been setting Milestones for 3 chosen large-scale scientific applications running on the OASCR-funded Cray XT4 system, Jaguar, located at the Oak Ridge National Laboratory.  This year's milestones called for a doubling in 
overall performance of the GTC-S application, which is a new version of the Gyrokinetic Toroidal Code that can treat globally consistent, shaped cross-section tokamaks by directly importing experimental profiles and equilibria. A new parallel algorithm implemented in GTC- S allowed it to easily surpass the milestones by dramatically increasing its concurrency and scalability.

Ravi Samtaney was invited by the Ultra-vis SciDAC Institute (PI: Prof. K-L Ma, UC Davis) to participate in a panel entitled 'Meet the Scientists' at the IEEE Visualization Conference in Sacramento, CA from October 28-November 1, 2007. He presented a talk in the panel discussing visualization and analysis needs faced by researchers performing simulations with block structured hierarchical adaptive mesh refinement methods.

Week of October 26, 2007

Theory Group

Dr. Harry Mynick gave an invited talk, "Zonal flows in 3D toroidal
systems" and Dr. Allan Reiman gave a talk "Stabilization of the
vertical Mode in Tokamaks by Localized Nonaxisymmetric Fields" at the
16th International Stellarator/Heliotron Workshop and 17th
International Toki Conference, in Toki, Japan (October 15-19, 2007).
Dr. R. E. Waltz from General Atomics visited PPPL on October 22-23.
Dr. G. Hammett hosted his visit. Dr. Waltz gave a joint Theory/NSTX
seminar entitled "Gyrokinetic Theory and Simulation of Momentum
Transport and Energy Exchange." A synopsis of physics results from
GYRO gyrokinetic simulations from the last five years was given with
a brief review. The focus however was on new theory and simulation of
the ExB shear and Coriolis angular momentum pinch effects needed to
understand the intrinsic toroidal rotation in tokamaks without
external torque in the core. In addition, new theory and simulations
showing that turbulent heating is dominantly an electron-ion energy
exchange was presented.

CPPG Group

Ravi Samtaney presented the CPPG seminar titled "Overcoming spatial
and temporal stiffness in MHD simulations for fusion applications."
He discussed two strategies: adaptive mesh refinement and fully
implicit Newton-Krylov and showed examples of MHD simulations of
interest to magnetic fusion.

Stephane Ethier gave a 2-part hands-on tutorial entitled
"Introduction to Parallel Programming with MPI" at Princeton
University as part of the Computer Science Department Program in
Integrative Information, Computer and Application Sciences (PICASso).
The course is limited to 30 attendees, mostly Princeton University
graduate students and researchers from several PU science
departments. The course filled up a few hours after the first
announcement. This shows the growing interest in parallel computing
in all scientific research fields on campus.

Week of October 19, 2007

Theory Group

Drs. Josh Breslau, Igor Kaganovich, Roman Kolesnikov and Wei-Li Lee
presented talks at the 20th International Conference on Numerical
Simulation of Plasmas in Austin, Texas.

Dr. Wei-Li Lee gave an invited/review talk, entitled "Self-Consistent
Profile Effects and Multiscale Integrated Gyrokinetic Particle
Simulation of Fusion Plasmas." The presentation included the new
findings that 1) profile relaxation in perturbative particle
simulation of microturbulence has negligible effects on steady state
transport, 2) the physics associated with the electron skin depth is
essential for high beta gyrokinetic particle simulations, and 3) the
electrostatic high frequency gyrokinetics can be studied with the
introduction of Kruskal rings. The use of the new global GTS code on
validation studies for NSTX plasmas, its recent performance
enhancement on MPP platforms and the prospect of using global
gyrokinetic particle codes for multiscale integrated simulations of
burning plasmas on petascale computers have also been discussed. The
collaborators of this work are R. Ganesh (IPR, India), E. Startsev,
R. Kolesnikov, H. Qin, S. Ethier, W. X. Wang and J. Manickam.

Dr. Joshua Breslau presented a talk on "An Improved Tokamak Sawtooth
Benchmark for Nonlinear Extended MHD."

Dr. Roman Kolesnikov presented an invited talk entitled,
"Electromagnetic high frequency gyrokinetic particle-in-cell
simulation." An electromagnetic version of an earlier developed
algorithm was presented. Comparisons with a Lorentz-force approach
were used to illustrate numerical advantages of the new algorithm.

Dr. Igor Kaganovich presented a talk titled: "Collective effects on
intense beam pulse neutralization by background plasma" Several
particle-in-cell codes were utilized for simulation of intense ion
beam pulses interacting with a background plasma. The results of
simulations were benchmarked against analytical theory. Necessary
requirements for correct simulations were discussed.

CPPG Group

D. McCune, L.P. Ku, S. Jardin and M. Chance attended the SciDAC SWIM
project meeting in ORNL. Project members presented progress reports
on the current physics thrusts (1) Simulation of current rampup in C-
Mod with ICRF and LHCD, (2) Evaluation of possibility of large
runaway electron formation due to knockons in the ITER discharge
startup, (3) Integrated simulation and stability analysis of a full
ITER discharge, and (4) modeling of the use of ECRH to stabilize
Neoclassical Tearing Modes in ITER. Computer science issues involved
the continued development of a modern framework that ties together
the different physics application codes (components) and allows them
a standard and convenient way to exchange necessary data through the
Plasma State component while using the massively parallel computing
resources in an optimal manner.

Week of October 12, 2007

Theory Group

Dr. T.S. Hahm presented an invited talk entitled "Recent progress in
the theory of turbulence-driven non-diffusive momentum transport" at
the JIFT Workshop on "Gyrokinetic Simulation of Plasma Transport:
Physics of Anomalous Fluxes of Momentum and Energy." This US-Japan
workshop was held on September 24 - 27, 2007, at the University of
Tokyo, Tokyo, Japan, and T.S. Hahm (PPPL), P.H. Diamond (UCSD) and
Hideo Sugama (National Institute for Fusion Studies, Japan) served as
workshop organizers. Dr. Hahm also presented a summary of two
sessions (internal transport barriers and rotation, theory and
simulation of transport barriers) as well as a poster on momentum
transport theory at the 11th IAEA Technical Meeting on H-mode and
Transport Barriers which was held on September 26 - 28, 2007, in
Tsukuba , Japan.

Professor John Krommes presented an invited talk at the international
scientific symposium "Plasma Theory, Wave Kinetics, and Nonlinear
Dynamics: KaufmanFest 2007," held in Berkeley on October 5-7 as "a
celebration of the insights, guidance, and contributions of Prof.
Allan Kaufman on the occasion of his 80th year." The title of his
presentation was "Nonlinear theoretical tools for fusion-related
microturbulence: Historical evolution, and recent applications to
zonal-flow dynamics."

Dr. Jay Johnson visited Dr. Marius Echim at the Institute for Space
Science in Bucharest, Romania, on October 1-12. He presented a
colloquium entitled "Outstanding science issues in space physics" at
the Faculty of Physics at the University of Bucharest, and is
collaborating on transport processes in Earth's plasma sheet and
modeling auroral acceleration.

Dr. Jay Johnson also presented an invited talk on "Insights into the
Nature and Morphology of the Substorm Process from Mapping Global
Features of Diffuse Aurora" at the STAMMS2 meeting on multi-point
measurements in space held in Orleans, France.

CPPG Group

We were notified by OFES this week that the SciDAC Center for
Extended Magnetohydrodynamics (CEMM) was successful in a re-
competition bid and will be renewed for a third three-year term at a
constant funding level. This PPPL-led Center consists of members
from 9 institutions. The focus of the Center is to apply advanced
computing techniques and resources to study and predict MHD phenomena
of importance to ITER: sawteeth, sawteeth in the presence of
energetic particles, excitation and control of neoclassical tearing
modes, resistive wall modes, disruptions, edge localized modes, error
field studies, and pellet fueling.

Due to the increased demand, 4 nodes (8 CPUs) have been added to the
PPPL Fusion Grid queue ("swift") that processes serial TRANSP
production run requests. The machines were provided by the PPPL
Computer Division.

Week of October 5, 2007

Theory Group

The DOE OFES Joule Theory Milestone for FY2007, which was led by the
PPPL Theory Department, was successfully completed. In FY2007 we
successfully improved the simulation resolution of linear stability
properties of Toroidal Alfven Eigenmodes driven by energetic
particles and neutral beams in ITER by increasing the number of
toroidal modes used to 15. In the course of the work, equilibria
representing the evolution of thirteen distinct plasma conditions
were developed and analyzed for TAE stability. The plasmas
represented three fiducial equilibria for the three main ITER
scenarios: the ELMy H-mode, hybrid and advanced (AT or reversed
shear) plasma regimes. The hybrid MHD/kinetic code NOVA-K was applied
to simulate the stabilty of TAE modes. We found the expected medium
to high-n range of TAEs unstable when the NBI was aimed slightly off
axis, 10-20cm vertically away from the midplane. The hybrid and AT
plasmas are the most unstable with the growth rates for the unstable
modes approaching 3-5%. H-mode plasmas show the least unstable case.
Complete stabilization of TAEs appears to be possible in both normal
shear and hybrid plasmas by aiming the NNBI exactly at the plasma
center or far away 50cm above/below the axis. In all cases studied,
the NBI ions strongly contributed to the instability and are
suggested for use for TAE stability control in ITER.

Dr. Allan Reiman hosted a National Stellarator Theory Teleconference
on September 27. Professor A. Ware of the University of Montana
presented a seminar entitled "Ballooning Modes in Quasi-symmetric
Stellarators". The effects on ballooning stability of two types of
symmetry breaking perturbations in HSX were studied. The addition of
a mirror term to the magnetic field was found to improve stability
properties, while a hill term negatively impacted stability. The
effects of the perturbations on local shear as well as on normal and
geodesic curvature were also examined.

CPPG Group

The Tokamak Simulation Code (TSC) has now been completely converted
to Fortran90, with all active versions merged, and put under source
code control using a SVN repository. The different versions that
were merged had special coding for ITER, DIIID, NSTX, CMOD and KSTAR.
The combined version can run TSC stand-alone, as before, or make
coupled run with TRANSP to utilize NUBEAM, or can be run as a SWIM
component in which it reads and writes to the plasma state using the
SWIM plasma state software. The source profiles (in AUXHEAT,
CURDRIVE), rotation profile (in TRCDEF) and electron density (in
REVAL) can be either the TSC internal analytic treatment, or from the
plasma state, or from tabulated data arrays in the external files
which may be tailored to simulations of a particular discharge. The
many additional switches in the new version are listed in a text file
"additional acoef" in the subdirectory "document". There is a README
file outlining the procedures for compile and load.

Fiscal Year 2007 saw a continued marked increase in PPPL Fusion Grid
TRANSP run production. The PPPL Fusion Grid services TRANSP run
requests from the US, Europe and Asia, with currently over 100 users
registered, carrying out simulation and analysis of tokamak
discharges from 9 current and future tokamaks: ITER, Asdex-Upgrade, C-
Mod, DIII-D, HL2A, JET, JT-60, MAST, and NSTX. FY-2007 total run
production on these tokamaks was 3843 runs (compared to 1401 in
FY-2005 and 2777 in FY-2006). Total CPU-hours in FY-2007 were 66,435
(compared to 11,135 in FY-2005 and 24,412 in FY-2006).

Week of September 28, 2007

Theory Group

On the request of the ITER team, the Equilibrium Spline Interface has
been complemented by Leonid Zakharov with routines calculating the
wetting zone and the halo currents from the plasma to the wall
surface during the vertical disruption event.

Propagation of an intense charged particle beam pulse through a
background plasma is a common problem in astrophysics and accelerator
applications. The plasma can effectively neutralize the charge and
current of the beam pulse, and thus provides a convenient medium for
beam transport. The application of a small solenoidal magnetic field
can drastically change the self-magnetic and self-electric fields of
the beam pulse, thus allowing effective control of the beam transport
through the background plasma. An analytical model has been
developed by Igor Kaganovich et al., to describe the self-magnetic
field of a finite-length ion beam pulse propagating in a cold
background plasma in a solenoidal magnetic field. Theory predicts
that there is a sizable enhancement of the self-electric and self-
magnetic fields due to the dynamo effect at certain values of applied
magnetic field. Furthermore, the combined ion beam - plasma system
acts as a paramagnetic medium, i.e., the solenoidal magnetic field
inside the beam pulse is enhanced.

CPPG Group

Doug McCune visited TRANSP User Groups at JET and MAST. There were
discussions of code status and plans for improvements, as well as
opportunities for JET and MAST team participation in TRANSP code
development. Both JET and MAST are very interested in emerging
TRANSP predictive capabilities (PTRANSP) and access to the TGLF
predictive transport model when this becomes available. The JET team
anticipates a strong focus on ICRF, and will work with PPPL to
improve RF modeling capabilities in TRANSP. The MAST team is
interested in exploring the possibility of incorporating edge
measurements and edge plasma modeling, to improve the realism of
treatment of edge effects and neutrals in the TRANSP analysis, while
taking advantage of the recent capability from PTRANSP to incorporate
free boundary equilibria in TRANSP simulations.

Stephane Ethier attended the Fall Creek Falls Conference "Key
Challenges in Computational Science at the Petascale," organized by
ORNL and held in Nashville, TN. Ethier presented work on
"Computational Challenges in Global Gyrokinetic Particle Simulations
of Strongly-Shaped Tokamaks".

Dr. Aleksandra Walczak (Princeton University) presented the CPPG
seminar on "From molecules to networks: the role of protein-DNA
binding kinetics in stochastic gene circuits". In the talk, he
discussed the development of relatively simple models and
approximations that help in the understanding of simple gene systems.

Week of September 21, 2007

Theory Group

A recently developed field line following code, SPLINT, written by
Stuart Hudson and Neil Pomphrey has been used to explore the efficacy
of a single circuit n=6 coil system for providing resonant magnetic
fields in NSTX, which ergodize the edge region. Ignoring plasma
shielding, less than 1kA-t of coil current effectively destroys
magnetic surfaces in the outer 10% of typical NSTX plasmas.
Preliminary results were included in Jon Menard's presentation at the
National Tokamak Planning Workshop.

CPPG Group

Stephane Ethier and Ravi Samtaney attended the annual face-to-face
NERSC Users' Group meeting in Oakland, CA, where NERSC is located.
The meeting consisted of a business day during which the users
learned about the status of NERSC's operations and projects, and of 3
training days on the newly deployed Cray XT4 computer. Dr. Samtaney
gave a user presentation entitled "Adaptive Mesh Simulations of
Pellet Injection into Tokamaks". He also gave the NAS Seminar
entitled "Overcoming Spatial and Temporal Stiffness in MHD
Simulations" at NASA Ames Research Center, Moffett Field CA on
September 18th 2007. All presentations are posted on the meeting's
web page at: http://www.nersc.gov/about/NUG/meeting_info/Sep07/

Week of September 14, 2007

CPPG Group

S. Jardin and D. McCune attended the "ITER Integrated Modeling
Workshop on Component Interfaces" at the Cadarache site, 10-14 Sept.
2007. This was the first Workshop on Integrated Modeling for ITER,
and was focused on technical issues that arise in establishing a
component approach to integrated modeling. The meeting was attended
by the leaders of each of the U.S. Integrated Modeling projects
(SWIM, FACETS, CPES, PTRANSP), several representatives from the
European Integrated Tokamak Modeling (ITM) project, and
representatives from the Japanese Burning Plasma Simulation
Initiative (BPSI) which includes both TASK and TOPICS. As a result
of the meeting, the groups agreed to develop and standardize a
unified set of interface data objects for use by ITER and the member
parties. The meeting was hosted by D. Campbell and W. Houlberg.
Copies of the presentations can be obtained from S. Jardin, and will
soon be available on the http://www.cswim.org/ web site.

Week of September 7, 2007

Theory Group

A paper titled “A new derivation of the plasma susceptibility tensor
for a hot magnetized plasma without infinite sums of products of
Bessel functions" by Hong Qin, Cynthia K. Phillips, and Ronald C.
Davidson has been published in Physics of Plasmas (Vol.14, No.9)
http://link.aip.org/link/?PHP/14/092103. The susceptibility tensor of
a hot, magnetized plasma is conventionally expressed in terms of
infinite sums of products of Bessel functions. For applications where
the particle's gyroradius is larger than the wavelength, such as
alpha particle dynamics interacting with lower-hybrid waves, and the
focusing of charged particle beams using a solenoidal field, the
infinite sums converge slowly. In this paper, a new derivation of the
plasma susceptibility tensor is presented which exploits a symmetry
in the particle's orbit to simplify the integration along the
unperturbed trajectories. As a consequence, the infinite sums
appearing in the conventional expression are replaced by definite
double integrals over one gyroperiod, and the cyclotron resonances of
all orders are captured by a single term. Furthermore, the double
integrals can be carried out and expressed in terms of Bessel
functions of complex order. From this new formulation, it is
straightforward to derive the asymptotic form of the full hot plasma
susceptibility tensor for a gyrotropic but otherwise arbitrary plasma
distribution in the large gyroradius limit. These results are of more
general importance in the numerical evaluation of the plasma
susceptibility tensor. Instead of using the infinite sums occurring
in the conventional expression, it is only necessary to evaluate the
Bessel functions once according to the new expression, which has
significant advantages, especially when the particle's gyroradius is
large and the conventional infinite sums converge slowly. Depending
on the size of the gyroradius, the computational saving enabled by
this representation can be several orders-of-magnitude.

CPPG Group

Doug McCune visited Dr. Holger St. John at General Atomics for the
PTRANSP collaboration. Development copies of TRANSP were
successfully installed and benchmarked on GA's 64 bit multi-core
"lohan" series workstations, thereby establishing the technical basis
for collaborative code development. Under the plans of the PTRANSP
project, GA will couple the GCNM-P stiff PDE integrator and the
emerging TGLF critical gradient transport model as an enhancement to
the predictive model capabilities of TRANSP. It is further planned
to use the Plasma State software developed under the SWIM SciDAC to
carry out communication between the GCNM-P package and the TRANSP
kernel.

Week of August 31, 2007

Theory Group

Prof. Bhimsen Shivamoggi from University of Central Florida visited PPPL on August 27-30. His visit was hosted by Dr. S. Jardin. On August 30th Prof. Shivamoggi presented a Theory Seminar entitled "Current-sheet Formation Near a Hyperbolic Magnetic Neutral Line in MHD". Current-sheet formation near a hyperbolic magnetic neutral line in MHD was investigated by including the effects of sweeping and shearing of the magnetic field lines by the plasma flow as well as density variation of the plasma. Exact solutions of the MHD equations appropriate for these situations were given. This problem was shown to possess a finite-time singularity for the incompressible plasma case and a whole new finite-time singularity for the variable-density plasma case. Theoretical results were compared with laboratory experiments.

CPPG Group

A command line interactive Fortran program called "cstate" has been developed for comparing the contents of a small number of plasma state files (or to examine the contents of a single state file). The program can read web-based states that are stored as URLs. After initial usage by the SWIM project, we plan to deploy cstate as a Fusion Grid Service, accessible via ElVis in a web browser. The cstate program allows detailed comparison of all aspects of the state: coordinate grid summaries, species lists and scalar data are displayed as tables; profiles and profile slices are shown in x-y "multiplots".

Week of August 24, 2007

Theory Group

T.S. Hahm attended the 3rd international summer school on plasma turbulence and transport: nonlinear wave-particle interactions in tokamak plasmas, and gave lectures on introduction to tokamak core turbulence, quasilinear theory of drift waves, and weak turbulence theory of drift waves. This year's summer school which was well attended by ~ 130 students from China, Korea, and Japan, was hosted by the South Western Institute of Physics and SiChuan University, and held on Aug 15-18 in Chengdu, China.

Alan Chin (Princeton University sophomore) worked this summer with Daren Stotler as a participant in DOE's SULI program.  As it did the previous summer, Alan's project involved the DG code, a graphical user interface program used to define computational grids input to tokamak scrape-off layer and edge plasma simulation codes.  Current applications of DG include B2-EIRENE simulations of the ITER divertor (Andre Kukushkin, ITER) and DEGAS 2 neutral transport simulations of NSTX experiments (Daren Stotler).  Alan's primary improvements to DG this year include a tool for specifying, viewing, and manipulating toroidally directed diagnostic chords and a new capability for stretching and rotating the view of the geometry.  The latter facility allows twisted grid cells to be identified and repaired.   His other extensions to DG and general knowledge of the code have enabled the generation of computational grids based on NSTX disconnected double null equilibria; this capability will be useful  for future DEGAS 2and UEDGE modeling of NSTX experiments.

Week of August 17, 2007

CPPG Group

A new release of the CPPG-developed web-based ElVis graphics software
has been announced. This latest release, documented in http://w3.pppl.gov/elvis, has new presentation styles for visualizing f(x,y)
data such as color-coded plasma cross-sections. These continuous
color plots can also be animated to show simulations evolving over
time, f(x,y,t), and can be monitored over the Internet. Interactive
zooming and scrolling has been added to logarithmic plots for
exploring data. User requests for higher resolution graphs, numerical
point editing, and flexible graph layout have been incorporated into
this version. Much of the development work for this release was
performed by Summer Student Interns Tarun Pondicherry and Ben
Phillips, sponsored by the PPPL Science Education Department and
mentored by Eliot Feibush. ElVis is presently being used in three
SciDac projects, several web services, and by many individual users.

Week of August 10, 2007

Theory Group

A paper entitled "High frequency gyrokinetic particle simulation" by
R. A. Kolesnikov, W. W. Lee, H. Qin and E. Startsev was published in
Physics of Plasmas 14, 072506 (2007). It addresses the gyrokinetic
approach for arbitrary frequency dynamics in magnetized plasmas,
using the gyrocenter-gauge kinetic theory. Contrary to low-frequency
gyrokinetics, which views each particle as a rigid charged ring,
arbitrary frequency response of a particle is described by a quickly
changing Kruskal ring. This approach allows separation of gyrocenter
and gyrophase responses and thus allows for, in many situations,
larger time steps for the gyrocenter push than for the gyrophase
push. The gyrophase response which determines the shape of Kruskal
rings can be described by a Fourier series in gyrophase for some
problems, thus allowing control over the cyclotron harmonics at which
the plasma responds. A computational algorithm for particle-in-cell
simulation based on this concept has been developed. An example of
the ion Bernstein wave is used to illustrate its numerical
properties, and comparison with a direct Lorentz-force approach is
presented.

Daren Stotler visited Oak Ridge National Laboratory to discuss future
atomic and plasma-material interaction physics research associated
with the Center for Plasma Edge Science (PI: C.S. Chang, NYU). The
end result of this work, done by CPES collaborators D. Schultz
(ORNL), M. Pindzola (Auburn U.) and co-workers, will provide an
update to the atomic and plasma-material data used by Stotler's DEGAS
2 neutral transport code. DEGAS 2's core routines are currently
being coupled into the CPES code, XGC.

An article describing the steady-state solution to a model of
advective-diffusive transport in chaotic fields by Dr. S. Hudson has
been accepted for publication in Physical Review E. This paper
studies transport in chaotic divergence-free flows, with rapid motion
parallel to the magnetic field and a small diffusive perpendicular
motion (characterized by a diffusion coefficient D). The strong
parallel motion leads many to the conclusion that chaotic magnetic
fields cannot support significant density gradients. This is
essentially correct near the "rational" regions, where the unstable
manifolds associated with the island chains provide rapid mixing.
However, for chaotic (but not uniformly ergodic fields), the
"irrational" regions present significant barriers to radial transport
even when no KAM surfaces exist. These barriers are provided by the
cantori, the remnants of the KAM surfaces. By constructing "chaotic
coordinates" based on a set of so-called ghost circles that
approximate the cantori, phase space is partitioned into regions of
rapid mixing and density flattening across the rationals, which are
separated by the irrational cantori where density gradients are
supported. This gives the density profile a smoothed Devil's
staircase structure, and this fractal structure is naturally revealed
by the chaotic coordinates. Just as the structure of chaotic fields
is universal, it is expected that the devil's staircase structure is
universal.

CPPG Group

K. Indireshkumar (Kumar) attended the SciDAC FACETS All Hands Meeting
at Tech-X Corporation in Boulder, Colorado. He gave a presentation on
parallelization, porting, and scaling studies of the PPPL Monte Carlo
Fast Ion code NUBEAM. He participated in discussions regarding
various FACETS components including NUBEAM, touching on issues of
compatibility with the FACETS framework.

Prof. Randall Bramley (Indiana University) visited PPPL for the week
to collaborate on the SWIM workscope, the ElVis-based visualization
tool in particular. He also presented a CPPG seminar on “The
Numerical Behavior of the Conjugate Gradient Algorithm” in which he
explained some non-obvious properties of the well-known algorithm
when applied to a variety of applications.

Week of August 3, 2007

Theory Group

A paper, "Stabilization of the Vertical Mode in Tokamaks by Localized
Nonaxisymmetric Fields," by Dr. A. Reiman, has been accepted for
publication by the journal Physical Review Letters. It has been
found that vertical instability of tokamak plasmas can be controlled
by nonaxisymmetric magnetic fields localized near the plasma edge at
the bottom and top of the torus. The required magnetic fields can be
produced by a relatively simple set of parallelogram-shaped coils.
By providing stable equilibria with more highly elongated cross-
sections, the addition of these nonaxisymmetric fields can
potentially lead to devices with improved confinement (empirically
derived global confinement scaling laws for tokamaks find that
confinement improves with increasing vertical elongation) and/or beta
limits (the Troyon scaling law for plasma stability predicts an
increase in the b limit for ballooning and kink modes with increasing
elongation). Furth-Hartman coils are calculated to have essentially
the same vertical stabilization effect as the simple parallelogram-
shaped coils, so that the vertical stabilization demonstrated
experimentally by Furth-Hartman coils supports the feasibility of
stabilizing vertical modes by the simpler coil set. The analytical
calculation assumes a large aspect ratio plasma that is well
approximated by a cylinder, b = 0, and a uniform equilibrium current
density. Stability is determined by a calculation, using the
stellarator approximation for both the equilibrium and stability
calculations.

Dr. Francesca M. Poli at CRPP-EPFL, Lausanne, Switzerland visited
PPPL on Aug 1-3 and presented a Science Focus Group Seminar on
turbulence measurements and analyses entitled "Electrostatic
instabilities and turbulence in a toroidal magnetized plasma." She
also had simulating discussions with many NSTX experimentalists and
theorists working on turbulence. Her visit was hosted by T.S. Hahm.

CPPG Group

S. Jardin attended a 4-day workshop on "Libraries and Algorithms for
Petascale Applications" sponsored by the DOE SciDAC Center for
Scalable Application Development Software. The workshop brought
together library and algorithm developers with representatives of
several different SciDAC Applications to identify future challenges
and needs. Jardin presented the leadoff talk on "Algorithmic needs
for Fusion MHD and other Predominantly Hyperbolic Systems of
Equations." As a result of interactions at the workshop, a very
promising scalable implicit solution technique has been identified
for the 3D nonlinear version of M3D-C1.

Week of July 27, 2007

Theory Group

Dr. T.S. Hahm attended the Festival de Theorie, sponsored by CEA
Cadarache, University Provence, and University Paul Cezane. held at
Aix-en-Provence, France, July 9-20. He presented an overview talk on
turbulence driven momentum transport, a tutorial talk on nonlinear
gyrokinetic description of tokamak core turbulence. He has also
participated in the gyrokinetic code validation discussion involving
GTC, GYSELA, ORB5 and GT3D.

Several theorists participated in the NSTX Results and Theory
Review. The following presentations were made: E. Belova on
“Nonlinear simulations of NBI driven GAE modes in NSTX”; G. Fu
on “Update on M3D hybrid simulations of beam-driven modes in
NSTX”; N. Gorelenkov on “Beta induced Alfven-Acoustic modes in
NSTX”; and L. Zakharov on “Lithium loaded target plate for high
performance plasma in NSTX.”

CPPG Group

Dr. Yudong Pan completed her 3-month stay at PPPL this week and
returned to the Southwestern Institute of Plasma Physics in China.
While at PPPL, she learned to use all features of the Tokamak
Simulation Code (TSC) and applied this to the design of an upgrade of
the HL-2A tokamak, which is to be called HL-2M. The simulations
covered both double and lower single null operation, and both ohmic
and auxiliary heated discharges. The vertical stability requirements
were also studied. The results of this study have been summarized in
the report Y. Pan, S. Jardin, and C. Kessel, "The Discharge Design of
HL-2M with TSC;" PPPL-4257 (2007): which will soon be available online.

Week of July 20, 2007

Theory Group

Dr. Ernest J. Valeo submitted a paper to Physics of Plasma titled "Full-Wave Simulations if ICRF heating in toroidal plasma with non-Maxwellian distribution functions in the FLR limit" co-authors are Phillips and Okuda from PPPL, Wright and Bonoli from MIT and Berry from ORNL.

CPPG Group

The SciDAC SWIM Project "Virtual Coding Camp" continued this week and PPPL made several critical contributions: 1. A new version of the "Plasma State" software was released that supports, among other things, a "partial copy" of a state object.  This capability is needed, for example, when one of the SWIM components (such as the RF component) changes grid size or resolution during a time-dependent run, or when one component is in "replay mode" and the output from that component is selectively copied from a previous run.  2. The "Linear Stability" component has been completed and put into production use.  This component reads the equilibrium and profile information from the plasma state, refines the equilibrium if necessary, performs a flux-coordinate mapping, evaluates the high and low toroidal mode number stability, and writes the stability results back into the plasma state.  3. A CMOD current ramput test case has been developed (in addition to the ITER test case).  In the CMOD test case, the RF heating starts at t=0.75 sec of the 2.0 current ramp.  These cases are now available to be either re-run with different RF components for parameter studies, or to use in the replay mode to aid in debugging and developing the other components.  The cases now include full stability analysis using the new Linear Stability component.

Week of July 13, 2007

Theory Group

Dr. Eun-Hwa Kim published a paper entitled, "Extraordinary-mode
radiation produced by linear-mode conversion of Langmuir waves" by
Eun-Hwa Kim, Iver H. Cairns, and Peter A. Robinson in Physics Review
Letters, Vol. 99, 015003 (2007).

Dr. Jay Johnson attended the 2007 International Union of Geodesy and
Geophysics Conference in Perugia, Italy, where he presented talks on
Enhanced Aurora, Transport at the Magnetopause, and Nonlinearity in
Magnetospheric Dynamics.

CPPG Group

PPPL participated in a SciDAC SWIM Project “Virtual Coding Camp” this
week, which consisted of a number of project conference calls and
emails to accomplish the project objectives set out for the week. As
part of the PPPL workscope, we produced a new component for the SWIM
framework called the “Equilibrium and Profile Advance Replay” or EPA-
Replay. This new component looks to the outside world like the EPA
component, but does not perform any calculations. Instead, it reads
Plasma State files from a previous calculation and writes the data
that the EPS normally writes into the new Plasma State for the new
calculation. This EPA-Replay component is already proving very
useful in the debugging of the other components that depend on the
EPS, in performing comparative studies for determining resolution
requirements in the other components, and for porting the other
components to new computing platforms.

Week of July 6, 2007

Theory Group

Dr. Nikolai Gorelenkov gave an invited talk at the EPS in Warsaw Poland titled "Predictions and observations of Beta-induced Alfven-acoustic Eigenmodes in JET and NSTX". The talk showed the results on theoretical predictions and experimental observations on JET and NSTX, of a new class of low frequency global-mode instabilities, which have been observed. These modes called Beta - induced Alfven - acoustic eigenmodes (or BAAE) are driven by energetic ions and are the results of the coupling of two fundamental MHD branches, acoustic and Alfvenic. Both qualitative and quantitative agreement with theory was reported.

Dr. R. Ganesh, a visiting researcher from the Indian, Institute for Plasma Research, started a three-month stay at PPPL, on July 2, 2007. He will be collaborating on studies related to turbulent transport.

CPPG Group

There has been a substantial increase in the rate of TRANSP run production on PPPL Fusion Grid servers. From June 1, 2006 to May 31, 2007, the Fusion Grid recorded 3566 runs using 48,630 server cpu-hours, compared to 1899 runs using 12,149 cpu hours over the same date range in the preceding year. All of the following tokamaks showed increased utilization: Asdex-U, C-Mod, DIII-D, JET, MAST, NSTX, as well as predictive simulations of ITER.

S. Jardin attended the EPS Conference on Plasma Physics in Warsaw, Poland and presented a paper on "Two-fluid extended-MHD calculations of toroidal equilibrium and collisionless reconnection in magnetized plasmas". The paper presented 2 new results obtained with the new M3D-C1 code [PPPL-4209, to appear in J. Comp. Phys. (2007)]. The first had to do with the role of the toroidal (guide) magnetic field on delaying the onset of fast magnet reconnection. The second had to do with the accurate calculation of self-consistent flows, rotations, and associated GAM oscillations in free-boundary diverted toroidal equilibrium.

Week of June 29, 2007

Theory Group

A paper based on the collaboration between PPPL and the W7AS stellarator group in Germany has been accepted for publication in the journal Nuclear Fusion, to appear as Nucl. Fusion 47 (2007) 572-578. It is presently available online at http://stacks.iop.org/ 0029-5515/47/572 Entitled "Pressure-induced breaking of equilibrium flux surfaces in the W7AS stellarator," the authors are A. Reiman, M. Zarnstorff, D. Monticello, A. Weller, J. Geiger and the W7-AS Team.

Jay Johnson and Eun-Hwa Kim attended the Geospace Environment Modeling meeting in Midway, Utah. Jay Johnson presented a discussion of entropy differences in the plasma sheet of the magnetosphere, comparing the statistics of plasma sheet properties appropriate for the growth and expansion phases of substorms. There is a significance decrease in the entropy per unit flux (proportional to mass content) earthward of 20 Earth radii, but little change in the specific entropy in the transition between growth and expansion phase. The result suggests that significant mass/volume is lost from field lines in the transition without significant nonadiabatic processes. This result is consistent with the loss of entropy due to the ejection of a plasmoid in the magnetotail.

The paper "Zonal Flows in Toroidal Systems," by Dr. Harry Mynick and Prof. Allen Boozer (Columbia U) has been accepted for publication in the Physics of Plasmas.

CPPG Group

The 3rd Quarter FY07 Nonlinear MHD Milestone progress report was submitted to DOE this week, summarizing progress in the 4 milestone areas: (1) Improve understanding of the present discrepancy between NIMROD and M3D and move to new CDX-U-relevant cases with more realistic parameters and sources. (2) Perform a linear edge stability calculation in a non-diverted equilibrium with a resistive code, and compare results with the linear ideal MHD code ELITE. (3) Extend the 2D GEM nonlinear benchmark to non-zero guide field and more extreme parameters. (4) Perform scalability studies on leading edge computers. A copy of this quarterly report can be found at: http://w3.pppl.gov/cemm/Milestones/Milestones_2007_Q3.pdf

Week of June 22, 2007

Theory Group

Dr. Bruce Scott, Max-Planck-Institute for Plasma Physics (Germany), gave a talk entitled, Gyrofluid Computation of Electromagnetic Core Turbulence on June 21, 2007.The abstract of his talk follows. Computations using the six-moment GEM code are given for turbulence at tokamak core parameters, including the correct electron/deuterium mass ratio. The Cyclone parameters are used as a base, and beta and the mass ratio are swept. Diagnostics showing proper function of the electron parallel dynamics are given. Finite beta is strongly stabilizing, such that the low value of the experimentally observed transport may be understood as just below the onset of kinetic ballooning. The effect of kinetic electrons does depend on the mass ratio M_i/m_e. A value of 3670 (deuterium) leads to complete ITG stabilization with finite transport due to electron microtearing. A value of 1/2 or 1/4 this leads to complete stabilization with no microtearing. A value of 300 leads to periodic bursting with narrow ITG streamers. A value of 100 leads to a result much like edge turbulence. Nominally, the radial/drift direction resolution ratio is 4, resolving all rational surfaces including the shortest wavelength ones. Reducing this ratio to 2 again produces unstable ITG streamers since the electrons do not sufficiently experience the effects of magnetic shear. Reducing the ratio to 1 produces unstable kinetic ballooning. Diagnostic support for all of the above is shown. The implication is that the correct mass ratio should be used, and all rational surfaces should be resolved, in order that computations of electromagnetic core turbulence be physically viable.

Dr. A. Reiman presented a seminar entitled "Pressure-induced Breaking of Equilibrium Flux Surfaces in the W7AS Stellarator" for the National Stellarator Theory Teleconference on June 21. Calculations were presented for two shots in the W7AS stellarator, which differed only in the magnitude of the current in the divertor control coil, but had very different values of experimentally attainable beta (beta = 2.7% vs. beta = 1.8%). Equilibrium calculations find that a region of chaotic magnetic field line trajectories fills approximately the outer 1/3 of the cross section in each of these configurations. The calculated magnetic field line diffusion coefficients in the stochastic regions for the two shots are consistent with the observed differences in the attainable b, and are also consistent with the differences in the reconstructed pressure profiles. This work was done in collaboration with Drs. M. Zarnstorff and D. Monticello at Princeton, and Drs. A. Weller and J. Geiger and the W7AS Team at Greifswald, Germany.

Dr. Leonid E. Zakharov attended the 12th Russian Conference on High Temperature Plasma Diagnostics, which was focused around ITER needs. He gave a talk on "Equilibrium reconstruction of q- and p-profiles in ITER using different external and internal measurements." At the request of the conference organizers, he presented a special talk on a new concept of a magnetic fusion reactor entitled, "Fusion with and without alpha particle heating." He also visited JET and gave two talks, one on "NBI fueling and stability of low recycling plasma" to motivate experiments on JET on ELM stabilization, and an EFDA-JET Seminar on, "A three step program toward a Reactor Development Facility (RDF)."

CPPG Group

J. Chen, together with M. Chance (theory), D. McCune, and L.P. Ku (EAD) have successfully created and tested a Python-based Linear MHD Stability Component for the SWIM project. The Stability Component reads all equilibrium and profile data from the SWIM Plasma State. It then invokes the JSOLVER inverse equilibrium code to recompute the equilibrium to a higher tolerance, keeping the boundary shape and plasma pressure and parallel-current profiles fixed. This high- resolution equilibrium is then passed through a separate mapping code, and the result of this is analyzed by the stability code. The stability results are then transferred back to the plasma state. The initial implementation of this calculates the stability using the high-n BALLOON code, but an option for the PEST-2 code will be added shortly.

R. Samtaney and K. Indireshkumar (Kumar) represented PPPL at the Computational Science Graduate Fellowship (CSGF) Conference in Washington DC on June 19-20. They presented a poster highlighting the computational plasma physics research at PPPL. One of the objectives of their attendance was to attract CSGF fellows to spend a summer at PPPL working with a staff member on a computational project.

Week of June 15, 2007

Theory Group

Dr. Oleg Polomarov from UT Austin visited PPPL and gave talk entitled "Robust approach for description of auto-resonance and bi-stability methods of adiabatic excitation of non-linear oscillations in plasma physics and quantum-mechanics" on June 15, 2007. The abstract of his talk is: Methods of adiabatic excitation of large-amplitude oscillations in resonantly driven dynamical systems are generic to a variety of plasma physics problems. A robust approach for description of the bi-stability, auto-resonance, and their possible combination has been developed and applied for the plasma beat-wave accelerator. The analogs of the auto-resonance and bi-stability in quantum- mechanical systems are considered.

Week of June 8, 2007

Theory Group

Dr. J.D. Callen, University of Wisconsin gave a Theory seminar on
June 6, 2007. His talk was entitled, "Derivation of paleoclassical
key hypothesis." The abstract of his talk is: The paleoclassical
model of radial electron heat transport in resistive, current-
carrying toroidal plasmas is based on a key hypothesis—that electron
guiding centers move and diffuse with radially localized annuli of
poloidal magnetic flux. This hypothesis is shown to result from
transforming the drift-kinetic-equation to poloidal flux coordinates
in situations where this flux is governed by a diffusion equation and
analyzing the mathematical characteristic curves (guiding center
trajectories) of the resultant drift-kinetic equation on the magnetic
field diffusion time scale tau_eta = a^2 D_eta. These effects add a
tau_eta time-scale, Fokker-Planck-type spatial diffusion operator to
the drift-kinetic equation.

CPPG Group

Four dual core AMD Opteron Linux servers (8 processors) have been
added to the "swift" queue, a pool of dedicated servers for Fusion
Grid serial TRANSP production runs at PPPL. TRANSP (NUBEAM)
benchmarks show that these servers, swift05--swift08, are 30% faster
than the older machines swift02--swift04 (6 processors) which remain
in service. The new machines boost PPPL's dedicated Fusion Grid
TRANSP production capacity by a factor of 2.7. If these machines are
booked, TRANSP jobs can also execute in a shared PPPL serial process
queue (sque) when slots are available.

Jin Chen attended the International Conference on Computational
Science 2007 (ICCS 2007) in China along with about 500 other
participants from 54 countries. She presented a paper "Variable
relaxation solve for nonlinear thermal conduction".

Dr. Mark Adams (Columbia/PPPL) presented the CPPG seminar on "New
Advances in the Gyrokinetic Toroidal Code and Their Impact on
Performance on the Cray XT Series." He described recent improvements
to GTC involving a second domain decomposition, and how this affects
weak parallel scaling results.

Week of June 1, 2007

Theory Group

Dr. Leonid Zakharov gave a talk to the NSTX Group (May 29, 2007) on
"Operational and design space of Liquid Lithium Divertor." The NBI
power/duration diagrams were presented for different liquid lithium,
capillary porous systems (CPS) on different substrates and for a
variety of thermal and power deposition regimes from the scrape-off-
layer. It was concluded that the liquid lithium on the top of the
stainless steel/copper sandwich, recommended for installation for the
next year's experimental campaign, can provide the necessary
operational space for high performance regimes in NSTX.

Dr. Oleksiy Mishchenko from Max-Planck Institut fuer Plasmaphysik,
Greifswald, Germany visited PPPL from May 21 to June 1. During his
productive visit hosted by T.S. Hahm, he interacted with several
experts on nonlinear gyrokinetic theory and simulations. In
particular, he discussed recent progress in Electromagnetic PIC delta-
f simulations pursued by the Greifswald group with GTC team members.
Currently, they run a linear 2D version, their primary interest is to
study pure electromagnetic modes, such as KBM or kinetic MHD. He
also gave a theory seminar on a many-body formulation of the
nonlinear gyrokinetic theory on May 31, which was well received. He
has shown that a collision integral can be derived using the Lie
perturbation method and BBGKY hierarchy. His result is similar to
Rostoker's integral (1960) in the limit of a straight magnetic field.
He is applying his general geometry version of turbulent
equipartition (TEP) particle pinch theory to an NSTX case with help
from S. Kaye.

Week of May 25, 2007

Theory Group

A paper entitled "Nonlocal properties of gyrokinetic turbulence and
role of ExB flow shear" by W. X. Wang, T. S. Hahm, W. W. Lee, G.
Rewoldt, J. Manickam and W. M. Tang has been accepted for publication
in Physics of Plasmas.

Dr. Bruce Scott, Max Planck Institute, Garching, Germany arrived for
a six-week visit to PPPL. He will collaborate with the core and edge
turbulent transport groups.

Eun-Hwa Kim attended the 2007 Joint Assembly of the American
Geophysical Union in Acapulco and presented talks on, "Modeling
Feedback Between Ion Outflows and Electromagnetic Alfven Ion
Cyclotron Waves;" "Generation and propagation of Pc1-2 waves in the
magnetosphere: Effects of heavy ions;" and "Simulation study of EM
radiation from Langmuir/z waves in warm magnetized plasmas."

CPPG Group

The PPPL TRANSP Monte Carlo code, NUBEAM, has been enhanced to enable
capture of detailed information on pitch, energy, and spatial
variation of the birth distribution of neutral beam and fusion
product fast ions. New TRANSP runs can now capture this information
for use by the legacy tool "get_fbm" which is included in the PPPL
NTCC software distribution. Using get_fbm, guiding center sample
files from either the birth distribution (new) or the slowing down
distribution (as before) can be generated. Such data can be used as
input to first principles fast ion codes with 3d field effects, such
as ORBIT. This improvement is also a step in the direction of being
able to provide input from NUBEAM deposition calculations to a Fokker
Planck slowing down calculation such as CQL3D.

Week of May 18, 2007

Theory Group

The Theory Department had its monthly meeting on May 17, 2007.
Informational micro-seminars were presented by Dr. G. Rewoldt on,
"Progress in Applications of the GEM code to NSTX;" and Dr. N.
Gorelenkov on, "Alfven acoustic eigenmodes below GAM frequency and
their observations."

Dr. R. White submitted a paper entitled, "The use of Kruskal-Newton
diagrams for differential equations" by T. Fischalek and R. White to
the Journal of Mathematical Physics.

CPPG Group

S. Jardin, D. McCune, and R. Samtaney, along with G. Fu and W. Lee
(Theory), C.K. Phillips (NSTX) and M. Zarnstorff (NCSX) attended a 2-
day Fusion Simulation Project Workshop in Rockville, MD. Keynote
addresses at the workshop were made by Michael Strayer (OASCR) and
Ray Fonk (OFES). The workshop was organized around four panels on
Project management & Structure, Physics Components, Code integration,
and Computer Science and Applied Math. The panels met separately to
refine reports they had been working on for the past several months,
and participated in joint plenary sessions where the work of each
panel was discussed and feedback from the other panels was received.
The output of the workshop is a ~40 page report that makes the case
for initiating a new joint OFES/OASCR budget item: The Fusion
Simulation Project. The funding plan calls for the start of about
$2M in new money in FY09 for some initial planning and design
activity, and for the funding rampup to continue to a total of about
$20M/year in new money by FY 2013. The goal is to produce the
world's best magnetic fusion simulation capability where advanced
simulation software and petascale computing
capabilities could be applied to simulation and analysis of ITER-
class and beyond burning plasma devices.

Week of May 11, 2007

Theory Group

Drs. Gorelenkov et al., submitted a paper entitled, "Predictions and
observations of low-shear beta-induced Alfven-acoustic Eigenmodes in
toroidal plasmas," to Physics Letters A. The article will be
available as a PPPL Report.

Drs. Fu et al., submitted a paper entitled, "Ideal
Magnetohydrodynamic Stability of the National Compact Stellarator
Experiment," to Fusion Science and Technology.

Dr. J. Manickam participated in a Gender Equity Workshop, co-
sponsored by the APS, DOE and NSF. The goal of this workshop is to
double the number of women in physics in the next 15 years by
informing, educating and providing chairs of physics departments and
physics-oriented national laboratory managers the tools to achieve
that goal. The presentations are available at
http://www.aps.org/programs/women/workshops/gender-equity.cfm

CPPG Group

Prof. Yudong Pan from the Computer and Control Division of the
Southwest Institute of Physics (Chengdu, Sichuan, China) arrived at
PPPL for a 3-month visit. Dr. Pan will be learning and modifying the
Tokamak Simulation Code (TSC) and applying it to model discharges in
NSTX. She will also begin using TSC for design studies of a
modification of the HL-2A tokamak at SWIP that will be called HL-2M.

Week of May 4, 2007

Theory Group

Ravi Samtaney and Daren Stotler attended the spring meeting of the Center for Plasma Edge Simulation (CPES) in Las Vegas on April 30 and May 1.  Samtaney gave a talk on the coupling of the XGC edge plasma turbulence code to the M3D nonlinear MHD code and discussed the applied mathematics issues associated with coupling kinetic-MHD codes.  Stotler provided a progress report on his efforts to replace the neutral particle transport routines in XGC with ones based on the DEGAS 2 Monte Carlo neutral transport code.  In addition, Eliot Feibush's work on the ElVis visualization system was presented by a colleague from Rutgers University.

Week of April 27, 2007

Theory Group

Dr. W. X.  Wang gave a seminar on April 26, 2007. The title of his talk was, “Gyrokinetic Simulation Studies of Plasma Transport in NSTX Experiments.”  Global gyrokinetic simulations have been carried out to investigate both turbulent and neoclassical transport properties for experiments of axisysmmetric devices. These studies support the experimental observation that the ion transport is at the neoclassical level in the National Spherical Torus Experiment (NSTX).  Nonlinear turbulence simulations using the GTC-S code have shown that ion temperature gradient (ITG) driven turbulence has significant fluctuation amplitude, but drives insignificant ion energy transport in NSTX (about the neoclassical level, sometimes even below it). This distinguished feature is in contrast to anomalous transport in other 
machines, such as DIIID, where ITG turbulence is shown to drive large transport (10 x neoclassical level), even though the mean turbulence fluctuation level for the two discharges are actually comparable. It 
is also found that self-consistent neoclassical equilibrium EXB flows, as calculated by GTC-Neo, also a global PIC code, can strongly stabilize ITG modes. Ion-ion collisions are shown to enhance ITG 
driven thermal transport, but not significantly. Also reported are simulations of toroidal momentum transport and anisotropic property of neoclassical equilibrium as well as the recent progress in GTC-S 
toward application to high-k fluctuations and the electron transport of NSTX discharges.

On April 27, Dr. Guilhem Dif-Pradalier,  of Association Euratom-CEA, Cadarache, France gave a Theory Seminar entitled, “Gyrokinetic Equilibrium and Self generated Flows.”

Daren Stotler presented a talk entitled “A Step Closer to a Validation Exercise” at the 2007 Transport Task Force Meeting in San Diego last week.  The presentation discussed validation metrics in 
general and described the evaluation of two specific metrics.

On April 18, Leonid Zakharov presented a poster on “Equilibrium Spline Interface (ESI) for magnetic confinement codes” to the TTF workshop in San Diego.  On April 20, he gave a talk to the Science 
Meeting in General Atomic on “Consideration of variances in equilibrium reconstruction.”

PPPL scientists were first or co-authors of 25 poster presentations at the 2007 International Sherwood Fusion Theory Conference in Annapolis, MD. The contributors were:  Belova, Breslau, Chance, 
Davidson, Ethier, Ferraro, Fu, Gerhardt, Gorelenkov, Hahm. Hammett, Jardin, Kaye, Kessel, Kolesnikov, Ku, Krommes, Lee, Lukin, Manickam,  McCune, Menard, Monticello, Mynick, Okabayashi, Park, Rayburn, Reiman, Reiman, Qin, Rewoldt, Samtaney, Startsev, Stoltzfus-Dueck, Tang, Takahashi, Wang, White, Yamada, Zakharov and Zweben.

CPPG Group

A major milestone has been met in the PPPL portion of the SciDAC SWIM project.  The PPPL developed EPA component (Equilibrium and Profile Advance) has now been fully coupled to the SWIM Computational Framework in a compliant manner.  As an initial demonstration, it has progressed through several macro-timesteps.  During the first call, it initializes the simulation state by calculating an initial equilibrium.  On the subsequent calls, it time advances the equilibrium and the associated profiles for a specified time period.   This capability now makes it fully coupled to the other component modules that are part of the SWIM system.

The NTCC interpolation library PSPLINE has been upgraded to support “hybrid” interpolation.  Interpolation methods for gridded numerical data of up to three dimensions can now be mixed, allowing specification of cubic spline interpolation along some dimensions and piecewise linear and/or simple zonal lookup along other dimensions.   The XPLASMA software has been upgraded to permit definition of profiles with hybrid interpolation, which are planned to accommodate new outputs of the NUBEAM fast ion model.

R. Samtaney  and S. C. Jardin attended the CEMM project meeting and 2007 Sherwood  Conference in which they presented papers on “Motion of a Localized High Density Region across Magnetic Flux Surfaces” and “Two-fluid MHD Calculations of Collisionless Reconnection in Magnetized Plasmas with a Strong Guide Field.”

Week of April 20, 2007

Theory Group

Dr. H. Mynick presented a seminar on April 19 for a National Stellarator Theory Teleconference hosted by Dr. A. Reiman.  The seminar described an analytic study of the shielding and time 
evolution of zonal flows in tokamaks and stellarators using the action-angle formalism.  The work has been done by Dr. Mynick in collaboration with Professor A. Boozer of Columbia University.

Drs. Hantao Ji and Greg Hammett gave invited talks at the APS April meeting in a session on "Momentum Transport in Astrophysical and Fusion Plasmas".  Ji discussed recent experiments at PPPL in his talk "Laboratory Studies of Angular Momentum Transport in Astrophysically Relevant Flows."   Hammett followed with a talk on behalf of U.C. Berkeley collaborator Eliot Quataert, on "Angular Momentum Transport  in Astrophysical Accretion Flows."

Hammett also gave an invited talk in a session on fusion plasmas, on "Progress in 5-Dimensional Plasma Turbulence Simulations in Fusion Energy Devices."  He represented fusion research for an APS-organized "Lunch with Experts," which provided an opportunity for undergraduate and graduate students to talk with scientists from various areas of physics.

CPPG Group

Stephane Ethier ran the standard weak scaling benchmark for the Gyrokinetic code GTC on the recently upgraded 119-Teraflops Cray XT system, Jaguar, at the National Center for Computational Sciences  (NCCS) at ORNL. GTC achieved a new record in scalability and performance, reaching nearly 20 Teraflops on 22,976 compute cores and advancing 11.6 billion particles one step per second. The total number of particles used in the benchmark was an unprecedented 74 billion.

Week of April 13, 2007

Theory Group

The Theory Department had its monthly group meeting on April 12, 2007. The informational micro-seminars speakers and their titles were: Neil Pomphrey on “Various stuff, mainly using spherical harmonics” and Don Monticello on “Calculations of helically symmetric equilibria with PIES.”

The following paper, “Non-local properties of gyrokinetic turbulence and role of EXB flow shear” by W. X. Wang, T. S. Hahm, W. W. Lee, G. Rewoldt, J. Manickam, and W. M. Tang, has been submitted Physics of Plasmas. The non-local physics associated with turbulent transport is investigated using global gyrokinetic simulations with realistic parameters in shaped tokamak plasmas.  The studies focus on the turbulence spreading through a ransport barrier characterized by an equilibrium EXB shear layer. It is found that an EXB shear layer with an experimentally relevant level of the shearing rate can significantly reduce, and sometimes even block, turbulence spreading by reducing the spreading extent and speed. This feature represents a new aspect of transport barrier dynamics. The key quantity in this process is identified as the local maximum shearing rate, rather than the amplitude of the radial electric field. The simulation studies also extend to radially local physics with respect to the saturation of the ion temperature gradient (ITG) instability, and show that the nonlinear toroidal couplings are the dominant k-space activity in the ITG dynamics, which cause energy transfer to longer wavelength damped modes, forming a down-shifted toroidal spectrum in the fully developed turbulence regime.

Week of April 6, 2007

Theory Group

Dr. H. Mynick, in collaboration with Professor A. Boozer from Columbia University, has submitted a paper entitled "Zonal Flows in Toroidal Systems" to Physics of Plasmas.   An analytic study of the shielding and time evolution of zonal flows in tokamaks and stellarators is presented, using the action-angle formalism. This framework permits one to solve the kinetic equation without expansion of that equation in small parameters of radial excursions and timescale, resulting in more general expressions for the dielectric shielding, and with a scaling modified from that in earlier work. From these expressions, it is found that for each mechanism of collisional transport, there is a corresponding shielding mechanism, of closely related form and scaling. The effect of these generalized expressions on the evolution and size of zonal flows, and their implications for stellarator design are considered. The paper is available as a PPPL Report, PPPL-4228.

A review article entitled ""Foundations of nonlinear gyrokinetic theory," and co-authored by A.J. Brizard at St. Michael's College and T.S. Hahm at PPPL, has been published in the April-June 2007 issue of Reviews of Modern Physics (Vol.79, No.2) 421-468.

CPPG Group

Stephane Ethier attended the 21st International Parallel and Distributed Processing Symposium (IPDPS) in Long Beach, CA, where he received the “Best Paper Award” as a co-author on the paper entitled "Scientific Application Performance on Candidate Petascale Platforms". This work was done in collaboration with Dr. Leonid Oliker of the Future Technologies Group at LBL in Berkeley, CA. Dr. Ethier also visited Prof. Zhihong Lin at the University of California, Irvine, and gave a presentation entitled "Extreme Parallel Computing: Running the Gyrokinetic Toroidal Code on 32,768 processors".

The Plasma State specifications and software for the SciDAC SWIM project has been updated.  Variables were added to track the results of linear MHD stability calculations, and to support a simulation of the possible generation of runaway fast electrons during start up, pellet injection events, or disruption of a tokamak discharge.  The Plasma State defines a communications framework which enables transfer of physics results between independently developed components for integrated simulation purposes.  The package is generated from a specification file using a Python code generator, enabling reliable and accurate modifications to the definition of state contents while supporting a range of services for I/O and interpolation.

Week of March 30, 2007

Theory Group

Prof. Dong-Hun Lee from the Department of Astronomy and Space
Science, Kyung Hee University, Yongin, Korea gave a theory seminar
entitled “Invariant imbedding theory of mode conversion in MHD and
plasma waves.” He presented a recent study of mode conversion, whichoccurs among the various wave modes in inhomogeneous plasmas. The mode conversion in plasma waves is associated with resonances, which often appear as singularities in the wave equation. A new approach called the IIM (invariant imbedding method) has been suggested which allows solving the wave equations correctly and accurately without any theoretical approximations, which becomes important when the approximations such as WKB or Bremmer series are invalid at the cutoff or singular regions. The process of mode conversion for each resonance in MHD and multi-fluid plasma waves has also been investigated. Prof. Lee is on a yearlong visit to PPPL.

CPPG Group

Dr. Alexander Pletzer of TechX Corporation visited PPPL for 10 days
to collaborate with TRANSP developers on the FACETS project. During
his stay, the TRANSP code and the Monte Carlo NUBEAM (NTCC module) were successfully ported to a 64-bit, 4-processor AMD computer at the TechX Corporation, using a 64-bit version of the lf95 FORTRAN compiler. Scaling studies of NUBEAM showed good scaling up to 4 processors.

Dr. Alexander Pletzer (Tech-X) presented a CPPG seminar on
“Autotools: towards a standard approach for building and sharing
codes” A large number of codes in our community are still built using
hand-written makefiles, an approach that works well for simple
projects but becomes increasingly difficult to support in a world of
multiple architectures, multiple compilers, and multiple programming
languages. Autotools addresses these challenges by providing a
standard set of tools to automate the creation of makefiles.

Week of March 23, 2007

Theory Group

A new model of MHD equilibria has recently been proposed that incorporates elements of ideal MHD theory, Taylor relaxation and chaotic Hamiltonian theory in a mathematically self-consistent manner. This model (proposed by Prof. Dewar of the Australian National University), is described in an article by S.R. Hudson, M.J. Hole and R.L. Dewar (to appear in Physics of Plasmas and can be found online at http://w3.pppl.gov/~shudson/PAPERS/PUBLISHED/HudsonHoleDewar_07.pdf. This article addresses a long-standing issue, for the last fifty years, of stellarator research, i. e. the lack of a consistent formulation of non-trivial MHD equilibria for nonaxisymmetric geometry. The principal issue is that existing codes, that attempt to solve such equilibria, expediently ignore a dense set of singularities in the parallel current inherent to the problem. The first step toward a global equilibrium code which correctly treats this issue has been completed, this being the construction of a Beltrami field in an arbitrary toroidal annulus and an investigation of the associated eigenproblem. Work towards a global equilibrium code is ongoing.

Dr. L. Zakharov gave an Experimental Seminar (03/20/2007) on “The theory of equilibrium reconstruction and a possibility of complete reconstruction in ITER,” (http://w3.pppl.gov/~zakharov). He presented calculations of potential variances in the safety factor,q,  and pressure profiles for different sets of external and internal measurements, envisioned for equilibrium reconstruction in ITER.  In particular, it was shown that complementing the external magnetic measurements with the line shift signals (MSE-LS), recently proposed by Nova Photonics, can significantly improve the reliability of the reconstructed plasma profiles, and thus, could substitute for the conventional line polarization measurements (MSE-LP), which are problematic in ITER.  Including the ability to calculate variances has completed the theory of equilibrium reconstruction, which for a long time had a significant gap in evaluating the quality of the reconstructed equilibrium using present techniques. The new approach was incorporated into the ESC code.

Dr. A. Reiman hosted a National Stellarator Theory Teleconference on March 22.  Dr. S. Nishimura, who is visiting Princeton from NIFS, Japan, gave a presentation on “Development of Moment Approach for Neoclassical Transport in Stellarators.”  The work is of particular interest in providing analytic expressions for transport coefficients in the low collisionality regime where codes such as DKES become very slow.

CPPG Group

A 2 1/2 day workshop was held at PPPL on “The future directions of M3D.”  The workshop was attended by about 24 people, including 12 from outside PPPL and about 6 graduate students from both PPPL and Columbia U.  All present and planned development activities involving the 3D Extended MHD code M3D were described, including those in the areas of higher order spatial discretization and improved algorithms for implicit solves in order to increase the time step, accuracy, efficiency, and parallel scaling properties.  There were several lively discussion sessions, and the last day was spent in creating a more detailed roadmap for M3D development in the next 3 years.  The viewgraphs can be found on the website http://w3.pppl.gov/CEMM on the “workshops” page.
 
A manuscript “On 1D diffusion problems with a gradient-dependent diffusion coefficient” was assigned PPPL-4234 and submitted for publication.  The research note describes how a relatively simple modification to the existing block-tridiagonal linear solvers in most transport codes can be made so that the solutions do not oscillate when using a microstability based transport model such as GLF23.  The modification is shown to be equivalent to applying a single Newton iteration to the non-linear finite difference equations at each point in the grid.
 
Don Batchelor from ORNL visited for 3 days to participate in “driver code” design for the SWIM project.  Progress was made in the areas of the development of a more sophisticated time stepping algorithm that handles “exceptions” such as sawtooth events and the injection of pellets, and in the incorporation of real time graphics using ElVis.  There were discussions with the larger SWIM team about the changes needed to transfer the SWIM framework and codes from the PPPL SGI computer mhd.pppl.gov to the ORNL computer Jaguar.
 
Ravi Samtaney and Stephane Ethier participated in a NERSC Users Group (NUG) conference call.  It was decided that the next NUG meeting will be on Sept 17th, 2007, and will involve training sessions for the new NERSC computer Franklin.

Week of March 16, 2007

Theory Group

Dr. A. Reiman gave a talk at the Third International Workshop on
Stochasticity in Fusion Plasmas (“SFP Workshop”) in Juelich, Germany,
entitled “Ergodization of the Magnetic Field in the W7AS Stellarator
with Increasing Beta.” The question of whether flux surfaces are
lost in high beta stellarator equilibria has been an open question
since the early days of the fusion program, and Dr. Reiman discussed
comparisons of experimental observations at high beta on the W7AS
stellarator with 3D equilibrium calculations which indicate that the
flux surfaces were broken-up over a large fraction of the cross-
section in the experiments. The SFP workshop brought together
physicists working on ergodic diverters in tokamaks, on stellarators,
and on 3D stabilization of ELMs in tokamaks to discuss the physics
common to these configurations.

On March 13, Daren Stotler and Bill Davis ran the Robot Ramble
competition at the New Jersey Science Olympiad in which teams of
students from 20 New Jersey High Schools designed and built a robot
to pick up various objects and place them into a box.

Week of March 9, 2007

Theory Group

The paper by Y. Nishimura, Z. Lin, and W.X. Wang ``Electromagnetic
global gyrokinetic simulation of shear Alfven wave dynamics in
tokamak plasmas'' was accepted for the publication in Physics of
Plasmas. The work represents collaborations between UC-Irvine and
PPPL. The paper demonstrates the capability of simulating long
wavelength (low-n) to short wavelength (high-n) electromagnetic
phenomena simultaneously without any restrictions on the toroidal
mode numbers. The abstract reads ``Electromagnetic gyrokinetic
simulation in toroidal geometry is developed based on a fluid-kinetic
hybrid electron model. The Alfven wave propagation in a fully global
gyrokinetic particle simulation is investigated. In the long
wavelength magnetohydrodynamic (MHD) limit, shear Alfven wave
oscillations, continuum damping, and the appearance of the frequency
gap in toroidal geometries are demonstrated. Wave propagation across
the magnetic field (kinetic Alfven wave) is examined by comparing the
simulation results with the theoretical dispersion relation.
Furthermore, finite-beta stabilization of the ion temperature
gradient (ITG) mode and the onset of the kinetic ballooning mode are
demonstrated.''

There was a TTF Momentum Transport Working Group (East Coast)
Gathering at NYU on March 5, co-organized by J.E. Rice from MIT,
C.S. Chang from NYU, and T.S. Hahm from PPPL. There were nineteen
participants, including experimentalists from NSTX, C-Mod, and
Columbia, as well as theorists from Columbia, MIT, NYU, PPPL, and
UCSD. W. Wang and T.S. Hahm represented PPPL theory department, and other participants from PPPL include S. Kaye, D. Mikkelsen, R.
Budny, S. Scott, and J.M. Kwon.

Dr. Andrew J. Schmitt from Plasma Physics Division of Naval Research
Lab gave a theory seminar entitled “Progress in the physics behind
direct-drive laser fusion energy.” Since it's conception in the early
1970's, direct drive laser fusion has made enormous progress. In the
1980's, the development of optical smoothing techniques and the
switch to shorter laser wavelengths increased laser-target coupling
and reduced the importance of laser-plasma instabilities. The 1990's
brought increased understanding of the ablatively-driven Richtmyer-
Meshkov and Rayleigh-Taylor instabilities, and the concept of
adiabatic-shaping techniques. Finally, in the last decade, the
availability of radiation hydro codes running on massively parallel
computers have allowed us to design targets that can produce high
gain in the presence of hydrodynamic instabilities. Dr. Schmitt
reviewed these developments, and discussed recent advances in
theoretical and experimental physics done at NRL that brighten the prospects for laser fusion energy.

CPPG Group

Doug McCune attended a computer science technical workshop for the
SWIM SciDAC at Indiana University, and gave an update on the status
of the Plasma State software component, which is being used to share
equilibrium and profile information between physics components in
integrated SWIM simulations. At the end of the workshop, using
“Makefile” improvements by Wael Elwasif of ORNL, it was shown that
SWIM participants could successfully update the plasma state
definition through its specification file, with all associated code
automatically regenerated and binaries correctly rebuilt.

An article appeared in HPCWire this week describing the significance
of the GTC benchmarking activity that Stephane Ethier has been
involved in during the last four years. It is described as part of
“one of the most comprehensive performance evaluations of
supercomputers.” The complete article can be found at:http://www.hpcwire.com/hpc/1309580.html.

Week of March 2, 2007

Theory Group

The Theory Department had its monthly group meeting on March 1,
2007. The informational micro-seminars speakers, and their titles
were: Ravi Samtaney on, “An implicit time-stepping method for
resistive MHD,” and Michio Okabayashi on, “Tearing mode
synchronization with a non-axisymmetric feedback-field.”

Drs. Yaroslav Kolesnichenko and Yurii Yakovenko from the Institute
for Nuclear Research in Kiev, Ukraine, arrived to spend one month
working with Roscoe White and others on the interaction of MHD with
high energy particles in NSTX.

Dr. Wei-Li Lee gave a talk, entitled “Integrated Kinetic Simulation
of Fusion Plasmas: Paths to Petascale Computing,” at the Plasma
Physics Colloquium of the Department of Applied Physics and Applied
Mathematics, Columbia University, on February 16, 2007. The focus of
the talk was on the use of the modern-day massively parallel
computers for studying plasma turbulence and the related magnetic
fusion physics based on the Particel-In-Cell method. He also
addressed the issue of discrete particle noise and velocity-space
resolution in kinetic simulations.

CPPG Group

A modification to TRANSP has been implemented to support predictive
applications. Sawtooth events can now be triggered asynchronously
during the course of a simulation, rather than having to be
prescribed from input data. A sawtooth event can be triggered by the
simulation physics criteria, and the time of the sawtooth does not
need to coincide with the long time step boundaries of the TRANSP
heating and current drive source models. In PTRANSP server mode,
supplemental pre-and post-sawtooth plasma state files are used to
organize the exchange of data with the predictive client code. This
capability will be used within the SWIM framework to more accurately
compute the effect of the sawtooth event on the redistribution of the
fast ions.

Stephane Ethier and Joshua Breslau (PPPL Theory) attended the First
Annual Cray Technical Workshop in Nashville, Tennessee on February
26-28 to learn about code optimization considerations on current and
future generation Cray supercomputers. On Wednesday, Dr. Breslau
presented a talk authored by himself and Jin Chen on “Massively
Parallel Magneto-hydrodynamics on the Cray XT3.”

Ravi Samtaney presented the Mechanical & Industrial Engineering
Seminar entitled “Simulations of Pellet Injection in Tokamaks” at
University of Massachusetts, Amherst on Feb 28, 2007.

Week of February 23, 2007

CPPG Group

in Chen attended the 2007 Society of Industrial and Applied
Mathematics (SIAM) Conference on Computational Science and
Engineering and presented a paper in the session, Numerical Methods
for PDEs, entitled “An Alternative Way to Solve Nonlinear PDEs.”

Week of February 16, 2007

Theory Group

Dr. A. Reiman visited the University of Wisconsin at Madison on Feb.
12 and gave a talk entitled "Pressure-Induced Breakup of Flux
Surfaces in the W7AS Stellarator". Analysis of W7AS data indicates
that the achievable beta is being limited by the formation of a large
region of stochastic field lines adjacent to the plasma edge. The
implications of these results for NCSX were also discussed, with the
NCSX configuration designed to have more robust flux surfaces.

Dr. Elena Belova presented a talk entitled, "Hybrid simulations of
rotational instabilities in FRCs' at the Innovative Confinement
Concepts workshop in College Park, MD, Feb. 12-14. This talk
describes the numerical study of rotational modes in FRCs, and
particularly in the FRX-L experiment at LANL.

Dr. Eun-Hwa Kim from the School of Physics, University of Sydney,
Australia gave a theory seminar entitled “Numerical study of linear
mode conversion in multi-fluid plasmas.” She discussed coupling of
plasma modes in inhomogeneous plasmas and linear energy transfer
from one mode to another with constant frequency via the process of
linear mode conversion (LMC). To study LMC in diverse plasma
environments, a three-dimensional multi-fluid simulation code has
been developed. This time dependent model can fully accommodate the effects of multi-ion species and electrons and allowed the study of a wide range of fluid waves from Langmuir oscillations to Alfven waves in an arbitrarily inhomogeneous system. The LMC between two different wave modes has been investigated, in the order of ascending
frequencies, at the Alfven resonance, at the Buchsbaum resonance, at the perpendicular ion cyclotron resonance, and at the plasma
frequency. The simulation study shows that (1) LMC from right- to
left-handed polarized waves occurs at the Alfven resonance. (2) In
multi-fluid plasmas, the energy of the electromagnetic wave is
transferred to the electrostatic wave at the Buchsbaum resonance. (3) At the ion-ion hybrid resonance, the wave energy flows from the left- to right-handed polarized waves when the incoming wave has a small incidence angle. (4) For warm magnetized plasmas, extraordinary waves can be generated by LMC from Langmuir waves.

CPPG Group

R. Samtaney has been elected to a 3-year membership on the National
Energy Research Supercomputer (NERSC) User Group Executive Committee
(NUGEX). He is to represent the Office of Advanced Scientific
Computing Research (OASCR) on the committee. He joins NUGEX vice-
chair S. Ethie