Abstract:

NUBEAM is PPPL's Monte Carlo package for evaluation of the deposition, slowing down, and thermalization of fast ion species in tokamaks. Fast ion species can be created as a result of neutral beam injection or as the product of nuclear fusion reactions. The slowing down calculation includes the effects of collisions with charged species, collisions with beam-injected and background neutral species (leading to charge exchange losses), and the orbit guiding center and finite larmor radius excursions of the fast ion trajectories. Profiles of fusion reaction rates are also computed, taking into account both fast ion - thermal and fast ion - fast ion reaction categories. The model includes simple models for toroidal field ripple loss and MHD "fishbone" losses, along with more comprehensive options for sawtooth mixing and anomolous radial diffusion. The model has been used in the TRANSP package for over twenty years, during which time it has been extensively validated against data from the PLT, PDX, PBX, TFTR, DIII-D, Asdex, JET, JT-60, and Textor tokamaks.

Extraction of the model from TRANSP as an NTCC module was done in 2001-- 2002 by:

• Alexei Pankin
• Doug McCune

The original authors of the code are Rob Goldston, Bob McCann, and Douglas McCune of PPPL. More recent contributions have been made by Rob Andre, Marina Gorelenkova, and K. Indireshkumar.

In 2009, NUBEAM was upgraded to make available ADAS atomic physics. This allows a more accurate treatment of deposition with high energy beams in high density target plasmas where collisional excitation effects play a large role.

Note: To get ADAS state excitation atomic physics set LEV_NBIDEP=2 and NSIGEXC=1 in the NUBEAM control inputs. These are not the defaults. Note also, the ADAS data was acquired for NUBEAM through a software license and is distributed by agreement. Users are requested to cite ADAS references in publications based on calculations that use these features. Appropriate references are listed below.

References:

• The original journal reference is:
  New Techniques for Calculating Heat and Particle Source Rates due to Neutral Beam Injection in Axisymmetric Tokamaks,
  R.J. Goldston et al.,
  J. Comp. Phys. 43 (1981) 61.
  This reference still gives a good description of the basic principles of the code, although features added since 1981 include:
  • angular momentum balance & effects of target plasma rotation
  • generalized, time varying numerical MHD equilibrium & fields
  • fusion product species; simultaneous treament of multiple fast species.
  • anomolous diffusion and sawtooth mixing models.
  
  
• The Tokamak Monte Carlo Fast Ion Module NUBEAM in the National Transport Code Collaboration Library,
  A. Pankin, D. McCune, R. Andre et al.
  Computer Physics Communications Vol. 159, No. 3 (2004) 157-184.

ADAS References:

• ADAS: Atomic Data Modelling and Analysis for Fusion
  H. P. Summers et al., (2007) AIP Conf. Proc. 901,239.
• Neutral beam stopping and emission in fusion plasmas I:deuterium beams
  H. Anderson et al., Plasma Phys. Control. Fusoin 42 (2000) 781-806