1. Code Name: MH3D-K Code

2. Category: 3D Nonlinear Particle/Fluid Hybrid Simulation

3. Responsible Physicist: G-Y Fu

4. Others involved in code development: W. Park, S. Parker

5. One line description: Gyrokinetic energetic particles/MHD fluid 3D initial value code.

6. Computer systems which code runs on: Cray J90

7. Typical running time: 3 hours

8. Approximate number of code lines: 35,000 lines

9. Does this code read data files from another code? yes, M3D, M3D-T, PEST.

10. Does this code produce data files that can be read by another code? If so, explain. M3D, M3D-T.

11. 1-2 paragraph description of code: The MH3D-K code treats fast non-thermal ('hot') ions as gyrokinetic parties which contribute to the pressure tensor in the MHD background fluid. The MHD part in turn gives B and E field by which the gyrokinetic particle trajectory is determined. This scheme can be called a pressure coupling in the combined momentum equation. Alternatively, the bulk fluid momentum equation can be used with current coupling(instead of the pressure) to produce a similar system. Two noise reduction schemes are used: the double trajectory method and the delta_f method.

12. Similar codes to this code, and distinguishing differences: After this code is published, several codes are developed using the same hybrid scheme. Vlad in Italy uses the pressure coupling scheme but with reduced MHD equations. Todo in Japan uses the current coupling scheme. E. Belova and R.E. Denton in Dartmouth have developed a current coupling scheme code for space physics applications.

13. Journal References describing code: W. Park et al. Phys. Plasmas 6, 1796 (1999); G. Y. Fu and W. Park, Phys. Rev. Lett. 1594 (1995); W. Park et al., Phys. Fluids B , 2033 (1992)

14. New code capabilities planned for next 1-2 years: Extension to unstructured mesh. Massively parallel version.

15. Code users: G-Y Fu, W. Park, N.N. Gorelenkov

16. Present and recent applications of code: Applied the code to stabilization of internal kink mode and nonlinear saturation of TAE and fishbone modes.

17. Status of code input/output documentation. Check one: ( ) does not exist (X) incomplete ( ) exists

18. Year Code was first used and present frequency of use: 1992. At present, the code with delta_f method is being used for simulations of internal kink mode, fishbone, TAE and other MHD modes driven by fast ions.

19. Estimate of Man-Years invested in developing code: 2 years

20. Catagories of usage of Code (Check all that apply): (x) application code to do analysis and prediction of experiments (x) numerical testbed of theoretical ideas ( ) physics module to be used in integrated moddelling ( ) code for machine design

21. Language code is written in: Fortran

22. Results of intercomparisons with other codes and results of validation against experiments. Benchmarked against NOVA-K for linear internal kink mode and TAE modes. The scaling of nonlinear saturation due to the wave-particle trapping agreed with an analytic theory.