1. Code Name: GEM1

2. Category: IXb. Particle Code: Gyrokinetic

3. Responsible Physicist: W. W. Lee

4. Others involved in code development: S. Parker

5. One line description: 1D electromagnetic gyrokinetic particle code.

6. Computer systems which code runs on: Cray, SUN, any UNIX-based system.

7. Typical running time: Production run takes hours.

8. Approximate number of code lines: 1000

9. Does this code read data files from another code? No.

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

11. 1-2 paragraph description of code: This is a 1D slab particle code for studying shear Alfven physics and drift instabilities.

12. Similar codes to this code, and distinguishing differences: This is a gyrokinetic slab code written in the gyrokinetic units. It has both linear and nonlinear capabilities.

13. Journal References describing code (up to 3): W. W. Lee, J. Comput. Phys. 72, 243 (1987). A. M. Dimits and W. W. Lee, J. Comput. Phys. 107, 309 (1993). S. E. Parker and W. W. Lee, Phys. Fluids B 5, 77 (1993).

14. New code capabilities planned for next 1-2 years: Finite-beta effects.

15. Code users: W. Lee

16. Present and recent applications of code: Noise problems, df-code, finite-beta

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

18 Year Code was first used: 1989

19. Estimate of Man-Years invested in developing code: 0.25

20. Catagories of usage of Code (Check all that apply): ( ) 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 writen in: Fortran

22. Results of intercomparisons with other codes and results of validation against experiments. The numerical method for the \delta f scheme, which has now been widely used in the community, was first developed here. We are now using this code to design a new efficient scheme for studying shear-Alfven waves.