1. 200 kV gun GPT simulations Tee, shroom and sphere catohdes
Gabriel Palacios
08/02/18

2. Summary

3. Solidworks geometry modifications: No shield

4. Solidworks geometry modifications: Original

5. Solidworks geometry modifications: GTS with small anode

6. Solidworks geometry modifications: No shield

7. Solidworks geometry modifications: Original

8. Solidworks geometry modifications: GTS with small anode

9. Cathode-anode gap:
The data for the following plots was taken along the cathode anode gap as a function of the height (on the photocathode surface) varying from -6mm to 6mm.

10. GPT Global particle tracker uses three files to run this simulation:
The initial file (with extension *.ini) with general info about the particles
The multiple run file (*.mr) that allows for parameter sweep
The batch file (*.bat) that launches the code to obtain solution and converts the solution files to trajectories for plots

11. GPT: *.ini
This is the main file that GPT uses to obtain a simulation, contains:
Initial particle information
Global components
Accuracy
Particle distribution
Field maps
Space charge switch and parameters

12. GPT: *.mr We use a multiple run file that contains:
Switches for space charge and backwards moving particle removal (not used here)
Particle Info
Output settings
Beamline Component Variables

13. GPT: *.bat
The batch file uses the console to run GPT codes to obtain the results and plots, it contains three lines:
The mr and gpt commands run the GPT solver with the *.ini file (combined with the multirun file) as targets and obtain the main solution file (*.gdf)
Gdf2a converts the solution binary file to a “normal” text file
Gdftrans uses the information in the solution file and converts it to particle trajectories

14. Braking the code
Let us brake the codes in parts

15. Braking the code: *.ini Initial particle information
E0 is the initial energy of particles in the distribution.
MTE (mean transverse energy) is defined in the *.mr file as [eV]
Xyrms is defined in the *mr file as 0.32e-3 [m].

16. Braking the code: *.ini Global components
maxTime is a variable that tells tout when to stop.
tout “Writes the electromagnetic fields at the position of all particle coordinates at the given simulation time to the GPT outputfile. ”
Zstop 0.5

17. Braking the code: *.ini Accuracy
GBacc “Negative base 10 logarithm of the simulation accuracy for γβ . If not specified, 4 is assumed.”
xacc Negative base 10 logarithm for the simulation accuracy for position. If not specified, 6 is assumed. It is rarely needed to change this value. Increasing
GBacc usually increases the accuracy for the position simultaneously.

18. Braking the code: *.ini Particle distribution Nparticles 1000
Qbunch -12e-12 [C]
Xyrms 0.32e-3 [m]
If transU is 1, distribution is uniform, else Gaussian transverse laser
If longU is 1, distribution is uniform, else Gaussian longitudinal laser
Trms 50E-12 Bunch length
Zcutoff 3

19. Braking the code: *.ini Particle distribution
setrxydist(set,distribution)
Set radial distribution in x - coordinate.
setphidist(set,distribution)
Set phi distribution.
settdist(set,distribution)
Set particle-release time distribution.
settransform(ecs,set)
Apply a coordinate transform on the particles in a set.

20. Braking the code: *.ini Particle distribution
setGBxdist(set,distribution)
Sets the momentum distribution in x-direction.
setGBxemittance(set,emittance)
Sets the emittance in x β x-space. Modifies: γβ x.
These elements scale the transverse momentum coordinates linearly till the specified emittance is reached.
dtmaxt(tstart,tend,dtmax)
Enforce a maximum timestep within a specified interval.

21. Braking the code: *.ini Field maps
map3D_E(ECS,mapfile.gdf,x,y,z,Ex,Ey,Ez,Efac)
Reads a 3D rectangular field map for the electric field from the specified GDF file.

22. Braking the code: *.ini
Space charge

23. Braking the code: *.ini
Removed bits

24. Braking the code: *.ini Output
tout(from,to,step,[CCSname]) Writes the electromagnetic fields at the position of all particle coordinates at the given simulation time to the GPT outputfile.
dtout 0.5E-11 in seconds
screen(ECS,at,[CCSname])
Writes particle coordinates when the particles pass through a nondestructive screen to the outputfile.
Normally, GPT stops execution after the last tout or screen .

25. Braking the code: *.ini
Bonus!
Setxydistbmp

26. Braking the code: *.mr

27. Braking the code: *.mr Switches Sccalc Surface charge calculation
Noback removes backwards movingparticles

28. Braking the code: *.mr
Particle info

29. Braking the code: *.mr
Output

30. Braking the code: *.mr
Beam line components

31. Braking the code: *.bat

32. Braking the code: *.bat Line 1 Line2 Line 3 Line 4 Line 5 Line 6
The gpt command runs on the *.ini file and solves it using the conditions set in the *.mr file. This stores the general solution in the *.gdf file together with particle positions
Line2
Converts the general solution binary file to a *.txt file to use with excel
Line 3
Obtains the particle trajectories from the general solution and saves it to the trajectories_*.gdf file
Line 4
Calculates the standard deviations from the general solution and stores them in the std_*.gdf
Line 5
Calculates the normalized emittance and stores it in the nemi_*.gdf file
Line 6
Converts the binary standard deviations into a *.txt file to use with excel
Line 7
Converts the binary trajectories into a *.txt file to use with excel

33. Preliminary results

34. Preliminary results: Fields maps

35. Preliminary results: Fields maps

36. Preliminary results: Fields maps

37. Preliminary results: x vs y

38. Preliminary results: x vs y

39. Preliminary results: x vs y

40. Preliminary results: Trajectories

41. Preliminary results: Trajectories

42. Preliminary results: Normalized transverse emittance

43. Preliminary results: Normalized transverse emittance

44. Preliminary results: Normalized transverse emittance

45. Preliminary results: Normalized transverse emittance

46. Preliminary results: Normalized transverse emittance

47. Preliminary results: Normalized transverse emittance

48. Preliminary results: Normalized transverse emittance

49. Preliminary results: Normalized transverse emittance

50. Preliminary results: Normalized transverse emittance

51. Preliminary results: Normalized transverse emittance

52. Preliminary results: Normalized transverse emittance

53. Preliminary results: Normalized transverse emittance

54. Fin.