Dynamic of Electron Cloud

Description of simulation input and output files

0. Table of contents

1. Source

You can download the program c source here.

2. Using

The command line syntax of the program is

./electron_cloud -i mi.in -o mi.out -s mi_space.out -t mi_traj.out
mi.in - input file,
mi.out - macro output file,
mi_space.out - space distribution output file,
mi_traj.out - trajetory output file.

The results of simulation with Fermilab Main Injector you can find here.

3. Input file

1. count_of_protons_in_bunch_per_unit_of_length_[1/m] - average linear density of protons in bunch. The electric field is calculated using this linear density and the densty of electrons.

2. count_of_primary_electrons_per_unit_of_time_length_at_protons_position_[1/m/sec] - count of generating primary electrons at the center of the pipe (residual gas). Every time step h the count of generaing electrons is h*count_of_primary_electrons_per_unit_of_time_length_at_protons_position (the fraction part generates with probability equals to it).

3. average_energy_of_primary_electrons_at_protons_position_[eV] - initial enegry of this electrons. Not a distribution.

4. count_of_primary_electrons_per_unit_of_time_length_at_chamber_surface_[1/m/sec] - count of generating primary electrons at chamber surface (collisions with walls).

5. average_energy_of_primary_electrons_at_chamber_surface_[eV] - initial enegry of this electrons.

6. walls_material_number_[1=copper;2=stainless_steel] - material of chamber surface. Using in cmee module.

7. cylinder_radius_[m] - the redius of the cylinder. Just a cylinder with circle cross-section.

8. cylinder_length_[m] - simulation length. It non-physical value. Using just for "quality" of calculation.

9. dipol_magnetic_field_[T] - dipol magnetic field in T (in a point!).

10. quadrupole_magnetic_field_[T/m] - dipol magnetic field in T/m. Its a characteristic value of dipol B0/a (in a point!).

11. time_step_[sec] - time step. See the example files for values.

12. max_time_[sec] - the period (includes the bunch and spacing times).

13. off_proton_time_[sec] - bunch time (bunch length over speed of light).

14. beam_size_rms_[m] - the rms size of the proton beam. The bunch density is uniformly distributed in the volume of the cylinder of radius beam_size_rms.

15. repeat_cycle - how many periods in our simulation. The total time is repeat_cycle*max_time.

Notice: the order of paramerers in input file are important.

You can download some examples of input file for Fremilab Main Injector
mi.in, mi_dipol.in, mi_dipol_01.in.

4. Macro output file

1. %d. Iteraction number.
2. %13.8e. Time.
3. %d. Count of electrons.
4. %13.8e. Electron dencity (m-3).
5. %13.8e. Average speed of electrons.
6. %13.8e. Average energy of electrons.
7. %lf. Average count of secondary electrons.
8. %13.8e. Average probility of collision.
9. %13.8e. Time step.
10. %13.8e. Proton density (m-3).

5. Space distribution output file

This file is created every 3000 iteractions.

1. %13.8e. Radius ri.
2. %13.8e. The probability that electron in [ri .. ri + r/50] (r - pipe radius).

6. Trajetory output file

This file with thajectory of some selected electron.

1. %d. Iteraction number.
2. %13.8e. Time.
3. %d. Count of electrons.
4. %d. Index of selected electron.
5. %13.8e. x-coord of selected electron.
6. %13.8e. y-coord of selected electron.
7. %13.8e. z-coord of selected electron.
8. %13.8e. Proton density.

Published 22 Sep 2005. Authors: Panagiotis Spentzouris, Eric Stern, Ivan Sadovsky