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NESC0983 EGUN.

EGUN, Charged Particle Trajectories in Electromagnetic Focusing System

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1. NAME OR DESIGNATION OF PROGRAM:  EGUN.
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2. COMPUTERS
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Program name Package id Status Status date
EGUN NESC0983/02 Tested 06-NOV-2002

Machines used:

Package ID Orig. computer Test computer
NESC0983/02 IBM 370 series PC Pentium III 500
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3. DESCRIPTION OF PROBLEM OR FUNCTION

EGUN computes trajectories of charged particles in electrostatic and magnetostatic focusing systems including the effects of space charge and self-magnetic fields. Starting options include Child's Law conditions on cathodes  of various shapes, user-specified conditions input for each ray, and a combination of Child's Law conditions and user specifications. Either rectangular or cylindrically symmetric geometry may be used.  Magnetic fields may be specified using an arbitrary configuration of coils, or the output of a magnet program, such as Poisson, or by an  externally calculated array of the axial fields.
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4. METHOD OF SOLUTION

The program first solves Laplace's equation. Next, the first iteration of electron trajectories is started using  one of the four starting options. On the first iteration cycle, space charge forces are calculated from the assumption of paraxial flow. As the rays are traced, space charge is computed and stored. After all the electron trajectories have been calculated, the program begins the second cycle by solving the Poisson equation with the space charge from the first iteration. Subsequent iteration cycles follow this pattern. The Poisson equation is solved by an alternate column relaxation technique known as the semi-iterative Chebyshev method. A fourth-order Runge-Kutta method is used to solve the relativistic differential equations of the trajectory calculations.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maxima of -
9001 mesh points in a square mesh
300 mesh points in the axial direction
100 mesh points in the radial direction
101 potentials
  51 rays
In the cylindrical coordinates, the magnetic fields are axially symmetric. In rectangular coordinates, the external field is assumed to be normal to the plane of the problem, which is assumed to be the median plane.
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6. TYPICAL RUNNING TIME

Running times vary greatly with the problem and the computer.
NESC0983/02
NEA-DB executed the test case on PC in 3 seconds.
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7. UNUSUAL FEATURES OF THE PROGRAM

EGUN has special options for round beams in rectangular coordinates, heavy ion beams, image tubes, shadow grids, and dielectrics.
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8. RELATED AND AUXILIARY PROGRAMS

An auxiliary plotting program is included with the package. EGUN supersedes the programs described in SLAC-51 and SLAC-166.
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9. STATUS
Package ID Status date Status
NESC0983/02 06-NOV-2002 Tested at NEADB
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10. REFERENCES

- W.B. Herrmannsfeldt:
  Numerical Design of Electron Guns and Space Charge Limited
  Transport Systems
  SLAC-PUB-2631, October 1980
- W.B. Herrmannsfeldt:
  Poisson Equation Solving Program
  SLAC-51, September 1965
- W.B. Herrmannsfeldt:
  Electron Trajectory Program
  SLAC-166, September 1973
NESC0983/02, included references:
- W.B. Herrmannsfeldt:
  Electron Trajectory Program.  SLAC-226  (November 1979)
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11. MACHINE REQUIREMENTS

450 Kbytes of memory and two direct-access devices (logical unitd 1 and 8) are required.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0983/02 FORTRAN
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13. SOFTWARE REQUIREMENTS: OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED
NESC0983/02
Tested at the NEA Data Bank on DOS.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

   EGUN
uses the SLAC system routine, LEFT1, to determine the amount of CPU  time remaining for job execution. This was not supplied. NESC substituted a dummy subroutine LEFT1 and function ICLOCK for testing. Function ICLOCK is a Basic Assembly Language routine which  calculates the elapsed CPU time. The sample plotting program included in the package uses the proprietary CALCOMP graphics library. Users will have to supply alternative timing and plotting rouintes suited to their local computing environment. Prospective new users of the program may contact the author to determine whether EGUN is appropriate for their intended applications.
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15. NAME AND ESTABLISHMENT OF AUTHOR

W.B. Herrmannsfeldt
Stanford Linear Accelerator Center
Stanford University
P.O. Box 4349
Stanford, Calfornia 94305, U.S.A.
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16. MATERIAL AVAILABLE
NESC0983/02
egun.for  Fortran source file
iclock.asb IBM assembler subroutine
plot.for  Plot source file
plotfile.dat  Data for Plot source file
Input and output files
report  SLAC-226  (November 1979)
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17. CATEGORIES
  • V. Particle Accelerators and High Voltage Machines

Keywords: Dirichlet problem, Laplace equation, accelerators, beam dynamics, beam transport, electron beams, finite difference method, ion beams, klystrons, phase space, poisson equation, r-z, x-y.