CCC-0117 BETA-2B.

1. NAME OR DESIGNATION OF PROGRAM:  BETA-2B.
Bremsstrahlung and Electron Transport Analysis.

3. DESCRIPTION OF PROBLEM OR FUNCTION

BETA-2B is a time-dependent Monte Carlo bremsstrahlung and electron transport analysis code for  complex geometries. It is designed primarily for electron energy deposition calculations.
The electron transport includes the effects of fixed electric and magnetic fields and self-produced electric fields. In following both primary and knock-on electrons, energy loss straggling effects are included.
The code solves photon transport not only from bremsstrahlung sources, but also from a fixed source. The effects of incoherent and coherent (Compton) scattering, pair production and photoelectric processes are included.
BETA-2B accepts generalized source distributions that are functions of space, angle, energy and time, including sources for which both energy and intensity vary with time.
The code can treat both simple 1,2 and 3-dimensional multiple material geometries, or complex 3-dimensional quadric surface geometries.

4. METHOD OF SOLUTION

BETA-2B uses a condensed history Monte Carlo technique.
The electron transport proceeds by calculating the length of each electron segment from a preset fractional energy loss. The electron  is allowed to traverse this path and its direction and energy are altered by random sampling a multiple scattering distribution and an energy loss straggling distribution.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Calculational
accuracy within 5 per cent of experimental results can be obtained for both low and high atomic number targets in the energy range from 0.05 to 15.0 MeV. The program can be applied outside this energy range, although the physical models are less accurate at lower energies.
Data arrays are packed into the blank COMMON block using variable dimensioning techniques. The length of blank COMMON is sufficient for fairly complex problems; unusually large problems, particularly  those requesting many of the optional output edits,may require the storage allocation to be increased.

6. TYPICAL RUNNING TIME

The following sample problems were run on a CDC 6600.
i) A calculation of the angle-energy distribution of an 8 MeV  electron beam as it penetrates a slab of aluminium, using a P24  Goudsmit-Sanderson distribution, 2 per cent energy loss per  path length segment, and following 3000 histories required 15      minutes.
ii) About 5 minutes were required to calculate the energy  deposition profile for a beam of 2 MeV electrons normally  incident on a semi-infinite slab of aluminium or lead. A  Gaussian angular straggling model was used, with 2 per cent      energy loss steps, and 500 histories were followed.
iii) A source of 10 MeV electrons, normally incident at one end of a  system of concentric cylinders of aluminium, iron and tungsten  with a central void was set up. Each cylinder was divided into  25 regions. The energy deposition distribution was calculated  using 5 per cent energy loss steps, and following 256 histories  Less than 2 minutes were required for a no-field case, 10  minutes were required with a 100,000 gauss uniform axial      magnetic field.
iv) A time-dependent energy deposition calculation on a lucite  cylinder require 7 minutes for 10 time steps. The electron  source was normally incident and uniformly distributed on the  end of the cylinder which was divided into 5 radial and 20  axial segments. 64 electron histories were followed per time      step.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

BETA-2B is the end-product of many  modifications to BETA (reference 2).

10. REFERENCES

- Thomas J. Jordan:
  BETA, A Monte-Carlo Program for Bremsstrahlung and Electron
  Transport Analysis
  AFWL-TR-68-III (October 1968).

- Thomas M. Jordan:
  BETA-2, A Time-Dependent, Generalized Geometry Monte Carlo Program
  for Bremsstrahlung and Electron Transport Analysis
  Volume I: Summary Report, Volume II: Users Manual
  A.R.T. Research Corporation Report ART-60 (October 29, 1971).

11. MACHINE REQUIREMENTS

The amount of core storage depends on the size of the blank COMMON block, and the degree of overlay. The maxi- mum degree of program segmentation for efficient operation is given  in volume 2 of reference 1. Five external storage units are required.
The program interfaces with the Calcomp plotting package through four entry points: PLOT, PLOTS, SYMBOL and NUMBER. If plotting is required the dummy subprograms with these names should be removed.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  OS for IBM 360.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHOR

Thomas J. Jordan
A.R.T. Research Corporation
1100 Glendon Avenue
Los Angeles
California 90024, USA

File name	File description	Records
CCC0117_01.001	BETA-2B SOURCE - FORTRAN IV	13765
CCC0117_01.002	BETA-2B OVERLAY CARDS	79
CCC0117_01.003	BETA-2B JOB CONTROL	5
CCC0117_01.004	BETA-2B SAMPLE PROBLEM INPUT	68
CCC0117_01.005	BETA-2B SAMPLE PROBLEM OUTPUT	317