1. NAME AND TITLE

CHARGE: Space Radiation Shielding Code - Proton and Electron Penetration of Multilayered Slabs and Spheres.

This package is retained by RSIC to preserve space technology developed in the 1960's. Originally developed for the IBM 7090, it was later rewritten for the IBM 360/370 and CDC 6500. The current version includes implementation on a PC.

2. CONTRIBUTORS

Missile and Space Systems Division, Douglas Aircraft Company, Inc., Santa Monica, California, contributed the original code system.

Nuclear Technology and Subsystems Branch, McDonnell Douglas Astronautics Company, Western Division, Huntington Beach, California.

Experimental and Mathematical Physics Consultants, Gaithersburg, Maryland.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370 (A); FORTRAN 77, IBM PC (B); CDC 6000 series (C).

4. NATURE OF PROBLEM SOLVED

CHARGE was designed to compute the dose rates and energy fluxes behind multilayered shields exposed to electrons and/or protons. Also, the doses due to electron, primary proton, electron bremsstrahlung, secondary proton, and secondary neutron radiations are calculated as a function of penetration into the shield.

5. METHOD OF SOLUTION

For protons the straight-ahead approximation technique is used in treating the high-energy "cascade" particles produced from nonelastic nuclear collisions. The code assumes that the low-energy "evaporation" secondary neutrons from nonelastic nuclear collisions are emitted isotropically and takes into account this angular dependence. Data developed by Bertini is employed for particle production from high-energy nonelastic collisions.

For electrons the range-energy calculation assumes the same functional relationship between penetration and energy as was used for protons.

Empirically corrected Born-approximation cross-sections for electron bremsstrahlung production calculations have been employed within the CHARGE code.

6. RESTRICTIONS OR LIMITATIONS

Restrictions and limitations of major consequence are not known.

Number of regions in shield < 100.

The PC version does not have the plotting capability.

7. TYPICAL RUNNING TIME

No study of typical running time for CHARGE problems for the mainframe version (A) has been made by RSIC. Estimated running time for sample problem: 0.06 hour.

For the PC Version (B), the sample problem CHARGE.DAT took about 23 minutes on an IBM PC/AT with a math coprocessor.

8. COMPUTER HARDWARE REQUIREMENTS

The code is operable on the IBM 360/75/91 and the CDC 6500 and the IBM PC with or without a math coprocessor.

9. COMPUTER SOFTWARE REQUIREMENTS

The code may be compiled and executed on FORTRAN IV Operating Systems with standard I-O, systems, and 2 scratch tapes assigned.

A special FORTRAN IV-written subroutine has been packaged with double precision and input capabilities. Plotting routines (SC 4020) are included but may be bypassed by an input parameter. Provisions are also included to bypass clock sampling and data routines.

A FORTRAN 77 compiler is required for the PC Version. The compiler used was Microsoft FORTRAN Version 5.0 under the DOS 3.3 operating system.

10. REFERENCES

J. R. Lilley and W. R. Yucker, "CHARGE, A Space Radiation Shielding Code," SM-46335 (April 1965).

W. R. Yucker and J. R. Lilley, "CHARGE Code for Space Radiation Shielding Analysis," DAC-62231 (April 1969).

README.DOC, informal notes for the IBM PC, EPMC, (October 1990).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents and one (1.2MB) DOS diskette which contains the source code, overlay control cards, and sample problem data, and output from running the sample problem.

12. DATE OF ABSTRACT

January 1968; updated July 1981, February 1985, December 1990.