1. NAME AND TITLE

LPPC: Proton Penetration Code.

AUXILIARY ROUTINES

NCON: Nuclear Constants Generator.

LMFC: Mission Flux Generator (Trapped Radiation).

FLARE: Mission Flux Generator (Solar Flux Events).

LSSC: Source Spectrum Converter.

LIGHT: Inelastic Gamma-Ray Production Code.

MSGAM: Multi-slab Gamma-Ray Code.

The proton range and stopping power data required as input to MSGAM may be calculated using computer code package CCC-50/LRSPC, which must be specifically requested if desired.

LPPC is one of a series of space codes maintained by RSIC to preserve the technology. Between 1966-1968, the code package was distributed eight times.

2. CONTRIBUTOR

Lockheed-Georgia Company, Nuclear Analysis Department, Marietta, Georgia.

3. CODING LANGUAGE AND COMPUTER

FAP (LPPC), FORTRAN II and FAP (LMFC, LSSC, LIGHT, MSGAM), FORTRAN II (NCON), FORTRAN IV and MAP (FLARE); IBM 7090 and 7094.

4. NATURE OF PROBLEM SOLVED

The proton penetration code, LPPC, calculates primary and secondary doses behind multi-strata slab or spherical shell shields due to an incident proton flux spectrum. NCON calculates secondary production constants for the LPPC library. LMFC calculates proton and electron flux spectra integrated over trajectories through the trapped radiation belts of earth. Arbitrary trajectories or orbital parameters may be specified.

The FLARE code provides a stochastic estimate, at various probability levels, of proton and alpha spectra which arise from solar flux events. LSSC facilitates preparation of proton input spectra for LPPC. The LIGHT code estimates gamma ray spectra resulting from inelastic nucleon-nucleus collisions. MSGAM computes gamma ray dose due to the distributed sources developed by LPPC.

5. METHOD OF SOLUTION

The LPPC program computes the primary proton spectrum and the production and attenuation of secondary components at discrete points through the shield by evaluating solutions to a pair of coupled integro-differential equations. The straight-ahead approximation is used for all radiation components except evaporation neutrons and inelastic gamma rays which are assumed to be generated isotropically. LMFC converts geographic coordinates to B-L coordinates and performs logarithmic interpolations in flux maps.

The FLARE code uses Monte Carlo techniques to estimate the occurrence, magnitude, and spectrum of solar flux events over the duration of a mission. An inverse square correction is applied to interplanetary missions. LSSC converts five types of spectra to spectra differential in energy. Spectra integral in energy are fitted with an approximating function which is differentiated. Spectra integral in rigidity are converted to spectra integral in energy, then treated as described above. Spectra differential in rigidity are converted by transforming from rigidity to energy units. Power law spectra, integral in energy, are differentiated directly.

The LIGHT program follows the gamma ray cascade from excited levels of residual nuclei by evaluating a solution to an integral equation. Discrete levels are used where data are available; at higher energies, a statistical model of the nucleus is used. All transitions are assumed to proceed via electric dipole. These data may be used in LPPC.

MSGAM treats isotropic gamma sources embedded non-uniformly in a slab shield. A point kernel calculation is performed utilizing appropriate buildup factors. The dose is computed at the exit face of each layer. This code uses source data generated by LPPC.

6. RESTRICTIONS OR LIMITATIONS

LPPC: Number of strata 10

Number of strata subdivisions (layers) 100

Number of input spectrum points 150

Slab shield or spherical shell shield.

LMFC: Number of trajectory points 150

FLARE: Number of days in mission 1000

The FLARE program is intended to treat missions consisting of an integral number of days.

LSSC: Number of input spectrum values 50

Number of output spectrum values 250

In some cases, the input data should be plotted and smoothed before processing.

LIGHT: Number of discrete levels 50

Number of level width ratios 100

Number of isotopes 20

Number of output spectrum values

discrete 100

continuous 100

Number of steps for solving equation 1000

MSGAM: Number of source energies 20

Number of layers 100

Number of materials 12

Number of energy flux-to-dose conversion factors 50

Number of mass attenuation coefficients per material 30

Number of Compton scattering cross sections per material 30

7. TYPICAL RUNNING TIME

Time given is for the IBM 7094:

LPPC: Variable; usually 7 layers per minute for isotopic case, 25 layers per minute for monodirectional case.

NCON: A few seconds per case.

LMFC: Variable, usually two minutes per 100 point orbit.

FLARE: Approximately 2 histories per second for a 450 day mission; 40 histories per second for a 14 day mission.

LSSC: Approximately 2 seconds per spectrum.

LIGHT: Approximately 25 seconds per case.

MSGAM: Variable, 90 seconds for a 10 energy, 24 layer case.

Estimated running time of the sample problem through all the routines on the IBM 7090: 50 minutes.

8. COMPUTER HARDWARE REQUIREMENTS

All routines operate on the IBM 7090 or 7094 computers. The FLARE code may also be run on the IBM 360/50. These routines require standard input, output, and punch tapes, plus an on-line printer for operator instructions. In addition, LPPC requires two working tapes on Channel B.

9. COMPUTER SOFTWARE REQUIREMENTS

This package requires a standard IBM monitor system with a FAP assembler and a FORTRAN II compiler with the exception of the FLARE code which requires the FORTRAN IV compiler. Certain nonstandard arithmetic subroutines are furnished with the package as binary card decks. In some cases, these have been translated into FAP by members of the RSIC staff.

10. REFERENCES

C. W. Hill, C. C. Douglass, Jr., W. B. Ritchie, K. M. Simpson, Jr., "Computer Programs for Shielding Problems in Manned Space Vehicles," ER-6643 (January 1964).

C. W. Hill, W. B. Ritchie, K. M. Simpson, Jr., "Data Compilation and Evaluation of Space Shielding Problems, Volume II, Dose Calculations in Space Vehicles," ER-7777 (August 1965).

C. W. Hill, W. B. Ritchie, K. M. Simpson, Jr., "Data Compilation and Evaluation of Space Shielding Problems, Volume III, Radiation Hazards in Space," ER-7777 (April 1966).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents and one (1.2MB) DOS diskette which contains, in separate files, the source card decks for all the routines, the input for sample problems, a BCD library of cross sections, punched card output, and the BCD output from each code for the sample problems.

12. DATE OF ABSTRACT

July 1967; updated July 1981; revised January 1983, February 1985.