1. NAME AND TITLE

TRAPP: Transport of Alpha Particles and Protons with all Nuclear Reaction Products Neglected.

AUXILIARY ROUTINES

INTRIGUE-2L: Linear, Logarithmic and Semilogarithmic Plot Routine.

TRAPPL: TRAPP Data Plot Routine.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

TRAPP is primarily intended for carrying out studies of the shielding required to protect astronauts against Van Allen belt protons and against solar-flare protons and alpha particles. The program treats the transport of protons and alpha particles through a homogeneous shield and tissue with the assumptions that all nuclear-reaction products may be neglected and all particles travel in a straight line and undergo a continuous slowing down. The geometry considered is that of a spherical shell shield with a tissue sphere at its center. For an isotropically incident proton or alpha-particle flux per unit energy with maximum energy < 3 GeV, the program gives the particle flux per unit energy, the absorbed-dose rate, and the dose-equivalent rate at the center of the tissue sphere as a function of the spherical-shell-shield thickness.

TRAPP may also be used for any arbitrary incident proton or alpha particle spectrum with maximum energy < 3 GeV.

5. METHOD OF SOLUTION

The program computes numerically the analytic solution to the one-dimensional Boltzmann equation for primary charged-particle flux as a recursive function of the depth increment, or in the shield and in the tissue ball. Attenuation by nuclear collisions is optional. Dose integrals are performed at the center of the tissue ball which may have radius equal to zero as an option.

The shield material may include hydrogen and elements with A > 12. The user must supply the proton stopping power in the shield as a function of energy between an arbitrary minimum, ECUT > .1 MeV, and an arbitrary maximum, EMAX < 3 GeV. All other stopping powers and nuclear cross sections are supplied by the program and described in the manual.

The incident Van Allen belt proton flux energy spectrum must be supplied by the user. Proton and alpha fluences from solar flares may be input or optionally computed in the program. Arbitrary proton or alpha fluxes may be used as inputs as pseudo Van Allen or solar flare fluxes.

The sample problem uses TRAPP for solar-flare proton and alpha-particle spectra with characteristic rigidity of 100 MV incident on an aluminum spherical shell shield of maximum thickness of 100 g/cm², and the incident particle spectra were obtained directly from the code. The sample problem gives the results of calculations with attenuation due to nuclear collisions both included and neglected. Input data and output for this sample case are included in the package.

6. RESTRICTIONS OR LIMITATIONS

Only one homogeneous spherical shell shield is permitted. The maximum number of elements in the shield is ten. The minimum shield thickness is 2 g/cm2 and the maximum is 100 g/cm²; both values can be changed by modifying the initial values of NIOPUT and IOPUT which are given in data statements in subroutine MAC.

7. TYPICAL RUNNING TIME

The sample problem took 57 seconds on the IBM 360/91 computer.

8. COMPUTER HARDWARE REQUIREMENTS

TRAPP is operable on the IBM 360/370 computers. It uses standard I-O and a maximum of 2 additional tapes or direct access devices.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN IV compiler is required. A Calcomp plotting package, INTRIGUE-IIL is required to process TRAPPL. INTRIGUE-IIL is included in the package.

10. REFERENCES

J. Barish, R. T. Santoro, F. S. Alsmiller, R. G. Alsmiller, Jr., "TRAPP, A Computer Program for the Transport of Alpha Particles and Protons with all Nuclear-Reaction Products Neglected," ORNL-4763 (August 1972).

Janet Endress, R. T. Santoro, J. Barish, "TRAPPL: A Program for Producing Calcomp Plots from Data Generated by TRAPP," ORNL-TM-3813 (July 1972).

M. B. Emmett, "INTRIGUE-II: An IBM-360 Subroutine Package for Making Linear, Logarithmic and Semilogarithmic Graphs Using the Calcomp Plotter," ORNL-4664 (March 1971).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents and one (1.2MB) DOS diskette which contains the source code and sample problem input and output.

12. DATE OF ABSTRACT

March 1973; updated May 1975.