**1. NAME AND TITLE**

FSCATT: Discrete Ordinates Gamma-Ray Transport Code System in Plane Geometry.

FSCATT was preceded by the FHUFF code which treated photoelectric absorption and forward fluorescence.

**2. CONTRIBUTORS**

Systems, Science and Software, La Jolla, California.

Bell Aerospace Textron, Buffalo, New York.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV; UNIVAC 1108 and FORTRAN 77; IBM 3033.

**4. NATURE OF PROBLEM SOLVED**

FSCATT calculates the spatial distribution of gamma-ray energy absorbed in a multilayered target for an arbitrary incident x-ray spectrum at an arbitrary angle. In addition, the transmitted spectrum at the rear of the target is calculated as a function of energy and angle.

K-shell fluorescence is treated as an isotropic source in each cell of the mesh. Compton scattering is modeled using the Klein-Nishina collision cross section to calculate the scattering source distribution.

FHUFF is used extensively to design and analyze x-ray shields. In FSCATT, both forward and backward fluorescence as well as Compton scattering are treated in plane geometry.

**5. METHOD OF SOLUTION**

FSCATT is a discrete ordinates energy deposition and transport code which accounts for photoelectric absorption, fluorescence, and Compton scattering in slab geometry. The code allows multilayer calculations with each layer consisting of a mixture of elements. The option to include test materials and/or calculate the deposition in heterogeneous materials is provided. The intensity and distribution of the radiation field is computed in terms of finite angular and energy groups in each cell of the mesh.

FSCATT is a numerical treatment of photoelectric absorption, scattering, and fluorescence in plane geometry.

**6. RESTRICTIONS OR LIMITATIONS**

Provisions for the use of 80 energy groups to resolve the scattered and fluorescent radiation are included in the code. Additional resolution can be obtained at the expense of core storage.

There is no numerical limit on the upper photon energy which can be transported by FSCATT, but since pair production is not treated, the accuracy of the solution becomes questionable above 1 MeV.

**7. TYPICAL RUNNING TIME**

Calculations using 100 energy groups to resolve the incident spectrum, 20 energy groups, and 6 angular groups to resolve the scattered and fluorescence radiation, and 50 cells on the mesh requires less than 1 minute of computer time on a UNIVAC 1108 or IBM 3033.

**8. COMPUTER HARDWARE REQUIREMENTS**

FSCATT is configured to operate on a UNIVAC 1108 with at least one tape drive and access to high-speed drum storage of 200,000 words. It also runs on the IBM 3033.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A FORTRAN IV compiler is required. The IBM VS FORTRAN 77 compiler was used on the IBM 3033.

**10. REFERENCES**

R. H. Fisher and R. A. Kruger, "A Numerical Treatment of Scattering and Fluorescence in Plane Geometry," DASA 2418 (May 1971).

R. H. Fisher and J. W. Wiehe, "A User's Guide to the FSCATT Code," DASA 2618 (November 1970).

N. Adonakis, Bell Aerospace Textron transmittal letter (September 1985).

**11. CONTENTS OF CODE PACKAGE**

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

**12. DATE OF ABSTRACT**

May 1975, revised December 1988.

**KEYWORDS:** DISCRETE ORDINATES; GAMMA-RAY; SLAB; ONE-DIMENSION;
MULTIGROUP