**1. NAME AND TITLE**

COLLIMATOR: Monte Carlo Calculation of the Spectrum of Gamma Radiation from a
Collimated Co-60 Source.

**2. CONTRIBUTOR**

Nuclear Engineering Department, University of Illinois, Urbana, Illinois.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV and MAP (Random Number Generator); IBM 7090.

**4. NATURE OF PROBLEM SOLVED**

COLLIMATOR performs a calculation of gamma-ray transport in a finite, multi-region
medium having cylindrical symmetry. The source may be described as a volume of point sources
of various energies. COLLIMATOR has been utilized to calculate the energy spectrum emitted by
a collimated Co-60 source.

**5. METHOD OF SOLUTION**

The Monte Carlo method is used. Splitting is utilized as well as importance sampling of source
directions. In addition, a procedure to facilitate the treatment of boundaries is included in which a
fictitious interaction is employed. In effect, this allows interaction coefficients for one medium to
be used for sampling path lengths in two media. This eliminates the need for calculating coordinates of interface crossing points.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

Estimated running time of the packaged sample problem: one minute on the IBM 7090.

**8. COMPUTER HARDWARE REQUIREMENTS**

The code was designed for the IBM 7090, using standard equipment.

**9. COMPUTER SOFTWARE REQUIREMENTS**

Any FORTRAN compiler may be used. The Random Number Generator (in MAP) may be
replaced.

**10. REFERENCE**

E. E. Morris and A. B. Chilton, "A Monte Carlo Calculation of the Spectrum of Gamma
Radiation from a Collimated Co-60 Source," NRDL-TRC-68-6 (December 1967).

**11. CONTENTS OF CODE PACKAGE**

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

**12. DATE OF ABSTRACT**

August 1971; revised July 1982.

**KEYWORDS:** MONTE CARLO; COLLIMATOR GEOMETRY