1. NAME AND TITLE OF DATA LIBRARY

XCOM: Photon Cross Sections on a Personal Computer, Versions 1.2 and 1.3.

2. NAME AND TITLE OF DATA RETRIEVAL PROGRAMS

XCOM: Program for Retrieval and Display of Photon Cross Sections.

3. CONTRIBUTOR

National Institute of Standards and Technology, Gaithersburg, Maryland.

4. HISTORICAL BACKGROUND AND INFORMATION

The National Institute of Standards and Technology, through its Office of Standard Reference Data, has long maintained and published compilations of measured and evaluated photon cross sections. This compilation of XCOM Version 1.2, released on personal computer media, represents best values as determined in 1987. XCOM1 (Version 1.3), copyright 1991, is similar to XCOM but uses the direct-access unformatted database file UDAT.

5. APPLICATION OF THE DATA

Partial interaction coefficients and total attenuation coefficients are useful in any radiation transport or other radiation analysis application.

6. SOURCE AND SCOPE OF DATA

The data from the National Institute of Standards and Technology are in binary files for 100 elements covering the energy range 1 keV to 100 GeV. The reactions considered are coherent and incoherent scattering, photoelectric absorption, and pair production. The XCOM data are derived from the same source as DLC-136/PHOTX.

7. DISCUSSION OF THE DATA RETRIEVAL PROGRAMS

XCOM is a program for the IBM PC and compatibles for the retrieval and display of the partial interaction coefficients and total attenuation coefficients for elements, compounds, and mixtures. The input is interactive. The user specifies the element or compound chemical symbol or provides weight fractions for each constituent specified by atomic number. A standard energy grid can be used for the output, or the user can modify the energy grid. Two kinds of output are produced: labeled tables for printing or arrays for input to other programs. The output can be in units of cm2/g or barns per atom. Note: the total attenuation coefficient without coherent scattering includes bound Compton scattering.

The XCOM1.2 program is written in Fortran 77 and was tested at RSIC using the Ryan-McFarland Version 2.42 compiler. Both the source program (eight files) and the executable program provided by NIST, compiled by a Ryan-McFarland compiler, are on the distribution diskette. The memory requirement is 256K bytes. The operating system assumed is PC-DOS or MS-DOS, version 2.0 or later. A math co-processor is desirable but not necessary.

The XCOM1.3 subdirectory includes a less system-dependent Fortran source and ASCII data files. This program can be compiled on many systems and was tested at RSIC on an IBM RS/6000 under aix 3.2.5 using the f77 command with the xlf 3.2.2.3 compiler. It was also tested on a Northgate 486 using the Lahey F77 Vers. 5.1 compiler under DOS 6.0 with 8MB memory and on a P5-120MHz with 16MB memory under Windows 95. The PC executables RSIC created when testing are included in this directory. XTRANS must be run to convert the ASCII data to binary before executing XCOM.

8. DATA FORMAT AND COMPUTER

ASCII Fortran source, binary and ASCII data files and executable program (D00174/IBMPC/00).

9. TYPICAL RUNNING TIME

The programs are interactive.

10. REFERENCES

RSIC "README.RSI" (June 1996).

M. J. Berger and J. H. Hubbell, "XCOM: Photon Cross Sections on a Personal Computer," NBSIR 87-3597 (July 1987).

11. CONTENTS OF LIBRARY

Included are the referenced documents and one 3.5 inch (1.4 MB) DS/HD diskette which contains the data files, Fortran source files, executable files, and text (ASCII) documentation files in DOS format.

12. DATE OF ABSTRACT

June 1996.