NESC0263 GASKET

1. NAME OR DESIGNATION OF PROGRAM:  GASKET

3. DESCRIPTION OF PROBLEM OR FUNCTION

GASKET calculates the thermal
neutron  scattering  law,  s(alpha,beta), for  a  large  class  of
moderators.  Provision has  been made in GASKET  for the following
dynamical modes of the scatterer -
   (1)  free translation (gas),
   (2)  diffusive or Brownian motion,
   (3)  harmonic isotropic vibrations with continuous frequency
        spectrum,
   (4)  harmonic anistropic vibrations with continuous frequency
        spectrum (as applied for instance to graphite),
   (5)  harmonic isotropic vibrations with discrete frequency
        spectrum.

4. METHOD OF SOLUTION

Neutron scattering kernels  are obtained from
the scattering law using the relation
sigma(e0 to e,theta) = (sigmab/4pi)*sqrt(e/e0)*exp(-beta/2)*
where  e0  and e  are,  respectively,  initial and  final  neutron
energies, theta is  the cosine of the neutron  scattering angle in
the  laboratory, and  alpha and  beta respectively,  dimensionless
momentum and energy transfers.  GASKET calculates s at points of a
2-dimensional  alpha,beta mesh.   Numerical  methods  are used  to
evaluate Fourier transforms of s.  For  very large values of alpha
and  beta an  option is  included  to use  Wick's short  collision
approximation for s.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maxima of -
   100 points in distributed frequency spectrum
   100 points in anisotropic part of the frequency spectrum
     2 discrete oscillators if w sub 1 does not equal zero, other-
       wise 20
    20 phonon terms calculated for each delta line

6. TYPICAL RUNNING TIME

10 minutes are required  on the UNIVAC1108;
8 on the CDC6600.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

An auxiliary  code, FLANGE  (NESC
Abstract 247), is used to  generate cross section information from
the scattering law.

10. REFERENCES

J. U.  Koppel, J.  R. Triplett,  and Y.  D. Naliboff,
GASKET, A  Unified Code  for Thermal  Neutron Scattering,  GA-7417
Revised, March 10, 1967.
             GASKET Update Note, GGA Note.
             Integral  Neutron   Thermalization,  Annual   Summary
Report, GA-8280, pp. 146-152, September 30, 1967.

11. MACHINE REQUIREMENTS

32K machine  with about  26K available  for
the program and one scratch unit (drum, disk, or tape)

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:   EXEC2.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHORS

   Program       J. U. Koppel, J. R. Triplett, and Y. D. Naliboff
   Abstract      D. H. Houston
                 General Atomic Company
                 P. O. Box 81608
                 San Diego, California  92138

File name	File description	Records
NESC0263_01.001	SOURCE PROGRAM (FORTRAN)	1460
NESC0263_01.002	SAMPLE PROBLEM	64
NESC0263_01.003	OUTPUT LIST OF SAMPLE PROBLEM	1381