**1. NAME AND TITLE**

THRUSH: Calculates Thermal Neutron Scattering Kernel.

**2. CONTRIBUTOR**

Century Research Center Corporation, Tokyo, Japan.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; Cray-XMP.

**4. NATURE OF PROBLEM SOLVED**

THRUSH computes the thermal neutron scattering kernel by the phonon expansion method for both
coherent and incoherent scattering processes. The calculation of the coherent part is suitable only for
calculating the scattering kernel for heavy water.

**5. METHOD OF SOLUTION**

To evaluate the scattering kernel from the double differential scattering cross section, it is
necessary to perform angular integration over scattering angle. This integration is performed
analytically in the THRUSH code. A "generalized" spectral density is used from which the coherent
as well as the incoherent scattering effect can be calculated. The Sjoelander expansion or short time
expansion is used to overcome the poor convergence at high incident neutron energy or high
temperature. The inter- molecular elastic scattering from the atom pair of different molecules of heavy
water is evaluated using Butler's model.

**6. RESTRICTIONS OR LIMITATIONS**

Maximum number of frequency mesh points for spectral density is 400 (IMAX). Maximum
number of convolution integrals for the n-th phonon term is 8000/IMAX. The maximum number of
energy meshes for the scattering kernel is 101.

**7. TYPICAL RUNNING TIME**

No information on execution times is available.

**8. COMPUTER HARDWARE REQUIREMENTS**

THRUSH runs on Cray computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

The code runs under COS using the CFT 1.11 compiler.

**10. REFERENCE**

H. Kadotani, "THRUSH: A Code for Calculating Thermal Neutron Scattering Kernel," JAERI-M
8927 (June 1980).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one (1.2MB) DOS diskette that contains the source file,
sample input and output.

**12. DATE OF ABSTRACT**

November 1989.

**KEYWORDS: ** THERMALIZATION