1. NAME AND TITLE

NE-SPEC: A Code System for Unfolding a Pulse Height Distribution of Neutrons Measured by an NE-213 Organic Scintillator.

AUXILIARY ROUTINES

SYSMTRIX: Response Matrix Generator.

CHNTLU: Measured Pulse Height Distribution Converter.

FERDOS: Unfolding Code.

ITEM2: Unfolding Code.

2. CONTRIBUTOR

Japan Atomic Energy Research Institute, Ibaraki-ken, Japan.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; FACOM 230/75.

4. NATURE OF PROBLEM SOLVED

NE-SPEC determines neutron spectra from measured pulse height distributions of neutrons by a NE-213 scintillator.

5. METHOD OF SOLUTION

NE-SPEC employs unfolding procedures. FERDOS uses a constrained least-squares unfolding method and ITEM2 uses an iterative unfolding method.

The pulse height distribution measured in unit of count per channel is first converted to that in a Na light unit. Coupling of the low and high gain data follows the data conversion. A response matrix of a NE-213 scintillator to neutrons is prepared by smearing the Monte Carlo calculation.

6. RESTRICTIONS OR LIMITATIONS

The maximum channel numbers for pulse height distribution is 1024. The maximum size of the response matrix is 55 (neutron energy mesh) x 165 (light output mesh).

The response matrix and almost all the input data are arranged to be common to both FERDOS and ITEM2. A feature of these routines is that both the lower and upper limit of the pulse height region for unfolding can be selected in parametric manner. Occasionally, a slight change of the number of the neutron energy meshes in the matrix causes large differences among the unfolded spectra, especially those unfolded by FERDOS. Therefore, the most reliable solution can be selected among the series of unfolded spectra obtained by changing step by step the lower limit of the neutron mesh of the response matrix.

It is recommended that the user measure the pulse height distributions by both the lower and higher gain measurements and couple them together. This is because the coupled data spread the energy region of the unfolded spectrum and also the smoothly coupled data assure that the pulse height distribution will not be contaminated by gamma rays and that the pulse height calibration will be made correctly.

7. TYPICAL RUNNING TIME

On the FACOM 230/75, SYSMTRIX requires about 2 minutes to generate a smeared response matrix. The other routines require less than 10 seconds. The entire code will run in less than 3 minutes.

8. COMPUTER HARDWARE REQUIREMENTS

NE-SPEC is operable on the FACOM 230/75 computer.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCE

N. Sasamoto and S. Tanaka, "The Unfolding Code System for the NE213 Liquid Scintillator," JAERI-M 6952 (February 1977).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

April 1984.