NEA-0599 NE-SPEC.

1. NAME OR DESIGNATION OF PROGRAM:  NE-SPEC. The Unfolding Code System for the NE213 Liquid Scintillator.

3. DESCRIPTION OF PROBLEM OR FUNCTION

The NE-SPEC system is composed  of three types of programs:
- The code to convert the pulse height distributions from counts    per channel to counts per light unit.
-  The code to generate the response matrix.
-  The unfolding code(s).

4. METHOD OF SOLUTION

Considering the three code types in turn:

As the unit of the pulse height distribution must be matched to that of the response matrix, it is necessary to convert from counts per channel to counts per light unit. In this system the light unit used is the Na light unit. Also a new calibration method is used to determine the coefficients of the linear expression that defines the relationship between the channel number and the light unit. This method utilizes the relations between the values of the light unit for the energy of the Compton peak and the corresponding channel number of the gamma ray sources.

The response matrix of the NE213 is obtained using Monte Carlo.
47 neutron groups are used in the test run, with cross sections from ENDF/B-IV. The light output data is that evaluated by Verbinski et al. The response matrix is reduced to 34 groups for the unfolding. The pulse height meshes are arranged at equal log spaces from 0.001  to 10.0 Na light units with 60 mesh points per decade.

For unfolding, two codes, FERDOS and ITEM-II, which are based on different principles are available, so as to check their results. FERDOS employs a constrained least squares unfolding procedure whilst ITEM-II uses an iterative unfolding method.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Number of data points per unit decade of pulse height intervals - max. 60.
Number of decades in the pulse height region - max. 4.
Pulse height of initial mesh in Na units - min. 0.001.
Number of channels in the measured pulse height distribution - max.  1024.
Number of data points of the pulse height distribution - max. 150.
Maximum size of response matrix is 55 (neutron energy mesh)*165 (light output mesh).

6. TYPICAL RUNNING TIME

The whole system running time required is less than 3 mins (on the FACOM 230/75).

NEA-DB executed the test cases on IBM 3081. The following CPU times were required for the different modules:
              SYSMATRIX       57.97 seconds
              CHNTLU           0.23
              FERDOS           0.08
              ITEM-II          2.09

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

NE-SPEC is a code system that uses  the data conversion code CHNTLU, the response matrix generating code SYSMTRIX, and the unfolding codes FERDOS (a modified version of FERDO) and ITEM-II.

10. REFERENCES

- V.V. Verbinski et al.:
  "Calibration of an Organic Scintillator for Neutron Spectrometry"
  Nucl. Instr. and Meth. 65, 8 (1968).

- Nobuo Sasamoto and Shun-ichi Tanaka:
  The Unfolding Code System for the NE213 Liquid Scintillator
  JAERI-M6952 (February 1977)

11. MACHINE REQUIREMENTS:  Less than 85 k core storage.

To run the test case, main storage requirements for the different modules are:
                        SYSMATRIX      256K bytes
                        CHNTLU         136K
                        FERDOS         292K

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  MVS-SP (IBM3081)

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHOR

          N. Sasamoto and S. Tanaka
          Japan Atomic Energy Research Institute
          Division of Reactor Engineering
          Tokai-Mura
          Naka-gun, Ibaraki-ken
          Japan.

File name	File description	Records
NEA0599_01.003	NE-SPEC INFORMATION FILE	96
NEA0599_01.004	SYSMATRIX SOURCE	383
NEA0599_01.005	CHNTLU SOURCE	151
NEA0599_01.006	FERDOS SOURCE	278
NEA0599_01.007	ITEM-II SOURCE	270
NEA0599_01.008	JCL	81
NEA0599_01.009	SYSMATRIX INPUT DATA	1985
NEA0599_01.010	CHNTLU INPUT DATA	89
NEA0599_01.011	FERDOS INPUT DATA	28
NEA0599_01.012	ITEM-II INPUT DATA	28
NEA0599_01.013	SYSMATRIX PRINTED OUTPUT	561
NEA0599_01.014	CHNTLU PRINTED OUTPUT	432
NEA0599_01.015	CHNTLU PUNCHED OUTPUT	52
NEA0599_01.016	FERDOS PRINTED OUTPUT	78
NEA0599_01.017	ITM-II PRINTED OUTPUT	330