RSICC CODE PACKAGE PSR-529

 

1.         NAME AND TITLE

UMG 3.3 - Unfolding with Maxed and Gravel.

 

2.         CONTRIBUTORS

Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany.

 

3.         CODING LANGUAGE AND COMPUTER

Fortran 90; PC under Windows (P00529PC58600).

 

4.         NATURE OF PROBLEM SOLVED

UMG (Unfolding with MAXED and GRAVEL) is a package of seven programs written for the analysis of data measured with spectrometers that require the use of unfolding techniques.  See the developers’ website for information on training courses http://www.ptb.de/en/org/6/utc2002/intro.htm.

The program MAXED applies the maximum entropy principle to the unfolding problem, and the program GRAVEL uses a modified SAND-II algorithm to do the unfolding.  There are two versions of each: MXD_FC33 and GRV_FC33 for “few-channel” unfolding (e.g., Bonner sphere spectrometers) and MXD-MC33 and GRV_MC33 for “multi-channel” unfolding (e.g., NE-213).

The program IQU can be used to calculate integral quantities for both MAXED and GRAVEL solution spectra and, in the case of MAXED solutions, it can also be used to calculate the uncertainty in these values as well as the uncertainty in the solution spectrum.  The uncertainty calculation is handled in the following way: given a solution spectrum generated by MAXED, the program IQU considers variations in the measured data and in the default spectrum and uses standard methods to do sensitivity analysis and uncertainty propagation.  There are two versions:  IQU_FC33 for “few channel” unfolding and IQU_MC33 for “multi-channel” unfolding.

The program UMGPlot can be used to display the results from the unfolding programs MAXED and GRAVEL in graphical form in a quick and easy way.

 

5.         METHOD OF SOLUTION

MAXED is based on the maximum entropy principle.  The solution to the unfolding problem is obtained by maximization of the relative entropy (used here in the form due to Skilling, which is a generalization of the usual expression to distributions that are not necessarily normalized) subject to constraints imposed by the measurements.  This approach permits the inclusion of prior information in a well defined and mathematically consistent way, and it leads to a solution spectrum that is a non-negative function which can be written in closed form.  This last feature permits the use of standard methods for sensitivity analysis and propagation of uncertainties, which are implemented in program IQU. GRAVEL is an iterative unfolding program that was first developed for the HEPRO package.  It uses a slight modification of the SAND-II algorithm.

 

6.         RESTRICTIONS OR LIMITATIONS

The “few-channel” programs MXD_FC33, GRV_FC33 and IQU_FC33 can analyze data sets with up to 100 measurements and can handle fluence vectors with up to 1000 energy bins.

The “multi-channel” programs MXD_MC33, GRV_MC33 and IQU_MC33 can analyze data sets with up to 4096 measurements and can handle fluence vectors with up to 4096 energy

bins.

 

7.         TYPICAL RUNNING TIME

The running time will depend on the complexity of the problem, the number of measurements and the number of energy bins used to describe the fluence vector.  On a PC with an Intel Pentium III, 866 MHz, 256MB, the running times for the examples included in the package are of the order of:

 

MXD_FC33:      < 10 s               MXD_MC33      210 s

GRV_FC33:       <2 s                  GRV_MC33:      450 s

IQU_FC33:        <2 s                  IQU_MC33:       100 s

 

Large, complex problems may require more time; for example, MXD_MC33 may require one hour or more when the number of measurements and the number of energy bins used to describe the fluence vector are close to the maximum allowed values.

 

8.         COMPUTER HARDWARE REQUIREMENTS

UMG runs on PCs running  Windows 95/98/ME and Windows NT/2000/XP.  The complete package needs about 11 Mbytes on the computer hard disk.

 

9.         COMPUTER SOFTWARE REQUIREMENTS

The package comes with installation programs that can be used for Windows 95/98/ME and Windows NT/2000/XP (in the case of other platforms, the package must be installed manually).UMG was compiled and tested at RSICC on a Pentium IV running Windows XP. The codes are expected to run on other computer systems but have only been tested on personal computers. The programs MAXED, GRAVEL and IQU were written in Fortran 90 and compiled with the Compaq Visual Fortran (version 6.1) compiler.  The program UMGPlot was written using the programming environment ComponentOne Studio for ActiveX.  The installation programs were created using the “WinZip Self_Extractor 2.2" which initiates a batch file with DOS commands. The included executables run on a variety of personal computers under various Windows operating systems such as Windows 95 and Windows XP.

 

10.        REFERENCES

M. Reginatto, Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany, “The ‘Few-Channel’ Unfolding Programs in the UMG Package: MXD_FC33, GRV_FC33 and IQU_FC333” (March 1, 2004).

            M. Reginatto, Physikalisch-Technische Bundesanstalt (PTB), Braunschweig,Germany, “The ‘Multi-Channel’ Unfolding Programs in the UMG Package: MXD_MC33, GRV_MC33 and IQU_MC33” (March 1, 2004).

M. Reginatto, Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany, “Manual for the Program UMGPlot.”

 

11.        CONTENTS OF CODE PACKAGE

UMG is transmitted on CD-ROM. Included in the package are the source files for all programs, PC executables, test cases, implementation instructions, procedures, description of sample problem cases, and documentation.

 

12.        DATE OF ABSTRACT

March 2004.

 

KEYWORDS:   BONNER SPHERE; NEUTRON; SENSITIVITY ANALYSIS; UNCERTAINTY ANALYSIS; UNFOLDING