last modified: 25-AUG-1988 | catalog | categories | new | search |

NEA-1026 LOUHI82.

LOUHI, Generator Spectra Unfolding Program with Linear and Nonlinear Regularization

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1. NAME OR DESIGNATION OF PROGRAM:  LOUHI82.
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2. COMPUTERS
To submit a request, click below on the link of the version you wish to order. Only liaison officers are authorised to submit online requests. Rules for requesters are available here.
Program name Package id Status Status date
LOUHI82 NEA-1026/01 Tested 25-AUG-1988

Machines used:

Package ID Orig. computer Test computer
NEA-1026/01 IBM 3033 IBM 3090
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3. DESCRIPTION OF PROGRAM OR FUNCTION

Unfolding or deconvolution of the solution of Fredholm integral equations of the first kind is required in the interpretation of several physical measurements. Examples of such include neutron spectroscopy with activation detectors, moderating spheres or proton recoil measurements, and numerous others of analogous nature. The mathematical problem typically does not have a unique solution and in consequence prior knowledge of the solutions must be used by regularization or other methods to obtain physically meaningful solutions.

LOUHI82 contains response functions identified as follows:

Au197G, Au97Gc, Au97N2, Sc45Ng, Sc45Gc, U238Ng, U238Gc, U238Nf, U235Nf, U235Fc, Np237F, Co59Ng, Co59Gc, Fe58Ng, Fe58Gc, Fe54Np, Ti46Np, Ti48Np, Ni60Np, Ni58Np, DAMAGE.
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4. METHOD OF SOLUTION

The unfolding problem is formulated as a generalized least squares problem whose objective function includes  in addition to matching the measured data prior information of the smoothness, shape and magnitude of the solution, as available. These conditions are formulated either as a linear regularization problem  which can be solved through fast matrix inversion techniques or a nonlinear regularization problem allowing also for logarithmic or relative weighting of the conditions and guaranteeing a nonnegative  solution by using gradient minimization methods.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Designed primarily for the so-called few-channel problems the dimensions of the present version allow for up to 40 arguments and solution points.
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6. TYPICAL RUNNING TIME

Problems with 10 response functions and 40 solution points typically require about 4 sec of UNIVAC 1108 CPU time with the faster linear method and about 15 sec with the iterative nonlinear method.
NEA-1026/01
NEA-DB ran the test case included in this package on an IBM 3090 computer in 37 seconds of CPU time.
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7. UNUSUAL FEATURES OF THE PROGRAM

LOUHI82 is designed to be applicable to a large number of physical problems and to be extended to incorporate also other unfolding methods, such as parametric representation and linear programming techniques to make it a truly  general purpose program offering a multitude of algorithms to choose and compare.
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8. RELATED AND AUXILIARY PROGRAMS:
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9. STATUS
Package ID Status date Status
NEA-1026/01 25-AUG-1988 Tested at NEADB
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10. REFERENCES:
NEA-1026/01, included references:
- J.V. Sandberg:
  Application of the Program LOUHI82 to Reactor
  Neutron Spectrum Unfolding.
  TKK-F-A524(1983)  (July 15, 1983)
- J.V. Sandberg:
  Differences of the LOUHI82 Input from the LOUHI78 Input
  TKK-F-C69  (February 24, 1983)
- J.T. Routti and J.V. Sandberg:
  General Purpose Unfolding Program LOUHI78 with Linear and
  Nonlinear Regularizations.
  Reprint from "Computer Physics Communications", 21 (1980), 119-144
- J.V. Sandberg and J.T. Routti:
  Unfolding Triga Reactor Neutron Spectra from Multicomponent
  Activation Detector Data with LOUHI82.
  Reprint from "Nuclear Technology", 63 (1983), 170-175
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11. MACHINE REQUIREMENTS:
NEA-1026/01
To run the test case on IBM 3090, 404K bytes of main storage were required.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-1026/01 FORTRAN-77
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:
NEA-1026/01
MVS/XA (IBM 3090).
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHORS

           J.T. Routi and J.V. Sandberg
           Helsinki University of Technology
           Department of Technical Physics
           SF-02150 Espoo, Finland
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16. MATERIAL AVAILABLE
NEA-1026/01
File name File description Records
NEA1026_01.001 INFORMATION FILE 65
NEA1026_01.002 LOUHI82 FORTRAN SOURCE PROGRAM 3320
NEA1026_01.003 JCL TO RUN THE SAMPLE CASE ON IBM 104
NEA1026_01.004 SAMPLE CASE INPUT 435
NEA1026_01.005 SAMPLE CASE OUTPUT 2425
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17. CATEGORIES
  • O. Experimental Data Processing

Keywords: activation analysis, neutron detectors, neutron recoil, neutron spectra, spectra unfolding.