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Manuscript Title: Analysis of photonuclear yield curves by the variable Bin Penfold- Leiss method.
Authors: P.D. Allen, Su Su, E.G. Muirhead
Program title: VBPL
Catalogue identifier: AAVC_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 21(1980)163
Programming language: Fortran.
Computer: CDC CYBER -73.
Operating system: SCOPE 3.4.
Word size: 60
Peripherals: disc.
Keywords: Nuclear physics, Particle detection, Photonuclear Cross-section, Matrix inversion, Variable bin Penfold-leiss.
Classification: 17.5.

Nature of problem:
Various standard procedures have been evolved for the unfolding of photonuclear cross sections from a measured set of bremsstrahlung induced yield curves. This program uses the Variable Bin Penfold-Leiss (VBPL) method of matrix inversion to obtain a set of cross section values each with its corresponding energy resolution. Various options are available. These include (1) conventional constant bin Penfold- Leiss analysis, (2) operator pre-determined analysis bin width, variable with photon energy, (3) choice of X-ray spectrum (presently either Schiff IOA or Bethe-Heitler) most appropriate for the X-ray convertor thicknesses used and the likely range of analysis bin widths, (4) provision for modification of the incident spectrum by absorption of the incident beam, both before and in the irradiated target, (5) the absolute calibration of the bremsstrahlung incident energy relative to the standard monitor ionization chamber, (6) the choice of presenting either the experimental yield data with corresponding X-ray monitor response for preliminary processing in the form of yield per unit monitor response, the so called reduced yield, or the presentation of the set of reduced yield data obtained from an alternative or external processing procedure.

Solution method:
The matrix conversion procedure is used. Selection of the analysis bin width can be made on the basis of the statistical criterion suggested by Thies. This may proceed under automatic program control or subsequently by operator specification in order to minimize rapid changes of analysis bin width.

The input data can consist of up to 230 yield points. The response function of the standard (P2) dose monitor is described by a polynomial of degree 5 or less; that of an experimental transmission dose chamber by a polynomial of degree 4 or less. If the user is specifying the analysis bin widths, up to 50 changes of these may be preselected. Absorption in the sample may be specified by absorption coefficients at up to 20 energy values.

Unusual features:
The flexibility in selection of the analysis bin widths allows the user to obtain optimum resolution in the analysed cross section consistent with the statistical quality of the input data at that stage over the full energy range.