Nuclear Instruments and Methods最新文献

A correction formula for the counting loss in a TPHC-PHA time analyzer is verified experimentally, after deriving the formula by several methods and obtaining a more refined correction formula. The experiment is made by the application of a gate circuit, which inhibits irrelevant signals, to conventional electronic equipment for measuring the neutron time-of-flight spectra. Lastly we propose the application of the method used in our experiments to general spectra measurement.

Thies et al. [3] recently proposed a method to measure photonuclear cross-sections with quasi-monochromatic photons - using bremsstrahlung as the source of radiation. In this method each yield ordinate has to be measured independently three times. It is shown here how one can make use of the ensuing replication of data to test thoroughly and unambiguously the reliability of the experimental ensemble used and the validity of the derived cross-section data.

We have developed a FORTRAN program that performs spectrum analysis using the advantages given by the non-iterative methods for small computers. With the inclusion of simple calculations for the precise determination of fitting intervals, by means of the normal cumulative distribution, we improve the precision of the usual stripping methods and resolve overlapping peaks.

A new method for checking the goodness-of-fit in gamma spectroscopy in proposed. Theoretical calculations are verified with the installation of the new formula into a gamma spectrum analysis program SAMPO78. The new method is clearly shown to be more sensitive in detecting irregular peak shapes and unsatisfactory fitting results than the usual χ² per degrees of freedom test.

Monte Carlo calculation are described which confirm that the response of a spherical thermal-neutron detector at the centre of a spherical moderating assembly in a neutron beam diverging from a point source is simply related to its response in a parallel neutron beam.

An iron septum magnet was designed for the charged-particle beam splitting system. Magnetic field measurements of the septum model magnet with a circular hole were performed for several conditions. The hole field is B₀ = 60–250 G for a hole radius of 12 mm and the gap field is B_g = 5–6 kG for a gap distance of 8 mm with a septum thickness of 1 mm. The multipole field strength in the circular hole is obtained from the field distribution.

Improvements in the determination of the energy levels of radioisotopes by the sum-peak technique of coincidence counting have been achieved by the utilisation of two Ge(Li) detectors. The performances of the spectrometer, and the validity of the method of interpretation of the γ-ray spectrum and of the shape of the continuum have been tested from the decay of ²⁰⁷Bi and ^110mAg.

A simple active aperture for the suppression of slit scattering in a magnetic spectrometer, using the sensitive area of a parallel plate avalanche counter, is described. The suppression of background at low excitation energies and small angles for inelastic scattering is demonstrated.

The peak shapes of X-ray lines vary from those of gamma-ray lines in spectra obtained from semiconductor detectors due to different natural line widths for both types of radiation. This excludes the application of the same peak evaluation method for both gamma and X-ray peaks and complicates gamma-ray emission rate determinations with detectors calibrated by X-ray sources and vice versa. The order of magnitude of possible errors is calculated and ways to overcome the problem are discussed.

A comparison between the absolute efficiency values of HgI₂ and NaI detectors has been carried out for six different source-to-detector arrangements. The HgI₂ and NaI detectors have been cansidered as equal in volume. Six different detector sizes and sources sizes have been used in the calculations. The calculations have been performed in the γ-ray energy region 60–1500 keV with the Monte Carlo method using a Univac 1100 computer. Water has been used as the source medium.