Masateru Sonoda

A fast neutron time-of-flight spectrometer with neutron-gamma ray discrimination

Abstract A fast neutron time-of-flight spectrometer with neutron-gamma ray discrimination based on the method developed by Alexander et al. is described. A combination of a 5″ dia. NE213 liquid scintillator and a 5″ dia. XP1040 photomultiplier is used both for neutron-gamma discrimination and neutron energy measurements. This spectrometer has a time resolution less than 2.0 nsec and is used at a counting rate as high as 4 × 104 pps.

Protons from 40Ca bombarded with 14.1 MeV neutrons

Abstract Energy spectra and angular distributions were measured for protons emitted from 40 Ca bombarded with 14.1 MeV neutrons. The constant-nuclear-temperature formula for level density fits the energy distribution for backward angles and yields a nuclear temperature of 1.34 ± 0.04 MeV for 40 K. The angular distributions of the protons emitted through compound process are nearly symmetric around 90°. The spin cut-off parameter is estimated to be about 2.0 from the angular distribution of protons emitted by the (n, p) reaction. The cross sections for the (n, p) and (n, np) reactions through compound process are 471 ± 21 mb and 180 ± 32 mb, respectively. The direct (n, p) reactions has a cross section of about 11 mb.

Large area mosaic solid-state detectors for low yield fission study

Abstract A number of silicon surface barrier detectors has been arrayed in mosaic structure to increase the sensitive area by an order of magnitude. It has been used as a remote detector at the end of the flight tube in the double-energy single-time-of-flight measurements of 252 Cf spontaneous fission fragments and found to be as good in performance as a small detector ordinarily used.

Background in associated-particle time-of-flight technique

Abstract The background which limits the use of the associated-particle in the neutron time-of-flight technique is considered in a model experiment of 238 U(n,f) reaction induced by 14 MeV neutrons. It is found that the background in the flight-time spectrum does not vanish even in the ideal case in which there are no sources of “uncorrelated” events.

Stabilization of spectrum with no reference peaks

Abstract Methods to stabilize a spectrum with no reference peaks are considered. Locating one of the two windows of a usual stabilizer in the flat region of spectrum and the other in the uppermost channel region, and setting unequally the widths or the gains of the two windows, it is found possible to stabilize the spectrum with no regerence peaks by comparing the counting rates in the two windows.

Angular distribution of neutrons from precompound decay in inelastic scattering

Abstract Precompound angular distribution in inelastic scattering of 14 MeV neutrons are analysed in terms of surface interaction with the higher exciton states taken into account. This model is applied to some (p, α) reactions also.

Magnetic field of alternately charged symmetric multipole magnet

Abstract The magnetic field of an alternately charged symmetric 2 N -pole magnet is calculated, using the conformal transformations. The formulae are given for the equipotential line, the line of force, the field strength, the magnetomotive force and the total magnetic flux passing through the surface of a pole piece.

The Efficiency of the G-M Counter

The efficiency, i. e. the counting probability per one quantum of the thick-walled γ-ray counter was computed theoretically by making some simplifying assumptions for several energies between 10 mc 2 and 34 mc 2 (Li-p γ-ray) and for different wall thickness. The efficiency of the thin-walled counter was also discussed.

Some Improvements in a Neutron Time-of-Flight Spectrometer for D+T Neutrons

Some improvements in a neutron time-of-flight spectrometer using the associated particle method are described. A simple circuit is devised to compensate the dependence of the flight-time of neutrons of a given energy on the pulse height of the output signals of the neutron detector. By the use of this circuit in the time-of-flight spectrometer having been used in this laboratory a time resolution of 1.2 nsec (f.w.h.m.) is obtained for direct neutrons from the D+T source. The spectrometer system is also so improved that two neutron detectors operate together with a single set of circuits for n-γ discrimination and time-to-pulse height conversion. The effects of the shadow bar and detector shielding on the background level are studied. The background is reduced by an order of magnitude by the use of a suitable shadow bar and detector shield.

Standardization of Linear Circuits in Nuclear Pulse Measuring System

An attempt of standardization of linear circuits in nuclear pulse measuring system is described. By the use of one circuit block, a number of transformations of linear pulses were accomplished. An operational amplifier fullfilling above-mentioned requirements was designed.