Yutaka Furuta

Response of 6LiF and 7LiF thermoluminescence dosimeters to fast neutrons

Abstract Energy responses of the integral thermoluminescence of magnesium-activated 6 LiF and 7 LiF thermoluminescence dosimeters (TLD) were obtained experimentally to neutrons of energies from 17 keV to 14 MeV with 60 Co equivalence in roentgens; the responses were compared with the calculated values of the kerma. Glow curves of the TLDs to neutrons were also studied, thereby revealing several facts.

Revised energy responses of 6LiF and 7LiF thermoluminescence dosimeters to neutrons

Abstract The energy response of a 6 LiF TLD to neutrons reported previously was revised by experiments. The kermas of 6 LiF and 7 LiF TLDs were also calculated more accurately, and compared with the experimental energy response.

Usage of a thermoluminescence dosimeter as a thermal neutron detector with high sensitivity

Abstract Thermal neutron measurements by thermoluminescence dosimeters have been studied in paired 6LiF and 7LiF or UD-136N and UD-137N. The results have a similar meaning to that of Au foils. The detectable minimum thermal neutrons fluence by the present method is about 104 n/cm2, which corresponds to a thermal neutron flux of several n/cm2 s with one hour exposure.

GAMMA-RAY PULSE DOSIMETER

A gamma‐ray dosimeter, which has a response expressible in roentgens and high sensitivity with a small active volume, is described. The major parts of this dosimeter (gamma‐ray pulse dosimeter) are a scintillation counter using an organic scintillator and an electronic integrator, with special care to reduce the counting loss. This dosimeter is sensitive to x or gamma rays with energies above 50 keV, and has an air equivalent response for energies above 200 keV with maximum response at 80 keV (+14%). A linear temperature dependence (0.5%/°C) is obtained under 40°C.

Estimation of gamma-ray exposure in mixed gamma-neutron fields by 6LiF and 7LiF thermoluminescence dosimeters in pair use

Abstract A procedure to estimate gamma-ray exposure in mixed gamma-neutron fields using a pair of 6LiF and 7LiF thermoluminescence dosimeters is described. In this method, only the “shape” of neutron spectrum is sufficient to know the exposure. Three types of neutron spectrum, i.e. monoenergetic, 1/E and fission, are investigated for the application.

SPECTRUM MEASUREMENTS OF INTERMEDIATE ENERGY NEUTRONS BY AN ORGANIC SCINTILLATOR.

Abstract The pulse height distribution was obtained experimentally for monoenergetic neutrons having energies from 566 keV to 52 keV with a newly developed gamma-ray pulse shape discriminator, the risetime to pulse height converter (RHC), in conjuction with an NE-213 scintillator. The gamma-ray rejection and the discrimination loss of 52 keV neutrons were estimated to be 99.4% and 13%, respectively, and the estimated neutron energy corresponding to the cut-off of the pulse height distribution was 20 keV. The light outputs of the NE-213 scintillator for neutrons (protons) to the energies are also shown in 60 Co light units.

Neutron capture cross section measurements of 155Gd and 157Gd from 1.1 to 235 keV

Abstract Neutron capture cross section measurements of 155 Gd and 157 Gd were made at the Japan Atomic Energy Research Institute linac in the energy range from 1.1 to 235 keV. The results were compared to other measurements and to the JENDL-2 evaluation. The analysis of the capture cross sections by the least squares method gives the following average resonance parameters: 10 4 S 0 = 3.00 ± 0.28, 10 4 S 1 = 3.7 ± 1.1, 〈 Γ s γ 〉 = 119 ± 29 eV, 〈 Γ p γ 〉 = 140 ± 60 eV for 155 Gd; and 10 4 S 0 = 2.23 ± 0.57, 10 4 S 1 = 2.2 ± 0.7, 〈 Γ s γ 〉 = 115 ± 28 eV, 〈 Γ p γ 〉 = 129 ± 25 eV for 157 Gd.

Utilization of Fe-filtered neutron beam for total cross section measurements up to 1 MeV

Abstract An iron filtered neutron beam has been made to be available at the time-of-flight facility of the Japan Atomic Energy Research Institute electron linac in order to measure more accurate total cross sections in the keV region. Twenty five neutron peaks from 24.3 keV to 1 MeV, which have extremely large signal-to-background ratio of 104, were observed with a 6Li-glass and a plastic scintillator at a 100 m station. The usefulness of the present filtered neutron beam facility was made sure by measuring the total cross section of polyethylene. These values are in excellent agreement with values computed from evaluated data in JENDI-I and ENDF/B-V.

Measurements of 122Sn neutron resonance parameters

Abstract Neutron transmission measurements were carried out on a 122 Sn oxide sample enriched to 92.20% at a 190 m station of the Japan Atomic Energy Research Institute linac with the neutron time-of-flight method. Resonance energies and neutron widths were determined for 21 resonances between 1.5 and 30 keV by a shape analysis code based on the Breit-Wigner multi-level formula. The following average resonance parameters for s-wave neutrons were obtained: D 0 = 1.17 +0.09 −0.08 keV, S 0 × 10 4 = 0.30 +0.12 −0.08 and R ′ = 5.60 ± 0.05 fm. The present s-wave neutron strength function of 122 Sn is substantially larger than the theoretical prediction of the doorway state model.

Neutron resonances in 142Ce

Abstract Neutron transmission and capture measurements have been made on natural cerium and separated isotope 142Ce at the TOF facility of the Japan Atomic Energy Research Institute linear accelerator. Resonance parameters of 142Ce have been newly determined up to 50 keV. The s-wave strength function S0, and average level spacing D0 were deduced to be S0=(2.7±0.6)x10−4, and D0=0.75±0.12 keV. Resonance parameters of N=82 nucleus 140Ce are also determined in the same energy region.