Shingo Taniguchi

Measurement of deep penetration of neutrons produced by 800-MeV proton beam through concrete and iron at ISIS

Abstract A deep penetration experiment through a thick bulk shield was performed at an intense spallation neutron source facility, ISIS, of the Rutherford Appleton Laboratory (RAL), UK. ISIS is an 800 MeV–200 μA proton accelerator facility. Neutrons are produced from a tantalum target, which is shielded with approximately 3-m thick iron and 1-m thick ordinary concrete in the upward direction. On the top of the shield, we measured the neutron flux attenuation through concrete and iron shields which were additionally placed up to 1.2-m and 0.6-m thicknesses, respectively, using the activation detectors of graphite, bismuth, aluminum and the multi-moderator spectrometer inserted indium. The attenuation lengths of concrete and iron for high-energy neutrons above 20 MeV produced at 90° to the proton beam were obtained from the 12 C ( n ,2 n ) 11 C reaction rates of graphite. The neutron spectra through concrete and iron were obtained by the unfolding analysis of the reaction rates of the 12 C ( n ,2 n ) 11 C , 27 Al ( n , α ) 24 Na , 209 Bi ( n ,x n ) 210−x Bi (x=4–10) and 115 In ( n , γ ) 116m In in the energy range of thermal to 400 MeV.

Fast-neutron profiling with an imaging plate

Abstract A method for taking the fast-neutron profile has been developed using an imaging plate combined with a polypropylene converter. By this method, we can obtain the spatial distribution of fast neutrons without any γ-ray contamination by taking the difference between the data with and without the converter. We have studied properties of this method concerning the neutron energy, converter thickness, fading, dynamic range and spatial resolution. Under appropriate conditions, the method has more than a 102 dynamic range with linearity and less than 1.0 mm spatial resolution for 5 and 15 MeV neutrons. By using this method, we successfully obtained a fast-neutron profile after a collimator and radiography of a 5 cm thick iron block.

Characteristics of a phoswich detector to measure the neutron spectrum in a mixed field of neutrons and charged particles

Abstract A phoswich detector composed of NE115 and NE213 scintillators has been developed to distinguish gamma-ray, neutron, and proton events. The detector performance was investigated in a neutron–proton mixed field at National Institute of Radiological Sciences (NIRS), which showed satisfactory particle identification.

Development of multi-moderator neutron spectrometer using a pair of 6Li and 7Li glass scintillators

A multi-moderator spectrometer using a pair of 6Li and 7Li glass scintillators has been developed. This new type of neutron spectrometer can measure the neutron spectrum in a mixed field of neutrons, charged particles and gamma-rays. The particle identification capability was investigated in neutron–gamma-ray and neutron–proton mixed fields and the neutron response functions of the spectrometer were obtained by calculations and experiments up to 200 MeV. This spectrometer has been applied to measure neutron spectrum in a neutron–proton mixed field, produced by bombarding a Be target by 70 MeV protons from the cyclotron.

Neutron Energy and Time-of-flight Spectra Behind the Lateral Shield of a High Energy Electron Accelerator Beam Dump,Part I: Measurements

Neutron energy and time-of-flight spectra were measured behind the lateral shield of the electron beam dump at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were produced by a 28.7 GeV electron beam hitting the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shield. The measurements were performed using a NE213 organic liquid scintillator behind different thicknesses of the concrete shield of 274 cm, 335 cm, and 396 cm, respectively. The neutron energy spectra between 6 and 800 MeV were obtained by unfolding the measured pulse height spectrum with the detector response function. The attenuation length of neutrons in concrete was then derived. The spectra of neutron time-of-flight between beam on dump and neutron detection by NE213 were also measured. The corresponding experimental results were simulated with the FLUKA Monte Carlo code. The experimental results show good agreement with the simulated results.

Neutron energy and time-of-flight spectra behind the lateral shield of a high energy electron accelerator beam dump. Part II: Monte Carlo simulations

Energy spectra of high-energy neutrons and neutron time-of-flight spectra were calculated for the setup of experiment T-454 performed with a NE213 liquid scintillator at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were created by the interaction a 28.7 GeV electron beam in the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shielding. In order to determine the attenuation length of high-energy neutrons additional concrete shielding of various thicknesses was placed outside the existing shielding. The calculations were performed using the FLUKA interaction and transport code. The energy and time-of-flight were recorded for the location of the detector allowing a detailed comparison with the experimental data. A generally good description of the data is achieved adding confidence to the use of FLUKA for the design of shielding for high-energy electron accelerators.

Neutron spectrometry in a mixed field of neutrons and protons with a phoswich neutron detector Part I: response functions for photons and neutrons of the phoswich neutron detector

Abstract We have developed a phoswich neutron detector consisting of an NE213 liquid scintillator surrounded by an NE115 plastic scintillator to distinguish photon and neutron events in a charged-particle mixed field. To obtain the energy spectra by unfolding, the response functions to neutrons and photons were obtained by the experiment and calculation. The response functions to photons were measured with radionuclide sources, and were calculated with the EGS4-PRESTA code. The response functions to neutrons were measured with a white neutron source produced by the bombardment of 135 MeV protons onto a Be+C target using a TOF method, and were calculated with the SCINFUL code, which we revised in order to calculate neutron response functions up to 135 MeV . Based on these experimental and calculated results, response matrices for photons up to 20 MeV and neutrons up to 132 MeV could finally be obtained.

Neutron spectrometry in a mixed field of neutrons and protons with a phoswich neutron detector: Part II: application of the phoswich neutron detector to neutron spectrum measurements

Abstract Using the developed phoswich neutron detector, the neutron energy spectra in a neutron–proton mixed field and in a neutron and heavy-charged-particle mixed field were measured using an unfolding method coupled with the obtained neutron response functions. The photon and proton energy spectra were obtained separately in these mixed fields using the photon response functions and the proton light yield calibration given in the preceding work. The measured spectra were compared with the spectra obtained by the TOF (time-of-flight) method.

Neutron spectrometry in neutron and charged-particle mixed fields with phoswich neutron detector

We have developed the phoswich neutron detector consisting of the NE115 and NE213 scintillators which can distinguish neutron and photon events from charged-particle events. The performance of distinguishing photon and neutron events from charged-particle events was investigated in two neutron and charged-particle mixed fields in NIRS, which gave satisfactory results. In these radiation environments, photon and neutron energy spectra were obtained by the unfolding technique and the evaluated response functions. The proton energy spectra were simultaneously obtained by using the relation between the proton light yield and the incident proton energy.