A project team headed by University of Tsukuba launched the development of a new accelerator based BNCT facility. In the project, we have adopted Radio-Frequency Quadrupole (RFQ)+Drift Tube Linac ...(DTL) type linac as proton accelerators. Proton energy generated from the linac was set to 8MeV and average current was 10mA. The linac tube has been constructed by Mitsubishi Heavy Industry Co. For neutron generator device, beryllium is selected as neutron target material; high intensity neutrons are generated by the reaction with beryllium and the 80kW proton beam.
Our team chose beryllium as the neutron target material. At present beryllium target system is being designed with Monte-Carlo estimations and heat analysis with ANSYS. The neutron generator consists of moderator, collimator and shielding. It is being designed together with the beryllium target system. We also acquired a building in Tokai village; the building has been renovated for use as BNCT treatment facility. It is noteworthy that the linac tube had been installed in the facility in September 2012.
In BNCT procedure, several medical devices are required for BNCT treatment such as treatment planning system, patient positioning device and radiation monitors. Thus these are being developed together with the linac based neutron source. For treatment planning system, we are now developing a new multi-modal Monte-Carlo treatment planning system based on JCDS. The system allows us to perform dose estimation for BNCT as well as particle radiotherapy and X-ray therapy. And the patient positioning device can navigate a patient to irradiation position quickly and properly. Furthermore the device is able to monitor movement of the patient׳s position during irradiation.
•A project team headed by University of Tsukuba launched a development of new accelerator based BNCT facility.•The project adopted an 8MeV RFQ+DTL type linac as proton accelerator.•The linac tube is completed and installed in BNCT facility at Tokai village.•Neutron generator device with beryllium target is being also designed and several medical devices as treatment planning system, patient positioning device are being also developed.•We are now developing a new multi-modal Monte-Carlo treatment planning system based on JCDS.
Abstract
The energy-resolved neutron imaging system, RADEN at J-PARC, has been providing to users a Rietveld-type analysis code, RITS, for pulsed neutron Bragg-edge transmission (BET) imaging with a ...graphical user interface (GUI) version, for fitting spectral data obtained with this instrument. In the last year, we updated the computational platform of GUI-RITS software from Scientific Linux 6 (SL6) and Python 2 to Windows 10 and Python 3, and added some functions to improve usability. The license agreement for this updated software is the Berkeley Software Distribution (BSD) 2-Clause License (non-copyleft) and is currently available for download from the RADEN website.
It should be possible to non-destructively estimate nuclide density by analyzing the transmission dips due to the resonance absorption in neutron transmission spectra. In this study performed at the ...NOBORU instrument in J-PARC/MLF, we evaluated the quality of the neutron resonance transmission measurements and their potential use in the estimation of nuclide density. First, we calculated the emission time distributions of epithermal neutrons by simulation and then fitted the pulse shapes using several kinds of functions to make a response function suitable for the NOBORU instrument. We found that the Cole-Windsor function well reproduced the pulse shape at arbitrary energy. Then, we applied this function to the resonance analysis code REFIT, and found that it was possible to reproduce the resonance shapes. Finally, we performed the transmission measurements at NOBORU and analyzed the resonance dips for Ta, Ag and Cu by the revised REFIT code.
A new pulsed-neutron instrument, named the Energy-Resolved Neutron Imaging System "RADEN", has been constructed at the beam line of BL22 in the Materials and Life Science Experimental Facility (MLF) ...of J-PARC. The primary purpose of this instrument is to perform energy-resolved neutron imaging experiments through the effective utilization of the pulsed nature of the neutron beam, making this the world's first instrument dedicated to pulsed neutron imaging experiments. RADEN was designed to cover a broad energy range: from cold neutrons with energy down to 1.05 meV (or wavelength up to 8.8 Å) with a good wavelength resolution of 0.20% to high-energy neutrons with energy of several tens keV (or wavelength of 10-3 Å). In addition, this instrument is intended to perform state-of-the-art neutron radiography and tomography experiments in Japan. Hence, a maximum beam size of 300 mm square and a high L D value of up to 7500 are provided.
Neutron imaging using pulsed neutron sources coupled with a 2-dimensional position sensitive detector applicable to the time-of-flight method can give information on the crystal texture of coherently ...scattering materials, dynamical information of incoherently scattering materials such as hydrogen, and magnetic field information. Bragg edges appeared at cold neutron region reflect the preferred orientation, crystallite size, and lattice spacing. To deduce such information from the neutron transmission data depending on the position we have developed a data analysis code, and applied this code to data of a welded iron sample. Furthermore, as examples of more realistic materials we have investigated quenched iron rods. The quenched region was clearly demonstrated by the lattice space distribution. Furthermore, difference in the bound state of water or hydrogen in wet and dry cement pastes have been observed by analyzing the gradient of the neutron transmission cross section at the cold neutron region. The magnetic field has been also measured by using the polarized neutrons, and the strength of the field was estimated easily by analyzing the wave length dependent data.
An accelerator based BNCT has been desired because of its therapeutic convenience. However, optimal design of a neutron moderator system is still one of the issues. Therefore, detailed studies on ...materials consisting of the moderator system are necessary to obtain the optimal condition. In this study, the epithermal neutron flux and the RBE dose have been calculated as the indicators to look for optimal materials for the filter and the moderator. As a result, it was found that a combination of MgF2 moderator with Fe filter gave best performance, and the moderator system gave a dose ratio greater than 3 and an epithermal neutron flux over 1.0×109cm−2s−1.
•We performed design study based on RBE estimation for a BNCT moderator system driven by an accelerator.•A moderator system consisting of MgF2 combined with a Fe filter gives the best performance.•The proposed model gives an epithermal neutron flux of more than 1.0×109cm−2s−1 and a dose ratio of 3.07.
One of the most interesting applications of neutron imaging is that it enables the observation of magnetic field. Because the interaction between the neutron spin and the magnetic field depends on ...the neutron energy, it is important to study the neutron energy dependence of magnetic field imaging to quantitatively treat the characteristics of the magnetic field. In this study, we have performed a polarized pulsed neutron imaging experiment using a time-of-flight method at J-PARC and have analyzed the energy dependence of the obtained polarization image. We have also quantitatively analyzed the strength and the direction of the magnetic field relative to the quantized axis inside a solenoid coil.
The sharp variation of neutron attenuation at certain energies specific to particular nuclides (the lower range being from ~1eV up to ~1keV), can be exploited for the remote mapping of element and/or ...isotope distributions, as well as temperature probing, within relatively thick samples. Intense pulsed neutron beam-lines at spallation sources combined with a high spatial, high-timing resolution neutron counting detector, provide a unique opportunity to measure neutron transmission spectra through the time-of-flight technique. We present the results of experiments where spatially resolved neutron resonances were measured, at energies up to 50keV. These experiments were performed with the intense flux low background NOBORU neutron beamline at the J-PARC neutron source and the high timing resolution (~20ns at epithermal neutron energies) and spatial resolution (~55µm) neutron counting detector using microchannel plates coupled to a Timepix electronic readout. Simultaneous element-specific imaging was carried out for several materials, at a spatial resolution of ~150µm. The high timing resolution of our detector combined with the low background beamline, also enabled characterization of the neutron pulse itself – specifically its pulse width, which varies with neutron energy. The results of our measurements are in good agreement with the predicted results for the double pulse structure of the J-PARC facility, which provides two 100ns-wide proton pulses separated by 600ns, broadened by the neutron energy moderation process. Thermal neutron radiography can be conducted simultaneously with resonance transmission spectroscopy, and can reveal the internal structure of the samples. The transmission spectra measured in our experiments demonstrate the feasibility of mapping elemental distributions using this non-destructive technique, for those elements (and in certain cases, specific isotopes), which have resonance energies below a few keV, and with lower resolution for elements with relatively high resonance energies in the 1–30keV range.
We measured the energy spectra and spatial distributions of the neutron beam of Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) at the Japan Proton Accelerator Research ...Complex/Materials and Life Science Experimental Facility (J-PARC/MLF). Our research team designed and built ANNRI to measure nuclear data with high precision. The measurements of the neutron beam were performed on three types of beams provided by ANNRI in the neutron energy range from 1.5
meV to 10
keV. The energy spectra show a typical feature of para-hydrogen moderator, and the absolute intensities almost agree with predictions based on both a simulation calculation of the Japan Spallation Neutron Source (JSNS) and a neutron transmission calculation of the beamline. The available neutron intensities at 21.5
m are 7.5×10
5, 1.6×10
4, and 1.1×10
5
n/cm
2/s in the energy ranges 1.5–25
meV, 0.9–1.1
eV, and 0.9–1.1
keV, respectively, under the 17.5
kW JSNS operation. The measured spatial distributions of the beams formed by three different collimators are consistent with those expected from the collimator-system design of the beamline. The beam sizes in FWHM are about 29, 14, and 11
mm for the three different beam collimators. The edges of the spatial distributions are relatively sharp, enabling us to measure the nuclear data successfully.
The RITS code is a unique and powerful tool for a whole Bragg-edge transmission spectrum fitting analysis. However, it has had two major problems. Therefore, we have proposed methods to overcome ...these problems. The first issue is the difference in the crystallite size values between the diffraction and the Bragg-edge analyses. We found the reason was a different definition of the crystal structure factor. It affects the crystallite size because the crystallite size is deduced from the primary extinction effect which depends on the crystal structure factor. As a result of algorithm change, crystallite sizes obtained by RITS drastically approached to crystallite sizes obtained by Rietveld analyses of diffraction data; from 155% to 110%. The second issue is correction of the effect of background neutrons scattered from a specimen. Through neutron transport simulation studies, we found that the background components consist of forward Bragg scattering, double backward Bragg scattering, and thermal diffuse scattering. RITS with the background correction function which was developed through the simulation studies could well reconstruct various simulated and experimental transmission spectra, but refined crystalline microstructural parameters were often distorted. Finally, it was recommended to reduce the background by improving experimental conditions.
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