We studied the energy resolution of the pulsed neutron beam of the Accurate Neutron–Nucleus Reaction Measurement Instrument (ANNRI) at the Japan Proton Accelerator Research Complex/Materials and Life ...Science Experimental Facility (J-PARC/MLF). A simulation in the energy region from 0.7meV to 1MeV was performed and measurements were made at thermal (0.76−62meV) and epithermal energies (4.8−410eV). The neutron energy resolution of ANNRI determined by the time-of-flight technique depends on the time structure of the neutron pulse. We obtained the neutron energy resolution as a function of the neutron energy by the simulation in the two operation modes of the neutron source: double- and single-bunch modes. In double-bunch mode, the resolution deteriorates above about 10eV because the time structure of the neutron pulse splits into two peaks. The time structures at 13 energy points from measurements in the thermal energy region agree with those of the simulation. In the epithermal energy region, the time structures at 17 energy points were obtained from measurements and agree with those of the simulation. The FWHM values of the time structures by the simulation and measurements were found to be almost consistent. In the single-bunch mode, the energy resolution is better than about 1% between 1meV and 10keV at a neutron source operation of 17.5kW. These results confirm the energy resolution of the pulsed neutron beam produced by the ANNRI beamline.
Targeting improved spatial resolution, a three-dimensional positron-emission-tomography (PET) scanner employing CdTe semiconductor detectors and using depth-of-interaction (DOI) information was ...developed, and its physical performance was evaluated. This PET scanner is the first to use semiconductor detectors dedicated to the human brain and head-and-neck region. Imaging performance of the scanner used for 18 F -fluorodeoxy glucose (FDG) scans of phantoms and human brains was evaluated. The gantry of the scanner has a 35.0-cm-diameter patient port, the trans-axial field of view (FOV) is 31.0 cm, and the axial FOV is 24.6 cm. The energy resolution averaged over all detector channels and timing resolution were 4.1% and 6.8 ns (each in FWHM), respectively. Spatial resolution measured at the center of FOV was 2.3-mm FWHM-which is one of the best resolutions achieved by human PET scanners. Noise-equivalent count ratio (NEC2R) has a maximum in the energy window of 390 to 540 keV and is 36 kcps/Bq/cm 3 at 3.7 kBq/cm 3 . The sensitivity of the system according to NEMA 1994 was 25.9 cps/Bq/cm 3 . Scatter fraction of the scanner is 37% for the energy window of 390 to 540 keV and 23% for 450 to 540 keV. Images of a hot-rod phantom and images of brain glucose metabolism show that the structural accuracy of the images obtained with the semiconductor PET scanner is higher than that possible with a conventional Bismuth Germanium Oxide (BGO) PET scanner. In addition, the developed scanner permits better delineation of the head-and-neck cancer. These results show that the semiconductor PET scanner will play a major role in the upcoming era of personalized medicine.
The pulsed polarized neutron imaging technique was applied to the observation of the domain structure in a grain oriented magnetic steel sheet with an insulating coating. The spontaneous ...magnetization of the steel could be quantitatively evaluated from the period of the oscillatory behavior observed in the wavelength dependent polarization. In addition, a striped domain structure in the demagnetized state and the reversal of the magnetization by an external magnetic field were also confirmed by selecting the appropriate combination of the neutron spin direction for the incident and analyzed beams. The results demonstrate that this method can visualize the distribution of the magnetization in a surface-coated magnetic steel.
We evaluated the accelerator beam power and the neutron-induced radioactivity of 9Be(p, n) boron neutron capture therapy (BNCT) neutron sources having a MgF2, CaF2, or AlF3 moderator and driven by ...protons with energy from 8MeV to 30MeV. The optimal moderator materials were found to be MgF2 for proton energies less than 10MeV because of lower required accelerator beam power and CaF2 for higher proton energies because of lower photon dose rate at the treatment position after neutron irradiation.
•We examined moderators depending on proton energy about accelerator-based sources.•We evaluated γ-dose rate due to neutron-induced radioactivity about the sources.•MgF2 was best for energy less than 10MeV due to a lower accelerator beam power.•CaF2 was best for energy more than 10MeV due to a lower dose at a patient place.
A pulsed neutron transmission coupled with a two-dimensional position sensitive neutron detector gives a time-of-flight spectrum at each pixel of the detector, which depends on the total ...cross-sections of materials. In order to extract quantitative information of the preferred orientation included in the Bragg scattering total cross-section data, a spectral analysis software for the 2D imaging has been developed, and the transmission data of an unbent iron plate were analyzed. The 2D images with respect to the preferred orientation were successfully obtained, and the effectiveness of spectroscopic neutron transmission imaging was indicated.
The residual strain and the total cross-section in Fe plate was investigated by a Bragg-edge transmission method. The experiments were performed at the position of the time-of-flight diffractometer ...at KENS, Sirius. The (Δ
d/
d) reached about 0.1%. The high counting rate and high efficiency pixel type 2d-detector with 8×8 pixels was used. The spatial resolution is about 2.1
mm. We clearly observed the image of the change on Bragg-edge shapes and the strain distribution. The total cross-section around the bending points was larger than other areas but there was no change in the Bragg-edge positions, which would correspond to the change of the microstructure. We obtained the image of residual strain at several points. The values of the residual strain at several lattice planes,
ε
110,
ε
200 and
ε
211, are −263 to 1707
με, −612 to 1665
με and −1205 to 327
με, respectively. It is indicated that the residual strain measurement by the Bragg-edge transmission is not inferior to the high-resolution Bragg diffraction.
Plastically deformed Ge-crystal wafers that have the cylindrical shape with a large curvature were characterized by neutron diffraction. The box-type rocking curve of Bragg reflection with the ...angular width of Γbox≃2° in FWHM, which is observable in the monochromatic neutron diffraction, results in an enhancement in the angle-integrated intensity (Iθ). Besides, Iθ efficiently increases by stacking such Ge wafers. In the course of white neutron diffraction, the reflected-beam width near the focus point becomes sharper than the initial beam width. Further, the dependence of the horizontal beam width on the distance between the sample and detector is quantitatively explained by taking account of the large Γbox, the small mosaic spread of η≃0.1°, and the thickness of the wafers. On the basis of these characterizations, use of plastically deformed Ge wafers as elements for high-luminance neutron monochromator is proposed.
Design study of the imaging beam line at J-PARC MLF, ERNIS Kiyanagi, Y.; Kamiyama, T.; Sato, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2011, Letnik:
651, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We have a plan to build an imaging beam line, Energy-Resolved Neutron Imaging System (ERNIS), at Materials and Life Science Experimental Facility (MLF) at Japan Proton Accelerator Research Complex ...(J-PARC). In pulsed neutron imaging, we use characteristic features of the neutron total cross section, depending on the neutron wavelength, to get sample information such as crystallographic structure and nuclide composition. One of the most important items to be determined for a beam line at J-PARC is the choice of moderator among coupled, decoupled, and poisoned moderators. From the wavelength resolution point of view, we decided to use the decoupled moderator, which could cover major experiments performed at a pulsed neutron source. Here, we discuss the structure of the imaging beam line at beam line 22 of the J-PARC neutron source as well as the arrangement of insertion devices and the experimental area.
We have performed neutron radiography and tomography using a CCD camera-type detector for some test samples at RADEN. The current spatial resolution for neutron radiography is estimated to about ...350μm in the largest field-of-view of 300 × 300 mm2 and 100μm in the field-of-view of 60 × 60 mm2. It is thought that the latter spatial resolution is strongly affected by the image blur in the scintillator screen. In the case of neutron tomography, the current spatial resolution is estimated to be better than 0.5mm using an iron and aluminum test sample. Furthermore, we have performed neutron tomography for a cast aluminum product. As a result, small blowholes are found in the center of the product. This demonstrates the importance of non-destructive testing by neutron radiography and tomography for industrial products.
The phase composition and the microstructure of four ferrous Japanese arrows of the Edo period (17th-19th century) has been determined through two complementary neutron techniques: Position-sensitive ...wavelength-resolved neutron transmission analysis (PS-WRNTA) and time-of-flight neutron diffraction (ToF-ND). Standard ToF-ND technique has been applied by using the INES diffractometer at the ISIS pulsed neutron source in the UK, while the innovative PS-WRNTA one has been performed at the J-PARC neutron source on the BL-10 NOBORU beam line using the high spatial high time resolution neutron imaging detector. With ToF-ND we were able to reach information about the quantitative distribution of the metal and non-metal phases, the texture level, the strain level and the domain size of each of the samples, which are important parameters to gain knowledge about the technological level of the Japanese weapon. Starting from this base of data, the more complex PS-WRNTA has been applied to the same samples. This experimental technique exploits the presence of the so-called Bragg edges, in the time-of-flight spectrum of neutrons transmitted through crystalline materials, to map the microstructural properties of samples. The two techniques are non-invasive and can be easily applied to archaeometry for an accurate microstructure mapping of metal and ceramic artifacts.
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