Takeshi Fujiwara

• PhD
• Senior Researcher at National Institute of Advanced Industrial Science and Technology

AISTANS, which is optimized for the Bragg-edge imaging, has been utilized for industrial applications. A second beamline was recently constructed and is under preparation for neutron analysis use. The power of the electron beam, which is used for neutron production at a tantalum target, is currently approximately 1 kW and it is planned to be increa...

The optical and X-and γ-ray induced scintillation characteristics of Tb-doped SrY 2 O 4 single crystals using the floating zone technique were evaluated. Under the UV and X-rays, the several lines in the range of 350 to 650 nm were observed in all the prepared crystals, which were attributed to the Tb ³⁺ ions. In the pulse area spectra of a ¹³⁷ Cs...

The neutron wavelength resolution, Bragg-edge measurement ability and future prospects regarding the neutron count rate were investigated at AISTANS. The wavelength resolution evaluated by Bragg-edge analysis using an iron powder sample is in reasonably good agreement with calculations at neutron wavelengths of 0.2–0.3 nm. Bragg-edge imaging was al...

Radiation plays a significant role in the field of medicine, for example, in radiation therapy and diagnostics. In both applications, accurate radiological imaging techniques are important, and at the same time, a sufficient field of view and high spatial resolution are required, sometimes with high timing resolution. In this paper, we review the d...

Neutron-beam flux spectra at the compact electron accelerator-driven pulsed neutron facility AISTANS were measured at a detector position of 8 m from the neutron source. Based on the measured spectra, the characteristics of the neutron beam from the decoupled ~ 20 K solid methane moderator and the amplification of the neutron-beam flux at the detec...

A quantitative nondestructive Bragg-edge imaging technique for power-storage degradation was developed using commercial prismatic-shaped lithium-ion battery cells. The C or Li atoms/ions column density [cm ⁻² ] images for five phases of the negative electrode material (graphite, Li 0.04 C 6 , Li 0.2 C 6 , Li 0.5 C 6 , and Li 1.0 C 6 ) with a 1 mm s...

Neutron imaging is a powerful tool for observing the internal structure of an object without destroying the object. Neutron imaging (neutron radiography) is a prominent application of neutrons but still requires significant improvements, for example, in sensitivity, resolution, radiation hardness, and handling of neutron imaging detectors. This pap...

An optically read-out glass gas electron multiplier (G-GEM) detector is expected to simplify complicated quality assurance measurements for hadron therapies by imaging the dose distribution of the incident beam. However, the effect of secondary particles from the detector itself has not been well studied. In this paper, we evaluate a design that re...

The use of carbon ion beams in cancer therapy (also known as hadron therapy) is steadily growing worldwide; therefore, the demand for more efficient dosimetry systems is also increasing because daily quality assurance (QA) measurements of hadron radiotherapy is one of the most complex and time consuming tasks. The aim of this study is to develop a...

This article reports initial results of fabricating a tailor-made 3D dosimeter using radiochromic material and a 3D printer. The 3D dose distribution is easily visualized and quantitated as the transparent polymers become colored after irradiation. With this technology, we propose a novel method that uses 3D dosimetry to precisely copy the shape of...

A new electron accelerator has been designed and is now under construction at AIST, Tsukuba, Japan. The accelerator will be used to produce a pulsed neutron beam for materials analysis. The design maximizes the yield of slow neutrons with high pulse temporal resolution as described in a previous publication [K. Kino et al., Nuclear Inst. and Method...

We have constructed a compact accelerator-based neutron facility at the National Institute of Advanced Industrial Science and Technology (AIST) in Japan aiming at development of structural materials of transportation vehicles for weight reduction. The facility consists of electron linear accelerator, neutron source, and a neutron beamline with a me...

We have designed and been constructing a compact accelerator-driven neutron facility for Bragg edge transmission imaging of structural materials to obtain position dependent crystallographic information. In order to combine a high neutron wavelength resolution, which is especially required for strain measurements, and an intense neutron beam flux a...

Large-scale detection is one of the important roles for gaseous detectors to play in high-energy physics. In many cases, energy resolving multi-channel readout is required. Recent micro-pattern gaseous detectors (MPGDs) have finer pitches or pixels; hence, large-sized detectors have thousands of readout channels. In those cases, it becomes importan...

We have developed a Glass Gas Electron Multiplier (Glass GEM, G-GEM), which is composed of two copper electrodes separated by a photosensitive etchable glass substrate having holes arranged in a hexagonal pattern. In this paper, we report the result of imaging using a G-GEM combined with a 2D electronic charge readout. We used a crystallized photos...

A large size x-ray imaging gaseous detector, which has 280 × 280 mm2 effective area has been successfully developed and x-ray imaging has been demonstrated. The imaging system consists of a chamber filled with Ne/CF4 scintillating gas mixture, inside of which Glass GEM (G-GEM) is mounted for gas multiplication. In this system electrons are generate...

This review investigates the advantages and disadvantages of gaseous radiation detectors when compared with solid-state detectors, for use in radiation imaging, which are caused by the differing properties of gases and solids. Imaging applications for which micro-pattern gas detectors (MPGDs) are superior, include neutron imaging, high-linear-energ...

In this study, we propose and demonstrate a novel imaging system, a gaseous flat-panel detector (FPD). The gaseous FPD consists of a glass gas electron multiplier (G-GEM) with a scintillation gas, which is optically coupled with photodiode panel fabricated with liquid crystal display technology. The G-GEM is ideal as a low energy deposition radiati...

A high-spatial-resolution X-ray-imaging gaseous detector has been developed with a single high-gas-gain glass gas electron multiplier (G-GEM), scintillation gas, and optical camera. High-resolution X-ray imaging of soft elements is performed with a spatial resolution of 281 μm rms and an effective area of 100 × 100 mm. In addition, high-resolution...

We have developed a fine-pitch glass gas electron multiplier (G-GEM) for high-resolution X-ray imaging. The fine-pitch G-GEM is made of a 400 μm thick photo-etchable glass substrate with 150 μm pitch holes. It is fabricated using the same wet etching technique as that for the standard G-GEM. In this work, we present the experimental results obtaine...

The glass made gas electron multiplier (GEM) and Ar/CF4-gas-based gaseous detector is developed as a scintillation detector and ultra high photon yield is demonstrated. The light yield of a glass GEM (G-GEM)-based gaseous detector is estimated to be 85,000 photons/keV, which is three orders of magnitude brighter than inorganic scintillators. The ra...

Abstract A photon counting imaging detector system for high energy X-rays is developed for on-site non-destructive testing of thick objects. One-dimensional silicon strip (1 mm pitch) detectors are stacked to form a two-dimensional edge-on module. Each detector is connected to a 48-channel application specific integrated circuit (ASIC). The thresho...

In this study, a new simple neutron imaging gaseous detector was successfully developed by combining a micro-structured ¹⁰B foil, a glass gas electron multiplier (G-GEM), and a mirror–lens–charge-coupled device (CCD)–camera system. The neutron imaging system consists of a chamber filled with Ar/CF4 scintillating gas mixture. Inside this system, the...

We have developed a compact X-ray source using a carbon nanostructure electron emitter and an X-ray imaging camera using a CdTe semiconductor and a pixelated readout circuit for the automated X-ray inspection of metal structures such as industrial pipelines. Both the X-ray source and the detector are compact, lightweight, and battery-driven, operat...

A high-energy X-ray/gamma-ray imaging system based on a hydrogenated amorphous silicon(a-Si:H)/crystalline silicon(c-Si) heterojunction strip detector was developed. The imaging system will be applied in nondestructive testing of concrete structures. We fabricated 50-channel heterojunction strip detectors with a1mm pitch on 500μm thick p-type silic...

An X-band (11.424GHz) electron linac as a neutron source for nuclear data study for the melted fuel debris analysis and nuclear security in Fukushima is under development. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the...

We are developing compact electron linear accelerators (hereafter linac) with high RF (Radio Frequency) frequency (9.3 GHz, wavelength 32.3 mm) of X-band and applying to medicine and non-destructive testing. Especially, potable 950 keV and 3.95 MeV linac X-ray sources have been developed for on-site transmission testing at several industrial plants...

We have developed a new gaseous radiation detector, referred to as the Glass GEM (G-GEM). The G-GEM is composed of a photosensitive etching glass (PEG3) substrate from HOYA Corporation, Japan. Since a large-area detector is required for imaging device applications, we newly developed a large-area G-GEM prototype with a sensitive area of 280×280 mm2...

X-band (11.424 GHz) electron linac as a neutron source for nuclear data study for the Fukushima nuclear plant accident is under development. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the safe settlement of the accident...

We have developed and upgraded portable 950 keV/3.95 MeV X-band (9.3 GHz) linac x-ray sources for on-site nondestructive testing (NDT) for social and industrial infrastructures. We integrated the hardware devices as well as software systems. For the hardware, we established all designed parameters including x-ray intensities of 0.05/2 Gy min−1 at 1...

Here we report the performance of Glass gas electron multipliers (Glass GEMs), which were fabricated with photo-etchable glass. The photo-etchable glass used for substrate is called PEG3 (Hoya Corporation). With this material, we succeeded in fabricating a Glass GEM that was 680 μ m-thick with a hole diameter of 170 μ m and Cr and Cu layer electrod...

Computed tomography system for in situ NDE of degradation bridges is under development, with portable 950 keV/3.95 MeV X-band linac as x-ray source. Collimator is adopted to reduce scattered X-ray noise and 3D model can be built from sectional images so that it becomes possible to evaluate mechanical characters of bridges referring to structural an...

The gas electron multiplier (GEM) is a gaseous detector that is widely used in many applications. Our glass GEM (G-GEM) comprises a photo-etchable glass (PEG3, HOYA Corporation, Japan). Our research indicated that it shows superior performance compared with other gas detectors. In this article, a new type of G-GEM is introduced. It has a guard-ring...

We recently developed glass gas electron multipliers (G-GEMs) with an entirely new process using photo-etchable glass. The photo-etchable glass used for the substrate is called PEG3 (Hoya Corporation). Taking advantage of low outgassing material, we have envisioned a medical application of G-GEMs. A two-dimensional position-sensitive dosimetry syst...

We recently developed a Glass GEM (G-GEM), and it exhibited a superior performance compared with other gaseous detectors. We are currently developing a G-GEM with a single-sided guard ring structure, in order to improve its spark tolerance. In this research, we compared its performance with that of a conventional hole structure. The single-sided gu...

Gas electron multipliers (GEMs) apply the concept of gas amplification inside many tiny holes, realizing robust and high-gain proportional counters. However, the polyimide substrate of GEMs prevents them from being used in sealed detector applications. We have fabricated and tested glass GEMs (G-GEMs) with substrates made of photosensitive glass ma...

In March 2011, there was an accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) and a lot of radionuclides were discharged into the environment, resulting from a powerful earthquake and tsunami. Considering the impact on human health, the radiation dosimetry is the most important for Iodine-131 among radionuclides in the initial stage imm...

We recently developed a Glass GEM (G-GEM), and it exhibited a superior performance. We also developed a G-GEM with a single-sided guard ring structure, in order to improve its spark tolerance. The guard ring G-GEM also showed good performance. The gas gain reached 7,500 with a single G-GEM setup. Energy resolution was 17.3% at maximum, with the col...

We report read out test result of inorganic scintillator; Ce:LiCaAlF 6 single crystal for neutron detection at spallation neutron source. The Ce:LiCaAlF6 crystal is tested in J-PARC spallation neutron source, which is background gamma-ray energy is higher than those from Co-60. Different size and thickness of crystal is tested and with 2 mm cube cr...

We plan to use our X-band (11.424GHz) electron linac as a neutron source for the nuclear analysis for the Fukushima nuclear plant accident. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the safe settlement of the accident...

Here we report new concept of neutron detector with Microstructure Boron Layer. Our new Microstructure Boron Layer is developed to improve the neutron detection efficiency of boron film converter. Microstructure is constructed on aluminum substrate and enriched boron 10 is deposited for 2 to 4 μm thick. The Microstructure were combined with GlassGE...

A Time Over Threshold (TOT) system has advantage over pulse height measurements on its high integrity and low power dissipation because of its binary readout and circuit simplicity. However the relation between TOT and input charge is strongly nonlinear and dynamic range is limited. We propose a new dynamic TOT system which converts the pulse heigh...

Here we report the performance of Glass GEM. Our new GEM is fabricated in totally new process with photo-etch able glass. The glass is called PEG3, the photo-etchabale glass material manufactured by HOYA-PENTAX co. ltd. With this material, we succeed in fabricating a 700μm thick GEM with Cr and Cu layer electrodes. Glass GEMs enable to overcome the...

In March 2011, there was an accident at the Fukushima Daiichi Nuclear Power Plant (NPP) and a discharge of radionuclides resulting from a powerful earthquake. Considering the impact on human health, the radiation dosimetry is the most important for 131I among radionuclides in the initial stage immediately following the release of radionuclides. Sin...

We are developing compact X-band linac X-ray sources for nondestructive evaluation and medicine. First, we develop a portable X-ray system by a 950keV 9.4GHz X-band linac to realize on-site inspection. We use a low power (250kW) magnetron as an RF source for compactness of the whole system. Since the RF power source is quite small and the stored en...

Neutron reflectometry is a powerful method for investigating the surface and interfacial structures of materials in the spatial range from nanometers to sub-micrometers. At the Japan Proton Accelerator Research Complex (J-PARC), a high-intensity pulsed neutron beam is produced with a proton accelerator at 220kW, which will be upgraded to 1MW in fut...

The Time over Threshold (ToT) method [1] is an effective signal processing method for increasing integrity and decreasing power consumption. However ToT suffers from a poor linearity and its dynamic range is limited. We have proposed a new dynamic Time-over-Threshold (dToT) [2] which converts the pulse height into the time width with a dynamically...

We report first read out result of inorganic-organic hybrid scintillator; Ce:LiCaAlF6 single crystal covered with plastic scintillator for neutron detection. The Ce:LiCaAlF6 sample coated with POPOP containing PPO showed great light output and energy resolution than the Ce:LiCaAlF6 itself when it was coupled to PMT. Light output was increased up to...

This paper proposes a novel waveform multiplexing method to realize high channel-density front-end application specific integrated circuit (ASIC) design. In the proposed method, multiplexing is achieved through connecting multiple preamplifiers to a single analog-to-digital converter (ADC). These preamplifiers have different decay time (90%-10%) wh...

Traditional pulse-height-analysis systems suffer from the complexity arising from ADC circuits. In particular, it is difficult to be applied to a large format array of pixilated detectors. Each channel of such an energy resolving multichannel system must be low power consumption and therefore it must be composed of simple circuits. The time-over-th...

A portable X-band (9.3-12GHz) 3.95MeV linear accelerator (linac) ha; been developed for an X-ray nondestructive (NDT) for on-site bridge inspection. Our compact and high energy linac enable; on-site NDT of large structure. In this study, radiographic image of 40cm thick concrete sample were successfully taken with this linac. However, issue with hi...

Pixellated radiation detectors require an energy resolving multichannel system. The time-over-threshold (ToT) method provides an inexpensive way to energy-resolving signal processing. However, the conventional, single-threshold ToT method suffers from a small dynamic range and poor linearity. We have studied linearity in a ToT system for typical sh...

M-MSGC has been successfully fabricated for neutron detector at Japanese spallation neutron source, J-PARC.

a b s t r a c t Conventional MSGCs are made of metal electrodes that might absorb or reflect optical photons. If the electrodes are made of transparent material like ITO, we could take advantage of optical readout. A gas scintillation proportional counter made of ITO MSGC is fabricated and tested where both optical and charge signals are obtained....

Linearity problem has restrained the application of Time-over-Threshold (ToT) on Micro Strip Gas Chamber (MSGC). Here, we proposed an improved ToT method, Dynamic ToT, which could achieve better linearity in a large dynamic range. Both normal ToT and Dynamic ToT module has been assembled with discrete circuits and tested with Multi-Grid MSGC (M-MSG...

A novel waveform multiplexing method has been proposed to implement mixed-signal design in large multichannel front-end electronics systems. By multiplexing analog channels with decay time modulation, this new approach is able to increase readout channels without increasing the number of analog to digital converters and digital circuits. Therefore,...

A spatial computer is a collection of devices filling space whose ability to interact is strongly dependent on their proximity. Previously, we have showed that programming such a computer as a continuous space can allow self-scaling across computers with different device distributions and can increase robustness against device failure. We have exte...

In the environment such as outer space where we cannot maintain the artifacts, it is the robustness that is important for artifacts. Thus the system, which has the information processing circuit realizing self-maintenance function is desirable. So far some approach is tried to realize self-maintenance function using the qualitative reasoning techni...

In the environment such as outer space where we cannot maintain the artifacts, it is the robustness that is important for artifacts. Thus the system which has the information processing circuit realizing self-maintenance function is desirable. So far some approach is tried to realize self-maintenance function using the qualitative reasoning techniq...

In the environment such as outer space where we cannot maintain the artifacts, it is the robustness that is important for artifacts. Thus the system which has the information processing circuit realizing self-maintenance function is desirable, and failure-detector is in need. In this study, we try to implement this failure-detecting function for po...

This paper presents a new network-based concept of real-time plant monitoring based on the wireless sensor network. The wireless sensor network is a novel technology to perform distributed sensing tasks, especially for applications such as environmental monitoring, smart spaces, medical systems and etc. The advances in MEMS technology, sensing tech...