Kyushu University Academic Staff Educational and Research Activities Database
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Keisuke Maehata Last modified date:2019.05.30



Graduate School
Undergraduate School
Other Organization


E-Mail
Homepage
http://meteor.nucl.kyushu-u.ac.jp
Phone
092-802-3481
Fax
092-802-3483
Academic Degree
Doctor of Engineering
Field of Specialization
Nuclear Engineering, Radiation Physics and Measurements, Cryogenics
Outline Activities
Research:
Development of particle detectors.
Cryogenics and superconducting technology for improvement in performance of such apparatuses as particle detectors, particle accelerators and nuclear fusion reactors.
1. Development of superconducting phase transition edge thermosensor (TES) microcalorimeter for innovative X-ray spectroscopy.
2. Development of dielectric microcalorimeter using quantumpara/ quantumferro electricity.
3. Study on scintillation phenomena in low temperatures
Research
Research Interests
  • Dosimetry of neutron fields with consideration of microscopic biological effects
    keyword : BNCT, accelerator driven neutron field, microscopic biological effects
    2016.04~2020.03.
  • Measurements of transport characteristics of electric charges excited by gamma-rays in TlBr compound semiconductor crystal
    keyword : TlBr compound semiconductor crystal, radiation detector, charge sensitive preamplifier, pulse-shape analysis
    2016.04~2020.03Development of the readout method for scintillation signals emitted from materials by using APDs in low temperature region. Development of new scintillators exhibiting excellent performance in low temperature region..
  • Development of a X-ray EDS system using a TES microcalorimeter performed on a scanning transmission electron microscope
    keyword : TES microcalorimeter, High energy resolution, Energy-dispersive spectroscopy, Transmission electron microscope, Compact dry dilution refrigerator
    2006.04~2019.03.
  • Development of superconducting phase transition edge thermometer (TES) type microcalorimeters for precise spectroscopy of LX-ray photons emitted from transuranium elements.
    keyword : TES, microcalorimeter, plutonium elements, transuranium elements, precise spectroscopy of LX-ray photons
    2005.04~2019.03Development of a microcalorimetor with using superconducting phase transition edge sensor for high precision energy dispersive spectroscopy of LX-rays emitted from transuranium elements such as plutonium..
  • Detection of scintillation photons at low temperatures and development of new type of cryogenic scintillators with excellent performence.
    keyword : scintillator, cryogenic technique
    2001.04~2018.03Development of the readout method for scintillation signals emitted from materials by using APDs in low temperature region. Development of new scintillators exhibiting excellent performance in low temperature region..
  • Development of new type of microcalorimeters with using quantumparaelectric materials
    keyword : quantumparaelectric materials, SrTiO3, microcalorimeter
    1993.04~2019.03Development of new type of microcalorimeters with using strong temperature dependence of the electric capacitance of quantum paraelectric materials in temperatures around 100 mK..
  • Development of liquid helium free 3He-4He dilution refrigerator for particle detectors with excellent energy resolution operating at ultra-low temperatures
    keyword : 3He-4He dilution refrigerator, liquid helium free
    2003.04~2019.03Development of a 3He-4He dilution refrigerator with utilizing a GM cooler for cryogenic particle detectors with a liquid helium free operation..
Academic Activities
Papers
1. Naoko Iyomoto, Ikumi Yoshimine, Yuki Shuto, Takehiro Kuroiwa, Keisuke Maehata, Tasuku Hayashi, Haruka Muramatsu, Kenichiro Nagayoshi, Kazuhisa Mitsuda, Akira Takano, Shota Yoshimoto, Yuta Kurume, Kenji Ishibashi1, Development of Gamma-Ray Transition-Edge-Sensor Microcalorimeters on Thick Membranes, Journal of Nuclear Science and Technology, https://doi.org/10.1007/s10909-018-2100-3, 194, 412-417, 2019.03, We developed transition-edge-sensor microcalorimeters to detect gamma rays of energy up to a few MeV. To develop devices that have mechanical robustness and fast response together with reasonable thermal isolation, we fabricated devices with thick (17 μm or 9.5 μm) membranes using silicon-on-insulator wafers. Here, we report the results for one of each device. The thermal conductances of the 17-μm- thick-membrane device and the 9.5-μm-thick-membrane device were measured to be 84 nW/K and 52 nW/K at their transition temperatures of 162 mK and 202 mK, respec- tively. The thermal conductances are 20–30 times and 6–9 times larger than those of our thin-membrane devices, when compared at the same temperatures. We irradiated the devices with gamma rays from a Cs-137 source. About 30% of the accumulated pulses are signals from the absorbers, while the remaining are signals from the silicon substrates. The energy resolution of the 662-keV photo peak for the 17-μm-thick- membrane device is 2.2 keV, whereas the baseline energy resolution is 2.3 keV. The energy resolution is several times worse than the design value. One reason for the degradation of the energy resolution is the low-frequency noise of the mechanical cooler, and the other reason is the thermal noise arising from the Compton-scattering events in the substrate..
2. Shota Yoshimoto, Maehata Keisuke, Iyomoto Naoko, Mitsuda Kazuhisa, Yamasaki Noriko, Dielectric microcalorimeter utilizing a quantum ferroelectric thermometer, Journal of Nuclear Science and Technology, https://doi.org/10.1007/s10909-018-2066-1, 194, 418-425, 2019.03, A dielectric capacitance thermometer was fabricated using KTa0.99 Nb0.01 O3 (KTN) quantum ferro- electrics. The electric capacitance of the KTN thermometer was measured as a function of tem- perature from 0.1 to 300 K using the four-terminal-pair method. The KTN thermometer exhibited a dependence of the electric capacitance on the temperature that showed promise for using the thermometer as a microcalorimeter. A prototype of the dielectric microcalorimeter (DMC) was assembled with the KTN thermometer and irradiated with alpha rays with an energy of 5.5 MeV at a temperature of 100 mK. When applying a DC bias voltage to the DMC, the detection signals could be observed at the output of the preamplifier. A response of the DMC to alpha rays was obtained despite the poor signal-to-noise ratio caused by long wirings for the detection signal readout inside the refrigerator..
3. Keisuke Nakamura, Keisuke Maehata, Tetsuya Sugimoto, Yu Kiguchi, Naoko Iyomoto, Yuki Morishita, Koji Takasaki and Kazuhisa Mitsuda, Spectroscopic measurements of L X rays using a transition-edge sensor microcalorimeter for nondestructive analysis of transuranium elements, Progress in Nuclear Science and Technology, Proceedings of ISORD-9, 10.15669/pnst.6.8, 6, 8-12, 2019.01, The TES microcalorimeter was employed for spectroscopic measurements of L X rays emitted from 237Np, 239Pu, 241Am and 244Cm sources of typical transuranium (TRU) elements. Peaks of major L X rays of TRU elements were clearly identified in experimental energy spectra. The feasibility was considered for a nonde- structive analysis of TRU elements based on experimental L X ray spectra measured by the TES microcalorimter..
4. Riichiro NAKAMURA, Keisuke MAEHATA, Nobihiro SHIGYO, Naoko IYOMOTO, Hiroki TANAKA, Evaluation of Biological Effect in Neutron Field Generated by an Accelerator Using PHITS Code with Microdosimetric Kinetic Model, JPS Conference Proceedings, Proceedings of the Second International Symposium on Radiation Detectors and Their Uses (ISRD2018), https://doi.org/10.7566/JPSCP.24.011026, 24, 011026, 2019.01, We are investigating evaluation of radiation biological effectiveness in an accelerator driven boron neutron capture therapy with considering microscopic energy deposition. In this study, we estimated cell survival fraction in a simulated neutron field for Boron Neutron Capture Therapy (BNCT) in a case of operating Fixed Field Alternating Gradient (FFAG) accelerator at Kyushu University with using the Particle and Heavy Ion Transport code System (PHITS) coupled with Microdosimetric Kinetic (MK) model..
5. S. Ezaki, K. Maehata, N. Iyomoto, T. Asano,3 and B. Shinozaki, Vortex dynamics in superconducting transition edge sensors, JOURNAL OF APPLIED PHYSICS, 10.1063/1.5013624, 123, 084504, 2018.02, The temperature dependence of the electrical resistance (R-T) and the current-voltage (I-V) charac- teristics has been measured and analyzed in a 40 nm thick Ti thin film, which is used as a transition edge sensor (TES). The analyses of the I-V characteristics with the vortex-antivortex pair dissocia- tion model indicate the possible existence of the Berezinskii-Kosterlitz-Thouless (BKT) transition in two-dimensional superconducting Ti thin films. We investigated the noise due to the vortices’ flow in TESs. The values of the current noise spectral density in the TESs were estimated by employing the vortex dynamics caused by the BKT transition in the Ti thin films. The estimated values of the current noise spectral density induced by the vortices’ flow were in respectable agree- ment with the values of excess noise experimentally observed in the TESs with Ti/Au bilayer..
6. Akira Takano, Keisuke Maehata, Naoko Iyomoto, Toru Hara, Kazuhisa Mitsuda, Noriko Yamasaki, Keiichi Tanaka, Simulation model of transmitted X-rays in polycapillary optics for TES microcalorimeter EDS system on scanning transmission electron microscope, IEEE Transactions on Nuclear Science, 10.1109/TNS.2017.2786703, 65, 2, 758-765, 2018.02, We created a simple simulation model of transmitted X-rays in polycapillary optics for improved understanding of the transmission characteristics and to aid in the design of the geometrical parameters of the polycapillary optics. New polycapillary optics for a 64-pixel array transition-edge sensor (TES) microcalorimeter energy dispersive spectrometer (EDS) system that was installed in a scanning transmission electron microscope (STEM) were developed using the simulation model. The characteristic X-rays that are emitted from the STEM specimen were transmitted and focused on the pixel array TES microcalorimeter by the polycapillary optics. The experimental X-ray transmission characteristics of the manufactured polycapillary optics agreed with the simulated results..
7. Akira Takano, Keisuke Maehata, Naoko Iyomoto, Toru Hara, Kazuhisa Mitsuda, Noriko Yamasaki, Keiichi Tanaka, DEVELOPMENT OF POLYCAPILLARY OPTICS FOR A SCANNING TRANSMISSION ELECTRON MICROSCOPE - TRANSITION EDGE SENSOR MICROCALORIMETER - ENERGY DISPERSIVE SPECTROMETER (STEM-TES-EDS), Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2017-9, 19-26, 2017.12.
8. Haruka Muramatsu, Tasuku Hayashi, Keisei Maehisa, Yuki Nakashima, Kazuhisa Mitsuda, Noriko Y. Yamasaki, Toru Hara, and Keisuke Maehata, A Study of X-Ray Response of the TES X-Ray Microcalorimeter for STEM, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2017.2661738, 27, 4, 2101204-2101204, 2101204, 2017.07, TES microcalorimeters show a nonlinear pulse- height-to-energy relation, reflecting their nonlinear resistance- to-temperature relation on the transition edge. In some of TES applications, such as energy dispersive X-ray spectroscopy, a wide energy range (e.g. 0.5–15 keV) and a good energy calibration (e.g. within a few eV) are required. We have studied the method to cali- brate the nonlinear pulse-height-to-energy and to correct for it in the data analysis. We irradiated a TES microcalorimeter with three radio isotopes simultaneously to obtain continuum-free line spectra covering from 3.3 to 17.8 keV. X-ray lines from those isotopes are, respectively, a line complex containing fine structures and/or satel- lite lines, which cannot be fully separated with TES microcalorime- ters. Thus, a special treatment is necessary. We first established a method to estimate the relation between PHA (pulse height ana- lyzed value by optimum filtering) and X-ray energy of the line com- plex precisely: we assumed that the relation could be approximated with a linear function, PHA = aE + b, locally in the narrow en- ergy range containing one of the line complex, and determined a and b from the model fit of the PHA spectrum of the line com- plex. Then, from the PHA-to-energy relations of six line complexes, we determined an approximation formula which represented the global PH-to-energy relation. We then applied the global relation to convert PHA values of all pulses to energy equivalent value, which we call PI (pulse invariant). We then fitted the PI spectra with the model function to check the consistency of energy. We have done these processes starting from two different forms of data; TES cur- rent as a function of time, and TES resistance as a function of time. The nonlinearity of PHA-to-energy was smaller for TES resistance pulses, and a better energy calibration is obtained. We found that the PI spectra obtained from TES resistance pulses reproduced the X-ray energies within ±3 eV uncertainty, while the uncertainties becomes as large as 10 eV for the PI spectra obtained from TES current pulses..
9. A. Takano, K. Maehata, Naoko IYOMOTO, T. Hara, K. Mitsuda, N. Yamasaki, K. Tanaka, Characterization of Polycapillary Optics Installed in an Analytical Electron Microscope, Proceedings of International Symposium on Radiation Detectors and Their Uses (ISRD2016), JPS Conference Proceedings, https://doi.org/10.7566/JPSCP.11.030003, 11, 030003, 2016.11.
10. K. Maehata, Superconducting Radiation Detectors, Proceedings of International Symposium on Radiation Detectors and Their Uses (ISRD2016), JPS Conference Proceedings, https://doi.org/10.7566/JPSCP.11.010004, 11, 010004, 2016.11.
11. T. Sugimoto, K. Maehata, Naoko IYOMOTO, KENJI ISHIBASHI, K. Nakamura, M. Maeda, K. Takasaki, K. Mitsuda, Spectroscopic Measurement of Pu L X-rays emitted by 244Cm Source with a TES Microcalorimeter, Proceedings of International Symposium on Radiation Detectors and Their Uses (ISRD2016), JPS Conference Proceedings, https://doi.org/10.7566/JPSCP.11.030001, 11, 030001, 2016.11.
12. Shota Yoshimoto, K. Maehata, K. Mitsuda, Y. Yamanaka, K. Sakai, K. Nagayoshi, R. Yamamoto, T. Hayashi, H. Muramatsu, Characterization System of Multi-pixel Array TES Microcalorimeter, Proceedings of International Symposium on Radiation Detectors and Their Uses (ISRD2016), JPS Conference Proceedings, https://doi.org/10.7566/JPSCP.11.010002, 11, 010002, 2016.11.
13. A. Takano, K. Maehata, K. Maehata, kazuhiro Yasuda, H. Maeno, K. Shiiyama, K. Tanaka, Characterization of Polycapirally Optics in a TES Microcalorimeter EDS System Installed on an SEM, Journal of Low Temperature Physics, 10.1007/s10909-015-1350-6, 184, 832-838, 2016.06, Energy-dispersive spectroscopic measurements are performed using a superconducting transition-edge sensor (TES) microcalorimeter mounted on a scanning electron microscope (SEM) for advanced research atKyushu University. Because the sensitive area of the TES microcalorimeter is about 0.02 mm2, polycapillary optics is used to collect the X-rays emitted by the SEM specimen on the TES microcalorimeter. The X-ray transmission efficiency of the polycapillary optics is obtained by analyzing the X-ray energy spectra measured by the TES microcalorimeter. The obtained transmission efficiency of the polycapillary optics is reproduced by the calculated results of the simulation..
14. K. Maehata, T. Hara, K. Mitsuda, M. Hidaka, K. Tanaka, Y. Yamanaka, A Transition Edge Sensor Microcalorimeter System for the Energy Dispersive Spectroscopy Performed on a Scanning-Transmission Electron Microscope, Journal of Low Temperature Physics, DOI 10.1007/s10909-015-1361-3, 184, 5-10, 2016.05, We are conducting the development of a transition edge sensor (TES) microcalorimeter system for energy-dispersive X-ray spectroscopy (EDS), performed
using a scanning-transmission electron microscope (STEM). The operating temperature of the TES microcalorimeter was maintained using a compact dry 3He-4He
dilution refrigerator. This was pre-cooled by a remote helium cooling loop system and a Gifford-McMahon cooler. These conditions allowed for high-resolution STEM
imaging to be achieved. A single-pixel TES microcalorimeter with a polycapillary optic was selected to demonstrate the analytical operation of the EDS system in the
STEM. For a Ti-It-Pt sample, an X-ray energy resolution of 8.6 eV full-width at half maximum (FWHM) was obtained at Ir Mα1, Pt Mα1, and Ir Mβ. Using an electron
device sample, element distribution maps of Si, Ti, and W were obtained using a Si Kα1 X-ray energy resolution of 9.7 eV FWHM..
15. Naoko IYOMOTO, Hisao Kawakami, K. Maehata, Ikumi Yoshimine, Yuki Shuto, Kenichiro Nagayoshi, Kazuhisa Mitsuda, Shohei Esaki, Akira Takano, Shota Yoshimoto, KENJI ISHIBASHI, Gamma-Ray Transition-Edge Sensor Microcalorimeters on Solid Substrates, Journal of Low Temperature Physics, DOI 10.1007/s10909-016-1538-4, 184, 82-87, 2016.05.
16. Haruka Muramatsu, K. Nagayoshi, T. Hayashi, K. Sakai, R. Yamamoto, K. Mitsuda, N. Y. Yamasaki, K. Maehata, T. Hara, Design and Performance of a TES X-ray Microcalorimeter Array for Energy Dispersive Spectroscopy on Scanning Transmission Electron Microscope, Journal of Low Temperature Physics, DOI 10.1007/s10909-016-1547-3, 184, 91-96, 2016.05.
17. R. Yamamoto, K. Sakai, K. Maehisa, K. Nagayoshi, T. Hayashi, H. Muramatsu, Y. Nakashima, K. Mitsuda, N. Y. Yamasaki, Y. Takei, M. Hidaka, S. Nagasawa, K. Maehata, T. Hara, Common Bias Readout for TES Array on Scanning Transmission Electron Microscope, Journal of Low Temperature Physics, DOI 10.1007/s10909-016-1562-4, 184, 454-459, 2016.05.
18. A. Takano, K. Maehata, N. IYOMOTO, K Yasuda, H. Maeno, K. Shiiyama, K. Tanaka, Characterization of TES microcalorimeter EDS system on a SEM, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2015-8, 28-37, 2016.01.
19. A. Takano, K. Maehata, N. IYOMOTO, T. Hara, K. Mitsuda, N. Y. Yamazaki, K. Tanaka, X-Ray Transmission Characteristic Measurements of Polycapillary Optics Installed in an Analytical Electron Microscope, IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 10.1109/TNS.2015.2453011, 62, 4, 1918-1922, 2015.08, This paper studies the polycapillary optics that are used to focus and transmit the X-rays emitted by a transmission electron microscope (TEM) specimen to an energy dispersive spectrometer using a superconducting transition edge sensor (TES) microcalorimeter. In this study, X-rays are collected from a TEM specimen and are then focused on a silicon drift detector, from which energy spectrum measurements of the polycapillary optics are taken and used to determine the transmission characteristics of the optics. When the polycapillary optics are used, an increase of 25.9 is seen in the intensity of 4.6 keV X-rays, while an increase of 6.0 is seen for 12.6 keV X-rays. The focal spot sizes of the X-ray beams from the polycapillary optics are found to be 382 um for the 4.6 keV X-rays and 156 um for the 12.6 keV X-rays. Further improvement of these characteristics can be achieved by improving the alignment of the optics to the detector and the collimator, which immediately precedes the detector, and by optimizing the collimator width..
20. S. Ezaki, K. Maehata, N. IYOMOTO, M. Maeda, T. Hara, K. Mitsua, K. Tanaka, X-Ray Response of a Transition Edge Sensor Microcalorimeter with a Mushroom-Shaped Absorber, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2014.2377113, 25, 3, 2100904, 2015.06.
21. M. Maeda, K. Maehata, N. IYOMOTO, K. ISHIBASHI, K Takasaki, K. Nakamura, K. Aoki, K. Mitsuda, K Tanaka, Y. Yamanaka, Peak identification of L X-ray spectra of elemental Np and U, Journal of Nuclear Science and Technology, 10.1080/00223131.2014.957744, 52, 4, 509-513, 2015.04, The L X-ray photons emitted by transuranic (TRU) elements are expected to be useful for developing nondestructive TRU monitors. Energy spectra of L X-rays emitted by 241Am, 238Pu and 239Pu sources were measured by a transition edge sensor (TES) microcalorimeter, which allowed precise peak identification with high energy resolution. In the measurements using the TES microcalorimeter, the full width at half maximum energy resolution was 62.6 eV at 17.222 keV for 239Pu source, 62.5 eV at 17.222 keV for 238Pu source and 60.9 eV at 17.751 keV for 241Am source. This study demonstrates the separation of 241Am and plutonium isotopes by L X-ray spectroscopy using a TES microcalorimeter..
22. K. Maehata, N. IYOMOTO, Y. Yamanaka, T. Ito, T. Hara, K. Mitsuda, N. Y. Yamaaaki, K. Tanaka, Development of compact dry 3He-4He dilution refrigerator for transition edge sensor microcalorimeter X-ray detector operation on electron microscopes, Journal of Superconductivity and Novel Magnetism, 10.1007/s10948-014-2699-5, 28, 3, 1161-1165, 2015.03.
23. K. Maehata, M. Maeda, N. IYOMOTO, K. ISHIBASHI, K. Nakamura, K. Aoki, K. Takasaki, K. Mitsuda, K. Tanaka, Response of a Superconducting Transition-Edge Sensor Microcalorimeter with a Mushroom-shaped Absorber to L X-rays Emitted by Transuranium Elements, IEICE Transactions on Electronics, 10.1587/Transele.E98.C.178, E98-C, 3, 178-185, 2015.03, A four-pixel-array superconducting transition-edge sensor (TES) microcalorimeter with a mushroom-shaped absorber was fabricated for the energy dispersive spectroscopy performed on a transmission electron microscope. The TES consists of a bilayer of Au/Ti with either a 50-nm or 120-nm thickness. The absorber of 5.0 ${\mu}$m thick is made from a Au layer and its stem is deposited in the center of the TES surface. A Ta${_{2}}$O${_{5}}$ insulating layer of 100-nm thickness is inserted between the overhang region of the absorber and the TES surface. A selected pixel of the TES microcalorimeter was operated for the detection of Np L X-rays emitted from an ${^{241}}$Am source. A response of the TES microcalorimeter to L X-rays was obtained by analyzing detection signal pulses with using the optimal filter method. An energy resolution was obtained to be 33 eV of the full width at half maximum value at 17.751 keV of Np L${_{\beta1}}$ considering its natural width of 13.4 eV. Response to L X-rays emitted from a mixture source of ${^{238}}$Pu, ${^{239}}$Pu and ${^{241}}$Am was obtained by operating the selected pixel of the TES microcalorimeter. Major L X-ray peaks of progeny elements of ${\alpha}$ decay of Pu and Am isotopes were clearly identified in the obtained energy spectrum. The experimental results demonstrated the separation of ${^{241}}$Am and plutonium isotopes by L X-ray spectroscopy..
24. A. Takano, K. Maehata, N. IYOMOTO, T. Hara, K. Mitsda, N. Y. Yamazaki, X-RAY TRANSMISSION CHARACTERISTICS MEASUREMENT OF A POLYCAPILLARY LENS INSTALLED IN AN ANALYTICAL ELECTRON MICROSCOPE, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2014-11, 52-61, 2015.01.
25. S. Ezaki, M. Maeda, N. IYOMOTO, K. Maehata, T. Hara, K. Mitsuda, N. Y. Yamaaaki, K. Tanaka, Y. Yamanaka, T. Ito, THE X-RAY RESPONSES AND CHARACTERIZATIONS OF THE TES MICROCALORIMATERS WITH MUSHROOM SHAPED ABSORBER, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2014-11, 34-43, 2015.01.
26. M. Maeda, K. Maehata, N. IYOMOTO, K. ISHIBASHI, K. Takasaki, K. Aoki, K. Mitsuda, K. Tanaka, Spectroscopic Measurement of L X-rays Emitted by Transuranium Elements by Using TES Microcalorimeter, Journal of Low Temperature Physics, DOI 10.1007/s10909-013-1012-5, 176, 1046-1052, 2014.09, Energy spectra of L X-rays emitted by 237Np and uranium isotopes progenies of 241Am and plutonium isotopes were measured by a transition edge sensor (TES) microcalorimeter for demonstration of peak separation with high energy resolution. L X-ray photons emitted by transuranium (TRU) elements can to be utilized for a nondestructive TRU monitor. Major L X-ray peaks are clearly distinguished in the energy spectrum of L X-rays obtained by the simultaneous measurement for radiation sources of 241Am and plutonium isotopes. The value of full width at half maximum energy resolution is 60.21 eV for a peak corresponding to Np Lβ1 X -rays of 17.751 keV in 241Am source measurement. Comparable energy resolutions were obtained in other experiments. This measurement demonstrated separation of 241Am
and plutonium isotopes by L X-ray spectroscopy using TES microcalorimeter..
27. K. Maehata, N. Iyomoto, M. Maeda, S. Ezaki, A. Takano, S. Matsumura, T. Hara, K. Mitsuda, N. Y. Yamasaki, K. Tanaka, Development of 4-Pixel-Array TES Microcalorimeters with Mushroom-Shaped Absorbers with Insulating Layers Supporting Overhang Regions, Journal of Low Temperature Physics, DOI 10.1007/s10909-014-1113-9, 176, 578-583, 2014.08, A four-pixel-array superconducting transition-edge sensor (TES) micro calorimeter with a mushroom-shaped absorber was developed for energy dispersive spectroscopy performed on a transmission electron microscope. The TES consists of a bilayer of Au/Ti with either a 120- or 50-nm thickness. The absorber is made from a Au layer and its stem is deposited in the center of the TES surface. A Ta2O5 insulating layer of 100-nm thickness is inserted between the overhang region of the absorber and the TES surface. Two types of microcalorimeter were fabricated with differing absorber thicknesses of 0.5 and 5.0 μm. An energy resolution of 15 eV FWHM with 5.9-keV X-rays was obtained using the 0.5-μm-type microcalorimeter..
28. K. Maehata, T. Hara, T. Ito, Y. Yamanaka, K. Tanaka, K. Mitsuda, N. Y. Yamasaki, A dry 3He–4He dilution refrigerator for a transition edge sensor microcalorimeter spectrometer system mounted on a transmission electron microscope, Cryogenics, 61, 86-91, 2014.05, A dry 3He–4He dilution refrigerator (DR) was developed for a superconducting transition edge sensor (TES) microcalorimeter installed on a transmission electron microscope. This system could be used for energy dispersive X-ray spectroscopy (EDS) with an excellent energy resolution. A Gifford–McMahon (GM)-type mechanical cryocooler was used as a pre-cooler for the DR to ensure liquid helium was not consumed during operation. To reduce sound and vibrations generated by the GM cryocooler, the DR was separated from the GM cryocooler in a split system. The TES microcalorimeter was glued onto the top of a copper rod referred to as the snout, which was attached to the mixing chamber of the DR. The cooling power in the mixing chamber was 30 lW at 105 mK. The lowest temperature in the mixing chamber was 74 mK, and that at top of the snout was 86 mK. An energy resolution of 7.6 eV full width at half maximum for Si Ka X-rays of 1.74 keV was obtained by TES microcalorimeter EDS performed with the transmission electron microscope..
29. Shohei Ezaki, Keisuke Maehata, Naoko IYOMOTO, Syo Matsumura, Kenichiro Nagayoshi, Kazuhisa Mitsuda, Noriko Yamasaki, Yoh Takei, Toru Hara, Keiichi Tanaka, DESIGN AND FABRICATION OF THE MULTI-PIXEL TES MICROCALORIMETER WITH A MUSHROOM SHAPED ABSORBER FOR X-RAY DETECTION, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2013-9. pp.72-80, 2014.01.
30. Makoto Maeda, Keisuke Maehata, Naoko IYOMOTO, Kenji ISHIBASHI, Koji Takasaki, Keisuke Nakamura, Katsunori Aoki, Kazuhisa Mitsuda, Keiichi Tanaka, SPECTROSCOPIC MEASUREMENT OF L X-RAYS EMITTED BY TRANSURANIUM ELEMENTS BY TES MICROCALORIMETER, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2013-9. pp.63-71, 2014.01.
31. T. Yasumune, M. Kurihara, K. Maehata, K. ISHIBASHI, A. Yoshikawa, Scintillation properties of Yb3+-doped YAlO3 in the temperature range from 4.2 to 175 K, Nuclear Instruments and Methods in Physics Research A, 726, 37-40, 2013.09, We measured the temperature dependence of the emission wavelength spectrum of YAP:Yb by irradiating with βrays from a 90Sr/90Y source in the temperature range from 4.2 to 175 K. The light yield of YAP:Yb was characterized using an avalanche photodiode in the detection of 662-keV γrays from a 137Cs source in the temperature range from 50 to 175 K. The light yield was found to increase with decreasing temperature and reached 3840 photons/MeV at a temperature of 50 K. By extrapolating the temperature dependence of the light yield using that of the integrated emission spectra, the experi- mental light yield was evaluated to be 4300 photons/MeV at a temperature of 4.2 K..
32. Keisuke Maehata, Naoko Iyomoto, Syo Matsumura, Yoshihiro Yamanaka, Takuji Ito, Toru Hara, Kazuhisa Mitsuda, Noriko Yamasaki, Keiichi Tanaka, Development of a compact dry 3He-4He dilution refrigerator for a TES microcalorimeter X-ray spectrometer for analytical transmission electron microscopy, Proceedings of the Twenty-Fourth International Cryogenic Engineering Conference and International Cryogenic Materials Conference 2012, p.235-238, 2013.03.
33. Sekiya N., Yamasaki N. Y., Mitsuda K., Kawasaki S., Takei Y., Sakai K., Sato K., Maehata K., and Takashima H., Development of dielectric X-ray microcalorimeter, Proceedings of the Twenty-Fourth International Cryogenic Engineering Conference and International Cryogenic Materials Conference 2012, p.215-218, 2013.03.
34. Takashi Yasumune, Keisuke Maehata, Masakazu Kurihara, Naoko Iyomoto, Kenji Ishibashi, Akira Yoshikawa, SCINTILLATION RESPONSE OF YAP:Yb CRYSTAL TO γ RAYS IN CRYOGENIC TEMPERATURES, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2012-8. p.128-133, 2012.12.
35. Makoto Maeda, Takashi Yasumune, Naoko Iyomoto, Keisuke Maehata, Toru Hara, Kazuhisa Mitsuda, Noriko Yamasaki, Keiichi Tanaka, Yoshihiro Yamanaka, Takuji Ito, RESPONSE CHARACTERISTICS OF TES MICROCALORIMETERS WITH DIFFERENT ABSORBER STRUCTURE, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2012-8. p.66-73, 2012.12.
36. Makoto Maeda, Kazuya Yamaguchi, Keisuke Maehata, Naoko Iyomoto, Kenji Ishibashi, Koji Takasaki, Keisuke Nakamura, Keiichi Tanaka, Yoshihiro Yamanaka, Spectroscopic Measurement of L X-Rays Emitted by 241Am Source by TES Microcalorimeter, Journal of Low Temperature Physics, 167, 754-758, 2012.02.
37. Keisuke Maehata , Naoko Iyomoto, Takashi Yasumune, Makoto Maeda, Syo Matsumura, Toru Hara, Kazuhisa Mitsuda, Noriko Yamasaki, Keiichi Tanaka, Development of a TES Microcalorimeter with a Mushroom Shaped Absorber Deposited on an Insulating Layer in an Overhang Region, Journal of Low Temperature Physics, 167, 226-231, 2012.02.
38. Takashi Yasumune, Masakazu Kurihara, Keisuke Maehata, Naoko Iyomoto, Kenji Ishibashi, Scintillation Properties of 6LiI(Eu) in Cryogenic Temperatures, Journal of Low Temperature Physics, 167, 442-446, 2012.02.
39. Keisuke Maehata, Toru Hara, Keiichi Tanaka, Kazuhisa Mitsuda, Noriko Y. Yamasaki, Mitsuaki Ohsaki, Shigemasa Ohta, Takuji Itoh and Yoshihiro Yamanaka, DEVELOPMENT OF TES MICROCALORIMETER ENERGY DISPERSIVE SPECTROSCOPY SYSTEM ON A TRANSMISSION ELECTRON MICROSCOPE, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2011-8. p.1-10, 2011.12.
40. Keisuke Maehata, Kazuya Idemitsu and Keiichi Tanaka, ENERGY DISPERSIVE X-RAY SPECTROSCOPY OF URANIUM ORE BY TES MICROCALORIMETER PERFORMED WITH SCANNING ELECTRON MICROSCOPE, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2011-8. p.11-16, 2011.12.
41. Makoto Maeda, Keisuke Maehata, Kenji Ishibashi, Koji Takasaki, Keisuke Nakamura, Keiichi Tanaka and Takahiro Umeno, SPECTROSCOPIC MEASUREMENT OF 214Am LX-RAYS BY TES MICROCALORIMETER, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2011-8. p.17-25, 2011.12.
42. Keisuke Maehata, Kazuya Idemitsu and Keiich Tanaka, X-ray Energy Dispersive Spectroscopy of Uranium Ore using a TES Microcalorimeter Mounted on a Field-Emission Scanning Electron Microscope, Nuclear Inst. and Methods in Physics Research, , A648 , 285–289, 2011.08, A phase transition edge sensor (TES) microcalorimeter was developed for the energy-dispersive measurement of LX-ray photons emitted by transuranium elements. The phase transition temperature of the TES was designed to be 200 mK using a bilayer structure of Au of 120 nm thickness and Ti of 50 nm thickness. A Au layer of 5.0 mm thickness was deposited on the Au/Ti bilayer to achieve an absorption efficiency of 50% and counting rate of 100 counts per second in the detection of LX-ray photons with energy from 10 to 20 keV. The TES microcalorimeter was operated for the detection of LX-ray photons emitted by 241Am, 238Pu, and 239Pu sources. A decay time constant of 180 ms for the detection signal pulses allowed the TES microcalorimeter to operate with a counting rate higher than 100 counts per second. The achieved energy resolution was 50 eV for the full width at half maximum of a peak corresponding to a 237Np L.
43. Takashi Yasumune, Takuro Masuda, Yuki Oshima, Keisuke Maehata, Kenji Ishibashi, and Takahiro Umeno, Measurement of Output Signals from an Avalanche Photodiode by Irradiating with X-rays in the Temperature Range from 150 mK to 4.2 K, Japanese Journal of Applied Physics, 50, 7, 072201(4ページ), 2011.07, We measured leakage current and gain characteristics of a reverse-type avalanche photodiode (APD). The leakage current generated below the breakdown voltage was found to be lower than 1pA at temperatures below 200K. Avalanche multiplication of the APD was achieved in the temperature range from 150 mK to 300 K. To characterize charge carrier properties of the APD, output signal pulses from the APD were observed by irradiating the APD with X-rays in the temperature range from 150 mK to 4.2 K. The yield of signal charge was found to abruptly change in the temperature range from 1 to 2 K, where the yield of charge at 1 K is about 50% of that at 2 K. # 2011 The Japan Society of Applied Physics.
44. Keisuke Nakamura, Makoto Maeda, Takashi Yasumune, Keisuke Maehata, Kenji Ishibashi, Keiichi Tanaka, Takahiro Umeno, Koji Takasaki and Takumaro Momose , DEVELOPMENT OF A MICROCALORIMETER WITH TRANSITION EDGE SENSOR FOR DETECTION OF LX
RAYS EMITTED BY TRANSURANIUM ELEMENTS, Radiation Protection Dosimetry, 146, 1-3, 88-91, 2011.04, A transition edge sensor (TES) microcalorimeter has been developed for use as an energy dispersive X-ray spectrometer. The TES microcalorimeter is a thermal detector that enables one to determine the energy of an incident photon by
measuring the resultant increase in temperature. In this work, a Ti/Au TES microcalorimeter was developed to measure LX rays emitted by transuranium elements. The phase transition temperature was set at ∼200 mK by using a bilayer
structure composed of a 110-nm-thick Au layer and a 40-nm-thick Ti layer. An Au of 5 mm thickness was deposited on the Ti/Au bilayer to achieve an absorption efficiency of 35–80 % for the energy range of LX rays (10–25 keV).
The developed TES microcalorimeter was irradiated with LX rays emitted by an 241Am source at an operating temperature of 140 mK. An energy resolution of ∼80 eV (full width at the half maximum) was obtained for Lb1X ray of
17.75 keV.
45. Yasuhiro IKEDA, Yoshiki NAGAFUCHI, Keisuke MAEHATA, Kenji ISHIBASHI, Takahiro UMENO, Hiroshi TAKASHIMA and Bambang PRIJAMBOEDI, Dielectric thermometer by using the quantum paraelectricity for microcalorimeter, Progress in NUCLEAR SCIENCE and TECHNOLOGY, Proceedings of the Fifth International Symposium on Radiation Safety and Detection Technology (ISORD-5), 1, 304-307, 2011.02.
46. Yuki OSHIMA, Takashi YASUMUNE, Takurou MASUDA, Keisuke MAEHATA, Kenji ISHIBASHI and Takahiro UMENO, Temperature Dependence of Li-Glass Scintillator Response to Neutrons, Progress in NUCLEAR SCIENCE and TECHNOLOGY, Proceedings of the Fifth International Symposium on Radiation Safety and Detection Technology (ISORD-5), 1, 296-299, 2011.02.
47. Makoto MAEDA, Takashi YASUMUNE, Hirofumi OGI, Keisuke MAEHATA,Hidehiko ARIMA, Kenji ISHIBASHI, Takahiro UMENO, Keiichi TANAKA, Keisuke NAKAMURA and Koji TAKASAKI, Development of TES microcalorimeter for high precision spectroscopy of LX-rays from transuranium elements, Progress in NUCLEAR SCIENCE and TECHNOLOGY, Proceedings of the Fifth International Symposium on Radiation Safety and Detection Technology (ISORD-5), 1, 226-229, 2011.02.
48. Makoto Maeda, Takashi Yasumune, Hirofumi Ogi, Keisuke Maehata, Hidehiko Arima, Kenji Ishibashi, Takahiro Umeno, Keiichi Tanaka, Keisuke Nakamura, Koji Takasaki, SPECTROSCOPIC MEASUREMENT OF LX-RAYS FROM 241Am SOURCE BY TES MICROCALORIMETER COOLED WITH LIQUID HELIUM FREE DILUTION REFRIGERATOR, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2010-10. p.63-71, 2010.12.
49. Yuki OSHIMA, Takashi Yasumune, Takuro Masuda, Keisuke Maehata, Kenji Ishibashi, Takahiro Umeno, Response of 6LiI(Eu) Scintillator coupled with an APD at Low Temperature, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2010-10. p.195-203, 2010.12.
50. T. Umeno, K. Maehata , K. Ishibashi, Y. Kamioka, S. Yoshida, K. Takasaki and K. Tanaka, Operation of a TES microcalorimeter cooled by a compact liquid-helium-free 3He–4He dilution refrigerator directly coupled to a Gifford–McMahon cooler, CRYOGENICS, 50, 5, 314-319, Vol. 50, Issue 5, pp. 314-319, 2010.05.
51. Keisuke MAEHATA, Keisuke NAKAMURA, Takashi YASUMUNE, Kenji ISHIBASHI, Koji TAKASAKI, Keiichi TANAKA, Akikazu ODAWARA and Atsushi NAGATA, Development of a TES Microcalorimeter for Spectroscopic Measurement of LX-rays Emitted by Transuranium Elements, Journal of Nuclear Science and Technology, 47, 3, 308-313, Vol. 47, No. 3, pp. 308-313, 2010.03.
52. Toru Hara, Keiichi Tanaka, Keisuke Maehata, Kazuhisa Mitsuda, Noriko Y. Yamasaki, Mitsuaki Ohsaki, Katsuaki Watanabe, Xiuzhen Yu, Takuji Ito and Yoshihiro Yamanaka, Microcalorimeter-type energy dispersive X-ray spectrometer for a transmission electron microscope, Journal of Electron Microscopy, 59, 1, 17-26, Vol. 59, No. 1, pp. 17-21, 2010.01.
53. T. Yasumune, Y. Oshima, K. Maehata, K. Ishibashi and T. Umeno, CHARACTERISTICS OF AVALANCHE PHOTODIODES AT LOW TEMPERATURES, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2009-12, p.1-10, 2010.01.
54. K Maehata, K. Nakamura, T. Yasunume, H. Ogi, M. Maeda, H. Arima, K. Ishibashi, T. Umeno, Y. Yamanaka, K. Takasaki and K. Tanaka, RESPONSE OF TES MICROCALORIMETER TO LX RAYS EMITTED FROM 241Am SOURCE BY OPERATED WITH A LIQUID-HELIUM-FREE 3He-4He DILUTION REFRIGERATOR, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2009-12. p.11-20, 2010.01.
55. Keiichi Tanaka, Kazuhisa Mitsuda, Toru Hara, Keisuke Maehata, Noriko Y. Yamasaki, Akikazu Odawara, Atsushi Nagata, Katsuaki Watanabe and Yoh Takei, Development of an energy dispersive spectrometer for a transmission electron microscope utilizing a TES microcalorimeter array, AIP Conference Proceedings, 1185, 715-718, 1185, The 13th International Workshop on Low Temperature Detectors, p.715-718, 2009.07.
56. T. Umeno, Y. Kamioka, S. Yoshida, K. Maehata, K. Ishibashi, K. Takasaki and K. Tanaka, Performance of compact liquid helium free 3He-4He dilution refrigerator directly coupled with GM cooler in TES microcalorimeter operation, 25th International Conference on Low Temperature Physics Journal of Physics: Conference Series, 150 (2009) 012051, 2009.04.
57. Y. Yamanaka, T. Ito, T. Umeno, Y. Suzuki, S. Yoshida, Y. Kamioka, and K. Maehata, Development of GM cryocooler separate type liquid-helium-free 3He-4He dilution refrigerator system, 25th International Conference on Low Temperature Physics Journal of Physics: Conference Series, 150 (2009) 012055, 2009.04.
58. Keisuke Maehata, Katsunori Ueno, Keisuke Nakamura, Takashi Yasumune, Hidehiko Arima, Kenji Ishibashi, Takahiro Umeno, Koji Takasaki, Keiichi Tanaka, Development of TES microcalorimeter for LX-ray spectroscopic analysis of transuranium elements, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2008-14, p.53-62, 2009.01.
59. Takashi Yasumune, Takuro Masuda, Keisuke Maehata, Kenji Ishibashi and Takahiro Umeno, Characteristics of avalanche photodiodes at low temperatures, Radiation Detectors and Their Uses, High Energy Accelerator Research Organization KEK Proceedings, 2008-14, pp.63-72, 2009.01.
60. Takashi Yasumune, Nobuyasu Takayama, Keisuke Maehata, Kenji Ishibashi, Takahiro Umeno, Detection of the scintillation light emitted from direct-bandgap compound semiconductors by a Si avalanche photodiode at 150 mK, Journal of nuclear science and technology, supplement 5, p. 447-450, 2008.07.
61. Katsuhiro Ueno, Akihiro Yamaguchi, Keiuske Nakamura, Keisuek Maehata, Kenji Ishibashi, Takahiro Umeno, Keiichi Tanaka, Koji Takasaki, Development of TES microcalorimeter for high precision spectroscopy of LX-ray photons emitted from transuranium elements, Journal of nuclear science and technology, supplement 5, p. 522-525, 2008.07.
Presentations
1. Keisuke Maehata, Tetsuya Sugimoto, Naoko Iyomoto, Keisuke Nakamura, Yuki Morishita, Koji Takasaki, Kazuhisa Mitsuda, L X ray spectroscopy of transuranium elements with transition edge sensor microcalorimeter, The second International Symposium on Radiation Detectors and Their Uses (ISRD2018) , 2018.01.
2. Toru Hara, Keiichi Tanaka, Keisuke Maehata, Kazuhisa Mitsuda, Yoshihiro Yamanaka, Mutsuo Hidaka, Kuniyasu Nakamura, Analytical Transmission Electron Microscope using a Transition Edge Sensor for X-ray Microanalysis, The 17th International Workshop on Low Temperature Detectors, 2017.07.
3. Naoko Iyomoto, Yuki Shuto, Takehiro Kuroiwa, Yuta Kurume, Yu Kiguchi, Keisuke Maehata, Tasuku Hayashi, Haruka Muramatsu, Kazuhisa Mitsuda, Shota Yoshimoto, Akira Takano, Development of gamma-ray position-sensitive transition-edge-sensor microcalorimeters, The 17th International Workshop on Low Temperature Detectors, 2017.07.
4. Keisuke Nakamura, Keisuke Maehata, Tetsuya Sugimoto, Yu Kiguchi, Naoko Iyomoto, Yuki Morishita, Koji Takasaki, Kazuhisa Mitsuda, Spectroscopic measurements of L X-rays with a TES microcalorimeter for a non-destructive assay of transuranium elements, The 17th International Workshop on Low Temperature Detectors, 2017.07.
5. Shota YOSHIMOTO, Keisuke MAEHATA, Naoko IYOMOTO, Kazuhisa MITSUDA, Noriko YAMASAKI, Development of a Dielectric Microcalorimeter with Quantum Ferroelectric Materials, The 17th International Workshop on Low Temperature Detectors, 2017.07.
6. Keisuke Maehata, Keisuke Nakamura, Tetsuya Sugimoto, Yu Kiguchi, Naoko IYOMOTO, Yuki Morishita, Koji Takasaki, Kazuhisa Mitsuda, Spectroscopic measurements of L X rays using a transition-edge sensor microcalorimeter for nondestructive analysis of transuranium elements, The 9th International Symposium on Radiation Safety and Detection Technology, 2017.07, The TES microcalorimeter was employed for spectroscopic measurements of L X rays emitted from 237Np, 239Pu, 241Am and 244Cm sources of typical transuranium (TRU) elements. Peaks of major L X rays of TRU elements were clearly identified in experimental energy spectra. The feasibility was considered for a nondestructive analysis of TRU elements based on experimental L X ray spectra measured by the TES microcalorimter..
7. A. Takano, K. Maehata, Naoko IYOMOTO, T. Hara, K. Mitsuda, N. Yamasaki, K. Tanaka, Development of Polycapillary Optics for a TES Microcalorimeter EDS System on a Scanning Transmission Electron Microscope, 2016 IEEE Nuclear Science Symposium & Medical Imaging Conference, 2016.11.
8. K. Maehata, T. Sugimoto, Naoko IYOMOTO, KENJI ISHIBASHI, K. Nakamura, Y. Morishita, K. Takasaki, K. Mitsuda, Spectroscopic measurement of L X-rays emitted from a 244Cm source with a TES microcalorimeter, 2016 IEEE Nuclear Science Symposium & Medical Imaging Conference, 2016.11.
9. A. Takano, K. Maehata, Naoko IYOMOTO, T. Hara, K. Mitsuda, N. Yamasaki, K. Tanaka, Characterization of Polycapillary Optics Installed in an Analytical Electron Microscope, The First Symposium on Radiation Detectors and Their Uses, 2016.01, An energy-dispersive spectrometer with a superconducting transition edge sensor (TES) microcalorimeter mounted on a scanning transmission electron microscope (STEM) is developed to enhance the accuracy of nanoscale materials analysis. TES microcalorimeters
generally have sensitive surface areas of the order of 100×100 μm2. Also, the magnetic field generated by the STEM objective lens means that a TES microcalorimeter cannot be placed in a STEM column. We therefore use polycapillary optics to collect the X-rays. In this study, X-rays are collected from a STEM specimen and are then focused on a silicon drift detector; from these measurements, the optics are characterized and the experimental results are compared with the design of the optics..
10. K. Maehata, Superconducting Radiation Detectors, The First Symposium on Radiation Detectors and Their Uses, 2016.01, Superconducting radiation detectors such as a superconducting tunnel junction (STJ), a microwave kinetic inductance detector (MKID) and a transition edge sensor (TES) microcalorimeter have been achieved an order of magnitude higher energy resolution than that of semiconductor radiation detectors in the detection of X-ray photon. The STJ and MKIDS utilize the narrow energy gap in the superconductor for the generation of large number of signal carriers by absorbing the energy of the X-ray photon. The TES microcalorimeter is a thermal detector that measures the energy of an incident X-ray photon as a temperature rise with using the sharpness of the phase transition between the superconducting and the normal conducting states.
In this talk, the resent research on the superconducting radiation detectors in Japan is reported. For students the operating principle of the superconducting radiation detectors is briefly explained before the report..
11. T. Sugimoto, K. Nakamura, M. Maeda, K. Maehata, N. IYOMOTO, K. ISHIBASHI, K. Takasaki, K. Mitsuda, ANALYSIS OF L X-RAY SPECTRA OF TRANSURANIUM ELEMENTS MEASURED BY A MICROCALORIMETER, The First Symposium on Radiation Detectors and Their Uses, 2016.01, L X-ray spectrometry is important technique for the non-destructive assay of transuranium (TRU) elements. L X-rays are emitted following the internal conversion of TRU elements. The L X-ray spectrum is, generally, obtained by a semiconductor detector. However, the accurate assay of TRU elements is difficult due to the insufficient energy resolution of the detector and slightly differences between the L X-ray lines. Recently, transition-edge-sensor (TES) microcalorimeters have been developed for spectroscopic measurements of X-rays and gamma-rays with excellent energy resolution. In this work, we measured L X-rays emitted by 244Cm and 237Np sources by a TES microcalorimeter. Energy spectra of L X-rays were obtained by processing detection signal pulses with using an optimal filtering method. Obtained L X-ray spectrum indicated that the TES microcalorimeter has enough potential to identify the L X-ray lines of TRU elements clearly. Because L X-ray natural line width and impulse response of the detector is approximated by Lorentzian distribution and Gaussian distribution, respectively, L X-ray peaks were analyzed for estimating the energy resolution by fitting the Voigt function, which is a convolution of Gauss and Lorentz functions..
12. S. Yoshimoto, K. Maehata, K. Mitsuda, K. Sakai, K. Nagayoshi, Characterization of Multi-pixel Array of TES Microcalorimeter, The First Symposium on Radiation Detectors and Their Uses, 2016.01, X-ray energy-dispersive spectroscopy (EDS) coupled with electron microscopy allows quantitative composition analysis within very small local structures by a rather simple operation. Usually Si(Li) semiconductor detectors (SSDs) are used for X-ray detection in the typical EDS systems of electron microscopes. The accuracy of the EDS is limited by the energy resolution of the X-ray detectors. The energy resolution of SSDs has reached the theoretical limit of 120 eV full width at half maximum (FWHM) at 5.9 keV. In addition, recent advanced materials research has indicated that a high energy resolution EDS system is required for use with scanning transmission electron microscopes (STEM). It is therefore necessary to develop X-ray detectors with an energy resolution superior to that of the SSDs for the next generation of EDS performed on the STEM. We have been conducted development of a TES microcalorimeter X-ray EDS system mounted on an STEM. A single pixel TES microcalorimeter EDS system was demonstrated an X-ray energy resolution of 8.6 eV FWHM in the EDS performed on the STEM at an accelerating voltage of 200 kV. A counting rate of the single pixel TES microcalorimeter was limited to 300 counts per second (cps) to obtain the energy resolution better than 10 eV FWHM. Therefore a multi-pixel array of TES microcalorimeter is developed for achieving the energy resolution better than 10 eV FWHM with the counting rate above 5 kcps. The number of pixels was selected to be 64 with consideration of the arrangement of the X-ray optic and the geometrical dimensions of the snout. Each pixel is individually connected with the input coil of the superconducting quantum interference device (SQUID) array. In order to reduce the number of wire, bias lines are connected in series for 8 pixel TESs and corresponding SQUID arrays, respectively. In this presentation we reports on measurements of response of each pixel to X-rays in the 64 pixel operation with the series bias line connection..
13. S. Yoshimoto, K. Maehata, T Hara, K. Mitsuda, K. Tanaka, Y. Yamanaka, K. Sakai, K. Nagayoshi, T. Hayashi, H. Muramatsu, Characterization system of 64 pixel array TES microcalorimeters
, 16th International Workshop on Low Temperature Detectors, 2015.07, We have constructed characterization system for 64-pixel array of TES microcalorimeters using a 3He−4He dilution refrigerator with the cooling power of 60 μW at temperature of 100 mK. A stick including 384 of Manganin wires was inserted into the refrigerator to perform characteristic measurements of multi-pixel array of the TES microcalorimeters and SQUID array amplifiers. The stick and Manganin wires were thermally anchored at temperatures of 4 K and 1 K with sufficient thermal contact. The cold end of the Manganin wires were thermally anchored and connected to NbTi wires at 0.7 K anchor. Then NbTi wires were wired to connectors placed on the holder mounted on the cold stage attached to the base plate of the mixing chamber. The heat flow to the cold stage through the installed wires was estimated to be 160 nW. In the operation test the characterization system maintained temperature below 100 mK..
14. K. Maehata, T. Hara, K. Mitsuda, M. Hidaka, K. Tanaka, Y. Yamanaka, A transition edge sensor microcalorimeter system for the energy dispersive spectroscopy performed on a scanning-transmission electron microscope, 16th International Workshop on Low Temperature Detectors, 2015.07, We have developed a transition edge sensor (TES) microcalorimeter EDS system operating on a STEM. The TES microcalorimeter was placed outside the STEM column to avoid the influence of the magnetic field generated by the objective lens of the STEM. The solid angle of the EDS system decreases with the inverse square of the length from the STEM specimen to the absorber surface of the TES microcalorimeter. In the TES microcalorimeter EDS system installed on the STEM, an X-ray polycapillary optic was employed to transport the X-rays emitted by the STEM specimen to the TES microcalorimeter placed outside the STEM column. Because it is important to maintain the operating temperature of the TES microcalorimeter with sufficient stability over long periods of time without excessive liquid helium consumption, a compact dry 3He-4He dilution refrigerator (DR) was developed. A remote helium cooling loop system with Gifford–McMahon (GM) cryocooler was employed for precooling the DR with preventing the noise and vibrations. A single pixel TES microcalorimeter EDS system was installed in a STEM for proving tests of our concept. The TES microcalorimeter consists of a bilayer TES of Au (120 nm thick) and Ti (50 nm thick) and an absorber layer of Au (0.5 μm thick, area 150 μm .
15. A. Takano, K. Maehata, N. IYOMOTO, K Yasuda, M. Maeno, K. Shiiyama, K. Tanaka, Characterization of polycapillary optics in a TES microcalorimeter EDS system installed on a SEM, 16th International Workshop on Low Temperature Detectors, 2015.07, A scanning electron microscope (SEM) is a powerful tool used to obtain micro- and nano-scale images of a material surface. A Si (Li) semiconductor detector (SSD) is used for detecting the X-rays in a typical energy dispersive spectroscopy (EDS) system. An insufficient energy resolution of the SSD results in peak overlaps of closely adjacent peaks. The superconducting transition edge sensor (TES) microcalorimeter system has been developed for improving the energy resolution of an EDS performed on the SEM. A TES microcalorimeter EDS system was installed on a SEM. The detection area of the TES microcalorimeter system is need to be improved because the solid angle is three orders smaller than that for conventional EDS system with the SSD. To increase the solid angle, we employed polycapillary optics. The X-ray transmission characteristics of polycapillary optics, such as a focal spot size and intensity gain, typically depend on the geometrical arrangements of the optics and the X-ray energy. The X-ray transmission characteristics are important parameters for determining the geometrical arrangements of the TES microcalorimeter and correcting the obtained X-ray energy spectra. In this work, we carried out energy spectrum measurements for X-rays transmitted by the polycapillary optics installed on the SEM for evaluation of the X-ray transmission characteristics of the polycapillary optics..
16. K. Nakamura, M. Maeda, K. Maehata, N. IYOMOTO, K. ISHIBASHI, K. Takasaki, K. Mitsuda, Development of a Microcalorimeter for Measurement of L X-Rays Emitted from Transuranium Elements, 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference with the 21st Symposium on Room--Temperature Semiconductor X--Ray and Gamma--Ray Detectors, 2014.11.
17. A. Takano, K. Maehata, N. IYOMOTO, T. Hara, K. Mitsuda, N. Y. Yamazaki, K. Tanaka, X-ray Transmission Characteristics Measurement of a Polycapillary Lens Installed in an Analytical Electron Microscope, 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference with the 21st Symposium on Room--Temperature Semiconductor X--Ray and Gamma--Ray Detectors, 2014.11.
18. S. Ezaki, K. Maehata, N. IYOMOTO, M. Maeda, T. Hara, K. Mitsuda, K. Tanaka, The X-ray Response of the TES Microcalorimeter with a Mushroom Shaped Absorber, Applied Superconductivity Conference, ASC 2014, 2014.08, Superconducting transition edge sensor (TES) microcalorimeters are excellent energy-resolving devices for X-ray detection. We fabricated two types of TES microcalorimeters using different values of the mushroom-shaped absorber thickness (0.5 μm: Type A and 5 μm: Type B). Both types of TES microcalorimeters were irradiated with X-ray photons emitted by an 55Fe source. X-ray detection signal pulses were collected to examine the effects of the absorber thickness on performance. The values of TES sensitivity α and the thermal conductance G were obtained by analyzing the current-voltage characteristics of TES considering the decay time constant of the detection signal pulses of different absorber thicknesses. By comparing the temperature dependence of G and the values of α and G for Types A and B TESs, the absorber thickness was found to not affect the electrical and thermal properties of TESs. The experimental ratio of the full width at half maximum value between Type A and B TESs agreed with theoretical estimations based on different absorber thicknesses. .
19. K. Maehata, N. IYOMOTO, Y. Yamanaka, T. Ito, T. Hara, K. Mitsuda, N. Y. Yamasaki, K. Tanaka, Development of a compact dry dilution refrigerator for operating a TES micro calorimeter X-ray detector on electron microscopes, The 4th International Conference on Superconductivity and Magnetism 2014, 2014.05, A compact dry 3He-4He dilution refrigerator (DR) was developed for operating a superconducting transition edge sensor (TES) microcalorimeter X-ray detector mounted on a transmission electron microscope. A Gifford–McMahon (GM)-type mechanical cryocooler was used for a pre-cooler of the DR to operate the TES microcalorimeter without consuming liquid helium.
To reduce sound and vibrations generated by the GM cryocooler, the DR was separated from the GM cryocooler in a split system which allows a remote helium cooling loop for pre-cooling the DR. In the DR unit, the dilution components of the still, the heat exchangers, and the cascade of two mixing chambers were assembled into a compact cylinder. A snout made of an oxigen-free copper rod was attached to the mixing chamber of the DR for placing the TES microcalorimeter X-ray detector. The lowest temperature and the cooling power in the mixing chamber were measured to be 87 mK and 20 uW at 100 mK, respectively. The DR unit was demonstrated to maintain a temperature on the top of the snout below that of operating a multi-pixel-array TES microcalorimeter X-ray detector..
20. M. Maeda, K. Maehata, N. IYOMOTO, K. ISHIBASHI, K Takasaki, K. Nakamura, K. Aoki, K. Mitsuda, K. Tanaka, Spectroscopic measurement of L X-rays emitted by transuranium elements by using TES Microcalorimeter, 15th International Workshop on Low Temperature Detectors, 2013.06.
21. 前畑 京介, 伊豫本 直子, 前田 亮, 江崎 翔平, 高野 彬, 松村 晶, 原 徹, 満田 和久, 山崎 典子, 田中 啓一, Development of 4-pixel array TES microcalorimeters with a mushroom shaped absorber supported by an insulating layer in an overhang region, 15th International Workshop on Low Temperature Detectors, 2013.06, 4-pixel-array superconducting transition-edge sensor (TES) microcalorimeters with a mushroom shaped absorber were developed for an energy dispersive spectroscopy performed on the transmission electron microscope. The TES consists of a bilayer of Au/Ti with 120nm/50nm thick. The mushroom shaped absorber is made from a Au layer and the absorber stem is deposited on the center of the TES surface. A Ta2O5 insulating layer of 100 nm thick was inserted between the overhang region of the absorber and the TES surface. Two types of 4-pixel-
array TES microcalorimeter were fabricated with the absorber of 0.5 um and 5 um thick. The energy resolution of 15 eV FWHM at 5.9 keV X-ray was obtained by operating the 4-pixel-array TES microcalorimeter with the mushroom shaped absorber of 0.5 um thick..
22. Estimation of emission probability of LX-rays emitted by Americium 241 by using a TES microcalorimeter.
23. Energy dispersive X-ray spectrum analysis of a uranium ore by using a TES maicrocalorimeter installed in a SEM.
24. Development of TES microcalorimeter spectroscopy system for a transmission electron microscope.
Awards
  • The 45th Atomic Energy Society of Japan Award (2012), Best paper,
    Paper Title: Development of a TES microcalorimeter for spectroscopic measurement of LX-rays emitted by transuranium elements
  • Ohyama Memorial Awards of 1993 for encouragement of young scientists and engineers, Cryogenics and Superconductivity Society of Japan
Educational
Educational Activities
Undergraduate: Atomic Physics, Radiation Detection and Measurement, Electronic Circuits
Graduate course: Radiation Physics and Detection I, Radiation Physics and Detection II, Electrodynamics for Nuclear Engineering
Social
Professional and Outreach Activities
Introductive Lecture on Science and Technology for Senior High School Students
Introductive School of Radiation for Junior High School Students.