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Publications (6)6.87 Total impact

  • K. Maehata · T. Hara · K. Mitsuda · M. Hidaka · K. Tanaka · Y. Yamanaka ·
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    ABSTRACT: 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 (Formula presented.)He-(Formula presented.)He 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 M(Formula presented.), Pt M(Formula presented.), and Ir M(Formula presented.). Using an electron device sample, element distribution maps of Si, Ti, and W were obtained using a Si K(Formula presented.) X-ray energy resolution of 9.7 eV FWHM.
    Journal of Low Temperature Physics 11/2015; DOI:10.1007/s10909-015-1361-3 · 1.02 Impact Factor
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    ABSTRACT: 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.
    Journal of Nuclear Science and Technology 04/2015; 52(4). DOI:10.1080/00223131.2014.957744 · 1.12 Impact Factor
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    ABSTRACT: 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 μW 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 KαX-rays of 1.74 keV was obtained by TES microcalorimeter EDS performed with the transmission electron microscope.
    Cryogenics 05/2014; DOI:10.1016/j.cryogenics.2014.03.002 · 1.17 Impact Factor
  • K. Maehata · N. Iyomoto · Y. Yamanaka · T. Ito · T. Hara · K. Mitsuda · N. Y. Yamasaki · K. Tanaka ·
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    ABSTRACT: A compact dry 3He- 4He dilution refrigerator (DR) was developed for operation of 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 as a DR pre-cooler to operate the TES microcalorimeter without consuming liquid helium. To reduce the noise and vibrations generated by the GM cryocooler, the DR was separated from the cryocooler in a split system that allows a remote helium cooling loop to pre-cool the DR. In the DR unit, the dilution components of the still, the heat exchangers, and the cascade pair of mixing chambers were assembled into a compact cylinder. A snout made from an oxygen-free copper rod was attached to the DR mixing chamber for placement of 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 μW at 100 mK, respectively. The DR unit was shown to maintain the temperature on top of the snout such that it was below the temperature required for multi-pixel-array TES microcalorimeter x-ray detector operation.
    Journal of Superconductivity and Novel Magnetism 03/2014; 28(3). DOI:10.1007/s10948-014-2699-5 · 0.91 Impact Factor
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    ABSTRACT: Nondestructive plutonium monitoring during reprocessing of spent nuclear fuel and in mixed-oxide-fuel fabrication facilities is expected to require spectroscopic measurements of L X-rays ranging from 10 to 20 keV. To this end, L X-ray emission intensities of transuranium elements will be important parameters in estimating the plutonium isotopic composition from L X-ray spectra. However, owing to fine structure within the L X-ray spectra, significant discrepancies exist among theoretical values, reference and experimental data concerning these emission intensities. To obtain better spectroscopic measurements, we used a TES microcalorimeter to get the energy spectrum of L X-rays emitted by 237Np resulting from α-decay of a 241Am source. Values for the L X-ray emission intensities were estimated by analyzing the spectral data and compared with previous data. We advocate for improvements in evaluation of emission intensities given the enhanced precision afforded by TES microcalorimetry.
    Journal of Low Temperature Physics 06/2012; 167(5-6). DOI:10.1007/s10909-012-0500-3 · 1.02 Impact Factor
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    ABSTRACT: A new energy dispersive X-ray spectrometer (EDS) with a microcalorimeter detector equipped with a transmission electron microscope (TEM) has been developed for high- accuracy compositional analysis in the nanoscale. A superconducting transition-edge-sensor-type microcalorimeter is applied as the detector. A cryogen-free cooling system, which consists of a mechanical and a dilution refrigerator, is selected to achieve long-term temperature stability. In order to mount these detector and refrigerators on a TEM, the cooling system is specially designed such that these two refrigerators are separated. Also, the detector position and arrangement are carefully designed to avoid adverse affects between the superconductor detector and the TEM lens system. Using the developed EDS system, at present, an energy resolution of 21.92 eV full-width-at-half maximum has been achieved at the Cr K alpha line. This value is about seven times better than that of the current typical commercial Si(Li) detector, which is usually around 140 eV. The developed microcalorimeter EDS system can measure a wide energy range, 1-20 keV, at one time with this high energy resolution that can resolve peaks from most of the elements. Although several further developments will be needed to enable practical use, highly accurate compositional analysis with high energy resolution will be realized by this microcalorimeter EDS system.
    Journal of electron microscopy 09/2009; 59(1):17-26. DOI:10.1093/jmicro/dfp043 · 1.63 Impact Factor