Mr. Koki Okazaki Profile

Koki Okazaki

at Osaka Univ

SPIE Involvement:

Author

Publications (9)

Proceedings Article | 31 August 2022 Presentation + Paper

Sub-arcsecond x-ray imaging with Multi-Image X-ray Interferometer Module (MIXIM): introduction of a periodic coded-aperture mask

Kazunori Asakura, Kiyoshi Hayashida, Shotaro Sakuma, Ayami Ishikura, Kenmei Sawagami, Wataru Kamogawa, Tomokage Yoneyama, Hirofumi Noda, Koki Okazaki, Maho Hanaoka, Kengo Hattori, Yusuke Matsushita, Taisei Mineta, Marina Yoshimoto, Yuichi Ode, Tomohiro Hakamata, Hironori Matsumoto, Hiroshi Tsunemi

Proceedings Volume 12181, 1218129 (2022) https://doi.org/10.1117/12.2629656

KEYWORDS: X-rays, Spatial resolution, X-ray imaging, Coded apertures, Interferometers, Sensors, X-ray detectors, Transmittance, X-ray sources, X-ray astronomy

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Proceedings Article | 18 December 2020 Presentation + Paper

Sub-arcseconds to micro-arcsecond x-ray imaging with multi image x-ray interferometer method (MIXIM): concept and scalabe mission plans

Kiyoshi Hayashida, Kazunori Asakura, Ayami Ishikura, Shotaro Sakuma, Takashi Hanasaka, Tomoki Kawabata, Tomokage Yoneyama, Hirofumi Noda, Koki Okazaki, Maho Hanaoka, Kengo Hattori, Kenmei Sawagami, Wataru Kamogawa, Hiroshi Nakajima, Yusuke Matsuhita, Taisei Mineta, Marina Yoshimoto, Tomohiko Hakamata, Yuichi Ode, Hironori Matsumoto, Hiroshi Tsunemi, Hisamitsu Awaki, Yuichi Terashima, Toshihiro Kawaguchi

Proceedings Volume 11444, 114441C (2020) https://doi.org/10.1117/12.2562193

KEYWORDS: X-ray imaging, X-rays, Interferometers, Diffraction gratings, Sensors, Image resolution, Spatial resolution, Satellites, Astronomy, Visibility

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Proceedings Article | 13 December 2020 Presentation + Paper

Soft x-ray imager (SXI) for Xtend onboard X-Ray Imaging and Spectroscopy Mission (XRISM)

Hiroshi Nakajima, Kiyoshi Hayashida, Hiroshi Tomida, Koji Mori, Hirofumi Noda, Hironori Matsumoto, Tomokage Yoneyama, Koki Okazaki, Kazunori Asakura, Maho Hanaoka, Kengo Hattori, Ayami Ishikura, Shotaro Sakuma, Takaaki Tanaka, Hiroyuki Uchida, Takeshi Tsuru, Yuki Amano, Hiromichi Okon, Makoto Yamauchi, Isamu Hatsukade, Yusuke Nishioka, Yoshiaki Kanemaru, Jin Sato, Toshiyuki Takaki, Yuta Terada, Tessei Yoshida, Takayoshi Kohmura, Kouichi Hagino, Shogo Kobayashi, Hiroshi Murakami, Hikari Kashimura, Hideki Uchiyama, Kazutaka Yamaoka, Masayoshi Nobukawa, Takashi Sako, Kumiko Nobukawa, Mariko Saito, Junko Hiraga, Yukino Urabe, Masayuki Yoshida, Tadayasu Dotani, Masanobu Ozaki, Hiroshi Tsunemi

Proceedings Volume 11444, 1144423 (2020) https://doi.org/10.1117/12.2560348

KEYWORDS: X-ray imaging, Charge-coupled devices, Imaging spectroscopy, Spectroscopy, X-rays, X-ray telescopes, CCD image sensors, Fermium, Frequency modulation, CCD cameras

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Proceedings Article | 13 December 2020 Presentation + Paper

Subsub-arcseconds x-ray imaging with multi-image x-ray interferometer module (MIXIM): experimental results

Kazunori Asakura, Kiyoshi Hayashida, Takashi Hanasaka, Tomoki Kawabata, Tomokage Yoneyama, Hirofumi Noda, Shotaro Sakuma, Koki Okazaki, Ayami Ishikura, Maho Hanaoka, Shuntaro Ide, Kengo Hattori, Hironori Matsumoto, Hiroshi Tsunemi, Hisamitsu Awaki, Hiroshi Nakajima, Junko Hiraga

Proceedings Volume 11444, 114441D (2020) https://doi.org/10.1117/12.2560772

KEYWORDS: X-rays, X-ray imaging, X-ray detectors, Interferometers, CMOS sensors, Diffraction gratings, X-ray astronomy, Sensors, Spatial resolution, Astronomy

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Proceedings Article | 13 December 2020 Presentation + Paper

On-ground calibration of XRISM/Xtend CCD

Tomokage Yoneyama, Hirofumi Noda, Maho Hanaoka, Kiyoshi Hayashida, Koki Okazaki, Kazunori Asakura, Yoshiaki Kanemaru, Jin Sato, Toshiyuki Takaki, Koji Mori, Takashi Sako, Masayoshi Nobukawa, Mariko Saito, Kumiko Nobukawa, Hiroshi Murakami, Yuki Amano, Hiroyuki Uchida, Hideki Uchiyama, Hiroshi Tomida, Hiroshi Nakajima, Kengo Hattori, Shotaro Sakuma, Ayami Ishikura, Hironori Matsumoto, Hiromichi Okon, Takaaki Tanaka, Takeshi Tsuru, Yukino Urabe, Junko Hiraga, Akira Kashimura, Shogo Kobayashi, Kouichi Hagino

Proceedings Volume 11444, 1144425 (2020) https://doi.org/10.1117/12.2561524

KEYWORDS: Charge-coupled devices, Calibration, X-rays, X-ray imaging, Fermium, Frequency modulation, X-ray telescopes, X-ray sources, Imaging spectroscopy, Spectroscopes

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SPIE Journal Paper | 6 June 2019

X-ray imaging polarimetry with a 2.5-μm pixel CMOS sensor for visible light at room temperature

Kazunori Asakura, Kiyoshi Hayashida, Takashi Hanasaka, Tomoki Kawabata, Tomokage Yoneyama, Koki Okazaki, Shuntaro Ide, Hirofumi Noda, Hironori Matsumoto, Hiroshi Tsunemi, Hisamitsu Awaki, Hiroshi Nakajima

JATIS, Vol. 5, Issue 03, 035002, (June 2019) https://doi.org/10.1117/12.10.1117/1.JATIS.5.3.035002

KEYWORDS: X-rays, Polarimetry, X-ray detectors, Sensors, X-ray imaging, CMOS sensors, Polarization, Visible radiation, X-ray astronomy, Charge-coupled devices

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Proceedings Article | 20 July 2018 Presentation + Paper

The spectral response of X-ray CCDs in the energy band around Si-K edge: a solution to the Si-K edge problem for the XIS onboard Suzaku

Koki Okazaki, Kiyoshi Hayashida, Hiroshi Nakajima, Riku Shomura, Tomokage Yoneyama, Hironori Matsumoto, Hiroshi Tsunemi, Koji Mori, Masahiro Tsujimoto, Yoshitomo Maeda, Ken Ebisawa

Proceedings Volume 10709, 107091F (2018) https://doi.org/10.1117/12.2314259

KEYWORDS: X-rays, Calibration, Matrices, Sensors, Charge-coupled devices, X-ray imaging, Quantum efficiency, Cameras, Absorption, X-ray astronomy

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X-ray Imaging Spectrometers (XIS) are the X-ray CCD cameras onboard Suzaku. They were operated in orbit from 2005 to 2015 and produced lots of findings with their good energy resolution and low non X-rat background. Precise calibration including the 10 eV accuracy in the energy scale reinforced them. Nevertheless, there has been a unresolved calibration issue in the spectral response around the Si-K edge (1.839 keV) appearing as systematic residuals up to 10%. The residual is negative peaking at 1.85 keV in the front illuminated (FI) sensors and positive peaking at 1.8 keV in the back illuminated (BI) sensor for X-ray sources dominated by continuum X-ray emission. Various attempts to eliminate these residuals by changing response parameters or quantum efficiency models have been insufficient. In this paper, we revisit this problem by focusing on the relation between incident X-ray energy and pulse height. We introduce a jump in that relation at the Si-K edge by modifying the , and optimize its value so as to minimize the residuals in the fit of the X-ray spectra for the black hole binary LMC X-3, a source dominated by continuum emission. We find the introduction of a jump significantly reduces the residuals. The optimized jump values are +4:2 channel, +4:0 channel, and -3:1 channel, corresponding to 15.3 eV, -11:3 eV, and 14.6 eV, for XIS0, XIS3 (FI), and XIS1 (BI), respectively. The direction of the jump is opposite for the FI and for the BI. We revise the response matrices generator so as to include the jump for each XIS sensor, and apply it to the X-ray spectra of the Perseus cluster of galaxies which has various emission lines in the spectra, and the blazar PKS2155-304 which was observed various epoch in the Suzakuoperation. We confirm the residuals are significantly reduced for these sources, too. We finally suggest the jump at Si-K edge in the energy and pulse height relation is qualitatively explained, if some of charges are lost in course of charger collection to the electrode of the CCD in the depletion later, and its amount is large for larger travel length in the depletion layer. If this explanation is correct, the Si-K edge problem and its solution presented in this paper is not specific only for the SuzakuXIS but also for other X-ray CCDs.

Proceedings Article | 10 July 2018 Presentation + Paper

Sub-arcsecond imaging with multi-image x-ray interferometer module (MIXIM) for very small satellite

Kiyoshi Hayashida, Tomoki Kawabata, Takashi Hanasaka, Kazunori Asakura, Tomokage Yoneyama, Koki Okazaki, Shuntaro Ide, Hironori Matsumoto, Hiroshi Nakajima, Hisamitsu Awaki, Hiroshi Tsunemi

Proceedings Volume 10699, 106990U (2018) https://doi.org/10.1117/12.2314181

KEYWORDS: X-rays, Sensors, X-ray detectors, X-ray imaging, Interferometers, X-ray sources, CMOS sensors, Satellites, Interferometry, Collimators

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We have proposed a new type of X-ray interferometer called Multi Image X-ray Interferometer Module (MIXIM) consisting simply of a grating and an X-ray spectral imaging detector. The baseline concept of MIXIM is a slit camera to obtain the profile of X-ray sources, but aim to get a sub-arcsecond resolution. For that purpose, to avoid blurring of the image by diffraction is a key, and we select X-ray events of which energy satisfies the interferometric condition called Talbot effect. Stacking the images (X-ray interferometric fringes) with the period of the grating is another point of the method, which provides the self image of a grating slit convolved with the profile of the X-ray source. We started an experiment with a micro focus X-ray source, 4.8 μm pitch grating, and an SOI type X-ray detector XRPIX2b with a pixel size of 30 μm. The stacked self image was obtained with a magnification factor of 4.4. We, however, need finer positional resolution for the detector to obtain the self image to a parallel beam, for which the magnification factor must be 1. We thus focused on small pixel size CMOS sensors developed for visible light. We irradiated X-rays to one of such CMOS sensors GSENSE5130 with a pixel size of 4.25 μm, and found enough capability to detect X-rays, i.e., FWHM of 207 eV at 5.9 keV at room temperature. We then employed this sensor and performed an experiment at a 200 m beam line of BL20B2 in the synchrotron facility SPring8. Using a grating with a pitch of 4.8 µm and an opening fraction of f=0.5, we obtained the self image of the grating at the detector distance from the grating of 23 cm and 46 cm and the X-ray energy of 12.4 keV. We also performed an experiment using a 9.6 μm f = 0.2 grating with a detector-grating distance of 92 cm, and obtained higher contrast image of the grating. Note that the slit width of 2.4 μm at 46 cm corresponds to 1.1′′, while that of 1.9 μm at 92 cm does 0.43′′. We suggest several format of possible MIXIM missions, including MIXIM-S for very small satellite of 50cm size, MIXIM-P for parasite use of nominal X-ray observatory employing grazing X-ray telescopes with a focal length of 10 m, and MIXIM-Z in which the grating-detector distance of 100 m is acquired by formation flight or free fryers to yield 0.01” level resolution.

Proceedings Article | 10 July 2018 Presentation + Paper

Soft x-ray imaging telescope (Xtend) onboard X-ray Astronomy Recovery Mission (XARM)

Kiyoshi Hayashida, Hiroshi Tomida, Koji Mori, Hiroshi Nakajima, Takaaki Tanaka, Hiroyuki Uchida, Takeshi Tsuru, Hiroshi Murakami, Takashi Okajima, Takayoshi Kohmura, Kouichi Hagino, Shogo Kobayashi, Manabu Ishida, Yoshitomo Maeda, Hideki Uchiyama, Kazutaka Yamaoka, Hironori Matsumoto, Masayoshi Nobukawa, Kumiko Nobukawa, Junko Hiraga, Makoto Yamauchi, Isamu Hatsukade, Yang Soong, Hideyuki Mori, Takayuki Hayashi, Hiroshi Tsunemi, Masanobu Ozaki, Tadayasu Dotani, Junichi Iwagaki, Tomokage Yoneyama, Koki Okazaki, Kazunori Asakura, Satomi Onishi, Yoshiaki Kanemaru, Jin Sato, Yusuke Nishioka, Ayaki Takeda, Hiromichi Okon, Masayuki Yoshida, Takeo Shimoi

Proceedings Volume 10699, 1069923 (2018) https://doi.org/10.1117/12.2311446

KEYWORDS: Charge-coupled devices, X-rays, Aluminum, X-ray telescopes, Coating, X-ray imaging, Mirrors, Satellites, Electronics, Fermium

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Showing 5 of 9 publications

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