Ibaraki University's
Graduate School of Science and Engineering (Science)
Department of Science (Physics Course)

Associate Professor



  1. (研究経歴)
     1999-2001 Department of Physics, Institute for Cosmic Ray Research, University of Tokyo
     Development of the data acquisition system of the environmental monitor (weather/cloud monitor, temperature sensor for electronics) for CANGAROO-III Cherenkov telescope array (TeV gamma-ray observatory).
     Awarded the degree of MSc in physics for a thesis entitled "Development of the environmental monitor system for CANGAROO-III" Work
     2001-2004 Department of Physics, Institute for Cosmic Ray Research, University of Tokyo
     Analysis of TeV gamma-ray data of the CANGAROO-II from supernova remnants (SN1987A, RX J0852.0-4622)
     Awarded the degree of PhD in physics for a thesis entitled "Detection of TeV gamma-rays from the Supernova Remnant RX J0852.0-4622" Work supervised by Professor Mori
     2004-2006 Postdoctoral fellow at the Department of Physics, Kyoto University
     Analysis of TeV gamma-ray data of CANGAROO-III gamma-ray experiment
     Development of astronomical X-ray polarimeter using micro pixel chamber (mu-PIC) on board satellite.
     2006-present
     Study of cosmic ray acceleration in supernova remnants (SNRs) by analyzing the Fermi satellite data. Fermi satellite was launched in 2008 to observe GeV gamma rays from astronomical objects. I developed the analysis code to investigate extended sources like SNRs.
    ☐ Development of the Compton camera GammaI using CsI(Tl) scintillators for measurement of arrival direction of gamma rays produced by radioactive cesium released into the environment from the Fukushima Dai-ichi Nuclear Power Plant accident due to the great east Japan earthquake and subsequent tsunamis in 2011 and application of GammaI for measurement of cosmic gamma rays, environmental monitoring of radiation in nuclear medicine facility, accelerators, nuclear power plant, etc.
     ☐ Development of equipment for the next generation Cherenkov observarory (CTA)

    Technical experience:
    1. Analysis;
     Data from the imaging atmospheric Cherenkov telescope
     Fermi gamma-ray satellite
    2. Computer programming;
     Analysis and data acquisition system using C++ , C, python, and Fortran languages
    3. Electronics;
     Data acquisition system
    4. Others;
     Experiments using gas chamber
     Operation of imaging atmospheric Cherenkov telescope
     Operation of satellite (Suzaku, data monitoring for Fermi satellite)

Academic background

  1. The University of Tokyo Graduate School, Division of Science Doctor course 2004/03 Completed
  2. The University of Tokyo Graduate School, Division of Science Master course 2001/03 Completed
  3. The University of Tokyo Faculty of Science 1999/03 Graduated

Academic degrees

  1. M.Sc. The University of Tokyo 2001/03
  2. Ph.D. (Science) The University of Tokyo 2004/03

Research Areas

  1. Particle/Nuclear/Cosmic ray/Astro physics
  2. Astronomy

Research keywords

  1. Gamma-ray astronomy, High-energy astrophysics, development of detectors, cosmic rays

Subject of research

  1. ガンマ線天文学、高エネルギー宇宙物理学 ガンマ線天文学、高エネルギー宇宙物理学
  2. 放射線検出器開発 2012/01/01-Present

Research Projects (Competitive Research Funds)

  1. 核融合、放射線治療、宇宙観測分野で応用可能な革新的ガンマ線カメラの原理実証 Others 平成30年度研究推進経費(Research Booster) 2018/07/25-2019/03/31
  2. 大口径大気チェレンコフγ線望遠鏡の稼働で迫る高エネルギー天体現象の発展的理解 Science research expense 2017/04/01-2021/03/31
  3. 放射能汚染地域におけるシイタケ原木林の利用再開・再生技術の開発 Others 農林水産業・食品産業科学技術研究推進事業 【実用技術開発ステージ】 (現場ニーズ対応型) 農林水産省 2016-2018
  4. 結晶シンチレータによる医療用高感度γ線コンプトンカメラの開発 Science research expense 2015/04/01-2019/03/31
  5. セシウム137からのガンマ線の到来方向が分かる安価な高感度放射線検出器「ガンマアイ」の改良 Others 茨城大学復興支援プロジェクト 2014-2015


  1. Research paper (scientific journal) Joint Remote measurement of urinary radioactivity in 18F-FDG PET patients using Compton camera for accuracy evaluation of standardized uptake value [F-1] Watanabe, Takara; Kano, Daisuke ; Enomoto, Ryoji; Muraishi, Hiroshi; Wakamatsu, Ryo ; Katagiri, Hideaki ; Kagaya, Mika ; Kondo, Ryotaro ; Fukushi, Masahiro ; Hosokawa, Syota ; Takeda, Tohoru; M. Tanaka, Manobu; Uchida, Tomohisa; Nakagami, Yoshihiro Biomed. Phys. Eng. Express 4, 065029 2018/10/25 10.1088/2057-1976/aae6b8 Currently, the most commonly used estimate of metabolic activity during clinical positron emission tomography (PET) is standardized uptake value (SUV) obtained from 18F-fluorodeoxyglucose (18F-FDG) captured in cancer cells. Although SUV is evaluated after corrections for the injected dose, weight, and other such parameters, the entire injected dose is inappropriate for this calculation because someFDGis excreted in urine. Therefore, the injected dose warrants correction by assessment of urinary radioactivity in patients before PET to enhance the accuracy of FDG calculation. However, this is not typically performed in clinical practice owing to secondary effects of radioactive contamination in hospitals and radiation exposure risk to the attending staff. Therefore, we aimed to develop a remote method for the measurement of urinary radioactivity in FDG-PET patients. Urinary radioactivity was estimated in a toilet bowl using gamma-ray distribution obtained with a Compton camera. The gamma-ray events from the toilet bowl per unit time (5 s) facilitated radioactivity calculation. Between 0 and 40 MBq, deviation of our detector from the linearity for radioactivity was <8.3%.
  2. Research paper (scientific journal) Joint Development of an all-sky gamma-ray Compton camera based on scintillators for high-dose environments Hideaki Katagiri, Wataru Satoh, Ryoji Enomoto, Ryo Wakamatsu, Takara Watanabe, Hiroshi Muraishi, Mika Kagaya, Souichi Tanaka, Kiyoto Wada, Manobu Tanaka & Tomohisa Uchida Journal of Nuclear Science and Technology 55/ 10, 1172-1179 2018/06/19 10.1080/00223131.2018.1485598 We developed an all-sky Compton camera for the detection of sub-MeV gamma rays emitted by radioactive cesium in high-dose environments. The camera consisted of six NaI (Tl) scintillators with a diameter of 1/2 in (1.3 cm) placed symmetrically at the vertexes of an octahedron. Irradiation tests with a point-like source at a high-dose irradiation facility confirmed that the camera can measure the arrival directions of sub-MeV gamma rays and visualize a gamma-ray source distribution in environments of up to ∼1 mSv/h. Due to the symmetrical geometry of the camera, the directional variance of its acceptance fell within ±23% (full width) of the average value. The camera capability to detect gamma rays in high-dose environments, in which multiple and/or extended sources exist, was verified in environments of up to ∼0.2 mSv/h by tests at the Fukushima Daiichi nuclear power plant. The imaging capability was confirmed also in lower dose environments such as 1 μSv/h for a reasonable observation time of 2 h, indicating that the developed camera is adequate for practical use in environments with a wide dynamic range of dose rate (∼200 times), i.e. from 1 μSv/h to 0.2 mSv/h.
  3. Research paper (scientific journal) Joint Development of an omnidirectional gamma-ray imaging Compton camera for low-radiation-level environmental monitoring Watanabe Takara, Enomoto Ryoji, Muraishi Hiroshi, Katagiri Hideaki, Kagaya Mika, Fukushi Masahiro, Kano Daisuke, Satoh Wataru, Takeda Tohoru, Tanaka Manobu, Tanaka Souichi, Uchida Tomohisa, Wada Kiyoto, Wakamatsu Ryo Jpn. J. Appl. Phys. Institute of Physics 57/ 2 2017/12/27 0021-4922 URL We have developed an omnidirectional gamma-ray imaging Compton camera for environmental monitoring at low levels of radiation. The camera consisted of only six CsI(Tl) scintillator cubes of 3.5 cm, each of which was readout by super-bialkali photo-multiplier tubes (PMTs). Our camera enables the visualization of the position of gamma-ray sources in all directions (∼4π sr) over a wide energy range between 300 and 1400 keV. The angular resolution (σ) was found to be ∼11°, which was realized using an image-sharpening technique. A high detection efficiency of 18 cps/(µSv/h) for 511 keV (1.6 cps/MBq at 1 m) was achieved, indicating the capability of this camera to visualize hotspots in areas with low-radiation-level contamination from the order of µSv/h to natural background levels. Our proposed technique can be easily used as a low-radiation-level imaging monitor in radiation control areas, such as medical and accelerator facilities.
  4. Research paper (scientific journal) Joint Constraints on Physical Conditions for the Acceleration on Ultra-high-energy Cosmic Rays in Nearby Active Galactic Nuclei Observed with the Fermi Large Area Telescope Kagaya, M., Katagiri, H., Yoshida, T., and Fukuda, A. The Astrophysical Journal 850/ 33 2017/11 We investigated the possibility of acceleration of ultra-high-energy cosmic rays (UHECRs) in nearby active galactic nuclei (AGNs) using archival multi-wavelength observational data, and then we constrained their physical conditions, i.e., the luminosity of the synchrotron radiation and the size of the acceleration site. First, we investigated the spatial correlation between the arrival directions of UHECRs and the positions of nearby AGNs in the Fermi third gamma-ray source catalog. We selected 27 AGNs as candidates of accelerators of UHECRs. Then, we evaluated the physical conditions in the acceleration regions of these AGNs via the Pe'er and Loeb method, which uses the peak luminosity of synchrotron radiation and the peak flux ratio of inverse Compton scattering to synchrotron radiation. From the evaluation, we found that six AGNs have the ability to accelerate ultra-high-energy (UHE) protons in the AGN cores. Furthermore, we found that the minimum acceleration size must be more than a few kpc for acceleration of UHE protons in the AGN lobes.
  5. Research paper (scientific journal) Joint Fermi LAT Discovery of Extended Gamma-Ray Emissions in the Vicinity of the HB 3 Supernova Remnant The Astrophysical Journal 818, 114 2016 10.3847/0004-637X/818/2/114 We report the discovery of extended gamma-ray emission measured by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) HB 3 (G132.7+1.3) and the W3 II complex adjacent to the southeast of the remnant. W3 is spatially associated with bright 12CO (J = 1-0) emission. The gamma-ray emission is spatially correlated with this gas and the SNR. We discuss the possibility that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray emission. The emission from W3 is consistent with irradiation of the CO clouds by the cosmic rays accelerated in HB 3.

Research presentations

  1. Oral presentation(general) 無機シンチレーターを用いた高線量場用コンプトン型全方向ガンマ線カメラの実証試験 日本原子力学会2018年春の年会 2018/03/26 これまで開発してきた高線量場でも使用可能で全方向からのガンマ線の到来方向を測定可能なコンプトン型カメラを用いて福島第一原発敷地内およびJ-PARC 3GeVシンクロトロンのビーム照射後の残留放射能を測定し、高線量環境下で様々な放射能分布の可視化が可能であることを実証した。
  2. Oral presentation(general) Development of an all-sky RI imaging monitor capable of measuring high-dose-rate gamma-ray sources 日本医学物理学会 2016/04
  3. Oral presentation(general) CsI(Tl)シンチレータによるオールスカイガンマ線コンプトンカメラの開発 日本物理学会 2016/03
  4. Oral presentation(general) シンチレータを用いた高線量場測定用コンプトンカメラの開発 日本物理学会 2016/03
  5. Oral presentation(general) ガンマ線の到来方向が判断できる4チャンネル型高感度サーベイメータの開発 日本物理学会 2016/03

Intellectual property rights

  1. Patent 放射能測定装置、放射能測定方法、放射能情報処理サーバおよび放射能情報処理システム 2018-167492 2018/09/07
  2. Patent 放射能測定システム及び放射能測定方法 2017-046902 2017/03/13


  1. 第111回日本医学物理学会学術大会 大会長賞 Development of an all-sky RI imaging monitor capable of measuring high-dose-rate gamma-ray sources 2016/04
  2. 第110 回日本医学物理学会学術大会 優秀研究賞 ガンマ線の到来方向がわかるコンプトン型サーベイメータの開発 2015/09
  3. 第107回日本医学物理学会学術大会大会長賞 Development of a novel γ-ray imaging system (γI:gamma-eye) using Compton camera technique 2014
  4. 第33回日本医用画像工学会大会 奨励賞 コンプトカメラ法による360°パノラマRI イメージングモニターの開発 2013
  5. 第106 回日本医学物理学会学術大会優秀研究賞 Application of a filtered back projection algorithm to Compton camera technique 2013

Alloted class

  1. Introductory physics I
  2. Experiments in General Physics
  3. Astrophysics II
  4. Scientific English Reading I
  5. Scientific English Reading II

Memberships of academic societies

  1. The Physical Society of Japan
  2. The Astronomical Society of Japan
  3. 日本原子力学会

Joint / funded research

  1. ガンマ線可視化カメラの開発 2017/01-2018/03 Domestic
  2. ガンマ線可視化カメラの開発 2015/11-2016/09 Domestic
  3. ガンマ線可視化カメラの開発 2014/05-2015/03 Domestic
  4. ガンマアイ(γI)コンプトンカメラの研究開発 2013-2014 Domestic