投稿日: 2018年9月6日

Short-Lived Radioisotope 98Tc Synthesized by the Supernova Neutrino Process

Takehito Hayakawa, Heamin Ko, Myung-Ki Cheoun, Motohiko Kusakabe, Toshitaka Kajino, Mark D. Usang, Satoshi Chiba, Ko Nakamura, Alexey Tolstov, Ken’ichi Nomoto, Masa-aki Hashimoto, Masaomi Ono, Toshihiko Kawano, and Grant J. Mathews

Phys. Rev. Lett. 121, 102701 – Published 4 September 2018

The isotope 98Tc decays to 98Ru with a half-life of 4.2×106 yr and could have been present in the early Solar System. In this Letter, we report on the first calculations of the production of 98Tc by neutrino-induced reactions in core-collapse supernovae (the ν process). Our predicted 98Tc abundance at the time of solar system formation is not much lower than the current measured upper limit raising the possibility for its detection in the not too distant future. We show that, if the initial abundance were to be precisely measured, the 98Tc nuclear cosmochronometer could be used to evaluate a much more precise value of the duration time from the last core-collapse supernova to the formation of the solar system. Moreover, a unique and novel feature of the 98Tc ν-process nucleosynthesis is the large contribution (∼20%) from charged current reactions with electron antineutrinos. This means that 98Tc becomes a unique new ν-process probe of the temperature of the electron antineutrinos.

DOI: https://doi.org/10.1103/PhysRevLett.121.102701

PDF: PhysRevLett.121.102701


論文出版:THz FEL のための電子銃開発

投稿日: 2018年7月13日

Development of a Multialkali Photocathode Dc Gun for a Smith-Purcell Terahertz Free-Electron Laser

Nobuyuki Nishimori, Ryoji Nagai, Masaru Sawamura and Ryoichi Hajima

Particles 2018, 1(1), 166-174 - Published: 13 July 2018

We have developed a photocathode dc gun for a compact Smith-Purcell free-electron laser in the terahertz wavelength region. The gun system consists of an alkali antimonide photocathode preparation chamber, a dc gun with a 250 kV-50 mA Cockcroft-Walton high-voltage power supply, and a downstream beamline with a water-cooled beam dump to accommodate a beam power of 5 kW. We fabricated a Cs3Sb photocathode with quantum efficiency of 5.8% at a wavelength of 532 nm and generated a 150 keV beam with current of up to 4.3 mA with a 500 mW laser. A vacuum chamber for the Smith-Purcell free-electron laser has been installed in the downstream beamline. We describe the present status of our work.

DOI: https://doi.org/10.3390/particles1010012



投稿日: 2018年6月28日

Geant4 physics process for elastic scattering of  -rays

Mohamed Omer and Ryoichi Hajima

原子核蛍光共鳴散乱(NRF)は、核物質の非破壊検査(NDA)において有用な技術である。NRFは同位体に固有のエネルギーをもった 線と物質の相互作用であることから、同位体を識別したNDAを実現できる。しかしながら、NRFと競合する他の光核相互作用が存在し、そのため、NRFによるNDAの測定性能が制限される可能性がある。競合する相互作用のうち原子核による 線の弾性散乱(デルブリュック散乱)は、これまでのモンテカルロコードでは考慮されていなかった。日本原子力研究開発機構では、平成27年度からNRFに基づくNDAシステムの開発プログラムを開始し、その一環として 線の弾性散乱がNRF測定に及ぼす影響を評価するために、Geant4に 線の弾性散乱を追加するためのコードを新規に開発した。今回刊行するJAEA-データ/コードレポートでは、シミュレーションコードの詳細な説明と、コード入力に用いた 線弾性散乱断面積、および、コードの検証と妥当性確認に用いた計算結果を示す。このレポートを公開することで、当該コードの信頼性向上に必要なユーザーからのフィードバックの機会が得られる。本研究は文部科学省の核セキュリティ強化等推進事業費補助金の支援を受けた。

報告書番号 : JAEA-Data/Code 2018-007
ページ数 : 32 Pages
発行年月 : 2018/06
PDF :  JAEA-Data-Code-2018-007.pdf:2.64MB
論文URL :  http://dx.doi.org/10.11484/jaea-data-code-2018-007



投稿日: 2018年1月12日

95gTc and 96gTc as alternatives to medical radioisotope 99mTc

Takehito Hayakawa, Yuichi Hatsukawa, Toru Tanimori
Heliyon 3 (2017) e00497.
doi: 10.1016/j.heliyon.2017.e00497 (open access)

医学診断用として広く用いられている放射性同位元素 99mTcの代替として、95gTcおよび96gTcが利用可能であることを示し、その製造方法を提案しました。



投稿日: 2017年11月27日

Properties of the RF transmission line of a C-shaped waveguide

Masaru Sawamura, Masato Egi, Kazuhiro Enami, Takaaki Furuya, Hiroshi Sakai, KenseiUmemori

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume 882, 21 February 2018, Pages 30-40

A new type of waveguide, named the C-shaped waveguide (CSWG), has a structure similar to that of a coaxial line but with a plate connecting the inner conductor to the outer conductor. The CSWG has unique characteristics, such as a cutoff frequency and easy cooling of the inner conductor, that are absent in the coaxial line. The results of calculations using 3-dimensional simulation software and measurement with the CSWG model are in good agreement with the analytical solution. The CSWG can be applied to a pickup port with a high-pass filter that can attenuate the higher-order modes over the cutoff frequency without attenuating the accelerating mode.


accepted manuscript PDF


投稿日: 2017年11月20日

Generating Carrier-Envelope-Phase Stabilized Few-Cycle Pulses from a Free-Electron Laser Oscillator

Ryoichi Hajima and Ryoji Nagai

Phys. Rev. Lett. 119, 204802 – Published 15 November 2017

We propose a scheme to generate carrier-envelope-phase (CEP) stabilized few-cycle optical pulses from a free-electron laser oscillator. The CEP stabilization is realized by the continuous injection of CEP-stabilized seed pulses from an external laser to the free-electron laser oscillator whose cavity length is perfectly synchronized to the electron bunch repetition. Operated at a midinfrared wavelength, the proposed method is able to drive a photon source based on high harmonic generation (HHG) to explore the generation of isolated attosecond pulses at photon energies above 1 keV with a repetition of >10  MHz. The HHG photon source will open a door to full-scale experiments of attosecond x-ray pulses and push ultrafast laser science to the zeptosecond regime.

DOI: https://doi.org/10.1103/PhysRevLett.119.204802

PDF: PhysRevLett.119.204802



投稿日: 2017年10月27日

Low-lying dipole strength in 52Cr

T. Shizuma, T. Hayakawa, I. Daito, H. Ohgaki, S. Miyamoto, and F. Minato

Phys. Rev. C 96, 044316 – Published 13 October 2017

DOI: https://doi.org/10.1103/PhysRevC.96.044316

published manuscript


投稿日: 2017年10月27日

Compton Scattering of Gamma-Ray Vortex with Laguerre Gaussian Wave Function

Tomoyuki MaruyamaTakehito HayakawaToshitaka Kajino (Submitted on 25 Oct 2017)

In this work, we report calculation for Compton scattering of a gamma-ray vortex with Laguerre Gaussian wave function on an electron in the framework of the relativistic quantum mechanics. We have found the following unexpected feature. The momentum of scattered photon distributes outside of the reaction plane determined by the incident photon and the scattered electron, and hence the energy of the scattered photon also distributes. This novel result indicates that one can identify a gamma-ray vortex by measuring coincidentally the scattered angles of the electron and photon.

Comments: 9 pages, 3 figures
Subjects: High Energy Physics – Phenomenology (hep-ph)
Cite as: arXiv:1710.09369 [hep-ph]
  (or arXiv:1710.09369v1 [hep-ph] for this version)



投稿日: 2017年10月19日

Construction and commissioning of the compact energy-recovery linac at KEKs

Mitsuo Akemoto, DaiArakawa, Seiji Asaoka, Enrico Cenni, Masato Egi,
Kazuhiro Enami, Kuninori Endo, Shigeki Fukuda, Takaaki Furuya, Kaiichi Haga,
Ryoichi Hajima, Kazufumi Hara, Kentaro Harada, Tohru Honda, Yosuke Honda,
Teruya Honma, Kenji Hosoyama, Eiji Kako, Hiroaki Katagiri, Hiroshi Kawata,
Yukinori Kobayashi, Yuuji Kojima, Yoshinari Kondou, Olga Tanaka,
Tatsuya Kume, Masao Kuriki, Hiroshi Matsumura, Hideki Matsushita,
Shinichiro Michizono, Takako Miura, Tsukasa Miyajima, Shinya Nagahashi,
Ryoji Nagai, Hirotaka Nakai, Hiromitsu Nakajima, Norio Nakamura,
Kota Nakanishi, Kazuyuki Nigorikawa, Nobuyuki Nishimori,
Takashi Nogami, Shuichi Noguchi, Takashi Obina, Feng Qiu, Hidenori Sagehashi,
Hiroshi Sakai, Shogo Sakanaka, Shinichi Sasaki, Kotaro Satoh, Masaru Sawamura,
Miho Shimada, Kenji Shinoe, Toshio Shishido, Mikito Tadano, Takeshi Takahashi,
Ryota Takai, Tateru Takenaka, Yasunori Tanimoto, Takashi Uchiyama,
Akira Ueda, Kensei Umemori, Ken Watanabe, MasahiroYamamoto

Nuclear Instruments and Physics Research A Volume 877, 1 January 2018, Pages 197-219 DOI: 10.1016/j.nima.2017.08.051
accepted manuscript PDF published manuscript (free download until Dec. 5, 2017) PDF

Energy-recovery linacs (ERLs) are promising for advanced synchrotron light sources, high-power free electron lasers (FELs), high-brightness gamma-ray sources, and electron–ion colliders. To demonstrate the critical technology of ERL-based light sources, we have designed and constructed a test accelerator, the compact ERL (cERL). Using advanced technology that includes a photocathode direct current (DC) electron gun and two types of 1.3-GHz-frequency superconducting cavities, the cERL was designed to be capable of recirculating low emittance (1 mm mrad) and high average-current (10 mA) electron beams while recovering the beam energy. During initial commissioning, the cERL demonstrated successful recirculation of high-quality beams with normalized transverse emittance of 0.14 mm mrad and momentum spread of 1.2 10−4 (rms) at a beam energy of 20 MeV and bunch charge below 100 fC. Energy recovery in the superconducting main linac was also demonstrated for high-average-current continuous-wave beams. These results constitute an important milestone toward realizing ERL-based light sources.



投稿日: 2017年8月25日

Measurement of deflection on germanium and gold prisms using 1.7 MeV laser Compton scattering γ-rays

T. Kawasaki, S. Naito, Y. Sano, T. Hayakawa, T. Shizuma, R. Hajima, S. Miyamoto Physics Letters A, Volume 381, Issue 36, 25 September 2017, Pages 3129-3133 https://doi.org/10.1016/j.physleta.2017.07.030 (Open Access)

We measured the refractive index of germanium and gold prisms at 1.7 MeV to explore if there are refractive index enhancements to 6th power of atomic number due to high order nonlinear process of Delbrück scattering in quantum electrodynamics. We measured the deflection by prisms using imaging plates and laser Compton scattering γ-rays with linear and random polarization. We used crystal and polycrystalline prisms for Au. The measured upper limit of the refractive index, δ, for crystal Ge, crystal Au, or polycrystal Au prisms is 4.0 x 10-8, 2.9 x 10-7, or 2.4 x 10-7. We could not find any signature for high order nonlinear process. This result does not support the hypothesis suggested by Habs et al. (2012)

2012 年に出版された論文にて、Habs らがSiプリズムにおける MeV エネルギーのガンマ線屈折に異常な振る舞いがあることを報告し、デルブリュック散乱の高次効果による可能性を示唆しました。われわれは、レーザーコンプトン散乱ガンマ線を使った実験を行い、金とゲルマニウムの屈折率を測定し、検出限界の範囲内でデルブリュック散乱の高次効果が見られないことを確認しました。

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