京都大学 · 物理学・天文学
Mahmoud Bakr教授の研究室では、核融合素子を用いた中性子源の開発とその応用を柱として、インエルーシブ・エレクトロスティック・コンfinメント(IEC)装置を用いた核融合反応の最適化や、中性子生成率の向上に向けた電極材料の特性評価を行っています。また、放射線遮蔽材料の選定や、熱電子銃におけるバックバンディング効果のシミュレーション、蛍光体材料のトラップパラメータ解析など、核物理・材料工学・放射線工学の分野を横断した研究が展開されています。特に、小型核融合装置を用いた多用途放射線源の実用化に向けた基盤技術の確立が目指されています。
Figures are computed from collected data and may differ slightly.
Thermoluminescence (TL) properties of La<sub>2</sub>O<sub>3</sub>: Dy<sup>3+</sup>, Li<sup>+</sup>, and La<sub>2</sub>O<sub>3</sub>: Eu<sup>3+</sup>, Li<sup>+</sup>, exposed to 5.12 Gy of beta radiation, and recorded at different heating rates 0.5, 1, 2, 3, 4, and 5 °C s<sup>-1</sup> (from Molefe et al., paper 2019), were analyzed and the trap parameters were determined in this study. These parameters include the order of kinetics <i>b</i>, the activation energy <i>E</i> (eV), the frequency fact
Neutrons are generated in the inertial electrostatic confinement (IEC) device through different types of fusion reactions of the fuel gas such as deuterium (D) and tritium (T). Fusion in the IEC device takes place via various kinds of collisions like beam-beam collision, beam–background gas collision, and beam-target collision on the electrode surfaces. Two identical anodes for the IEC chamber made from titanium (Ti) and SUS-316L stainless steel (SS) are used to study the effect of the anode mat
An inertial electrostatic confinement (IEC) fusion device accelerates ions, such as deuterium (D) or tritium (T), to produce nuclear fusion and generate neutrons. The IEC's straightforward configuration consists of a concentric spherical transparent cathode at a negative bias surrounded by a grounded spherical anode. The effects of cathode properties on the neutron production rate (NPR) remain, to date, inadequately studied. This study aims to determine the impact of the cathode material on the
Thermionic emission performance from single crystals of CeB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> and LaB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> was investigated at different operational loads using a test machine, in order to consider CeB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> as a cathode for thermionic
The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode's temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (${\mathrm{LaB}}_{6}$) thermionic rf gun cathodes. For each, particle simulation codes are used to simulate the BB effect and electron beam dyn
A radiation source based on the inertial electrostatic confinement fusion (IECF) system is being developed for multidisciplinary research applications. The radiation outputs from the IECF system are 2.45 MeV fast neutrons and the associated co-generated X-rays with an energy less than 3 MeV. A radiation shielding study has been performed on five types of concrete to define the most efficient material for the shielding design of the system. The proposed materials were ilmenite-magnetite concrete
The emission properties of CeB6 compared to LaB6 thermionic cathodes have been measured using an electrostatic DC gun. Obtaining knowledge of the emission properties is the first step in understanding the back-bombardment effect that limits wide usage of thermionic radio-frequency electron guns. The effect of back-bombardment electrons on CeB6 compared to LaB6 was studied using a numerical simulation model. The results show that for 6 μs pulse duration with input radio-frequency power of 8 MW, C
Trapping ions, such as deuterium and tritium, inside a potential well to generate neutrons is a well-established technology through electric and magnetic fields via the inertial electrostatic confinement fusion (IECF) and the tokamak, respectively. In the IECF, the straightforward configuration is a concentric cathode connected to a negative bias, surrounded by a grounded anode that serves as a vacuum vessel. Theoretically, neutrons are generated inside the vessel through fusion between ions tha
We are developing, the first of its type, a portable active interrogation system for special nuclear materials (SNMs) detection such as U-235 and Pu-239. The system is based on the recently developed technique, threshold energy neutron analysis (TENA) method. Mandatory aspects for the neutron generator to be used for on-site inspection as well as for container screening at ports of entry is intense neutron as 5×107 n/s neutron yield in a very compact configuration such as ∼25 cm diameter, 60 cm
Abstract Herein, we employ the threshold energy neutron analysis (TENA) technique to introduce the world's first active interrogation system to detect special nuclear materials (SNMs), including U-235 and Pu-239. The system utilizes a DD neutron generator based on inertial electrostatic confinement (IEC) to interrogate suspicious objects. To detect secondary neutrons produced during fission reactions induced in SNMs, a tensioned metastable fluid detector (TMFD) is employed. The current status of
The effect of back-bombardment (BB) electrons is considered one of the main obstacles for extensive use of thermionic RF guns (T-RF). The 10 hexaboride materials named (Ca, Sr, Ba, La, Ce, Pr, Nd, Sm, Eu, and Gd) B6 are investigated in this paper to survey the effect of the cathode material on reducing BB electrons and compare them with LaB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> (which is widely used as a thermionic cathode). A nume
In this investigation, the impact of water thickness and various types of concrete materials, each characterized by different densities and elemental compositions, is examined for their role in shielding a radiation generator based on Inertial Electrostatic Confinement Fusion (IECF) device. The study focuses on assessing several vital parameters, including the effective removal cross-section (∑ Rt ) for fast neutrons, total mass attenuation coefficients (μ mt ), linear attenuation coefficients (
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