Internal electrostatic confinement fusion (慣性静電閉じ込めによる核融合) 論文紹介 by 白鳥昂太郎 Paper Institute Institute of Advanced Energy, Kyoto University Prof. Kiyoshi Yoshikawa's Research Group 京都大学エネルギー理工学研究所 エネルギー 生成研究部門 粒子エネルギー研究分野 吉川 潔 研究室 http://www.iae.kyotou.ac.jp/beam/index_j.html Brief introduction of Internal electrostatic confinement fusion : IECF IECF is the scheme of injecting the ions and electrons towards the spherical center, trapping both species in the electrostatic self-field and giving rise to fusion in the dense core. (Fusion mechanism is not completely understood.) For effective production of neutron, multi-well potential is needed. Energy of neutron d+d→3He+n : 2.5 MeV d+t→4He+n : 14.1 MeV (d+3He→4He+p : 14.7 MeV) Background The concept of IECF is conceived in 1950s. The first purpose is to investigate the room temperature fusion system (for power source ?). →Not realistic… →Latest type, input 100W ⇔Output by fusion 1μW But… IECF is a good neutron source. → Investigation is continued. The Machine Intensity of neutron d+d→3He+n : 2.5 MeV → 5×106 n/s (High voltage and ion current are unknown) Advantage of IECF compared with neutron source (example 252Cf) Mono-energetic spectrum No decreasing by particle decay Easy to operate Energy spectrum of neutron from Cf Able to use proton source O.I. Batenkov et al., INDC(NDS)-146,(1983) 252 (d+3He→4He+p : 14.7 MeV) Good application Purpose of this paper To measure ion current dependency of neutron yield (N∝I2) for investigating IEFC mechanism To explain mechanism by theoretical calculation for offering the technical advantages ↑ The structure of internal potential is unknown. → fusion mechanism Information for developing the technical progress : To optimize high voltage, current and to develop cooling system →Technical advantages Ion current dependency of neutron yield Calculation by multi-well potential: N∝I2 (I=ion current) ⇔Experimental result: scales linearly I Limitation of high voltage and current are 70kV and 15 mA, respectively. Not to exceed the threshold for multi-well potential Perveance : I(mA)/V1.5(kV) > 2.2 Re-experiment by sufficient condition by using pulse current I2 dependency over the threshold was confirmed. Result of theoretical calculation To construct the program by multiwell potential and to simulate the dependency of ion current N∝I3 dependency exists in the high current region. →Increased ion current make multi-well potential unstable and this unstably increase the density of central region. ⇒The experiment to confirm this dependency in the high current region should be performed. Result of theoretical calculation To construct the program by multiwell potential and to simulate the dependency of ion current N∝I3 dependency exists in the high current region. →Increased ion current make multi-well potential unstable and this unstably increase the density of central region. ⇒The experiment to confirm this dependency in the high current region should be performed. Conclusion The dependency of ion current (N∝I2) by multi-well potential is confirmed. There may be the dependency N∝I3 in the high ion current region. → The experiment should be performed. Progress after this experiment Multi-well potential was first measured by the laser-induced fluorescence method. To increase the nuetron intensity of DD reaction → 2×108 n/s Future plan Improvement of ion source Glow discharge ＋ Magnetron ion source Intensity of neutron will be increased by one-order (108→109 n/s). Application Examples Mine sweeper Development with 7 organizations They plan to operate this machine in Afghanistan. Why neutron source ? It is very difficult to distinguish mine from other metals by metal detector. → mine/metals = 1/1000 under the ground →The plastic and ceramic mine cannot be detected. The composition of TNT is known. →By measuring γ ray from TNT reacted with neutron and back scattered neutron by proton in TNT, we will be able to distinguish mine from other metals. What detect ? γ ray from neutron capture : 1H(n,γ), 14N(n,γ) Energy 1H(n,γ) : 2.22 MeV 14N(n,γ) : 10.8 MeV CsI, NaI, BGO for detection 10.8 MeV → Detected by BGO multi compton gamma camera BGO gamma compton camera Expected performance (1m×1m field, 20cm depth, 30 g mine) ～106 n/cm2/s Efficiency 99.9% Miss identify 40% @ 10 min Other method 回転する鎖で地面をひたすら叩いて、 片っ端から爆発させる Summary Present performance of IECF : 2×108 n/s. IECF will be able to be used for several applications by adjusting neutron intensity. Mine sweeper with IECF is planned.
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