Numerical simulation of a high-brightness lithium ion gun for a Zeeman polarimetry on JT-60U

JT-60Uにおけるゼーマン偏光計測のための高輝度リチウムイオン銃の数値計算

小島 有志; 神谷 健作; 井口 春和*; 藤田 隆明; 鎌田 裕

Kojima, Atsushi; Kamiya, Kensaku; Iguchi, Harukazu*; Fujita, Takaaki; Kamada, Yutaka

本研究はJT-60Uにおける高空間分解能周辺電流分布計測を目指したゼーマン偏光計測のための高輝度リチウムビーム源の開発を目的とする。JT-60Uにおけるリチウムビーム計測配位はイオン銃から観測領域まで6m離れており、イオン銃の性能としては引き出し電流値よりもビーム発散角が重要なパラメーターとなる。本発表では今回製作した高輝度リチウムイオン銃の配位を用いて空間電荷を考慮した軌道計算を行い、引き出したビームの特性、特にイオン発生分布の違いが与える影響を評価した結果を報告する。

A lithium ion gun is under construction for a lithium beam Zeeman polarimetry on JT-60U. The performance of the prototype ion gun has been estimated by the numerical simulation taking the space charge effects into account. The target values of the ion gun are the beam energy of 30 keV, the beam current of 10 mA and the beam divergence angle within 0.13 degrees. The low divergence is required for the geometry of the Zeeman polarimetry on JT-60U where the observation area is 6m away from the neutralizer. The simulation results show the beam loss of 50% caused by the clash to the electrode such as an cathode and the neutralizer. Moreover, the beam transport efficiency from the neutralizer to the observation area is low due to the broadening of the divergence angle. The total beam efficiency is about 5%. Extracted current profile affects the beam property and efficiency. The peaked profile achieves better efficiency than the hollow one. As a result, beam current of 1mA is obtained at the observation area by the simulation for the prototype ion gun.