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Numerical Simulation of a High-Brightness Lithium Ion Gun for a Zeeman Polarimetry on JT-60U

Atsushi KOJIMA, Kensaku KAMIYA, Harukazu IGUCHI¹⁾, Takaaki FUJITA and Yutaka KAMADA

Japan Atomic Energy Agency, Naka, Ibaraki 311-0193, Japan

1)

National Institute for Fusion Science, Toki, Gifu 509-5292, Japan

(Received 4 December 2006 / Accepted 16 May 2007 / Published 20 November 2007)

Abstract

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 of 0.13 degrees is required for the geometry of the Zeeman polarimetry on JT-60U where the observation area is 6.5 m away from the neutralizer. The numerical simulation needs to be carried out for the design study because the requirement of the divergence angle is severe for the development of the high-brightness ion gun. The simulation results show the beam loss of 50 % caused by the clash to the electrode such as the 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 beam profile affects the beam focusing and the efficiency. The peaked profile achieves better efficiency than the hollow one. As a result, beam current of 1 mA is obtained at the observation area by the simulation for the prototype ion gun.

Copyright (c) 2007 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

plasma and fusion, lithium beam, beam probe, ion gun, JT-60U

DOI: 10.1585/pfr.2.S1104

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This paper may be cited as follows:

Atsushi KOJIMA, Kensaku KAMIYA, Harukazu IGUCHI, Takaaki FUJITA and Yutaka KAMADA, Plasma Fusion Res. 2, S1104 (2007).