Development of $\hbox {H}^{-}$ multicusp ion source

Abstract

Introduction

 The ion source is one of the key devices for the high-intensity cyclotron, which exerts influence on the beam intensity and applications of the machine. This paper will provide an introduction to current measures and present relevant experimental study as well as the beam test results.

Purpose

 The existing ion source of the accelerator has a 2-mA output current. Our aim is to increase the current to roughly 5 mA to decrease the reaction time of cyclotron. Therefore, a new ion source was developed. To this end, some simulations were performed, and the simulated ion source was constructed, and then some measurements were noted.

Methods and materials

 The CST code is used to simulate the chamber and extraction system. For construction, some materials such as copper and stainless steel are used. Tungsten wire of 2.1 mm diameter was developed to reach high beam current. Turbo and rotary pump is chosen for system evacuation. Faraday cup can be used for readout. The magnets for plasma confinement are made of Nd–Fe–B material.

Results

 The source assembly consists of a tubular plasma chamber (inner diameter: 100 mm; length: 150 mm) with 12 columns of permanent magnets (Nd–Fe–B material) to provide a stronger multicusp field, a three-electrode extraction system, and a top cover with a confinement magnet inside. Now, 5 mA $\hbox {H}^{-}$ beam can be extracted from the ion source with a plasma electrode aperture of 13 mm under an arc power of 6 kW. The optimum $\hbox {H}_{2}$ gas flow rate and the change of pressure found during the tuning process of the ion source are presented.