Over 7200 hours commissioning of RF-driven negative hydrogen ion source developed at CSNS

Abstract

The China Spallation Neutron Source project Phase-II (CSNS-II) aims to deliver a proton beam of 500 kW on the tungsten target. To accomplish this goal, an RF-driven negative hydrogen ion source was developed to replace the penning ion source used in CSNS-I. The RF-driven ion source has been put into commissioning on CSNS accelerator since September 8th, 2021. And it was shut down on July 26th, 2022, together with the whole accelerator for the annual maintenance in summer. In this run cycle it has accumulated service time of over 7200 hours without major maintenance. The availability of the ion source is above 99.99%, except for one or two sparks per day of the 50 kV high voltage platform, each spark causing 1 second trip of the accelerator. The RF-driven ion source has an external antenna winding around a silicon nitride plasma chamber, which is quite robust in high duty-factor operation. In this paper, we present the structure of the ion source, the improvements over other ion sources, and the issues met in the commissioning.