Development of a new J-PARC-made internal antenna for the J-PARC RF-driven H− ion source

Abstract

We have been conducting the test of a new J-PARC-made internal antenna for the J-PARC RF-driven cesiated H− ion source. During the test of high-density plasma production by the antenna, we monitored the outgassing characteristics of the antenna by measuring the mass spectrum of the source gas and optical emission spectrum of the plasma. It is confirmed that no remarkable impurities were detected from the new antenna. The observed emittances of the H− beam extracted by using the new antenna were similar to those by using the SNS-made antenna. To accelerate the endurance test of the new antenna, we applied the antenna for the high-density plasma production to the 5% duty factor (1 ms pulse width with 50 Hz repetition rate) with the 2 MHz RF input power of approximately 60 kW at the ion source test stand. These values are much higher than those in the J-PARC nominal operation; 0.8 ms pulse width with 25 Hz repetition rate (the duty factor of 2%) with the RF input power of approximately 30 kW. The paper describes the results of the characteristics of the new J-PARC-made antenna.