H- Ion Source Development for the FNAL 750keV Injector Upgrade

TL;DR

This paper reports on the development and testing of a new H- ion source for FNAL's 750keV injector upgrade, emphasizing improved reliability, efficiency, and beam quality based on a magnetron design from BNL.

Contribution

It introduces a magnetron H- ion source with enhanced reliability and efficiency for the FNAL injector upgrade, including detailed performance data and operational experience.

Findings

Produces 90mA H- beam at 15Hz with 0.38% duty cycle

Achieves 60mA/kW power efficiency at 35kV extraction

Demonstrates reliable operation with 6-9 months lifetime

Abstract

The new FNAL 750keV injector upgrade for the replacement of the 40 year old Fermi National Laboratory (FNAL) Cockcroft-Walton accelerators with a new ion source and 200MHz Radio Frequency Quadrupole (RFQ), Low Energy Beam Transport (LEBT) and Medium Energy Beam Transport (MEBT), has been built and is now being tested prior to installation during the 2012 shutdown. The new H- ion source is a round aperture magnetron which was developed at Brookhaven National Lab (BNL) by Jim Alessi. Operational experience from BNL has shown that this type of source is more reliable with a longer lifetime (on the order of 6 to 9 months) due to better power efficiency. With a similar duty factor to BNL, we expect to have a comparable lifetime between source changes. The new source design reliably produces 90mA of H- beam current at 15Hz rep-rate, 250 \mu s pulse width, and a duty factor of 0.38%. The measured emittances at the end of the LEBT are horizontally \epsilon H = 0.21\pi mm* mrad and vertically \epsilon v = 0.17\pi mm* mrad. With 35kV extraction the power efficiency is 60mA/kW. The source design, along with data from a test stand and the LEBT, will be presented in this paper.