Operating experience with a 100-keV, 100-mA H− injector

Abstract

According to beam dynamics calculations it should be possible to accelerate a high‐perveance beam in a radio‐frequency quadrupole (RFQ) accelerator with low emittance growth and nearly 100% capture efficiency. A 100‐mA, 100‐keV H− ion injector with a 5‐Hz, 1‐ms duty factor was built for use with this accelerator, but the beam emittance at 100 keV was found to be two to four times the value previously determined at 20 keV. This emittance growth was traced to the 20‐keV beam transport, where an instability occurred in the background plasma created by beam ionization of the residual gas. The injector has been rebuilt with a shorter transport length, resulting in greatly reduced emittance growth.