• R.F. Welton, S.N. Murray, M.P. Stockli
  ORNL, Oak Ridge, Tennessee
• R. Keller
  LBNL, Berkeley, California

The ion source developed for the Spallation Neutron Source* (SNS) is a radio frequency, multi-cusp source designed to produce ~ 40 mA of H^- with a normalized rms emittance of less than 0.2 pi mm mrad. To date the source has been utilized in the commissioning of the SNS accelerator, delivering beams of 10^-50 mA with duty-factors of typically ~0.1% for operational periods of several weeks and availabilities now ~99%. Ultimately the SNS facility will require beam duty-factors of 6% (1 ms pulse length, 60 Hz repetition rate, 21 day run-period). Over the last year, several experiments were performed in which the ion source was continuously operated at full duty-factor and maximum beam current on a dedicated test stand. Recently, a breakthrough in our understanding of the Cs release process has led to the development of a new source conditioning technique which resulted in a dramatic increase in beam persistence with time. Average H^- beam attenuation rates have been improved from ~5 mA/day to ~0.4 mA/day, allowing beams in excess of 30 mA to be delivered continuously at full duty factor for periods of ~20 days. Prior to this development, full duty factor beams could only be sustained for periods of several hours.