• K.R. Shin, Y.W. Kang, S.-H. Kim, A.V. Vassioutchenko
  ORNL, Oak Ridge, Tennessee
• A.E. Fathy
  University of Tennessee, Knoxville, Tennessee

In radio frequency quadrupole (RFQ) structures, the fundamental quadrupole mode is used for focusing and acceleration of ion particles. The fields are maintained to have negligible interference with other unwanted modes of the structure using mode suppressors of different types especially in vane type RFQs that require dipole mode separation. The field distribution on the beam axis is usually measured and referenced using multiple loop-type magnetic probe antennas on the wall along the structure. Since the structures are equipped with many slug tuners on the outer wall for correction of fields, the tuner-probe interference can be a concern. In order to investigate the mode separation properties of the commonly used mode suppressors and the accuracies in field distribution with respect to localized perturbation due to the tuners, a systematic 3D simulation was carried out using a full-scale model of the SNS RFQ.

• Y.W. Kang, R.E. Fuja, T.W. Hardek, S.W. Lee, M.P. McCarthy, M.F. Piller, K.R. Shin, M.P. Stockli, A.V. Vassioutchenko, R.F. Welton
  ORNL, Oak Ridge, Tennessee

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is in the process of ramping up the H^- ion beam power to 1.4 MW, its full design power for the neutron production. For robust operation of the neutron facility, work is underway for various improvements on the RF power systems of the ion source. For short and long-term higher beam power operations, an RF-driven H^- ion source employing external antenna with a water-cooled, ceramic aluminum nitride (AlN) plasma chamber has been developed*. The new ion source has been tested to deliver up to 42 mA in the SNS Front End (FE) and unanalyzed beam currents up to ~100mA (60Hz, 1ms) in the ion source test stand. In addition to the external antenna design for improved antenna lifetime, other RF developments for improvement of reliability are running 2 MHz power amplifier system is with isolation transformer, employing full solid-state 2 MHz power amplifier, more precise 2 MHz capacitive impedance matching, and upgrading 13 MHz RF plasma gun system. This paper discusses the engineering solutions with analysis and development of the above RF systems for the new ion source system.

R.F. Welton, N.J. Desai, J. Carmichael, B. Han, Y.W. Kang, S.N. Murray, T. Pennisi, M. Santana, and M.P. Stockli, "The Continued Development of the SNS External Antenna H^- Ion Source," ICIS2009