DEVELOPMENT OF AN SCRFQ HEAVY-ION LINAC FOR RI BEAMS

A split coaxial RFQ (SCRFQ) is being developed to accelerate RI beams from 1 to 170 KeV/u as part of the Japanese Hadron Project (JHP). Our SCRFQ is equipped with modulated vanes. On the basis of the studies on a cold model and a proton accelerating one, a 25.5 MHz prototype for the JHP SCRFQ has been constructed. The prototype, consisting of three module cavities, is 2.1 m in length and 0.9 m in inner diameter, and accelerates ions with a charge-to-mass ratio (q/A) greater than 1/30 from 1 to 45.4 keV/u. The unloaded Q-value of the cavity is 6400, corresponding to about 84% of the calculated value, and the field imbalance between vanes is within +/- 0.6%. The designed intervane voltage of 109 kV for ions with q/A = 1/30 is achieved with a 70 kW peak power. By using ions of three species, N2+, N+ and Ne+, acceleration tests are conducted. The transmission efficiency attained with a N+ beam is better than 80% at normalized intervane voltages higher than 1.2.