Nuclear Instruments and Methods in Physics Research A328 (1993) 251-254 North-Holland NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH Secbon A Fabrication and test of a superconducting RFQ A. Jain 1, H. Wang 1, I. Ben-Zvi ~, P. Paul and J.W. No~ Department of Physics, SUNY at Stony Brook, Stony Brook, N Y 11794-3800, USA A. Lombardi 1NFN-LNL, Via Romea 4, Legnaro (PD) 1-35020, Italy The fabrication and first performance tests of a prototype superconducting radio-frequency quadrupole resonator (SRFQ) are described. The SRFQ operates at 57 MHz and is optimized for a particle velocity of /3 = 0.033. It is constructed of copper electroplated with a lead-tin alloy. An accelerating field gradient of 1.25 MV/m was achieved with about 7 W of helium dissipation. This corresponds to an energy gain of 700 keV per unit charge over the 56 cm overall diameter of the resonator. 1. Introduction A superconducting radio-frequency quadrupole (SRFQ) would be very useful for the continuous (cw) acceleration of low-velocity heavy-ion beams since it would combine the efficient acceleration and intrinsic focussing of the RFQ with very modest power dissipa- tion. A recent paper [1] has described an SRFQ pre- accelerator for boosting ions as heavy as Pb from an ECR source up to /3 ~ 0.05 for injection into a super- conducting linac. The proposed design breaks the long classical RFQ into a series of compact independent elements each optimized (by proper choice of modula- tion parameter m and aperture a) for maximum accel- eration per unit surface field over a particular velocity range. The present paper describes the fabrication and first superconducting tests of the third of six elements described in ref. [1]. Further details of the SRFQ design and fabrication can be found in other confer- ence papers [2,3] and a thesis [4]. four curved electrode support tubes (4 cm diam) and two spheres (12 cm diam). These two vane subassem- blies are in turn suspended from the reinforced top plate of the outer container by two large (8 cm diam) hanging tubes. Beam enters and leaves the resonator through large beam ports with 32 mm openings. The 2. Description The prototype SRFQ resonator is shown in fig. 1. The active elements of the structure are the four steeply modulated (m = 4) 40 cm long vanes surround- ing the beam axis (minimum aperture radius a = 15.7 ram). The two pairs of diagonally opposed vanes of the same electrical polarity are interconnected through ~o~ Present address: Brookhaven National Laboratory, Upton, NY 11973, USA. Fig. 1. Cut-away view of the prototype SRFQ. The overall size is about 0.6 x 0.6 m. 0168-9002/93/$06.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved III. BOOSTERS, RF CAVITIES