RF and field measurements of the SSC-LINAC RFQ

The 53.667 MHz continuous-wave heavy ion RFQ has been designed and manufactured for the SSC-LINAC project. This four-rod RFQ accelerates ions with maximum mass to charge ratio of 7 from 3.728 keV/u to 143 keV/u. Measurements have been carried out to check the RF performance of the cavity and the quality of the electric field. The S₁₁ of the power coupler is adjusted to better than ?44 dB, and the Q ₀ of the cavity is 6440. The quality of the electric field is evaluated by the perturbation method. The measurement procedure and data analysis will be discussed in detail. The error due to gravity of the perturbation bead has been corrected by averaging the fields in different quadrants. As a result, the unflatness of the electric field is ±2.5%, and the dipole field component distributes from 0% to 20% in different longitudinal positions, which indicates the asymmetry of the quadrupole field. The unflatness of the quadrupole field distribution represents a good agreement with the simulation results. High power RF test and beam commissioning of the RFQ are on schedule in early 2014.