Power-Balance Control by Slug Tuner for the 175MHz Radio-Frequency Quadrupole (RFQ) Linac in IFMIF Project

Abstract

RF Power-balance control among the quadrants of IFMIF 4-vane radio-frequency quadrupole (RFQ) linac structure is a critical issue, because it may be affected by the fabrication error of the 12m-long RFQ and by the perturbation due to loop antenna installation. The power-balance controllability of slug tuners was measured by a low power test, and the distortion behavior of electric fields profiles at beam bore peripheral was calculated by an electromagnetic field simulation code. From the low power test, it was found that RF power-balance up to 80% can be controlled without overlap of modes. The calculation suggested that the design requirement of distortion limit of 1% can be attained by employing 1cm slug tuner with insertion depth of 1cm or less.