Construction of a variable-frequency radio-frequency quadrupole linac for the RIKEN heavy-ion linac

Abstract

A new type of variable-frequency radio-frequency quadrupole (RFQ) linac has been constructed as a new preinjector for the RIKEN heavy-ion linac (RILAC). The RFQ resonator, based on a folded-coaxial structure with a movable shorting plate, is compact even in a low frequency region below 20 MHz. It accelerates ions with mass-to-charge ratios of 5.3 to 26.4 in the energy range up to 450 keV per charge, by varying its resonant frequency from 17.4 to 39.0 MHz. Moreover, the power loss is small in the low frequency region; the rf power consumption in cw mode is 7 kW at 17.4 MHz, and it increases to 30 kW at 39.0 MHz at the maximum intervane voltage of 36.8 kV. We initiated this project in 1991, and installed the new preinjector consisting of an electron cyclotron resonance ion source of 18 GHz and this RFQ in 1996. Since the installation, the beam intensity has become larger by more than 1 order of magnitude than that formerly obtained with the Cockcroft–Walton preinjector. Recently, the maximum power of the beam extracted from the RILAC and that from the ring cyclotron has reached 560 W and 2 kW, respectively.

Experiments on searching for the heaviest elements

“…Ion source used is a 18GHz ECR Ion Source [12]. [12], RFQ-Linac [14], Original Linac [13], Booster ?Linac CSM [15], and a gas-filled recoil ion separator GARIS are shown.…”

“…The accelerator consists of three Linac, a frequency tunable RFQ-Linac [14], the original heavy ion Linac [13], and a booster Linac (CSM) [15]. A gas-filled recoil ion separator GARIS is used as a recoil separator.…”