Rfq Linac Commissioning and Carbon4+ Acceleration for Ag15+ Acceleration via Direct Plasma Injection Scheme

Various species of high intensity highly charged state heavy ion beams with small emittance are required in many fields including particle physics, medical uses, inertial fusion, and simulator of space radiations. Direct Plasma Injection Scheme (DPIS), we have developed for several years, is a unique scheme to provide heavy ion beams to meet the above requirements. A high-density plasma created by a laser ablation with an initial drift velocity flies to entrance of a Radio Frequency Quadrupole (RFQ) LINAC; ions will be separated from plasma via high voltage at the inside of the RFQ LINAC. Then ions are captured by the RF buckets and are accelerated remaining high current over 10mA. In the past, we had accelerated carbon4+, carbon5+, and carbon6+ using a RFQ with partially modulated vanes. Due to the un-modulated section of the electrodes, accelerated beams were not bunched. In 2011, we replaced the vanes with a newly designed one. The designed charge to mass ratio (q/A) is 1/6 and the output energy is 270 keV/u. The beam commissioning with carbon 4+ was successfully carried out. In the next step we'll try to accelerate carbon 2+ (q/A=1/6), which is to demonstrate the feasibility of the Ag+15 ion acceleration. INTRODUCTION We are studying high current highly charged beam acceleration using direct plasma injection scheme (DPIS) which has been developed for several years [1]. We established how to capture and accelerate intense carbon beams with carbon beam. Using a table top small NdYAG laser system, carbon can be easily ionized up to fully stripped condition and the vanes in the RFQ was designed to accelerate more than 4/12 of charge to mass ration. We had tested carbon 4+, 5+ and 6+ acceleration. In the next step, we plan to accelerate heavier species like silver, bismuth or uranium, newly designed vanes were demanded. Currently we are testing laser irradiation conditions. In parallel, we modified the RFQ to accelerate lower charge to mass ratio particles. In this paper we describe the beam-commissioning test with a new set of vanes. LASER ION SOURCE High power laser irradiation on the solid target makes laser ablation plasma. A laser power density of more than 10^10[W/cm^2] is required to induce high charge state ions, therefore laser light is needed to be focused by an optical lens. The plasma contains a stream of high brightness highly charged ion flux. By extracting ions from the plasma, intense ion beams can be easily provided. Since the ablated plasma is emitted from a target material, the plasma moves away from the target. Simultaneously, the plasma expands three dimensionally. So the plasma plume volume expands longitudinally and transversely in a free space. The longer length of the plasma in the space gives a longer ion beam pulse width and thinner ion current density. These relations are shown in equations (1) and (2). The is a pulse length, and the is a current density of generated ion beam. The L is a plasma drift distance, the length from target to the ion extraction position.   L