Eun-San Kim

Beam Dynamics for High-Power Superconducting Heavy-Ion Linear Accelerator of RAON

We investigated optimum choices of accelerator parameters for superconducting-technology-based heavy-ion linear accelerator (linac) to achieve the high beam quality at an in-flight target with a high beam power of 400 kW. The superconducting linac system is designed to provide a stable-ion beams from protons to uranium with energies of 600 MeV and 200 MeV/u, respectively. The linac optics is also designed such that the effects of envelope instability, parametric resonance between the transverse and longitudinal planes, beam steering effect due to asymmetric field in quarter-wave resonance (QWR) cavities, and emittance growth in charge strippers due to the straggling effect, parametric resonance, and envelope instability become as small as possible. The dimensions of the warm and cold sections in the low-energy section which mainly determine the longitudinal acceptance of the linac are optimized to achieve a longitudinal acceptance larger than 27 keV/u-ns enabling stable operation. The tracking simulation for the uranium beam was performed and we achieved the transverse normalized rms emittance of 0.095 mm-mrad and longitudinal rms emittance of 2.10 keV/u-ns at the end of designed linac without uncontrolled beam losses along the linac. In order to estimate the degradation of the machine performance due to imperfections such as misalignment, ripple of the magnet power source, and phase and power variation of the RF source, the particle tracking simulation was performed and the uncontrolled beam loss with the machine imperfection without the orbit and optics correction was less than 1 W/m which is a condition required for machine operation. The optimum scheme for orbit correction in the low-energy linac is investigated based on the transfer matrix of the elements and the validation of the scheme is confirmed by the particle tracking simulation using TRACK code.

Preliminary physical and electromagnetic design for the injector of the heavy ion superconducting linaca)

The Rare Isotope Science Project in Korea has developed a high current heavy ion accelerator using superconducting linacs. A normal conducting injector system was proposed to supply heavy ions to the superconducting driver linac. A beam physics and engineering design study was performed, and the beam dynamics of the injector was simulated. Optimized beam transmission and emittance were obtained from the beam dynamics simulation. Various normal conducting bunchers, such as multi-harmonic buncher, velocity equalizer, radiofrequency quadrupole, and re-bunchers, will be used and have been electromagnetically calculated.

Design study of a radio-frequency quadrupole for high-intensity beams*

The Rare isotope Accelerator Of Newness (RAON) heavy-ion accelerator has been designed for the Rare Isotope Science Project (RISP) in Korea. The RAON will produce heavy-ion beams from 660-MeV-proton to 200-MeV/u-uranium with continuous wave (CW) power of 400 kW to support research in various scientific fields. Its system consists of an ECR ion source, LEBTs with 10 keV/u, CW RFQ accelerator with 81.25 MHz and 500 keV/u, a MEBT system, and a SC linac. In detail, the driver linac system consists of a Quarter Wave Resonator (QWR) section with 81.25 MHz and a Half Wave Resonator (HWR) section with 162.5 MHz, Linac-1, and a Spoke Cavity section with 325 MHz, Linac-2. These linacs have been designed to optimize the beam parameters to meet the required design goals. At the same time, a light-heavy ion accelerator with high-intensity beam, such as proton, deuteron, and helium beams, is required for experiments. In this paper, we present the design study of the high intensity RFQ for a deuteron beam with energies from 30 keV/u to 1.5 MeV/u and currents in the mA range. This system is composed of an Penning Ionization Gauge ion source, short LEBT with a RF deflector, and shared SC Linac. In order to increase acceleration efficiency in a short length with low cost, the 2nd harmonic of 162.5 MHz is applied as the operation frequency in the D+ RFQ design. The D+ RFQ is designed with 4.97 m, 1.52 bravery factor. Since it operates with 2nd harmonic frequency, the beam should be 50% of the duty factor while the cavity should be operated in CW mode, to protect the downstream linac system. We focus on avoiding emittance growth by the space-charge effect and optimizing the RFQ to achieve a high transmission and low emittance growth. Both the RFQ beam dynamics study and RFQ cavity design study for two and three dimensions will be discussed.

Development of an ion beam analyzing system for the KBSI heavy-ion accelerator.

The Korea Basic Science Institute (KBSI) has been developing a heavy ion accelerator system to accelerate high current, multi-charge state ions produced by a 28 GHz superconducting electron cyclotron ion source. A beam analyzing system as a part of the low energy beam transport apparatus was developed to select charged particles with desirable charge states from the ion beams. The desired species of ion, which is generated and extracted from the ECR ion source including various ion particles, can be selected by 90° dipole electromagnet. Due to the non-symmetrical structure in the coil as well as the non-linear permeability of the yoke material coil, a three dimensional analysis was carried out to confirm the design parameters. In this paper, we present the experimental results obtained as result of an analysis of KBSI accelerator. The effectiveness of beam selection was confirmed during the test of the analyzing system by injecting an ion beam from an ECR ion source.

Simultaneous Two Beam Acceleration Lattice Design Study for the Post Linear Accelerator of RISP

The Rare Isotope Science Project, RISP, is the research complex by using heavy ion accelerator, in which RISP research complex consists of front-end system, super conducting linear accelerator(SCL), ISOL system, In-flight system. The original purpose of post linear accelerator was for the alternative acceleration of stable driver beam from ECR ion source and unstable rare isotope beam from ISOL system. However, the post accelerator lattice was re-designed with new concept of acceleration method to get more benefits. The idea was the simultaneous acceleration of stable driver beam and RI beam by using the post accelerator lattice of average A/q value. In this proceeding, we will describe the results of beam dynamics study of simultaneous two beam acceleration at SCL3.

Signal Archiving System for RISP Heavy-ion Accelerator Control System

The Rare Isotope Science Project (RISP) of Institute for Basic Science (IBS) has developed heavy-ion accelerator. RISP control system uses the EPICS control system to control and monitor all accelerator software and hardware. Archiver appliance is the tool for signal archive and retrieval. RISP control group has conducted test of the archiver appliance, and customized signal archiver system. This paper will present the archiver appliance test that we have used.