Yong-Hwan Kim

Design of the PEFP MEBT

A MEBT system of the Proton Engineering Frontier Project (PEFP) has to be installed after the 20 MeV DTL where a beam extraction system will be positioned to supply 20 MeV proton beams to the user group. This implies a large drift space which can be a serious potential problem in the longitudinal beam matching between the DTL and the following accelerating structure. The MEBT consists of 8 quadrupole magnets and 2 buncher cavities. The initial 4 quadrupoles is controlling the beam size in the bending magnet for beam extraction. The transverse beam matching is achieved by the following 4 magnets. The buncher cavities are for the longitudinal beam matching.

Conceptual design of 10 MeV, 100 kW CW electron accelerator for industrial application

The application fields of intense gamma-rays or X-rays for industrial purposes are expanding. An electron beam accelerator which can generate X-rays whose dose rate is equivalent to the effect of a several MCi gamma-ray source is a major candidate as an intense X-ray source. The 10 MeV, 100 kW CW electron accelerator Fantron-I is conceptually designed for an X-ray source to irradiate food, corn, forest products and so on. Electrons are accelerated seventeen times through two coaxial cavities with a TM010 mode by means of a bending magnet located outside the cavity. The resonant frequency of the cavity is about 160 MHz and the phase of one cavity is 180/spl deg/ shifted from that of the other. Higher order modes (HOM) which may cause beam instability are analyzed. The design parameters of beam lines and bending magnets are determined from the results of beam phase analysis, especially magnetic flux density and locations of each bending magnet are carefully adjusted to synchronize the beam with the accelerating field. In this paper, characteristics and the overall conceptual design of the Fantron-I are presented.

Initial Test of the PEFP 20 MeV DTL

A conventional 20 MeV drift tube linac (DTL) for the Proton Engineering Frontier Project (PEFP) has been developed as a low energy section of 100 MeV accelerator. The machine consists of four tanks with 152 cells supplied with 900 kW RF power from 350 MHz klystron through the ridge-loaded waveguide coupler. We assembled the fabricated accelerator components and aligned each part with care. We have also prepared the subsystems for the test of the DTL such as RF power delivery system, high voltage DC power supply, vacuum system, cooling system, measurements and control system and so on. The detailed description of the initial test setup and preliminary test results will be given in this paper.

Test Results of the PEFP 3MeV RFQ Upgrade

A 3MeV RFQ for 100MeV proton accelerator has been developed at PEFP (Proton Engineering Frontier Project). The tuning results of the cavity showed that both the frequency and field profile were beyond the tuner limit. To check the cavity characteristics, RF test including proton beam acceleration has been done. To solve the problems in existing RFQ, new RFQ so called RFQ Upgrade has been fabricated. Because the main problem of the existing one is improper tuning of the cavity, the important step for development of RFQ Upgrade is to adjust the vanes before brazing. In this paper, the test results of the existing PEFP RFQ and the pre-brazing tuning are presented.

Design of radially focused uniform X-ray source

The 10 MeV, 100 kW CW electron accelerator (FANTRON I) is being developed in Department of Nuclear Engineering, Seoul National University (SNU). The X-ray generated by the accelerated electron beam will be used in sterilizing the agricultural, forest and aquatic products. For the effective irradiation and the safety of the irradiated products, uniform irradiation is needed. The designed target is mainly featured by the radially focused uniform X-ray. The diameter of irradiation hole is 0.75 m. And the generated X-ray is emitted toward the center of the irradiation hole with uniform distribution along the circumference. To generate the radially focused uniform X-ray, the accelerated electron beam must be focused radially on the target that is the outer shell of the irradiation hole with high uniformity.

Fabrication of the KSTAR central solenoid model coil (II)

The Korea Superconducting Tokamak Advanced Research (KSTAR) Central Solenoid (CS) model coil has been developed. The conductor type is Nb/sub 3/Sn CICC (cable-in-conduit conductor). The entire manufacturing equipment and tooling have been established along with an online manufacturing system. The major role of the KSTAR CS model coil is to demonstrate the manufacturing feasibility of the KSTAR superconducting coils. The winding type is continuous pancake winding without joints in one coil. This paper gives a full account of the detailed manufacturing processes such as winding, jacket removing, welding, termination, heat treatment, insulation and resin impregnation, etc.

Test Scheme Setup for the PEFP 20 MeV DTL

A 100 MeV proton accelerator is under development for the Proton Engineering Frontier Project (PEFP). The goal of the first stage of the project is to develop a 20MeV accelerator and the initial test of the 20 MeV accelerator will be made. The DTL of 20 MeV accelerator consists of four tanks and will be driven with single klystron, which gives rise to some unique problems with regard to the way of independent resonance control for each tank. Some changes made in the LLRF for reducing phase or amplitude error of cavities affect all of four tanks simultaneously, for which it is not possible to use LLRF for individual control of phase and amplitude of each tank. For independent control of each tank, we are going to use the temperature control of the drift tubes as a frequency tuner. During the initial test of the DTL, the phase of each tank will be synchronized with the first tank phase, and beam based test will be performed as if all of tanks were single unit. The detailed description of the test scheme and the analysis results will be given in this paper.

Performance test of the KSTAR Central Solenoid (CS) model coil

The KSTAR (Korea Superconducting Tokamak Advanced Research) CS (Central Solenoid) model coil has been developed and the performance test for the selection of materials and demonstration of manufacturing procedures at each steps have been carried out. Before the stability performance test in the vacuum cryostat, the preliminary cryogenic test, with full data acquisition, quenching detection and power supply system in the pool-type cryostat, have been done. In this cryogenic preliminary test, the major parameters related to structural integrity, quenching properties, cool-down and warm-up condition, and loss problems, etc. were measured under the various operational scenarios, and compared with the analysis. The main results of the test during the manufacturing and the preliminary cryogenic test are described in this paper.

Mechanical analysis of the KSTAR CS model coil

KSTAR (Korea Superconducting Tokamak Advanced Research) CS (central solenoid) model coil made with CIC (cable in conduit) superconductor had been developed in the Department of Nuclear Engineering, Seoul National University. In superconducting magnets, there are mechanical stresses by Lorentz force and thermal stresses by the difference of thermal contraction between conduit and insulator. In this study, the computational analysis with ANSYS, a common FEA (finite element analysis) code, and experimental measurements of KSTAR CS model coil with resistance foil type strain gages have been performed. According to the results of computational analysis, KSTAR CS model coil satisfies safety design limitations. Experimental results obtained from the test of KSTAR CS model coil were compared with those of computational analysis.

Insulation system test for the KSTAR central solenoid (CS) model coil

The insulation system for a tokamak superconducting magnet should ensure the mechanical and electrical reliability and must have resistance to the radiation environment during operation. The winding scheme of the whole KSTAR (Korea Superconducting Tokamak Advanced Research) CS (central solenoid) coil using Nb/sub 3/Sn CICC (cable in conduit conductor), it is found that there is considerable shear due to tensile force. To obtain a proper resin system two candidates were tested and compared with the ITER (International Thermonuclear Experimental Reactor) standard resin system as a benchmark. This work includes viscosity measurement, flexural strength, shear strength and thermal contraction at room temperature and 77 K. Test procedures and the results of each measurement are presented.