Kyung-Tae Seol

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 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.

Diffusion and Thermal Stability of Implanted Hydrogen in ZnO Nanorods

The 20-MeV proton-beam with a fluence of 10 cm was irradiated on ZnO nanorods. The effects of protonbeam irradiation on ZnO nanorods are investigated by using H nuclear magnetic resonance (NMR) spectroscopy. After irradiation, new and modified NMR resonance lines are observed in H NMR spectra. The diffusion and thermal stability of each proton species are investigated from the laboratoryand rotating-frame spin-lattice relaxation data depending on temperature. Understanding the properties of thermally stable hydrogen species created by the beam irradiation may promise many possible applications, since the hydrogen stable up to high temperature only meets the device working conditions.

Solid Targetry for the Isotope Production Facility at the KOMAC 100 MeV Linac

The construction of the isotope production facility was recently completed on the 100 MeV proton linac at the KOMAC (Korea Multi-purpose Accelerator Complex). To produce the Sr-82 and Cu-67, we have prepared the solid targetry which consist of target transportation system , target cooling system and a hot-cell for remote handling. The Isotope production targets are made of RbCl pellet, Zn metal disc and stainless steel cladding. For the proton beam irradiation, the targets are transported by target drive system which consist of drive chain and guide rail by remotely. In this paper, we will report the detailed design, fabrication and operation status of the solid targetry at the KOMAC isotope production facility. TARGET PREPARATION To design RI target, we have derived the optimum thickness of target materials considering the beam energy loss by the beam window, cooling water and target claddings through SRIM calculation [2]. Figure 1 describes the typical target configuration for Sr-82 production, which is consisted of 1 RbCl target and aluminum dummy target. Figure 1: Target configuration for Sr-82 production. For the Sr-82 and Cu-67, the pressed RbCl pellet and Zn metal disc was prepared. These target materials have the natural abundance of isotopes and they are encapsulated in stainless steel cladding with o.d. of 60 mm and i.d. of 50 mm with 0.3 mm window for the proton irradiation. To prevent the leakage of the radioactive species inside target claddings, the cladding is fabricated by laser welding. After the target cladding fabrication, the leakage tests have been conducted by using the penetration test. Figure 2 shows the fabricated proto-type target claddings after welding process. (a) RbCl pellet and its target cladding (b) Zn disc and its target cladding Figure 2: The proto-type target for Sr-82 / Cu-67 production.

SRF LINAC FOR FUTURE EXTENSION OF THE PEFP

A study on the superconducting RF linac is underway in order to increase the beam energy up to 1 GeV by extending the Proton Engineering Frontier Project (PEFP) 100-MeV linac. The operating frequency of the PEFP superconducting linac (SCL) is 700 MHz, which is determined by the fact that the frequency of the existing normal conducting linac is 350 MHz. A preliminary study on the beam dynamics showed that two types of cavities with geometrical betas of 0.50 and 0.74 could cover the entire energy range from 100 MeV to 1 GeV. An inductive output tube (IOT) based RF system is under consideration as a high-power RF source for the SCL due to its low operating voltage and high efficiency. As a prototyping activity for a reduced beta cavity, a five-cell cavity with a geometrical beta of 0.42 was designed and fabricated. A vertical test of the prototype cavity at low temperatures was performed to check the performance of the cavity. The design study and the prototyping activity for the PEFP SCL will be presented in this paper.

DESIGN AND FABRICATION OF THE BEAM POSITION MONITOR FOR THE PEFP LINAC

The beam position monitor (BPM) is an essential component for the PEFP 100-MeV linacs commissioning. A prototype stripline-type linac BPM was designed for this purpose. The electrode aperture is 20 mm in diameter, and the electrode is 25 mm long, so it can be installed between Drift Tube Linac (DTL)101 and DTL102, which is the shortest distance. One end of the electrode is connected to the Sub Miniature Type A (SMA) feed through for signal measurement, and the other end is terminated as a short. The signal amplitude of the fundamental component was calculated and compared with that of the second harmonic component. The designed BPM was fabricated and a low-power RF test was conducted. In this paper, the design, fabrication and low power test of the BPM for the PEFP linac are presented.

Compact microwave ion source for industrial applications.

A 2.45 GHz microwave ion source for ion implanters has many good properties for industrial application, such as easy maintenance and long lifetime, and it should be compact for budget and space. But, it has a dc current supply for the solenoid and a rf generator for plasma generation. Usually, they are located on high voltage platform because they are electrically connected with beam extraction power supply. Using permanent magnet solenoid and multi-layer dc break, high voltage deck and high voltage isolation transformer can be eliminated, and the dose rate on targets can be controlled by pulse duty control with semiconductor high voltage switch. Because the beam optics does not change, beam transfer components, such as focusing elements and beam shutter, can be eliminated. It has shown the good performances in budget and space for industrial applications of ion beams.

Amplitude and Phase Stability of Analog Components for the LLRF System of the PEFP Accelerator

The Proton Engineering Frontier Project (PEFP) low-level radio frequency (LLRF) system for the 3-MeV radio frequency quadrupole accelerator (RFQ) and the 20-MeV drift tube linear accelerator (DTL) has been developed. A stability of 1 % in the amplitude and 1 degree in the phase is required. Therefore, the drift of the analog components should be low enough to satisfy these requirements. An analog chassis, as a prototype of the LLRF system, was con gured and tested. RF components, including an IQ modulator, an RF switch, a mixer, RF splitters, RF lters, a circuit for measuring tank phase and a trip circuit for high voltage standing wave ratio (VSWR), have been installed in this chassis. The analog chassis performs an error compensation of the RF amplitude and phase from the IQ signal, a down-conversion to the 10 MHz IF signal, an interlock for the arc and the high VSWR and a distribution for the RF and the clock signals. The amplitude and the phase stability of each component were measured to check the e ect on the whole systems performance. In the test with dummy cavities, a uctuation of 5 degrees was measured in the 340 MHz LO signal, but the relative phase between the two cavities was maintained within 0.2 degrees because of the e ect being the same for the LO signals of the two cavities.