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Cha S.,Korea Atomic Energy Research Institute | Kim Y.,Korea Atomic Energy Research Institute | Lee B.C.,Korea Atomic Energy Research Institute | Park H.D.,Radiation Technology eXcellence RTX | And 3 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2017

KAERI is developing a 6 MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300 MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25 MHz, it gives 5 MHz (∵±25 MHz/10 turns → 50 MHz/10 turns =5 MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10 kHz/step (=5 MHz per turn/500 steps per turn). The developed system is a more compact new resonance frequency control system. In addition, a frequency measuring part is included and it can measure the real-time resonance frequency from the magnetron. We have succeeded in the stable provisioning of RF power by recording the results of a 0.01% frequency deviation in the AFC during an RF test. Accordingly, in this paper, the detailed design, fabrication, and a high power test of the AFC system for the X-band linac are presented. © 2017 Elsevier B.V.

Kim J.H.,Korea Atomic Energy Research Institute | Park H.D.,Radiation Technology EXcellence RTX | Kim H.-J.,Kyungpook National University | Tae H.-S.,Kyungpook National University
Molecular Crystals and Liquid Crystals | Year: 2015

For the fast and stable address under the high Xe gas condition of plasma display panels (PDPs), the weak and strong discharge characteristics in both surface-gap and plate-gap discharges were examined for two different Xe gas contents (7 and 20%). It is observed that it is very difficult to produce the strong plate-gap discharge required for the address discharge as the Xe gas content increases from 7 to 20%, thus requiring an additional voltage increase for the strong plate-gap discharge. Based on these experimental observations, the modified driving waveform, featuring being able to produce an intensified address discharge in the plate-gap discharge without a misfiring discharge in the surface-gap discharge, is proposed for the successful high speed address of the high Xe PDP. © 2015 Copyright © Taylor & Francis Group, LLC.

Kang H.S.,Radiation Technology eXcellence RTX | Koo Y.H.,Radiation Technology eXcellence RTX | Park H.D.,Korea Atomic Energy Research Institute | Chai G.-S.,Radiation Technology eXcellence RTX | And 3 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2015

As the development of manufacturing technology for electronic devices, propresses it is necessary to study manufacturing technologies for mass storage, low-volume, improved reliability, and low cost materials for electronic devices used in data communication. The noble metals are the most commonly used raw materials used in such manufacturing. However, the raw materials (Ag, Pt, etc.) are expensive and raise the manufacturing cost. So, there is a need to replace these materials with raw materials of low cost. Recently, the much-cheaper Cu has received attention in that it has the same properties as the noble metals. Cu has good physical and chemical properties. However, its anti-oxidation is weak. Therefore, to make up for this weak point, research has generally been conducted to find a method to coat copper with a noble metal. The coating, comprised of the noble metal, is strong against the oxidation of the Cu surface. In this study, we made Cu@Ag core.shell nanoparticles; these particles have the same level of electro-conductivity as Ag. These materials are expected to reduce the product cost of raw materials. Copyright © 2015 American Scientific Publishers All rights reserved Printed in the United States of America.

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