• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1530-1533
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• 2005

Total 12 units of high power klystron-modulator systems as microwave source is under operation for 2.5-GeV electron linear accelerator in Pohang Light Source(PLS) linac. RF power and beam power of klystron are precisely measured for the effective control of electron beam. A precise measurement and measurement equipment with good response characteristics are required for this. Input power of klystron is calculated from the applied voltage and the current on its cathode. Tiny measurement error severely effects RF output power value of klystron. Therefore, special care is needed to measure precise beam voltage. Capacitive voltage divider(CVD) unit is intended for the measurement of beam voltage of 400 kV generated from the pulsed klystron-modulator system. Main parameter to determine the standard capacitance in the high arm of CVD is dielectric constant of insulation oil. Therefore CVD should be designed to have a minimum capacitance variation due to voltage, frequency and temperature in the measurement range. This paper will discuss the analysis of capacitive voltage divider for a pulsed high-voltage measurement, and the empirical relations between capacitance and oil temperature variation.

• Nuclear Engineering and Technology
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• 제37권5호
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• pp.447-456
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• 2005

Laser driven accelerators promise to provide an alternative to conventional accelerator technology. They rely on the excitation of large amplitude density waves in a plasma by the photon pressure of an intense laser. The density oscillations in which electrons and ions are separated, result in extremely large longitudinal electric fields that can be several orders of magnitude larger than those that are used in today's radio-frequency accelerators. Whereas this principle had been demonstrated experimentally for nearly two decades, it was not until 2004 that the production of high quality electron beams around 100 MeV was demonstrated. Analysis, aided by particle-in-cell simulations, as well as experiments with various plasma lengths and densities, indicate that tailoring the length of the accelerator, together with loading of the accelerating structure with beam, are the keys to production of mono-energetic electron beams. Increasing the energy towards a GeV and beyond will require reducing the plasma density and design criteria are discussed for an optimized accelerator module. The current progress and future directions are summarized through comparison with conventional accelerators, highlighting the unique short and long term prospects for intense radiation sources and high energy accelerators based on laser-drivenplasma accelerators.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.180-182
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• 1994

In an electron storage ring of Pohang Light Source (PLS), electrons lose their energy in every turn by the synchronous radiation. A high power RF amplifier is employed to compensate the electron energy that is lost by the synchronous radiation. The specification of RF amplifier is an continuous output power of 60 kW at 500.082 MHz operating frequency. The power is supplied to RF cavities in the storage ring tunnel. Total number of amplifier system currently required is three. Tile total number will be increased upto five as the operating condition of storage ring is upgraded. The RF amplifier is mainly consisted of a high voltage DC power supply, an intermediate RF power amplifier (IPA), and a klystron tube. In this article, the design of RF amplifier system and characteristics of the klystron tube will be discussed.

• 한국의학물리학회지:의학물리
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• 제31권2호
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• pp.9-19
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• 2020

Purpose: This study aims to develop a multi-purpose electron beam irradiation device for preclinical research and material testing using the research electron linear accelerator installed at the Dongnam Institute of Radiological and Medical Sciences. Methods: The fabricated irradiation device comprises a dual scattering foil and collimator. The correct scattering foil thickness, in terms of the energy loss and beam profile uniformity, was determined using Monte Carlo calculations. The ion-chamber and radiochromic films were used to determine the reference dose-rate (Gy/s) and beam profiles as functions of the source to surface distance (SSD) and pulse frequency. Results: The dose-rates for the electron beams were evaluated for the range from 59.16 Gy/s to 5.22 cGy/s at SSDs of 40-120 cm, by controlling the pulse frequency. Furthermore, uniform dose distributions in the electron fields were achieved up to approximately 10 cm in diameter. An empirical formula for the systematic dose-rate calculation for the irradiation system was established using the measured data. Conclusions: A wide dose-rate range electron beam irradiation device was successfully developed in this study. The pre-clinical studies relating to FLASH radiotherapy to the conventional level were made available. Additionally, material studies were made available using a quantified irradiation system. Future studies are required to improve the energy, dose-rate, and field uniformity of the irradiation system.

• 한국진공학회지
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• 제15권4호
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• pp.331-337
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• 2006

국제 직선형 충돌 가속기 (ILC; International Linear Collider). 자유전자 레이저 (FEL: Free Electron Laser)와 같은 차세대 가속기에 사용 할 공동형 빔위치 측정기 ( 공동형 BPM: cavity-type beam position monitor)를 일본 고에너지 연구소 (KEK; High Energy Accelerator Research Organization)와 공동으로 개발하였다. ILC 및 FEL의 운전을 위해서는 빔 기반 정렬 (beam-based alignment)과 되먹임 장치 (feedback system)가 필수적으로 요구되는데, 이를 위해서는 적절한 위치에 서브마이크론의 분해능을 지닌 빔위치 측정기를 설치하여야 한다 [1]. 공동형 BPM은 기계적인 정밀도에 매우 민감하므로 정밀한 제작과 미세한 기계적 조정을 통하여 성능을 달성하게 된다. 우리는 제작 오차를 줄이기 위하여 공진 공동, 빔 튜브, 도파관, 전기도입기 등 모든 부품을 조립 후 한꺼번에 진공 브레이징 하였다. 공동의 외주면에는 네 개의 튜닝 핀을 두어 공진주파수 및 x-y 격리도 (x-y isolation between coupled waveguide)를 미세 조정할 수 있도록 하였다. 현재 개발된 공동형 BPM 은 공진주파수는 6.422 GHz 이며, 공동 내경은 53.822 mm, 빔의 위치 측정 범위는 ${\pm}250 {\mu}m$이다. network analyzer를 관측하면서 튜닝핀을 이용하여 x-y 격리도를 -40 dB 이하로 조정할 수 있었다. 실제 KEK ATF2에서의 전자빔을 이용한 시험에서 신호의 모양, x-y 격리도, 민감도 등에서 만족한 결과를 얻었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권2호
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• pp.63-68
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• 2005

Total 12 units of high power klystron-modulator systems as microwave source are under operation for 2.5 GeV electron linear accelerator in Pohang Light Source (PLS) linac. The klystron-modulator system has an important role for the stable operation to improve an availability statistics of overall system performance of klystron-modulator system. RF power and beam power of klystron are precisely measured for the effective control of electron beam. A precise measurement and measurement equipment with good response characteristics are demanded for this. Input power of klystron is calculated from the applied voltage and the current on its cathode. Tiny measurement error severely effects RF output power value of klystron. Therefore, special care is needed to measure precise beam voltage. Capacitive voltage divider (CVD), which divides input voltage as capacitance ratio, is intended for the measurement of a beam voltage of 400 kV generated from the klystron-modulator system. Main parameter to determine standard capacitance in the high arm of CVD is dielectric constant of insulation oil. Therefore CVD should be designed to have a minimum capacitance variation due to voltage, frequency and temperature in the measurement range. This paper will be present and discuss the design concept and analysis of capacitive voltage divider for a pulsed high-voltage measurement, and the empirical relations between capacitance effects and oil temperature variation.

• 한국전자파학회논문지
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• 제29권6호
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• pp.407-410
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• 2018

일반적으로 전자파의 동작 주파수가 높아짐에 따라 최대 출력이 작아지고, 파동의 파장도 작아지기 때문에, 회로의 크기도 작아질 수밖에 없다. 특히, kW급 이상의 고출력 테라헤르츠파 주파수 대역의 회로를 제작하려면, ${\mu}m{\sim}mm$ 규모의 회로 크기 문제 때문에 제작에 한계점이 있다. 이러한 한계점을 극복하기 위해 본 논문에서는 회로의 지름이 2.4 cm 정도의 원통형으로, 0.1 THz~0.3 GW급의 발생원 설계 기술을 제안한다. 판드로모티브 힘이 생기는 플라즈마 항적장 가속원리와 인위적인 유전체 활용한 체렌코프방사 발생 기술 기반의 고출력 전자파 발생원의 최적화된 설계를 위해 모델링 및 전산모사를 수행하였다. 객관적인 검증 과정을 통해 회로의 크기에 제한을 덜 받도록 하는 대구경 형태의 고출력 테라헤르츠파 진공소자 제작이 용이하도록 효과적인 설계의 가이드라인을 제시하였다.