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Design and fabrication of side-coupled RF cavity for S-band 6/3 MeV dual-energy electron linac
Mun Jungho,Chae Moonsik,Lee Jaehyun,Yeon Yeong Henm,Park Jae Yeon,Lee Nam-Ho 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.7
We demonstrate the design and manufacture of RF (radio-frequency) electron linac (linear accelerator) cavity of 6/3 MeV dual-energy X-ray generator for air-cargo security inspections. When an accelerated electron beam collides with the metal target, an X-ray is generated by a bremsstrahlung process. We designed a dual-energy RF cavity using a three-dimensional electromagnetic field simulation code and an electron beam trajectory code. The designed RF cavity is a side-coupled standing-wave type, driven by the π/2 mode, and has a resonant frequency of 2856 MHz. The maximum dose rate of X-ray was calculated to be 7.07 and 0.91 Gy/min at 1 m for an X-ray energy of 6 and 3 MeV using a tungsten target, respectively. In the simulation results, the accelerating gradient was about 13.5 MV/m, the Q-factor was 15,900, and the total length of the RF cavity was 57 cm for 6 MeV of the maximum accelerated electron energy. The resonance frequency and the Q-factor of the fabricated RF cavity were measured by 2855.34 MHz and 14,000, respectively.
Beam Characterization at the KAERI UED Beamline
Sadiq Setiniyaz,Hyun Woo Kim,In-Hyung Baek,Jinhee Nam,MoonSik Chae,Byung-Heon Han,Boris Gudkov,Kyu Ha Jang,Sunjeong Park,Sergey Miginsky,Nikolay Vinokurov,Young Uk Jeong 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.6
The UED (ultrafast electron diffraction) beamline of the KAERI’s (the Korea Atomic Energy Research Institute’s) WCI (World Class Institute) Center has been successfully commissioned. We have measured the beam emittance by using the quadrupole scan technique and the charge by using a novel measurement system we have developed. In the quadrupole scan, a larger drift distance between the quadrupole and the screen is preferred because it gives a better thin-lens approximation. A high bunch-charge beam, however, will undergo emittance growth in the long drift caused by the space-charge force. We present a method that mitigates this growth by introducing a quadrupole scan with a short drift and without using the thin-lens approximation. The quadrupole in this method is treated as a thick lens, and the emittance is extracted by using the thick-lens equations. Apart from being precise, our method can be readily applied without making any change to the beamline and has no need for a big drift space. For charge measurement, we have developed a system consisting of an in-air Faraday cup (FC) and a preamplifier. Tests performed utilizing 3.3- MeV electrons show that the system was able to measure bunches with pulse durations of tens of femtoseconds at 10 fC sensitivity.
Kang Chang Goo,Kim Su Jin,김병혁,Kim Young Soo,Park Jeong Min,Kim Han Soo,Ha Jang Ho,Choi Hyojeong,Chae Moonsik,Oh Kyungmin,Lee Byeongno,Lee Nam-Ho 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.9
Radiation-based imaging systems comprise multiple radiation sensors that are assembled with coupled Si PIN (positive - intrinsic - negative) photodetectors and scintillators. This paper describes the fabrication and characterization of a four-channel array Si PIN photodetector for security inspection systems. The Si PIN photodetector was fabricated using conventional (CMOS) processes at the Radiation Equipment Fab. The junction depth, passivation, and anti-reflection layer of the photodetector were controlled to maximize the light detection efficiency and the signal-to-noise ratio. The spectral responsivity obtained was 0.28 A/W for the cadmium tungstate (CWO) emission at a wavelength of 475 nm. Finally, a line pattern image was acquired using the fabricated Si PIN sensor and a self-developed readout and data acquisition system. The significance of this study is it confirms the feasibility of using the developed array-type Si PIN photodetectors in radiation-based imaging systems.