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Experimental Measurement of the 3D Spatio-Temporal Profile of a Pulsed Terahertz Wave
Yun-Sik Jin,Seok-Gy Jeon,Chae-Hwa Shon,김근주,Sun-Shin Jung 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.4
We experimentally analyzed the spatio-temporal profile of the pulsed THz wave generated from the surface of a p-type InAs (100) bulk crystal irradiated with a femtosecond laser. Propagation of the pulse during several picoseconds was observed with enhanced spatial resolution in far-field region on an arbitrary chosen two-dimensional area. The spatial configuration in the frequency domain shows that there are two different dominant radiation patterns that depend on the radiation frequency because the intensity profile of the pulsed THz wave has a non-Gaussian distribution. The analysis can help us figure out the physical origins for pulsed THz wave generation from semiconductor surfaces.?
A New Slit-Type Vacuum-Channel Transistor
In Jun Park,Seok-Gy Jeon,Changhwan Shin Institute of Electrical and Electronics Engineers 2014 IEEE transactions on electron devices Vol. No.
<P>A new vacuum-channel transistor with a carbon nanotube cathode and nanometer-scale channel length-called a slit-type vacuum-channel transistor is proposed and investigated. The suggested device structure features distinguishable cutoff, linear, and saturation regions with a negligible gate leakage current. Its channel length is almost the same as the mean free path of carriers in air, which suggests that the device can operate not only in vacuum but also in air, without any performance degradation. Because of its geometrical characteristics, it is possible for this device to be operated when the anode bias is almost the same as the gate bias with negligible oxide leakage. Therefore, the device can be used as an elemental device component in digital integrated circuits.</P>
Characteristics of the Shock Structure for Transition Injection in Laser Wakefield Acceleration
김경남,Yong Hun Hwangbo,Seok-Gy Jeon,Jaehoon Kim 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.5
In order to develop a stable and ecient laser wakefield accelerator by transition injection, the characteristics of the plasma density generated in a gas medium by shock was experimentally measured. The density difference between before and after the shock, and the density after the shock are important parameters for determining the charge and energy of the electron beam in the transition injection scheme. Based on experiments, we developed an adjustment method of these parameters and measured the characteristics of the electron beam by using the shock structure. The shock structure in the gas medium was generated by inserting a blade in a supersonic gas nozzle, and plasma was generated by using a 16-TW laser. Before the shock, the density increases and after that, the density is the same as the density without the shock. The ratio of the density difference was in the range of 0:1 - 0.6, which could be adjusted according to the position of the blade. The density after the shock was adjustable by varying the distance between the laser and the nozzle, and it was in a suitable range of 5 1018 cm3 - 1:2 1019 cm3 for the electron acceleration. The measured electron beam indicates that the position of the shock needs to be in the range of 0:3 - 0.5 mm before the laser focal position in the vacuum because of faster laser focus due to self-focusing.
Kim Kyung Nam,Hwangbo Yonghun,Jeon Seok-gy,Kim Jaehoon,Han Soorim,Kim Kum Bae 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.5
A cancer treatment device using a very high energy electron beam has been studied as a new radiation therapy method because of its deep penetration depth, dose characteristics that are better than those of the existing X-ray method, and easy adjustment of the irradiation direction compared to existing equipment. For this treatment, compact high-energy electron accelerators are essential, and a laser wakefield accelerator is a good candidate. In this study, very high energy electrons were accelerated using a laser wakefield accelerator, and the dose characteristics due to these electrons were measured to confirm the possibility of treatment. Electron beam with an energy of 94 MeV were accelerated by using a 16-TW high-power laser, and the dose profile was measured with a tough phantom by using a Gafchromic film. With an 18 nC charge, the peak dose was 120 cGy at a 40 mm depth. The measured dose profile was compared with that obtained using a Monte Carlo simulation with low and high energy electron beams, and the results indicate a quasi-mono-energetic property of the electron beam.
High performance field emission of carbon nanotube film emitters with a triangular shape
Shin, Dong Hoon,Yun, Ki Nam,Jeon, Seok-Gy,Kim, Jung-Il,Saito, Yahachi,Milne, William I.,Lee, Cheol Jin Elsevier 2015 Carbon Vol.89 No.-
<P><B>Abstract</B></P> <P>We report novel two-dimensional (2D) shaped carbon nanotube (CNT) field emitters using triangular-shaped CNT films and their field emission properties. Using the 2D shaped CNT field emitters, we achieved remarkable field emission performance with a high emission current of 22mA (equivalent to an emission current density >10<SUP>5</SUP> A/cm<SUP>2</SUP>) and long-term emission stability at 1mA for 20h. We also discuss the field emission behavior of the 2D shaped CNT field emitter in detail.</P>
조국희(Kook-Hee Cho),전석기(Seok-Gy Jeon),정순신(Sun-Shin Jung),이홍식(Hong-Sik Lee) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
산업용 가열, 건조, 해동 기술 분야에서 피 가열물의 열전달 특성이 좋지 않은 경우 대출력 마그네트론을 적용하여 전자파 가열방식을 이용함으로써 기존의 가열망식 보다 효율을 상당히 개선할 수 있음은 오래 전부터 알려져 왔다. 그러나 국내에서는 대출력(30㎾급 이상) 마그네트론 제조기술 및 성능 분석을 할 수 없어 외국에서 수입하여 산업에 산발적으로 적용하고 있는 실정이다. 따라서 본 연구는 30 ㎾급 대출력 마그네트론과 구동전원을 위한 시험 장비를 구축하여 신뢰성을 확보하면 마그네트론을 이용한 고효율 가열, 건조, 해동 기술에 적용이 가능하다.