• 한국초전도ㆍ저온공학회논문지
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• 제21권3호
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• pp.22-26
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• 2019

With an increasing potential to realize quantum computer, it has recently been an important issue to extend the capabilities of RF cavities to maintain longer coherent quantum system. Using superconductors instead of normal metals allows the quantum system to have a substantially enhanced quality factor. In this paper, surface impedances of superconducting cavities are calculated by the Mattis-Bardeen theory with Python & MATLAB programs. With a simulation of electromagnetic field distribution, the sensitivity to dielectric and surface losses of the superconducting cavities are determined. Then calculations of the resonance frequency and quality factor of three-dimensional superconducting resonators made of Al or Nb are discussed.

• 한국초전도ㆍ저온공학회논문지
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• 제16권3호
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• pp.15-20
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• 2014

The heavy ion accelerator that will be built in Daejeon, Korea utilizes superconducting cavities operating in 2 K. The cavities are QWR (quarter wave resonator), HWR (half wave resonator), SSR1 (sing spoke resonator1) and SSR2. The main role of the cryomodule is supplying thermal insulation for cryogenic operation of the cavities and maintaining cavities' alignment. Thermal and structural consideration such as thermal load by heat leak and heat generation, cryogenic fluid management, thermal contraction, and so on. This paper describes detailed design considerations and current results have being done including thermal load estimation, cryogenic flow piping, pressure relief system, and so on.

• 한국초전도ㆍ저온공학회논문지
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• 제16권3호
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• pp.21-25
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• 2014

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, it is called as, superconducting contactless power transfer for EV (SUWPT4EV) system. As the HTS coil has an enough current density, it can deliver a mass amount of electric energy in spite of a small scale antenna. The SUCPT4EV system has been expected as a noble option to improve the transfer efficiency of large electric power. Such a system consists of two resonator coils; HTS transmitting antenna (Tx) coil and normal conducting receiver (Rx) coil. Especially, the impedance matching for each resonator is a sensitive and plays an important role to improve transfer efficiency as well as delivery distance. In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, within 45 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 15% compared with copper antenna. In addition, we achieved effective impedance matching conditions between HTS antenna and copper receiver at radio frequency (RF) power of 370 kHz.

• 한국초전도ㆍ저온공학회논문지
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• 제17권4호
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• pp.43-46
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• 2015

The heavy ion accelerator that will be built in Daejeon utilizes four types of superconducting cavities. Cryomodules holding the superconducting cavities in them supply thermal insulation for cavities operating in 4.3 K or 2.1 K. A Prototype of cryomodule which holds two HWR (Half Wave Resonator) cavities was fabricated and tested. Since the operating temperature of the HWR is 2.1 K, the superfluid helium was generated with warm vacuum pumping system. The cyromodule was successfully cooled down below lambda point temperature of helium and any detectable leak was not observed during the test. The static thermal load at 4.2 K was measured. The result and the experience for the cool-down below lambda point of helium are reported in this paper.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.42-42
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• 2002

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.389-392
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• 1996

The recent development of high temperature superconducting epitaxial thin film offer great potential for planar passive microwave application such as ring resonator, filters, transmission lines, and antennas. This paper describes the fundamental properties of Microstrip Band-Pass Filter using HTS Thin Film and its application to microwave devices. In order to fabricate HTS microstrip multiple filters, We have grown laser ablated HTS thin films, patterned by photolithographic process and wet etching processes intro HTS microwave devices.

• Progress in Superconductivity
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• 제4권2호
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• pp.132-136
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• 2003

Extremely selective high temperature superconducting (HTS) band -pass filters were developed for the base transceiver station applications of Digital Cellular communication Service (DCS). The filters have a bandwidth of 25 MHz at a center frequency of 834 MHz. There are 12 resonators which have spiral-meander microstrip-line structures in order to reduce far-field radiations with a reasonable tunability. As a result, the size of filters is 5 mm $\times$ 17 mm $\times$ 41 mm. Device characteristics exhibited a low insertion loss of -0.4 dB with a -0.2 dB ripple and a return loss better than -10 dB in the pass-band at 65 K. The out-of-band signals were attenuated better than 60 dB about 3.5 MHz from the lower band edge, and 3.8 MHz from the higher band edge.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1777-1783
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• 2020

As a part of R&D work for the high intensity proton linac of China Accelerator Driven Sub-critical System project, a superconducting half-wave cavity with a frequency of 162.5 MHz and an optimal beta of 0.15 (HWR015) has been developed at Institute of Modern Physics (IMP), Chinese Academy of Sciences. In this paper, the design and test results will be described in detail. We introduced a new stiffening strategy for the HWR cavity, the simulation results show that the cavity has much lower frequency sensitivity coefficient (df/dp), Lorentz force detuning coefficient (KL), and can achieve more stable mechanical properties. The performance of the HWR cavity operated in cryostat will be also reported.

• 대한전자공학회논문지TE
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• 제37권1호
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• pp.63-69
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• 2000

"H" 형태의 공진기로서 이루어진 초전도 안테나는 비슷한 크기를 가진 마이크로스트립 안테나에 비하여 소형화에 유리하다. "H"형 초전도 안테나 제작을 위해 rf 마그네트론 스퍼터링을 이용하여 $YBa_2Cu_3O_{7-x}$ (YBCO)/MgO 고온초전도 박막을 제조하였으며 표준 식각법을 이용하여 안테나를 형상화 하였다. 일반 금속과의 특성을 비교하기 위해서 동일한 차원의 금 안테나가 제작되었다. 개구 결합 방식을 이용하여 초전도 안테나 패치와 $50{\Omega}$ 급전선을 임피던스 결합을 시켰다. 다양한 종류의 실험 결과가 반사손실, 공진주파수, 특성임피던스 등을 중심으로 보고되었다. H형 초전도 안테나는 금 안테나에 비하여 정재파비에서 0.36 효율에서 24% 반사손실에서 14.6bB 이상 더 우수한 성능을 보여주었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권5호
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• pp.326-332
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• 1999

In this paper, we designed and fabricated High-Tc Superconducting (HTS) microstrip bandpass filters using Stepped Impedance Resonators(SIR) and studied on their characteristics. The $high-T_c$ superconducting $Y_1Ba_2Cu_3O_{7-x}$ epitaxial films were deposited by Pulse Laser Deposition (PLD) system on MgO. The fabricated filters were designed so as to operate in Ku band with central frequency 17.25 GHz, bandwidth 2.896% and ripple 0.01 dB. These filters were composed of parallel coupled microstrip SIR of which impedance ratio (K) are 0.5, 1.5. In the measured response, HTS filters had showed insertion loss below -0.5 dB. For comparison with normal conducting filter, we fabricated the Au counterpart that consists of the resonators as K=1.5 in the same dimension and measured performance of the Au filter. In comparison, HTS filter designed optimally got superior response to gold conterpart.