중이온가속기용 고온초전도 사극자석의 구조 설계 및 열적 특성 연구 = Investigation on the Mechanical Design and Thermal Characteristics of HTS Quadrupole Magnet for Heavy Ion Accelerator

다국어 초록 (Multilingual Abstract)

Heavy ion accelerator generates rare isotopes using a collision of a accelerated heavy ion with a targe for the research purpose in nuclear science, atomic science, material science and biology. When using IF (In-flight Fragment) system, neutron is scattered during the collision and it acts as an intensive heating source in separator magnets after the target.
As a beam power increases, the neutron radiation heating increase and it hinders the use of LTS (Low Temperature Superconductor) magnets due to the cooling cost of a helium refrigeration system and reduced thermal stability of the LTS magnets. Recently, HTS (High Temperature Superconductor) magnets and MIC (Mineral Insulation Cable) magnets are considered as a promising option to overcome these obstacles. By using a HTS　magnet, it is possible to generate strong magnetic field with an elevated temperature around 40~50 K to reduce the cooling cost and increase the thermal stability.
This theses describes the development of a prototype HTS quadrupole magnet, focussing on the mechanical/thermal design and cooling experiments. Mechanical design was carried out to secure mechanical stability against strong electromagnetic force and reduce conduction heat loss through a beam tube. Thermal analysis was performed to estimate the total heat loss to the magnet and design cooling channels installed around the magnet.
Since the magnets was designed to be cooled by circulation of helium gas, a stand alone helium gas circulation refrigeration system was also developed using GM cryocoolers, a cryogenic blower, heat exchangers and so on. Using the refrigeration system, the magnet was successfully cooled down to operation temperature and an optimum operation parameters were obtained by varying the helium pressure and mass flow rate. To find an optimum operation parameters of the refrigeration system, helium charging pressure and rotating speed of the blower were adjusted from 5 to 8 bar and 6,000 to 12,000 rpm. Through the experiment it was possible to obtain the optimum parameters as 8 bar and 9,000 rpm which minimize the magnet temperature. In addition, the heat loss of the magnet was obtained using the measured temperature difference and the mass flow rate of helium gas, and it showed good agreement with the thermal analysis results.
This design process and experimental results will be used to develop a practical HTS quadrupole magnets, which can be used as a pre-separator of the IF system in heavy-ion accelerators, in near future. The helium circulation refrigeration system can also be used for various industrial HTS magnet applications.

목차 (Table of Contents)

• I. 서 론 1
• 1. 연구 배경 1
• 2. 연구 목적 6
• II. 중이온 가속기용 고온 초전도 사극자석 설계 8
• 1. 고온 초전도 사극자석의 전자기설계 8
• 2. 고온 초전도 사극자석의 구조설계 13
• 3. 고온 초전도 사극자석의 열적설계 32
• 1) 고온 초전도 사극자석의 열침입량 계산 32
• 2) 고온 초전도 사극자석의 헬륨 냉각유로 설계 43
• 4. 고온 초전도 사극자석의 제작 조립 49
• III. 기체헬륨 순환 냉각시스템의 설계 54
• 1. 기체헬륨 순환 냉각시스템 구성 54
• 1) 극저온 냉동기의 선정 54
• 2) 극저온 블로어의 선정 57
• 3) 기타 부속품 61
• 4) 내부배관 설계 65
• 2. 기체헬륨 순환 냉각시스템의 제작 67
• 3. 기체헬륨 순환 냉각시스템의 시운전 70
• IV. 기체헬륨 순환 냉각시스템을 이용한 사극자석 시제품의 시운전 73
• 1. 기체헬륨 순환 냉각시스템을 이용한 모듈코일의 성능평가 73
• 2. 사극자석 시제품의 시운전 83
• 1) 냉각시운전 85
• 2) 사극자석의 최적운전조건 도출 89
• 3) 사극자석 시제품의 운전전류통전 시험 95
• V. 결 론 98
• 참고문헌 101
• Appendix 중성자 의한 복사발열에 따른 사극자석의 냉각특성 106
• Abstract 110
• 감사의 글 112