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Fabrication and Characterization of 4-T/203 mm RT Bore 2G HTS Magnet With No-Insulation Method
Sangwon Yoon,Kyekun Cheon,Hunju Lee,Seung-Hyun Moon,Sun-Young Kim,Yungil Kim,Sang-Ho Park,Kyeongdal Choi,Gye-Won Hong Institute of Electrical and Electronics Engineers 2014 IEEE transactions on applied superconductivity Vol.24 No.3
<P>We fabricated superconducting magnet using second-generation (2G) high-temperature superconducting wire by SuNAM. Magnetic field strength at the center is 4 T, and room temperature bore diameter is 203 mm. The magnet consists of 30 double pancake coils (DPCs) with the inner diameter of 245 mm and outer diameter of 297 mm. All double pancakes were wound by no-insulation method and performance were tested separately before assemble. Tested DPCs were resistively connected by HTS tape(splice joint), and assembled coil was conduction cooled by a two-stage Gifford-McMahon cryo-cooler to the operating temperature of 8 K. The size of magnet is 452 mm in height. Current, voltage, and field strength were measured as a function of time with various ramping up and down conditions and results were compared with the simulated behavior. The coil generates 4 T when operating current ramped to 205 A by 0.03 A/s without quench. Initial cool down time was 72 h and the measure field homogeneity in 10 mm DSV was 0.015% and 0.012% in radial axis and vertical axis, respectively. The results showed that no-insulation winding method is a possible option for making compact magnet coil with sufficient structural integrity, thermal and electrical stability at the same time. The magnet showed quench at field strength of 4.49 T when ramped with 0.2 A/s to 235 A. The magnet showed same performance after recovery from quench.</P>
Sangwon Yoon,Kyekun Cheon,Hunju Lee,Seung-hyun Moon,Ilkyu Ham,Yungil Kim,Sang-ho Park,Hyeonggil Joo,Kyeongdal Choi,Gye-Won Hong IEEE 2013 IEEE transactions on applied superconductivity Vol.23 No.3
<P>A conduction-cooled high-temperature superconducting magnet using 2nd generation HTS wire, which has a room-temperature bore 102 mm in diameter, has been developed and tested up to 3 T with the operating temperature of 20 K. The magnet consists of 22 double pancake coils (DPCs) with an inner diameter of 140 mm and outer diameter of 182 mm. Twenty-two double pancake coils were tested separately at 77 K for checking the <I>IV</I>-curve. Selected DPCs were resistively connected by HTS tape (Splice joint), and an assembled magnet coil with the size of 182.5 mm diameter and 242 mm in height was conduction cooled by a two-stage Gifford-McMahon cryo-cooler to 20 K. Current, voltage, and field strength were measured as a function of time with various ramping up and down conditions. The resulting performance data of the assembled magnet agreed well with the expectation from FEM simulation. The aimed field homogeneity of 0.1% in 10 mm diameter sphere volume was proved when operating current was 141.6 A at 20 K with central magnetic field intensity of 2.9975 T by hall sensor. The magnetic flux density at center showed nonlinear dependence with ramping current within the range of 0.05 A/sec ~0.15 A/sec because of charging delay. However, saturated magnetic flux density showed the same value of 2.9975 T regardless of ramping rate.</P>
Vision Inspection Methods for Uniformity Enhancement in Long-Length 2G HTS Wire Production
Jae-Hun Lee,Byoung-Jean Mean,Tae-Jin Kim,Young-Soon Kim,Kyekun Cheon,Taehoon Kim,Dae-Gwan Park,Dae-Won Song,Ho-Kyum Kim,Woosuk Chung,Hunju Lee,Seung-Hyun Moon Institute of Electrical and Electronics Engineers 2014 IEEE transactions on applied superconductivity Vol.24 No.5
<P>With much effort devoted by many research groups, the performance of 2nd generation (2G) superconducting wires, also called coated conductors (CC), was drastically improved, leading to many meaningful and impressive demonstrations of electric power devices. Now that the performances such as critical current, in-field characteristics, and mechanical strengths became sufficient to the application, the attention has moved to how we can produce long 2G wires with high uniformity. Many in-line inspection tools are tested and introduced to address these challenges. In this paper, we describe two methods that we adopted for in-line monitoring and feedback control of layer deposition. One is for texture control of ion beam assisted deposition (IBAD) of an MgO layer through reflection high-energy electron diffraction (RHEED) pattern monitoring and analysis. The other is for composition control of a superconducting layer through surface color observation and control of metal source evaporation rates. By applying the above two methods, we achieved in-plane texture of about 4.8 ° in the MgO layer, as measured by FWHM of phi-scan of (220) peak, and the critical current of 750 A/12 mm width in the GdBCO layer along the length of more than 650 m, with excellent uniformity.</P>
Jang, Jae Young,Yoon, Sangwon,Hahn, Seungyong,Hwang, Young Jin,Kim, Jaemin,Shin, Kang Hwan,Cheon, Kyekun,Kim, Kwanglok,In, Sehwan,Hong, Yong-Ju,Yeom, Hankil,Lee, Hunju,Moon, Seung-Hyun,Lee, SangGap IOP 2017 Superconductor science & technology Vol.30 No.10
<P>A conduction-cooled 3 T 100 mm winding bore multi-width and no-insulation (NI) all-REBCO magnet was designed, constructed and tested at 13 K. The magnet consists of a stack of double pancake (DP) coils wound with, for the first time, REBCO tapes having a 1 <I>μ</I>m <I>thick layer of stainless steel</I>, named ‘metallic cladding’, that surrounds the tapes in a hermetic way to substantially reduce the NI charging delay. After construction, the magnet was cooled down to the target operating temperature of 13 K using a two-stage pulse-tube cryo-cooler. During charging–discharging tests up to 200 A, magnetic center field, voltage of each DP coil, power supply current, and magnet temperature were monitored. The charging time constant of the magnet was measured to be about 10.1 s, 13 times smaller than that of its NI counterpart. The magnet experienced, due to an unexpected power supply trip, a sudden discharge at a peak coil current density of 353 A mm<SUP>2</SUP>, yet it survived without any degradation. The results demonstrated strong potential of the metallic cladding NI-REBCO magnet for significant charging-delay reduction and self-protecting operation.</P>