부산대학교 도서관

A limb size MRI magnet coldmass has been constructed using DI-BSCCO tapes from Sumitomo. The coils were wound with epoxy pre-impregnated fiberglass cloth (pre-preg) between layers to bond the wires. For radial dimensional control, temperature was elevated during the winding to thin out the epoxy and to adjust the pre-preg cloth layer thickness in order to control the coil build up. The wire tension was controlled within 1 kg with a set of moving pulleys. While the coils appeared solid after winding and curing, issues were found in the leads between coils. When the coldmass was cooled down to liquid nitrogen $({\rm LN}_{2})$ temperature, breaks in wire leads were found. Thermal expansion and contraction mismatch between the coil bobbin and the BSCCO tape was attributed to the leads break. The thermal stress was induced both in the oven curing and the ${\rm LN}_{2}$ cooling processes. Preliminary testing results at ${\rm LN}_{2}$ temperature are discussed. The magnet was designed to have a center field of 1.5 T operating at a liquid neon (LNe) temperature of 27 K.