33 research outputs found
Thermal Diffusion and Quench Propagation in YBCO Pancake Coils Wound with ZnO-and Mylar Insulations
The thermal diffusion properties of several different kinds of YBCO
insulations and the quench properties of pancake coils made using these
insulations were studied. Insulations investigated include Nomex, Kapton, and
Mylar, as well as insulations based on ZnO, Zn2GeO4, and ZnO-Cu. Initially,
short stacks of YBCO conductors with interlayer insulation, epoxy, and a
central heater strip were made and later measured for thermal conductivity in
liquid nitrogen. Subsequently, three different pancake coils were made. The
first two were smaller, each using one meter total of YBCO tape present as four
turns around a G-10 former. One of these smaller coils used Mylar insulation
co-wound with the YBCO tape, the other used YBCO tape onto which ZnO based
insulation had been deposited. One larger coil was made which used 12 total
meters of ZnO-insulated tape and had 45 turns. The results for all short sample
and coil thermal conductivities were ~1-3 Wm-1K-1. Finally, quench propagation
velocity measurements were performed on the coils (77 K, self field) by
applying a DC current and then using a heater pulse to initiate a quench.
Normal zone propagation velocity (NZP) values were obtained for the coils both
in the radial direction and in the azimuthal direction. Radial NZP values
(0.05-0.7 mm/s) were two orders of magnitude lower than axial values (~14-17
mm/s). Nevertheless, the quenches were generally seen to propagate radially
within the coils, in the sense that any given layer in the coil is driven
normal by the layer underneath it.Comment: 58 pages, 5 tables, 16 fig
Inhibitory Effects of Prior Low-dose X-irradiation on Ischemia-reperfusion Injury in Mouse Paw
We have reported that low-dose, unlike high-dose, irradiation enhanced antioxidation function and reduced oxidative damage. On the other hand, ischemia-reperfusion injury is induced by reactive oxygen species. In this study, we examined the inhibitory effects of prior low-dose X-irradiation on ischemia-reperfusion injury in mouse paw. BALB/c mice were irradiated by sham or 0.5 Gy of X-ray. At 4 hrs after irradiation, the left hind leg was bound 10 times with a rubber ring for 0.5, 1, or 2 hrs and the paw thickness was measured. Results show that the paw swelling thickness by ischemia for 0.5 hr was lower than that for 2 hrs. At 1 hr after reperfusion from ischemia for 1 hr, superoxide dismutase activity in serum was increased in those mice which received 0.5 Gy irradiation and in the case of the ischemia for 0.5 or 1 hr, the paw swelling thicknesses were inhibited by 0.5 Gy irradiation. In addition, interstitial edema in those mice which received 0.5 Gy irradiation was less than that in the mice which underwent by sham irradiation. These findings suggest that the ischemia-reperfusion injury is inhibited by the enhancement of antioxidation function by 0.5 Gy irradiation
Hyperconductivity in chilled beryllium metal
It is shown that in the vicinity of 77 K beryllium has a superior specific conductance compared with the nominally excellent metallic conductors aluminum and copper. It is concluded that beryllium should be considered for some conduction applications, despite its well known toxicity problems