Fusion Programme - ENEA - Fusione

4. Superconductivity2007 Progress ReportHeaterV +5 cmV 26 cmV 12.6 cmV 02.5 cmV 36 cmNZPV (cm/s)2.075 K65 K1.000 50 100 150I bias (A)5 cmV 4V -Fig. 4.27 - YBCO 344-superconductor tape mounted onthe sample-holder for quench experiments. On the right,the layout of voltage tapsFig. 4.28 - NZPV as a function of I bias at 65 and 75 Kwhen the heater is mounted on the YBCO (solidsymbols) and on the Ni side of the tape (open symbols)section; whereas the other is 2D, thus providinginformation on the voltage/temperature evolutionwithin each section of the tape, without anyhomogenization. It is worth noting that thematerial properties of the tape implemented in themodel are based on experimental measurementof each single component and are highly nonlinearcompared to their temperature dependence. Theiterative algorithm is explicit and therefore properconstraints on the maximum time step applicableat each step of integration have been inserted toavoid numerical instabilities. Figure 4.29 reportsthe voltage distribution measured in the simulatedrun and compared with the respectiveexperimental measurements. These activities arefunded by the EFDA Technology WorkProgramme HTSPER task (TW5-TMSC-HTSPER).Voltage (V)Voltage (V)6×10 -34×10 -3T ref =80 K; I bias =45 A; E= 0.57 Jch0ch1ch2ch3ch42×10 -3 a)00 4 8 12 16 20Time (s)1.0×10 -26×10 -3T=80 K; I bias =45 A; E heater = 0.57 Jrun 20 ch0run 20 ch1run 20 ch2run 20 ch3run 20 ch4Fig. 4.29 - a) Simulated and b) measured voltage tracesdue to propagation of the normal zone in YBCO tape2×10 -3 b)00 5 10 15 20Time (s)93