OVERALL CRITICAL-CURRENT DENSITY OF CHEVREL WIRES AT HIGH MAGNETIC-FIELD

Wires of Pb1-xSnxMo6S8 (PSMS) using the powder-in-tube process have be en carefully drawn and the critical current density J(c) has been meas ured on small coils wound with wires of 1.5 meterin lenfth in magnetic fields up to 24 tesla. At 1.9K, we achieved an overall critical curre nt density J(co), exceeding slightly 100 A/mm(2) at 20 tesla and 63 A/ mm(2) at 24 tesla, Below 18 tesla, we always observed an abrupt occurr ence of the resistive state, indicating that in this region J(c) is li mited by local defects, generally located at the ends of the coil. Nev ertheless, at 15 tesla and 4.2K, J(c) reaches 550 A/mm(2), These very good results are the consequence of a better choice of the materials f orming the wire and of a full control of the synthesis of the PSMS pow der. The analysis of the field dependence of J(c) shows that the grain s are well connected, but that the critical field B-c2 is still too lo w at 4.2K (31 tesla instead of 50 tesla). An optimization of the annea ling conditions is expected to considerably increase J(c) at high magn etic fields.