“…for the Large Hadron Collider) lies between 10 and 12 T. However, most investigations with the goal of enhancing the critical current density, j , , of Nb,Sn multifilamentary wires have so far led to considerable progress only at high fields ( B > 18 T). The latter were obtained by adding elements like Ta [l-31 or Ti [4], which are dissolved in the Nb,Sn phase, thus leading to higher p. values and in turn to enhanced B,, values. However, the beneficial effect on j , at high fields observed for Ta or Ti added to Nb,Sn wires is always combined with a lowering ofj, at lower fields, the crossover of j , against B taking place at N 11 T [3, 41. This lowering of j , at lower fields has so far not been fully understood, the indications for a possible reduction of the average A15 grain size given by various authors being contradictory.…”