On nature of critical current density limit of Nb3Sn layers

Dependence of critical current density of Nb3Sn homogeneous layer at the temperatures of 4.2 and 2.15 K in the range of fields 3-16.5 Tl have been measured. The dependences obtained satisfy the concept of rigid fixing of fine (1-3 nm) current microstructure (with the density up to 1012 cm-2 and total cross section of ∼10-2) and electronic condensate attaining critical rate in it. The conclusion is made on the threshold of the critical current density obtained (at 10Tl - 106 A/cm2 without the field of ∼6·106 A/cm2), constituting ∼0.02-0.03 of the utmost possible one