Study of stability and electric losses in a superconducting helicoid

The 'critical state' stability and electrical losses in a laboratory superconducting helicoid were experimentally and theoretically studied. It has been found that at the design current density j<or approx. 7.107 A/m2 the helicoid has stationary stability and the charging rate B<or approx. 10-2T/s guarantees that the 'critical state' of the coil will be achieved at 4.2 K. The measurements of the loss made it possible to determine the characteristic decay time of the 'critical state' (1500 s) and the heat flow at the moments of appearance of the flux jumps (q=(150±10)W/m2). The analytical expressions derived for the losses and the boundary of dynamic stability explain well the experimental results. 11 refs.; 20 figs