Measurement of energy dissipated in superconductors during flux jumps

Abstract

The energy dissipated, during field cycling and during flux jumps, has been calculated from measurements of specimen temperature on samples of Pb-Bi eutectic alloy. The dissipation thus calculated is compared with that obtained directly from the area of the magnetization curves. The agreement is well within experimental error. The energy dissipated ΔW during three types of flux jump has been measured. For complete flux jumps with no flux penetration of the sample between jumps, ΔW is found to be equal to ½ΔBΔH. For complete flux jumps with flux penetration between successive jumps, ΔW is found to be equal to ¾(ΔB)². For partial flux jumps ΔW is equal to between (H−B) ΔB and 25(H−B) ΔB, showing that much of the extra flux introduced during the jump is concentrated near the centre of the sample. These results are entirely consistent with the description of flux jumps in terms of the critical state model of irreversible type II superconductors.