Dislocation mobility in pure copper at 4.2 °K

Torsional stress pulses of several microseconds duration were applied at 4.2 °K to cylindrical single crystals of copper containing freshly introduced dislocations. Dislocation displacements were measured by means of a double-etch technique, and subsequently the dislocation damping coefficient B was determined to be equal to 0.8 × 10-5 dyn sec/cm2. While B decreases monotonically with decreasing temperature, the value of B at 4.2 °K is greater than that predicted from theoretical calculations of the interaction between a moving dislocation and the conduction-electron gas in copper.