Effects of transport current and columnar defects on the rf penetration depth of NbSe2.

We report on simultaneous measurements of the dc critical current and rf penetration depth of superconducting 2[ital H]-NbSe[sub 2]. We observed that the large peak in the dc critical current (the peak effect'') occurs at the same applied magnetic field [ital H]([ital T]) as a maximum in the rf penetration depth, indicating that the anomaly in flux-line dynamics is associated with a change in flux-line pinning strength. The anomalies in the critical current and rf penetration depth disappear in a sample with a high density of columnar defects produced by Ag-ion bombardment; both superconducting and charge-density-wave phase transitions are substantially broadened by the defects.