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 2H-NbSe2. We observed that the large peak in the dc critical current (the ''peak effect'') occurs at the same applied magnetic field H(T) as a maximum in the rf penetrati on depth, indicating that the anomaly in flux-line dynamics is associa ted 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 substan tially broadened by the defects.