Effect of radiation damage on the charge-density-wave dynamics in NbSe3

We have used 2.5-MeV protons to produce radiation damage in NbSe3, in a homogeneous controlled manner. The defect concentration was varied from 10 to 500 ppm in order to study the effects of pinning on the charge-density-wave motion. Measurements were made of the nonlinear conductivity, the threshold electric field, and the dielectric constant and conductivity as a function of frequency in the range 0-100 MHz. We find that the threshold field and the reciprocal dielectric constant vary linearly with the defect concentration and hence the restoring force.