Retrospective Rn-220 measurements by compact discs

This work studies the possibility for retrospective ²²⁰Rn measurements by alpha-track etching of the back side (the labeled side) of home-stored CDs. It was already shown that such measurements are feasible, if the front side of the CD is etched, but these measurements require to correct the signal for the presence of ²²²Rn. To the best of our knowledge, this is the only method for retrospective thoron measurement described in the literature. Our preliminary results presented here show that the coating on the back side of the CD prevents ²²²Rn influence on ²²⁰Rn measurements. Moreover, it appears that the signal at the back side is an order of magnitude greater than that at the front side, which would significantly improve the sensitivity of the method. Thus, the approach proposed in this work gives new practical means for retrospective thoron measurements.