The range of ²⁰⁸Tl from ²¹²Bi decay in collodion thin films

We measured the effective range of ~116 keV ²⁰⁸Tl ions in extremely thin films of Collodion (C₆H₈N₂O₉). The ²⁰⁸Tl ions were obtained from the α decay of ²¹²Bi, being emitted in the ²²⁰Rn decay chain. The amount of the stopped ²⁰⁸Tl ions in each Collodion film was determined by measuring the short-lived (~3 m) β activity of ²⁰⁸Tl where the effective range was found to be 11.69 ± 0.35 µg/cm². This value is in agreement (~15%) with Monte Carlo simulations using the SRIM and TRIM software packages which calculate the ions average range in Collodion resulting in a value of 10.14 ± 0.31 µg/cm². The range of the 116 keV ²⁰⁸Tl ions in Collodion as measured here was found to be ~11% larger than the literature range in Carbon of the 120 keV doubly charged ²⁰⁵Tl ions (produced by an accelerator) and reported to be 10.5 µg/cm². In Carbon, the measured value was also higher than the SRIM simulated value by ~11%. The results seem also to reveal no dependence on the charge of the projectile. We also found that the measured spectrum width is wider by a factor 2.4 than the simulated value. We attribute this deviation to a partial energy reduction of ²⁰⁸Tl ions resulting from both diffusion and decay of the ²²⁰Rn and its daughters into the Al substrate holding the source, to errors in the film thickness and also to an overestimation of the SRIM stopping power. Graphical Abstract: [Figure not available: see fulltext.].