Investigations of factors affecting the use of uranium metal as a source of alpha particles for the evaluation of alpha track detectors

Abstract

The original goal of the present thesis was to compare several Solid State Nuclear Track Detectors (SSNTD) as alpha particle detectors. The SSNTD to be compared were different polycarbonates and a cellulose nitrate detector. For this purpose, an uranium foil was used as the alpha particle source. The foil created new problems which needed to be studied in detail. Among these problems, the effect of the thickness of the oxide layer on the uranium metal foil surface was the most important. To study this effect, Kodak-Path6 LRI 15 films (cellulose nitrate) were used, in association with an established etching process: 145 minutes at 60'C in a 10% NAOH solution. This study also presented an opportunity to obtain more knowledge of the etching process, resulting in the improvement of the etching efficiency. The experiments showed that the relative position (horizontal or vertical) of the film in the etching bath was important. It also demonstrated a dramatic effect of the age of the etching solution on the etching efficiency and also showed that the age of the detectors is also a parameter to be considered. With these experiments, other parameters were identified which required greater study, such as the ratio of the volume of the etching solution to the detector area to be etched. Once the etching process was improved and set, a study of the attenuation effect of the oxide layer was performed. It appeared that, from 0 to 1.31 mg.cm-2, the thickness has an important effect on the exposure rate. However, for thicknesses above this value, the exposure rate remains constants This proved that the oxide layer thickness of the uranium foil should not be of concern once it reaches 1.31 Mg.CM-2. Therefore, the comparison initially planned could now be continued. However, this study strongly suggests that the effect of the age of the detector and the ratio of the volume of the etching solution to the area to be etched should be studied for the LR I 15 films before additional comparisons could be performed.