Factors affecting the registration and counting of alpha tracks in solid state nuclear track detectors

Abstract

:In view of the fact that the radon progeny contribute the highest to the natural radiation dose to general populations, large scale and long-term measurements of radon and its progeny in the houses have been receiving considerable attention. Solid State Nuclear Track Detector (SSNTD) based systems, being the best suited for large scale passive monitoring, have been widely used for the radon gas (using a cup closed with a semi-permeable membrane) and to a limited extent, for the measurement of radon progeny (using bare mode in conjunction with the cup). These have been employed for radon mapping and indoor radon epidemiological studies with good results. In this technique, alpha tracks recorded on SSNTD films are converted to radon/thoron concentrations using corresponding conversion factors obtained from calibration experiments carried out in controlled environments.The detector response to alpha particles depends mainly on the registration efficiency of the alpha tracks on the detector films and the subsequent counting efficiency. While the former depends on the exposure design, the latter depends on the protocols followed for developing and counting of the tracks. The paper discusses on parameters like etchant temperature, stirring of the etchant and duration of etching and their influence on the etching rates on LR-115 films. Concept of break down thickness of the SSNTD film in spark counting technique is discussed with experimental results. Error estimates on measurement results as a function of background tracks of the films are also discussed in the paper.

Inhalation Dose and Source Term Studies in a Tribal Area of Wayanad, Kerala, India

“…As the passive measurements using the pinhole dosimeters may be influenced by factors like the bulk etching rate, leakage from the cup, and so forth [ 36 ], active measurements were done to ascertain and validate the concentration obtained using pinhole dosimeters. Ten houses including the houses showing higher radon and thoron concentrations were intensively studied.…”

Effect of Gamma Rays on The Bulk Etching Rate of LR-115 Detector

“…The bulk etch rate is the removing rate of the undamaged surface of the detector by chemical reaction between the surface of detector material and etching solution, which due to removal of material from the detector surface. During etching, the material of detector is removed layer by layer and the detector thickness becomes smaller and smaller [8]. When a heavily ionizing charged particle passes through such materials, it leaves a narrow trail of damage of a few angstroms in diameter along its path [9].…”