Microstructural Investigation of PM-355 Nuclear Track Detector Subjected to Low-Dose Gamma Irradiation: A Positron Annihilation Lifetime Study

Emad Hassan Aly

doi:10.4236/msa.2013.410076

Abstract

Samples of the PM-355 polymeric solid state nuclear track detector were exposed to low gamma absorbed doses from 1 kGy (0.1 Mrad) up to 9 kGy (0.9 Mrad). Positron annihilation lifetime (PAL) in conjunction with transmission electron microscopy (TEM) and Thermo-gravimetric analysis (TGA) were performed on irradiated and pristine samples at room temperature. The observed lifetime spectra were resolved into three components where the ortho-positronium (o-Ps) lifetime component was associated with the pick-off annihilation of positronium trapped by the free volume. PAL studies of irradiated PM-355 samples showed that ortho-positronium (o-Ps) lifetime increases with an increase in dose up to 4 kGy and decreases at higher doses. In contrast, the intensity of the o-Ps component, I3, decreases with the dose up to about 2 kGy, followed by a much smooth decrease up to 7 kGy, and then it levels off. TGA analysis indicated that the PM-355 detector decomposed in one main breakdown stage. These results are discussed on the basis of chemical and physical changes occurring at the microscopic level in the PM-355 due to irradiation. Crosslinking dominates for doses between 1 and 4 kGy, while the degradation mechanism (Chain scission) prevails for doses up to 9 kGy.

Highlights

Polymeric materials are, at the present, extensively recognized as being of substantial meaning in a broad diversity of immense industrial and scientific interest [1]
Positron annihilation lifetime (PAL) studies of irradiated PM-355 samples showed that ortho-positronium (o-Ps) lifetime increases with an increase in dose up to 4 kGy and decreases at higher doses
Since radiation is one of the major factors that change the structural properties of polymers, in particular solid-state nuclear track detectors (SSNTDs), it would be meaningful to study the modification on their properties due to irradiation

Summary

Introduction

At the present, extensively recognized as being of substantial meaning in a broad diversity of immense industrial and scientific interest [1]. Since radiation is one of the major factors that change the structural properties of polymers, in particular solid-state nuclear track detectors (SSNTDs), it would be meaningful to study the modification on their properties due to irradiation. Solid-state nuclear track detectors have found a variety of applications in different fields of science and technology [2]. These detectors have recently found extensive applications in plentiful high-temperature plasma experiments for corpuscular diagnostics. An allyldiglycol polycarbonate (CR-39) plastic is one of the applicants for dosimeter material, having a dose response in an elevated gamma dose region. The particular CR-39 polymer PM-355 is of explicit concern, finding assorted applications in physical and technological sciences [7]. The PM-355 plastic appeared to be the most excellent one, for the recognition of light ions including protons, deuterons, He-, C-, and S-ions, and this detector was principally used in the plasma experiments [9] and was suggested as an appropriate analytical tool for the laser-plasma experiment [10]

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