Alternative Approach to Extract the Bulk Etching Rate of PADC Nuclear Detector

Abstract

The paper aims to propose the maximum track length (L max ) measurement as an alternative approach to evaluate and extract the bulk etch rate (V b ) of the nuclear detector PADC CR-39, and compare it with the results obtained by the removal layer thickness measurement of the etched detector. The alternative L max -method mainly relies on the measuring the length of the etched tracks, their maximum values and saturation times from the obtained track profile images. The detectors were irradiated with different energies of alpha particles emitted from the 241 Am source and then etched in a 6.5 N NaOH solution at 701 o C for different successive time intervals. In order to calculate V b , the maximum length of the tracks and their saturation times were determined corresponding to the energies of the alpha particles used. A direct proportion between the maximum length of the tracks and the energy of the alpha particle was observed. However, the value of V b is found to be 1.3440.0202 m h -1 obtained using the L max -method, and it was consistent with that computed by the method based on the measurement of the thickness difference of the etched detector which was 1.3540.065 m h -1 . Keywords ISSN: 0067-2904Al-Nia'emi Iraqi Journal of Science, 2018, Vol. 59, No.2B, pp: 856-864 857 IntroductionThe solid-state nuclear track detectors (SSNTDs) are considered as reliable means to detect the charged particles. The poly allyl diglychol carbonate (PADC) polymer is regarded as one of the most favorite types of SSNTDs, especially the well commercially known detector CR-39 which is widely utilized in different fields of sciences. This preferred standpoint is due to its high sensitivity to the charged particles and protons recoil of neutrons [1,2,3]. However, a review of SSNTD's properties can be seen elsewhere [4].It is well-known that the track creation and development in SSNTDs is strongly controlled by two essential parameters, the track etch rate (V t ) along the track depth in the detector, and the bulk etch rate (V b ) in undamaged areas of the detector, respectively. The shape development of the etched track passes through two phases or stages [5]. The first one is the acute-conical phase through which the track develops into a sharp conical etch pit when V t >V b . Whilst when the etching solution passes the end of the damaged path (i.e the end of the particle range) in the detector towards the undamaged region, the track enters the second phase of the development; the over-etched phase where the track develops into a spherical shape etch pit as V t =V b [6].It has been realized that the direct measurement of track lengths is difficult compared to the direct measurement of the track-opening diameters which is relatively simple and straightforward. Nevertheless, the formal description of the track evolution, the monitoring and imaging the profiles (longitudinal cross-sections) of the etched tracks, and measuring their lengths (or depths) have attracted the attention of many researchers to realize the real...