Alpha track registration and revelation in CR-39 using new etching method for ultratrace alpha radioactivity quantification in solution media

A CR-39 based method was developed for measuring the ultra-trace alpha radio activities in aqueous samples having curie levels of γ/β-radio activities. The chemical etching method was optimized to reveal the alpha tracks in CR-39. This new chemical etching method involved the use of a phase transfer catalyst tetraethylammonium bromide which reduced the track revelation induction time without deteriorating the track-etch parameters. The alpha track-etch parameters such as bulk-etch rate, track-etch rate, induction time, and the critical angle of alpha track registration were measured at 60 and 70 °C, with and without using a phase transfer catalyst in the chemical etching for the comparison and optimization. The track registration efficiency of CR-39 in the solution medium was measured using the samples having known alpha activity of mixPu, and value obtained was found to be (4.42 ± 0.12) × 10−4 cm. The registration efficiency value thus obtained was corroborated with the expected efficiency expected from the calculated range of alpha particles in the solution. This CR-39 based method was employed to quantify the alpha activity, as low as 0.2 Bq mL−1, in the aqueous radiopharmaceutical samples having the curie levels of γ/β radio activities.

Updates to TRACK_TEST and TRACK_VISION Computer Programs

The computer programs TRACK_TEST and TRACK_VISION were previously developed to model profiles and optical appearances of tracks developed in solid-state nuclear track detectors. The programs were based on a track development model that involved the bulk etch rate Vb and the track etch rate Vt or the V function (i.e., Vt/Vb). The present work reported our work to update and modify these two programs. In the revised TRACK_TEST, two new V functions were added and enabled. Sample results for the CR-39 detector obtained using the three original and the two new V functions were compared. Discrepancies were within ~10% and <14% for incident alpha-particle energies of 1 MeV and >1 MeV, respectively. Another major revision of TRACK_TEST was to enable calculations for the Makrofol detector. In the revised TRACK_VISION, the two new V functions, as well as the option for the Makrofol detector, were also added. The experimental results on the Makrofol detectors were obtained (irradiated with 3.6-MeV alpha particles under normal incidence and then etched to achieve a removed detector thickness of 30 μm) for comparisons with the modeled results using the revised TRACK_VISION. The track diameters obtained from the experiment and model were 24.7 and 23.2 μm, respectively. Moreover, a bright area in the central parts, together with an outer dark ring, were present in both the simulated and experimental tracks. The track-opening diameters and the general optical appearances of the tracks were in good agreement.

Effects of UV irradiation on Fission-fragment track parameters in Makrofol-E detector

This study gives information about the effects of UV (here, the wavelength is 160 nm) exposure on the bulk etch rate ([Formula: see text], track etch rate ([Formula: see text], the detector sensitivity ([Formula: see text], critical angle ([Formula: see text] and etching efficiency ([Formula: see text] of Makrofol-E Solid State Nuclear Track Detector. The effect of UV on the activation energy of Makrofol-E was also studied. Nine pieces of Makrofol-E Solid State Nuclear Track Detector were separated into three equal sets as set A, set B and set C. Set A, named as reference set (Fission fragment FF), was irradiated to [Formula: see text]Cf source. Set B, called as post-exposed ([Formula: see text]), was first irradiated to [Formula: see text]Cf and then exposed to UV. The process was reversed for set C named as pre-exposed ([Formula: see text]) at the same conditions. From the results, it is concluded that radiation produces small but significant effect on activation energy [Formula: see text] of bulk etch rate for pre-exposed and post-exposed samples. Also, the activation energies [Formula: see text] of track etch rate for post-exposed and Fission fragment samples are within experimental uncertainty. The energy carried by UV radiation may be responsible for cross networking processes occurring during the exposure which results small change in activation energies for both [Formula: see text] and [Formula: see text]. The [Formula: see text] can be increased by hardening detector material of the pre-exposed detector.

Measurement of Truebeam® Head-Leakage by Optically Stimulated Uminescence/Track-Etch Passive Detectors

This work was performed in order to measure the photon and neutron head-leakage values of the TrueBeam® (TB) accelerator. Measurements are compared with the data provided by the manufacturer for TB as well as Clinac.Four higher photon energies (10MV, 10MV FFF, 18MV and 20MV) and electron energy (22MeV) are considered in this study. The electron energy used in this study was the maximum available in this machine. Optically Stimulated Luminescence (OSL) Dosimeters are used for photon head-leakage measurements. Neutron component of the head-leakage was measured using track-etch (CR-39) detectors. Both photon and neutron head-leakage values for TB machine was measured using OSL and track-etch, respectively. These results were compared with the standard values provided by the manufacturer for both TB and Clinac. The study indicates that the higher neutron head-leakage once moved towards the 20MV range of photon energy. Also, the lower head-leakage values were recorded for flattening filter free beam (10MV FFF). It was observed that the photon head leakage value for Clinac was higher, and the neutron head-leakage value was found to be slightly less than the TB values.

Tangential flow microfluidics for the capture and release of nanoparticles and extracellular vesicles on conventional and ultrathin membranes

Membranes have been used extensively for the purification and separation of biological species. A persistent challenge is the purification of species from concentrated feed solutions such as extracellular vesicles (EVs) from biological fluids. We investigated a new method to isolate micro- and nano-scale species termed tangential flow for analyte capture (TFAC), which is an extension of traditional tangential flow filtration (TFF). Initially, EV purification from plasma on ultrathin nanomembranes was compared between both normal flow filtration (NFF) and TFF. NFF resulted in rapid formation of a protein cake which completely obscured any captured EVs and also prevented further transport across the membrane. On the other hand, TFF showed capture of CD63 positive EVs with minimal contamination. We explored the use of TFF to capture target species over membrane pores, wash and then release in a physical process that does not rely upon affinity or chemical interactions. This process of TFAC was studied with model particles on both ultrathin nanomembranes and conventional thickness membranes (polycarbonate track-etch). Successful capture and release of model particles was observed using both membranes. Ultrathin nanomembranes showed higher efficiency of capture and release with significantly lower pressures indicating that ultrathin nanomembranes are well-suited for TFAC of delicate nanoscale particles such as EVs.