Determination of alpha activity in organic solvents using CR-39

Differentiating multi-MeV, multi-ion spectra with CR-39 solid-state nuclear track detectors

The development of high intensity petawatt lasers has created new possibilities for ion acceleration and nuclear fusion using solid targets. In such laser-matter interaction, multiple ion species are accelerated with broad spectra up to hundreds of MeV. To measure ion yields and for species identification, CR-39 solid-state nuclear track detectors are frequently used. However, these detectors are limited in their applicability for multi-ion spectra differentiation as standard image recognition algorithms can lead to a misinterpretation of data, there is no unique relation between track diameter and particle energy, and there are overlapping pit diameter relationships for multiple particle species. In this report, we address these issues by first developing an algorithm to overcome user bias during image processing. Second, we use calibration of the detector response for protons, carbon and helium ions (alpha particles) from 0.1 to above 10 MeV and measurements of statistical energy loss fluctuations in a forward-fitting procedure utilizing multiple, differently filtered CR-39, altogether enabling high-sensitivity, multi-species particle spectroscopy. To validate this capability, we show that inferred CR-39 spectra match Thomson parabola ion spectrometer data from the same experiment. Filtered CR-39 spectrometers were used to detect, within a background of ~ 2 × 1011 sr-1 J-1 protons and carbons, (1.3 ± 0.7) × 108 sr-1 J-1 alpha particles from laser-driven proton-boron fusion reactions.

Measurements of alpha radioactivity in thermal power plant effluents employing CR-39 detector based improved alpha track detection method

Natural radioactivity is released into the environment during the combustion process of coal at various thermal power plants. Coal contains higher contents of α-emitting radionuclides such as ²³⁸U, ²³²Th along with their decay elements, which pose a potential health risk to the population. In the present studies, the effluent waste samples were collected from a coal fired Thermal Power Plant. Samples were collected in the form of solid residues and filtrates. CR-39 detector pieces were then exposed for varying time with residue and filtrate samples for registering the alpha tracks for α-detection and measurement. Thus, registered alpha particles in CR-39 detectors were revealed by employing the conventionally used 6M NaOH/KOH etchant and 5% tetraethyl ammonium bromide (TEAB) as a phase transfer catalyst in 6M NaOH/KOH etchant. Under both compositions of the etchants, CR-39 detectors were etched at 60 °C for 6 h for developing alpha tracks for observations under optical transmission microscope. Alpha track densities (T_d) and alpha track diameters in the etched CR-39 detectors for all samples were measured. The introduction of new chemical etchant effectively improved the uniformity in distribution of alpha tracks, enhanced the track density, and reduced the time of track revelation in CR-39 detectors. Therefore, it could be concluded that the phase transfer catalyst TEAB was highly effective in the etchant for alpha track revelation and detection as compared to conventionally used 6M NaOH etching method. Apart from measuring alpha radio activities, the amounts of ²³⁸U & ²³²Th in the samples were also measured by ICP-MS for understanding the alpha radio activities measured in the coal samples.

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.