Radon track imaging in CR-39 plastic detectors using confocal scanning laser microscopy

Radon alpha track counting on solid state nuclear track detector by an ImageJ-based software macro

Radon (²²²Rn) is a radioactive gas emanating from geological materials. Inhalation of this gas is closely related to an increase in the probability of lung cancer if the levels are high. The usual methodology for the quantification of radon by passive methods is the use of etched solid-state nuclear track detectors, frequently in combination with optical microscopes or image scanning for image acquisition and software-based image processing for track counting. Currently available commercial instrumentation, as the Radosys microscopy system, is quite expensive, so the development of alternative methodologies is desirable. In this work, a simple, fast and low-cost image acquisition system for the determination of tracks in chemically etched CR-39 solid-state nuclear track detectors to quantify ²²²Rn alpha tracks has been proposed. The image of the detector surface is obtained by a conventional light stereoscopic microscope, transmitted by a CCD camera into the computer, and analyzed by the ImageJ open-source software. This methodology was employed to analyze 45 samples collected in dwellings and caves located in the region of Extremadura (Southwest Spain). Results show a good correlation coefficient of r² = 0.98 between the reference and purposed methodology and excellent repeatability, demonstrating that the system enables routine counting tracks for radon measurement as an alternative to the Radosys microscopy instrument.

STUDYING THE STRUCTURAL, OPTICAL, CHEMICAL AND ELECTROCHEMICAL ETCHING CHANGES OF CR-39 FOR DOSEMETRIC APPLICATIONS

The present work shows the induced modification of the structural, optical, chemical etching and electrochemical etching parameters of CR-39 irradiated with alpha-particles. CR-39 polymer track detectors were irradiated with different fluences (1.62 × 106, 2.72 × 106, 3.82 × 106 and 5.21 × 106 particles/cm2) of alpha-particles using 241Am source. The structural and optical properties were measured by FT-IR spectroscopy, X-ray diffraction and UV/Vis spectroscopy, respectively. The FT-IR spectra reveal that no major changes in the typical functional groups of irradiated polymer detectors. The X-ray diffraction patterns show that a broad band in the region of 12° < 2θ > 27°, which refers to the presence of the combination of amorphous and crystalline phases. UV/Vis responses of irradiated polymer track detectors exhibit a single absorption band in the range of 254-352 nm that is correlated to the occurrence of electronic transition. Also, the changes in the chemical and electrochemical parameters due to alpha-irradiation are examined and thoroughly discussed.

Application of confocal microscopy for surface and volume imaging of solid state nuclear track detectors

Inhalation of radon gas is considered a risk factor in the development of lung cancer. Solid state nuclear track detectors (SSNTDs) are often used for monitoring radon levels. We have previously shown that 3D imaging can help distinguish real tracks from artefact. In this study, we investigated particle tracks in nine SSNTDs using surface and volume visualisation from confocal microscope imaging. An Olympus LEXT OLS 4000 confocal microscope equipped with the Olympus LEXT Remote Development Kit was used to acquire z-stack images and surface data from the SSNTDs. Surface and volume visualisation analysis methods were developed and applied to examine the data. The mean (standard deviation) depth of 45 tracks from the nine detectors was 9.5 (4.6) μm. The mean difference in track depth using the two analysis techniques was 0.08 μm, thus showing good agreement. Furthermore, volume visualisation should enable assessment of the structure of tracks deep in the detector.