Speaker
Description
Naturally occurring radionuclides such as potassium (K), uranium (U), and thorium (Th) are primary sources of ionizing radiation (α, β, and γ) contributing to the radiation dose received by quartz and feldspar mineral grains used in luminescence dosimetry/dating. The heterogeneous distribution of radionuclides within or adjacent to individual mineral grains can lead to significant variations in the absorbed dose, a phenomenon referred to as micro-dosimetry. Understanding and quantifying these micro-scale dose variations are crucial for accurate dose reconstruction at the level of single grains. Yet, this aspect remains poorly constrained due to a lack of suitable experimental techniques and the complexities involved in studying natural samples, which often contain a mixture of diverse components. While gamma-ray spectrometry is commonly used to quantify natural radionuclides, it provides only bulk-averaged values and offers no spatial mapping of the sources or origin within a sample [1, 2].
In this work, we present an integrated workflow to configure and apply the Timepix3 detector (silicon-based, 14 × 14 mm² active area, 256 × 256 pixels, 300 µm thickness [3]) for high-sensitivity imaging of α- and β-particles in low-radioactivity natural settings with the goal of enabling its use in micro-dosimetric investigations. The workflow includes particle track reconstruction, charged particle identification, background suppression, energy calibration using calibration standards, including x-rays, and pixel-level filtering. Due to the low interaction probability of γ-rays in 300 µm-thick silicon, high-energy photons (>100 keV) are largely undetectable using such a detector thickness; thus, our focus is restricted to α and β detection. The developed methodology enables spatially resolved imaging of charged particle emissions from natural sample surfaces (e.g., rock), allowing the investigation of dose variations at the scale of individual mineral grains. Our results demonstrate the capability of Timepix3 to support micro-dosimetric investigations and particle-specific mapping in weak radioactive natural materials.
References
- Nathan, R.P., Thomas, P.J., Jain, M., Murray, A.S. and Rhodes, E.J. 2003. Environmental dose rate heterogeneity of beta radiation and its implications for luminescence dating: Monte Carlo modelling and experimental validation. Radiation Measurements, 37: 305-313.
- Fu, X., Romanyukha, A.A., Li, B., Jankowski, N.R., Lachlan, T.J., Jacobs, Z., George, S.P., Rosenfeld, A.B. and Roberts, R.G., 2022. Beta dose heterogeneity in sediment samples measured using a Timepix pixelated detector and its implications for optical dating of individual mineral grains. Quaternary Geochronology, 68: 101254.
- Poikela, T., Plosila, J., Westerlund, T., Campbell, M., De Gaspari, M., Llopart, X., ... & Kruth, A. (2014). Timepix3: a 65K channel hybrid pixel readout chip with simultaneous ToA/ToT and sparse readout. Journal of instrumentation, 9(05), C05013.
| Workshop topics | Detector systems |
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