TUTCRIS - Tampereen teknillinen yliopisto

TUTCRIS

Alpha Radiation Detection via Radioluminescence of Air

Tutkimustuotos: Väitöskirja

Yksityiskohdat

AlkuperäiskieliEnglanti
KustantajaTampere University of Technology
Sivumäärä61
ISBN (elektroninen)978-952-15-3889-6
ISBN (painettu)978-952-15-3882-7
TilaJulkaistu - 21 joulukuuta 2016
OKM-julkaisutyyppiG5 Artikkeliväitöskirja

Julkaisusarja

NimiTampere University of Technology. Publication
Vuosikerta1449
ISSN (painettu)1459-2045

Tiivistelmä

Alpha radiation presents a challenge for operators in the field of nuclear safety and security. Due to the short range (few centimeters in air) and high stopping power, alpha particles are conventionally detected with dedicated instruments in close proximity of the source. However, the thermalization of an alpha particle in air causes an effect similar to northern lights. The scale of this radioluminescence emission is very weak, but the increase in range and number of signal carriers allows remote detection of alpha particles. This Thesis investigates the light yield of this effect and its applications to alpha radiation detection.

An experimental approach is taken to estimate the amount of radioluminescence photons per single alpha particle. Two different methods are employed for the measurement and the result of 19 ± 3 photons/MeV is discussed in the light of previous works. In addition, the emission spectrum is recorded in order to support the observations. This knowledge is essential for quantitative performance estimations of the method.

Contamination screening at distances greatly exceeding the typical range of alpha particles is studied by two-fold approach. First, three types of scientific-grade cameras are used to image radioluminescence light of alpha radiation sources at a nuclear research facility. The images are taken through translucent materials in darkness, and the feasibility implications of this fieldwork are described. Second, the translation into operative use is facilitated by development of a remote mapping system, optimized for use in an illuminated environment. The system is based on single pixel detector with a telescope that is panned across an area of interest. The process is automated in order to demonstrate its potential in nuclear decommissioning applications.

Whilst the radioluminescence method enables remote mapping of alpha sources, further analysis of the emitters requires gamma spectrometry. Here, the optical signals of alpha particles are used to trigger a gamma measurement of materials which decay via simultaneous emission of an alpha particle and a gamma ray. This allows focusing of gamma measurement without collimators and provides an effective means to reduce background level for the detection of minute amounts of material.

The coincidence method is also applied to direct detection of radon decay in air by observing simultaneous photon detection events. For the demonstration, high speed electronics are employed for list mode collection of radon events. The results are carefully analyzed to maximize the potential of large measurement volume and the temporal response of the method. The developed detection system is benchmarked and calibrated against a leading commercial radon detector.

Overall, the results confirm that radioluminescence light can be successfully utilized for in situ detection and characterization of alpha radiation sources. Moreover, the method allows unprecedented approaches that may establish their niche in the coming years.

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