DEPARTMENT OF RADIATION
PHYSICS AND DOSIMETRY - NZ63
Head of the Department: Prof. Paweł Bilski
English   Język polski

Newly discovered phenomenon of high-dose high-temperature lithium fluoride thermoluminescent emission: investigation of th mechanism and application to LHC measurements


Research project NCN SONATA ST2

delivery time in years: 2014-2017

Project manager: Barbara Obryk

The project aimed to investigate a mechanism leading to the newly discovered high-dose high-temperature lithium fluoride thermoluminescent emission and to verify the occurrence of this phenomenon in TL materials, as well as effective use of the method of measurement of ionizing radiation in the ultra-wide range based on this phenomenon at high energy accelerators, especially the LHC at CERN, and also nuclear facilities.

LiF:Mg,Cu,P thermoluminescent detectors enable measurements of radiation doses from tens of nanograys up to a few kilograys, at which dose the total saturation of the signal of the so-called main dosimetric peak (at about 220oC) occurs. Recently was observed high-temperature emission of LiF detectors heated to temperatures up to 600oC, after exposures to radiation doses ranging from 1 kGy to 1 MGy. In particular, the new peak was discovered in their glow-curve (denoted as peak B), occurring above 400oC, which properties are inconsistent with existing models of thermoluminescence.

Research conducted within the project have shown that in the occurrence of peak B in the LiF glow-curve a key role is played by dopants. The studies have been performed both in terms of type and concentration of dopants for detectors exposed to high doses of gamma, electron, proton and thermal neutron. Our studies have shown that in the presence of peak B in LiF glow-curves, dopants, in particular the correlation between magnesium, copper and phosphorus concentrations, are key to this effect. It was found that an important role in this phenomenon plays defects generated by radiation and their interaction with defects existing in the detector. A comprehensive study of properties of different TL detectors in terms of doping type and concentration of dopants have been conducted. The research methods involve study of thermoluminescent emission glow-curves, absorption spectra, emission spectra, photoluminescence, EPR spectra and other properties.

Worked out within the project experimental base and research methodology provided a proven research workshop of processes in TL materials. The studied phenomenon provided very promising applications for measurements of high and very high doses of radiation. Combining the standard thermoluminescence with the researched effect it was possible to measure with a single detector doses ranging from 1 μGy to 1 MGy, so covering an exceptional range of 12 orders of magnitudes. This approach has been already applied at CERN, around LHC and for its experiments and also for other high-energy accelerators and also nuclear facilities.

Understanding the mechanism of this phenomena on the one hand enable significant progress in the development of TL ultra-wide dose range dosimetry method, on the other contributes to a better understanding of the properties of defects in insulators, in particular their interaction with ionizing radiation.


Publications

Barbara Obryk, Helen J. Khoury, Vinicius S. de Barros, Pedro L. Guzzo, Paweł Bilski, On LiF:Mg,Cu,P and LiF:Mg,Ti phosphors high & ultra-high dosefeatures, Radiat. Meas. 71 (2014) 25-30; http://dx.doi.org/10.1016/j.radmeas.2014.02.002

K. Remy, S. Sholom, B. Obryk, S.W.S. McKeever, Optical absorption in LiF, LiF:Mg, LiF:Mg, Cu,P irradiated with high gamma and beta doses, Radiat. Meas. (2016); http://dx.doi.org/10.1016/j.radmeas.2016.11.007

Barbara Obryk, Mariusz Kłosowski, Patrycja Baran, Krzysztof Hodyr, Effect of dopants’ concentration on high-dose high-temperaturethermoluminescence of LiF:Mg,Cu,P detectors: Mg and Cu influence, Radiat. Meas. (2017); http://dx.doi.org/10.1016/j.radmeas.2017.03.003