M. Kłosowski

LITHIUM FLUORIDE CRYSTALS AS FLUORESCENT NUCLEAR TRACK DETECTORS

Radiophotoluminescence signal of LiF crystals was found to be sufficiently strong to visualize tracks of a single charged particle. This was achieved with a wide-field fluorescent microscope equipped with a ×100 objective and LiF single crystals grown with the Czochralski method at IFJ PAN. The tracks of alpha particles, protons, as well as products of 6Li(n,α)3H reaction with thermal neutrons (moderated Pu/Be source), were observed. These encouraging results are the first steps towards practical use of LiF as fluorescent nuclear track detectors. The most promising dosimetric application seems to be neutron measurements.

OVERVIEW OF NEUTRON MEASUREMENTS IN JET FUSION DEVICE

The design and operation of ITER experimental fusion reactor requires the development of neutron measurement techniques and numerical tools to derive the fusion power and the radiation field in the device and in the surrounding areas. Nuclear analyses provide essential input to the conceptual design, optimisation, engineering and safety case in ITER and power plant studies. The required radiation transport calculations are extremely challenging because of the large physical extent of the reactor plant, the complexity of the geometry, and the combination of deep penetration and streaming paths. This article reports the experimental activities which are carried-out at JET to validate the neutronics measurements methods and numerical tools used in ITER and power plant design. A new deuterium-tritium campaign is proposed in 2019 at JET: the unique 14 MeV neutron yields produced will be exploited as much as possible to validate measurement techniques, codes, procedures and data currently used in ITER design thus reducing the related uncertainties and the associated risks in the machine operation.

IMAGING OF PROTON BRAGG PEAKS IN LiF

Lithium fluoride (LiF) is one of the most common thermoluminescent phosphors routinely used in radiation protection services. Another advantageous property of LiF is radiophotoluminescence, whose occurs after its irradiation due to the creation of color centers. Excitation of LiF samples with a blue light causes the emission of photoluminescence, which spectrum consists of two peaks at ~520 and ~670 nm. The work was focused on imaging of Bragg peaks of proton beams routinely applied at the proton eye radiotherapy facility operating at the Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN) in Krakow by the measurement of the fluorescence light in LiF crystals excited with a 445 nm blue light after their previous irradiation with the proton beams of energies of 28, 30, 40 and 50 MeV. The range of proton beams in LiF crystals for different energies was calculated by Monte Carlo simulations.

Optical and thermal pre-readout treatments to reduce the influence of fading on LiMgPO4 OSL measurements

TL (Thermoluminescent) and OSL (Optically Stimulated Luminescence) techniques are both luminescent techniques widely applied in several areas into radiation dosimetry. The main difference between them are related to the employed stimulus (thermal or optical) for luminescent emission, as well as the advantages of each technique. Due to simplicity and not to be required heating, the OSL technique has been continuously improved and new researches in materials to be used with this technique have grown in the last decades. Nowadays the main problems in the application of the developed new materials are the poor stability and loss of OSL signal over time (fading). In this study, we performed a sequence of thermal (preheat) and optical (OSL with infra-red light stimulus) pre-readout treatments immediately before OSL readouts of LiMgPO4 based detectors (LMP), aiming the applicability of novel materials, contributing to find solutions to minimize the influence of fading. Moreover, it was demonstrated that the influence of fading is minimized and the stability of OSL signal from LMP is achieved using just optical process, without heating the material.

OSL properties of lithium aluminate crystals grown with Micro-Pulling-Down technique

Selected optically stimulated luminescence properties of lithium aluminate crystals are presented within this work. Crystals were grown using Micro-Pulling-Down technique. The growth parameters and XRD analysis of obtained samples are demonstrated. OSL decay curves, thermal stability and fading of samples prepared under different conditions are compared.

TL and OSL properties of LiMgPO 4 :Tb,B

LiMgPO4 (LMP) phosphor is a new highly sensitive material for TL and OSL dosimetry. The objective of the work was to investigate the dosimetric properties of this material. LMP phosphor doped with Tb and B was irradiated with beta rays and alpha particles. Thermoluminescence (TL) and optically stimulated luminescence (OSL) measurements were performed for LMP powders in comparison with Al2O3:C detector (Landauer). The phosphate which was made in our laboratory exhibits a main TL peak at 150°C. The synthesized LiMgPO4:Tb,B is a highly sensitive OSL material for dosimetric applications.