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There are three main methods used in individual monitoring: radiographic films, thermoluminescence (TL) and optically stimulated luminescence (OSL). Distinguishing between static (e.g. by leaving it accidentally or purposely in the radiation field) and dynamic exposures can be almost routinely performed for radiographic and OSL methods but is still unsolved for TL detectors. The main aim of this work is to develop a method for identifying static exposures of standard TL detectors at doses which are typical of radiation protection. For this purpose, a new TLD reader equipped with a CCD camera was developed to measure the two-dimensional signal map and not only the total light emitted (as is performed with standard photomultiplier-based TL readers). Standard MCP-N (LiF:Mg,Cu,P) TL pellets of 4.5 mm diameter and 0.9 mm thickness were installed in the standard Rados TL personal badges with special, non-uniform filters and exposed statically to 33 keV X-ray beams at three angles: 0 degrees, 30 degrees and 60 degrees. The detectors were readout in the CCD camera reader and 2-D images were collected. The analysis of these CCD images allows the identification of the static exposure cases and partly the angle of incidence at a dose level of 20 mSv.

Different approaches for the measurement of a relatively small gamma dose in strong fields of thermal and epithermal neutrons as used for Boron Neutron Capture Therapy (BNCT) have been studied with various thermoluminescence detectors (TLDs). CaF(2):Tm detectors are insensitive to thermal neutrons but not tissue-equivalent. A disadvantage of applying tissue-equivalent (7)LiF detectors is a strong neutron signal resulting from the unavoidable presence of (6)Li traces. To overcome this problem it is usual to apply pairs of LiF detectors with different (6)Li content. The experimental determination of the thermal neutron response ratio of such a pair at the Geesthacht Neutron Facility (GeNF) operated by PTB enables measurement of the photon dose. In the experimental mixed field of thermal neutrons and photons of the TRIGA reactor at Mainz the photon dose measured with different types of (7)LiF/(nat)LiF TLD pairs agree within a standard uncertainty of 6% whereas the CaF(2):Tm detectors exhibit a photon dose by more than a factor of 2 higher. It is proposed to determine suitable photon energy correction factors for CaF(2):Tm detectors with the help of the (7)LiF/(nat)LiF TLD pairs in the radiation field of interest.

The dosimetry around the X-ray tube with a needle-like anode (NAXT), developed at the Institute of Nuclear Studies, for interstitial brachytherapy has been performed using (1) dye films (Gafchromic XR-T), (2) large-area thermoluminescent (TL) detectors--prepared either by gluing TL powder onto thin Al foil (so-called planar detectors with spatial resolution of 0.1 mm) and (3) miniature (2 mm diameter and 0.5 mm thick) TL detectors. The measurements were performed in following geometries. (1) Needle inside a PMMA cylinder--the planar TL detector mounted on the surface of the cylinder. (2) Needle inside a thick block of PMMA and TL detector mounted vertically 7 mm from needle axis. TL detectors were read with the planar (2D) thermoluminescence reader, developed at IFJ, with a sensitive CCD (charge couple device) camera. Gafchromic films were evaluated with a system based on Agfa Arcus 1200 scanner and calibrated with X rays (35 kV) filtered with 0.03 mm Mo and with Co-60 photons. The intensity distribution of TL light on the planar detector was calibrated in terms of absorbed dose to water, using (137)Cs gamma-rays. TL planar detectors seem to be a promising tool for 2D dosimetry of miniature X-ray sources. Obtained results for TLDs and Gafchromic films seem to be comparable but differences have been found. Both methods are useful for measurements of dose distribution around the NAXT X-rays source.

In the dosimetry of boron neutron capture therapy (BNCT) beams, thermoluminescent (TL) detectors are typically applied in phantom measurements to determine the spatial distribution of the gamma ray and neutron dose. Pairs of 6LiF and 7LiF are applied to discriminate between the thermal neutron and gamma ray field components, exploiting the high cross section for (n,alpha) reaction of 6Li. At the Institute of Nuclear Physics (INP) in Kraków (Poland) a prototype TL-based measuring set has been constructed and tested. This set consists of a miniature TL detector (of 2 mm diameter and 0.4 mm thickness) placed inside a miniature container made of non-thermoluminescent 6LiF. The outer dimensions of the set are 4.5 mm diameter and 1.4 mm thickness, enabling its application in place of a thermoluminescence dosemeter pellet in typical phantoms. The detector sets were tested in the BNCT beam of the Studsvik reactor. By exploiting the ratio of TL signals of the unshielded and shielded detectors, it was possible to estimate the contributions of the thermal and epithermal components of the neutron field.

Lithium fluoride thermoluminescent (TL) detectors, with Li-7 isotope and various activators (MTS-7 LiF:Mg,Ti, MTT-7 LiF:Mg,Ti with enhanced Ti concentration and MCP-7 LiF:Mg,Cu,P) were used for dosimetry of heavy charged particles, within the ICHIBAN experiment. The microdosimetric model has been applied to calculate detection efficiency, η, relative to gamma-ray dose, of these detectors after proton and heavy charged particle (HCP) irradiation for ion charges ranging from Z = 1 to Z = 6 and in the energy range from 0.3 to 20 MeV amu - 1 . The calculated ratio η M C P - 7 /η M T S - 7 lies in the range between 0.2 and 1.0 for protons and between 0.2 and 0.4 for HCP with Z> 1. The calculated value of η M T T - 7 /η M T S - 7 for protons was found range between 1.0 and 1.45 and, for Z>1, between 1.3 and 2. These relationships can be applied to derive information about the 'effective LET' in an unknown HCP field and to correct the TLD readings for dose evaluation.

A method of measurement of radon concentration in air was developed, based on high-sensitivity LiF:Mg,Cu,P (MCP-N, TLD Poland) thermoluminescent detectors installed in charcoal canisters. The canisters were exposed typically for 72 h in a calibration chamber with a radon concentration ranging from 100 Bq x m(-3) to 87 kBq x m(-3). It was found that in these conditions the signal registered by the TL detectors was proportional to the 222Rn concentration and the lowest limit of detection (LLD) was at a level of 100 Bq x m(-3). The proposed method can be used in large-scale, multi-site surveys aimed at screening for high levels of indoor radon concentration or for measuring ground radon exhalation rates.

Dose measurements in brachytherapy 192Ir implants are often difficult due to large dose gradients and complex photon spectra. Therefore, tissue-equivalent detectors with a high spatial resolution, such as the highly promising LiF:Mg,Cu,P thermoluminescent detectors (TLDs) are required. It was the aim of the present work to ascertain if miniature LiF:Mg,Cu,P TLDs can effectively measure the dose distribution around 192Ir implants. 'Pin worm' TLDs (type MCP, diameter 0.6 mm, length 2 mm) were compared with GR-200R (SSDL, Beijing) rods cut in half. The TLDs were tested for reproducibility and energy dependence using high dose rate (HDR) and low dose rate (LDR) brachytherapy units. 192Ir measurements were performed in a tissue equivalent phantom accommodating hollow needles and catheters routinely used in brachytherapy. Pin worms had an average reproducibility of less than +/-2% (1 SD) and a detection limit of less than 10 microGy. The small dimensions of the pin worms allowed their placement within brachytherapy needles and catheters. The measured relative dose distribution was in good agreement with the predictions of a computerised treatment planning system (ADAC Pinnacle); however, limitations in the TLD energy correction did not allow for absolute dose comparison.

Short-term measurements of kerma rate from external radiation in the environment have been performed simultaneously at 100 locations over an area of about 15,000 km 2 using the Rapid Assessment of ACcidental Exposures (RACE) system which is based on LiF:Mg,Cu,P (MCP-N) ultra-sensitive thermoluminescent detectors. The short-term exposure lasted about 5 days, a total of about 128 h between pre-exposure annealing and readout, of which the exposure of the detector at the measurement site lasted about 96 h. To verify the short-term readouts, LiF:Mg,Cu,P (MCP-N) and conventional LiF:Mg,Ti (MTS-N) detectors were exposed at the same locations over a much longer period of 75 d. 100 field sites were selected over a large area in Southern Poland at distances of up to 150 km around Krakow. TL dosemeters, calibrated in terms of air kerma free-in-air using gamma rays from a 137 Cs source, were field-exposed 1 m above ground. The average kerma rates over 75 d measured using MTS-N (LiF:Mg,Ti) detectors ranged between 47 and 87 nGy.h -1 , using MCP-N between 60 and 107 nGy.h -1 while those measured over 4 days ranged between 56 and 100 nGy.h -1 . Comparison of ratios of short-term/long-term readouts of MCP-N at rural locations (35 points) gave a mean ratio of 0.99 ± 0.09 (1 SD). Thus, using the RACE system based on MCP-N detectors, one is able simultaneously to monitor environmental radiation kerma rates at a large number of locations over a very large area, over periods of two days, or less. Provided natural background kerma rates at selected monitoring points are available prior to the accident, the RACE system can be applied to assess kerma rates in the environment rapidly, following a nuclear accident. Noting that kerma rates would then be considerably higher, only a few hours of evaluation time would be required. The system could also be useful in reclamation and restoration works in the environment.

The time evolution of individual TL peak intensities in LiF:Mg,Cu:P has been studied for several storage temperatures ranging from -20°C to +50°C and for time periods from 10 min to 3 months. The experiments were carried out using commercially available LiF:Mg,Cu,P phosphors (GR-200 from China, MCP-N from Poland). The glow curves obtained were analysed using the FADA deconvolution program developed at CIEMAT. The influence of initial trap filling was studied by comparing two sets of detectors irradiated before and after the storage period. The results show no major differences between the two LiF:Mg,Cu,P varieties. The data show a good stability (1.00 ± 0.06) of the main dosimetric peak (peak 4) at all temperatures and over all time periods. In contrast, peak 2 and peak 3 show an exponential decrease, the rate of which strongly depends on storage temperature (peak 3 half-life changes from 300 h at room temperature to 20 h at +50°C).

Variation of Ti and Mg concentration is known to modify substantially the dosimetric characteristics of the standard LiF:Mg,Ti detector commonly used in radiotherapy. Preliminary studies conducted by the Institute of Nuclear Physics at Krakow suggested that the Ti concentration could be optimised with respect to low supralinearity and high TL efficiency in heavy particle beams. These results led to further investigation of new TL detectors appropriate to proton therapy. In particular, the influence of both Mg and Ti dopant concentrations on TL response in proton beams was studied.(LiF)-Li-7:Mg,Ti pellets (diameter 4.5 mm, thickness 0.5 mm) doped with 30 different combinations of Ti and Mg (five Ti concentrations: 4, 13, 39, 130, 260 ppm; six Mg concentrations: 30, 60, 120, 240, 480, 960 ppm) were irradiated in a 65 MeV proton beam at two different positions in a Perspex phantom corresponding to different depths in the Bragg curve. From the analysis of dose response and TL efficiency and its dependence on LET, recommendations on optimal dopant concentration are drawn for the clinical use of the dosemeter in proton therapy.

In a systematic investigation of the effect of dopant composition on dosimetric characteristics of thermoluminescent LiF:Mg,Cu,P phosphor, 130 samples were prepared with different concentrations of all activators over the following ranges: Mg (0-1.0 mol%), Cu (0-0.5 mol%) and P (0-5.0 mol%). From each material a group of sintered detectors was produced. Parameters describing the shape of the glow curve were analysed after standard annealing at 240°C and after annealing at temperatures up to 400°C. It appears that the amplitude of the main dosimetric peak 4 depends on the concentration of Cu and Mg, showing a distinct maximum for certain concentrations of these dopants. Intensities of high temperature peaks tend to rise with increasing Mg and decreasing Cu concentration. The dependence of the amplitude of peak 4 on P concentration is a step function, rising by an order of magnitude as the amount of P exceeds a threshold value of 0.15 mol%. It appears that copper does not participate in the formation of traps nor of luminescent centres and plays an indirect role, that of inhibiting the growth of high-temperature peaks. Increase of annealing temperatures up to 270°C results in a decrease of the signal from high temperature peaks and in an increase of the main peak intensity (for most combinations of dopant composition). At annealing temperatures above 270°C intensities of all peaks decrease. This thermal susceptibility of LiF:Mg,Cu,P appears to be associated with the instability of Mg-related defects.

Results are reported of tests of GR-200A (LiF:Mg,Cu,P Chinese production), MCP-N (LiF:Mg,Cu,P Polish production) and α-Al 2 O 3 highly sensitive TL detectors used in short-term measurements of natural radiation performed within the EU Intercalibration by the Polish (INP) and Spanish (CIEMAT) participants. The experiment was carried out in Roskilde, Denmark, by Riso National Laboratory. To assess only the cosmic component of natural radiation, detectors were exposed on a wooden pier. The actual dose rate was monitored over the total exposure time of three days by a Reuter-Stokes high pressure ionisation chamber. Results obtained with MCP-N and GR-200A were, for both teams, about 32 nGy.h -1 , for α-Al 2 O 3 :C about 49 nGy,h -1 , while the chamber-evaluated mean dose rate was about 40 nGy,h -1 . It was found that all tested detectors (MCP-N, GR-200A and α-Al 2 O 3 :C) are capable of measuring natural gamma dose rates alter an exposure of only a few hours.

The cosmic component of background gamma radiation, the intrinsic background (or 'self-dose') and fading of TLD-600, TLD-700 and TLD-200 (all produced by Harshaw), MCP-N (LiF:Mg,Cu,P produced by INP Krakow) and phosphate glass dosemeters SC-1 (Toshiba Glass) were measured over a period of 557 days at the Asse salt-mine 775 m below ground level, in a steel shielding at the FZK (Karlsruhe Research Centre) laboratory and in a buoy off-shore of an artificial lake. Assuming a reference cosmic dose rate of 37 nGy.h -1 over the lake, the relative response to cosmic rays was estimated at 0.76 for the LiF:Mg, Ti and CaF 2 :Dy detectors and 0.86 and 0.81 for the phosphate glass and LiF:Mg,Cu,P detectors, respectively. Fading of detectors of all types did not exceed 5% per annum, including long-term storage at 33°C in the salt mine.

The energy dependence of two types of LiF:Mg,Cu,P (GR-200A from China, MCP-N from Poland) and one type of α-Al 2 O 3 :C from Russia has been studied in the range 0.6-6.0 MeV. For completion, standard LiF:Mg,Ti (TLD-100 from USA) was also tested with the same methods. All the irradiations were carried out in Metrological Facilities in Spain (CIEMAT) and Germany (PTB). A build-up experiment was performed using different thicknesses of PMMA placed at the front and back of detectors. Corrections from photon attenuation, build-up factor and dose enhancement have been calculated and compared for further discussion. The results for the hypersensitive phosphors show an agreement within 5% when the 6-7 MeV photon response is compared with the standard 137 Cs calibration, while an under-response of 10% is observed for TLD-100.