Since about two decades, a renewed interest on aerogels has risen. These peculiar materials show fairly unique properties. Thus, they are under investigation for both scientific and commercial ...purposes and new optimized production processes are studied. In this work, the possibility of using aerogel in the field of radiation detection is explored. The idea is to substitute the gas filling in a ionization chamber with the aerogel. The material possesses a density about 100 times greater than ambient pressure air. Where as the open-pore structure should allow the charge carriers to move freely. Small hydrophobic silica aerogel samples were studied. A custom ionization chamber, capable of working both with aerogel or in the classic gas set up, was built. The response of the chamber in current mode was investigated using an X-ray tube. The results obtained showed, under proper conditions, an enhancement of about 60 times of the current signal in the aerogel configuration with respect to the classic gas one. Moreover, some unusual behaviours were observed, i.e. time inertia of the signal and super-/sub-linear current response with respect to the dose rate. While testing high electric fields, aerogel configuration seemed to enhance the Townsend’s effects. In order to represent the observed trends, a trapping–detrapping model is proposed, which is capable to predict semi-empirically the steady state currents measured. The time evolution of the signal is semi-quantitatively represented by the same model. The coefficients estimated by the fits are in agreement with similar trapping problems in the literature. In particular, a direct comparison between the benchmark of the FET silica gates and aerogel case endorses the idea that the same type of phenomenon occurs in the studied case.
•Neutron/γ–ray discrimination via optical light filtration instead of PSD methods.•Study of the CVL in CLYC: an ultra-fast mechanism emitting in the deep-near UV.•Correlation between the time and the ...wavelength domain of the scintillation light.•Correlation between the RL spectra with the TCSPC technique and a fast PMT results.•LET dependence of the quenching effect on the CVL emission in CLYC.
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7Li enriched Cs2LiYCl6:Ce3+ (CLYC) is a promising inorganic scintillator for real-time γ-ray and fast neutron spectrometry. The neutron/γ-ray discrimination is usually accomplished exploiting the different quenching effects of high Linear Energy Transfer (LET) particles on different scintillation mechanisms, usually by means of the time analysis of the pulse shape. In principle, the emission wavelength information could be used to address the same task. However, a systematic study of the correlations between the CLYC decay time, its radio-luminescence spectrum and the LET of the impinging particle has not yet been performed. We therefore investigated the CLYC scintillation process under neutron and γ-ray irradiation, correlating the time response to the scintillation wavelength spectrum using a 1–inch right cylinder>99% 7Li enriched CLYC. We found that the relative intensity of the Core to Valence Luminescence (CVL) is almost constant with photons in the energy range 20–660 keV, i.e. 0.5–5 keV/μm LET, and is only partially quenched by neutrons. Instead, the direct electron-hole capture scintillation mechanism is completely cut under neutron irradiation. The luminescence in between the deep-Ultraviolet and the Near Ultraviolet region (250–350 nm) might be attributed to both the CVL and the host luminescence, also in thick highly Ce3+-doped crystals.
The new operational dosimetric quantities framework, proposed in the ICRU95 report, has stimulated the scientific community to start investigations that aim to assess its impact on radiation ...protection practices. As part of this effort, the present study describes an inter-comparison exercise among individual monitoring services (IMSs) on passive whole-body dosimetry. The inter-comparison is performed in terms of both the existing operational dose quantityHp(10)and its proposed replacementHp, to allow an evaluation of the actions that may be necessary to adapt dosimetry systems to the proposed quantity. For two of the tested IMSs, simple modifications to the detector response function, or the dose calculation algorithm, were sufficient to obtain results within acceptable limits. However, these approaches are not sufficient to give a level of performance comparable to that achieved in terms ofHp(10). This may require a modification to dosemeter design.
In the framework of the EURADOS working group 11, an intercomparison of active neutron survey meters was performed in a pulsed neutron field (PNF). The aim of the exercise was to evaluate the ...performances of various neutron instruments, including commercially available rem-counters, personal dosemeters and instrument prototypes. The measurements took place at the cyclotron of the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH. The cyclotron is routinely used for proton therapy of ocular tumours, but an experimental area is also available. For the therapy the machine accelerates protons to 68MeV. The interaction of the proton beam with a thick tungsten target produces a neutron field with energy up to about 60MeV. One interesting feature of the cyclotron is that the beam can be delivered in bursts, with the possibility to modify in a simple and flexible way the burst length and the ion current. Through this possibility one can obtain radiation bursts of variable duration and intensity. All instruments were placed in a reference position and irradiated with neutrons delivered in bursts of different intensity. The analysis of the instrument response as a function of the burst charge (the total electric charge of the protons in the burst shot onto the tungsten target) permitted to assess for each device the dose underestimation due to the time structure of the radiation field. The personal neutron dosemeters were exposed on a standard PMMA slab phantom and the response linearity was evaluated.
Since the first particle accelerator’s construction in 1931, an exponential spread of these machines occurred worldwide, in different kinds of applications. Nowadays, these are mainly used for ...industrial (60%) and medical (35%) purposes and for scientific research (5%). High energy secondary mixed fields produced by the particle beams interaction with matter imply a complex environmental dosimetry and special radiation protection regulations able to guarantee workers and population safety. In the medical field, this aspect is particularly emphasized in hadrontherapy centres, where high energy charged particles such as protons and carbon ions modify environmental doses, with a significant increase in the neutron contribution. This work proposes a technique to identify points of losses of the primary particle beam around an acceleration ring and has been developed within the radiation protection section at the National Centre for Oncological Hadrontherapy situated in Pavia. In the first part, the radiation field produced by protons and carbon ions interactions with structural materials at different energies was investigated. The main instrument of analysis is the Monte Carlo code for particle transport FLUKA, supported by experimental measurements in the treatment room carried out with the rem counter LUPIN, designed for pulsed neutron fields dosimetry. This first step allowed an analysis of both the angular and energetic instrumental response and a comparison of experimental results with simulations. The second part proposes a description of the technique for beam loss positions reconstruction around the acceleration ring at CNAO based on the application of unfolding codes.
A new method for improving REM counter performance in Pulsed Neutron Fields (PNFs) has been developed. This method uses an analysis of the build-up of space charge in the counter to compensate for an ...underestimation of Ambient Dose Equivalent (H*(10)) in intense pulsed fields. It was applied to three sets of experimental data acquired using the LUPIN-II REM counter device, which is designed for use in PNFs. The data was acquired using the cyclotron at Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), at the HiRadMat facility at CERN and at the ‘Elettra Sincrotrone Trieste’ (ELETTRA), Italy. A comparison of the data with and without this compensation method is used to highlight its effectiveness. The LUPIN-II performance, which has already been shown to be able to cope with fields of up to hundreds of nSv/burst, is improved by at least one order of magnitude, with further potential for improvement.
Since 2012, the European Radiation Dosimetry Group (EURADOS) has developed its Strategic Research Agenda (SRA), which contributes to the identification of future research needs in radiation dosimetry ...in Europe. Continued scientific developments in this field necessitate regular updates and, consequently, this paper summarises the latest revision of the SRA, with input regarding the state of the art and vision for the future contributed by EURADOS Working Groups and through a stakeholder workshop. Five visions define key issues in dosimetry research that are considered important over at least the next decade. They include scientific objectives and developments in (i) updated fundamental dose concepts and quantities, (ii) improved radiation risk estimates deduced from epidemiological cohorts, (iii) efficient dose assessment for radiological emergencies, (iv) integrated personalised dosimetry in medical applications and (v) improved radiation protection of workers and the public. This SRA will be used as a guideline for future activities of EURADOS Working Groups but can also be used as guidance for research in radiation dosimetry by the wider community. It will also be used as input for a general European research roadmap for radiation protection, following similar previous contributions to the European Joint Programme for the Integration of Radiation Protection Research, under the Horizon 2020 programme (CONCERT). The full version of the SRA is available as a EURADOS report (www.eurados.org).
SSNTDs (solid-state nuclear track detectors), primarily made from PADC (poly(allyl diglycol carbonate)), are attractive detectors for dosimetric purposes. SSNTDs are more similar to human tissue than ...other passive detectors and the measurement of the track parameters provides information about the energy deposition of the incident particle. This paper describes a method for LET measurement based on the measurements of the major and minor axes of the track opening. The method was experimentally tested using alpha particles with energies ranging from 4.2MeV to 6MeV. The experimental results show that PADC can measure the total energy lost by a particle along a path of length Δx divided by the length itself, a quantity strictly related to the LET.
The European Radiation Dosimetry Group (EURADOS) is a network of organizations and scientists promoting research and development in the dosimetry of ionizing radiation, contributing to harmonization ...in dosimetry practice across Europe, and offering education and training in areas relevant for dosimetry. As a registered non-profit association under German law, EURADOS is currently running eight active working groups (WGs): WG2 on “Harmonization of Individual Monitoring”, WG3 on “Environmental Dosimetry”, WG6 on “Computational Dosimetry”, WG7 on “Internal Dosimetry”, WG9 on “Dosimetry in Radiotherapy”, WG10 on “Retrospective Dosimetry”, WG11 on “Dosimetry in High-Energy Radiation Fields”, and WG12 on “Dosimetry in Medical Imaging”. This paper presents recent scientific results obtained within these working groups, and additionally highlights the role of EURADOS as an organization which contributes to the development of a systematic strategy of radiation protection research in Europe.
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