Characterization Of Radiation Fields Research Articles

Data Processing Engine (DPE): data analysis tool for particle tracking and mixed radiation field characterization with pixel detectors Timepix

Hybrid semiconductor pixelated detectors from the Timepix family are advanced detectors for online particle tracking, offering energy measurement and precise time stamping capabilities for particles of various types and energies. This inherent capability makes them highly suitable for various applications, including imaging, medical fields such as radiotherapy and particle therapy, space-based applications aboard satellites and the International Space Station, and industrial applications. The data generated by these detectors is complex, necessitating the development and deployment of various analytical techniques to extract essential information.For this purpose, and to aid the Timepix user community, it was designed and developed the“Data Processing Engine” (DPE) as an advanced tool for data processing designed explicitly for Timepix detectors. The functionality of the DPE is structured into three distinct processing levels: i) Pre-processing: this phase involves clusterization and the application of necessary calibrations and corrections. ii) Processing: this stage includes particle classification, employing machine learning algorithms, and the recognition of radiation fields. iii) Post-processing: involves various analyses, such as directional analysis, coincidence analysis, frame analysis, Compton directional analysis, and the generation of physics products, are performed. The core of the DPE is supported by an extensive experimental database containing calibrations and referential radiation fields of typical environments, including protons, ions, electrons, gamma rays and X rays, as well as thermal and fast neutrons. To enhance accessibility, the DPE is implemented into various user interface platforms such as a command-line tool, an application programming interface, and as a graphical user interface in the form of a web portal. The DPE's broad utility is exemplified through its integration into various applications and developments.

Advancing Methods for Fusion Neutronics: An Overview of Workflows and Nuclear Analysis Activities at UKAEA

Global research programs seeking to achieve a commercially viable model of a fusion power plant are being accelerated at an unprecedented rate. One critical element to the design and licensing is an accurate understanding of the radiation environment throughout the plant lifetime and subsequent decommissioning phase. The radiation field, which results from the nuclear fusion reaction, gives rise to highly complex phenomena such as flux leakage, materials activation, and decay gamma fields. Demonstration of compliance with limits, the integrity of components, and the permissibility of operations are all fundamental to regulatory approval and the overall safety of a nuclear device. As such, neutronics, which is used in the general sense to refer to the mapping of radiation fields in nuclear devices, is a critical design driver. The Applied Radiation Technology group at the United Kingdom Atomic Energy Authority is a world leader in this field, developing new methods and deploying state-of-the-art codes to conduct nuclear analysis. As well as applied neutronics in areas spanning fusion reactors, medical applications, spallation neutron sources, and nuclear fission, there is an extensive parallel experimental program undertaking critical radiation field characterization and conducting measurements using an array of bespoke particle detection systems. This paper highlights recent technical developments made by this group in the context of outstanding challenges in this field, as well as providing an overview of current methods and capabilities for the broader interest of the community.

Astroparticle Experiments to Improve the Biological Risk Assessment of Exposure to Ionizing Radiation in the Exploratory Space Missions: The research topic initiative

The actual and next decade will be characterized by an exponential increase in the Beyond Low Earth Orbit space exploration. In this context, a detailed space radiation field characterization will be crucial to optimize radioprotection strategies, assess the risk of the health hazard related to human space exploration, and reduce the damages potentially induced to astronauts from galactic cosmic radiation. Since the beginning of the century, many astroparticle experiments investigating the unknown universe components (e.g., dark matter, antimatter, dark energy) have collected enormous amounts of data regarding the cosmic ray (CR) components of the radiation in space. Such experiments are CR observatories, and the collected CR events contain valuable information that can enhance the space radiation field characterization. This paper will briefly present the status of the art of this research topic, and a research initiative titled “Astroparticle Experiments to Improve the Biological Risk Assessment of Exposure to Ionizing Radiation in the Exploratory Space Missions” will be introduced.

Experimental and Monte Carlo based study of different microdosimetric quantities at mixed radiation environments of nuclear reactor, reprocessing facility and D-D accelerator

Personnel working in the environment of nuclear reactors, fuel reprocessing facilities, high energy accelerators get exposed to a mixed radiation field of electrons, photons, and neutrons with a wide range of energy and fluence. Performance evaluations of the passive personnel dosimeters in these mixed radiation environments require knowledge of the external dose contributed by different types of radiations having variation in their energy, etc. Tissue Equivalent Proportional Counters (TEPC), sensitive to a wide range of particles and energy (Linear Energy Transfer (LET) ∼ 0–1500 keV μm−1), is one of the standard reference detectors which can be used for the characterization of mixed radiation fields. In the present work, HAWK TEPC was used to evaluate different microdosimetric parameters such as dose mean lineal energy (ӯD), average quality factor (Ǭ), the contribution of gamma and neutron dose equivalents for the characterizations of the radiation fields inside in a nuclear research reactor hall, fuel reprocessing facility, D-D neutron beam facility, radionuclide source based neutron calibration facilities, etc. Measured results were compared with Monte Carlo simulated values using radiation transport code PHITS. TEPC measurement shows that the radiation work field around nuclear reactor facility is dominated by gamma rays with approximate ӯD and Ǭ of ∼42 keV μm−1 and ∼2.3, respectively. Whereas ӯD and Ǭ values for neutron dominated locations in fuel reprocessing facility are 82 keV μm−1 and 8.2, respectively. Ǭ values near thermal neutron beam line in research reactor are close to 1 due to (n, γ) reaction. For 2.54 MeV mono-energetic D-D neutron beam, measured and calculated dose mean lineal energies (ӯD) are 52.5 keV μm−1 and 59.6 keV μm−1, respectively, whereas corresponding Ǭ values are 11.23 and 13.01. Obtained values can be utilized to correlate the neutron and gamma dose equivalents measured by passive detectors used for personnel monitoring program to enhance confidence in the dosimetry.

Radiation field characterization with emphasis on the collimator configuration at the compact neutron source RANS-II facility

ABSTRACT The RIKEN Accelerator-driven compact Neutron Source-II (RANS-II) based on the 7Li(p,n)7Be reaction with 2.49 MeV proton injection was installed in a small area of the experimental hall, where the scattered radiation is expected to strongly influence experiments. Therefore, we have begun to study the radiation characteristics of the RANS-II hall by simulation with the Particle and Heavy Ion Transport code System (PHITS) and by experiments to clearly identify the scattered component. In addition, to suppress the background, a collimator is studied with respect to its size, shape, and materials. With the use of the 30 mm borated polyethylene collimator, we found that the background becomes less than 1 of the extracted neutron beam intensity 1.0 m from the Li target. For the experiment, neutron suppression was characterized by measuring the neutron dose rate with a neutron dosimeter and a collimator. The suppression ability of the neutron beam was confirmed by comparing the results of simulations with those of experiments.

A Novel Hybrid Microdosimeter for Radiation Field Characterization Based on the Tissue Equivalent Proportional Counter Detector and Low Gain Avalanche Detectors Tracker: A Feasibility Study

In microdosimetry, lineal energies y are calculated from energy depositions ϵ inside the microdosimeter divided by the mean chord length, whose value is based on geometrical assumptions on both the detector and the radiation field. This work presents an innovative two-stages hybrid detector (HDM: hybrid detector for microdosimetry) composed by a tissue equivalent proportional counter and a silicon tracker made of 4 low gain avalanche diode. This design provides a direct measurement of energy deposition in tissue as well as particles tracking with a submillimeter lateral spatial resolution. The data collected by the detector allow to obtain the real track length traversed by each particle in the tissue equivalent proportional counter and thus estimates microdosimetry spectra without the mean chord length approximation. Using Geant4 toolkit, we investigated HDM performances in terms of detection and tracking efficiencies when placed in water and exposed to protons and carbon ions in the therapeutic energy range. The results indicate that the mean chord length approximation underestimate particles with short track, which often are characterized by a high energy deposition and thus can be biologically relevant. Tracking efficiency depends on the low gain avalanche diode configurations: 34 strips sensors have a higher detection efficiency but lower spatial resolution than 71 strips sensors. Further studies will be performed both with Geant4 and experimentally to optimize the detector design on the bases of the radiation field of interest.The main purpose of HDM is to improve the assessment of the radiation biological effectiveness via microdosimetric measurements, exploiting a new definition of the lineal energy (yT), defined as the energy deposition ϵ inside the microdosimeter divided by the real track length of the particle.

Particle tracking and radiation field characterization with Timepix3 in ATLAS

Four hybrid pixel detectors of Timepix3 technology, installed in the ATLAS experiment, were continuously taking data from April 2018 until the end of the Run-2 data taking period (December 2019). These detectors are synchronized with each other and the LHC orbit clock. They are capable of resolving the bunch structure of the LHC beams due to their time resolution of ∼2ns. Thus, they allow the characterization of the radiation field inside and outside bunch-crossing periods. This is shown for Timepix3 detectors at the extended barrel (x=-3.58 m, y=0.97 m, z=2.83 m). We apply pattern recognition methods to decompose the radiation field and determine the directionality of the minimum ionizing particles (MIP) component of the radiation field.

A remotely triggered fast neutron detection instrument based on a plastic organic scintillator.

A detector system for the characterization of radiation fields of both fast neutrons and γ rays is described comprising of a gated photomultiplier tube (PMT), an EJ299-33 solid organic scintillator detector, and an external trigger circuit. The objective of this development was to conceive a means by which the PMT in such a system can be actuated remotely during the high-intensity bursts of pulsed γ-ray contamination that can arise during active interrogation procedures. The system is used to detect neutrons and γ rays using established pulse-shape discrimination (PSD) techniques. The gating circuit enables the PMT to be switched off remotely. This is compatible with use during intense radiation transients to avoid saturation and the disruption of the operation of the PMT during the burst. Data are presented in the form of pulse-height spectra and PSD scatter plots for the system triggered with a strobed light source. These confirm that the gain of the system and the throughput for both triggered and un-triggered scenarios are as expected, given the duty cycle of the stimulating radiation. This demonstrates that the triggering function does not perturb the system response of the detector.

Fast three-dimensional radiation field characterization in large-scale nuclear installations

The requirement of the fast three-dimensional radiation field calculation is raised during the decommissioning of large-scale nuclear installations. The most often used methods, such as the Monte Carlo and the discrete ordinates methods, have shortcomings in their simulations of such problems. The coupled Monte Carlo–point kernel computational scheme is developed to meet the requirement. The facility is separated into the source region and the bulk shielding region, with a common interface. The transport within the source region is simulated using the Monte Carlo method, which is by nature good at treating complex geometries. The radiation field in the bulk shielding region is treated by the point kernel approach to avoid the extremely expensive computation for deep penetration problems. The flow rate through the interface, which is given by the Monte Carlo simulation, is considered as the equivalent surface source for the point kernel calculation. Test calculations from simplified typical waste storage facilities have been performed to validate the coupled scheme by comparing them with the results conducted by the Monte Carlo method directly. The good agreement of the results, as well as the significant saving in computing time, indicates that the coupled method is suitable for the fast three-dimensional radiation field calculation.

Characterization of Radiation Fields for Assessing Concrete Degradation in Biological Shields of NPPs

Life extensions of nuclear power plants (NPPs) to 60 years of operation and the possibility of subsequent license renewal to 80 years have renewed interest in long-term material degradation in NPPs. Large irreplaceable sections of most nuclear generating stations are constructed from concrete, including safety-related structures such as biological shields and containment buildings; therefore, concrete degradation is being considered with particular focus on radiation-induced effects. Based on the projected neutron fluence values (E > 0.1 MeV) in the concrete biological shields of the US pressurized water reactor fleet and the currently available data on radiation effects on concrete, some decrease in mechanical properties of concrete cannot be ruled out during extended operation beyond 60 years. An expansion of the irradiated concrete database is desirable to ensure reliable risk assessment for extended operation of nuclear power plants.

ATLAS-TPX: a two-layer pixel detector setup for neutron detection and radiation field characterization

A two-layer pixel detector setup (ATLAS-TPX), designed for thermal and fast neutron detection and radiation field characterization is presented. It consists of two segmented silicon detectors (256 × 256 pixels, pixel pitch 55 μm, thicknesses 300 μm and 500 μm) facing each other. To enhance the neutron detection efficiency a set of converter layers is inserted in between these detectors. The pixelation and the two-layer design allow a discrimination of neutrons against γs by pattern recognition and against charged particles by using the coincidence and anticoincidence information. The neutron conversion and detection efficiencies are measured in a thermal neutron field and fast neutron fields with energies up to 600 MeV. A Geant4 simulation model is presented, which is validated against the measured detector responses. The reliability of the coincidence and anticoincidence technique is demonstrated and possible applications of the detector setup are briefly outlined.

Characterization of Radiation Fields in Biological Shields of Nuclear Power Plants for Assessing Concrete Degradation*

Life extensions of nuclear power plants to 60 and potentially 80 years of operation have renewed interest in long-term material degradation. One material being considered is concrete, with a particular focus on radiation-induced effects. Based on the projected neutron fluence values (E > 0.1 MeV) in the concrete biological shields of the US pressurized water reactor fleet and the available data on radiation effects on concrete, some decrease in mechanical properties of concrete cannot be ruled out during extended operation beyond 60 years. An expansion of the irradiated concrete database and a reliable determination of relevant neutron fluence energy cutoff value are necessary to ensure reliable risk assessment for extended operation of nuclear power plants.

Image-Guided Radiotherapy Using a Modified Industrial Micro-CT for Preclinical Applications.

Purpose/ObjectiveAlthough radiotherapy is a key component of cancer treatment, its implementation into pre-clinical in vivo models with relatively small target volumes is frequently omitted either due to technical complexity or expected side effects hampering long-term observational studies. We here demonstrate how an affordable industrial micro-CT can be converted into a small animal IGRT device at very low costs. We also demonstrate the proof of principle for the case of partial brain irradiation of mice carrying orthotopic glioblastoma implants.Methods/MaterialsA commercially available micro-CT originally designed for non-destructive material analysis was used. It consists of a CNC manipulator, a transmission X-ray tube (10–160 kV) and a flat-panel detector, which was used together with custom-made steel collimators (1–5 mm aperture size). For radiation field characterization, an ionization chamber, water-equivalent slab phantoms and radiochromic films were used. A treatment planning tool was implemented using a C++ application. For proof of principle, NOD/SCID/γc−/− mice were orthotopically implanted with U87MG high-grade glioma cells and irradiated using the novel setup.ResultsThe overall symmetry of the radiation field at 150 kV was 1.04±0.02%. The flatness was 4.99±0.63% and the penumbra widths were between 0.14 mm and 0.51 mm. The full width at half maximum (FWHM) ranged from 1.97 to 9.99 mm depending on the collimator aperture size. The dose depth curve along the central axis followed a typical shape of keV photons. Dose rates measured were 10.7 mGy/s in 1 mm and 7.6 mGy/s in 5 mm depth (5 mm collimator aperture size). Treatment of mice with a single dose of 10 Gy was tolerated well and resulted in central tumor necrosis consistent with therapeutic efficacy.ConclusionA conventional industrial micro-CT can be easily modified to allow effective small animal IGRT even of critical target volumes such as the brain.

Microdosimetric characterisation of radiation fields for modelling tissue response in radiotherapy

Purpose: Our overall goal is the development of an approach to model tissue response to radiotherapy in which a tissue is viewed as a statistical ensemble of interacting cells. This involves characterisation of radiation fields on the spatial scale of subcellular structures. On this scale, the spatial distribution of radiation energy imparted to tissue is highly non-uniform and should be characterised in statistical terms. Microdosimetry provides a formalism developed for that purpose. This study addresses limitations of the standard microdosimetric approach to modelling tissue response by introducing two new characteristics that include additional information in a form convenient for this application. Methods : The standard microdosimetric approach is based on the concept of a sensitive volume (SV) representing a target volume in the cell. It is considered in isolation from other SVs, implying that energy depositions in different SVs are statistically independent and that individual cells respond to radiation independent of each other. In this study, we examined the latter approximation through analysis of correlation functions. All calculations were performed with Geant4-DNA Monte Carlo code. Results: We found that for some realistic scenarios, spatial correlations of deposited energy can be significant. Two new characteristics of radiation fields are proposed. The first is the specific energy-volume histogram (zVH), which is a microscopic analogue of the dose-volume histogram. The second describes the probability distribution of deposited energies in two SVs without assuming statistical independence between the SVs. Numerical examples for protons and carbon ions of therapeutic energies are presented and discussed. Conclusion: We extended the microdosimetric approach to modelling tissue response by including additional important characteristics and presented them in a more conventional radiotherapy format. --------------------------------------------- Cite this article as : Wang H, Vassiliev ON. Microdosimetric characterisation of radiation fields for modelling tissue response in radiotherapy. Int J Cancer Ther Oncol 2014; 2 (1):020116. DOI : http://dx.doi.org/10.14319/ijcto.0201.16

Design and operation of the H4IRRAD mixed-field test area at CERN

H4IRRAD is a new mixed-field irradiation area at CERN, designed for testing LHC electronic equipment, especially large volume assemblies such as full electronics racks of high current power converters. The area uses alternatively an attenuated primary 400 GeV/c proton beam slowly extracted from the CERN SPS, or a secondary, mainly proton, beam of 280 GeV/c directed towards a 1 m long, 7.5 cm diameter Cu target. Different shielding layers are used to reproduce a radiation field similar to the LHC “tunnel” and “shielded” areas in test zones around the target. The FLUKA Monte Carlo code was used for the design and optimization studies with the objective to match, as closely as possible, the mixed-radiation fields in the LHC ring, whilst also maintaining the lowest possible field gradient within the irradiation areas. Activation studies for the target, equipment, and the air volume were performed in order to assess safety risks, specify the access conditions and determine how to handle the equipment after irradiation. The test area has been in operation since 2011 with numerous tests performed already. The design concept of H4IRRAD, along with comparison studies between the FLUKA predictions and the measurements for the mixed radiation field characterization will be presented in this paper.

Characterisation of radiation field for irradiation of biological samples at nuclear reactor--comparison of twin detector and recombination methods

Central Laboratory for Radiological Protection is involved in achieving scientific project on biological dosimetry. The project includes irradiation of blood samples in radiation fields of nuclear reactor. A simple facility for irradiation of biological samples has been prepared at horizontal channel of the nuclear reactor MARIA in NCBJ in Poland. The radiation field, composed mainly of gamma radiation and thermal neutrons, has been characterised in terms of tissue kerma using twin-detector technique and recombination chambers.

Radiation field characterization and shielding studies for the ELI Beamlines facility

The ELI (Extreme Light Infrastructure) Beamlines facility in the Czech Republic, which is planned to complete the installation in 2015, is one of the four pillars of the ELI European project. Several laser beamlines with ultrahigh intensities and ultrashort pulses are foreseen, offering versatile radiation sources in an unprecedented energy range: laser-driven particle beams are expected to range between 1 and 50GeV for electrons and from 100MeV up to 3GeV for protons. The number of particles delivered per laser shot is estimated to be 109–1010 for the electron beams and 1010–1012 for the proton beams.The high energy and current values of the produced particles, together with the potentiality to operate at 10Hz laser repetition rate, require an accurate study of the primary and secondary radiation fields to optimize appropriate shielding solutions: this is a key issue to minimize prompt and residual doses in order to protect the personnel, reduce the radiation damage of electronic devices and avoid strong limitations in the operational time.A general shielding study for the 10PW (0.016Hz) and 2PW (10Hz) laser beamlines is presented here. Starting from analytical calculations, as well as from dedicated simulations, the main electron and proton fields produced in the laser-matter interaction have been described and used to characterize the “source terms” in full simulations with the Monte Carlo code FLUKA. The secondary radiation fields have been then analyzed to assess a proper shielding. The results of this study and the proposed solutions for the beam dumps of the high energy beamlines, together with a cross-check analysis performed with the Monte Carlo code GEANT4, are presented.

Characterization of radiation fields and dose assessment from fuels manufacturing for advanced fuel cycles

The purpose of this study was to examine radiological hazards introduced to workers from the fabrication of fuels with minor actinides (MA) and reprocessed uranium (RepU) and determine the feasibility of using shielded gloveboxes instead of remotely controlled operations in hot cells. Of particular concern is the increase in photon source term from the daughter products in RepU and the mixed neutron and photon fields introduced by MA recycle. In the interest of keeping the glovebox worker's radiation dose as low as reasonable achievable (ALARA), dose rates were calculated for various typical and bounding fuel compositions for light water reactors (LWR) and fast reactor (FR) mixed oxide (MOX) fuels with and without MA. The impact of varying the separation efficiency of americium (Am) and curium (Cm) was examined because current separation processes in reprocessing and recycling do not allow for the complete separation of Am from Cm. The additional Cm will cause a significant increase in the neutron source term. The sensitivity of the fuels to aging time was also examined by decaying the recycled feedstocks from 6 months to 3 years to simulate the effect of delays in reuse of recycled materials. The highest photon and neutron sources were used to calculate the additional shielding requirements that would be needed for fuel fabrication. Through insight gained from this study, it can be concluded that a standard glovebox with one quarter inch stainless steel walls can be used to fabricate fuels with Am with little to no additional shielding. The introduction of small amounts of Cm in the fuels will require the fuel fabrication to be preformed remotely in hot cells. Thus, stressing the importance of developing methods to increase the separation efficiency of Am from Cm.

Experimental Studies of Shielding and Irradiation Effects at High-Energy Accelerator Facilities

Experimental studies of shielding and radiation effects are carried out at Fermi National Accelerator Laboratory (FNAL) under collaboration between FNAL and Japan, aiming at benchmarking simulation codes and studying irradiation effects for the upgrade and design of new high-energy accelerator facilities. The purposes of this collaboration are (a) acquisition of shielding data in a proton beam energy region above 100 GeV, (b) further evaluation of predictive accuracy of the PHITS and MARS codes, (c) modification of physics models and data in these codes if needed, (d) characterization of radiation fields for studies of radiation effects, and (e) development of a code module for an improved description of radiation effects.The first campaign of the experiment was carried out at the Pbar target station and NuMI experimental station at FNAL, which use irradiation of targets with 120-GeV protons for antiproton and neutrino production, respectively. The generated secondary particles passing through steel, concrete, and rock were measured by activation methods as well as by other detectors such as a scintillator with a veto counter, phoswich detector, and a Bonner ball counter on trial. Preliminary experimental and calculated results are presented.

100 years of solid state dosimetry and radiation protection dosimetry

The use of solid state detectors in radiation dosimetry has passed its 100th anniversary. The major applications of these detectors in radiation dosimetry have been in personal dosimetry, retrospective dosimetry, dating, medical dosimetry, the characterization of radiation fields, and also in microdosimetry and radiobiology research. In this introductory paper for the 15th International Conference, I shall speak of the history of solid state dosimetry and of the radiation measurement quantities that developed at the same time, mention some landmark developments in detectors and applications, speak a bit more about dosimetry and measurement quantities, and briefly look at the past and future.