Browsing by Author "Prokopovich, DA"

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    2nd generation microdosimeter with guard ring: an IBC study
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2009-11-25) Ziebell, AL; Hu, N; Lai, NS; Lim, WH; Reinhard, MI; Prokopovich, DA; Siegele, R; Dzurak, AS; Rosenfeld, AB
    Silicon-on-insulator (SOI) micro dosimeters have recently been used to successfully measure the radiobiological properties of mixed radiation fields typical of medical, space and radiation protection environments. These SOI devices consist of a 2D array of elongated parallelepiped diode structures. Charge collection studies have revealed that due to the electric field distribution within the planar SV, there are significant lateral charge diffusion effects which complicate charge collection and give rise to a less than ideal chord length variance. © 2009 AINSE
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    3D radiation detectors: charge collection characterisation and applicability of technology for microdosimetry
    (IEEE Xplore, 2014-08-04) Tran, LT; Prokopovich, DA; Petasecca, M; Lerch, MLF; Kok, A; Summanwar, A; Hansen, T; Via, CD; Reihnard, MI; Rosenfeld, AB
    A study of charge collection in SINTEF 3D active edge silicon detectors was carried out at ANSTO using Ion Beam Induced Charge (IBIC) technique. An IBIC study has shown that several different geometries of 3D detectors have full depletion under low applied bias. The effect of fast neutron and gamma radiation on their charge collection efficiency was also investigated. A 3D active edge silicon detector technology has demonstrated extremely promising performance for application of the 3D Sensitive Volumes (SVs) fabrication methods to SOI microdosimetry.© 2014, IEEE.
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    3D sensitive volume microdosimeter with improved tissue equivalency: charge collection study and its application in 12C ion therapy
    (IOP Publishing, 2018-02-06) James, B; Tran, LT; Bolst, D; Prokopovich, DA; Reinhard, MI; Lerch, MLF; Petasecca, M; Guatelli, S; Povoli, M; Kok, A; Matsufuji, N; Jackson, M; Rosenfeld, AB
    This research focuses on the characterisation of a new 3D sensitive volume (SV) microdosimeter covered with polyimide – a material which closely mimics human tissue. The electrical and charge collection properties of the device were investigated and its application in 12C ion therapy were studied. Charge collection studies revealed uniform charge collection and no cross talk between adjacent SVs. To study the microdosimetric response in 12C ion therapy, the new polyimide mushroom microdosimeter were placed at various positions along the central axis of a 290 MeV/u 12C ion spread out Bragg peak (SOBP) at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. From these microdosimetric spectra, dose mean lineal energy $(\overline{{y}_{D})}$ and RBE10 results were obtained, with RBE10 increasing from 1.3 at the entrance to 2.7 at the end of the SOBP. The results obtained in this work show that the new generation of mushroom microdosimeters, covered with tissue equivalent polyimide material, are a useful tool for quality assurance in heavy ion therapy applications. © Open Access - CC BY - IOP Publishing Ltd.
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    Application of an SOI microdosimeter for monitoring of neutrons in various mixed radiation field environments
    (Institute of Electrical and Electronics Engineers (IEEE), 2022-03-01) Pan, VA; Vohradsky, J; James, B; Pagani, F; Chartier, L; Debrot, E; Pastuovic, Z; Cutajar, D; Poder, J; Nancarrow, M; Pereloma, E; Bolst, D; Lee, SH; Inaniwa, T; Safavi-Naeini, M; Prokopovich, DA; Guatelli, S; Petasecca, M; Lerch, MLF; Povoli, M; Kok, A; Tran, LT; Rosenfeld, AB
    Radiation monitoring in space radiation is complex due to galactic cosmic rays (GCRs), solar particle events (SPEs), and albedo particles. Thermal neutrons are an important component in the Moon radiation albedo field which can cause single event upset (SEU) in electronics when they interact with the 10 B present in electronic components. In this work, we studied an application of silicon on insulator (SOI) microdosimeters for neutron monitoring in various mixed radiation field environments. A 10- μm SOI microdosimeter was utilized in conjunction with a 10 B 4 C thin-film converter to successfully measure the thermal neutron contribution out of field of a therapeutic proton beam as well as an 18-MV X-ray linear accelerator (LINAC). The microdosimeter was placed downstream of the Bragg peak (BP) as well as laterally out of field of the proton beam and at two positions along the treatment couch of the 18-MV LINAC. It was demonstrated that the 10- μm SOI microdosimeter with 10 B 4 C converter is suitable for detection of thermal neutrons with excellent discrimination of gamma, fast and thermal neutron components in the presence of a gamma-neutron pulsed field of an 18-MV LINAC. To reduce the gamma contribution and further improve detection of neutrons in mixed radiation fields, a new 2 μm Mushroom-planar microdosimeter was fabricated and characterized in detail using an ion beam induced charge collection (IBIC) technique with 1.78 MeV He2+ ions. It was demonstrated that this 2 μm SOI microdosimeter can be operated in a passive mode. The SOI microdosimeter with the 10 B 4 C converter can be recommended for the detection of thermal neutrons for SEU prediction in the mixed gamma-neutron fields during space missions, especially for the Moon mission.© Copyright 2025 IEEE
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    Carbon ion particle therapy - from accelerators to medical application
    (Australian Nuclear Science and Technology Organisation, 2017-10-06) Prokopovich, DA
    Particle therapy is gaining increasing usage internationally with particle therapy now being routinely used as a part of the radiotherapy protocols for cancer in several countries. Australia currently has several particle therapy proposals in development, including recent funding for a South Australian proton therapy and research facility. ANSTO and others are supporting the establishment of a National Particle Treatment and Research Centre. Unlike conventional Xray therapy, which uses accelerated electrons to generate X-rays, particle therapy uses a particle accelerator to fire ions directly in a highly precise beam into the patient to spare healthy tissue and ensure conformity of the dose delivery. Carbon ion therapy facilities use accelerated 12C ions because the carbon ions have a higher Relative Biological Effectiveness (RBE) when compared to X-rays or protons, as well as a better dose conformation to a tumour. An overview of different accelerator technologies and treatment delivery methods will be given as well as highlights of the latest developments for patient dose delivery technology.
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    Characterisation of a ΔE–E particle telescope using the ANSTO heavy ion microprobe
    (Elsevier, 2007-07) Siegele, R; Reinhard, MI; Prokopovich, DA; Ionescu, M; Cohen, DD; Rosenfeld, AB; Cornelius, IM; Wroe, A; Lerch, MLF; Fazzi, A; Pola, A; Agosteo, S
    Semiconductor planar processing technology has spurned the development of novel radiation detectors with applications in space, high energy physics, medical diagnostics, radiation protection and cancer therapy. The ANSTO heavy ion microprobe, which allows a wide range of ions to be focused into spot sizes of a few micrometers in diameter, has proven to be an essential tool for characterising these detectors using the Ion Beam Induced Charge (IBIC) imaging technique. The use of different ions and the wide range of available energies on the heavy ion microprobe, allows the testing of these devices with ionising particles associated with different values of linear energy transfer (LET). Quadruple coincidence measurements have been used to map the charge collection characteristics of a monolithic ΔE-E telescope, This was done through simultaneous measurement of the spatial coordinates of the microbeam relative to the sample and the response of both detector elements. The resulting charge collection maps were used to better understand the functionality of the device as well as to ascertain ways in which future device designs could be modified to improve performance. © 2007, Elsevier Ltd.
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    Characterization of prompt gamma rays for in-vivo range verification in hadron therapy: a geant4 simulation study
    (Institute of Physics Publishing, 2018-02-06) Zarifi, M; Guatelli, S; Qi, Y; Bolst, D; Prokopovich, DA; Rosenfeld, AB
    Prompt gamma (PG) rays have been proposed for in-vivo beam range verification during treatment delivery. As a secondary by-product emitted almost instantaneously upon ion-nuclear interaction, PG rays offer real-time tracking of the Bragg peak (BP). However their detection is challenging since they have a broad energy spectrum with interference from neutrons and stray gamma rays. Numerous approaches have been proposed to utilise PG for in-vivo beam range verification. In this work, Geant4 Monte Carlo (MC) simulations have been used to study the spectral, spatial, temporal and angular distribution characteristics of PG emission and detection from hadron radiation fields of varying energy. Proton, 12C and 4He beams irradiated homogeneous water phantoms. These studies will provide valuable information for the development of clinically suitable and reliable PG detector systems. © The Authors. Open Access.
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    Charge transport properties of CdMnTe radiation detectors
    (EDP Sciences, 2012-04-11) Rafiei, R; Boardman, DA; Reinhard, MI; Sarbutt, A; Kim, KH; Watt, GC; Uxa, S; Prokopovich, DA; Belas, E; Bolotnikov, AE; James, RB
    Growth, fabrication and characterization of indium-doped cadmium manganese telluride (CdMnTe) radiation detectors have been described. Alpha-particle spectroscopy measurements and time resolved current transient measurements have yielded an average charge collection efficiency approaching 100 %. Spatially resolved charge collection efficiency maps have been produced for a range of detector bias voltages. Inhomogeneities in the charge transport of the CdMnTe crystals have been associated with chains of tellurium inclusions within the detector bulk. Further, it has been shown that the role of tellurium inclusions in degrading charge collection is reduced with increasing values of bias voltage. The electron drift velocity was calculated from the rise time distribution of the preamplifier output pulses at each measured bias. From the dependence of drift velocity on applied electric field the electron mobility was found to be μn = (718 ± 55) cm2/Vs at room temperature. © 2012 the Authors, published by EDP Sciences.
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    Comparison of LaBr3 : Ce and LaCl3 : Ce with NaI(Tl) and cadmium zinc telluride (CZT) detectors
    (Institute of Electrical and Electronics Engineers (IEEE), 2008-06) Alexiev, D; Mo, L; Prokopovich, DA; Smith, ML; Matuchova, M
    Energy resolution and detection efficiency were compared between new scintillators, lanthanum bromide (LaBr3:Ce) and lanthanum chloride (LaCl3:Ce) with conventional detectors, sodium iodide NaI(Tl) and cadmium zinc telluride (CdZnTe or CZT). The study has shown that LaBr3:Ce and LaCl3:Ce scintillator detectors provided by Saint-Gobain offer better resolution than NaI(Tl) detector. LaBr3:Ce and LaCl3:Ce detectors could resolve some closely spaced peaks from 133Ba and 152Eu, which Na(I) could not. LaBr3:Ce has slightly better resolution and higher efficiency than LaCl3:Ce. An overall advantage of LaBr3:Ce and LaCl3:Ce detectors over NaI(Tl) and CZT has been discussed. The intrinsic activity of LaBr3:Ce is also demonstrated in this study. © 2008, Institute of Electrical and Electronics Engineers (IEEE)
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    Comparison of SOI microdosimeter and tissue equivalent proportional counter measurements at the CERF facility
    (Institute of Electrical and Electronics Engineers (IEEE), 2010-01-29) Prokopovich, DA; Reinhard, MI; Taylor, GC; Hands, A; Rosenfeld, AB
    The CERN-EU High Energy Reference Field (CERF) facility is used in the calibration of neutron dosimeters for aviation and high energy physics applications. A comparison of the facility's microdosimetric spectra obtained with a new Silicon on Insulator (SOI) Microdosimeter and a HAWK Tissue Equivalent Proportional Counter (TEPC) are presented. Experimental measurements with a silicon PIN dosimeter diode are also described which indicate a small but significant contribution from charged particles to dosimetry measurements within the neutron dominated field.
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    Cylindrical silicon-on-insulator microdosimeter: charge collection characteristics.
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2007-11-22) Ziebell, AL; Lim, WH; Reinhard, MI; Cornelius, IM; Prokopovich, DA; Siegele, R; Dzurak, AS; Rosenfeld, AB
    At present there exists a need, in both medical physics and radiation protection, for a portable microdosimeter that can be used in determining the radiobiological effectiveness (RBE) of different mixed radiation fields.
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    Cylindrical silicon-on-insulator microdosimeter: design, fabrication and TCAD modeling
    (Institute of Electrical and Electronics Engineers (IEEE), 2009-04) Lim, WH; Ziebell, AL; Cornelius, IM; Reinhard, MI; Prokopovich, DA; Dzurak, AS; Rosenfeld, AB
    A novel silicon-on-insulator (SOI) microdosimeter has been designed and fabricated using planar processing techniques to realise a device with a micron-scale well-defined sensitive volume. Cylindrical structures were employed to allow for an improved definition of the average chord length of the sensitive volume over that of previous elongated parallelepiped solid-state detector designs. The structures were manufactured on individual silicon mesas situated on top of a buried oxide insulating layer. The mesa design eliminated lateral charge diffusion. Two kinds of test structures were designed with sensitive region widths of 2 mum and 10 mum. In addition, an array of 900 cylindrical diodes was fabricated to increase the charge collection statistics. TCAD (Technology Computer Aided Design) modeling of the electrostatic potential and electric field profile of the cylindrical microdosimeter was carried out to obtain 3D potential and electric field profiles. The modeling revealed a radial electric field within the cylindrical-shaped sensitive volume with a 1/r dependence. While the electric field at the core of the cylindrical microdosimeter was not sufficiently high to induce avalanche signal multiplication, the higher electric field at the core should still assist in the measurement of low linear-energy transfer (LET) events. © 2009, Institute of Electrical and Electronics Engineers (IEEE)
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    Development of a large-area silicon α-particle detector
    (Elsevier, 2014-09) Tran, LT; Prokopovich, DA; Lerch, MLF; Petasecca, M; Siegele, R; Reinhard, MI; Perevertaylo, VL; Rosenfeld, AB
    Circular ion-implanted silicon detector of α-particles with a large, 5-cm2, sensitive area has been developed. An advantage of the detector is that the detector surface is easily cleanable with chemicals. The hardened surface of the detector shows no signs of deterioration of the spectroscopic and electrical characteristics upon repeated cleaning. The energy resolution along the diameters of the detector was (1.0±0.1)% for the 5.486-MeV α-particles. Detailed tests of the charge collection efficiency and uniformity of the detector entrance window were also performed with a 5.5-MeV He2+ microbeam. © 2014, Elsevier Ltd.
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    Evaluation of novel gamma ray imaging technology
    (Australasian Radiation Protection Society, 2017-08-09) Guenette, MC; Boardman, DA; Sarbutt, A; Flynn, A; Prokopovich, DA
    We present the imaging results from a novel single pixel gamma-ray imaging system, developed at ANSTO, which is capable of providing quantitative, spectroscopic gamma images using a fast and efficient imaging methodology. Gamma ray imaging can assist in surveying active areas by providing information of the radiation environment in areas which are hard to reach (e.g. in enclosed spaces or at height) and by gaining valuable information about the radiation environment whist limiting exposure to personnel in high dose rate environments. The system design provides a large field of view (360° × 70°) and covers a wide energy range of 40 keV to 1.5 MeV. The gamma ray image is overlaid on a 360° panoramic optical image of the scene, which allows for easy location of the gamma emitting radionuclides that are present. By selecting different regions of interest in the recorded gamma spectrum, separate radionuclide specific images, of the area being surveyed, can be visualised. Calibration of the detector allows for quantitative mapping of where each component of the dose rate at the detector originates. This can be converted into activity with a priori knowledge of the scene geometry. Gamma-ray images have been experimentally obtained for both point sources and extended sources in controlled testing environments and these results will be presented. The imaging results from a range of real world operational environments, around the ANSTO site, will be presented and demonstrate the systems capability for locating sources of radiation in nuclear industry applications.
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    Experimental investigation of the characteristics of radioactive beams for heavy ion therapy
    (Wiley, 2020-07) Chacon, A; James, B; Tran, LT; Guatelli, S; Chartier, L; Prokopovich, DA; Franklin, DR; Mohammadi, A; Nishikido, F; Iwao, Y; Akamatsu, G; Takyu, S; Tashima, H; Yamaya, T; Parodi, K; Rosenfeld, AB; Safavi-Naeini, M
    Purpose This work has two related objectives. The first is to estimate the relative biological effectiveness of two radioactive heavy ion beams based on experimental measurements, and compare these to the relative biological effectiveness of corresponding stable isotopes to determine whether they are therapeutically equivalent. The second aim is to quantitatively compare the quality of images acquired postirradiation using an in‐beam whole‐body positron emission tomography scanner for range verification quality assurance. Methods The energy deposited by monoenergetic beams of C at 350 MeV/u, O at 250 MeV/u, C at 350 MeV/u, and O at 430 MeV/u was measured using a cruciform transmission ionization chamber in a water phantom at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Dose‐mean lineal energy was measured at various depths along the path of each beam in a water phantom using a silicon‐on‐insulator mushroom microdosimeter. Using the modified microdosimetric kinetic model, the relative biological effectiveness at 10% survival fraction of the radioactive ion beams was evaluated and compared to that of the corresponding stable ions along the path of the beam. Finally, the postirradiation distributions of positron annihilations resulting from the decay of positron‐emitting nuclei were measured for each beam in a gelatin phantom using the in‐beam whole‐body positron emission tomography scanner at HIMAC. The depth of maximum positron‐annihilation density was compared with the depth of maximum dose deposition and the signal‐to‐background ratios were calculated and compared for images acquired over 5 and 20 min postirradiation of the phantom. Results In the entrance region, the was 1.2 ± 0.1 for both C and C beams, while for O and O it was 1.4 ± 0.1 and 1.3 ± 0.1, respectively. At the Bragg peak, the was 2.7 ± 0.4 for C and 2.9 ± 0.4 for C, while for O and O it was 2.7 ± 0.4 and 2.8 ± 0.4, respectively. In the tail region, could only be evaluated for carbon; the was 1.6 ± 0.2 and 1.5 ± 0.1 for C and C, respectively. Positron emission tomography images obtained from gelatin targets irradiated by radioactive ion beams exhibit markedly improved signal‐to‐background ratios compared to those obtained from targets irradiated by nonradioactive ion beams, with 5‐fold and 11‐fold increases in the ratios calculated for the O and C images compared with the values obtained for O and C, respectively. The difference between the depth of maximum dose and the depth of maximum positron annihilation density is 2.4 ± 0.8 mm for C, compared to −5.6 ± 0.8 mm for C and 0.9 ± 0.8 mm for O vs −6.6 ± 0.8 mm for O. Conclusions The values for C and O were found to be within the 95% confidence interval of the RBEs estimated for their corresponding stable isotopes across each of the regions in which it was evaluated. Furthermore, for a given dose, C and O beams produce much better quality images for range verification compared with C and O, in particular with regard to estimating the location of the Bragg peak. © 2024 American Association of Physicists in Medicine.
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    From imaging to dosimetry: GEANT4-based study on the application of medipix to neutron dosimetry
    (Elsevier, 2009-10-12) Othman, MAR; Marinaro, DG; Petasecca, M; Guatelli, S; Cutajar, DL; Lerch, MLF; Prokopovich, DA; Reinhard, MI; Uher, J; Jakubek, J; Pospisil, S; Rosenfeld, AB
    An application of Medipix2 using a newly developed segmented multiple thickness polyethylene (PE) converter for fast neutron detection is presented. The system has the ability to provide an energy independent response for the dose equivalent for fast neutrons. The application of weighting factors to each defined thickness of PE allows for a flattening of the response of the detector system for dosimetry applications. Six PE converter segments were applied, and their thicknesses and weighting factors were optimised to obtain the required energy independent detector response. The study performed by means of GEANT4. Its suitability for neutron dosimetry was studied with respect to a previously published work. © 2013 Elsevier B.V.
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    Geant4 simulation of the CERN-EU high-energy reference field (CERF) facility
    (Oxford University Press (OUP), 2010-09) Prokopovich, DA; Reinhard, MI; Cornelius, IM; Rosenfeld, AB
    The CERN-EU high-energy reference field facility is used for testing and calibrating both active and passive radiation dosemeters for radiation protection applications in space and aviation. Through a combination of a primary particle beam, target and a suitable designed shielding configuration, the facility is able to reproduce the neutron component of the high altitude radiation field relevant to the jet aviation industry. Simulations of the facility using the GEANT4 (GEometry ANd Tracking) toolkit provide an improved understanding of the neutron particle fluence as well as the particle fluence of other radiation components present. The secondary particle fluence as a function of the primary particle fluence incident on the target and the associated dose equivalent rates were determined at the 20 designated irradiation positions available at the facility. Comparisons of the simulated results with previously published simulations obtained using the FLUKA Monte Carlo code, as well as with experimental results of the neutron fluence obtained with a Bonner sphere spectrometer, are made. © 2010, Oxford University Press (OUP)
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    High-purity CdMnTe radiation detectors: a high-resolution spectroscopic evaluation
    (Intistute of Electrical Engineers, 2013-02-07) Rafiei, R; Reinhard, MI; Kim, KH; Prokopovich, DA; Boardman, DA; Sarbutt, A; Watt, GC; Bolotnikov, AE; Bignell, LJ; James, RB
    The charge transport properties of a high-purity CdMnTe (CMT) crystal have been measured at room temperature down to a micron-scale resolution. The CMT crystal, doped with indium, was grown by the vertical Bridgman technique. To reduce the residual impurities in the Mn source material, the growth process incorporated a five-times purification process of MnTe by a zone-refining method with molten Te solvent. The resulting 2.6 mm thick crystal exhibited an electron mobility-lifetime product of μnτn=2.9 × 10-3 cm2V-1. The velocity of electron drift was calculated from the rise time distribution of the preamplifier's output pulses at each measured bias. The electron mobility was extracted from the electric field dependence of the drift velocity and at room temperature it has a value of μn=(950±90) cm2/Vs. High-resolution maps of the charge collection efficiency have been measured using a scanning microbeam of 5.5 MeV 4He2+ ions focused to a beam diameter <; 1 μm and display large-area spatial uniformity. The evolution of charge collection uniformity across the detector has been highlighted by acquiring measurements at applied biases ranging between 50 V and 1100 V. Charge transport inhomogeneity has been associated with the presence of bulk defects. It has been demonstrated that minimizing the content of impurities in the MnTe source material is highly effective in achieving major improvements in the CMT detector's performance as compared to previous data. © 2013, IEEE.
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    IBIC microscopy – the powerful tool for testing micron – sized sensitive volumes in segmented radiation detectors used in synchrotron microbeam radiation and hadron therapies
    (Elsevier B. V., 2019-11-01) Pastuovic, Z; Davis, J; Tran, LT; Paino, JR; Dipuglia, A; James, B; Povoli, M; Kok, A; Perevertaylo, VL; Siegele, R; Prokopovich, DA; Lerch, MLF; Petasecca, M; Rosenfeld, AB; Cohen, DD
    Ion Beam Induced Charge (IBIC) microscopy performed using highly tuned microbeams of accelerated ions with energies in the MeV range is the powerful tool for analysis of charge carrier transport properties in semiconductor devices based on semiconductor hetero-junction, metal-on-semiconductor and semiconductor-on-insulator configurations. Here we present two cases of recent applications of the IBIC microscopy in the field of medical radiation physics. The reduced-rate ion microbeams with energies in the MeV range and sub-micrometer spot-sizes have been used for the investigations of the charge collection efficiency (CCE) in sensitive volumes of segmented radiation detectors in order to measure the spatial distribution and uniformity of CCE in different polarization conditions. This information allows the determination of the charge carrier transport properties in selected substructures of a particular device and to quantify its ability to accurately determine the energy deposited by incident ionizing radiation - two fundamental requirements of any microdosimeter or detector of ionizing radiation. © 2019 Elsevier B.V.
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    Investigation of Polarisation in CdTe using TCT
    (IOP Science, 2016-04-15) Prokopovich, DA; Ruat, M; Boardman, DA; Reinhard, MI
    The polarisation effect in CdTe:Cl has been studied using the Transient Current Technique (TCT) in order to quantitatively evaluate the subsequent changes in the charge transport properties as well as the electric field distribution in the sensor volume. The electric field is calculated from TCT pulses using the Schockley-Ramo theorem. The mobility of the charge carriers as well as their average drift velocity in the CdTe material are determined using the TCT pulse width. Infrared illumination demonstrated a temporary restoration of the electric field. However after a few minutes the polarization effect is resumed, even under constant IR illumination. © 2014, IOP Publishing Ltd and Sissa Medialab srl.