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Data, Emanuele Maria; Vohradsky, James; James, Benjamin; Pan, Vladimir; Bolst, David & Donetti, Marco
[Show all 18 contributors for this article]
(2025).
Comparison of LEM and MKM based RBE-weighted doses from microdosimetric measurements with silicon 3D microdosimeter.
Physica Medica.
ISSN 1120-1797.
136.
doi:
10.1016/j.ejmp.2025.105042.
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Introduction:
In carbon ion radiation therapy, the Local Effect Model (LEM) predicts higher value of Relative Biological Effectiveness (RBE) with respect to the Microdosimetric Kinetic Model (MKM) in most clinical situations. This work aims at comparing the MKM-based RBE-weighted dose calculated from experimental microdosimetric quantities against the RBE-weighted dose computed by a Treatment Planning System (TPS) using the LEM version I.
Methods:
The Silicon-On-Insulator (SOI) 3D mushroom microdosimeter, developed by the Centre for Medical Radiation Physics (CMRP), Wollongong (Australia), was placed in an RW3 phantom and was irradiated with carbon ions with different plans at the Centro Nazionale di Adroterapia Oncologica (CNAO), Pavia (Italy), acquiring microdosimetric spectra along the beam direction and calculating the corresponding
with the MKM model applied for Human Salivary Gland (HSG) cells.
Results:
A good agreement between experiment and Monte Carlo simulation was found, obtaining RBE10 values ranging between 1.2 and 2.8. The prescribed LEM I-based RBE-weighted dose of 3.0 GyE in a cubic SOBP showed to be 33 % larger than the MKM-based RBE-weighted dose, consistently with other results found in literature.
Conclusion:
This work confirms the reliable use of the 3D SOI microdosimeters as a quality assurance tool for RBE prediction in particle therapy. In addition, the presented outcomes represents a validation through experimental measurements of previous works found in literature on the MKM and LEM RBE-weighted dose comparison based on TPS calculations and Monte Carlo simulations.
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Waets, Andreas; Emriskova, Natalia; Alia, Ruben Garcia; Klimek, Karolina; Pan, Vladimir & Rosenfeld, Anatoly
[Show all 12 contributors for this article]
(2025).
Microdosimetry of very-high-energy heavy ion beams for electronics testing using silicon-on-insulator detectors.
IEEE Transactions on Nuclear Science.
ISSN 0018-9499.
72(8),
p. 2513–2518.
doi:
10.1109/TNS.2025.3550471.
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This article explores the use of microdosimetry with a silicon-on-insulator (SOI) detector for characterizing very-high-energy (VHE) heavy ion beams used specifically for single event effect (SEE) testing of electronics. The detector was deployed at CERN’s heavy ion facility for radiation effects testing and exposed to lead ion beams in the 100–1000 MeV per nucleon kinetic energy range. The implications and possible benefits of using microdosimetry for SEE testing purposes are discussed.
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Segal, Julie; Kenney, Christopher; Koybasi, Ozhan; Kok, Angela & Povoli, Marco
(2024).
Design, fabrication, and preliminary test results of a new inverse-LGAD for soft X-ray detection.
Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment.
ISSN 0168-9002.
1065.
doi:
10.1016/j.nima.2024.169467.
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Povoli, Marco; Kok, Angela Chun Ying; Koybasi, Ozhan; Getz, Michael Norderhaug; O'Neill, George & Röhrich, Dieter
[Show all 15 contributors for this article]
(2023).
3D silicon detectors for neutron imaging applications.
Journal of Instrumentation (JINST).
18,
p. 1–12.
doi:
10.1088/1748-0221/18/01/C01056.
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Neutron detection is of great importance in many fields spanning from scientific research, to nuclear science, and to medical application. The development of silicon-based neutron detectors with enhanced neutron detection efficiency can offer several advantages such as spatial resolution, enhanced dynamic range and background discrimination. In this work, increased detection efficiency is pursued by fabricating high aspect ratio 3D micro-structures filled with neutron converting materials (B4C) on planar silicon detectors. An in-depth feasibility study was carried out in all aspects of the sensor fabrication technology. Passivation of the etched structures was studied in detail, to ensure good electrical performance. The conformal deposition of B4C with a newly developed process showed excellent results. Preliminary electrical characterisation of the completed devices is promising, and detectors have been mounted on dedicated boards in view of the upcoming tests with neutrons.
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Getz, Michael Norderhaug; Povoli, Marco; Koybasi, Ozhan; Slavicek, Tomas & Monakhov, Eduard
(2023).
Gamma-radiation hardness and long-term stability of ALD-Al2O3 surface passivated Si.
Journal of Applied Physics.
ISSN 0021-8979.
133(15).
doi:
10.1063/5.0143013.
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Al2O3 has emerged as the surface passivation material of choice for p-type silicon in photovoltaics and has also become a candidate for passivating Si-based radiation sensors. However, the surface passivation of Al2O3 has been shown to degrade when exposed to gamma-radiation, making it of interest to determine methods of depositing Al2O3 that minimize the radiation-induced degradation on the surface passivation. In this study, we investigate the long-term stability and gamma-radiation hardness of Al2O3 prepared using the TMA+H2O+O3 precursor combination and how the pretreatment, the deposition temperature, and the film thickness affect the density of interface states, Dit, and fixed oxide charge, Qfix, before and after gamma-irradiation. We find that the surface saturation current density, J0s, of silicon passivated by Al2O3 increases after annealing but stabilizes over time depending on the Al2O3 thickness. Samples with thicknesses of <20 nm stabilize within hours, while those with >60 nm stabilize over days. J0s stabilizes at lower values with increased Al2O3 thickness. After exposure to 1 Mrad gamma-radiation, the samples still exhibit low Dit and high Qfix, with the best performing sample having a Dit of 1.5 × 1010 eV−1 cm−2 and a Qfix of −3.1 × 1012 cm−2. The deposition temperature appears to indirectly affect radiation hardness, owing to its impact on the hydrogen concentration in the film and at the Si–SiOx–Al2O3 interface. Lifetime measurements after irradiation indicate that Al2O3 still passivates the surface effectively. The carrier lifetime and Qfix can largely be recovered by annealing samples in O2 at 435 °C.
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Getz, Michael Norderhaug; Povoli, Marco & Monakhov, Eduard
(2022).
Improving ALD-Al2O3 Surface Passivation of Si Utilizing Pre-Existing SiOx.
IEEE Journal of Photovoltaics.
ISSN 2156-3381.
12(4),
p. 929–936.
doi:
10.1109/JPHOTOV.2022.3169985.
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Al 2 O 3 has rapidly become the surface passivation material of choice for p + layers of solar cells because of its high negative fixed charge, good long-term and thermal stability, and no parasitic absorption. In this article, the surface saturation current density, fixed charge, and interface state density are compared for Al 2 O 3 deposited on Si substrates where the pre-existing out-of-the-box SiO x layer was not removed, with substrates where the SiO x was removed by hydrofluoric acid. The depositions are performed by atomic layer deposition at temperatures in the 150–300 °C range, using trimethylaluminium, H 2 O, and O 3 as precursors. The samples where the native oxide was not removed achieve a higher level of surface passivation for every tested deposition temperature, with the sample deposited at 200 °C exhibiting a surface saturation current density of only 0.9 fA/cm 2 after annealing, a fixed charge of −4.2 × 10 12 cm −2 , and a density of interface states of 9.8 × 10 9 cm −2 eV −1 . Capacitance and conductance voltage characteristics reveal a strong correlation between the surface saturation current density and the density of interface states and fixed charges. It is also determined that the long-term stability of the surface passivation depends on the deposition temperature, with higher deposition temperatures resulting in improved long-term stability. The results indicate that H-terminated Si prior to Al 2 O 3 deposition may have a detrimental effect on the surface passivation.
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Lee, Sung Hyun; Mizushima, Kota; Yonai, Shunsuke; Matsumoto, Shinnosuke; Mizuno, Hideyuki & Nakaji, Taku
[Show all 16 contributors for this article]
(2022).
Predicting the Biological Effects of Human Salivary Gland Tumour Cells for Scanned 4He-, 12C-, 16O-, and 20Ne-Ion Beams Using an SOI Microdosimeter.
Applied Sciences.
12(12).
doi:
10.3390/app12126148.
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Experimental microdosimetry along with the microdosimetric kinetic (MK) model can be utilized to predict the biological effects of ions. To predict the relative biological effectiveness (RBE) of ions and the survival fraction (SF) of human salivary gland tumour (HSGc-C5) cells, microdosimetric quantities measured by a silicon-on-insulator (SOI) MicroPlus-mushroom microdosimeter along the spread-out Bragg peak (SOBP) delivered by pencil beam scanning of 4He, 12C, 16O, and 20Ne ions were used. The MK model parameters of HSGc-C5 cells were obtained from the best fit of the calculated SF for the different linear energy transfer (LET) of these ions and the formerly reported in vitro SF for the same LET and ions used for calculations. For a cube-shaped target of 10 × 10 × 6 cm3, treatment plans for 4He, 12C, 16O, and 20Ne ions were produced with proprietary treatment planning software (TPS) aiming for 10% SF of HSGc-C5 cells over the target volume and were delivered to a polymethyl methacrylate (PMMA) phantom. Afterwards, the saturation-corrected dose-mean lineal energy derived based on the measured microdosimetry spectra, along with the physical dose at various depths in PMMA phantoms, was used for the estimation of the SF, RBE, and RBE-weighted dose using the MK model. The predicted SF, RBE, and the RBE-weighted dose agreed with what was planned by the TPS within 3% at most depths for these ions.
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Heggelund, Andreas; Huiberts, Simon Kristian; Dorholt, Ole; Read, Alexander Lincoln; Røhne, Ole Myren & Sandaker, Heidi
[Show all 14 contributors for this article]
(2022).
Radiation hard 3D silicon pixel sensors for use in the ATLAS detector at the HL-LHC.
Journal of Instrumentation (JINST).
17(8).
doi:
10.1088/1748-0221/17/08/P08003.
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The High Luminosity LHC (HL-LHC) upgrade requires the planned Inner Tracker (ITk) of the ATLAS detector to tolerate extremely high radiation doses. Specifically, the innermost parts of the pixel system will have to withstand radiation fluences above 1 × 1016 neqcm-2. Novel 3D silicon pixel sensors offer a superior radiation tolerance compared to conventional planar pixel sensors, and are thus excellent candidates for the innermost parts of the ITk. This paper presents studies of 3D pixel sensors with pixel size 50 × 50 μm2 mounted on the RD53A prototype readout chip. Following a description of the design and fabrication steps, Test Beam results are presented for unirradiated as well as heavily irradiated sensors. For particles passing at perpendicular incidence, it is shown that average efficiencies above 96% are reached for sensors exposed to fluences of 1 × 1016 neqcm-2 when biased to 80 V.
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Betta, Gian-Franco Dalla & Povoli, Marco
(2022).
Progress in 3D Silicon Radiation Detectors.
Frontiers in Physics.
10.
doi:
10.3389/fphy.2022.927690.
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In the past few years, there has been an increasing interest toward 3D silicon radiation detectors. Owing to their unique architecture, 3D detectors provide a remarkable radiation hardness at relatively low bias voltage (hence low power dissipation), that makes them the most appealing solution for use in the innermost layers of tracking detectors in High Energy Physics (HEP) experiments. Besides this primary application, the use of 3D sensor technology has been extended also to other fields, like thermal neutron detection and microdosimetry for proton and ion therapy. In this paper, we will review the state of the art and on going efforts in 3D detectors, covering the main design and technological issues, as well as selected results from the experimental characterization and TCAD simulation.
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Koybasi, Ozhan; Nordseth, Ørnulf; Tran, Trinh; Povoli, Marco; Rajteri, Mauro & Pepe, Carlo
[Show all 14 contributors for this article]
(2021).
High Performance Predictable Quantum Efficient Detector Based on Induced-Junction Photodiodes Passivated with SiO2/SiNx.
Sensors.
21(23).
doi:
10.3390/s21237807.
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We performed a systematic study involving simulation and experimental techniques to develop induced-junction silicon photodetectors passivated with thermally grown SiO2 and plasma-enhanced chemical vapor deposited (PECVD) SiNx thin films that show a record high quantum efficiency. We investigated PECVD SiNx passivation and optimized the film deposition conditions to minimize the recombination losses at the silicon–dielectric interface as well as optical losses. Depositions with varied process parameters were carried out on test samples, followed by measurements of minority carrier lifetime, fixed charge density, and optical absorbance and reflectance. Subsequently, the surface recombination velocity, which is the limiting factor for internal quantum deficiency (IQD), was obtained for different film depositions via 2D simulations where the measured effective lifetime, fixed charge density, and substrate parameters were used as input. The quantum deficiency of induced-junction photodiodes that would be fabricated with a surface passivation of given characteristics was then estimated using improved 3D simulation models. A batch of induced-junction photodiodes was fabricated based on the passivation optimizations performed on test samples and predictions of simulations. Photodiodes passivated with PECVD SiNx film as well as with a stack of thermally grown SiO2 and PECVD SiNx films were fabricated. The photodiodes were assembled as light-trap detector with 7-reflections and their efficiency was tested with respect to a reference Predictable Quantum Efficient Detector (PQED) of known external quantum deficiency. The preliminary measurement results show that PQEDs based on our improved photodiodes passivated with stack of SiO2/SiNx have negligible quantum deficiencies with IQDs down to 1 ppm within 30 ppm measurement uncertainty.
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Terzo, Stefano; Boscardin, Maurizio; Carlotto, Juan; Betta, Gian-Franco Dalla; Darbo, Giovanni & Dorholt, Ole
[Show all 29 contributors for this article]
(2021).
Novel 3D Pixel Sensors for the Upgrade of the ATLAS Inner Tracker.
Frontiers in Physics.
9.
doi:
10.3389/fphy.2021.624668.
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The ATLAS experiment will undergo a full replacement of its inner detector to face the challenges posed by the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The new Inner Tracker (ITk) will have to deal with extreme particle fluences. Due to its superior radiation hardness the 3D silicon sensor technology has been chosen to instrument the innermost pixel layer of ITk, which is the most exposed to radiation damage. Three foundries (CNM, FBK, and SINTEF), have developed and fabricated novel 3D pixel sensors to meet the specifications of the new ITk pixel detector. These are produced in a single-side technology on either Silicon On Insulator (SOI) or Silicon on Silicon (Si-on-Si) bonded wafers by etching both n- and p-type columns from the same side. With respect to previous generations of 3D sensors they feature thinner active substrates and smaller pixel cells of 50 × 50 and 25 × 100 µm2. This paper reviews the main design and technological issues of these novel 3D sensors, and presents their characterization before and after exposure to large radiation doses close to the one expected for the innermost layer of ITk. The performance of pixel modules, where the sensors are interconnected to the recently developed RD53A chip prototype for HL-LHC, has been investigated in the laboratory and at beam tests. The results of these measurements demonstrate the excellent radiation hardness of this new generation of 3D pixel sensors that enabled the project to proceed with the pre-production for the ITk tracker.
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Valdimir, Pan; Vohradsky, James; James, Benjamin; Pagani, F; Chartier, Lachlan & Debrot, Emily
[Show all 23 contributors for this article]
(2021).
Application of an SOI Microdosimeter for Monitoring of Neutrons in Various Mixed Radiation Field Environments.
IEEE Transactions on Nuclear Science.
ISSN 0018-9499.
69(3),
p. 491–500.
doi:
10.1109/TNS.2021.3125999.
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Radiation monitoring in space radiation is complex due to Galactic Cosmic Rays (GCR), Solar Particle Events (SPE) 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 10B 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 10B4C 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 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 10B4C 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 characterised 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 10B4C converter can be recommended for detection of thermal neutrons for SEU prediction in mixed gamma-neutron field during space missions especially for the Moon mission.
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Tran, Linh T.; David, Bolst; James, Benjamin; Pan, Vladimir M.; Vohradsky, James & Peracchi, Stefania
[Show all 19 contributors for this article]
(2021).
Silicon 3D Microdosimeters for Advanced Quality Assurance in Particle Therapy.
Applied Sciences.
12(1).
doi:
10.3390/app12010328.
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The Centre for Medical Radiation Physics introduced the concept of Silicon On Insulator (SOI) microdosimeters with 3-Dimensional (3D) cylindrical sensitive volumes (SVs) mimicking the dimensions of cells in an array. Several designs of high-definition 3D SVs fabricated using 3D MEMS technology were implemented. 3D SVs were fabricated in different sizes and configurations with diameters between 18 and 30 µm, thicknesses of 2–50 µm and at a pitch of 50 µm in matrices with volumes of 20 × 20 and 50 × 50. SVs were segmented into sub-arrays to reduce capacitance and avoid pile up in high-dose rate pencil beam scanning applications. Detailed TCAD simulations and charge collection studies in individual SVs have been performed. The microdosimetry probe (MicroPlus) is composed of the silicon microdosimeter and low-noise front–end readout electronics housed in a PMMA waterproof sheath that allows measurements of lineal energies as low as 0.4 keV/µm in water or PMMA. Microdosimetric quantities measured with SOI microdosimeters and the MicroPlus probe were used to evaluate the relative biological effectiveness (RBE) of heavy ions and protons delivered by pencil-beam scanning and passive scattering systems in different particle therapy centres. The 3D detectors and MicroPlus probe developed for microdosimetry have the potential to provide confidence in the delivery of RBE optimized particle therapy when introduced into routine clinical practice.
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James, Benjamin; Tran, Linh T.; Bolst, David; Prokopovich, Dale A.; Lerch, Michael L.F. & Petasecca, Marco
[Show all 13 contributors for this article]
(2021).
In-field and out-of-field microdosimetric characterisation of a 62 MeV proton beam at CATANA.
Medical Physics.
ISSN 0094-2405.
48(8),
p. 4532–4541.
doi:
10.1002/mp.14905.
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Purpose
A 5 and 10 μm thin silicon on insulator (SOI) 3D mushroom microdosimeter was used to characterize both the in-field and out-of-field of a 62 MeV proton beam.
Methods
The SOI mushroom microdosimeter consisted of an array of cylindrical sensitive volumes (SVs), developed by the Centre for Medical Radiation Physics, University of Wollongong, was irradiated with 62 MeV protons at the CATANA (Centro di AdroTerapia Applicazioni Nucleari Avanzate) facility in Catania, Italy, a facility dedicated to the radiation treatment of ocular melanomas. Dose mean lineal energy, (urn:x-wiley:00942405:media:mp14905:mp14905-math-0001), values were obtained at various depths in PMMA along a pristine and spread out Bragg peak (SOBP). The measured microdosimetric spectra at each position were then used as inputs into the modified Microdosimetric Kinetic Model (MKM) to derive the RBE for absorbed dose in a middle of the SOBP 2Gy (RBED). Microdosimetric spectra were obtained with both the 5 and 10 μm 3D SOI microdosimeters, with a focus on the distal part of the BP. The in-field and out-of-field measurement configurations along the Bragg curve were modeled in Geant4 for comparison with experimental results. Lateral out-of-field measurements were performed to study secondary particles’ contribution to normal tissue’s dose, up to 12 mm from the edge of the beam field, and quality factor and dose equivalent results were obtained.
Results
Comparison between experimental and simulation results showed good agreement between one another for both the pristine and SOBP beams in terms of urn:x-wiley:00942405:media:mp14905:mp14905-math-0002 and RBED. Though a small discrepancy between experiment and simulation was seen at the entrance of the Bragg curve, where experimental results were slightly lower than Geant4. The dose equivalent value measured 12 mm from the edge of the target volume was 1.27 ± 0.15 mSv/Gy with a urn:x-wiley:00942405:media:mp14905:mp14905-math-0003 value of 2.52 ± 0.30, both of which agree within uncertainty with Geant4 simulation.
Conclusions
These results demonstrate that SOI microdosimeters are an effective tool to predict RBED in-field as well as dose equivalent monitoring out-of-field to provide insight to probability of second cancer generation.
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Getz, Michael; Povoli, Marco & Monakhov, Eduard
(2021).
Effect of the native oxide on the Surface Passivation of Si by Al2O3.
Journal of Applied Physics.
ISSN 0021-8979.
129(20).
doi:
10.1063/5.0051215.
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The effect of the native silicon oxide layer on the passivation properties of Al2O3 on p-type Si surfaces has been investigated. This was done by comparing effective carrier lifetime, surface saturation current density, fixed charge, and density of interface states of samples, where the native oxide was not removed prior to Al2O3 passivation, with samples subjected to a 3 min HF-dip. The sample with the native oxide exhibits excellent surface passivation post-annealing, with a surface saturation current density of 13 fA/cm2 and significantly longer effective lifetime compared to the sample, where the native oxide was removed. Capacitance–voltage measurements of a sample with the native oxide revealed a remarkably low density of interface states (1010 eV−1 cm−2), almost three times lower than a sample where the native oxide was removed prior to Al2O3 deposition. The results indicate that a thin layer of native oxide improves the Al2O3 surface passivation of silicon.
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Mendicino, Roberto; Kok, Angela; Koybasi, Ozhan; Povoli, Marco; Summanwar, Anand & Betta, Gian-Franco Dalla
(2020).
Characterization of SINTEF 3D diodes with trenched-electrode geometry before and after neutron irradiation.
Journal of Instrumentation (JINST).
15(2),
p. 1–9.
doi:
10.1088/1748-0221/15/02/C02023.
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We report on the characterization of 3D diodes with trenched electrodes and active edges manufactured by SINTEF MiNaLab (Oslo, Norway), and irradiated with reactor neutrons up to a maximum fluence of 2 × 1016 neq cm−2. The charge collection performance of these test structures is investigated by using a position resolved pulsed laser system, and discussed with the aid of TCAD simulations. In spite of the non-idealities of the test setup, whose spatial resolution is not fine enough for the small-pitch geometries of the considered samples, results confirm the good radiation hardness of 3D sensors with trenched electrodes.
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Mehendale, Shruti Vineet; Kanaki, Kalliopi; Povoli, Marco; Samnøy, Andreas Tefre; Tambave, Ganesh Jagannath & Kok, Angela
[Show all 17 contributors for this article]
(2020).
Characterization of boron-coated silicon sensors for thermal neutron detection.
Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment.
ISSN 0168-9002.
972.
doi:
10.1016/j.nima.2020.164124.
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Silicon neutron detectors can operate at low voltage and come with ease of fabrication and the possibility of integration of readout electronics and thus are attractive from an application point of view. In this paper, we have studied thermal neutron capture by silicon diodes coated with boron carbide (B4C). One of the surfaces of the diodes was covered with either natural B4C (B4C) or with enriched B4C (B4C). We have investigated: (a) the effect of increase in the sensitive area of the surface of the diode covered with B4C on the neutron detection efficiency and (b) the effect of enrichment of 10B in B4C. The difference in 10B in B4C (16 at. in the deposited film) and B4C ( 79 at. in the deposited film) leads to about three times increase in detection efficiency of the same detector. For the given experimental conditions, we do not observe a direct relationship between increase in the surface area and the detection efficiency. Energy spectra obtained by Geant4 simulations support the experimental observation of finding no direct relation between increase in the surface area and the detection efficiency.
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Peracchi, Stefania; James, P; Federico, Pagani; Pan, Alexey; Vohradsky, J. & Bolst, David
[Show all 19 contributors for this article]
(2020).
Radiation shielding evaluation of spacecraft walls against heavy ions using microdosimetry.
IEEE Transactions on Nuclear Science.
ISSN 0018-9499.
68(5),
p. 897–905.
doi:
10.1109/TNS.2020.3032946.
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Despite the low contribution of heavy ions to the total fluence in the space radiation environment, their radiobiological effect on the human body is extremely high. In this article, we investigated the radiation field which resulted from the interaction of galactic cosmic rays (GCRs), specifically some heavy ions and energies, typically encountered in space with a realistic multilayer sample of the International Space Station (ISS) Columbus module's shielding wall. The quality factor, Q, and the normalized dose equivalent, H, derived from microdosimetric measurements for C, Ne, and Si ions behind different spacecraft wall configurations and materials are presented in this article. Particularly, carbon fiber, polyoxymethylene, and perspex with same areal density compared to currently used aluminum were investigated.
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Samnøy, Andreas Tefre; Ytre-Hauge, Kristian; Malinen, Eirik; Tran, Linh; Rosenfeld, Anatoly & Povoli, Marco
[Show all 9 contributors for this article]
(2020).
Microdosimetry with a 3D silicon on insulator (SOI) detector in a low energy proton beamline.
Radiation Physics and Chemistry.
ISSN 0969-806X.
176(109078).
doi:
10.1016/j.radphyschem.2020.109078.
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An accurate description of the radiation quality of proton beams is a precondition to increase our understanding of radiobiological mechanisms and to develop accurate biological response models for radiotherapy. However, there are few detectors capable of measuring microdosimetric quantities with high spatial resolution along the entire Bragg curve due to the rapid increase in stopping power at the Bragg peak (BP) and distal dose fall-off (DDF). The aim of this work was to measure the microdosimetric spectra along the Bragg curve in a low energy proton beamline used for radiobiological experiments with a novel 3D silicon-on-insulator (SOI) “mushroom” microdosimeter.
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Kok, Angela; Povoli, Marco; Summanwar, Anand; Tran, Linh T.; Petasecca, Marco & Lerch, Michael
[Show all 9 contributors for this article]
(2020).
Fabrication and First Characterization of Silicon-Based Full 3-D Microdosimeters.
IEEE Transactions on Nuclear Science.
ISSN 0018-9499.
67(12),
p. 2490–2500.
doi:
10.1109/TNS.2020.3035077.
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Microdosimetry provides measurements of stochastic lineal energy deposition in a micrometric sensitive volume (SV) that are comparable to human cell dimensions, typically in the order of 10-15 μm in diameter. Silicon-based microdosimeters have been fabricated using “3-D technology,” providing true celllike SVs that are fully encapsulated by a 3-D through substrate electrode. The unique geometry has been made feasible using modern microelectromechanical systems (MEMS). The combination of MEMS techniques and radiation detector fabrication brings forth challenges in achieving reliability, consistency, and high yield. This article reviews the technological challenges encountered in several prototype runs completed at SINTEF. The technological review and prototype iterations aim to deliver a future technology plan at the manufacture level with a high yield throughput.
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James, B.; Tran, Linh T.; Vohradsky, J.; Bolst, David; Pan, Vladimir M. & Carr, M
[Show all 19 contributors for this article]
(2019).
SOI Thin Microdosimeter Detectors for Low Energy Ions and Radiation Damage Studies.
IEEE Transactions on Nuclear Science.
ISSN 0018-9499.
66(1),
p. 320–326.
doi:
10.1109/TNS.2018.2885996.
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The responses of two silicon on insulator (SOI) 3-D microdosimeters developed by the Centre for Medical Radiation Physics were investigated with a range of different low energy ions, with high linear energy transfer (LET). The two microdosimeters n-SOI and p-SOI were able to measure the LET of different ions including 7 Li, 12 C, 16 O, and 48 Ti with ranges below 350 μm in silicon. No plasma effects were seen in the SOI microdosimeters when irradiated with the high LET ions. A Monte Carlo simulation using Geant4 was compared to the experimental measurements, whereby some discrepancies were observed for heavier ions at lower energies. This discrepancy can be partly attributed to uncertainties in the thickness of the energy degraders and overlayers of the devices. The microdosimetric measurements of low energy 16 O ions were obtained and compared to a therapeutic 16 O ion beam. The radiation hardness of the two devices was studied using the ion beam induced charge collection technique. Both types of the microdosimeters when biased had no essential changes in charge collection efficiency in the sensitive volume after irradiation with low energy ions.
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Wagenaar, David; Tran, Linh T.; Meijers, Arturs; Marmitt, Gabriel Guterres; Souris, Kevin & Bolst, David
[Show all 13 contributors for this article]
(2019).
Validation of linear energy transfer computed in a Monte Carlo dose engine of a commercial treatment planning system.
Physics in Medicine and Biology.
ISSN 0031-9155.
65(2).
doi:
10.1088/1361-6560/ab5e97.
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The relative biological effectiveness (RBE) of protons is highly variable and difficult to
quantify. However, RBE is related to the local ionization density, which can be related to the
physical measurable dose weighted linear energy transfer (LETD). The aim of this study was
to validate the LETD calculations for proton therapy beams implemented in a commercially
available treatment planning system (TPS) using microdosimetry measurements and
independent LETD calculations (Open-MCsquare (MCS)).
The TPS (RayStation v6R) was used to generate treatment plans on the CIRS-731-HN
anthropomorphic phantom for three anatomical sites (brain, nasopharynx, neck) for a
spherical target (Ø=5 cm) with uniform target dose to calculate the LETD distribution.
Measurements were performed at the University Medical Center Groningen proton therapy
center (Proteus Plus, IBA) using a
+
-probe utilizing silicon on insulator microdosimeters
capable of detecting lineal energies as low as 0.15 keV/m in tissue. Dose averaged mean
lineal energy 𝛾̅̅𝐷̅ depth-profiles were measured for 70 and 130 MeV spots in water and for
the three treatment plans in water and an anthropomorphic phantom. The ̅𝛾̅𝐷̅ measurements
were compared to the LETD calculated in the TPS and MCS independent dose calculation
engine. D⋅𝛾̅̅𝐷̅ was compared to D⋅LETD in terms of a gamma-index with a distance-toagreement criteria of 2 mm and increasing dose difference criteria to determine the criteria
for which a 90% pass rate was accomplished.
Measurements of D⋅𝛾̅̅𝐷̅ were in good agreement with the D⋅LETD calculated in the TPS and
MCS. The 90% passing rate threshold was reached at different D⋅LETD difference criteria for
single spots (TPS: 1% MCS: 1%), treatment plans in water (TPS: 3% MCS: 6%) and
treatment plans in an anthropomorphic phantom (TPS: 6% MCS: 1%).
We conclude that D⋅LETD calculations accuracy in the RayStation TPS and open MCSquare
are within 6%, and sufficient for clinical D⋅LETD evaluation and optimization. These findings
remove an important obstacle in the road towards clinical implementation of D⋅LETD
evaluation and optimization of proton therapy treatment plans.
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James, Benjamin; Tran, Linh T.; Bolst, David; Perrachi, Stefania; Davis, Jeremy & Prokopovich, Dale A.
[Show all 16 contributors for this article]
(2019).
SOI Thin Microdosimeters for High LET Single Event Upset Studies in Fe, O, Xe and Cocktail Ion Beam Fields.
IEEE Transactions on Nuclear Science.
ISSN 0018-9499.
67(1),
p. 146–153.
doi:
10.1109/TNS.2019.2939355.
Full text in Research Archive
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The response of a 5 μm thin silicon on insulator (SOI) 3D microdosimeter was investigated for single event upset applications by measuring the LET of different high LET ions. The charge collection characteristics of the device was performed using the Ion Beam Induced Charge collection
(IBIC) technique with 3 and 5.5 MeV He2+ ions incident on the microdosimeter. The microdosimeter was irradiated with 16O, 56Fe and 124Xe ions and was able to determine the LET within 5% for most configurations apart from 124Xe. It was observed that on average, measured LET was 12% lower for 30 MeV/u 124Xe ion traversing through different thickness Kapton absorbers in comparison to Geant4 simulations. This
discrepancy can be partly attributed to uncertainties in the thickness of the energy degraders and thickness of the SOI layer of the devices. The effects of overlayer thickness variation is not easy observed for ions with much lower LET as O and Fe. Based on that it is difficult to make conclusion that plasma effect is observed for 30 MeV/u 124Xe ions and further research to be carried out for ion with LET higher than 12 MeV/µm.
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Peracchi, Stefania; James, Benjamin; Tran, Linh T.; Bolst, David; Prokopovich, Dale A. & Davis, Jeremy
[Show all 14 contributors for this article]
(2019).
A solid-state microdosimeter for dose and radiation qualty monitoring for astronauts in space.
IEEE Transactions on Nuclear Science.
ISSN 0018-9499.
67(1),
p. 169–174.
doi:
10.1109/TNS.2019.2943597.
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This article presents a study of the response of the silicon on insulator (SOI) microdosimeter with 3-D sensitive volumes (SVs) to 400 MeV/u 16 O and 500 MeV/u 56 Fe ions mimicking galactic cosmic rays outside and inside the International Space Station (ISS). An average quality factor ( $\bar {Q}$ ) and the dose equivalent ( $H$ ) of the radiation field were obtained experimentally, and the results were compared with GEANT4 simulations.
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Bolst, David; Gautelli, Susanna; Tran, Linh T.; Davis, Jeremy; Chartier, Lachlan & Prokopovich, Dale A.
[Show all 16 contributors for this article]
(2019).
Validation of Geant4 for silicon microdosimetry in heavy ion therapy.
Physics in Medicine and Biology.
ISSN 0031-9155.
65(4).
doi:
10.1088/1361-6560/ab586a.
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Microdosimetry is a particularly powerful method to estimate the relative biological effectiveness (RBE) of any mixed radiation field. This is particularly convenient for therapeutic heavy ion therapy (HIT) beams, referring to ions larger than protons, where the RBE of the beam can vary significantly along the Bragg curve. Additionally, due to the sharp dose gradients at the end of the Bragg peak (BP), or spread out BP, to make accurate measurements and estimations of the biological properties of a beam a high spatial resolution is required, less than a millimetre. This requirement makes silicon microdosimetry particularly attractive due to the thicknesses of the sensitive volumes commonly being ∼10 µm or less. Monte Carlo (MC) codes are widely used to study the complex mixed HIT radiation field as well as to model the response
of novel microdosimeter detectors when irradiated with HIT beams. Therefore it is essential to validate MC codes against experimental measurements.
This work compares measurements performed with a silicon microdosimeter in monoenergetic 12C , 14N and 16O ion beams of therapeutic energies, against simulation results
calculated with the Geant4 toolkit. Experimental and simulation results were compared in terms of microdosimetric spectra (dose lineal energy, d(y)), the dose mean lineal energy, yD and the RBE10, as estimated by the microdosimetric kinetic model (MKM). Overall Geant4
showed reasonable agreement with experimental measurements. Before the distal edge of the BP, simulation and experiment agreed within ∼10% for yD and ∼2% for RBE10. Downstream of the BP less agreement was observed between simulation and experiment, particularly for the
12C and 16O beams. Simulation results downstream of the BP had lower values of yD and RBE10 compared to the experiment due to a higher contribution from lighter fragments compared to heavier fragments.
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Tran, Linh T.; Chartier, Lachlan; Bolst, David; Davis, Jeremy; Prokopovich, Dale A. & Pogossov, Alex
[Show all 16 contributors for this article]
(2018).
In-field and out-of-file application in 12C ion therapy using fully 3D silicon microdosimeters.
Radiation Measurements.
ISSN 1350-4487.
115,
p. 55–59.
doi:
10.1016/j.radmeas.2018.06.015.
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This paper presents recent development of Silicon on Insulator (SOI) detectors for microdosimetry at the Centre for Medical Radiation Physics (CMRP) at the University of Wollongong. A new CMRP SOI microdosimeter design, the 3D mushroom microdosimeter is presented. Modification of SOI design and changes to the fabrication processes have led to improved definition of the microscopic sensitive volumes (SV), and thus to better modelling of the deposition of ionizing energy in a biological cell. The electrical and charge collection properties of the devices have been presented in previous works. In this study, the response of the microdosimeters in monoenergetic and spread out Bragg peak therapeutic 12C ion beam at Heavy Ion Medical Accelerator in Chiba (HIMAC, Japan) are presented. Derived relative biological effectiveness (RBE) in 12C ion radiation therapy matches the tissue equivalent proportional counter (TEPC) well, along with outstanding spatial resolution. The use of SOI technology in experimental microdosimetry offers simplicity (no gas system or HV supply), high spatial resolution, low cost, high count rates capabilities for beam characterisation and quality assurance (QA) in charged particle therapy.
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Tran, Linh T.; Bolst, David; Guatelli, Susanna; Pogossov, Alex; Petasecca, Marco & Lerch, Michael L.F.
[Show all 16 contributors for this article]
(2018).
The relative biological effectiveness for carbon, nitrogen, and oxygen ion beams using passive and scanning techniques evaluated with fully 3D silicon microdosimeters.
Medical Physics.
ISSN 0094-2405.
45(5),
p. 2299–2308.
doi:
10.1002/mp.12874.
Full text in Research Archive
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Background: The aim of this study was to measure the microdosimetric distributions of a carbon pencil-beam scanning (PBS) and passive scattering system as well as to evaluate the relative biological effectiveness (RBE) of different ions, namely 12C, 14N and 16O, using a silicon-on-insulator (SOI) microdosimeter with well-defined 3D sensitive volumes (SV). Geant4 simulations were performed with the same experimental setup and results were compared to the experimental results for benchmarking.
Method: Two different silicon microdosimeters with rectangular parallelepiped and cylindrical shaped SVs, both 10 µm in thickness were used in this study. The microdosimeters were connected to low noise electronics which allowed for the detection of lineal energies as low as 0.15 keV/μm in tissue. The silicon microdosimeters provide extremely high spatial resolution and can be used for in-field and out-of-field measurements in both passive scattering and PBS deliveries. The response of the microdosimeters was studied in 290 MeV/u 12C, 180 MeV/u 14N, 400 MeV/u 16O passive ion beams, and 290 MeV/u 12C scanning carbon therapy beam at Heavy Ion Medical Accelerator in Chiba and Gunma University Heavy Ion Medical Center, Japan, respectively. The microdosimeters were placed at various depths in a water phantom along the central axis of the ion beam, and at the distal part of the Spread Out Bragg Peak (SOBP) in 0.5 mm increments. The RBE values of the pristine Bragg peak (BP) and SOBP were derived using the microdosimetric lineal energy spectra and the modified microdosimetric kinetic model (MKM), using MKM input parameters corresponding to human salivary gland (HSG) tumour cells. Geant4 simulations were performed in order to verify the calculated depth-dose distribution from the treatment planning system and to compare the simulated dose-mean lineal energy to the experimental results.
Results:
For a 180 MeV/u 14N pristine BP, the dose-mean lineal energy (yD) ̅obtained with two types of silicon microdosimeters started from approximately 29 keV/µm at the entrance to 92 keV/µm at the BP, with a maximum value in the range of 412 to 438 keV/µm at the distal edge. For 400 MeV/u 16O ions, the dose-mean lineal energy (yD) ̅started from about 24 keV/µm at the entrance to 106 keV/µm at the BP, with a maximum value of approximately 381 keV/µm at the distal edge. The maximum derived RBE10 values for 14N and 16O ions were found to be 3.10 ± 0.47 and 2.93 ± 0.45, respectively. Silicon microdosimetry measurements using pencil beam scanning 12C ions were also compared to the passive scattering beam.
Conclusions: These SOI microdosimeters with well-defined 3D SVs have applicability in characterising heavy ion radiation fields and measuring lineal energy deposition with sub-millimetre spatial resolution. It has been shown that the dose-mean lineal energy increased significantly at the distal part of the BP and SOBP due to very high LET particles. Good agreement was observed for the experimental and simulation results obtained with silicon microdosimeters in 14N and 16O ion beams, confirming the potential application of SOI microdosimeter with 3DSV for quality assurance in charged particle therapy.
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Tran, Linh T.; Chartier, Lachlan; Prokopovich, Dale A.; Bolst, David; Povoli, Marco & Summanwar, Anand
[Show all 16 contributors for this article]
(2017).
Thin silicon microdosimeter utilizing 3D MEMS fabrication technology: Charge collection study and its application in mixed radiation fields.
IEEE Transactions on Nuclear Science.
ISSN 0018-9499.
65(1),
p. 467–472.
doi:
10.1109/TNS.2017.2768062.
Full text in Research Archive
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New 10-μm-thick silicon microdosimeters utilizing 3-D technology have been developed and investigated in this paper. The TCAD simulations were carried out to understand
the electrical properties of the microdosimeters’ design. A charge collection study of the devices was performed using 5.5-MeV He2+ ions which were raster scanned over the surface of the detectors and the charge collection median energy maps were obtained and the detection yield was also evaluated. The Devices were tested in a 290 MeV/u carbon ion beam at the Heavy Ion Medical Accelerator in Chiba (HIMAC) in Japan. Based on the microdosimetric measurements, the quality factor and dose equivalent out of field were obtained in a mixed radiation field mimicking the radiation environment for spacecraft in deep space.
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Alagoz, Enver; Bräuer-Krisch, Elke; Bravin, Alberto; Cornelius, Iwan; Fournier, Pauline & Hansen, Thor-Erik
[Show all 18 contributors for this article]
(2016).
Multi-strip silicon sensors for beam array monitoring in micro-beam radiation therapy.
Physica Medica.
ISSN 1120-1797.
32(12),
p. 1795–1800.
doi:
10.1016/j.ejmp.2016.11.005.
Full text in Research Archive
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We present here the latest results from tests performed at the ESRF ID17 and ID21 beamlines for the characterization of novel beam monitors for Microbeam Radiation Therapy (MRT), which is currently being implemented at ID17. MRT aims at treating solid tumors by exploiting an array of evenly spaced microbeams, having an energy spectrum distributed between 27 and 600 keV and peaking at 100 keV. Given the high instantaneous dose delivered (up to 20 kGy/s), the position and the intensity of the microbeams has to be precisely and instantly monitored. For this purpose, we developed dedicated silicon microstrip beam monitors. We have successfully characterized them, both with a microbeam array at ID17, and a submicron scanning beam at ID21. We present here the latest results obtained in recent tests along with an outlook on future developments.
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Bräuer-Krisch, Elke; Adam, Jean-Francois; Alagoz, Enver; Bartzsch, Stefan; Crosbie, Jeff & DeWagter, Carlos
[Show all 22 contributors for this article]
(2015).
Medical physics aspects of the synchrotron radiation therapies: Microbeam radiation therapy (MRT) and synchrotron stereotactic radiotherapy (SSRT).
Physica Medica.
ISSN 1120-1797.
31(6),
p. 568–583.
doi:
10.1016/j.ejmp.2015.04.016.
Full text in Research Archive
Show summary
Stereotactic Synchrotron Radiotherapy (SSRT) and Microbeam Radiation Therapy (MRT) are both novel approaches to treat brain tumor and potentially other tumors using synchrotron radiation. Although the techniques differ by their principles, SSRT and MRT share certain common aspects with the possibility of combining their advantages in the future. For MRT, the technique uses highly collimated, quasi-parallel arrays of X-ray microbeams between 50 and 600 keV. Important features of highly brilliant Synchrotron sources are a very small beam divergence and an extremely high dose rate. The minimal beam divergence allows the insertion of so called Multi Slit Collimators (MSC) to produce spatially fractionated beams of typically ∼25–75 micron-wide microplanar beams separated by wider (100–400 microns center-to-center(ctc)) spaces with a very sharp penumbra. Peak entrance doses of several hundreds of Gy are extremely well tolerated by normal tissues and at the same time provide a higher therapeutic index for various tumor models in rodents. The hypothesis of a selective radio-vulnerability of the tumor vasculature versus normal blood vessels by MRT was recently more solidified.
SSRT (Synchrotron Stereotactic Radiotherapy) is based on a local drug uptake of high-Z elements in tumors followed by stereotactic irradiation with 80 keV photons to enhance the dose deposition only within the tumor. With SSRT already in its clinical trial stage at the ESRF, most medical physics problems are already solved and the implemented solutions are briefly described, while the medical physics aspects in MRT will be discussed in more detail in this paper.
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Povoli, Marco; Alagoz, Enver; Bravin, Alberto; Cornelius, Iwan; Bräuer-Krisch, Elke & Fournier, Pauline
[Show all 18 contributors for this article]
(2015).
Functional characterisation of novel silicon beam monitors for the micro-beam radiation therapy,
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2015, 31 Oct.-7 Nov. 2015.
IEEE (Institute of Electrical and Electronics Engineers).
ISSN 9781467398633.
doi:
10.1109/NSSMIC.2015.7581894.
Full text in Research Archive
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Among the new emerging cancer therapies, Microbeam Radiation Therapy (MRT) is currently showing very promising results in terms of limiting or decreasing tumor growth while keeping the damage to healthy tissue to a minimum. The MRT is able to deliver unprecedented dose rates of up to 20 kGy/s, posing important questions in terms of treatment planning and patient safety during treatment. For this reason, a beam monitoring system must be built, in which a detector acquires the microbeam array profile in real-time. In case of anomalies detection, the detector signals the beam-line to close the shutter as an emergency safety measure. Many sensors technologies for beam monitoring are currently being considered and silicon strip detectors seem to be very promising candidates. In this study the characterisation in full MRT conditions of a novel silicon strip detector is reported explaining strengths and weaknesses of the devices. Modifications to the sensor layout are also suggested in this study
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Povoli, Marco; Alagoz, Enver; Bravin, Alberto; Cornelius, Iwan; Bräuer-Krisch, Elke & Fournier, Pauline
[Show all 18 contributors for this article]
(2015).
Thin silicon strip detectors for beam monitoring in Micro-beam Radiation Therapy.
Journal of Instrumentation (JINST).
10(11).
doi:
10.1088/1748-0221/10/11/P11007.
Full text in Research Archive
Show summary
Microbeam Radiation Therapy (MRT) is an emerging cancer treatment that is currently being developed at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. This technique uses a highly collimated and fractionated X-ray beam array with extremely high dose rate and very small divergence, to benefit from the dose-volume effect, thus sparing healthy tissue. In case of any beam anomalies and system malfunctions, special safety measures must be installed, such as an emergency safety shutter that requires continuous monitoring of the beam intensity profile. Within the 3DMiMic project, a novel silicon strip detector that can tackle the special features of MRT, such as the extremely high spatial resolution and dose rate, has been developed to be part of the safety shutter system. The first prototypes have been successfully fabricated, and experiments aimed to demonstrate their suitability for this unique application have been performed. Design, fabrication and the experimental results as well as any identified inadequacies for future optimisation are reported and discussed in this paper.
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Povoli, Marco; Alagoz, Enver; Bravin, Alberto; Cornelius, Iwan; Bräuer-Krisch, Elke & Fournier, P.
[Show all 17 contributors for this article]
(2014).
Simulation and Testing of Thin Microstrip Silicon Dosimeters for the Microbeam Radiation Therapy.
IEEE Nuclear Science Symposium Conference Record.
ISSN 1082-3654.
doi:
10.1109/NSSMIC.2014.7430903.
Full text in Research Archive
Show summary
The Micro-Beam Radiation Therapy (MRT) is a promising newly emerged cancer treatment currently under development at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Several safety requirements must be complied with, prior to the human clinical trials of the MRT such as the ability to send a signal to the emergency beam shutter in case of any beam anomalies, in order to avoid exposing the patient to excess radiation. This will require a beam monitor that can work under the demanding operating conditions of the MRT. A good candidate for this application is a silicon strip detector. A novel device layout has been proposed and numerical simulations were performed to carry out the optimisation of design and fabrication at SINTEF MiNaLab, Oslo, Norway. Simulation results and preliminary electrical measurements on wafer level are reported and discussed.
View all works in NVA
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Choolakkal, Arun Haridas; Povoli, Marco; O'Neill, George; Högberg, Hans; Pedersen, Henrik & Birch, Jens
(2023).
Conformal deposition of BxC on Si chip-substrates for solid-state neutron detectors.
Full text in Research Archive
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Choolakkal, Arun Haridas; Povoli, Marco; O'Neill, George; Högberg, Hans; Pedersen, Henrik & Birch, Jens
(2023).
Conformal deposition of BxC thin films for solid-state neutron detectors.
Full text in Research Archive
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Vincent, de Rover; Paino, Jason R; Moore, Lawson; Kok, Angela; Petasecca, Marco & Povoli, Marco
[Show all 10 contributors for this article]
(2021).
First Application of Silicon Carbide Detector in Synchrotron X-Ray Radiation Fields.
Full text in Research Archive
Show summary
New detectors designed to have a radiation-stable, accurate and more human tissue-like response when measuring the radiation dose delivered in Synchrotron X-ray radiation fields is particularly important in Microbeam Radiation Therapy. This paper focusses on demonstrating an epitaxial silicon-carbide (EPI-SiC) detector specifically manufactured for such radiation fields. In particular, how the EPI-SiC detector responds to the intense radiation with applied bias and any measureable radiation damage effects that may impact on the ability of the EPI-SiC detector to accurately measure the radiation doses delivered. The EPI-SiC detector responds well to synchrotron X-ray broad beams generated at the Australian Synchrotron. In edge-on detector readout mode the sharp penumbra of the X-ray beam defined by a 0.532 mm wide rectangular beam aperture can easily be observed. At an applied reverse bias of 100 V, 65 nA of photocurrent is measured when the EPI-SiC detector is fully illuminated by the beam. With approximately 30,000 Gy delivered (60 times more than the peak dose typically delivered in MRT) we observe a 19.4 % increase in the measured reverse bias dark current. These results are very encouraging, and indicate that the prototype EPI-SiC detectors are suitable for use in these intense synchrotron radiation environments.
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Tran, Linh T.; Benjamin, James; David, Bolst; Wagenaar, Dirk; Goethem, Marc-Jan & Both, Stefan
[Show all 13 contributors for this article]
(2021).
Silicon based microdosimeter for variable LETD determination in proton radiotherapy planning.
Full text in Research Archive
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Variations in proton relative biological effectiveness (RBE) with dose averaged linear energy transfer (LET) remain one of the largest sources of uncertainty in proton radiotherapy. Biological robust LET based optimization has been introduced into some clinical treatment planning systems (TPS) to avoid normal tissue toxicity (Monte Carlo (MC) based calculation RaySearch commercial TPS). This work aims to introduce a new single cylindrical sensitive volume (SV) SOI microdosimeter modelling a biological cell using a 3D detector technology and can be operated in high intensity pencil beam scanning (PBS). The microdosimeter was applied for LET verification computed in a MC dose engie of RaySearch TPS. Various treatment plans were generated in a research version of RayStation v6R TPS using pencil beam scanning at University Medical Center Groningen facility, the Netherlands. Two plans were created consisting of a single pristine Bragg peak of 70 MeV and 130 MeV in a homogeneous water phantom and three PBS treatment plans were created to treat a spherical target with a 5 cm diameter with uniform dose coverage, in the CIRS 731- HN anthropomorphic head and neck phantom. The silicon microdosimeter system was used to measure these plans and to compare with Geant4 simulation for the same configuration and setup. Based on measured microdosimetric quantity, the dose mean lineal energy (yD), an additional dose for each plan was obtained. It has been observed that additional dose could increase up to 47% compared to prescribed physical dose assuming constant RBE of 1.1. Good agreement was observed between additional dose obtained based on measured yD and calculated LET by RaySearch TPS. This work ahs demonstrated that the single SV silicon microdosimeter system developed by CMRP and fabricated at SINTEF is a very useful and unique tool to validate LET computed in RaySearch TPS and will allow new quality assurance for biologically optimized proton therapy planning.
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Dorholt, Ole; Heggelund, Andreas Løkken; Huiberts, Simon; Kok, Angela; Koybasi, Ozhan & Lauritzen, Magne Eik
[Show all 12 contributors for this article]
(2019).
Radiation hard pixel '3D' sensors for use in ATLAS-ITk
at LHC.
Full text in Research Archive
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In preparation for operation at the High Luminosity LHC, the tracking system of the ATLAS experiment is replaced
with a new inner tracker, the ITk. The innermost layers of this system must be designed to withstand a fluence of
more than 10^16 cm-2 1 MeV neutron equivalents. At SINTEF, Norway, silicon pixel sensors have been produced in
‘3D’ design to tolerate such high fluences. Some of these sensors have been mounted with prototype readout
electronics designed for operation at the ITk, the RD53A chip. The assembled modules have been shown to operate
according to expectation in proton and electron test beams at CERN and DESY. Assemblies have subsequently
been irradiated with protons up to a fluence of 5 x 10
^15 protons cm-2 as well as with neutrons at a fluence of 10^16 cm-
2 . Subsequent beam tests show that the sensors can operate after such fluences with good efficiency. Results from
these tests are presented.
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Koybasi, Ozhan; Kok, Angela; Summanwar, Anand; Povoli, Marco & Breivik, Lars
(2019).
Fabrication of active-edge detectors
without support wafer using a
unique "perforated edge" approach.
Full text in Research Archive
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Minimisation of insensitive volume in silicon sensors is highly demanded in many applications for high energy physics, structural biology, synchrotron experiments and nuclear medicine. A large contribution to this insensitive volume is the guard rings and current terminating structures required in conventional planar silicon sensor that surround the chip periphery. The maximum size of silicon sensors that is optimal is limited by the diameter or dimensions of the substrate and the overall yield of the fabrication process (the smaller the sensors the higher the overall manufacture yield). For these reasons, many imaging applications require the tiling of multiple sensors modules together to cover large areas. For standard silicon detectors, the insensitive guard-ring regions will result in a loss of information and result in imperfect images. Stanford Nanofabrication Facility (SNF), was the first to introduce the 'active edge', a new edge terminating structure, that replaces the insensitive guard ring area. The concept is based on the original '3D technology' proposed by S. Parker et al in 1995. The technique requires through silicon substrate electrodes, formed first by etching high aspect ratio holes using modern micromachining known as Deep Reactive Ion Etching (DRIE), originally developed for MEMS technologies. Several laboratories worldwide have investigated this approach using a support wafer that is required to provide mechanical integrity once the through substrate trench surrounding the entire periphery of the sensor is etched. The trench electrodes are subsequently doped using gas phase doping technique. Once the sensors are completed, the support wafer must be removed. This further complicates an already difficult technology. SINTEF have recently investigated a new edgeless design concept, known as the 'perforated edge'. The design allows possible future manufacture without the use of the support wafer. The integrity of the device wafer is retained since only small segments are removed during DRIE. We present here the design concept, fabrication, and the first characterization of this newly developed edgeless detector that can potentially be fabricated by a cost-effective manufacture process with high yield, suitable for state-of-the-art pixel sensor module assembly.
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Mendicino, Roberto; Betta, Gian-Franco Dalla; Kok, Angela; Koybasi, Ozhan; Povoli, Marco & Summanwar, Anand
(2019).
Characterization of Sintef 3D diodes with trenches geometry before and after neutron irradiation.
Full text in Research Archive
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Detectors with high radiation tolerance and high time resolution are required for charged particle
in high physics and space applications.
3D detectors were introduced by S. Parker 1 in the middle 90’ and they represented a starting point
for evolved device able to work at fluency up to 2 × 10^16 neq/cm2. A limit to 3D detector is the not
uniformity of electrical field that translates in a not uniform charge collection efficiency after high
radiation doses and an uneven timing for the signal.
Different solution has been proposed in the last decade (eg. Hexagonal geometry of the electrodes)
but many TCAD device simulations suggest parallel trenches as best solution [2]. Two different geometries have been taken into consideration both with parallel trenches. The distance between
trenches of opposite sign is 25 µm in both case and the distance between trenches with equal sign
is fixed to 50 µm. The main difference is trenches length that is respectively of 100 µm and 50 µm.
They have been designed and fabricated by SINTEF MiNaLab, Oslo, Norway on SI-SI, high resistivity,
float zone substrates (6−12 kΩ cm) with an active thickness of 100 µm.
The neutron irradiation of the sensors has been carried out at the TRIGA Mark II reactor at JSI
(Ljubljana, Slovenia) in May 2018 and the characterization was performed afterwards.
The functional characterization has been performed by using a position resolved laser and by using
a setup designed for this type of measurements.
The radiation source is a pulsed laser with a wavelength of 1064 nm that allow a quasi-uniform
release of charge in the silicon substrate and a nominal pulse of 40ps. The laser source is integrated
in a microscope optics that can be moved in the 3 axes with a precision on the micrometer range.
In additional, the detectors are located in a vacuum chamber that avoid problems related to the
humidity/hoarfrost when the detectors works at low temperature. The detector is connected by
using two tungsten micro-needles connected to the readout circuits.
The results are two-dimensional maps of the signal across the 3D single basic cell. The measure has
been repeated for different voltages and temperature.
The data are then normalized to the signals acquired on non-irradiated samples.
At the conference we will report on the device design and technology, as well as on selected results
from the electrical and functional characterization.
[1] S. I. Parker et al., ”3D-A proposed new architecture for solid-state
radiation detectors”, Nucl. Instrum. Methods A, vol. 395, pp. 328-343,
1997.
[2] R. Mendicino, et al. “3D trenched-electrode sensors for charged particle tracking and timing.”
Nucl. Instrum. Methods A 2019.
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Koybasi, Ozhan; Kok, Angela; Summanwar, Anand; Povoli, Marco; Breivik, Lars & Bergamaschi, Anna
[Show all 9 contributors for this article]
(2019).
Characterization of active-edge detectors fabricated without support wafer.
Full text in Research Archive
Show summary
Silicon radiation sensors typically have an inactive volume at the device periphery necessary to accommodate multiple guard-rings and current terminating structures necessary to deliver increased
breakdown voltage and stability and to shield the active area from the defects induced by the dicing
procedure.
The extension of the dead region can be as wide as a few mm, depending on the thickness and resistivity of the wafer as well as on the performance requirements for the sensor. There is a demand in both
industrial and scientific communities for “edgeless” silicon radiation sensors where the insensitive
edge area is reduced to a minimum. This would allow for the reduction of geometrical inefficiencies
and for the seamless tiling of multiple sensors into matrices, to ensure large area coverage without
distortions or missing data.
The need for “edgeless” detectors has initiated the efforts to engineer the state-of-the-art silicon radiation sensors in order to drastically reduce the dead periphery of the devices. The fabrication of
edgeless radiation detector has so far been demonstrated at SINTEF, VTT, and FBK. The “edgeless”
feature is realized by etching deep trenches around the active area of the sensor using deep reactive
ion etching (DRIE) and by doping the trenches heavily to prevent the depletion region from reaching
the damages induced by the etching procedure. In order to maintain the wafer integrity during and
after the DRIE process, the device wafer is fusion bonded to a support wafer prior to DRIE, which, for
most applications, must be removed after the sensor processing has been completed. The removal
of the support wafer is very challenging, making this traditional approach far from ideal for productions with high yield and low cost.
At SINTEF we have recently developed a simplified method to fabricate edgeless sensors without
the need for a support wafer. This method was conceptualized. Instead of a continuous trench
surrounding the active area of the sensor, a segmented trench is created, leaving enough silicon in
place to ensure mechanical integrity without the use of a support wafer. We call this approach “perforated” edge (Fig.1). After doping of the trench segments, the unetched material between segments
is doped by deep drive-in, thereby effectively forming a fully doped “wall” throughout the entire
thickness of sensor. Once the wafer processing is completed, the edgeless sensors can be safely singulated using conventional saw dicing methods.
The sensors presented here, were fabricated on 300 µm thick, FZ high resistivity n-type wafers. The
electrical characterization was performed using a manual probe station before and after dicing, on
5x5 mm2 edgeless diodes. The full depletion voltage as extracted from C-V measurements is ~45 V.
The leakage current at full depletion is < 100 pA, comparable to the leakage current of their counterparts with traditional guard ring edge termination. The breakdown voltage is still above 300 V even
after dicing through the center of the trench segments, demonstrating that this novel edge termination can prevent edge-related early discharge. After dicing 10 µm inwards from the center of trench
segments, the leakage current dramatically increases at 135 V as the depletion region is not shielded
from the dicing region anymore.
We have successfully demonstrated a method for the fabrication of edgeless silicon radiation sensors
with edge insensitivity of < 10 µm, without using a support wafer. This method is simpler, more cost
effective, and delivers a higher throughput when compared to the traditional edgeless detector fabrication methods that have been previously demonstrated. At the conference we will present details
on design, fabrication, electrical and functional characterization with focus on the signal efficiency
and response uniformity of the edge termination of these newly developed edgeless detectors.
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Heggelund, Andreas Løkken; Stugu, Bjarne; Røhne, Ole Myren; Sandaker, Heidi; Read, Alexander Lincoln & Dorholt, Ole
[Show all 11 contributors for this article]
(2019).
Test beam characterization of irradiated SINTEF 3D pixel sensors.
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The upcoming High Luminosity LHC (HL-LHC) puts stringent requirements on the tracking detectors situated closest to the interaction point in the planned Inner Tracker (ITk) of the ATLAS experiment. 3D pixel detectors have been proposed as a candidate for the innermost layers of the ITk since these detectors decouple the sensor thickness and the inter-electrode spacing, effectively increasing the radiation hardness.
The SINTEF prototyping R&D run (run 4) for radiation hard 3D silicon pixel detectors features ultra thin device layouts down to 100 and 50um active thicknesses, with a variety of compatibility. The layouts discussed here are compatible with the ATLAS pixel readout ASIC RD53A, allowing nominal signal thresholds below 1ke-.
The flip-chip and UBM processing steps was done by Fraunhofer IZM in Berlin, and these hybrids were mounted on Single Chip Cards (SCC) and bonded at the University of Oslo.
Noise vs. thickness scans demonstrates that the capacitance is dominated by device thickness, inferring less intrinsic noise in thinner devices.
Pre-irradiation tests, performed at the SPS testbeam facility at CERN shows an efficiency loss that is consistent with the non-active column geometry of the 50x50 1E pixel matrix, giving an overall efficiency > 97%. While devices irradiated to a fluence of 5x10^15 neqcm-2 have an efficiency within optimistic expectations for such thin devices.
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Segal, Julie; Lietaer, Nicolas & Povoli, Marco
(2019).
Thinned Commercial Foundry-built High Energy Physics Sensors using Microwave Anneal.
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In order to support the high luminosity upgrades at ATLAS and CMS, thinned silicon sensors for hybrid pixel detectors are critical to improve radiation hardness, reduce detector mass, and address high occupancy rates. Because silicon wafer processing tools are not equipped to handle thin wafers, the thinning step cannot be performed until after the majority of the processing steps are complete, requiring post-processing to create the doped region that constitutes the diode contact at the backside of the wafer. However, the high temperature anneal required to activate the dopant would be damaging to the existing front side structures. A new microwave annealing technology can activate the backside implant at low temperature, without damaging the frontside structures. We employed this technique to post-process 6-inch wafers from two different high energy physics (HEP) sensor foundries. Results are promising, indicating that the microwave anneal backside has potential to become a cost-effective solution for manufacturing thin sensors for large area HEP detectors.
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Kok, Angela; Povoli, Marco; Summanwar, Anand; Tran, Linh T.; Petasecca, Marco & Lerch, Michael L.F.
[Show all 7 contributors for this article]
(2019).
Fabrication challenges of silicon-based microdosimeter using 3D technology.
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Microdosimetry provides measurements of stochastic lineal energy deposition on a micrometric sensitive volume (SV), comparable to human cell dimensions. Conventional microdosimeter uses a tissue equivalent proportional counter (TEPC) that requires high voltage operation, are bulky and have poor spatial resolution. Silicon-on-insulator (SOI) microdosimeter fabricated using the so-called '3D technology', provides true cell-like SV that is encapsulated by a through substrate electrode. Furthermore, such detectors provide many attractive advantages such as micrometric spatial resolution, compact design, and easy coupling to readout electronics that provide real-time on-line monitoring. SINTEF in collaboration with Centre for Medical Radiation Physics (CMRP), have developed a full 3D SOI microdosimeter, a 5th generation SOI microdosimeter. Characterisation results of the first prototype run at several heavy ion therapy (HIT) centres demonstrated excellent results with derived radiobiological effectiveness (RBE), comparable with TEPC. Foreseen future manufacture of such dosimeters remains a challenge. One of the major difficulties is the integrity of metal connection joining individual sensitive volumes where the metal must trespass the the 3D circular electrodes encapsulating the entire SVs. The problem is further exasperated by the further enhancement in microdosimetry where all silicon surrounding the SVs is removed. This paper presents the first fabrication review of results and challenges over the several prototype runs carried out at SINTEF Minalab. The review and investigation aim to generate a fabrication technology that have a potential to provide a commercially viable manufacture process with a high yield throughput. Challenging processes such as removal of bulk silicon outside of the microscopic SVs and deposition of tissue equivalent material will also be discussed.
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Koybasi, Ozhan; Povoli, Marco; Kok, Angela; Summanwar, Anand; Breivik, Lars & Hansen, Trond Andreas
[Show all 9 contributors for this article]
(2018).
Status of 3D detector development at SINTEF for ITk Upgrade.
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SINTEF in collaboration with University of Oslo have been performing R&D activities on 3D detectors with the aim to qualify to be a production site for ITk upgrade. In this context, a 3D detector
fabrication run has been completed recently with very promising results. Various sensor geometries
with active edges were implemented, and the fabrication was carried out on 6-inch Si-Si wafers with
sensor substrate thicknesses of 100 µm and 50 µm using single-sided processing approach. We will
present the electrical test results; assembly, irradiation and test beam plans; and the plans for the
next fabrication run
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Mendicino, Roberto; Betta, G-F. Dalla; Forcolin, GT; Kok, Angela; Koybasi, Ozhan & Neha, Neha
[Show all 8 contributors for this article]
(2018).
Characterization of SINTEF 3D diodes with different inter-electrode spacings after neutron irradiation up to 2 x 10 e16 neutron equivalent/cm^2.
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Due to radiation hardness requirements, 3D detectors are the best candidate technology for the innermost tracking layers at the High Luminosity LHC (HL-LHC) as well as for radiation monitoring in long space missions. In the framework of the project "Three-dimensional Low-Voltage Silicon Detectors" funded by ESA, SINTEF Minalab has developed novel full 3D detectors with slim and active edges. Functional tests to measure the charge collection efficiency after irradiation at the fluences expected at the HL-LHC cannot be accurately measured using the current readout chips due to their limited radiation tolerance. As an alternative, small-size 3D diodes connected to discrete read-out channels can be used. This study is aimed at investigating the performance of 3D sensors of different inter-electrode spacing which were designed and fabricated by SINTEF Minalab (Oslo, Norway). At the conferece, we will recall the main design and technological aspects for these sensors, and report selected results from their characterization with IR laser after neutron irradiation up to 2 x 10e16 neutron equivalent /cm^2.
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Kok, Angela; Koybasi, Ozhan; Povoli, Marco; Summanwar, Anand; Dorholt, Ole & Heggelund, Andreas Løkken
[Show all 11 contributors for this article]
(2018).
SINTEF 3D Pixel Run-4 fabrication and characterisation.
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This contribution details the fabrication procedure together with electrical characterisation results. The pre-irradiation evaluation of the sensor assemblies will be shown and the irradiation campaign will be described. Post-irradiation results will be discussed and analysed and future planned development and activities will be outlined, aiming at the qualification of the Norwegian collaboration for the production of 3D pixel sensors for the innermost layer of the ATLAS ITK.
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James, Benjamin; Tran, Linh T.; Bolst, David; Pan, Vladimir M.; Prokopovich, Dale A. & Petasecca, Marco
[Show all 13 contributors for this article]
(2018).
Fully 3D Sensitive Volume Microdosimeter Charge Collection and Radiation Damage Studies.
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In the course of this research, a radiation damage study of 3D microdosimeter structures were carried out using 5.5 MeV He2+ and 24 MeV C-12 ions microbeam. Radiation damage study post irradiation of the microdosimeters with low energy Li, C, O, ti ion was also investigated. Additionally, electrical and charge collection properties were studied for a new 3D SV microdosimeter covered with a tissue equivalent material.
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Povoli, Marco; Koybasi, Ozhan; Kok, Angela; Hansen, Trond Andreas & Breivik, Lars
(2018).
Development of N-on-P planar technology at SINTEF MiNaLab.
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SINTEF MiNaLab has a long-standing experience in the production of planar radiation detectors on
N-type silicon substrates. In recent years, a growing interest in sensors produced on P-type substrates was demonstrated on many fronts. N-on-P sensor technology is now becoming the “to-go
choice”, especially in fields where radiation hardness is crucial (e.g. CERN experiments) and/or a
faster response time is needed.
In the past two years SINTEF MiNaLab has invested heavily in the development of its own N-on-P
silicon sensors technology. Great effort was put into assessing different layout implementations that
would optimize the sensor’s electrical characteristics while achieving the desired surface radiation
hardness.
We have recently completed a new prototyping fabrication run of N-on-P silicon sensors. The device
of reference for the development of the technology was the standard SINTEF test diode. Many geometrical implementations were included, featuring variable numbers of guard-rings and field-plate
designs. Two different sets of pixels detectors were also included together with other test structures
for technology evaluation. Surface isolation was realized with P-spray and a total of 6 different
implantation doses where tested to understand their impact on the electrical characteristics of the
sensors and identify a dose that can provide a good isolation before and after irradiation. This work
will briefly describe the wafer layout, the fabrication process and will focus on the electrical characterization results, finally outlining the plans for irradiation tests. Conclusions will be drawn on the
status of the technology and the capability for future sensor production will be discussed.
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Kok, Angela; Koybasi, Ozhan; Povoli, Marco; Summanwar, Anand & Breivik, Lars
(2018).
A novel and simple method for fabrication of edgeless silicon radiation detectors.
Full text in Research Archive
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Povoli, Marco; Kok, Angela; Koybasi, Ozhan; Summanwar, Anand; Tran, Linh T. & Rosenfeld, Anatoly B.
(2017).
3D Silicon Sensors for radiation monitoring in space.
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The recent revival of space exploration implies an increased interest in space travels that are associated with many challenges and risks, mostly related to the ever-changing adverse space weather. Radiation of any types can be detrimental to both astronauts and the equipment on-board. The capability of monitoring radiation levels reliably in space is therefore becoming a critical aspect for space missions. Many existing radiation monitoring systems are bulky and require operation at high voltages and powers, for example, the Tissue Equivalent Proportional Counter (TEPC). Other systems are often fabricated using off-the-shelf components, including Si diodes for radiation detection, but lack the necessary radiation tolerance to ensure sensor survival throughout the entire mission.
The 3D silicon sensor technology provides unique solutions to the limitations of the existing technologies for radiation monitoring in space. This new technology was introduced to mitigate the effects of radiation damage in High Energy Physics Experiments. Through state-of-the-art micro-machining, 3D technology decouples the inter-electrode spacing from the thickness of the silicon sensor. Columnar electrodes are etched through the silicon bulk, allowing for inter-electrode spacing that is independent of the bulk thickness. The reduction in electrode spacing results in ultra-low operating voltage (<10 V), fast sensor response (< 1ns), and increased radiation hardness. 3D silicon pixel sensors were fabricated for the ATLAS experiment at CERN, and operation up to fluences in excess of 1x1016 neq/cm-2 was demonstrated. Design, fabrication, and testing of a novel 3D silicon sensors tailored to space applications and manufactured at SINTEF MiNaLab are here reported. Electrical characteristics and sensor response to radioactive sources will be presented. Further tests plans will be discussed together with a development plan aiming at a portable, real-time on-line micro-dosimeter for space applications realised in collaboration with the Centre for Medical Radiation Physics at the University of Wollongong, Australia.
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Kok, Angela & Povoli, Marco
(2016).
New technology allows radiology treatments to become more focused.
Full text in Research Archive
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A new technology, originally developed in 2012 to provide sensors that can tolerate extremely high radiation doses, has proven effective in particle therapy and has many advantages over x-ray photon therapy.
Marco Povoli, Angela Kok and a team of world-renowned medical physicists, sensor technologists and medical personnel formed the microscopic sensor developed at SINTEF in Trondheim, Norway. They partnered with the Centre for Medical Radiation Physicists at the University of Wollongong, Australia.
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Rosenfeld, Anatoly B.; Tran, Linh T.; Povoli, Marco; Kok, Angela & Summanwar, Anand
(2016).
Novel Trends in Medical Microdosimetry.
Full text in Research Archive
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Rosenfeld, Anatoly B.; Tran, Linh T.; Povoli, Marco & Kok, Angela
(2016).
Innovative Radiation Detectors for Particle Therapy.
Full text in Research Archive
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Rosenfeld, Anatoly B.; Tran, Linh T.; Povoli, Marco & Kok, Angela
(2016).
New Technologies in Semiconductor Medical Dosimetry.
Full text in Research Archive
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Benjaminsen, Christina; Povoli, Marco & Kok, Angela
(2016).
Microscopic sensor for more precise radiology treatments.
[Internet].
http://geminiresearchnews.com/2016/11/microscopic-sensor-pre.
Full text in Research Archive
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Povoli, Marco; Kok, Angela; Franconi, Laura; Rohne, O & Koybasi, Ozhan
(2015).
Status of single-sided 3D detector development at SINTEF.
Full text in Research Archive
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Published
Jan. 21, 2014 2:17 PM
- Last modified
Jan. 21, 2014 2:21 PM