Silicon Solid-state Detectors Research Articles

Development of a High-Efficiency Device for Thermal Neutron Detection Using a Sandwich of Two High-Purity 10B Enriched Layers.

The shortage of 3He, a crucial element widely used as a neutron converter in neutron detection applications, has sparked significant research efforts aimed at finding alternative materials, developing appropriate deposition methods, and exploring new detector architectures. This issue has required the exploration of novel approaches to address the challenges faced in neutron detection. Among the available conversion materials, 10B has emerged as one of the most promising choices due to its high neutron-capture cross-section and relatively high Q value. In our previous papers, we delved into the possibility of depositing neutron conversion layers based on 10B using Pulsed Laser Deposition (PLD). We investigated and evaluated the performance of these layers based on various factors, including deposition conditions, substrate properties, and film thickness. Moreover, we successfully developed and tested a device that employed a single conversion layer coupled with a silicon particle detector. In this current study, we present the development of a new device that showcases improved performance in terms of efficiency, sensitivity, and discrimination against γ background signals. The background signals can arise from the environment or be associated with the neutron field. To achieve these advancements, we considered a new detection geometry that incorporates the simultaneous use of two 10B conversion layers, each with a thickness of 1.5 μm, along with two solid-state silicon detectors. The primary objective of this design was to enhance the overall detection efficiency when compared to the single-layer geometry. By employing this novel setup, our results demonstrate a significant enhancement in the device's performance when exposed to a neutron flux from an Am-Be neutron source, emitting a flux of approximately 2.2 × 106 neutrons per second. Furthermore, we established a noteworthy agreement between the experimental data obtained and the simulation results.

Heavy Ion Energy Deposition and SEE Intercomparison Within the RADNEXT Irradiation Facility Network

RADNEXT is an EU-funded network of irradiation facilities and radiation effects experts aimed at increasing the quantity and quality of user access to accelerator infrastructure, and improving the diversity and harmonization across facilities. Along with the beam provision to worldwide radiation effects users, RADNEXT has an ambitious research program oriented at improving radiation effects testing, of which an example of a heavy ion facility inter-comparison at very different energy regimes is included in this work. In particular, energy deposition distributions in a silicon solid-state detector and the Single Event Upset (SEU) and Multiple Cell Upset (MCU) behaviour are compared amongst heavy ion beams of similar LET, but very different energies (i.e., from the more classical ~10 MeV/u regime up to several hundreds of MeV/u).

Microstructural and Micro-Chemical Evolutions in Irradiated UCO Fuel Kernels of AGR-1 and AGR-2 TRISO Fuel Particles

AGR-1 and AGR-2 tristructural-isotropic (TRISO) fuel particles were fabricated using slightly different fuel kernel chemical compositions, modified fabrication processes, different fuel kernel diameters, and changed 235U enrichments. Extensive microstructural and analytical characterizations were conducted to correlate those differences with the fuel kernels’ responses to neutron irradiations in terms of irradiated fuel microstructure, fission products’ chemical and physical states, and fission gas bubble evolutions. The studies used state-of-the-art transmission electron microscopy (TEM) equipped with energy-dispersive x-ray spectroscopy (EDS) via four silicon solid-state detectors with super sensitivity and rapid speed. The TEM specimens were prepared from selected AGR-1 and AGR-2 irradiated fuel kernels exposed to safety testing after irradiation. The particles were chosen in order to create representative irradiation conditions with fuel burnup in the range of 10.8 to 18.6% fissions per initial metal atom (FIMA) and time-average volume-average temperatures varying from 1070 to 1287°C. The 235U enrichment was 19.74 wt.% and 14.03 wt.% for the AGR-1 and AGR-2 fuel kernels, respectively. The TEM results showed significant microstructural reconstructions in the irradiated fuel kernels from both the AGR-1 and AGR-2 fuels. There are four major phases: fuel matrix of UO2 and UC, U2RuC2, and UMoC2—in the irradiated AGR-2 fuel kernel. Zr and Nd form a solid solution in the UC phase. The UMoC2 phase often features a detectable concentration of Tc. Pd was mainly found to be located in the buffer layer or associated with fission gas bubbles within the UMoC2 phase. EDS maps qualitatively show that rare-earth fission products (Nd et al.) preferentially reside in the UO2 phase. In contrast, in the irradiated AGR-1 fuel kernel, no U2RuC2 or UMoC2 precipitates were positively identified. Instead, there was a high number of rod-shaped precipitates enriched with Ru, Tc, Rh, and Pd observed in the fuel kernel center and edge zone. The differences in irradiated fuel kernel microstructural and micro-chemical evolution when comparing AGR-1 and AGR-2 TRISO fuel particles may result from a combination of irradiation temperature, fuel geometry, and chemical composition. However, irradiation temperature probably plays a more deterministic role. Limited electron energy-loss spectroscopy (EELS) characterizations of the AGR-2 fuel kernel show almost no carbon in the UO2 phase, but a small fraction of oxygen was detected in the UC/UMoC2 phase.

Thin silicon solid-state detectors for energetic particle measurements

Context. Silicon solid-state detectors are commonly used for measuring the specific ionization, dE∕dx, in instruments designed for identifying energetic nuclei using the dE∕dx versus total energy technique in space and in the laboratory. The energy threshold and species resolution of the technique strongly depend on the thickness and thickness uniformity of these detectors. Aims. Research has been carried out to develop processes for fabricating detectors that are thinner than 15 μm, that have a thickness uniformity better than 0.2 μm over cm2 areas, and that are rugged enough to survive the acoustic and vibration environments of a spacecraft launch. Methods. Silicon-on-insulator wafers that have a device layer of the desired detector thickness supported by a thick handle layer were used as starting material. Standard processing techniques were used to fabricate detectors on the device layer, and the underlying handle-layer material was etched away leaving a thin, uniform detector surrounded by a thick, supporting frame. Results. Detectors as thin as 12 μm were fabricated in two laboratories and successfully subjected to environmental and performance tests. Two detector designs were used in the High-energy Energetic Particles Instrument, which is part of the Integrated Science Investigation of the Sun instrument suite on NASA’s Parker Solar Probe spacecraft. These detectors have been performing well for more than two years in space. Conclusions. Thin silicon detectors in d E∕dx versus total energy instruments enable the identification of nuclei with energies down to ~1 MeV nuc−1. This research suggests that detectors at least a factor of two thinner should be achievable using this fabrication technique.

Integrating X-ray kV millimetric field dosimetry with a synthetic diamond detector into the treatment planning system commissioning of a preclinical irradiator.

Small animal irradiators are equipped with x-ray beams and cone collimators with millimeter dimensions to be used in preclinical research. The use of small fields in the kV energy range may require the application of energy-dependent, field size-dependent, or depth-dependent correction factors to the dosimetric data acquired for treatment planning system (TPS) commissioning purposes to obtain accurate dose values. Considering that these corrections are also detector dependent, the suitability of a synthetic single-crystal diamond detector for small-field relative dosimetry in a preclinical irradiator (220-kVp) was evaluated to avoid the necessity of applying correction factors during TPS commissioning. The detector response was assessed during the transition for field sizes ranging from 20×20mm2 to 3×3mm2 , using the small animal radiation research platform (SARRP). The percentage depth dose distributions (PDDs), lateral profiles and output factors (OFs) were measured. The PDDs for the synthetic diamond detector were compared to the distributions acquired using a small-volume microchamber (0.016cm3 ) and with Monte Carlo calculations using the MC3D in-house software package. The profiles and OFs were compared to the data from a silicon solid-state detector and to radiochromic film data provided by the manufacturer; for the OF determination, measurements made using a microchamber were added for comparison. The performance of several detectors used as references was previously validated for relative dosimetry in preclinical irradiators. A commercial TPS was commissioned for the factor-based algorithm, using the data acquired with the diamond detector, and no additional correction factors were applied. To verify the performance of the TPS and the accuracy of the dosimetric methodology, radiochromic film irradiation in water was conducted, and two-dimensional (2D) dose distributions in the coronal and axial planes were compared under different gamma criteria. Compared with the microchamber and MC3D distributions, the agreement of the PDDs using the synthetic diamond detector was better than 2%. The profile data exhibited very good agreement compared with the data from the silicon detector, with an average and a maximum difference of 0.31 and 0.39mm in the penumbras, respectively. Compared with the data from the radiochromic film, the average and maximum differences were equal to 0.77 and 0.89mm, respectively. Very good agreement, within 1%, was obtained between the OFs measured with the synthetic diamond detector and the radiochromic film, compared only for the cone collimators. The validation of the TPS commissioning using gamma criteria compared to film showed an average passing rate of 100% and 93.2% with a global gamma criterion of 1mm/3% for the coronal and axial planes, respectively, including the 3×3mm2 field size and penumbra regions. Synthetic diamond is a suitable detector for the complete relative dosimetry of small x-ray fields. The commissioning of the TPS with its own beam dosimetric data exhibited encouraging results even in a 3×3mm2 field and penumbra region. This methodology allows for the prediction of 2D dose distributions with an accuracy in water ranging from 3 to 5% compared to the 2D distribution from film dosimetry.

Optimization of energy and directional response of a small 4π silicon dosemeter for quality control of CT/CBCT-units – A 3D CAD, Monte-Carlo, AM approach

A 4π radiation dosemeter for use in medical radiology was designed. It is based on a solid state silicon detector, a sensor wafer, a flex card, a 3D plastic holder and a spherical stainless steel filter with a distribution of holes around the detector. The detector is attached to the wafer using only low Z material. To achieve an energy and directional response which is as uniform as possible for various radiation qualities and beam directions, the filter was designed using a series of Monte Carlo calculations. The energy filter and its hole pattern were created using Additive Manufacturing (AM) in the form of metal 3D printing. The functionality of the dosemeter was designed to fulfill the quality criteria of a combined energy and angular dependence of less than 5% for the IEC beam qualities RQR and RQT in the range of 65–145 kV. This is a major improvement to the existing solutions that may need software corrections to be used for the same beam quality range.

A C-14 beam monitor using silicon solid state sensor for cultural heritage

We report the design and preliminary test results of a 14 C beam monitor developed for the online monitoring for radiocarbon dating. The challenge of the INFN CHNet-Lilliput experiment is to measure the amount of carbon in very small samples (down to a few micro-grams) with a very low concentration of radiocarbon. For this purpose, a new dedicated beam monitor for 14 C ions (Energy ≃ 10 MeV) uses a silicon solid state detector made of 4 independent sectors, active area 50 × 50 mm 2 and 300 μ m thickness. The detector was preliminary tested in the INFN Laboratory of Bari and then installed on the final part of the Accelerator Mass Spectrometry (AMS) beam line at the INFN-LABEC Laboratory of Firenze (Italy) where sample measurements for radiocarbon dating are performed since 2004. • Preliminary test results of a 14C beam monitor for the online monitoring for radiocarbon dating. • The challenge of the INFN CHNet-Lilliput experiment is to measure the amount of carbon in very small samples. • A new dedicated beam monitor for 14C ions (Energy ∼ 10 MeV) uses a silicon solid state detector made of 4 independent sectors ( 300 μ m thickness). • The detector was tested in the INFN Laboratory of Bari and then installed at the INFN-LABEC (Firenze).

The extremely high-energy electron experiment (XEP) onboard the Arase (ERG) satellite

The extremely high-energy electron experiment (XEP) onboard the Arase (ERG) satellite is designed to measure high-energy electrons in the Earth’s radiation belts. The XEP was developed by taking advantage of our technical heritage of high-energy particle detectors that are onboard Earth observation satellites of the Japan Aerospace Exploration Agency (JAXA) as the radiation monitor. The main target of the XEP is to precisely measure variations of relativistic electrons in the outer radiation belt even during magnetic storms. The measurement is scientifically required to address physical mechanisms of electron acceleration and loss. The XEP consists of five solid-state silicon detectors (SSDs) and a single-crystal inorganic scintillator of cerium-doped gadolinium orthosilicate (GSO) to measure electrons in the energy range of 0.4–20 MeV and has a 20° single field of view (FOV). It is also equipped with a plastic scintillator that surrounds the GSO scintillator to prevent particles from entering the detectors from outside the FOV. The XEP has started its observation of relativistic electrons and has successfully observed dynamic variations of relativistic electron fluxes in the outer radiation belt during magnetic storms. This paper describes the instrumentation of the XEP and presents an example of initial observation results.

Neutron detection devices with 6LiF converter layers

The demand for new thermal neutron detectors as an alternative to 3He tubes in research, industrial, safety and homeland security applications, is growing. These needs have triggered research and development activities about new generations of thermal neutron detectors, characterized by reasonable efficiency and gamma rejection comparable to 3He tubes. In this paper we show the state of art of a promising lowcost technique, based on commercial solid state silicon detectors coupled with thin neutron converter layers of 6LiF deposited onto carbon fiber substrates. Several configurations were studied with the GEANT4 simulation code, and then calibrated at the PTB Thermal Neutron Calibration Facility. The results show that the measured detection efficiency is well reproduced by the simulations, therefore validating the simulation tool in view of new designs. These neutron detectors have also been tested at neutron beam facilities like ISIS (Rutherford Appleton Laboratory, UK) and n_TOF (CERN) where a few samples are already in operation for beam flux and 2D profile measurements. Forthcoming applications are foreseen for the online monitoring of spent nuclear fuel casks in interim storage sites.

Absolute efficiency calibration of 6LiF-based solid state thermal neutron detectors

The demand for new thermal neutron detectors as an alternative to 3He tubes in research, industrial, safety and homeland security applications, is growing. These needs have triggered research and development activities about new generations of thermal neutron detectors, characterized by reasonable efficiency and gamma rejection comparable to 3He tubes. In this paper we show the state of the art of a promising low-cost technique, based on commercial solid state silicon detectors coupled with thin neutron converter layers of 6LiF deposited onto carbon fiber substrates. A few configurations were studied with the GEANT4 simulation code, and the intrinsic efficiency of the corresponding detectors was calibrated at the PTB Thermal Neutron Calibration Facility. The results show that the measured intrinsic detection efficiency is well reproduced by the simulations, therefore validating the simulation tool in view of new designs. These neutron detectors have also been tested at neutron beam facilities like ISIS (Rutherford Appleton Laboratory, UK) and n_TOF (CERN) where a few samples are already in operation for beam flux and 2D profile measurements. Forthcoming applications are foreseen for the online monitoring of spent nuclear fuel casks in interim storage sites.

Radiation dose-dependent risk on individuals due to ingestion of uranium and radon concentration in drinking water samples of four districts of Haryana, India

ABSTRACTUranium gets into drinking water when the minerals containing uranium are dissolved in groundwater. Uranium and radon concentrations have been measured in drinking water samples from different water sources such as hand pumps, tube wells and bore wells at different depths from various locations of four districts (Jind, Rohtak, Panipat and Sonipat) of Haryana, India, using the LED flourimetry technique and RAD7, electronic silicon solid state detector. The uranium (238U) and radon (222Rn) concentrations in water samples have been found to vary from 1.07 to 40.25 µg L−1 with an average of 17.91 µg L−1 and 16.06 ± 0.97 to 57.35 ± 1.28 Bq L−1 with an average of 32.98 ± 2.45 Bq L−1, respectively. The observed value of radon concentration in 43 samples exceeded the recommended limits of 11 Bq L−1 (USEPA) and all the values are within the European Commission recommended limit of 100 Bq L−1. The average value of uranium concentration is observed to be within the safe limit recommended by World Health Organization (WHO) and Atomic Energy Regulatory Board. The annual effective dose has also been measured in all the water samples and is found to be below the prescribed dose limit of 100 µSv y−1 recommended by WHO. Risk assessment of uranium in water is also calculated using life time cancer risk, life time average daily dose and hazard quotient. The high uranium concentration observed in certain areas is due to interaction of ground water with the soil formation of this region and the local subsurface geology of the region.

Study of silicon+6LiF thermal neutron detectors: GEANT4 simulations versus real data

Research and development on alternative thermal neutron detection technologies and methods are nowadays needed as a possible replacement of 3He-based ones. Commercial solid state silicon detectors, coupled with neutron converter layers containing 6Li, have been proved to represent a viable solution for several applications as present in the literature. In order to better understand the detailed operation and the response and efficiency of such detectors, a series of dedicated GEANT4 simulations were performed and compared with real data collected in a few different configurations. The results show an excellent agreement between data and simulations, indicating that the behavior of the detector is fully understood.

A combined segmented anode gas ionization chamber and time-of-flight detector for heavy ion elastic recoil detection analysis.

A dedicated detector system for heavy ion elastic recoil detection analysis at the Tandem Laboratory of Uppsala University is presented. Benefits of combining a time-of-flight measurement with a segmented anode gas ionization chamber are demonstrated. The capability of ion species identification is improved with the present system, compared to that obtained when using a single solid state silicon detector for the full ion energy signal. The system enables separation of light elements, up to Neon, based on atomic number while signals from heavy elements such as molybdenum and tungsten are separated based on mass, to a sample depth on the order of 1 μm. The performance of the system is discussed and a selection of material analysis applications is given. Plasma-facing materials from fusion experiments, in particular metal mirrors, are used as a main example for the discussion. Marker experiments using nitrogen-15 or oxygen-18 are specific cases for which the described improved species separation and sensitivity are required. Resilience to radiation damage and significantly improved energy resolution for heavy elements at low energies are additional benefits of the gas ionization chamber over a solid state detector based system.

Characterization of the silicon+6LiF thermal neutron detection technique

The worldwide need to replace 3He for neutron detection has triggered research and development on new technologies and methods. A promising one is based on commercial solid state silicon detectors coupled with thin neutron converter layers containing 6Li. After proving the feasibility of this technique, we characterized the behavior of such a detector with different converter layer thicknesses. In this paper we also disentangle other contributions to the overall spectrum shape observed with this kind of detector, proving that its detection efficiency can be made reasonably high and that the gamma/neutron discrimination capability is comparable to that of 3He tubes.

Risk assessment of exposure to radon concentration and heavy metal analysis in drinking water samples in some areas of Jammu & Kashmir, India

Radon concentration was measured in drinking water samples in some areas of Jammu & Kashmir, India, using RAD 7, an electronic solid state silicon detector. The observed values of radon concentration in some samples exceed the safe limit as recommended by the US Environmental Protection Agency (USEPA). These samples were also analyzed for concentration of certain heavy elements like As, Pb, Zn, Cu, Hg, Ni, and Cd using inductively coupled plasma atomic emission spectrometer (ICP-AES). The study was undertaken from the health hazard point of view.

XEDS in the AEM: Has Everything Thing That Can be Invented, Been Invented?

There is a fairly old apocryphal quotation stating : “Everything that can be invented has been invented.” [1] attributed at one time to Charles H. Duell of the US Patent office in 1899. We all realize this is an absurd statement, and it is well documented that Duell actually said something quite different and urged the US Congress to encourage the advancement of science as well as to improve the patent system [2,3]. This does however bring to focus a salient point concerning x-ray spectroscopy, as it relates to analytical electron microscopy. For many years instrument developers have concentrated upon advances in electron-optics, with justifiable and demonstrated improvements in imaging and probe forming systems. Aberration correctors, high sensitivity imaging detectors and electron spectrometry systems abound [4] , however, there are only a few seminal events which mark evolutionary advances in x-ray spectrometry. Arguably we can list the foremost of these as: the invention of electron microprobe analysis (EMPA) by Castaing [5], the invention of the Lithium Drifted Silicon (Si(Li) solid state detector [6], the development of the first AEM (EMMA-4) [7] and the development of the Silicon Drift Detector (SDD)[8]. While these are all key events which mark the onset of major advances in our ability to perform microanalysis, by comparison they represent only a fraction of the investment in resources compared to the electron optical developments. A very large fraction of the instrumentation found in characterization facilities worldwide has ancilliary x-ray analysis subsystems. The majority of these ancilliary x-ray spectrometry systems have been interfaced to an electron optical column in the simplest possible configuration and although they are at times considered routine, this does not mean that we have achieved all that these resources can provide, nor does it mean that we have addressed fully all their methodological intricacies and/or potentials.

Time-of-flight ERD with a 200 mm2 Si3N4 window gas ionization chamber energy detector

Low energy heavy ion elastic recoil detection work has been carried out in Jyväskylä since 2009 using home made timing detectors, a silicon energy detector and a timestamping data acquisition setup forming a time-of-flight–energy telescope. In order to improve the mass resolution of the setup a new energy detector was designed to replace the silicon solid state detector, which suffered from radiation damage and had poor resolution for heavy recoils.In this paper the construction and operation of an isobutane filled gas ionization chamber with a 14×14mm2 100nm thick silicon nitride window are described. In addition to greatly improved energy resolution for heavy ions, the detector is also able to detect hydrogen recoils simultaneously in the energy range of 100–1000keV. Additionally the detector has position sensitivity by means of timing measurement, which can be performed without compromising the performance of the detector in any other way. The achieved position sensitivity improves the depth resolution near the surface.

Electron and proton beam testing of pixelated solid state detectors

The biasing of guard rings in pixelated ion implanted silicon solid state detectors is often given little analysis as to the potential detrimental effects associated with capacitive coupling of the response of the pixel element to the guard ring and vise versa. This has been demonstrated and illustrates the importance of using beam testing to measure the angular response of particle instruments. We describe herein the development cycle of the Fixed Sensor Head (FSH) instrument, an imaging electron spectrometer that will be flown on the US Air Force's Demonstration and Science eXperiment (DSX) mission. During its construction, the FSH was tested using particle beams many times and each test yielded an important result that contributed to the design of the instrument before being delivered in August 2010.After several lower energy (<30keV) beam calibration tests at Hanscom Air Force Base demonstrated that the FSH was performing very well, a final, higher energy (150keV<E<1MeV) beam test at the Goddard Space Flight Center was almost skipped due to budget and scheduling constraints. This final test illuminated a major problem with the biasing of a detector guard ring that would have been difficult if not impossible to track down on orbit. The problem was easily fixed, but serves to highlight the importance of biasing of guard rings properly, and the necessity of testing instruments across the entire range of possible stimuli that they may encounter.

Measurement of the sensitive profile in a solid state silicon detector, irradiated by X-rays

A newly constructed solid state silicon dose profile detector is characterized concerning its sensitive profile. The use of the MEDIPIX2 sensor system displays an excellent method to align an image of an X-ray slit to a sample under test. The scanning from front to reverse side of the detector, show a decrease in sensitivity of 20%, which indicates a minority charge carrier lifetime of 0.18 ms and a diffusion length of 460 μm. The influence of diced edges results in a volumetric efficiency of 59%, an active volume of 1.2 mm2 of total 2.1 mm2.

The Relativistic Electron-Proton Telescope (REPT) Instrument on Board the Radiation Belt Storm Probes (RBSP) Spacecraft: Characterization of Earth’s Radiation Belt High-Energy Particle Populations

Particle acceleration and loss in the million electron Volt (MeV) energy range (and above) is the least understood aspect of radiation belt science. In order to measure cleanly and separately both the energetic electron and energetic proton components, there is a need for a carefully designed detector system. The Relativistic Electron-Proton Telescope (REPT) on board the Radiation Belt Storm Probe (RBSP) pair of spacecraft consists of a stack of high-performance silicon solid-state detectors in a telescope configuration, a collimation aperture, and a thick case surrounding the detector stack to shield the sensors from penetrating radiation and bremsstrahlung. The instrument points perpendicular to the spin axis of the spacecraft and measures high-energy electrons (up to ∼20 MeV) with excellent sensitivity and also measures magnetospheric and solar protons to energies well above E=100 MeV. The instrument has a large geometric factor (g=0.2 cm2 sr) to get reasonable count rates (above background) at the higher energies and yet will not saturate at the lower energy ranges. There must be fast enough electronics to avert undue dead-time limitations and chance coincidence effects. The key goal for the REPT design is to measure the directional electron intensities (in the range 10−2–106 particles/cm2 s sr MeV) and energy spectra (ΔE/E∼25 %) throughout the slot and outer radiation belt region. Present simulations and detailed laboratory calibrations show that an excellent design has been attained for the RBSP needs. We describe the engineering design, operational approaches, science objectives, and planned data products for REPT.