Search

In this paper, we describe an experiment aimed to measure the physical observables, which can be used for the assessment of the radiation hardness of commercially available silicon photo diodes commonly used as nuclear detectors in particle accelerator laboratories. The experiment adopted the methodology developed during the International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP No. F11016) "Utilization of Ion Accelerators for Studying and Modelling Ion Induced Radiation Defects in Semiconductors and Insulators". This methodology is based on the selective irradiation of micrometer-sized regions with different fluences of MeV ions using an ion microbeam and on the measurement of the charge collection efficiency (CCE) degradation by Ion Beam Induced Charge (IBIC) microscopy performed in full depletion condition, using different probing ions. The IBIC results are analyzed through a theoretical approach based on the Shockley-Read-Hall model for the free carrier recombination in the presence of ion-induced deep traps. This interpretative model allows the evaluation of the material radiation hardness in terms of recombination parameters for both electrons and holes. The device under study in this experiment was a commercial p-i-n photodiode, which was initially characterized by i) standard electronic characterization techniques to determine its doping and ii) the Angle-Resolved IBIC to evaluate its effective entrance window. Nine regions of (100 × 100) µm2 were irradiated with 11.25 MeV He ions up to a maximum fluence of 3·1012 ions/cm2. The CCE degradation was measured by the IBIC technique using 11.25 MeV He and 1.4 MeV He as probing ions. The model presented here proved to be effective for fitting the experimental data. The fitting parameters correspond to the recombination coefficients, which are the key parameters for the characterization of the effects of radiation damage in semiconductors. [ABSTRACT FROM AUTHOR]

The electrical properties of photodiodes based on silicon-on-sapphire structures are investigated theoretically and experimentally. It is shown that they are no worse than silicon diodes in terms of their basic parameters, while their radiation hardness is higher by an order of magnitude than that of similar diodes based on bulk silicon. [ABSTRACT FROM AUTHOR]

Presents a study to compare effects of electron and proton irradiation on n+-p-p+ silicon diodes. Methodology used to conduct study; Indication of findings; Discussion on results.

Investigates the behavior of radiation-induced carbon-related defects in high-resistivity silicon detectors. Determination of the kinetic parameters of the process; Examination of the effect of variations in the fabrication technology of the detector on the defect properties; Details of experimental techniques used.

Presents a study which examined the effect of radiation induced defects on the capacitance of silicon detectors. Theoretical considerations; Experimental details; Results and discussion.

Silicon-diode-based detectors are commonly used for the dosimetry of small radiotherapy beams due to their relatively small volumes and high sensitivity to ionizing radiation. Nevertheless, silicon-diode-based detectors tend to over-respond in small fields because of their high density relative to water. For that reason, detector-specific beam correction factors () have been recommended not only to correct the total scatter factors but also to correct the tissue maximum and off-axis ratios. However, the application of to in-depth and off-axis locations has not been studied. The goal of this work is to address the impact of the correction factors on the calculated dose distribution in static non-conventional photon beams (specifically, in stereotactic radiosurgery with circular collimators). To achieve this goal, the total scatter factors, tissue maximum, and off-axis ratios were measured with a stereotactic field diode for 4.0-, 10.0-, and 20.0-mm circular collimators. The irradiation was performed with a Novalis® linear accelerator using a 6-MV photon beam. The detector-specific correction factors were calculated and applied to the experimental dosimetry data for in-depth and off-axis locations. The corrected and uncorrected dosimetry data were used to commission a treatment planning system for radiosurgery planning. Various plans were calculated with simulated lesions using the uncorrected and corrected dosimetry. The resulting dose calculations were compared using the gamma index test with several criteria. The results of this work presented important conclusions for the use of detector-specific beam correction factors ( in a treatment planning system. The use of for total scatter factors has an important impact on monitor unit calculation. On the contrary, the use of for tissue-maximum and off-axis ratios has not an important impact on the dose distribution calculation by the treatment planning system. This conclusion is only valid for the combination of treatment planning system, detector, and correction factors used in this work; however, this technique can be applied to other treatment planning systems, detectors, and correction factors. [ABSTRACT FROM AUTHOR]

The experimental results and calculations of the efficiency of the energy conversion of Ni-63 β-radiation sources to electricity using silicon p-i-n diodes are presented. All calculations are performed taking into account the energy distribution of β-electrons. An expression for the converter open-circuit voltage is derived taking into account the distribution of high-energy electrons in the space-charge region of the p-i-n diode. Ways of optimizing the converter parameters by improving the technology of diodes and optimizing the emitter active layer and i-region thicknesses of the semiconductor converter are shown. The distribution of the conversion losses to the source and radiation detector and the losses to high-energy electron entry into the semiconductor is calculated. Experimental values of the conversion efficiency of 0.4-0.7% are in good agreement with the calculated parameters. [ABSTRACT FROM AUTHOR]

A novel bimodal radiation imager (X-ray and thermal neutron) was designed using a fin–trench microstructured silicon diode backfilled with 6LiF, then bonded to a Timepix pixelated imaging ASIC (X-MSNDs). A simulation scheme had been devised which combined finite element analysis and discrete charge carrier transport to simulate the imaging characteristics of such arbitrarily doped 3D silicon Timepix sensors. However, the precise dopant profile of the deeply etched silicon surface that forms the X-MSND diode junction is difficult to measure with conventional optical or chemical staining means. A set of boundary conditions was instead derived from simple particle transport simulations and the constant-surface-concentration silicon diffusion model. Finite element analysis of the microstructured devices using COMSOL Multiphysics and this derived boundary condition revealed that the fin region of the sensors was generally un-depleted under the maximum 300 V reverse bias, and the calculated electric field along the thickness of the sensor in the microstructured region is negligible. Charge carrier transport simulations using Allpix 2 predicted charge carrier motion in the fin region is dominated by slow diffusion along the fin dimension, resulting in mean charge drift times of 1000 ns to collect 95% of charge carriers. Neutron transport simulations indicated that single neutron detection events resulted in highly elongated pixel clusters, typically 1-pixel wide by 6-pixels along the fin dimension. Measured data collected from KSU fabricated X-MSND imagers matched these simulation results. [ABSTRACT FROM AUTHOR]

This paper reports control of switching characteristics of silicon-based semiconductor diode using electron beam produced using linear accelerator. Conventionally, p-n junction chips of diode are exposed to gamma rays from a radioactive source or electron beam from a microtron, depending upon the required level of correction. High energy linear accelerators featuring simultaneous exposure of multiple chips are recent advancements in radiation technology. The paper presents the results of the radiation process using a 10 MeV linear accelerator as applied in industrial manufacturing of a high voltage diode (2600 V). The achieved values of reverse recovery time were found to be within the design limits. The suitability of the new process was verified by constructing the trade-off curve between the switching and conduction parameters of the diode for the complete range using large number of experimental samples. The paper summarizes the advantages of the new process over the conventional methods specifically with reference to industrial requirements. The developed process has been successfully implemented in semiconductor manufacturing. [ABSTRACT FROM AUTHOR]

Abstract: The CMS silicon strip tracker is the largest detector of its kind. It is expected to operate at the LHC for more than 10 years. In order to quantify aging effects, it is important to keep track of the evolution of fundamental detector properties under radiation and thermal fluctuations. In these proceedings we present our methods measuring the evolution of our sensors full depletion voltage and leakage current. We will also present a comparison between the change in detector properties as seen so far with the theoretical predictions. As an outlook we introduce our simulations of the evolution of the detector properties in the next 10 years. [Copyright &y& Elsevier]

Abstract: For the high-luminosity phase of LHC (Large Hadron Collider) at CERN a campaign was started in the CMS (Compact Muon Solenoid) experiment to investigate different radiation hard silicon detectors. Therefore 6in. silicon wafers were ordered to answer various questions regarding for example the radiation tolerance and the annealing behavior of different sensor material. The testing variety includes sensor versions n-in-p and p-in-n in thicknesses from to . In terms of sensor material the difference between floating zone, magnetic Czochralski and epitaxial grown silicon is investigated. For the n-in-p sensors, the different isolation technologies, p-stop and p-spray, are tested. The design of the wafer contains test structures, diodes, mini-sensors, long and very short strip sensors, real pixel sensors and double metal routing variants. The irradiation is done with mixed fluences of protons and neutrons which represent the rates of integrated hadrons that are expected in the CMS tracker after the LHC upgrade. This paper presents an overview of results from measurements of non-irradiated test structures with different technologies and also the results after irradiation. [Copyright &y& Elsevier]

Abstract: We have developed a prototype of a survey meter combining a CVD diamond detector and silicon detectors to appropriately take temporal measurements of γ-ray radiations over a wide range of the dose rates and to measure high accumulated doses of γ-ray radiations. In order to carry out this, at first, we have studied the radiation hardness of diamond detectors suitably fabricated with high-quality single-crystalline CVD diamond films to confirm that such CVD diamond detectors have greatly superior radiation hardness, compared with commercially available silicon detectors. It is evidenced that the performance of the CVD diamond detector did not significantly change even after heavy γ-ray irradiation of 0.7 MGy while the silicon detectors have a remarkable increase in the dark current, a detection peak shift to the low energy side, and a decrease in detection counts for 5.486-MeV α particles. Due to a size limitation of the CVD diamond detector, such a CVD diamond detector was combined with six commercially available silicon detectors to fabricate a survey meter which can appropriately work under severe irradiation conditions, or, at accumulated doses larger than at least 0.5 MGy and which can cover a wide range of the dose rates from 1 μGy/h to at least 1 kGy/h. The prototype survey meter had a practically useful linearity in this dose rate range. Thus, we have confirmed that such a diamond-Si combined survey meter can be put into practical use. [Copyright &y& Elsevier]

Abstract: Silicon detectors in 3D technology are a candidate for applications in environments requiring an extreme radiation hardness, as in the innermost layers of the detectors at the proposed High-Luminosity LHC. In 3D detectors, the electrodes are made of columns etched into the silicon perpendicular to the surface. This leads to higher electric fields, a smaller depletion voltage and a reduced trapping probability of the charge carriers compared to standard planar detectors. In this article, the signal and the noise of irradiated n-in-p and p-in-n 3D silicon strip detectors are compared. The devices under test have been irradiated up to a fluence of 2×1016 1MeV neutron equivalent particles per square centimetre , which corresponds to the fluence expected for the inner pixel detector layers at the High-Luminosity LHC. A relative charge collection efficiency of approximately 70% was obtained even after the highest irradiation fluence with both detector types. The influence of different temperatures on the signal and the noise is investigated and results of annealing measurements are reported. [Copyright &y& Elsevier]

Abstract: The development of edgeless Si detectors was stimulated by the tasks of the total pp cross-section study in the TOTEM experiment at the Large Hadron Collider at CERN. For this, the dead region at the detector diced side should be reduced below 50μm. This requirement is successfully realized in edgeless Si detectors with current terminating structure (CTS), which are now operating at LHC. The development of the experiment and future LHC upgrade need the elaboration of radiation hard version of edgeless Si detectors. The current investigation represents an extension in understanding on edgeless detectors operation and development of a new issue – edgeless detectors with CTS on p-type Si. [Copyright &y& Elsevier]

Abstract: A new international-patent-pending (PCT/US2010/52887) detector type, named here as 3D-Trench electrode Si detectors, is proposed in this work. In this new 3D electrode configuration, one or both types of electrodes are etched as trenches deep into the Si (fully penetrating with SOI or supporting wafer, or non-fully penetrating into 50–90% of the thickness), instead of columns as in the conventional (“standard”) 3D electrode Si detectors. With trench etched electrodes, the electric field in the new 3D electrode detectors are well defined without low or zero field regions. Except near both surfaces of the detector, the electric field in the concentric type 3D-Trench electrode Si detectors is nearly radial with little or no angular dependence in the circular and hexangular (concentric-type) pixel cell geometries. In the case of parallel plate 3D trench pixels, the field is nearly linear (like the planar 2D electrode detectors), with simple and well-defined boundary conditions. Since each pixel cell in a 3D-Trench electrode detector is isolated from others by highly doped trenches, it is an electrically independent cell. Therefore, an alternative name “Independent Coaxial Detector Array”, or ICDA, is assigned to an array of 3D-Trench electrode detectors. The electric field in the detector can be reduced by a factor of nearly 10 with an optimal 3D-Trench configuration where the junction is on the surrounding trench side. The full depletion voltage in this optimal configuration can be up to 7 times less than that of a conventional 3D detector, and even a factor of two less than that of a 2D planar detector with a thickness the same as the electrode spacing in the 3D-Trench electrode detector. In the case of non-fully penetrating trench electrodes, the processing is true one-sided with backside being unprocessed. The charge loss due to the dead space associated with the trenches is insignificant as compared to that due to radiation-induced trapping in sLHC environment. Since the large electrode spacing (up to 500μm) can be realized in the 3D-Trench electrode detector due to their advantage of greatly reduced full depletion voltage, detectors with large pixel cells (therefore small dead volume) can be made for applications in photon science (e.g. X-ray). [Copyright &y& Elsevier]

Abstract: The CMS silicon strip tracker is the largest detector of its kind. It is expected to operate at the LHC for more than 10 years. In order to quantify aging effects, it is important to keep track of the evolution of fundamental detector properties under radiation and thermal fluctuations. Our aim is to define monitoring procedures to determine the characteristics regularly. In this paper we focus on the silicon sensor''s full depletion voltage. We present the first results obtained with two different methods: a standard one with signal from particles and a newly developed approach based on noise. In addition we compare our output with the measurements performed during the construction. [Copyright &y& Elsevier]

Abstract: In current particle physics experiments, silicon strip detectors are widely used as part of the inner tracking layers. A foreseeable large-scale application for such detectors consists of the luminosity upgrade of the Large Hadron Collider (LHC), the super-LHC or sLHC, where silicon detectors with extreme radiation hardness are required. The mission statement of the CERN RD50 Collaboration is the development of radiation-hard semiconductor devices for very high luminosity colliders. As a consequence, the aim of the R&D programme presented in this article is to develop silicon particle detectors able to operate at sLHC conditions. Research has progressed in different areas, such as defect characterisation, defect engineering and full detector systems. Recent results from these areas will be presented. This includes in particular an improved understanding of the macroscopic changes of the effective doping concentration based on identification of the individual microscopic defects, results from irradiation with a mix of different particle types as expected for the sLHC, and the observation of charge multiplication effects in heavily irradiated detectors at very high bias voltages. [Copyright &y& Elsevier]

Abstract: In this work, a Si(Li) detector was used to analyze mammographic X-ray spectra produced by an industrial equipment with Molybdenum (Mo) target, operating at constant tube potentials between 20 and 35kV. Filters of Mo and Al of suitable thickness were added to the tube exit, in order to reproduce the radiation qualities of an X-ray mammographic equipment, as recommended by the International Electrotechnical Commission (IEC 61267) and the Physikalisch-Technischen Bundesanstalt (PTB). A detailed evaluation of the detector response functions was made using Monte Carlo simulations. The validity of this method was tested through comparisons with the experimental spectra of radioactive sources. The results showed that the Si(Li) detector exhibits good response function in low energy (between 5 and 20keV). The measured X-ray spectra for a Mo filtration (0.03mm thickness), corrected using the response functions, show a good agreement with the reference clinical spectra. The results of this work also show that both the radiation qualities implemented and the spectra shape are consistent with that obtained for mammographic X-ray beams, and they can be applied to calibration of the mammography measurements instruments (e.g. ionization chambers and dosimeters). [Copyright &y& Elsevier]

While the Large Hadron Collider (LHC) began taking data in 2009, scenarios for a machine upgrade to achieve a much higher luminosity are being developed. In the current planning, it is foreseen to increase the luminosity of the LHC at CERN around 2018. As radiation damage scales with integrated luminosity, the particle physics experiments will need to be equipped with a new generation of radiation hard detectors. This article reports on the status of the R&D projects on radiation hard silicon strips detectors for particle physics, linked to the Large Hadron Collider Upgrade, super-LHC (sLHC) of the ATLAS microstrip detector. The primary focus of this report is on measuring the radiation hardness of the silicon materials and the detectors under study. This involves designing silicon detectors, irradiating them to the sLHC radiation levels and studying their performance as particle detectors. The most promising silicon detector for the different radiation levels in the different regions of the ATLAS microstrip detector will be presented. Important challenges related to engineering layout, powering, cooling and reading out a very large strip detector are presented. Ideas on possible schemes for the layout and support mechanics will be shown. [ABSTRACT FROM AUTHOR]

The fabrication of 3D detectors which requires bulk micromachining of columnar electrodes has been realized with advancements in MEMS technology. Since the fabrication of the first 3D prototype in Stanford Nanofabrication Facility in 1997, a significant effort has been put forth to transfer the 3D detector technology to large scale manufacturing for future high luminosity collider experiments, in which the radiation hardness will be the primary concern, and other applications such as medical imaging and X-ray imaging for molecular biology. First, alternative 3D structures, single type column (STC) and double-side double type column (DDTC) 3D detectors, were produced at FBK-irst (Trento, Italy) and CNM-Barcelona (Spain), and assessed thoroughly to improve the production technology towards the standard full-3D detectors. The 3D collaboration has been extended to include SINTEF (Norway), which is committed to small to medium scale production of active edge full-3D silicon sensors. This paper focuses on p-type 3D detectors compatible with the CMS pixel front end electronics from the second run of fabrication at SINTEF clean room facilities. The sensors that passed the wafer level electrical characterization have been bump-bonded at IZM (Germany), assembled into modules and wire-bonded for functional characterization at Purdue University. We report the leakage current characteristics, bump-bond quality, threshold, noise, and gain measurement results of these 3D modules as well as the preliminary beam test data taken at Fermi National Accelerator Laboratory. [ABSTRACT FROM AUTHOR]

Abstract: Human will be sooner or later return to the moon and will eventually travel to the planets near Earth. Space radiation hazards are an important concern for human space flight in deep space where galactic cosmic rays (GCR) and solar energetic particles are dominated and radiation is much stronger than that in LEO (Low Earth Orbit) because in deep space there is no magnetosphere to screen charged particle and no big planet nearby to shadow the spacecraft. Research indicates that the impact of particle radiation on humans depends strongly on the particles'' linear energy transfer (LET) and the radiation risk is dominated by high LET radiation. Therefore, radiation research on high LET should be emphasized and conducted systematically so as to make radiation risk as low as reasonably achievable (ALARA) for astronauts. Radiation around the moon can be measured with silicon detectors and/or CR-39 plastic nuclear track detectors (PNTDs). At present stage the silicon detectors are one of the preferred active dosimeters which are sensitive to all LET and CR-39 detectors are the preferred passive dosimeters which are sensitive to high LET (≥5keV/μm water). CR-39 PNTDs can be used as personal dosimeters for astronauts. Both the LET spectrum and the charge spectrum for charged particles in space can be measured with silicon detectors and CR-39 detectors. Calibrations for a detector system combined with the silicon detectors CRaTER (Cosmic Rays Telescope for the Effects of Radiation) from Boston University and Massachusetts Institute of Technology, and the CR-39 PNTDs from JSC (Johnson Space Center) – SRAG (Space Radiation Analysis Group) were conducted by exposing the detector system to the accelerator generated protons and heavy ions. US space mission for the radiation measurement around the moon using CRaTER was carried out in 2009. Results obtained from the calibration exposures indicate an excellent agreement between LET spectrum and charge spectrum measured with CR-39 detectors and simulated with PHITS (Particle and Heavy Ion Transport System). This paper introduces the LET spectrum method and charge spectrum method using CR-39 PNTDs and the Monte Carlo simulation method for CR-39 detectors, presents and compares the results measured with CR-39 PNTDs and simulated for CR-39 detectors exposed to heavy irons (600MeV/n) in BNL (Brookhaven National Laboratory) in front and behind the CRaTER. [Copyright &y& Elsevier]

Abstract: Experimental results for the restricted energy loss of ultrarelativistic electrons, with Lorentz factors up to , in a thin silicon detector are presented. The combination of high Lorentz factors and thin targets, opens for the possibility to study two mutually excluding effects, both based upon theory and on scarce experimental observations. One is a disappearance of the density effect when the transit time becomes so short that the effect of plasma-oscillations becomes negligible. This would result in an increased energy loss as the Lorentz factor increases. The other is an effect based on the existence of a coherence length over which there are contributions to the energy loss. This effect leads to a substantially decreased energy loss for thin targets as the Lorentz factor increases. The latter is shown to be incompatible with our measurements, whereas the former may be present with a correction of a few percent to an otherwise constant energy loss. Furthermore, we point to significant effects related to synchrotron and transition radiation, that must be carefully considered in a possible future experiment, and may as well have been of significance for the conclusion in earlier experiments. [Copyright &y& Elsevier]

Abstract: High-power diodes with the radiation enhanced diffusion (RED) of Pd are shown to have much higher ruggedness during the reverse recovery compared to that of the Pt. Anode doping profiles measured by spreading resistance technique after a 10MeV He implantation with subsequent annealing between 500 and 800°C reveal different compensation effects between the Pd and Pt. The in-diffusing Pd converts the n-type background doping concentration of N D =3×1013 cm−3 in the position of radiation defects to that of a p-type with about one order higher concentration. The created low-doped p-layer significantly increases ruggedness of diodes during reverse recovery. In the diodes with the Pt layer, only a modest compensation is observed, a conversion to a p-type layer is missing and robustness is much lower. The DLTS spectra for the Pt and Pd devices show a similar electronic structure and introduction rates of defects at 700°C, while they differ significantly at 600 and 650°C both for the majority and minority carriers. It is preliminary suggested that the strong compensation effect after the RED of Pd is caused by a high introduction rate of an acceptor deep level at the lower half of the silicon bandgap. [Copyright &y& Elsevier]

Abstract: This work focuses on the investigation of radiation-induced defects responsible for the degradation of silicon detector performance. Comparative studies of the defects induced by irradiation with 60Co-γ rays, 6 and 15MeV electrons, 23GeV protons and reactor neutrons revealed the existence of point defects and cluster-related centers having a strong impact on damage properties of Si diodes. The detailed relation between the “microscopic” reasons as based on defect analysis and their “macroscopic” consequences for detector performance is presented. In particular, it is shown that the changes in the Si device properties (depletion voltage and leakage current) after exposure to high levels of 60Co-γ doses can be completely understood by the microscopically investigated formation of two point defects, a deep acceptor and a shallow donor, both depending strongly on the oxygen concentration in the silicon bulk. Specific for hadron irradiation are the annealing effects which decrease (increase) the originally observed damage effects as seen by the changes of the depletion voltage and these effects are known as “beneficial” and “reverse” annealing, respectively. A group of three cluster-related defects, revealed as deep hole traps, proved to be responsible specifically for the reverse annealing. Their formation is not affected by the oxygen content or silicon growth procedure suggesting that they are complexes of multi-vacancies located inside extended disordered regions. [Copyright &y& Elsevier]

Radiation tolerance of small-sized CsI(TI) crystals coupled to silicon photodiodes was studied by using protons. Irradiations up to the fluence of 1012 protons/cm² were used. Degradation of light output by less than 5% was achieved. [ABSTRACT FROM AUTHOR]

CERN RD39 Collaboration develops radiation-hard cryogenic silicon detectors. Recently, we have demonstrated improved radiation hardness in novel Current Injected Detectors (CID). For detector characterization, we have applied cryogenic Transient Current Technique (C-TCT). In beam tests, heavily irradiated CID detector showed capability for particle detection. Our results show that the CID detectors are operational at the temperature -50° C after the fluence of 1 × 1016 1 MeV neutron equivalent/cm2. [ABSTRACT FROM AUTHOR]

Single crystals of CdZnTe of dimensions 10 x 10 x 3 mm³ and HgI2 of dimensions 10 x 10 x 2 mm³ were fabricated into planar detectors. Four sets of detectors were then exposed to simulated solar proton events of varying magnitude at the Kernfysisch Versneller Instituut in the Netherlands. Events were simulated by generating protons over the energy range 60 MeV to 200 MeV in 10 energy bands which approximated the spectral shape of the August 1972 solar particle event. One pair of detectors (a CdZnTe and a Hgl2) was exposed to an integral fluence of 108 protons cm-2, a second to 109 protons cm-2, a third to 1010 protons cm-2 and the fourth to 1011 protons cm-2. The latter corresponds to an absorbed dose in silicon of 100 krad or in SI units, 1 kGy. The detectors were characterized both before and after the irradiations in terms of background count rate and spectral performance using 55Fe, 109Cd, 241Am, 57Co and 137 radioactive sources. Typical pre-irradiation FWHM energy resolutions of 3 keV and 4 keV were recorded at 60 keV for the CdZnTe and HgI2 detectors, respectively. It was found that HgI2 is very radiation tolerant showing little degradation in energy resolution or charge collection efficiency (CCE) for input fluences up to 1011 protons cm-2. CdZnTe, on the other hand, showed a clear degradation in energy resolution and CCE for input fluences above 109 protons cm-2. For example, the energy resolution degraded by a factor of 3 between 109 and 1010 protons cm-2 while the CCE decreased by a factor of 2. [ABSTRACT FROM AUTHOR]

Experimental results are presented that characterize the implosion dynamics and radiation output of wire-array Z pinches on the 1-MA, 100-ns rise-time Cornell Beam Research Accelerator (COBRA) [J. B. Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)]. The load geometries investigated include 20-mm-tall cylindrical arrays ranging from 4 to 16 mm in diameter, and consisting of 8, 16, or 32 wires of either tungsten, aluminum, or Invar (64% iron, 36% nickel). Diagnostics fielded include an optical streak camera, a time-gated extreme-ultraviolet framing camera, a laser shadowgraph system, time-integrated pinhole cameras, an x-ray wide-band focusing spectrograph with spatial resolution, an x-ray streak camera, a load voltage monitor, a Faraday cup, a bolometer, silicon diodes, and diamond photoconducting detectors. The data produced by the entire suite of diagnostics are analyzed and presented to provide a detailed picture of the overall implosion process and resulting radiation output on COBRA. The highest x-ray peak powers (300–500 GW) and total energy yields (6–10 kJ) were obtained using 4-mm-diameter arrays that stagnated before peak current. Additional findings include a decrease in soft x-ray radiation prior to stagnation as the initial wire spacing was changed from 1.6 mm to 785 μm, and a timing correlation between the onset of energetic electrons, hard x-ray generation, and the arrival of trailing current on axis—a correlation that is likely due to the formation of micropinches. The details of these and other findings are presented and discussed. [ABSTRACT FROM AUTHOR]

Simulation of energy deposition in silicon by nuclear reactions is a crucial point for single event prediction tool development. In order to compare with the simulation of nuclear reactions, a silicon diode is irradiated by a 30 MeV and 63 MeV neutron beam and the energy deposited by each nuclear reaction is measured. Simulation of the ionizing energy deposition in the irradiated diode is performed by the Monte Carlo method using nuclear reaction databases. Neutron beam spectra and surrounding materials are taken into account. Experimental and simulated results are shown to be in good agreement. [ABSTRACT FROM PUBLISHER]

3D pixel sensors are a novel type of silicon detector designed for High Energy Physics and other applications. Their features include high spatial resolution and radiation tolerance. The design consists of alternating rows of n- and p-type columns in a p-type substrate. Capacitance data are presented for 3D pixel devices characterized after exposure to various fluences of 55 MeV protons. Simulations and two methods for the measurement of the inter-electrode capacitance as a function of input signal frequency are shown. [ABSTRACT FROM AUTHOR]

Abstract: A model describing the passivation by Li atoms of acceptors arising from radiation damage in Si detectors has been developed. Our studies indicate that it is possible to produce a protocol that will allow the in-situ recovery of lithium-drifted Si particle detectors under irradiation by high-energy particles. Our model for particle damage recovery is supported by preliminary results on the recovery of old, degraded detectors. [Copyright &y& Elsevier]

Plans are well advanced for a phased upgrade program of the Large Hadron Collider (LHC) at CERN. An improvement of nearly a factor of ten to reach a luminosity close to 1035 cm2 s-1 is the target of the upgraded machine, called the Super LHC (SLHC). The innermost tracker devices in the SLHC will be exposed to hadron radiation doses in excess of 1 times 1016 neq cm-2. The detectors to be used in the tracker system of the SLHC experiments need therefore to be qualified to these extreme fluences. Segmented n-strip silicon detectors made with thin (140 mum) and standard (300 mum) p-type substrates have been irradiated with neutrons to different fluences up to 1 times 1016 neq cm-2 and characterised in term of charge collection efficiency measurements using high speed (40 MHZ, 25 ns shaping time) analogue electronics. These measurements are the first direct comparison between the charge collection performance of thin and thick silicon microstrip devices as a function of different fluences relevant to future supercolliders. They also set a reference for the maximum collected charge by segmented sensors made in planar technologies (microstrip and pixel detectors) at these extreme doses, allowing for predictions on the functionality of silicon detectors that can operated in the inner tracking system of SLHC experiments. [ABSTRACT FROM PUBLISHER]

Radiation detectors based on the deposition of a 10 to 30 μm thick hydrogenated amorphous silicon (a-Si:H) sensor directly on top of integrated circuits have been developed. The performance of this detector technology has been assessed for the first time in the context of particle detectors. Three different circuits were designed in a quarter micron CMOS technology for these studies. The so-called TFA (Thin-Film on ASIC) detectors obtained after deposition of a-Si:H sensors on the developed circuits are presented. High internal electric fields (104 to 105 V/cm) can be built in the a-Si:H sensor and overcome the low mobility of electrons and holes in this amorphous material. However, the deposited sensor's leakage current at such fields turns out to be an important parameter which limits the performance of a TFA detector. Its detailed study is presented as well as the detector's pixel segmentation. Signal induction by generated free carrier motion in the a-Si:H sensor has been characterized using a 660 nm pulsed laser. Results obtained with a TFA detector based on an ASIC integrating S ns peaking time pre-amplifiers are presented. Direct detection of 10 to 50 keV electrons and 5.9 keY X-rays with the detectors are then shown to understand the potential and the limitations of this technology for radiation detection. [ABSTRACT FROM AUTHOR]

Our group has been investigating the effects related to radiation damage of CCDs since 1998. In a series of measurements in 2003 we found the puzzling effect of very slow filling of charge traps created by radiation damage of the silicon device. In 2005 we intended to study this phenomenon in detail. However, while in 2003 we could see all the traps created by neutron irradiation in 1998-1997 unchanged, such traps unexpectedly almost completely disappeared in 2005. We explain this as an effect of annealing induced by electron irradiation, as in 2003 we irradiated with electrons the same device irradiated with neutrons in 1997-1998. Results of the 2005 measurements are presented. [ABSTRACT FROM AUTHOR]

Abstract: In this contribution, the correlation between fundamental interaction processes induced by radiation in silicon and observable effects which limit the use of silicon detectors in high-energy physics experiments is investigated in the frame of a phenomenological model which includes: generation of primary defects at irradiation, starting from elementary interactions in silicon; kinetics of defects, effects at the p–n junction detector level. The effects due to irradiating particles (pions, protons, neutrons), to their flux, to the anisotropy of the threshold energy in silicon, to the impurity concentrations and resistivity of the starting material are investigated as time, fluence and temperature dependences of detector characteristics. The expected degradation of the electrical parameters of detectors in the complex hadron background fields at LHC & SLHC is predicted. [Copyright &y& Elsevier]

Abstract: The control of the carrier lifetime profile in semiconductor power devices is of fundamental importance to optimize device parameters. With respect to traditional technologies such as diffusion of metallic impurities, light ion irradiation at low doses provides precise spatial localization of defects acting as carrier traps and recombination centres. Hence, the generation of suitable lifetime profiles obtained by controlling ion fluence and energy allows the reduction of turn-off times and switching losses in power electronic devices. In order to characterise the effects of ion irradiation on carrier lifetime profiles, we have used the ion beam induced charge collection (IBIC) technique in lateral geometry to measure charge collection efficiency (CCE) profiles in silicon p+/n/n+ diodes under different applied bias conditions before and after a frontal 6.5MeV He++ ion implantation at a total fluence of 2×1012 ions/cm2. After the irradiation, the profile shows a clear drop of charge collection efficiency which occurs at the end of the ion range. The formalism based on Shockley–Ramo–Gunn’s theorem was applied to interpret the CCE profiles in both virgin and irradiated samples and to assess the free carrier lifetime profile modification following the radiation damage. [Copyright &y& Elsevier]

Abstract: Ambient dose-equivalent results from an in-flight comparison between different tissue-equivalent proportional counters and silicon diode spectrometers from seven European institutes are presented and compared with calculations using the EPCARD computer program. The measurements were performed on 40000 and 32000ft in narrow target areas at latitudes and . Keeping the altitude and geographic position almost constant provided unique conditions for comparisons. The different measuring systems as well as the calculations are in remarkably good agreement, with an average standard deviation in the ambient dose equivalent between 6% and 21%. The ratio between calculated and measured ambient dose-equivalent rates varies between 0.91 and 1.09, with an average of . Nevertheless some systematic differences in the experimentally determined ambient dose equivalent and its low-LET and high-LET components are noticed and discussed. It is concluded that the standard deviation between different instruments can through optimization and harmonization of the calibration procedures be reduced by up to a factor of two. [Copyright &y& Elsevier]

The results of investigation of n ++ p + pp + silicon detector structures manufactured from p silicon are presented. These detectors demonstrate the effect of internal amplification of a signal (with a gain of 20) with retained properties of the detector as a spectrometric device. An efficient lowering of the energy level for the detected ionizing radiation is demonstrated. [ABSTRACT FROM AUTHOR]

We have fabricated a position sensitive radiation detector by creating radiation damage regions in a Si photodiode. Radiation damage was created in layers at a depth of several μm by 7Li and 16O ion beams which had an energy between 2 and 4 MeV. Ions were focused and scanned using a nuclear microprobe facility. The ion beam induced charge (IBIC) signals created in diodes during irradiation were simultaneously measured to monitor the exact ion beam fluence and analyzed to estimate the amount of defects created. By controlling the ion microbeam scanning system, graduated and position dependent radiation damage was produced in different micro-patterns. Such structures may be used as a simple position sensitive radiation sensor. [ABSTRACT FROM AUTHOR]

In this Paper we describe the performance of a rad- hard diode (A1/p+/n/n+/Al), developed in the framework of research and development programs for the future CMS experiment at LHC, for detection and spectrometry of X-and -γ-rays envis-aging its use in characterization of porous structures by X-ray tomography. The diode's response was studied using 57 Co, 133 and 241Am radioactive sources at room temperature. A reasonable good energy resolution was obtained in the energy range between 30 and 360 keV (FWHM = 5.2 keV and 5.7 keV, respectively). In the same energy range, measurements of full-energy peak efficien- cies were carried out and compared with the theoretical values. For 59.5 keV photons the angular dependence of the efficiency was also measured. The results have demonstrated that this diode is appro- priate for direct detection of low energy electromagnetic radiation. [ABSTRACT FROM AUTHOR]

Abstract: We report on JFET devices fabricated on high-resistivity silicon with a radiation detector technology. The problems affecting previous versions of these devices have been thoroughly investigated and solved by developing an improved fabrication process, which allows for a sizeable enhancement in the JFET performance. In this paper, the main features of the fabrication technology are presented and selected results from the electrical and noise characterization of transistors are discussed. [Copyright &y& Elsevier]

Abstract: Radiation hardness of silicon detectors based on thin epitaxial layer on Czochralski (CZ) substrate for the LHC upgrade (Super-LHC) was studied. No type inversion was observed after irradiation by 24GeV/c protons up to the fluence of 1016 p/cm2 due to overcompensating donor generation. After long-term annealing (corresponding to 500 days at room temperature) proton irradiated devices show a decrease of the effective doping concentration and then undergo type inversion. Measurements confirm that thin epitaxial devices on CZ substrate could be used for innermost layers of vertex detectors in future experiments at the Super-LHC. [Copyright &y& Elsevier]

Abstract: In this paper, we discuss the measurement of charge collection in irradiated silicon pixel sensors and the comparison with a detailed simulation. The simulation implements a model of radiation damage by including two defect levels with opposite charge states and trapping of charge carriers. The modeling proves that a doubly peaked electric field generated by the two defect levels is necessary to describe the data and excludes a description based on acceptor defects uniformly distributed across the sensor bulk. In addition, the dependence of trap concentrations upon fluence is established by comparing the measured and simulated profiles at several fluences and bias voltages. [Copyright &y& Elsevier]

Time-resolved measurements of the absolute free-bound (FB) continuum spectrum emitted from a 12-cm-diameter argon gas-puff Z-pinch driven at ∼6-MA peak current with 220- to 260-ns implosion times are reported. A crystal spectrometer is used with silicon diode detectors to provide kiloelectronvolt spectral resolution. The energy and absolute-intensity calibration procedures for the spectrometer are described. The slope of the FB continuum is well represented by a decaying exponential spectrum with a single electron temperature from which spatially averaged, time-resolved (Te(t)), and time-integrated ((Te)) electron temperatures are inferred. An expression for the absolute FB continuum, which takes into account recombination onto bare as well as H-like species, is presented and used to infer time-integrated spatially averaged ion densities (ni). The values of (Te) and (ni) are in general agreement with the values of these quantities obtained by using the conventional K-shell line-ratio method. Values of Te(t) peak on the rise of the continuum radiation pulse and gradually decrease during the pulse. The fraction of the total energy radiated in the K-shell that resides in the FB continuum is 6%–10%, and this fraction increases with (ni). Calculated continuum spectra are in agreement with measured spectra. [ABSTRACT FROM AUTHOR]

Commercial silicon Schottky barrier power diodes have been subjected to 203 MeV proton irradiation and the effects of the resultant displacement damage on the I–V characteristics have been observed. The diodes show excellent resistance to radiation damage. Changes in forward and reverse bias I–V characteristics are reported for irradiated commercial Schottky barrier diodes at fluences up to 4 × 1014 p/cm². Small changes are seen in the reverse bias I–V characteristics with increasing irradiation fluence. In forward bias, the series resistance is observed to increase as the fluence increases. The changes in series resistance are interpreted as being due to changes in the effective dopant density due to carrier removal by the defects produced. [ABSTRACT FROM AUTHOR]

Abstract: We have developed an unconventional Transition Radiation Detector (SiTRD) based on silicon strip detectors (SSDs) operating inside a magnetic field. In this way, the path of the radiating particle is deflected with respect to the transition radiation X-rays that convert in a detector region far away from the charged particle track. In this paper we will show the results of a beam test performed at low momenta, up to , with a reduced scale detector prototype. We have also implemented a full Monte Carlo simulation to design a SiTRD for an accelerator or a cosmic ray experiment at higher momenta, up to . We have simulated two different detector configurations and we have studied their performance. [Copyright &y& Elsevier]