Search

One-dimensional modeling and simulations of the electric and weighting fields have been systematically carried out for 2D-Planar-Electrode and 3D type detectors. Poisson and Laplace equations have been solved analytically in Cartesian and cylindrical coordinates with well defined boundary conditions. It has been found that the electric field profile and full depletion voltage depend in general on the detector effective doping density (N e f f) and electrode spacing (λ C), while the weighting field depends only on the electrode spacing and relative geometry size of the collecting electrode with respect to the electrode spacing. For 2D-Planar-Electrode strip and pixel detectors, the full depletion voltage will be somewhat higher than that of 2D pad detectors, and the weighting field will be more concentrated near the collecting electrode due to the "small pixel" effect. For 3D-Trench-Electrode (cylindrical type) detectors, however, exact one-dimensional solutions have been obtained for electric and weighting fields. The results are compared to those obtained for 2D-Planar-Electrode pad detectors and conventional 3D-Column-Electrode detectors. [ABSTRACT FROM AUTHOR]

Abstract: For the development of radiation-hard Si detectors for the SiD BeamCal (Si Detector Beam Calorimeter) program for International Linear Collider (ILC), n-type Magnetic Czochralski Si detectors have been irradiated first by fast neutrons to fluences of 1.5×1014 and 3×1014 neq/cm2, and then by gamma up to 500Mrad. The motivation of this mixed radiation project is to test the radiation hardness of MCZ detectors that may utilize the gamma/electron radiation to compensate the negative effects caused by neutron irradiation, all of which exists in the ILC radiation environment. By using the positive space charge created by gamma radiation in MCZ Si detectors, one can cancel the negative space charge created by neutrons, thus reducing the overall net space charge density and therefore the full depletion voltage of the detector. It has been found that gamma radiation has suppressed the room temperature reverse annealing in neutron-irradiated detectors during the 5.5month of time needed to reach a radiation dose of 500Mrad. The room temperature annealing (RTA) was verified in control samples (irradiated to the same neutron fluences, but going through this 5.5month RTA without gamma radiation). This suppression is in agreement with our previous predictions, since negative space charge generated during the reverse annealing was suppressed by positive space charge induced by gamma radiation. The effect is that regardless of the received neutron fluence the reverse annealing is totally suppressed by the same dose of gamma rays (500Mrad). It has been found that the full depletion voltage for the two detectors irradiated to two different neutron fluences stays the same before and after gamma radiation. Meanwhile, for the control samples also irradiated to two different neutron fluences, full depletion voltages have gone up during this period. The increase in full depletion voltage in the control samples corresponds to the generation of negative space charge, and this increase in concentration of negative space charge goes up with the neutron fluence. If we assume the reverse annealing is also taking place for the two gamma-irradiated samples with similarly different concentrations of negative space charge generated, the observed effect of no changes in space charge (no changes in V fd ) in these two gamma-irradiated samples would imply that concentrations of positive space charge created in these two control samples are different at the same gamma dose, and gamma irradiation effectively “switched off”, the RT (room temperature) reverse annealing of neutron irradiation. It has also been found that as soon as the gamma irradiation stops, the RT reverse annealing of neutron irradiation-induced defects resumes with same rate as that of the control detectors. This behavior in mixed radiation samples (neutron plus gamma) would suggest some nonlinear effect (defects induced by mixed-radiations are not additive of those by individual radiation alone), or interaction of radiation induced acceptor-type and donor-type defects. [Copyright &y& Elsevier]

Abstract: We undertook systematic transient current technique (TCT) studies, measuring the shapes of electron- and hole-transient currents in three sets of samples irradiated by 24GeV/c protons at fluences 1.6×1014–2.4×1015 p/cm2. We carried out these measurements after leaving the samples to anneal for 22–23 days at room temperature. The three sets comprised (1) magnetic Czochralski (MCZ) n-type Si detectors; (2) MCZ p-type Si detectors; and (3) float-zone (FZ) n-type Si detectors (control set). The control set showed no surprises. The space charge sign inversion (SCSI) had already occurred at the lowest fluence (1.6×1014 p/cm2), and the double junction/double peak effect was readily apparent, with the first junction, the minor one, near the p+ contact, which changes very little with bias voltages. It is superseded by the second junction near the n+ contact (negative space charge) at biases higher than the full-depletion voltage. For both MCZ n-type and p-type detectors, the double junction/double peak effect also was initiated at the lowest fluence, but the standard SCSI evident in FZ n-type detectors (wherein the negative space charge dominates the entire detector) was not seen in that fluence range. However, in these two groups, the double junction/peak effect persisted into subsequent higher fluences with almost equal junctions near the p+ and n+ contacts, regardless of bias voltages, which may be much larger than the full-depletion voltages. This new effect, termed the equal-double-junction effect, is unique for the 24GeV/c proton-irradiated MCZ (n and p) Si detectors. It is evident by the almost identical shapes in TCT currents, before trapping corrections, for both electrons (red laser on the p+ contact) and holes (on the n+ contact), with the first peak always dominating a small second peak at any bias voltages. After trapping corrections, the heights of the two peaks are about the same, suggesting the existence of nearly equal-double junctions in the detector. [Copyright &y& Elsevier]

Abstract: The aim of this study is the evaluation of radiation effects in detectors based on p-type magnetic czochralski (MCz) Si that was converted to n-type by thermal donor (TD) introduction. As-processed p+-p-n+ detectors were annealed at 430°C resulting in p+-n(TD)-n+ structures. The space charge sign and the electric field distribution E(x) in MCz Si p+-n(TD)-n+ detectors irradiated by 24GeV/c protons were analyzed using the data on the current pulse response and the Double Peak (DP) electric field distribution model for heavily irradiated detectors. The approach considers an irradiated detector as a structure with three regions in which the electric field depends on the coordinate, and the induced current pulse response arises from the drift process of free carriers in the detector with variable electric field. Reconstruction of the E(x) profile from the pulse response shapes is performed employing a new method for DP electric field reconstruction. This method includes: (a) a direct extraction of charge loss due to trapping and (b) the fitting of a simulated pulse response to the “corrected” pulse by adjusting the electric field profiles in the three regions. Reconstruction of E(x) distribution showed that in the diodes irradiated by a proton fluence of (2–4)×1014 p/cm2 space charge sign inversion has occurred. This is the evidence that the influence of 24GeV/c proton radiation on MCz Si p+-n(TD)-n+ detectors is similar to that on p+-n-n+ detectors based on FZ or diffusion oxygenated n-type Si. [Copyright &y& Elsevier]

Abstract: For tracking at a high luminosity upgrade of the LHC, detector granularity, scale, and radiation resistance must increase. Material burden, cost, and construction must be kept manageable. One configuration which may facilitate these requirements is to build large multi-module units referred to here as “staves”. Design issues and prototyping results for staves are discussed. [Copyright &y& Elsevier]

Abstract: Positive space charge build-up was observed in proton—and neutron—irradiated high-resistivity magnetic Czochralski (MCZ) n-type Si detectors after gamma radiation. Space charge sign re-inversion (SCSRI) from negative to positive was achieved at the high dose of 454Mrad in a low-fluence proton irradiated MCZ Si detector. No SCSRI has been observed yet for low-fluence neutron-irradiated MCZ Si detectors at the highest dose in this study (662Mrad), but positive space charge is building up, and SCSRI is expected at higher doses. Up to the highest dose in this study, the double junction or double peak electric field distribution is still preserved even after SCSRI. No SCSRI was observed in control FZ Si detectors. Space charge sign inversion was also observed in high-resistivity as-processed MCZ p-type Si detectors after gamma radiation. [Copyright &y& Elsevier]

Abstract: A pellet target produces micro-spheres of different materials, which are used as an internal target for nuclear and particle physics studies. We will describe the pellet hydrogen behavior by means of fluid dynamics and thermodynamics. In particular, one aim is to theoretically understand the cooling effect in order to find an effective method to optimize the working conditions of a pellet target. During the droplet formation the evaporative cooling is best described by a multi-droplet diffusion-controlled model, while in vacuum, the evaporation follows the (revised) Hertz–Knudsen formula. Experimental observations compared with calculations clearly indicated the presence of supercooling, the effect of which is discussed as well. [Copyright &y& Elsevier]

Abstract: The novel Si stripixel detector, developed at BNL (Brookhaven National Laboratory), has been applied in the development of a prototype Si strip detector system for the PHENIX Upgrade at RHIC. The Si stripixel detector can generate two-dimensional (2D) position sensitivity with single-sided processing and readout. Test stripixel detectors with pitches of 85 and 560μm have been subjected to the electron beam test in a SEM set-up, and to the laser beam test in a lab test fixture with an table for laser scanning. Test results have shown that the and strips are well isolated from each other, and 2D position sensitivity has been well demonstrated in the novel stripixel detectors. [Copyright &y& Elsevier]

Abstract: Non-uniform distribution of the electric field outlined as double peak distortion (DPD) is considered for heavily irradiated silicon strip detectors, which were developed for the CERN-ATLAS semiconductor tracker. DPD originates from the non-uniform accumulation of electrons and holes from the bulk generated current that are captured by radiation induced defects: deep acceptors and donors with mid-gap energy levels. This corresponds to the formation of the low electric field region in the detector central part that consequently will delay charge collection. The electric field distributions at different reverse biases, fluences and detector operational temperatures are calculated using a one-dimensional Poisson equation as it was done earlier for pad detectors. It has been shown that due to the electric field focusing at the strips the DPD effect is more pronounced for strip detectors as compared to that in pad detectors. The double peak electric field distribution is evinced experimentally in current pulse response shape when the charge is collected along the strip axis. [Copyright &y& Elsevier]

A novel detector concept has been developed in this work that has the necessary properties to provide two-dimensional (2-D) position sensitivity with a moderate number of readout electronic channels and single-sided detector fabrication process. The concept is based on interleaved pixel electrodes arranged in a projective X–Y readout, which makes possible position encoding with minimum number of channels. In further discussions, we refer to this concept as “stripixel” detector, as it combines the 2-D position resolution of a pixel electrode geometry with the simplicity of the projective readout of a double-sided strip detector. For DC coupled detectors with large pitches (>20 μm), individual pixels are divided into X- and Y-cell that can be interleaved by many different schemes that ensure the charge sharing between them. This type of stripixel detectors is called interleaved stripixel detectors. When the detector pitch goes down (<20 μm), the X and Y-pixel may not have to be interleaved, and they can be connected in an alternating way to X–Y strip readout. This type of stripixel detectors is called alternating stripixel detectors (ASD). For ASD, a position resolution better than 1 μm in two dimensions can be achieved by determining the centroid of the charge collected on pixel electrodes with a granularity in the range of 5–6 μm. For AC coupled detectors, no interleaving scheme may be needed, and there may be no limit on the pitch size, i.e. it may go from pitches in the order of microns, to hundreds of microns or even mm''s. This electrode granularity does not pose difficult demands on the lithography and the fabrication technology. This novel detector concept can be applied to any semiconductor detectors/sensors, such as Si, Ge, GaAs, SiC, diamond, etc. [Copyright &y& Elsevier]

Novel detector type, named “Stripixel” detector developed at BNL, has been applied in the development of a prototype Si strip detector for the PHENIX Upgrade at RHIC. This novel detector type can generate X–Y two-dimensional position sensitivity with single-sided processing and readout. The prototype Si stripixel detector has an active area of about 3 cm×6 cm, which is divided into two identical halves. Both X and Y pitches are 80 μm, with a stereo angle of 4.6°. There are 384 X strips and 384 Y strips on each half of the detector. The first batch of prototype Si stripixel detectors has been produced at BNL. The initial tests of detector electrical properties have yielded good results. Charge collection tests on test-structure strip detectors have shown both X and Y position sensitivities to laser light. Beam tests on the Si strip detectors have been done at RIKEN in November 2002. [Copyright &y& Elsevier]

Detectors processed from standard and oxygenated Si are compared with respect to radiation hardness to ultra-high dose of γ-rays up to 1.76 Grad. The detectors are processed by different manufactures: Silicon Detector Development and Processing Lab (SDDPL) of BNL (USA), CIS (Germany) and Micron Semiconductor (UK). Oxygenation was performed either by using High Temperature, Long Time (HTLT) oxidation in oxygen-based ambient, or by short-time high-temperature oxidation in O2 followed by a long-time drive-in diffusion in N2. It has been shown that radiation hardness improvement in oxygenated detectors irradiated by γ-rays actually extends now up to ultra-high dose of 1.76 Grad. Effects of space charge sign inversion (SCSI) and linear build-up of negative space charge with γ-ray dose have been observed in standard Si detectors, similar to the case of neutron/proton irradiation. In contrast to standard Si in detectors, it has been revealed that in oxygenated Si detectors, positive space charge is accumulated with increasing dose up to 1.76 Grad with no SCSI (“positive space charge detectors”), which is unique for γ-irradiation. The advantage for using oxygenated Si detectors, as compared to standard Si detectors in practical applications in the ultra-high dose range of 1–1.76 Grad, has been demonstrated in terms of the profit in the reduction of full depletion voltage by a factor of 3–4, and in the reduction of leakage current by a factor of 3.2–5. In the pulse operational mode, however, polarization effect has been observed for oxygenated detectors irradiated to this ultra-high dose range of 1–1.76 Grad at room temperature, indicating the upper dose limit for a “damageless” oxygenated Si detector is about 1 Grad. The fact that this polarization occurs at RT is a paradox, since for other types of radiations it occurs only at cryogenic temperatures. [Copyright &y& Elsevier]

A variety of Si detectors have been developed and processed at BNL with its unique detector fabrication facility. These detectors include Si drift detectors (SDD); Si micro- and mm-strip detectors; Si pad detectors; and Si pixel detectors with a variety of configurations. In this paper, the details of the design and processing technology of large area SDD for the STAR SVT at RHIC, micro- and mm-strip detectors for CERN RD39/NA60 experiments; and radiation tolerant n/n, n/p pixel detectors for LHC experiments will be given. In addition, simulation results of new types of Si strip/pixel detectors with improved radiation tolerance will be presented for the first time. [Copyright &y& Elsevier]

In this work, the effects of 60Co γ -ray irradiation on high resistivity p -type diodes have been investigated. The diodes were exposed to dose values of 0.1, 0.2, 1, and 2 MGy. Both macroscopic (I – V , C – V) and microscopic investigations, by means of Thermally Stimulated Current (TSC) and Deep Level Transient Spectroscopy (DLTS) techniques, were conducted to characterize the radiation-induced changes. The investigated diodes were manufactured on high resistivity p -type Float Zone (FZ) silicon and were further classified into two types based on the isolation technique between the pad and guard ring: p -stop and p -spray. After irradiation, the macroscopic results of current–voltage and capacitance–voltage measurements were obtained and compared with existing literature data. Additionally, the microscopic measurements focused on the development of the concentration of different radiation-induced defects, including the Boron interstitial-Oxygen interstitial (B i O i) complex, the Carbon interstitial-Oxygen interstitial (C i O i) defect, the H40K, and the so-called I P ∗. To investigate the thermal stability of induced defects in the bulk, isochronal annealing studies were performed in the temperature range of 100 °C to 300 °C. These annealing processes were carried out on diodes irradiated with doses of 1 and 2 MGy. Furthermore, in order to investigate the unexpected results observed in the C – V measurements after irradiation with high dose values, the surface conductance between the pad and guard ring was measured as a function of both dose and annealing temperature. [ABSTRACT FROM AUTHOR]

New types of silicon pixel detectors have been proposed because of the need for more radiation hard semiconductor devices for the high luminosity tracking detector upgrades at the Large Hadron Collider. A novel type of 3D Si pixel detectors is proposed, with each cell of the 3D-Trench Electrode pixel detector featuring a concentric trench electrode surrounding the central collecting column electrode. The pixel sensor is an array of those individual cells. Systematic 3D simulations using Silvacos TCAD programs have been carried out to study the characteristics of this novel 3D pixel design and to compare to the traditional 3D column electrode pixel design. The 3D simulations show a much lower depletion voltage and a more uniform electric field in the new 3D-Trench Electrode pixel detectors as compared to the traditional 3D column Electrode detectors. The first prototype 3D-Trench Electrode pixel detectors have been manufactured at the Centro Nacional De Microelectronica. Preliminary electrical measurements are discussed and charge collection efficiency measurements are presented. [ABSTRACT FROM AUTHOR]

This study focuses on the properties of the B i O i (interstitial Boron–interstitial Oxygen) and C i O i (interstitial Carbon–interstitial Oxygen) defect complexes by 5.5 MeV electrons in low resistivity silicon. Two different types of diodes manufactured on p-type epitaxial and Czochralski silicon with a resistivity of about 10 Ω ⋅ cm were irradiated with fluence values between 1 × 1015 cm-2 and 6 × 1015 cm-2. Such diodes cannot be fully depleted and thus the accurate evaluation of defect concentrations and properties (activation energy, capture cross-section, concentration) from Thermally Stimulated Currents (TSC) experiments alone is not possible. In this study we demonstrate that by performing Thermally Stimulated Capacitance (TS-Cap) experiments in similar conditions to TSC measurements and developing theoretical models for simulating both types of B i O i signals generated in TSC and TS-Cap measurements, accurate evaluations can be performed. The changes of the position-dependent electric field, the effective space charge density N eff profile as well as the occupation of the B i O i defect during the electric field dependent electron emission, are simulated as a function of temperature. The macroscopic properties (leakage current and N eff) extracted from current–voltage and capacitance–voltage measurements at 20 °C are also presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this report, the processing of thermal donor (TD) compensated detectors is described. Heat treatment of Czochralski silicon (Cz-Si) wafers between 400 and 600°C leads to aggregation of interstitial oxygen atoms resulting in electrically active shallow levels in the silicon band gap. This process is known as TD formation. It depends on the temperature, the oxygen concentration in the silicon material and the presence of hydrogen in device manufacturing process. The oxygen concentration in silicon wafers grown by Magnetic Czochralski (MCz) method is sufficiently high in order that the concentration of TDs is comparable with the initial phosphorous or boron doping of high-resistivity Cz-Si. The TD formation has been studied by monitoring the detector full depletion voltage with respect to the heating time at 430°C. The TD formation has been verified by Deep Level Transient Spectroscopy (DLTS) measurements. In addition, the annealing behavior of the irradiated samples at different temperatures is discussed. The TD formation in n+/p−/p+ pad detectors has been observed not to influence the leakage current of the devices. Thus, the full depletion voltage of the detectors processed on p-type MCz-Si wafers can be modified by this method. [Copyright &y& Elsevier]

An X-ray Active Matrix Pixel Sensor (XAMPS) for recording Data from the Scanning Transmission Electron Microscope (STEM) was designed, produced and tested. The reason for measuring scattering angle of all STEM electrons is given together with the requirement on the performance of the XAMPS. Principles of the measurement of the number of STEM electrons scattered in a particular direction are summarized. Results of tests performed on a produced detector are described and the problem with the formation of an insulation layer between silicon and aluminum is identified. A change in the design of the pixel is proposed which results in a fully functioning XAMPS even with the insulation layer present. [Copyright &y& Elsevier]

In this paper, we present total-ionization dose (TID) radiation hardness test methods and the analysis of experimental results of a low-noise front-end ASIC dedicated to CZT and/or Si-PIN detectors for X-ray surveys in space. A six-channel front-end readout prototype chip is designed and implemented in 180 nm CMOS process. The topology, circuit descriptions, and radiation-hardened-by-design techniques are firstly presented. Secondly, the radiation test apparatus, radiation test conditions, DUTs, test boards and the radiation test flow are introduced. Then, experimental results including the electrical performance before irradiation, key parameters including leakage current, gain, nonlinearity, and ENC slope after TID radiation are described and discussed. With the accumulation of the total dose, the leakage current is suppressed; the gain and the nonlinearity vary slightly; the noise performance is degraded. After the annealing process, the ASIC operates normally. However, the noise performance is degenerated. The ENC slope is twice than that before irradiation. It can be concluded that the proposed ASIC can resist total dose of 200 krad (Si) according to the radiation hardness assessment. [ABSTRACT FROM AUTHOR]

In this work, two particular properties of the position-sensitive, thick silicon detectors (known as the “E” detectors) in the High Resolution Array (HiRA) are investigated: the thickness of the dead layer on the front of the detector, and the overall thickness of the detector itself. The dead layer thickness for each E detector in HiRA is extracted using a measurement of alpha particles emitted from a 212 Pb pin source placed close to the detector surface. This procedure also allows for energy calibrations of the E detectors, which are otherwise inaccessible for alpha source calibration as each one is sandwiched between two other detectors. The E detector thickness is obtained from a combination of elastically scattered protons and an energy-loss calculation method. Results from these analyses agree with values provided by the manufacturer. [ABSTRACT FROM AUTHOR]

Searches for rare nuclear processes, such as neutrinoless double beta-decay and the interactions of WIMP dark matter, are motivating experiments with ever-decreasing levels of radioactive backgrounds. These background reductions are achieved using various techniques, but amongst the most important is minimizing radioactive contamination in the materials from which the experiment is constructed. To this end there have been decades of advances in material sourcing, manufacture and certification, during which researchers have accumulated many thousands of measurements of material radiopurity. Some of these assays are described in publications, others are in databases, but many are still communicated informally. Until this work, there has been no standard format for encoding assay results and no effective, central location for storing them. The aim of this work is to address these long-standing problems by creating a concise and flexible material assay data format and powerful software application to manipulate it. A public installation of this software, available at http://www.radiopurity.org , is the largest database of assay results ever compiled and is intended as a long-term repository for the community's data. [ABSTRACT FROM AUTHOR]

Detectors manufactured on p-type silicon material are known to have significant advantages in very harsh radiation environment over n-type detectors, traditionally used in High Energy Physics experiments for particle tracking. In p-type (n + segmentation on p substrate) position-sensitive strip detectors, however, the fixed oxide charge in the silicon dioxide is positive and, thus, causes electron accumulation at the Si/SiO 2 interface. As a result, unless appropriate interstrip isolation is applied, the n-type strips are short-circuited. Widely adopted methods to terminate surface electron accumulation are segmented p-stop or p-spray field implantations. A different approach to overcome the near-surface electron accumulation at the interface of silicon dioxide and p-type silicon is to deposit a thin film field insulator with negative oxide charge. We have processed silicon strip detectors on p-type Magnetic Czochralski silicon (MCz-Si) substrates with aluminum oxide (Al 2 O 3 ) thin film insulator, grown with Atomic Layer Deposition (ALD) method. The electrical characterization by current–voltage and capacitance−voltage measurement shows reliable performance of the aluminum oxide. The final proof of concept was obtained at the test beam with 200 GeV/c muons. For the non-irradiated detector the charge collection efficiency (CCE) was nearly 100% with a signal-to-noise ratio (S/N) of about 40, whereas for the 2×10 15 n eq /cm 2 proton irradiated detector the CCE was 35%, when the sensor was biased at 500 V. These results are comparable with the results from p-type detectors with the p-spray and p-stop interstrip isolation techniques. In addition, interestingly, when the aluminum oxide was irradiated with Co-60 gamma-rays, an accumulation of negative fixed oxide charge in the oxide was observed. [ABSTRACT FROM AUTHOR]

Abstract: The reverse current of irradiated Si detectors was analyzed in terms of carrier generation via defects with the energy levels in the Si bandgap. The data for detectors irradiated by 23GeV protons and 1MeV neutrons were obtained in the temperature (T) range of 200–300K. Two models of the bulk generation current were developed to allow fitting and simulation of the reverse current vs. T data. These are a model of carrier generation via a single effective energy level for the direct estimation of detector performance, and a model of two generation centers with the effective energy levels originating from radiation-induced deep levels adjacent to the midgap. The influence of the bandgap temperature dependence (E g (T)) on the parameters of the current generation centers was estimated. The first model gives the effective level energy of E v +0.65eV and a linear dependence of the effective defect concentration on fluence. The second model involves contribution from deep donors and deep acceptors positioned at E v +0.48eV and E c −0.52eV, respectively, and is adapted for simultaneous calculation of the reverse current and the electric field distribution in irradiated detectors. The results of the study show that: (a) both models fit well to the experimental data; (b) contribution of the E g (T) dependence to E t does not exceed 5%; (c) taking into consideration the bulk generation current gives the correct electric field distribution, which is a key reference for other characteristics of irradiated Si detectors; and (d) the generation lifetime is significantly larger than the carrier trapping time constant pointing to additional levels taking part in trapping of the drifting charge. [Copyright &y& Elsevier]

Abstract: Recent experiments on silicon detectors developed by the CERN-RD50 collaboration for very high luminosity colliders showed a significant enhancement of the collected charge Q c in Si detectors irradiated to the fluence of 1015–1016 n eq /cm2 if the devices were operated at high bias voltage. The enhancement arises from carrier avalanche multiplication in high electric field of the junction. However, calculated and experimental results indicated that a maximum Q c enhancement is much lower than the signal gain in avalanche photodiodes. The study of the collected charge in Si n-on-p strip detectors described here is focused on the restriction of the internal gain in irradiated Si strip detectors. It is demonstrated that (1) the gain in the collected charge due to avalanche multiplication is strongly restricted by the negative feedback arisen from a space charge limited current (SCLC negative feedback), which is an inherent property of heavily irradiated Si detectors with high concentration of radiation-induced defects; (2) the dependence of the gain on fluence is nonmonotonous due to competition between enhanced carrier trapping at high fluence and avalanche multiplication, which correlates with recent experimental results; (3) SCLC negative feedback makes the internal gain practically insensitive to the design of the detector region with high electric field. The results of this study show that the avalanche multiplication effect can be efficient in improving the radiation performance of Si detectors developed for the sLHC in a limited fluence range, which luckily covers the range expected in the upgraded LHC experiments. [Copyright &y& Elsevier]

Abstract: The model explaining an enhanced collected charge in detectors irradiated to 1015–1016 neq/cm2 is developed. This effect was first revealed in heavily irradiated n-on-p detectors operated at high bias voltage ranging from 900 to 1700V. The model is based on the fundamental effect of carrier avalanche multiplication in the space charge region and in our case is extended with a consideration of p–n junctions with a high concentration of the deep levels. It is shown that the efficient trapping of free carriers from the bulk generation current to the deep levels of radiation induced defects leads to the stabilization of the irradiated detector operation in avalanche multiplication mode due to the reduction of the electric field at the junction. The charge collection efficiency and the detector reverse current dependences on the applied bias have been numerically simulated in this study and they well correlate to the recent experimental results of CERN RD50 collaboration. The developed model of enhanced collected charge predicts a controllable operation of heavily irradiated detectors that is promising for the detector application in the upcoming experiments in a high luminosity collider. [Copyright &y& Elsevier]

Abstract: The collected charge in Si detectors irradiated up to the fluences of Super-LHC range (1016 neq cm−2) is calculated using an approach of double peak electric field distribution with an active base region. In the calculations the base region located between the space charge regions is considered as an active element of the detector structure in which the electric field is non-zero and depends on the irradiation fluence. With this advanced approach, the collected charge vs. fluence dependences is calculated and compared to those obtained using a standard linear electric field in an irradiated Si detector. The study is carried out for pad detectors, and for strip detectors with a strip pitch of 80μm typical for ATLAS topology. It is shown that at the fluence ≥1015 cm−2 the electric field in the active base stimulates an increase of the collected charge by a factor of 1.3 and 4.2 in strip and pad detectors, respectively. The values of the collected charge calculated in the assumption of the double peak electric field and active base are still smaller than the experimental data. This suggests that additional effects may contribute to the collected charge that is under study. [ABSTRACT FROM AUTHOR]

Abstract: A heavily irradiated (3×1015 1MeVneq/cm2) Current Injected Detector (CID) was tested with 225GeV muon beam at CERN H2 beam line. In the CID concept the current is limited by the space charge. The injected carriers will be trapped by the deep levels and this induces a stable electric field through the entire bulk regardless of the irradiation fluence the detector has been exposed to. The steady-state density of the trapped charge is defined by the balance between the trapping and the emission rates of charge carriers (detrapping). Thus, the amount of charge injection needed for the electric field stabilization depends on the temperature. AC-coupled 16cm2 detector was processed on high resistivity n-type magnetic Czochralski silicon, and it had 768 strips, 50μm pitch, 10μm strip width and 3.9cm strip length. The beam test was carried out using a silicon beam telescope that is based on the CMS detector readout prototype components, APV25 readout chips, and eight strip sensors made by Hamamatsu having 60μm pitch and intermediate strips. The tested CID detector was bonded to the APV25 readout, and it was operated at temperatures ranging from −40 to −53°C. The CID detector irradiated at 3×1015 1MeVneq/cm2 fluence shows about 40% relative Charge Collection Efficiency with respect to the non-irradiated reference plane sensors. [Copyright &y& Elsevier]

Abstract: Experimental results and simulations of Charge Collection Efficiency (CCE) of Current Injected Detectors (CIDs) are focused. CID is a concept where the current is limited by the space charge. The injected carriers will be trapped by the deep levels. This induces a stable electric field through the entire bulk regardless of the irradiation fluence the detector has been exposed. Our results show that the CCE of CIDs is about two times higher than of regular detectors when irradiated up to 1×1016 cm−2. The higher CCE is achieved already at −50°C temperatures. [Copyright &y& Elsevier]

Abstract: The CERN RD39 Collaboration has constructed a Transient Current Technique (TCT) measurement setup, which is capable to operate below liquid nitrogen temperatures. By analyzing the current transients, it is possible to extract the full depletion voltage, effective trapping time, electric field distribution and the sign of the space charge in the silicon bulk. Our results show that the effective space charge and trapping can be manipulated by charge injection and temperature. This might allow significantly higher Charge Collection Efficiency (CCE) compared to the detectors operating under normal reverse bias and at temperatures from 0 to . [Copyright &y& Elsevier]

Abstract: Radiation hardness up to is required in the future high-energy physics experiments. This is well beyond the radiation tolerance of even the most advanced semiconductor detectors fabricated by commonly adopted technologies. The Current Injected Detector (CID) is a device in which the current is limited by the space charge, which originates from injected carriers trapped by the deep levels. This induces a stable electric field through the entire detector bulk regardless of the irradiation fluence the detector has been exposed to. The steady state density of the trapped charge is defined by the balance between the trapping and emission rates of charge carriers (detrapping). Thus, the amount of charge injection needed for electric field stabilization depends on the temperature. The CID mode has a new specific feature which limits the maximum operational voltage. It is connected with the space charge density saturation and the sharp current rising at the threshold voltage . The value of is proportional to the irradiation fluence and it increases with respect to the irradiation fluence extending the range of the operation voltage. [Copyright &y& Elsevier]

Abstract: We are studying the operation of silicon microstrip detector with readout electronics in the temperature range from 90 to 130K. The sensor can be operated in the current-injection mode which significantly improves its radiation hardness. A first module prototype has been built, with APV25 readout chips and an embedded microtube, providing efficient low-mass cooling of the whole module with a two-phase flow of or Ar. First pedestal and pulse shape temperature dependencies are presented for this module. We have also built an edgeless test module with two pairs of laser cut sensors, with both angular and parallel cuts with respect to the strips (at pitch). We are studying the efficiency of the microstrip sensors very close () to the physical border of the cut silicon crystal and present here some electrical characteristics. [Copyright &y& Elsevier]

Abstract: We report measurements in a high-energy pion beam of the sensitivity of the edge region in “edgeless” planar silicon pad diode detectors diced through their contact implants. A large surface current on such an edge prevents the normal reverse biasing of the device, but the current can be sufficiently reduced by the use of a suitable cutting method, followed by edge treatment, and by operating the detector at low temperature. The depth of the dead layer at the diced edge is measured to be (12.5±8stat..±6syst.)μm. [Copyright &y& Elsevier]

Abstract: The non-depletion detector operation mode has generally been disregarded as an option in high-energy physics experiments. In this paper, the non-depletion operation is examined by detailed analysis of the electric field distribution and the current pulse response of heavily irradiated silicon (Si) detectors. The previously reported model of double junction in heavily irradiated Si detector is further developed and a simulation of the current pulse response has been performed. It is shown that detectors can operate in a non-depletion mode due to the fact that the value of the electric field in a non-depleted region is high enough for efficient carrier drift. This electric field originates from the current flow through the detector and a consequent drop of the potential across high-resistivity bulk of a non-depleted region. It is anticipated that the electric field in a non-depleted region, which is still electrically neutral, increases with fluence that improves the non-depleted detector operation. Consideration of the electric field in a non-depleted region allows the explanation of the recorded double-peak current pulse shape of heavily irradiated Si detectors and definition of the requirements for the detector operational conditions. Detailed reconstruction of the electric field distribution gives new information on radiation effects in Si detectors. [Copyright &y& Elsevier]

Abstract: Carrier lifetime variations dependent on proton irradiation at fluences in the range from 5×1012 to 1015 cm−2 and γ-ray doses ranging from 50 to 400Mrad were investigated in high-resistivity oxygenated silicon wafers and pad detectors. Fast recombination and slow trapping constituents within recombination transients have been distinguished by combining analyses of excess carrier decays dependent on excitation intensity and temperature, measured using the technique of microwave absorption by free carriers. Difference in defect formation rate and type of defects in the ranges of moderate and highest proton irradiation fluences as well as between γ-ray- and proton-irradiated material have been revealed from the inverse lifetime dependence on irradiation fluence and on temperature. The activation factors of the capture centers have been evaluated from carrier lifetime variations in the range of low and elevated temperatures. [Copyright &y& Elsevier]

Abstract: When processing boron-doped p-type high-resistivity Czochralski Silicon (Cz-Si), the Thermal Donor (TD) generation process can be utilized in order to produce p+/n−/n+ detectors. The last thermal process step, i.e. the sintering of aluminum, is intentionally carried out at the temperature where TDs are created. Due to the generated donors the p-type bulk will eventually be compensated to n-type bulk. With this method it is possible, with low costs and with a process of low thermal budget, to fabricate detectors with high oxygen concentration. Moreover, the full depletion voltage of detectors could be tailored between a wide range from 30V up to almost 1000V by changing heat treatment duration at 400–450°C from 20 to 80min. The Space Charge Sign Inversion (SCSI) in the TD generated devices has been verified by the Transient Current Technique (TCT). The results of 24GeV/c proton irradiation to fluences up to 5×1014 p/cm2 show a very small increase of full depletion voltage. [Copyright &y& Elsevier]

Abstract: We report measurements in a high-energy beam of the sensitivity of the edge region in “edgeless” planar silicon pad diode detectors. The edgeless side of these rectangular diodes is formed by a cut and break through the contact implants. A large surface current on such an edge prevents the normal reverse biasing of this device above the full depletion voltage, but we have shown that the current can be sufficiently reduced by the use of a suitable cutting method, followed by edge treatment, and by operating the detector at a low temperature. A pair of these edgeless silicon diode pad sensors was exposed to the X5 high-energy pion beam at CERN, to determine the edge sensitivity. The signal of the detector pair triggered a reference telescope made of silicon microstrip detector modules. The gap width between the edgeless sensors, determined using the tracks measured by the reference telescope, was then compared with the results of precision metrology. It was concluded that the depth of the dead layer at the diced edge is compatible with zero within the statistical precision of ±8μm and systematic error of ±6μm. [Copyright &y& Elsevier]

Abstract: We have processed pin-diodes and strip detectors on n- and p-type high-resistivity silicon wafers grown by magnetic Czochralski method. The Czochralski silicon (Cz-Si) wafers manufactured by Okmetic Oyj have nominal resistivity of 900Ωcm and 1.9kΩcm for n- and p-type, respectively. The oxygen concentration in these substrates is slightly less than typically in wafers used for integrated circuit fabrication. This is optimal for semiconductor fabrication as well as for radiation hardness. The radiation hardness of devices has been investigated with several irradiation campaigns including low- and high-energy protons, neutrons, γ-rays, lithium ions and electrons. Cz-Si was found to be more radiation hard than standard Float Zone silicon (Fz-Si) or oxygenated Fz-Si. When irradiated with protons, the full depletion voltage in Cz-Si has not exceeded its initial value of 300V even after the fluence of 5×1014 cm−2 1-MeV eq. ncm−2 that equals more than 30 years operation of strip detectors in LHC experiments. [Copyright &y& Elsevier]

Abstract: The PP2PP experiment is one of five experiments at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory, Long Island, New York. It is designed to measure the elastic scattering of protons at = 50–500GeV. The detector consists of silicon strip detectors mounted in Roman Pots and installed in the RHIC ring 60m from the interaction region. During the engineering run of 2002 and physics run of 2003 the detectors were inserted as close as 15 mm from the proton beam. An overview of the experiment and details of the detector design and performance will be presented. [Copyright &y& Elsevier]

In this work, it is shown that the analysis of thermally stimulated currents (TSC) and current transients (CT) at constant temperature can be a suitable tool to study the influence of deep levels on space charge density N(T) in irradiated silicon diodes. In particular, the occurrence of space charge sign inversion (SCSI) can be related to signal discontinuities in TSC and CT measurements. This approach has been adopted in this work to study devices made of standard Float Zone (FZ) and Diffusion Oxygenated Float Zone silicon, irradiated by γ-rays up to a dose of 300 Mrad. Our study shows that all the samples are inverted at 50 K after a low-temperature excitation. Several space charge sign inversions, from positive to negative and vice versa, have been observed between cryogenic and room temperature, and have been related to carriers emission from dominating deep traps. Only standard FZ silicon remains inverted at room temperature after a dose of 300 Mrad. [Copyright &y& Elsevier]

A new spherical grating undulator beamline has been commissioned at the synchrotron radiation source ASTRID in Aarhus. It covers an energy range from 12 to 130 eV with a resolving power of about 15.000. This beamline is combined with an end-station for angle-resolved photoemission. The spectrometer is a 75 mm mean radius hemispherical electron energy analyzer which is mounted on a goniometer within the ultra-high vacuum chamber. The motions of the analyzer and several settings of the beamline are motorized and computerized scans can be performed. The system is in particular well suited for measurements of the electronic structure along arbitrary lines in k→||-space, Fermi surface mapping and studying the polarization dependence of photoemission features. [Copyright &y& Elsevier]

Silicon microstrip detectors will provide the forward tracking in the TOTEM experiment at the LHC. To allow efficient tracking closest to the beam (&ap;1 mm) these detectors should be sensitive up to their physical edge (i.e. edgeless). Edgeless (without guard rings) microstrip planar detectors can be operated at cryogenic temperatures (about 130° K) where leakage currents due to the active edge are drastically reduced. A silicon microstrip prototype, cut perpendicular to the strips, has been tested with a pion beam at CERN to study its efficiency close to the edge by using reference tracks from a simple silicon telescope. Results indicate that the detector measures tracks with good efficiency up to the physical edge of the silicon. [Copyright &y& Elsevier]

The influence of oxygen in silicon on bulk damage effects induced by 60Co-gamma irradiation has been studied in a dose range between 0.2 and 900 Mrad. The detector processing and oxygen enrichment were carried out in a common project by the Institute of Micro-sensors CiS using n-type high-resistivity FZ silicon (3–6 kΩ cm) with 〈1 1 1〉 and 〈1 0 0〉 orientation. Different oxygen concentrations were achieved by diffusion at 1150°C for 24, 48 and 72 h. This report on bulk damage effects is focussed on the observed changes in the reverse current, the effective space charge density Neff extracted from C/V measurements and investigations using the transient current technique. A substantial improvement of radiation hardness concerning the development of the macroscopic properties was found for detectors manufactured on oxygenated material compared to standard material. It will be demonstrated that the change of the effective space charge density as well as the increase of the reverse current can be attributed to the creation of two deep acceptor levels and a shallow donor level. [Copyright &y& Elsevier]

Silicon detectors have been made on oxygenated silicon with the incorporation of thermal donors during the oxidation process based on BNL''s high-temperature long-time (thermal donor) (HTLT(TD)) technology. The initial doping concentration in HTLT(TD) silicon detectors is twice more than that of standard silicon detectors (same starting material, but no HTLT process), with TD being the dominant donor. Standard and HTLT(TD) silicon detectors have been irradiated by 10 MeV protons up to 2.5×1014 p/cm2. It has been found that the increase rate (β) of the space charge concentration (Neff) after space charge sign inversion (SCSI) in HTLT(TD) silicon detectors is about half of that in standard silicon detectors. Further improvement in proton radiation hardness has been observed in terms of the SCSI fluence. The SCSI fluence for HTLT(TD) silicon detectors is more than four times higher than that of standard detectors, although the corresponding ratio of initial space charge concentrations between the two groups of detectors is about two. This result implies that the SCSI is greatly delayed in HTLT(TD) silicon detector compared with silicon detectors with similar initial space charge (all phosphorus) concentration (lower resistivity standard silicon detectors). [Copyright &y& Elsevier]

The cryogenic silicon Beam Tracker of NA60 is the first detector based on the Lazarus effect used in a high-energy physics experiment. It employs single-sided silicon strip sensors of 50 μm pitch operated at a temperature of 130 K. Two tracking stations determine the transverse coordinates of the interaction point at the target with 20 μm resolution, to improve the determination of the offset of secondary vertices. This impact parameter measurement allows NA60 to distinguish between prompt dimuons and muon pairs from D-meson decays. The detector concept and technical feasibility have been demonstrated in beam time periods between 1999 and 2002. [Copyright &y& Elsevier]

This paper describes a novel technique to monitor high-intensity particle beams by means of a semiconductor detector. It consists of cooling a semiconductor detector down to cryogenic temperature to suppress the thermally generated leakage current and to precisely measure the integrated ionization signal. It will be shown that such a device provides very good linearity and a dynamic range wider than is possible with existing techniques. Moreover, thanks to the Lazarus effect, extreme radiation hardness can be achieved providing in turn absolute intensity measurements against precise calibration of the device at low beam flux. [Copyright &y& Elsevier]

The Photo Injector Test facility at DESY Zeuthen (PITZ) was built to develop electron sources for the TESLA Test Facility Free Electron Laser and future linear colliders. The main goal is to study the production of minimum transverse emittance beams with short bunch length at medium charge (∼1 nC). The facility includes a 1.5 cell L-band cavity with coaxial RF coupler, a solenoid for space charge compensation, a laser capable to generate long pulse trains, an UHV photo cathode exchange system, and different diagnostics tools. Besides an overview of the facility, its main components and their commissioning, this contribution will concentrate on the first measurements at PITZ with photoelectrons. This will include measurements of the transverse and longitudinal laser profile, charge and quantum efficiency, momentum and momentum spread, transverse electron beam profiles at different locations and first results on transverse emittance. [Copyright &y& Elsevier]

The Solenoidal Tracker At RHIC-Silicon Vertex Tracker (STAR-SVT) is a three-barrel microvertex detector based upon silicon drift detector (SDD) technology. As designed for the STAR-SVT, (SDDs) are capable of providing unambiguous two-dimensional hit position measurements with resolutions on the order of 20 μm in each coordinate. In addition, a high-resolution energy loss measurement in the three layers of the SVT enables good particle identification. We describe features of the design of the STAR-SVT SDDs and electronics that are motivated by such characteristics. We also detail the mechanical structure, assembly procedures, and performance characteristics of the completed device. [Copyright &y& Elsevier]

We have designed and built a new hodoscope for heavy ion beams consisting of two tracking stations equipped with silicon microstrip detectors operated at 130 K. Preliminary results from tests performed in the high intensity CERN-SPS Pb ion beam show that we were able to detect and identify each incoming ion up to a beam intensity of ∼107 ions/s. The beam profile could be monitored on-line with 50 μm resolution. The detector performed satisfactory even after a dose of 90±40 Grad. [Copyright &y& Elsevier]

The current status of the STAR Silicon Vertex Tracker (SVT) is presented. The performance of the Silicon Drift Detectors (SDD) is discussed. Results for a recent 15 layer SDD tracker which prototypes all components of the SVT are presented. The enhanced physics capabilities of the STAR detector due to the addition of the SVT are addressed. [Copyright &y& Elsevier]

The China Spallation Neutron Source (CSNS) is a high intensity proton accelerator-based facility, and its accelerator complex includes two main parts: a H- linac and a rapid cycling synchrotron (RCS). The RCS accumulates the 80 MeV proton beam, and accelerates it to 1.6 GeV, with a repetition rate of 25 Hz. The beam commissioning of RCS began in May, 2017 and reached the target beam power of 100 kW in February, 2020. The longitudinal beam dynamics study plays the key role in the commissioning. The study and optimization include the synchronicity between the ramping magnet field and the RF system, the mitigation of the high intensity effects to minimize the beam loss and the measurement of the longitudinal dynamics. Through the optimization of the bunch factor, the strong space charge effects with high intensity is mitigated, thus the RCS transmission efficiency arrives mostly at 100 %. The beam distribution is not affected by the phase loop with a new algorithm and the beam loss is smaller than the original one. The beam commissioning in longitudinal plane is reviewed in the paper. • The beam commissioning reached the target beam power of 100 kW. • The synchronicity is optimized between the magnet and the RF cavity. • The strong space charge effects with high intensity is mitigated. • The phase loop with a new algorithm is adopted. [ABSTRACT FROM AUTHOR]