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The development of semiconductor sensors for new particle tracking detectors places increasing limits on sensor characteristics such as uniformity, size and shape of inefficient areas and size of active compared to inactive sensor areas. Accurately assessing these relatively subtle effects requires either measurements in particle beams or the modification of samples to be used in dedicated laser test setups. Active Region Extent Assessment with X-rays (AREA-X) has been developed as an alternative method for the fast, efficient and precise study of the active area of a semiconductor sensor. It uses a monochromatic, micro-focused X-ray beam with a 10–20 keV energy range as provided by several synchrotron beam lines and uses the photo current induced in the sensor to measure the depth of the responsive sensor volume. It can be used to study local inhomogeneities or inefficiencies, the overall extent of the active sensor volume and its shape and its localised application, which makes the need to gather statistics over a large area unnecessary, allowing for fast readout, which enables studies of the sensor behaviour at a range of external parameters, e.g. temperature or applied bias voltage. This paper presents the measurement concept and technical setup of the measurement, results from initial measurements as well as capabilities and limitations of the method.

The ATLAS collaboration is designing the all-silicon Inner Tracker (ITk) that will operate in the HL-LHC replacing the current design. The silicon microstrip sensors for the barrel and the endcap regions in the ITk are fabricated in 6 inch, p-type, float-zone wafers, where large-area strip sensor designs are laid out together with a number of miniature sensors. The radiation tolerance and specific system issues like the need for slim edge of 450 μm have been tested with square shaped sensors intended for the barrel part of the tracker. This work presents the design of the first full size silicon microstrip sensor for the endcap region with a slim edge of 450 μm. The strip endcaps will consist of several wheels with two layers of silicon strip sensors each. The strips have to lie along the azimuthal direction, apart from a small stereo angle rotation (20 mrad on each side, giving 40 mrad total) for measuring the second coordinate of tracks. This stereo angle is built into the strip layout of the sensor and, in order to avoid orphan strips, the sensor edges are inclined by the stereo angle. On top of this, the top and bottom edges are designed as arcs to have equal length strips. Together with the design of this new Stereo Annulus sensor, we will report on the initial measurements of the leakage current as a function of bias voltage, after dicing, and the depletion voltage., The research was supported and financed in part by Canada Foundation for Innovation, the National Science and Engineering Research Council (NSERC) of Canada under the Research and Technology Instrumentation (RTI) grant SAPEQ-2016-00015; the Spanish Ministry of Economy and Competitiveness through the Particle Physics National Program, ref. FPA2015-65652-C4-4-R (MINECO/FEDER, UE), and co-financed with FEDER funds; and USA Department of Energy, Grant DE-SC0010107.

Active silicon detectors built on p-type substrate are a promising technological solution for large area silicon trackers such as those at the High Luminosity LHC, but the radiation hardness of this novel approach has to be evaluated. Active n-in-p strip detector prototypes CHESS2 for ATLAS with different substrate resistivities in the range of 20–1000 Ω cm were irradiated with neutrons and protons up to a fluence of 2 × 1 0 15 n eq cm − 2 and 3 . 6 × 1 0 15 n eq cm − 2 . Charge collection in passive test structures on the chip was evaluated using Edge-TCT and minimum ionising electrons from 90Sr. Results were used to assess radiation hardness of the detector in the given fluence range and to determine parameters of initial acceptor removal in different substrates.

The ATLAS experiment will replace the existing Inner Detector by an all-silicon detector named the Inner Tracker (ITk) for the High Luminosity LHC upgrades. In the outer region of the ITk is the strip detector, which consists of a four layer barrel and six discs to each side of the barrel, with silicon-strip modules as basic units. Each module is composed of a sensor and one or more flex circuits that hold the read-out electronics. In the experiment, the modules are mounted on support structures with integrated power and cooling. The modules are designed with geometries that accommodate the central (barrel) and forward (end-cap) regions, with rectangular sensors in the barrels and wedge shaped sensors in the end-caps. The strips lengths and pitch sizes vary according to the occupancy of the region.

Miniature sensors with external dimensions of 10 mm x 10 mm were produced together with full-size sensors for the innermost ring (R0) of the end-cap part in the upgraded ATLAS inner tracker (ITk). AC- and DC-coupled n-type strips with three different pitches (wide, default and narrow) were processed on high-resistivity p-type FZ silicon substrates by Hamamatsu Photonics. The miniature sensors were irradiated with 70-MeV protons at CYRIC, Tohoku University (Japan) and reactor neutrons at the Jožef Stefan Institute (Slovenia) to three different 1-MeV neutron equivalent fluences: 0.5, 1 and 2 x 1015 n eq cm−2. The upper fluence range exceeds the highest anticipated in the innermost part of the ATLAS ITk-Strips over the HL-LHC lifetime ( ∼ 1.25 × 10 15 n eq cm2). The charge collection in the test sensors was evaluated systematically using a 90Sr β -source and an Alibava analogue readout system at reverse-bias voltages up to 1000 V.

The ATLAS upgrade strip module design has readout flex circuits glued directly on top of the sensor’s active area to facilitate the assembly process and minimize the radiation length. The process requires radiation-hard adhesives compatible with the sensor technology. We report on the studies of the breakdown behavior with miniature versions of the prototype sensors, where candidate adhesives were placed in several locations on top of the sensor, including the strip area, guard ring region, and sensor edge. Thermal cycling tends to attenuate the observed cases of breakdown with glue on top of the guard ring. Glue reaching the sensor edge results in low breakdown voltage if it also covers AC- or DC- pads or bias ring openings. Glue placement on top of guard ring region was performed on a large-format sensor, with generally similar results to the miniature sensor tests, except for a large glue deposition, which resulted in a permanent reduction of the breakdown voltage. Post-irradiation measurements were performed for some of the glues deposited on top of the strip area, without any sign of the early breakdown. To help rank the candidate glue, we studied them with differential scanning calorimetry to find the glass transition and degree of curing.

In preparation for the High Luminosity LHC (HL-LHC) runs, the ATLAS inner detector will be completely replaced with an all silicon Inner Tracker (ITk). Hybrid silicon pixel modules will be used for the innermost tracking layers, and silicon micro-strip detectors will be used the outer layers of the tracker. During the production of the detector, the sensors, readout electronics, and other components will undergo a series of quality control (QC) and quality assurance tests. Defects in the fabrication of the sensors will be flagged early in the manufacturer's and ATLAS QC tests. A study of the influence of sensor defects was performed to assess the characteristics of these defects in completed modules, and whether any defect posed a risk to the operation of the front-end readout electronics. All defects were found to have no impact on the performance of the front-end readout electronics for healthy amplifier channels, and defects that short the coupling between the strip implant and the metal readout electrode were only noticeable for strip leakage currents in excess of 250 nA, beyond the end-of-life currents expected for most sensors at the HL-LHC.

Journal of Instrumentation 15(09), P09004 (2020). doi:10.1088/1748-0221/15/09/P09004, For the Phase-II Upgrade of the ATLAS Detector [1], its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100% silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-250) [2,2] and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests., Published by Inst. of Physics, London

Low Gain Avalanche Detectors (LGADs) are based on a n + + -p + -p-p + + structure where appropriate doping of multiplication layer (p + ) leads to high enough electric fields for impact ionization. Operation of these detectors in harsh radiation environments leads to decrease of gain attributed to the effective acceptor removal in the multiplication layer. In order to cope with that devices were produced where boron was replaced by gallium. The initial radiation hardness studies show a smaller degradation of gain with neutron fluence indicating that gallium is more difficult to displace/deactivate from the lattice site than boron.

The planned High Luminosity Large Hadron Collider is being designed to maximise the physics potential of the LHC with 10 years of operation at instantaneous luminosities of 7.5×10 34 cm ¿2 s ¿1 . A consequence of this increased luminosity is the expected radiation damage requiring the tracking detectors to withstand hadron fluence to over 1×10 15 1 MeV neutron equivalent per cm 2 in the ATLAS Strips system. Fast readout electronics, deploying 130 nm CMOS front-end electronics are glued on top of a silicon sensor to make a module. The radiation hard n-in-p micro-strip sensors used have been developed by the ATLAS ITk Strip Sensor collaboration and produced by Hamamatsu Photonics. A series of tests were performed at the DESY-II test beam facility to investigate the detailed performance of a strip module with both 2.5 cm and 5 cm length strips before irradiation. The DURANTA telescope was used to obtain a pointing resolution of 2 ¿m, with an additional pixel layer installed to improve timing resolution to ~25 ns. Results show that prior to irradiation a wide range of thresholds (0.5¿2.0 fC) meet the requirements of a noise occupancy less than 1×10 ¿3 and a hit efficiency greater than 99%. © 2018, The research was supported and financed in part by Canada Foundation for Innovation, the National Science and Engineering Research Council (NSERC) of Canada under the Research and Technology Instrumentation (RTI) grant SAPEQ-2016-00015; the National Key Program for S&T Research and Development (Grant No. 2016YFA0400101) of China and CAS-Helmholtz Joint Research Group; theMinistry of Education, Youth and Sports of the Czech Repub87lic coming from the projectLM2015058 - Research infrastructure for experiments at CERN; the DST/NRF in South 88 Africa; the Spanish Ministry of Economy and Competitiveness through the Particle Physics National Program, ref. 89 FPA2015-65652-C4-4-R (MINECO/FEDER, UE), and co-financed with FEDER funds; the UK’s Science and Tech90nology Facilities Council; USA Department of Energy, Grant DE-SC0010107; and the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement no. 654168. The measurements leading to these results have been performed at the Test Beam Facility at DESY Hamburg (Germany), a member of the Helmholtz Association (HGF).

The ATLAS experiment is going to replace the current Inner Detector with an all new inner tracker (ITk) in the ATLAS detector for HL-LHC at CERN. Silicon strip detectors cover the outer layers of the barrel and the endcap sections. We have designed and fabricated a prototype single-sided n + -in-p AC-coupled silicon strip sensor for the outer barrel layer with long strips (LS), ATLAS17LS. It is of the maximum allowable size to fit in a 6-in. silicon wafer, with an outer dimension of 9.80 (width) × 9.76 (length) cm 2 . The sensor features two rows of LS strip segments, 4.83 cm strip length per segment, a strip pitch of 75.5 μ m , and a slim edge design. We have implemented technology for high voltage operation of up to 1000 V, with a good signal collection after irradiation fluence of 5.6 × 1014 n eq ∕ cm 2 at the end of HL-LHC operation. We had two objectives for the ATLAS17LS fabrication: qualification of the sensor design and fabrication quality, and providing an adequate number of the sensors for prototyping the building blocks of the strip detector. The sensors were fabricated in 3 batches by HPK with standard wafers from the foundry (320 μ m physical thickness). Additional 10 sensors were fabricated with a thinner active thickness of 240 μ m to investigate the influence of active thickness on charge collection. Another additional 5 sensors, with special passivation to investigate the influence of passivation on humidity sensitivity. The visual inspection of fabricated sensors revealed an inadequacy that the designed metal width of 10 μ m was too narrow. The initial measurements by the vendor showed that the sensors fulfilled the specifications: onset voltages of Microdischarge V M D above the operation voltage V O P (700 V for the 1st and 2nd batches; 500 V for the 3rd batch, which has improved the yield), leakage currents of 0.1 μ A/cm 2 at V O P , full depletion voltages V F D 330 V, and rates of bad strips 1%.

The high luminosity upgrade of the Large Hadron Collider, foreseen for 2027, requires the replacement of the ATLAS Inner Detector with a new all-silicon Inner Tracker (ITk). The expected total integrated luminosity of 4000 fb − 1 means that the strip part of the ITk detector will be exposed to a large radiation fluence of up to Φ e q = 1.6 × 1015 1 MeV n e q /cm and an ionizing dose of 0.66 MGy, including a safety factor of 1.5. Radiation-hard n + -in-p micro-strip sensors for use in the ITk have been developed by the ATLAS ITk Strip Sensor collaboration and produced by Hamamatsu Photonics K.K. In this paper, the results obtained from the electrical characterization of the latest barrel ATLAS17LS sensor prototype, before and after irradiation, are shown. Surface properties of the long-strip barrel, full-sized and miniature sensors have been studied before and after proton, neutron and gamma irradiation up to the maximal fluences and radiation doses specified for the ITk Strip tracker. Sensors have been irradiated by protons at CYRIC, Tohoku University (Japan), the Proton Irradiation Facility at CERN, Karlsruhe Inst. Tech. (Germany) and at the University of Birmingham (UK), by neutrons from the Ljubljana TRIGA reactor (Slovenia) and by gamma rays from the 60 Co source in UJP Praha (Czech Republic). It has been verified that the surface radiation damage does not influence the sensor functionality. The breakdown voltage is well above the maximum operational voltage. All the tested surface parameters, such as the inter-strip resistance and capacitance, coupling capacitance and bias resistance satisfy the ATLAS ITk specifications for strip sensors.

The inner tracker of the ATLAS detector is scheduled to be replaced by a completely new silicon-based inner tracker (ITk) for the Phase-II of the CERN LHC (HL-LHC). The silicon strip detector covers the volume 40 R 100 cm in the radial and | z | 300 cm in the longitudinal directions. The silicon sensors for the detector will be fabricated using the n + -on-p 6-inch wafer technology, for a total of 22,000 wafers. Intensive studies were carried out on the final prototype sensors ATLAS17LS fabricated by Hamamatsu Photonics (HPK). The charge collection properties were examined using penetrating 90Sr β -rays and the ALIBAVA fast readout system for the miniature sensors of 1 cm × 1 cm in area. The samples were irradiated by protons in the 27 MeV Birmingham Cyclotron, the 70 MeV CYRIC at Tohoku University, and the 24 GeV CERN-PS, and by neutrons at Ljubljana TRIGA reactor for fluence values up to 2 × 1015 n eq /cm 2 . The change in the charge collection with fluence was found to be similar to the previous prototype ATLAS12, and acceptable for the ITk. Sensors with two active thicknesses, 300 μ m (standard) and 240 μ m (thin), were compared and the difference in the charge collection was observed to be small for bias voltages up to 500 V. Some samples were also irradiated with gamma radiation up to 2 MGy, and the full depletion voltage was found to decrease with the dose. This was caused by the Compton electrons due to the 60Co gamma radiation. To summarize, the design of the ATLAS17LS and technology for its fabrication have been verified for implementation in the ITk. We are in the stage of sensor pre-production with the first sensors already delivered in January of 2020.

We report on measurements on Ultra-Fast Silicon Detectors (UFSD) which are based on Low-Gain Avalanche Detectors (LGAD). They are n-on-p sensors with internal charge multiplication due to the presence of a thin, low-resistivity diffusion layer below the junction, obtained with a highly doped implant. We have performed several beam tests with LGAD of different gain and report the measured timing resolution, comparing it with laser injection and simulations. For the 300 μm thick LGAD, the timing resolution measured at test beams is 120 ps while it is 57 ps for IR laser, in agreement with simulations using Weightfield2. For the development of thin sensors and their readout electronics, we focused on the understanding of the pulse shapes and point out the pivotal role the sensor capacitance plays.

The radiation hardness and thermal stability of the electrical characteristics of atomic layer deposited Al2O3 layers to be used as passivation films for silicon radiation detectors with slim edges are investigated. To directly measure the interface charge and to evaluate its change with the ionizing dose, metal-oxide-silicon (MOS) capacitors implementing differently processed Al2O3 layers were fabricated on p-type silicon substrates. Qualitatively similar results are obtained for degradation of capacitance-voltage and current-voltage characteristics under gamma and proton irradiations up to equivalent doses of 30 Mrad and 21.07 Mrad, respectively. While similar negative charge densities are initially extracted for all non-irradiated capacitors, superior radiation hardness is obtained for MOS structures with alumina layers grown with H2O instead of O3 as oxidant precursor. Competing effects between radiation-induced positive charge trapping and hydrogen release from the H2O-grown Al2O3 layers may explain their higher radiation resistance. Finally, irradiated and non-irradiated MOS capacitors with differently processed Al2O3 layers have been subjected to thermal treatments in air at temperatures ranging between 100 °C and 200 °C and the thermal stability of their electrical characteristics has been evaluated. Partial recovery of the gamma-induced degradation has been noticed for O3-grown MOS structures. This can be explained by a trapped holes emission process, for which an activation energy of 1.38 ± 0.15 eV has been extracted.

The production of large area sensors is one of the main challenges that the ATLAS collaboration faces for the new Inner-Tracker full-silicon detector. During the prototype fabrication phase for the High Luminosity Large Hadron Collider upgrade, several ATLAS institutes observed indications of humidity sensitivity of large area sensors, even at relative humidities well below the dew point. Specifically, prototype Barrel and End-Cap silicon strip sensors fabricated in 6-inch wafers manifest a prompt decrease of the breakdown voltage when operating under high relative humidity, adversely affecting the performance of the sensors. In addition to the investigation of these prototype sensors, a specific fabrication batch with special passivation is also studied, allowing for a deeper understanding of the responsible mechanisms. This work presents an extensive study of this behaviour on large area sensors. The locations of the hotspots at the breakdown voltage at high humidity are revealed using different infrared thermography techniques. Several palliative treatments are attempted, proving the influence of sensor cleaning methods, as well as baking, on the device performance, but no improvement on the humidity sensitivity was achieved. Furthermore, a study of the incidence of the sensitivity in different batches is also presented, introducing a hypothesis of the origins of the humidity sensitivity associated to the sensor edge design, together with passivation thickness and conformity. Several actions to be taken during sensor production and assembly are extracted from this study, in order to minimize the impact of humidity sensitivity on the performance of large area silicon sensors for High Energy Physics experiments.

The planned upgrade of the Large Hadron Collider, the HL-LHC, requires the development of improved tracking silicon sensors for the main CERN experiments. These devices must fulfil the specifications established by the different detectors for the adverse HL-LHC working conditions, in order to guarantee the proper performance of the tracking systems during the lifetime of the experiments. In the framework of the ATLAS Inner-Tracker sensor Market Survey, a prototype strip sensor layout has been designed by the collaboration, and fabricated in 6-inch substrates by Infineon Technologies AG. This work presents a set of test structures included in this prototype, capable to evaluate key device and technological parameters as strip implant resistivity, bias resistance, coupling capacitance, surface currents, or the influence of the sensor edge design in device breakdown voltage. A complete analysis of these parameters before and after proton and gamma irradiations, up to fluences and doses similar to the ones expected in the future HL-LHC experiments, is presented. This study shows the relevance of microelectronic test structures in the development of technologies of tracking silicon sensors for High Energy Physics experiments.

We report on design and performance of new strip sensors for the Heavy Photon Search (HPS) experiment. The sensors feature a slim edge implementation using the Scribe–Cleave–Passivate (SCP) method. The slim edge design has allowed the introduction of a new layer closer to the target, which increased the tracking acceptance and vertex precision, improving physics reach of the experiment. We describe the production, testing, and operational experience with the new sensors.

Journal of Instrumentation 14(03), P03024 - P03024 (2019). doi:10.1088/1748-0221/14/03/P03024, For the Phase-II Upgrade of the ATLAS detector at CERN, the current ATLAS Inner Detector will be replaced with the ATLAS Inner Tracker (ITk). The ITk will be an all-silicon detector, consisting of a pixel tracker and a strip tracker. Sensors for the ITk strip tracker are required to have a low leakage current up to bias voltages of −500 V to maintain a low noise and power dissipation. In order to minimise sensor leakage currents, particularly in the high-radiation environment inside the ATLAS detector, sensors are foreseen to be operated at low temperatures and to be manufactured from wafers with a high bulk resistivity of several kΩ·cm. Simulations showed the electric field inside sensors with high bulk resistivity to extend towards the sensor edge, which could lead to increased surface currents for narrow dicing edges. In order to map the electric field inside biased silicon sensors with high bulk resistivity, three diodes from ATLAS silicon strip sensor prototype wafers were studied with a monochromatic, micro-focused X-ray beam at the Diamond Light Source (Didcot, U.K.). For all devices under investigation, the electric field inside the diode was mapped and its dependence on the applied bias voltage was studied., Published by Inst. of Physics, London

A novel microstrip sensor geometry, the stereo annulus, has been developed for use in the end-cap of the ATLAS experiment’s strip tracker upgrade at the HL-LHC. Its first implementation is in the ATLAS12EC sensors, a large-area, radiation-hard, single-sided, AC-coupled, n + -in-p design produced by the ITk Strip Sensor Collaboration and fabricated by Hamamatsu Photonics in early 2017. The results of the initial testing of two ATLAS12EC batches are presented here with a comparison to specification. The potential of the new sensor shape to reinvigorate endcap strip tracking is explained and its effects on sensor performance are isolated by comparing the bulk mechanical and electrical properties of the new sensor to the previous iteration of prototype, the conventional barrel ATLAS12A sensor. The surface properties of the new sensor are evaluated for full-size unirradiated sensors as well as for mini sensors unirradiated and irradiated with protons up to a fluence of 2 . 2 × 1 0 15 neq cm−2. The results show that the new stereo annulus ATLAS12EC sensors exhibit excellent performance and the expected irradiation evolution.

For the High-Luminosity Upgrade of the Large Hadron Collider at CERN, the ATLAS Inner Detector will be replaced with a new, all-silicon tracker (ITk). In order to minimise the amount of material in the ITk, circuit boards with readout electronics will be glued onto the active area of the sensor. Several adhesives, investigated to be used for the construction of detector modules, were found to become fluorescent when exposed to UV light. These adhesives could become a light source in the high-radiation environment of the ATLAS detector. The effect of fluorescent material covering the sensor surface in a high-radiation environment has been studied for a silicon micro-strip sensor using a micro-focused X-ray beam. By positioning the beam parallel to the sensor surface and pointing it both inside the sensor and above the sensor surface inside the deposited glue, the sensor responses from direct hits and fluorescence can be compared with high precision. This contribution presents a setup to study the susceptibility of silicon strip sensors to light contamination from fluorescent materials and shows their impact on the noise and fake signal rate of a sensor operated in a high-radiation environment.

11th International 'Hiroshima' Symposium on the Development and Application of Semiconductor Tracking Detectors (HSTD-11), Naha, Japan, 11 Dec 2017 - 15 Dec 2017; Nuclear instruments & methods in physics research / A 924, 116 - 119 (2018). doi:10.1016/j.nima.2018.06.085, For the Phase-II Upgrade of the ATLAS detector~\cite{ATLAS}, a new, all-silicon tracker will be constructed in order to cope with the increased track density and radiation level of the High-Luminosity Large Hadron Collider. While silicon strip sensors are designed to minimise the fraction of dead material and maximise the active area of a sensor, concessions must be made to the requirements of operating a sensor in a particle physics detector. Sensor geometry features like the punch-through protection deviate from the standard sensor architecture and thereby affect the charge collection in that area.In order to study the signal collection of n$^{+}$-p$^{-}$-p$^{+}$ silicon strip sensors over their punch-through-protection area, ATLAS silicon strip sensors were scanned with a micro-focused X-ray beam at the Diamond Light Source. Due to the highly focused X-ray beam ($2\times3µ\text{m}^2$) and the short average path length of an electron after interaction with an X-ray photon ($\leq2µ\text{m}$), local signal collection in different sensor areas can be studied with high resolution.This study presents results of high resolution 2D-scans of the punch-through protection region of ATLAS silicon micro-strip sensors, showing how far the strip signal collection area extends toward the bias ring and how the region is affected by radiation damage., Published by North-Holland Publ. Co., Amsterdam

The Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experiment's technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in the e$^+$e$^-$ invariant mass spectrum, above the trident background or as a narrow invariant mass peak with a decay vertex displaced from the production target, so charged particle tracking and vertexing are needed for its detection. In the HPS Test Run, charged particles are measured with a compact forward silicon microstrip tracker inside a dipole magnet. Electromagnetic showers are detected in a PbW0$_{4}$ crystal calorimeter situated behind the magnet, and are used to trigger the experiment and identify electrons and positrons. Both detectors are placed close to the beam line and split top-bottom. This arrangement provides sensitivity to low-mass heavy photons, allows clear passage of the unscattered beam, and avoids the spray of degraded electrons coming from the target. The discrimination between prompt and displaced e$^+$e$^-$ pairs requires the first layer of silicon sensors be placed only 10~cm downstream of the target. The expected signal is small, and the trident background huge, so the experiment requires very large statistics. Accordingly, the HPS Test Run utilizes high-rate readout and data acquisition electronics and a fast trigger to exploit the essentially 100% duty cycle of the CEBAF accelerator at JLab., Comment: Revised version to match published version, 16 pages, 18 figures, published in Nuclear Instruments and Methods in Physics Research Section A, editor: Per Hansson Adrian

Low Gain Avalanche Detectors (LGAD) are based on a n++-p+-p-p++ structure where an appropriate doping of the multiplication layer (p+) leads to high enough electric fields for impact ionization. Gain factors of few tens in charge significantly improve the resolution of timing measurements, particularly for thin detectors, where the timing performance was shown to be limited by Landau fluctuations. The main obstacle for their operation is the decrease of gain with irradiation, attributed to effective acceptor removal in the gain layer. Sets of thin sensors were produced by two different producers on different substrates, with different gain layer doping profiles and thicknesses (45, 50 and 80 μm). Their performance in terms of gain/collected charge and leakage current was compared before and after irradiation with neutrons and pions up to the equivalent fluences of 5⋅1015 cm−2. Transient Current Technique and charge collection measurements with LHC speed electronics were employed to characterize the detectors. The thin LGAD sensors were shown to perform much better than sensors of standard thickness (∼300 μm) and offer larger charge collection with respect to detectors without gain layer for fluences <2⋅1015 cm−2. Larger initial gain prolongs the beneficial performance of LGADs. Pions were found to be more damaging than neutrons at the same equivalent fluence, while no significant difference was found between different producers. At very high fluences and bias voltages the gain appears due to deep acceptors in the bulk, hence also in thin standard detectors. Low Gain Avalanche Detectors (LGAD) are based on a n ++ -p + -p-p ++ structure where an appropriate doping of the multiplication layer (p + ) leads to high enough electric fields for impact ionization. Gain factors of few tens in charge significantly improve the resolution of timing measurements, particularly for thin detectors, where the timing performance was shown to be limited by Landau fluctuations. The main obstacle for their operation is the decrease of gain with irradiation, attributed to effective acceptor removal in the gain layer. Sets of thin sensors were produced by two different producers on different substrates, with different gain layer doping profiles and thicknesses (45, 50 and 80 μ m). Their performance in terms of gain/collected charge and leakage current was compared before and after irradiation with neutrons and pions up to the equivalent fluences of 5⋅1015 cm −2 . Transient Current Technique and charge collection measurements with LHC speed electronics were employed to characterize the detectors. The thin LGAD sensors were shown to perform much better than sensors of standard thickness ( ∼ 300 μ m) and offer larger charge collection with respect to detectors without gain layer for fluences

In this paper we report on the timing resolution of the first production of 50 micro-meter thick Ultra-Fast Silicon Detectors (UFSD) as obtained in a beam test with pions of 180 GeV/c momentum. UFSD are based on the Low-Gain Avalanche Detectors (LGAD) design, employing n-on-p silicon sensors with internal charge multiplication due to the presence of a thin, low-resistivity diffusion layer below the junction. The UFSD used in this test belongs to the first production of thin (50 {\mu}m) sensors, with an pad area of 1.4 mm2. The gain was measured to vary between 5 and 70 depending on the bias voltage. The experimental setup included three UFSD and a fast trigger consisting of a quartz bar readout by a SiPM. The timing resolution, determined comparing the time of arrival of the particle in one or more UFSD and the trigger counter, for single UFSD was measured to be 35 ps for a bias voltage of 200 V, and 26 ps for a bias voltage of 240 V, and for the combination of 3 UFSD to be 20 ps for a bias voltage of 200 V, and 15 ps for a bias voltage of 240 V., Comment: 7 pages, 8 figures, 1 table, Subm. to NIM A

We have been developing a novel radiation-tolerant n+-in-p silicon microstrip sensor for very high radiation environments, aiming for application in the high luminosity large hadron collider. The sensors are fabricated in 6 in., p-type, float-zone wafers, where large-area strip sensor designs are laid out together with a number of miniature sensors. Radiation tolerance has been studied with ATLAS07 sensors and with independent structures. The ATLAS07 design was developed into new ATLAS12 designs. The ATLAS12A large-area sensor is made towards an axial strip sensor and the ATLAS12M towards a stereo strip sensor. New features to the ATLAS12 sensors are two dicing lines: standard edge space of 910 μm and slim edge space of 450 μm, a gated punch-through protection structure, and connection of orphan strips in a triangular corner of stereo strips. We report the design of the ATLAS12 layouts and initial measurements of the leakage current after dicing and the resistivity of the wafers.

Detectors proposed for the International Linear Collider (ILC) incorporate a tungsten sampling calorimeter (`BeamCal') intended to reconstruct showers of electrons, positrons and photons that emerge from the interaction point of the collider with angles between 5 and 50 milliradians. For the innermost radius of this calorimeter, radiation doses at shower-max are expected to reach 100 MRad per year, primarily due to minimum-ionizing electrons and positrons that arise in the induced electromagnetic showers of e+e- `beamstrahlung' pairs produced in the ILC beam-beam interaction. However, radiation damage to calorimeter sensors may be dominated by hadrons induced by nuclear interactions of shower photons, which are much more likely to contribute to the non-ionizing energy loss that has been observed to damage sensors exposed to hadronic radiation. We report here on the results of SLAC Experiment T-506, for which several different types of silicon diode sensors were exposed to doses of radiation induced by showering electrons of energy 3.5-10.6 GeV. By embedding the sensor under irradiation within a tungsten radiator, the exposure incorporated hadronic species that would potentially contribute to the degradation of a sensor mounted in a precision sampling calorimeter. Depending on sensor technology, efficient charge collection was observed for doses as large as 220 MRad., Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS13), Tokyo, Japan, 11-15 November 2013

AC-coupled silicon strip sensors can be damaged in case of a beam loss due to the possibility of a large charge accumulation in the bulk, developing very high voltages across the coupling capacitors which can destroy them. Punch-through structures are currently used to avoid this problem helping to evacuate the accumulated charge as large voltages are developing. Nevertheless, previous experiments, performed with laser pulses, have shown that these structures can become ineffective in relatively long strips. The large value of the implant resistance can effectively isolate the “far” end of the strip from the punch-through structure leading to large voltages. We present here our developments to fabricate low-resistance strip sensors to avoid this problem. The deposition of a conducting material in contact with the implants drastically reduces the strip resistance, assuring the effectiveness of the punch-through structures. First devices have been fabricated with this new technology. Initial results with laser tests show the expected reduction in peak voltages on the low resistivity implants. Other aspects of the sensor performance, including the signal formation, are not affected by the new technology.

In cases such as that of the proposed International Linear Collider (ILC), for which the beam-delivery and detector-occupancy characteristics permit a long shaping-time readout of the microstrip sensors, it is possible to envision long ( ∼ 1 meter) daisy-chained ‘ladders’ of fine-pitch sensors read out by a single front-end amplifier. In this study, a long shaping-time ( ∼ 2 μ sec ) front-end amplifier has been used to measure readout noise as a function of detector load. Comparing measured noise to that expected from lumped and distributed models of the load network, it is seen that network effects significantly mitigate the amount of readout noise contributed by the detector load. Further reduction in noise is demonstrated for the case that the sensor load is read out from its center rather than its end.

All silicon wafers are singulated into individual chips after device processing (front-end) and before packaging. Silicon wafer singulation is dominated by blade- and laser-dicing techniques, both leave some damage. We are using scribing and cleaving to singulate silicon radiation detectors. Scribing and cleaving is known to leave almost damage free sidewalls when applied to III–V compound semiconductors. The technique is not well developed for dicing silicon devices. We used silicon sensors working in a full depletion mode to determine the damage from different scribing techniques (laser-, diamond, and etch-scribing). Etch-scribing shows very low leakage currents and enables cuts at the edge of the active area of the sensor/die. Furthermore, the leakage currents for laser- and diamond-scribed devices can be reduced by a gaseous sidewall etch step.

Silicon detectors normally have an inactive region along the perimeter of the sensor. In this paper we describe a “scribe, cleave, and passivate” (SCP) technique for the fabrication of slim edges in a post processing with finished detectors. The scribing was done by laser-scribing and etching. After scribing and cleaving steps, the sidewalls are passivated with a dielectric. We present results for n- and p-type sensors with different sidewall passivations. The leakage current depends strongly on the type of sidewall passivation. An alumina passivation leads to very low leakage currents for p-type sensors because of a negative interface charge. For n-type sensors, a hydrogenated silicon nitride shows the lowest leakage currents. Furthermore, we applied the technique to large area n-type single-sided strip detectors (cleaving length up to 3.5 cm).

The effectiveness of punch-through protection (PTP) structures on n-on-p AC-coupled silicon strip detectors using pulses from a 1064 nm IR laser, which mimics beam accidents, is investigated. The voltages on the strip implants are measured as a function of the bias voltage and incoming particle flux. We present a 4-resistor model to describe the sensor after large particle fluxes, which is then used to characterize the effectiveness of PTP structures. The effectiveness of PTP structures is presented in terms of total strip implant to bias rail length, type of surface treatment used for strip isolation, coverage of the polysilicon bias resistor, and radiation damage from protons, neutrons and pions.

Requirements of HEP experiments lead to highly integrated systems with many electrical, mechanical and thermal constraints. A complex performance optimisation is therefore required. High-speed data transmission lines are designed using copper-polyimide flexible bus tapes rather than cable harnesses to minimise radiation length. Methods to improve the signal integrity of point-to-point links and multi-drop configurations in an ultra-low-mass system are described. FEA calculations are an essential guide to the optimisation of a tape design which supports data rates of 640 Mbps for point-to-point links over a length of up to 1.4 m, as well as 160 Mbps for multi-drop configuration. The designs were validated using laboratory measurements of S-parameters and direct bit error ratio tests.

CHESS-2 (CMOS HV Evaluation for Strip Sensors) is a novel ASIC strip architecture designed to investigate the feasibility of using HV-CMOS MAPS (Monolithic Active Pixel Sensors) as alternative sensors for the ATLAS Phase-II Strip Tracker Upgrade. The ASIC is optimized for signal processing, hit pixel position encoding and readout. CHESS-2 includes three independent groups of 128 strips composed of 32 pixels each. The pixel includes a charge sensitive amplifier and the first stage of a comparator inside the collecting well. The second stage, the configuration, the encoding and the readout sections are placed at the periphery of the strips. A novel “fast skip” hit encoding logic identifies the first 8 hit pixel positions with a single-bunch time resolution (25 ns) and sends the data to a fast readout circuitry for serialization and transmission on 14 LVDS channels at 320 MHz. Several substrate resistivity variants have been fabricated for a full characterization of the performance aspects.

The design and technology of the silicon strip detector modules for the Semiconductor Tracker (SCT) of the ATLAS experiment have been finalised in the last several years. Integral to this process has been the measurement and verification of the tracking performance of the different module types in test beams at the CERN SPS and the KEK PS. Tests have been performed to explore the module performance under various operating conditions including detector bias voltage, magnetic field, incidence angle, and state of irradiation up to 3×1014 protons per square centimetre. A particular emphasis has been the understanding of the operational consequences of the binary readout scheme. © 2004 Elsevier B.V. All rights reserved.

Charge collection properties of particle detectors made in HV-CMOS technology were investigated before and after irradiation with reactor neutrons. Two different sensor types were designed and processed in 180 and 350 nm technology by AMS. Edge-TCT and charge collection measurements with electrons from 90Sr source were employed. Diffusion of generated carriers from undepleted substrate contributes significantly to the charge collection before irradiation, while after irradiation the drift contribution prevails as shown by charge measurements at different shaping times. The depleted region at a given bias voltage was found to grow with irradiation in the fluence range of interest for strip detectors at the HL-LHC. This leads to large gains in the measured charge with respect to the one before irradiation. The increase of the depleted region was attributed to removal of effective acceptors. The evolution of depleted region with fluence was investigated and modeled. Initial studies show a small effect of short term annealing on charge collection.

Topical Workshop on Electronics for Particle Physics 2015, TWEPP 2015, Lisbon, Portugal, 28 Sep 2015 - 2 Oct 2015 ; Journal of Instrumentation 1611(02), C02005(2016). doi:10.1088/1748-0221/11/02/C02005, The LHC luminosity upgrade, known as the High Luminosity LHC (HL-LHC), will require the replacement of the existing silicon strip tracker and the transistion radiation tracker. Although a baseline design for this tracker exists the ATLAS collaboration and other non-ATLAS groups are exploring the feasibility of using CMOS Monolithic Active Pixel Sensors (MAPS) which would be arranged in a strip-like fashion and would take advantage of the service and support structure already being developed for the upgrade. Two test devices made with the AMS H35 process (a High voltage or HV CMOS process) have been subjected to various radiation environments and have performed well. The results of these tests are presented in this paper., Published by Inst. of Physics, London

We have tested the effectiveness of punch-through protection (PTP) structures on n-on-p AC-coupled Silicon strip detectors using pulses from an 1064 nm IR laser, which simulate beam accidents. The voltages on the strips are measured as a function of the bias voltage and compared with the results of DC I – V measurements, which are commonly used to characterize the PTP structures. We find that the PTP structures are only effective at very large currents (several mA), and clamp the strips to much larger voltages than assumed from the DC measurements. We also find that the finite resistance of the strip implant compromises the effectiveness of the PTP structures.

Using a discrete RC network with characteristics approximating those of a high-precision silicon microstrip sensor, we have explored the use of resistive charge division to estimate the position of charge deposition in the direction parallel to the length of the sensor strips. For an electrode with distributed resistance and capacitance of 600 k Ω and 12.5 pF, respectively (similar to values expected for a 10 cm long resistive silicon microstrip), we estimate the fractional resolution to be ±6.1% of the length of the sensor. We find this value to be independent of resistance, to depend weakly on strip capacitance, and to apply for both isolated single electrodes as well as sensors with multiple parallel electrodes with significant capacitive coupling between electrodes.

The ATLAS collaboration R&D group “Development of n-in-p Silicon Sensors for very high radiation environment” has developed single-sided p-type 9.75 cm×9.75 cm sensors with an n-type readout strips having radiation tolerance against the 1015 1-MeV neutron equivalent (neq)/cm2 fluence expected in the Super Large Hadron Collider. The compiled results of an evaluation of the bulk and strip parameter characteristics of 19 new non-irradiated sensors manufactured by Hamamatsu Photonics are presented in this paper. It was verified in detail that the sensors comply with the technical specifications required before irradiation. The reverse bias voltage dependence of various parameters, frequency dependence of tested capacitances, and strip scans of more than 23,000 strips as a test of parameter uniformity and strip quality over the whole sensor area have been carried out at Stony Brook University, Cambridge University, University of Geneva, and Academy of Sciences of CR and Charles University in Prague. No openings, shorts, or pinholes were observed on all tested strips, confirming the high quality of sensors made by Hamamatsu Photonics.

We present spectra of high-redshift supernovae (SNe) that were taken with the Subaru low resolution optical spectrograph, FOCAS. These SNe were found in SN surveys with Suprime-Cam on Subaru, the CFH12k camera on the Canada-France-Hawaii Telescope (CFHT), and the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). These SN surveys specifically targeted z>1 Type Ia supernovae (SNe Ia). From the spectra of 39 candidates, we obtain redshifts for 32 candidates and spectroscopically identify 7 active candidates as probable SNe Ia, including one at z=1.35, which is the most distant SN Ia to be spectroscopically confirmed with a ground-based telescope. An additional 4 candidates are identified as likely SNe Ia from the spectrophotometric properties of their host galaxies. Seven candidates are not SNe Ia, either being SNe of another type or active galactic nuclei. When SNe Ia are observed within a week of maximum light, we find that we can spectroscopically identify most of them up to z=1.1. Beyond this redshift, very few candidates were spectroscopically identified as SNe Ia. The current generation of super red-sensitive, fringe-free CCDs will push this redshift limit higher., 19 pages, 26 figures. PASJ in press. see http://www.supernova.lbl.gov/2009ClusterSurvey/ for additional information pertaining to the HST Cluster SN Survey

This paper reports on the first characterization of double sided 3D silicon radiation pixel detectors with slim edges. These detectors consist of a three-dimensional array of electrodes that penetrate into the detector bulk with the anode and cathode electrodes etched from opposite sides of the substrate. Different detectors were post-processed using the scribe-cleave-passivate (SCP) technology to make “slim edge” sensors. These sensors have only a minimal amount of inactive peripheral region, for the benefit of the construction of large-area tracker and imaging systems. The target application for this work is the use of 3D slim edge detectors for the ATLAS Forward Physics (AFP) CERN Project, where pixel detectors for position resolution and timing detectors for removal of pile up protons, will be placed as close as possible to the beam to detect diffractive protons at 220 m on either side of the ATLAS interaction point. For this reason the silicon areas should feature the narrowest possible insensitive zone on the sensor edge closest to the beam and withstand high nonuniform irradiation fluences.

Prior to 1950 nearly all sound recordings were made on mechanical media such as wax, foil, shellac, lacquer, and plastic. Some of these older recordings contain material of great historical value or interest but are damaged, decaying, or now considered too delicate to play. Archives seek to preserve and also create broad access to their collections. An ongoing effort at Berkeley Lab has applied methods of optical metrology and image processing to reconstruct sound stored on these mechanical carriers. This approach was inspired by the use of precision optical metrology to align and fabricate silicon tracking arrays for high-energy physics experiments and by track finding and fitting data analysis methods. The technology has matured to the point that an optical metrology system for sound restoration has been designed and built for the Library of Congress. (c) 2007 Elsevier B.V. All rights reserved.

A further development of a new technological solution to improve the beam-loss protection of silicon strip sensors used in large High Energy Physics experiments is presented. Previous studies show that the high strip resistance limits the beneficial effect of full Punch-Through protection (PTP) structures to the area near the structures. In our approach, we extended the PTP protection to the full active area of the sensor by lowering the strip resistance. This is achieved by the addition of a low-resistivity layer connected along the whole strip implant. We have previously demonstrated that such sensors performed as expected, and that other sensor performance factors are not compromised due to the technological modification. The current studies are focused on two aspects of practical application: manufacturability of the sensors with high yield, and their radiation tolerance. To that extend we have made devices with alternative methods of making low-resistivity layers that with better technological performance, and we have irradiated them with protons in the range expected for upgraded ATLAS strips system. The results show that the sensors fabricated with these alternative technological methods remain within specs and that the strip resistance is properly reduced. On the other hand, radiation does not affect the reduced strip resistance.

We present measurements of \Omega_m and \Omega_{\Lambda} from a blind analysis of 21 high-redshift supernovae using a new technique (CMAGIC) for fitting the multi-color lightcurves of Type Ia supernovae, first introduced in Wang et al. (2003). CMAGIC takes advantage of the remarkably simple behavior of Type Ia supernovae on color-magnitude diagrams, and has several advantages over current techniques based on maximum magnitudes. Among these are a reduced sensitivity to host galaxy dust extinction, a shallower luminosity-width relation, and the relative simplicity of the fitting procedure. This allows us to provide a cross check of previous supernova cosmology results, despite the fact that current data sets were not observed in a manner optimized for CMAGIC. We describe the details of our novel blindness procedure, which is designed to prevent experimenter bias. The data are broadly consistent with the picture of an accelerating Universe, and agree with a flat Universe within 1.7\sigma, including systematics. We also compare the CMAGIC results directly with those of a maximum magnitude fit to the same SNe, finding that CMAGIC favors more acceleration at the 1.6\sigma level, including systematics and the correlation between the two measurements. A fit for w assuming a flat Universe yields a value which is consistent with a cosmological constant within 1.2\sigma.

We present a novel technique for fitting restframe I-band light curves on a data set of 42 Type Ia supernovae (SNe Ia). Using the result of the fit, we construct a Hubble diagram with 26 SNe from the subset at 0.01< z

Audio information stored in the undulations of grooves in a medium such as a phonograph record may be reconstructed, with no contact, by measuring the groove shape using precision metrology methods and digital image processing. The effects of damage and contamination may be compensated through image processing. The speed and data handling capacity of available computing hardware make this approach practical. A feasibility test is reported which used a general purpose optical metrology system to study a 50 year old 78 r.p.m. phonograph record.

An application-specific integrated circuit (ASIC) wafer test system has been developed to provide comprehensive production screening of the ATLAS Semiconductor Tracker front-end chip (ABCD3T). The ABCD3T features a 128-channel analog front-end, a digital pipeline, and communication circuitry, clocked at 40 MHz, which is the bunch crossing frequency at the Large Hadron Collider. The tester measures values and tolerance ranges of all critical IC parameters, including dc parameters, electronic noise, time resolution, clock levels, and clock timing. The tester is controlled by a field-programmable gate array (ORCA3T) programmed to issue the input commands to the IC and to interpret the output data. This allows the high-speed wafer-level IC testing necessary to meet the production schedule. To characterize signal amplitudes and phase margins, the tester utilizes pin-driver, delay, and digital-to-analog converter chips, which control the amplitudes and delays of signals sent to the IC under test. Output signals from the IC under test go through window comparator chips to measure their levels. A probe card has been designed specifically to reduce pickup noise that can affect the measurements. The system can operate at frequencies up to 100 MHz to study the speed limits of the digital circuitry before and after radiation damage. Testing requirements and design solutions are presented.

A new technological solution to improve the beam-loss protection of silicon strip sensors used in large High Energy Physics experiments is presented. In the current ATLAS-SCT, sensors have Punch-Through protection (PTP) structures included to develop low impedance from the strip to the bias ring in case large voltages exceed some threshold that could damage the strip coupling capacitance. Previous studies show that the high strip resistance limits the beneficial effect of full PTP structures to the area near the structures. In our approach, we extend the PTP protection to the full active area of the sensor by lowering the strip resistance. This is achieved by the addition of a conductive layer connected along the whole strip implant. Strip sensors with different PTP structures, varying the p-stop strip isolation width and the distance between the strip to the bias ring, have been designed and fabricated using our technology proposal, together with standard sensors. Electrical characterization include general performance sensor tests (IV, CV, Rinterstrip, Cinterstrip, Ccoupling) and pulse formation tests to show that sensor performance is not compromised due to the technological modification. Besides, Punch-through DC static measurements and laser-based performance studies have been done to demonstrate the effectiveness of our proposal.

A detailed description of the integration structures for the barrel region of the silicon strips tracker of the ATLAS Phase-II upgrade for the upgrade of the Large Hadron Collider, the so-called High Luminosity LHC (HL-LHC), is presented. This paper focuses on one of the latest demonstrator prototypes recently assembled, with numerous unique features. It consists of a shortened, shield-less, and double sided stave, with two candidate power distributions implemented. Thermal and electrical performances of the prototype are presented, as well as a description of the assembly procedures and tools.