Silicon Microstrip Detectors Research Articles

Evaluation of charge -sharing effects on the spatial resolution of the PICASSO detector

A double -layer “edge-on” silicon microstrip detector has been designed and realized in the frame of the PICASSO (Phase Imaging for Clinical Application with Silicon detector and Synchrotron radiatiOn) project at the SYRMEP (SYnchrotron Radiation for MEdical Physics) beamline of Elettra (Trieste, Italy). The detector meets the requirements for synchrotron radiation mammography with patients inregarding: (a) size, since it covers the full beam width (210 mm); (b) spatial resolution, determined by the 0.05 mm strip pitch; (c) single-photon counting capabilities, because it is able to handle more than 10 6 photons/(pixel×s); (d) contrast resolution, thanks to a threshold trim DAC that equalizes the channel sensitivity; (e) efficiency, due to the high absorption in the 15–20 mm sensor depth. Experimental measurements evidence charge sharing, though not compromising the spatial resolution.

SLHC upgrade of the ATLAS SCT tracker

The LHC accelerators and detectors will be upgraded to the super LHC (SLHC) in two phases: in PHASE-I to the peak luminosities of ∼3×10 34 cm −2 s −1 and in PHASE-II to ≥10×10 34 cm −2 s −1, to collect proton–proton collision data of ∼3000 fb −1 per experiment. The complete inner trackers of the ATLAS detector will be replaced with new silicon pixels in the inner part and new silicon microstrip detectors in the outer part. The n-strips in the p-type material (“n-in-p”) microstrip sensors have been developed. The n-in-p sensor collects electrons, the faster signals, in the p–n junction side of the detector throughout its lifetime. Characterization of the wafer materials and the design of the strip sensors have advanced through the development of ATLAS05, ATLAS06, and ATLAS07 sensors. An n-in-p silicon microstrip sensor has been fabricated that tolerates bias voltage up to ∼1000 V, in 150-mm-diameter FZ wafers from industry.

A single-photon counting “edge-on” silicon detector for synchrotron radiation mammography

The Phase Imaging for Clinical Application with Silicon detector and Synchrotron radiatiOn (PICASSO) project is developing an “edge-on” silicon microstrip detector for mammography with synchrotron radiation. The sensor is equipped with a fast single-photon counting electronics based on the Mythen-II application-specific integrated circuit. A first prototype has been assembled and tested at the SYnchrotron Radiation for MEdical Physics (SYRMEP) beamline at Elettra in Trieste, Italy. The first results are presented in this study including evidence of high-rate single-photon counting with negligible losses up to 1.2×10 6 incident photons per pixel per second; spatial resolution consistent with the pixel aperture (0.3 mm×0.05 mm); high-quality imaging of test-objects, obtained with a dose comparable to the one delivered in modern full-field digital mammographic systems.

Silicon microstrip detectors in 3D technology for the sLHC

The projected luminosity upgrade of the large hadron collider (LHC), the sLHC, will constitute a challenging radiation environment for tracking detectors. Massive improvements in radiation hardness are required with respect to the LHC. In the layout for the new ATLAS tracker, silicon strip detectors (SSDs) with short strips cover the region from 28 to 60 cm distance to the beam. These SSDs will be exposed to fluences up to 10 15 N eq / cm 2 , hence radiation resistance is the major concern. It is advantageous to fuse the superior radiation hardness of the 3D design originally conceived for pixel-style applications with the benefits of the well-known planar technology for strip detectors. This is achieved by ganging rows of 3D columns together to form strips. Several prototype sLHC detector modules using 3D SSD with short strips, processed on p-type silicon, and LHC-speed front-end electronics from the present ATLAS semi-conductor tracker (SCT) were built. The modules were tested before and after irradiation to fluences of 10 15 N eq / cm 2 . The tests were performed with three systems: a highly focused IR-laser with 5 μ m spot size to make position-resolved scans of the charge collection efficiency (CCE), a Sr 90 β -source set-up to measure the signal levels for a minimum ionizing particles (MIPs), and a beam test with 180 GeV pions at CERN. This article gives a brief overview of the performance of these 3D modules, and draws conclusions about options for using 3D strip sensors as tracking detectors at the sLHC.

First LHC beam induced tracks reconstructed in the LHCb VELO

The Vertex Locator of the LHCb experiment has been used to fully reconstruct beam induced tracks at the LHC. A beam of protons was collided with a beam absorber during the LHC synchronisation test of the anti-clockwise beam on the weekend 22nd–24th August 2008. The resulting particles have been observed by the Vertex Locator. The LHCb Vertex Locator is a silicon micro-strip detector containing 21 planes of modules. Tracks were observed passing through up to 19 modules (38 silicon sensors). A total of over 700 tracks were reconstructed, and are being used to study the calibration and alignment of the detector.

Off-line calibration and data analysis for the silicon beam telescope on the CERN H2 beam

The Silicon Beam Telescope (SiBT07) at the CERN H2 beam is a position-sensitive beam telescope targeted for LHC upgrade tests. The telescope consists of eight consecutive silicon microstrip detectors and slots for two test detectors. This article describes the reconstruction of reference tracks with the CMS data analysis software CMSSW. The related data analysis and calibration procedures, including pedestal corrections, common-mode corrections, and track-based alignment, are also described.

Boron imaging with a microstrip silicon detector for applications in BNCT

Boron Neutron Capture Therapy (BNCT) is a radiotherapic technique exploiting the α particles produced after the irradiation of the isotope 10 of boron with thermal neutrons in the capture reaction B ( n , α ) 7 10 Li . It is used to treat tumours that for their features (radioresistance, extension, localization near vital organs) cannot be treated through conventional photon-beams radiotherapy. One of the main limitations of this technique is the lack of specificity (i.e. the ability of localizing in tumour cells, saving the healthy tissues) of the compounds used to carry the 10B isotope in the organs to be treated. This work, developed in the framework of the INFN PhoNeS project, describes the possibility of boron imaging performed exploiting the neutrons photoproduced by a linac (the Clinac 2100C/D of the S. Anna Hospital Radiotherapy Unit in Como, Italy) and detecting the α s with a non-depleted microstrip silicon detector: the result is a 1D scan of the boron concentration. Several boron doped samples have been analysed, from solutions of H 3 BO 3 (reaching a minimum detectable amount of 25 ng of 10B) to biological samples of urine containing BPA and BSH (the two molecules currently used for the clinical trials in BNCT) in order to build kinetic curves (showing the absolute 10B concentration as a function of time). Further measurements are under way to test the imaging system with 10BPA–Fructose complex perfused human lung samples.

Studies of charge collection efficiencies of planar silicon detectors after doses up to [formula omitted] and the effect of varying diode configurations and substrate types

Planar, segmented silicon sensors are used for the tracker and vertex detectors of high energy physics experiments at the Large Hadron Collider (LHC) because of their unsurpassed performance in terms of granularity, resolution and speed while offering relatively low mass. The planned luminosity upgrade of the LHC at CERN (Super-LHC, SLHC) will provide a difficult environment for these silicon tracking and vertexing detector systems. For the regions where silicon micro-strip detectors are envisaged in the SLHC ATLAS experimental upgrade, the expected particle fluence at the innermost micro-strip layer is up to 1 × 10 15 1 MeV neutron equivalent particles ( n eq ) per square centimeter over the anticipated 5 year lifespan of the experiment, making the radiation hardening of the silicon detectors more important than ever. We present studies of the charge collection efficiencies of various diode configurations ( p + -strip in n-bulk, n + -strip in n-bulk, and n + -strip in p-bulk) as well as substrate types (float zone, FZ or magnetic Czochralski, MCz) after neutron irradiation up to 1 × 10 15 n eq cm - 2 . The charge collection efficiency measurements have been carried out using 128 channel analogue, high-speed (40 MHz) electronics and a strontium electron source. These measurements indicate that p-in-n sensors are not radiation tolerant enough for use at the SLHC for micro-strip detectors. Both n-in-n and n-in-p geometries in both FZ and MCz substrates have shown sufficient charge collection for use in these regions, with n-in-p FZ chosen as the baseline technology choice for the ATLAS upgrade.

Photon counting microstrip detector for time resolved powder diffraction experiments

The Microstrip sYstem for Time rEsolved experimeNts (MYTHEN) detector is a silicon microstrip detector with single photon counting readout developed for powder diffraction experiments at the Swiss Light Source. A one-dimensional 30 k channels system covering 120° has been installed at the Material Science beamline and is being used for users operation since the end of 2007. Due to its massively parallel detection of X-rays and fast readout, it is optimized for time-resolved or dose–critical measurements that can be performed in fractions of a second on the whole angular range. The intensity of the synchrotron radiation source can be exploited thanks to the high counting rate capability. Promising results have been obtained also for other synchrotron radiation applications like imaging and pump-and-probe experiments. The detector characteristics will be described in detail and its outstanding performances will be shown.

Experimental study of the radiation emitted by180−GeV∕celectrons and positrons volume-reflected in a bent crystal

The radiation emitted by $180\ensuremath{-}\mathrm{GeV}∕c$ volume-reflected electrons and positrons impinging on a bent crystal has been measured by the H8RD22 Collaboration on the H8 beamline at the CERN SPS. A dedicated spectrometer has been developed to measure high-energy photon spectra (up to $\ensuremath{\sim}100\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$) under volume reflection: photon and charged particle beams have been separated by a bending magnet and leptons were detected and tagged by microstrip silicon detectors and a Pb-scintillator sampling calorimeter. A comparison between the experimental and analytical data for the amorphous and volume-reflection cases is presented and the differences are discussed.

Short Strips for the sLHC: A P-Type Silicon Microstrip Detector in 3-D Technology

The luminosity upgrade of the Large Hadron Collider (LHC), the sLHC, will constitute an extremely challenging radiation environment for tracking detectors. With respect to the LHC, large improvements in radiation hardness are required. In this paper, we investigated the expected radiation hardness of the 3-D-design, where rows of 3-D-columns are etched in substrate material and joined together to form strips. To investigate the feasibility of 3-D silicon strip detectors (SSD) for the sLHC, we have built prototype modules using 3-D single type column (3-D-STC) strip detectors with short strips and front-end electronics from the present ATLAS SemiConductor Tracker (SCT). The modules were tested with a beta source setup before and after irradiation to sLHC fluences with 26 MeV protons. We report on the performance of these 3-D-modules, compare it to the results prior to irradiation, and draw conclusions about options for using 3-D SSD detectors for tracking at the sLHC.

Track reconstruction of cosmic ray real data with the CMS Silicon Strip Tracker

The CMS tracking system consists of a silicon pixel vertex detector and a surrounding silicon microstrip detector. The system is currently going through final assembly stage. As the construction goes on, big parts of the detector are being powered, controlled and readout as a whole. A cosmic ray trigger has been setup, thus providing the first real events recorded in the CMS tracker. Reconstruction was performed with three track finder algorithms; we will talk about the Combinatorial Track Finder, which is based on the Kalman Filter technique for both trajectory building and track fitting. A dedicated algorithm for cosmic ray track's seeding has been developed, together with useful tools for the tracking performance analysis; the exercise has been very useful for the understanding and the improvement of the tracking algorithm.

First flight data from the PAMELA spectrometer

PAMELA is a satellite-borne experiment designed to study charged particles in the cosmic radiation, optimized in particular for antimatter components search. The experiment is mounted on the Resurs DK1 satellite that was launched on June 15th 2006 from Baikonur cosmodrome and is now collecting data from a semi-polar elliptical orbit around the Earth. The core of the PAMELA apparatus is a magnetic spectrometer, designed to determine precisely the rigidity and the absolute charge of particles crossing the detector. The tracking system is composed of six planes of silicon microstrip detectors dipped in an almost uniform magnetic field generated by a permanent magnet made of an Nd–Fe–B alloy. Some preliminary analysis about the spectrometer's performances, made using data collected since July 2006 till June 2007, are here reviewed.

The LHCb silicon tracker

The Silicon Tracker is a large-surface silicon micro-strip detector that covers the full acceptance of the experiment in a single tracking station upstream of the spectrometer magnet and the inner-most part of three tracking stations downstream of the magnet. Special emphasis has been put on module quality assurance at all stages of the production. Various tests are performed after each production step and each module goes through several burn-in cycles. The design of the LHCb silicon detectors is described and the main lessons learnt from the R&D phase are summarised. Focus will be on the experience from module production and the quality assurance program.

Deflection of400 GeV/cproton beam with bent silicon crystals at the CERN Super Proton Synchrotron

This paper presents a detailed study of the deflection phenomena of a $400\text{ }\text{ }\mathrm{GeV}/c$ proton beam impinging on a new generation of bent silicon crystals; the tests have been performed at the CERN Super Proton Synchrotron H8 beam line. Channeling and volume reflection angles are measured with an extremely precise goniometer and with high resolution silicon microstrip detectors. Volume reflection has been observed and measured for the first time at this energy, with a single-pass efficiency as large as 98%, in good agreement with the simulation results. This efficiency makes volume reflection a possible candidate for collimation with bent crystals at the CERN Large Hadron Collider.

A novel Si strip array to investigate reaction and decay mechanisms

The performance of a novel set-up of double-sided silicon micro-strip detectors (DSSD) developed for the GSI-R3B project (reaction studies with relativistic radioactive beams) is presented. The set-up was used in an experiment aimed at measuring the two-proton decay of 19Mg. This experiment required to record simultaneously protons and the residual nuclei with good position and energy resolution. Our experimental results show that both protons and heavy ions ranging from Z=2 up to Z=12 can be identified with good signal-to-noise ratio and high energy and spatial resolution. This allowed to reconstruct 2- and 3-particle vertices with high precision, opening the possibility to measure lifetimes of very short-lived nuclei and to obtain precise angular correlations of the outgoing particles. This detection system serves as a prototype for the R3B recoil detector, which will be composed of a two-layer Si strip tracker.

Performance Tests of Developed Silicon Strip Detector by Using a 150 GeV Electron Beam

We manufactured and characterized a silicon micro-strip detector to be used in a beam tracker. A silicon detector features a DC-coupled silicon strip sensor with VA1_Prime2 analog readout chips.The silicon strip sensors have been fabricated on 5-in. wafers at Electronics and Telecommunications Research Institute (Daejeon, Korea). The silicon strip sensor is single-sided and has 32 channels with a 1 mm pitch, and its active area is 3.2 by 3.2 cm2 with 380 μm thickness. The readout electronics consists of VA hybrid, VA Interface, and FlashADC & Control boards. Analog signals from the silicon strip sensor were being processed by the analog readout chips on the VA hybrid board. Analog signals were then changed into digital signals by a 12 bit 25 MHz FlashADC. The digital signals were read out by the Linux-operating PC through the FlashADC-USB2 interface. The DAQ system and analysis programs were written in the framework of ROOT package.The beam test with the silicon detector had been performed at CERN beam facility. We used a 150 GeV electron beam out of the SPS(Super Proton Synchrotron) H2 beam line. We present beam test setup and measurement result of signal-to-noise ratio of each strip channel.

A prototype of radiation imaging detector using silicon strip sensors

The aim of this work is to evaluate the performance of a strip sensor with a single photon counting data acquisition system based on VA1 readout chips to study the feasibility of a silicon microstrip detector for medical application. The sensor is an AC-coupled single-sided microstrip sensor and the active area of the sensor is 32.0 mm×32.0 mm with a thickness of 380 μm. The sensor has 64 readout strips with a pitch of 500 μm. The sensor was biased at 45 V and the experiment was performed at room temperature. Two silicon strip sensors were mounted perpendicularly one another to get two-dimensional position information with a 5 mm space gap. Two low noise analog ASICs, VA1 chips, were used for signal readout of the strip sensor. The assembly of sensors and readout electronics was housed in an Al light-tight box. A CsI(Tl) scintillation crystal and a 2-in. photomultiplier tube were used to trigger signal events. The data acquisition system was based on a 64 MHz FADC and control softwares for the PC-Linux platform. Imaging tests were performed by using a lead phantom with a 90Sr radioactive source and a 45 MeV proton beam at Korea Institute of Radiological and Medical Science in Seoul, respectively. Results of the S/ N ratio measurement and phantom images are presented.

Annealing studies of silicon microstrip detectors irradiated at high neutron fluences

Silicon p-type detectors are being investigated for the development of radiation-tolerant detectors for the luminosity upgrade of the CERN large hadron collider (Super-LHC (sLHC)). Microstrip detectors have been fabricated by CNM-IMB with an n-side read-out on p-type high-resistivity float zone substrates. They have been irradiated with neutrons at the TRIGA Mark II nuclear reactor in Ljubljana. The irradiation fluxes match with the expected doses for the inner tracker at the sLHC (up to 10 16 equivalent 1 MeV neutrons cm −2). The macroscopic properties of the irradiated prototypes after irradiation were characterized at the IFIC-Valencia laboratory. The charge collection studies were carried out by means of a radioactive source setup as well as by an infrared laser illumination. The annealing behavior was studied in detail on a microstrip detector irradiated with a flux of 10 15 equivalent 1 MeV neutrons cm −2. Collected charge measurements were made after accelerated annealing times at 80 °C up to an equivalent annealing time of several years at room temperature. This note reports on the recorded results from the annealing of the irradiated p-type microstrip sensor.

A new analogue sampling readout system for the COMPASS RICH-1 detector

A new electronic readout for CsI-coated multiwire proportional chambers (MWPC), used as photon detectors in the COMPASS ring imaging Cherenkov (RICH) detector, is described. A prototype system comprising more than 5000 channels has been built and tested in high-intensity beam conditions. It is based on the APV25-S1 analogue sampling chip, and replaces the GASSIPLEX chip readout used previously. The APV25 chip, although originally designed for Silicon microstrip detectors, is shown to perform well even with “slow” signals from an MWPC, maintaining a signal-to-noise ratio (SNR) of 9. For every trigger the system reads out three consecutive amplitudes in time, thus allowing to extract information on both the signal amplitude and its timing. This information is used to reduce pile-up events in a high-rate environment. Prototype tests of the new readout electronics on a central RICH photocathode in nominal COMPASS beam conditions showed that the effective time window is reduced from more than 3μs for the GASSIPLEX to less than 400ns for the APV25 chip. This leads to a significant improvement of the signal-to-background ratio (SBR) with respect to the original readout. A gain by a factor of 5–6 was experimentally verified in the very forward region of phase space, where pile-up due to the muon beam halo is most significant. Owing to its pipelined architecture, the new readout system also considerably reduces the dead time per event, thus allowing to make use of trigger rates exceeding 50kHz.