Showing papers by "Manuel Lozano published in 2011"

Comparative measurements of highly irradiated n-in-p and p-in-n 3D silicon strip detectors

Abstract: Silicon detectors in 3D technology are a candidate for applications in environments requiring an extreme radiation hardness, as in the innermost layers of the detectors at the proposed High-Luminosity LHC. In 3D detectors, the electrodes are made of columns etched into the silicon perpendicular to the surface. This leads to higher electric fields, a smaller depletion voltage and a reduced trapping probability of the charge carriers compared to standard planar detectors. In this article, the signal and the noise of irradiated n-in-p and p-in-n 3D silicon strip detectors are compared. The devices under test have been irradiated up to a fluence of 2×1016 1 MeV neutron equivalent particles per square centimetre (neq/cm2), which corresponds to the fluence expected for the inner pixel detector layers at the High-Luminosity LHC. A relative charge collection efficiency of approximately 70% was obtained even after the highest irradiation fluence with both detector types. The influence of different temperatures on the signal and the noise is investigated and results of annealing measurements are reported.

Test Beam Results of 3D Silicon Pixel Sensors for the ATLAS upgrade

Abstract: Results on beam tests of 3D silicon pixel sensors aimed at the ATLAS Insertable B-Layer and High Luminosity LHC (HL-LHC) upgrades are presented. Measurements include charge collection, tracking efficiency and charge sharing between pixel cells, as a function of track incident angle, and were performed with and without a 1.6 T magnetic field oriented as the ATLAS inner detector solenoid field. Sensors were bump-bonded to the front-end chip currently used in the ATLAS pixel detector. Full 3D sensors, with electrodes penetrating through the entire wafer thickness and active edge, and double-sided 3D sensors with partially overlapping bias and read-out electrodes were tested and showed comparable performance.

Simulation of new p-type strip detectors with trench to enhance the charge multiplication effect in the n-type electrodes

Abstract: This paper shows the simulation results of new p-type strip detectors with trench electrodes to enhance the charge multiplication effect in the irradiated detector. The new design includes baby microstrip detectors (area=1 cm 2 ) with a strip pitch of 80 μm and p-stop isolation structures. The strip has a 5 μm-wide trench along all its length, filled and doped with polysilicon to create a deep N + contact into the material bulk. The trench depth can be varied in order to study the influence of the electric field on the charge multiplication effect in heavily irradiated samples. Some alternative designs have also been studied to establish a comparison between various structures using different technologies. Simulation reproduce the electrical behaviour under different irradiation conditions, taking into account the damage accumulated after irradiation with neutrons and protons with several fluence values. The investigation of these effects provides important indications on the ability of this modified electrode geometry to control and optimise the charge multiplication effect, in order to fully recover the collection efficiency of heavily irradiated microstrip detectors, at reasonable bias voltage compatible with the voltage feed limitation of the CERN SLHC experiments.

Geant4 and MCNPX simulations of thermal neutron detection with planar silicon detectors

Abstract: We used Geant4 and MCNPX codes to evaluate the detection efficiency of planar silicon detectors coupled to different Boron-based converters with varied compositions and thicknesses that detect thermal neutrons via the 10B(n,α)7Li nuclear reaction. Few studies about the thermal neutron transport in Geant4 have been reported so far and it is becoming increasingly difficult to ignore its discrepancies with MCNPX in this neutron energy range. In the thermal energy range, Geant4 shows high discrepancies with MCNPX giving a maximum efficiency of about 3.3% in the 10B case whereas that obtained with MCNPX was 5%. Disagreements obtained between both codes in this energy range are analyzed and discussed.

Precision scans of the Pixel cell response of double sided 3D Pixel detectors to pion and X-ray beams

Abstract: Three-dimensional (3D) silicon sensors offer potential advantages over standard planar sensors for radiation hardness in future high energy physics experiments and reduced charge-sharing for X-ray applications, but may introduce inefficiencies due to the columnar electrodes. These inefficiencies are probed by studying variations in response across a unit pixel cell in a 55μm pitch double-sided 3D pixel sensor bump bonded to TimePix and Medipix2 readout ASICs. Two complementary characterisation techniques are discussed: the first uses a custom built telescope and a 120GeV pion beam from the Super Proton Synchrotron (SPS) at CERN; the second employs a novel technique to illuminate the sensor with a micro-focused synchrotron X-ray beam at the Diamond Light Source, UK. For a pion beam incident perpendicular to the sensor plane an overall pixel efficiency of 93.0±0.5% is measured. After a 10o rotation of the device the effect of the columnar region becomes negligible and the overall efficiency rises to 99.8±0.5%. The double-sided 3D sensor shows significantly reduced charge sharing to neighbouring pixels compared to the planar device. The charge sharing results obtained from the X-ray beam study of the 3D sensor are shown to agree with a simple simulation in which charge diffusion is neglected. The devices tested are found to be compatible with having a region in which no charge is collected centred on the electrode columns and of radius 7.6±0.6μm. Charge collection above and below the columnar electrodes in the double-sided 3D sensor is observed.

Beam Test Measurements With Planar and 3D Silicon Strip Detectors Irradiated to sLHC Fluences

Abstract: The planned luminosity upgrade of the CERN LHC to the super LHC (sLHC) requires investigation of new radiation hard tracking detectors. Compared to the LHC, tracking detectors must withstand a 5-10 times higher radiation fluence. Promising radiation hard options are planar silicon detectors with n-side readout and silicon detectors in 3D technology, where columnar electrodes are etched into the silicon substrate. This article presents beam test measurements per formed with planar and 3D n-in-p silicon strip detectors. The detectors were irradiated to different fluences, where the maximum fluence was 3 × 1015 1 MeV neutron equivalent particles per square centimeter (neq/cm2) for the planar detectors and 2 × 1015 neq/cm2 for the 3D detectors. In addition to signal measurements, charge sharing and resolution of both detector technologies are compared. An increased signal from the irradiated 3D detectors at high bias voltages compared to the signal from the unirradiated detector indicates that charge multiplication effects occur in the 3D detectors. At a bias voltage of 260 V, the 3D detector irradiated to 2 × 1015 neq/cm2 yields a signal almost twice as high as the signal of the unirradiated detector. Only 30% of the signal of an unirradiated detector could be measured with the planar detector irradiated to 3 × 1015 neq/cm2 at a bias voltage of 600 V, which was the highest bias voltage applied to this sensor.

Combined effect of bias and annealing in gamma and neutron radiation assurance tests of SiGe bipolar transistors for HEP applications

Abstract: SiGe BiCMOS technologies are one of the proposed options for the front-end readout electronics of the detectors in the middle region of the ATLAS-Upgrade. The radiation hardness of the SiGe bipolar transistors is being assessed for this application through irradiations with different particles. Biasing conditions during irradiation experiments of bipolar transistors or circuits have an influence on the damage and there is a risk of erroneous results. We have performed several irradiation experiments of SiGe devices in different bias conditions. We have observed a systematic trend in gamma irradiations, showing a smaller damage in transistors irradiated biased compared to those irradiated with shorted or floating terminals. These effects have not been observed in neutron irradiations.

3D Medipix2 detector characterization with a micro-focused X-ray beam

Abstract: Three-dimensional (3D) photodiode detectors offer advantages over standard planar photodiodes in a wide range of applications. The main advantage of these sensors for X-ray imaging is their reduced charge sharing between adjacent pixels, which could improve spatial and spectral resolution. However, a drawback of 3D sensors structures is the loss of detection efficiency due to the presence in the pixel structure of heavily doped electrode columns which are insensitive to X-ray. In this work two types of 3D silicon detectors: n-type wafer with hole collecting readout-columns (n-type) and p-type wafer with electron collecting readout-columns (p-type), bump-bounded to a Medipix2 read-out chip were characterized with a 14.5 keV micro-focused X-ray beam from a synchrotron. Measurements of the detection efficiency and the charge sharing were performed at different bias voltages and Medipix2 energy thresholds and compared with those of a standard planar silicon sensor.

Results from the first prototype of large 3D active edge sensors

Abstract: 3D active edge sensors have advantages such as radiation hardness and edgeless capability With the use of deep reactive ion etching and wafer bonding, 185 by 205 mm2 3D detectors with active edges have been successfully fabricated at SINTEF MiNaLab These sensors are compatible with the ATLAS FE-I4 readout electronics Fabrication process and difficulties are presented and the preliminary electrical measurements are also discussed

CdTe/CZT pixel detector for gamma-ray spectrometry with imaging and polarimetry capability in astrophysics

Abstract: Gamma-ray astrophysics in the MeV energy range plays a crucial role for the understanding of many exciting cosmic phenomena such as stellar explosions or cosmic accelerators (eg, Supernovae, Novae, Supernova Remants (SNRs), Gamma-Ray Bursts (GRBs), Pulsars, etc) Cadmium Telluride (CdTe) and Cadmium Zinc Telluride (CdZnTe) are very attractive materials for gamma-ray detection, which have demonstrated a great potential onboard current space missions (such as IBIS/INTEGRAL and BAT/SWIFT) However, the energy coverage of these instruments has been limited up to a few hundred keV, and there has not been yet a dedicated instrument for polarimetry Our technological activities aim to develop a gamma-ray spectrometer based on Cd(Zn)Te detectors, with imaging and polarimetry capability for astrophysical applications, in the energy range from a few hundred keV up to a few MeV Within this framework, a gamma-ray polarimeter based on pixelated Cd(Zn)Te detectors in planar-transverse-field (PTF) configuration, is being considered as a payload option for a balloon-borne experiment

Measurements with Irradiated 3D Silicon Strip Detectors

Abstract: For the unprecedentedly high radiation level at the sLHC, the luminosity upgrade of the LHC, new tracking detectors are investigated. Among different approaches, silicon detectors in 3D technology constitute a promising option. Columnar electrodes are etched into the substrate, therefore the distance for charge collection and depletion is decoupled from the detector thickness. Thus, two of the detrimental effects caused by radiation in silicon (increased depletion voltage and charge carrier trapping) can be reduced. Results of measurements with irradiated 3D silicon strip detectors produced by IMB-CNM are presented.

Linear mode Reach — Through Avalanche Photodiodes for medium energy X-ray detection

Abstract: Reach-Through Avalanche Photodiodes (RT-APD) for medium energy X-ray detection, with 300 μm thick active region, have been devised, fabricated and characterised at the IMB-CNM clean room. The RT-APD structure and principle of operation are detailed in this paper, together with the main modifications introduced over its general design in order to improve the device performance. The optimisation of these parameters has been made with the aid of TCAD simulations, which suitability is showed here. Finally, the main aspects of the fabrication process and the first characterisation results have been also included.