2013

A portable telescope based on the ALIBAVA system for test beam studies
J. Bernabeu, G. Casse, C. Garcia, A. Greenall, C. Lacasta, M. Lozano, S. Marti-Garcia, G. Pellegrini, J. Rodriguez, M. Ullan, I. Tsurin
Nuclear Inst. & Meth. A, Vol. 732, 21 December 2013, Pages 130–133
Proceedings of the Vienna Conference on Instrumentation 2013
doi:10.1016/j.nima.2013.06.067

Abstract: A test beam telescope has been built using the ALIBAVA system to drive its data acquisition. The basic telescope planes consist of four XYT stations. Each station is built from a detector board with two strip sensors, mounted one in each side (strips crossing at 90°). The ensemble is coupled to an ALIBAVA daughter board. These stations act as reference frame and allow a precise track reconstruction. The system is triggered by the coincidence signal of the two scintillators located up and down stream. The telescope can hold several devices under tests. Each ALIBAVA daughter board is linked to its corresponding mother board. The system can hold up to 16 mother boards. A master board synchronizes and controls all the mother boards and collects their data. The off-line analysis software has been developed to study the charge collection, cluster width, tracking efficiency, resolution, etc., of the devices under test. Moreover, the built-in ALIBAVA TDC allows the analysis of the time profile of the device signal. The ALIBAVA telescope has been successfully operated in two test runs at the DESY and CERN-SPS beam lines.

Signal and charge collection efficiency of n-in-p strip detectors after mixed irradiation to HL-LHC fluences
S. Kuehn, T. Barber, G. Casse, P. Dervan, A. Driewer, D. Forshaw, T. Huse, K. Jakobs, U. Parzefall
Nuc. Instr. Meth. A , Volume 730, 1 December 2013, Pages 58-61
doi:10.1016/j.nima.2013.04.068

Abstract: For the year 2020, an upgrade of the LHC with a factor ten increase in luminosity is planned. The resulting severe radiation doses for the ATLAS tracker demand extremely radiation tolerant detectors. In this study six planar n-in-p strip sensors produced by Hamamatsu Photonics were irradiated in consecutive irradiation steps with pions of 280 Mev/c, protons of 25 Mev/c and reactor neutrons resulting in a combined fluence of up to 3×1015 1 MeV neutron equivalent particles per square centimeter (neq/cm2)(neq/cm2). This particle composition and fluence corresponds to the qualification limit specified by the ATLAS experiment for the outer pixel layers (assuming an integrated luminosity of 3000 fb-1). The View the MathML source320µm thick devices are investigated using electrons from a 90Sr source. After each irradiation step both charge collection efficiency and noise measurements have been performed using the ALIBAVA readout system, which is based on analogue ASIC chip clocked at 40 MHz. Measurements of the signal and signal-to-noise ratio of detectors will be given after the sensors were exposed to radiation that both in fluence and composition are corresponding to the expectations for the HL-LHC trackers. Conclusions will be drawn on their operation in the ATLAS inner detector upgrade.

A charge collection study with dedicated RD50 charge multiplication sensors
C. Betancourt, T. Barber, M. Hauser, K. Jakobs, S. Kuehn, U. Parzefall, S. Wonsak
Nuc. Instr. Meth. A , Volume 730, 1 December 2013, Pages 62-65
doi:10.1016/j.nima.2013.05.186

Abstract: This study investigates the charge collection efficiency of silicon strip detectors, produced by MICRON Semiconductor Co., Ltd. within the CERN RD50 collaboration, designed specifically to understand the effect of design parameters on the onset and magnitude of charge multiplication. Charge collection measurements are performed before and after irradiation with a proton fluence of 1×1015 1 MeV neq/cm2 and neutron fluence ranging from 1–5×1015 neq/cm2. Structures on these devices include varying diffusion times and energies for the implantation process, different sensor thicknesses, the use of intermediate biased or floating strips between the readout strips, and several different strip width and pitch geometries. The charge collection for these devices is studied as a function of the bias voltage, looking for indications of charge multiplication. Results are compared to standard float zone 300µm thick silicon strip sensors having a strip width of 25µm and pitch of 80µm.

Degradation of charge sharing after neutron irradiation in strip silicon detectors with different geometries
G. Casse, P. Dervan, D. Forshaw, A. Greenall, T. Huse, I. Tsurin, M. Wormald, Members of the CERN/RD50 collaboration
Nuc. Instr. Meth. A , Volume 730, 1 December 2013, Pages 54-57
doi:10.1016/j.nima.2013.05.158

Abstract: The aim of the CERN/RD50 collaboration is the improvement of the radiation tolerance of semiconductor detectors for future experiments at high-luminosity colliders. In the RD50 framework, evidence of enhanced signal charge in severely irradiated silicon detectors (diodes, segmented planar and 3D devices) was found. The underlying mechanism was labelled charge multiplication. This has been one of the most exciting results from the research activity of RD50 because it could allow for a greatly extended radiation tolerance, if the mechanism is to be found controllable and tuneable. The charge multiplication mechanism is governed by impact ionisation from electrons drifting in high electric field. The electric field profile is influenced by the geometry of the implanted electrodes. In order to investigate the influence of the diode implantation geometry on charge multiplication, the RD50 collaboration has commissioned the production of miniature microstrip silicon sensors with various choices of strip pitch and strip width over pitch (w/p) ratios. Moreover, some of the sensors were produced interleaving readout strips with dummy intermediate ones in order to modify the electric field profile. These geometrical solutions can influence both charge multiplication and charge sharing between adjacent strips. The initial results of this study are here presented.

The Birmingham Irradiation Facility
P. Dervan, R. French, P. Hodgson, H. Marin-Reyes, J. Wilson
Nuc. Instr. Meth. A , Volume 730, 1 December 2013, Pages 101-104
doi:10.1016/j.nima.2013.05.156

Abstract: At the end of 2012 the proton irradiation facility at the CERN PS will shut down for two years. With this in mind, we have been developing a new ATLAS scanning facility at the University of Birmingham Medical Physics cyclotron. With proton beams of energy approximately 30 MeV, fluences corresponding to those of the upgraded Large Hadron Collider (HL-LHC) can be reached conveniently. The facility can be used to irradiate silicon sensors, optical components and mechanical structures (e.g. carbon fibre sandwiches) for the LHC upgrade programme. Irradiations of silicon sensors can be carried out in a temperature controlled cold box that can be scanned through the beam. The facility is described in detail along with the first tests carried out with mini (1×1 cm2) silicon sensors.

Scribe–cleave–passivate (SCP) slim edge technology for silicon sensors
V. Fadeyev, H.F.-W. Sadrozinski, S. Ely, J.G. Wright, M. Christophersen, B.F. Phlips, G. Pellegrini, S. Grinstein, G.-F. Dalla Betta, M. Boscardin, R. Klingenberg, T. Wittig, A. Macchiolo, P. Weigell, D. Creanza, R. Bates, A. Blue, L. Eklund, D. Maneuski, G. Stewart, et al.
Nuc. Instr. Meth. A , Volume 731, 11 December 2013, Pages 260-265
doi:10.1016/j.nima.2013.03.046

Abstract: We are pursuing scribe–cleave–passivate (SCP) technology of making “slim edge” sensors. Such sensors have only a minimal amount of inactive peripheral region, which benefits construction of large-area tracker and imaging systems. Key application steps of this method are surface scribing, cleaving, and passivation of the resulting sidewall. We are working on developing both the technology and physical understanding of the processed devices performance. In this paper we begin by reviewing the manufacturing options of SCP technology. Then we show new results regarding the technology automation and device physics performance. The latter includes charge collection efficiency near the edge and radiation hardness study. We also report on the status of devices processed at the request of the RD50 collaborators.

Characterization of 3D-DDTC strip sensors with passing-through columns
M. Povoli, C. Betancourt, M. Boscardin, G.-F. Dalla Betta, G. Giacomini, B. Lecini, S. Kuehn, U. Parzefall, N. Zorzi
Nuc. Instr. Meth. A , Volume 730, 1 December 2013, Pages 38-43
doi:10.1016/j.nima.2013.04.064

Abstract: We report on the pre-irradiation electrical and functional characterization of newly developed 3D silicon strip detectors fabricated at FBK. Critical layout aspects present in the previous version of the technology were solved, and the new sensors are showing encouraging results both in terms of electrical properties and charge collection efficiency.

3D active edge silicon sensors: Device processing, yield and QA for the ATLAS-IBL production
C. Da Vià, M. Boscardin, G.-F. Dalla Betta, G. Darbo, C. Fleta, C. Gemme, G. Giacomini, P. Grenier, S. Grinstein, T.-E. Hansen, J. Hasi, C. Kenney, A. Kok, A. La Rosa, A. Micelli, S. Parker, G. Pellegrini, D.-L. Pohl, M. Povoli, E. Vianello, N. Zorzi, S.J. Watts
Nuclear Inst. & Meth. A, Vol. 699, 21 January 2013, Pages 18-21
doi:10.1016/j.nima.2012.05.070

Abstract: 3D silicon sensors, where plasma micromachining is used to etch deep narrow apertures in the silicon substrate to form electrodes of PIN junctions, were successfully manufactured in facilities in Europe and USA. In 2011 the technology underwent a qualification process to establish its maturity for a medium scale production for the construction of a pixel layer for vertex detection, the Insertable B-Layer (IBL) at the CERN-LHC ATLAS experiment. The IBL collaboration, following that recommendation from the review panel, decided to complete the production of planar and 3D sensors and endorsed the proposal to build enough modules for a mixed IBL sensor scenario where 25% of 3D modules populate the forward and backward part of each stave. The production of planar sensors will also allow coverage of 100% of the IBL, in case that option was required. This paper will describe the processing strategy which allowed successful 3D sensor production, some of the Quality Assurance (QA) tests performed during the pre-production phase and the production yield to date.

Embedded pitch adapters for the ATLAS Tracker Upgrade
M. Ullan, V. Benitez, G. Pellegrini, C. Fleta, M. Lozano, C. Lacasta, U. Soldevila, C. Garcia
Nuc. Instr. Meth. A , Volume 732, 21 December 2013, Pages 178–181
doi:10.1016/j.nima.2013.07.078

Abstract: In the current ATLAS tracker modules, sensor bonding pads are placed on their corresponding strips and oriented along the strips. This creates a difference in pitch and orientation between sensor bond pads and readout electronics bond pads. Therefore, a pitch adapter (PA), or “fan-in”, is needed. The purpose of these PA is the electrical interconnection of every channel from the detector bonding pads to the read-out chips, adapting the different pad pitch. Our new approach is to build those PAs inside the sensor; this is what we call Embedded Pitch Adapters. The idea is to use an additional metal layer in order to define a new group of pads, connected to the strips via tracks with the second metal. The embedded PAs have been fabricated on 4-in. prototype sensors for the ATLAS-Upgrade Endcap Tracker to test their performance and suitability. The tests confirm proper fabrication of the second metal tracks, and no effects on detector performance. No indication of cross-talk between first and second metal channels has been observed. A small indication of possible signal pick-up from the bulk has been observed in a few channels, which needs to be further investigated.

Charge multiplication in irradiated segmented silicon detectors with special strip processing
G. Casse, D. Forshaw, T. Huse, I. Tsurin, M. Wormald, M. Lozano, G. Pellegrini
Nuclear Inst. & Meth. A, Vol. 699, 21 January 2013, Pages 9-13
doi:10.1016/j.nima.2012.04.033

Abstract: Charge multiplication in severely irradiated silicon detectors is now a well proven effect that enhances their charge collection and makes them operable up to the doses anticipated for future super-colliders (like the high luminosity LHC at CERN). The effect is well documented but not completely understood. The multiplication is caused by impact ionisation due to hot electrons moving in the high electric field that develops near the junction in the irradiated sensors. The details of the electric field profile in the silicon bulk are not available due to the unknown spatial distribution of the inhomogeneous effective space charge in the hadron irradiated silicon bulk. The gradient of the effective space charge distribution is crucial for the formation of high electric field regions where the multiplication takes place. The electric field might be influenced by the implant forming the n–p junction and by a non-homogenous bulk space charge near the junction. Deep n+ structures (junction) could enhance or reduce the multiplication effect. Also an altered doping gradient (obtainable for example by a graded p-doping between the junction and the p-bulk) could achieve the same results. In order to achieve enhanced charge multiplication in microstrip detectors the junction has been shaped by mean of deep p-doping diffusion and of trenches etched in the silicon bulk and filled with n+ doped polysilicon to create a deep junction. We report here the result obtained with these methods before and after various doses of neutron irradiation.

ALIBAVA silicon microstrip readout system for educational purposes
J. Bernabeu,G. Casse, C. Garcia, Greenall, C. Lacasta, M. Lozano, G. Pellegrini, J. Rodriguez, S. Marti-Garcia, M. Ullan, IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS-MIC) 2013
doi:10.1109/NSSMIC.2013.6829803

Abstract: The ALIBAVA is a compact and portable system for characterization of silicon microstrip radiation detectors. Actually, the ALIBAVA system is conceived to easily characterize multichannel semiconductor detectors, providing high sensitivity to low signals and high speed. The front-end electronics is based on a low noise ASIC with 128 input channels. Beyond its scientific and sensor R&D applications, the system can also be used in instrumentation lectures at the university teaching laboratories. New features of the system makes it more suitable for its handling by undergraduate and postgraduate students (following lectures on radiation detection instrumentation), who will greatly benefit in their instruction by using this system to learn about the properties of microstrip sensors and signal formation in those devices which are extensively used in a wide range of fields as High Energy Physics, Nuclear Physics, Medical Physics, etc.

Characterisation of edgeless technologies for pixellated and strip silicon detectors with a micro-focused X-ray beam
R. Bates, A. Blue, M. Christophersen, L. Eklund, S. Ely, V. Fadeyev, E. Gimenez, V. Kachkanov, J. Kalliopuska, A. Macchiolo, D. Maneuski, B. F. Phlips, H. Sadrozinski, G. Stewart, N. Tartoni, R. M. Zain
Journal of Instrumentation, 2013, Vol. 8, Issue 01, Article P01018
doi:10.1088/1748-0221/8/01/P01018

Abstract: Reduced edge or “edgeless” detector design offers seamless tileability of sensors for a wide range of applications from particle physics to synchrotron and free election laser (FEL) facilities and medical imaging. Combined with through-silicon-via (TSV) technology, this would allow reduced material trackers for particle physics and an increase in the active area for synchrotron and FEL pixel detector systems. In order to quantify the performance of different edgeless fabrication methods, 2 edgeless detectors were characterized at the Diamond Light Source using an 11 µm FWHM 15 keV micro-focused X-ray beam. The devices under test were: a 150 µm thick silicon active edge pixel sensor fabricated at VTT and bump-bonded to a Medipix2 ROIC; and a 300 µm thick silicon strip sensor fabricated at CIS with edge reduction performed by SCIPP and the NRL and wire bonded to an ALiBaVa readout system. Sub-pixel resolution of the 55 µm active edge pixels was achieved. Further scans showed no drop in charge collection recorded between the centre and edge pixels, with a maximum deviation of 5% in charge collection between scanned edge pixels. Scans across the cleaved and standard guard ring edges of the strip detector also show no reduction in charge collection. These results indicate techniques such as the scribe, cleave and passivate (SCP) and active edge processes offer real potential for reduced edge, tiled sensors for imaging detection applications.

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