During the shutdown of the CERN Large Hadron Collider in 2013-2014, an additional pixel layer was installed between the existing Pixel detector of the ATLAS experiment and a new, smaller radius beam pipe. The motivation for this new pixel layer, the Insertable B-Layer (IBL), was to maintain or improve the robustness and performance of the ATLAS tracking system, given the higher instantaneous and integrated luminosities realised following the shutdown. Because of the extreme radiation and collision rate environment, several new radiation-tolerant sensor and electronic technologies were utilised for this layer. This paper reports on the IBL construction and integration prior to its operation in the ATLAS detector.

During the shutdown of the CERN Large Hadron Collider in 2013-2014, an additional pixel layer was installed between the existing Pixel detector of the ATLAS experiment and a new, smaller radius beam pipe. The motivation for this new pixel layer, the Insertable B-Layer (IBL), was to maintain or improve the robustness and performance of the ATLAS tracking system, given the higher instantaneous and integrated luminosities realised following the shutdown. Because of the extreme radiation and collision rate environment, several new radiation-tolerant sensor and electronic technologies were utilised for this layer. This paper reports on the IBL construction and integration prior to its operation in the ATLAS detector.

Extent and accuracy of surgical resection is a crucial step in operable tumor therapy. Emergence of promising specific tumor-seeking agents labeled with positron emitters is giving rise to a renewed interest for radioguided surgery using beta probes. Beta detection, due to the particle short range, allows a more sensitive and accurate tumor localization compared to gamma radiotracers. In that context, we are currently developing an intraoperative positron imaging probe using SiPM photosensors to perform tumor localization and post-operative control of the surgical cavity. Because compactness is a key feature when trying to detect positron emitters with high sensitivity in small surgical cavities, we chose to study the simplest detector design based on the use of a very thin organic scintillator coupled to the photosensor. Different designs of the positron imaging probe, including scintillator material and thickness, light spreading window and optical reflector, were investigated with Monte-Carlo simulations and measurements. Their impact on the probe performances were optimized in terms of positron sensitivity, gamma rays background noise contamination, spatial resolution and bias and uniformity. The ability of the probes to detect small radiolabeled tumors was also investigated by simulating different phantom uptake configurations.

This article reports on the design and features of a very compact and light gamma camera based on SiPM arrays and miniaturized readout electronics dedicated to tumor localization during radio-guided cancer surgery. This gamma camera, called MAGICS, is composed of four (2×2) photo-detection elementary modules coupled to an inorganic scintillator. The 256 channels photo-detection system covers a sensitive area of 54×53m2. Each elementary module is based on four (2×2) SiPM monolithic arrays, each array consisting of 16 SiPM photo-sensors (4×4) with 3×3mm2 sensitive area, coupled to a miniaturized readout electronics and a dedicated ASIC. The overall dimensions of the electronics fit the size of the detector, enabling to assemble side-by-side several elementary modules in a close-packed arrangement. The preliminary performances of the system are very encouraging, showing an energy resolution of 9.8% and a spatial resolution of less than 1mm at 122keV.

This work presents a model describing the IV characteristics of SiPM detectors allowing to easily determine important physical parameters like breakdown voltage VBD and triggering probability PGeiger. The proposed model provides a good description of experimental data taken with SiPMs of different technologies (i.e. Hamamatsu HPK, KETEK) and geometries. Good agreement over a very wide range of current (i.e. 10(-11)A up to 10(-4)A) was observed between the experimental and calculated values. Silvaco TCAD simulation tool was used to acquire further insights into the physics behind the IV current and to identify the different components of DC current (i.e. Shockley-Read-Hall thermal generated carriers, trap-assisted and band-to-band tunneling). The results of our model are shown to be in good agreement with VBD and PGeiger determined from AC measurements.

The LHC accelerator complex will be upgraded between 2020-2022, to the High-Luminosity-LHC, to considerably increase statistics for the various physics analyses. To operate under these challenging new conditions, and maintain excellent performance in track reconstruction and vertex location, the ATLAS pixel detector must be substantially upgraded and a full replacement is expected. Processing techniques for novel pixel designs are optimised through characterisation of test structures in a clean room and also through simulations with Technology Computer Aided Design (TCAD). A method to study non-perpendicular tracks through a pixel device is discussed. Comparison of TCAD simulations with Secondary Ion Mass Spectrometry (SIMS) measurements to investigate the doping profile of structures and validate the simulation process is also presented.

This work reports on the behavior of the Multi-Pixel Photon Counter (MPPC) detectors produced by Hamamatsu HPK in a temperature range from +55°C down to −175°C. Devices of 1×1mm2 and 3×3mm2 total area and 50×50μm2 μcell size have been studied. Electrical parameters such as breakdown voltage, gain, capacitance, pulse shape, quenching resistance and dark count rate were measured and some of them showed important temperature variation. Besides this temperature dependence, it is shown that MPPC detectors can operate with a stable gain independent of T if the overvoltage is kept constant. Moreover, at a given temperature, the device of 3×3mm2 (production year 2011) presents seven times less dark rate/mm2 with respect to the one of 1×1mm2 (production year 2007), showing an important technological improvement implemented by HPK during four year׳s time interval.

The emergence of promising specific tumor-seeking agents labeled with positron emitters is giving rise to a renewed interest for radioguided surgery using beta probes. Intraoperative positron probes present intrinsic advantages over gamma detection to provide real time information about the tumor extend and the assessment of reasonable surgical resection margins. In that context, we are currently developing two different intraoperative positron probes based on SiPM photosensors: a small positron imaging probe to perform tumor localization and post-operative control of the surgical cavity, and a miniaturized counting probe to guide in real time the excision of the lesion. We report here design and characterization of the performance of these probes. The imaging probe consists of the stack of two SiPM arrays coupled to a plastic and a GSOZ scintillators in order to remove the gamma ray background noise with a subtraction method. The counting probe is built around seven detection elements, each composed of a plastic scintillating fiber and a SiPM, and is designed to be directly coupled to an excision tool. We show that the imaging probe offers submillimetric intrinsic resolution and bias over its usable field of view. These performances are insensitive to temperature variations due to a real-time temperature-compensated circuit integrated in the readout electronics. The positron sensitivity measured with 18F-FDG (12.6 cps/nCi) is superior to those of the best positron probes reported. Detailed description of the first prototypes of the two positron probes as well as complete characterization of their performances, including evaluation of the gamma ray rejection efficiency with realistic phantoms, will be presented at the conference.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Contribution du CNRS/IN2P3 à l’upgrade d’ATLAS. Proposition soumise au Conseil Scientifique de l’IN2P3 du 21 Juin 2012 C. Bee, F. Bombard, N. Bousson, P. Breugnon, Y. Coadou, J.-C. Clemens, F. Djama, L. Feligioni, D. Fougeron, T. Gastaldi, et al.

The ATLAS Collaboration will upgrade its semiconductor pixel tracking detector with a new Insertable B-layer (IBL) between the existing pixel detector and the vacuum pipe of the Large Hadron Collider. The extreme operating conditions at this location have necessitated the development of new radiation hard pixel sensor technologies and a new front-end readout chip, called the FE-I4. Planar pixel sensors and 3D pixel sensors have been investigated to equip this new pixel layer, and prototype modules using the FE-I4A have been fabricated and characterized using 120 GeV pions at the CERN SPS and 4 GeV positrons at DESY, before and after module irradiation. Beam test results are presented, including charge collection efficiency, tracking efficiency and charge sharing.

This work reports on Silicon Photomultipliers (SiPM) timing resolution measurements performed at the picosecond level at Laboratory of Linear Accelerator (LAL), In2p3- CNRS.The dependence of Single Photoelectron Timing Resolution (SPTR) with the applied voltage, wavelength of the light and the temperature was measured for detectors from Hamamatsu Photonics, AdvanSiD and Sensl with an active area of 1 and 9 mm(2).The SPTR improves with the bias voltage increase. No significant variation of SPTR was observed with the temperature change. We also observed a weak variation of it as a function of the wavelength of the light. The best SPTR measured was about 120 ps (FWHM). (C) 2012 Elsevier B.V. All rights reserved.

Intraoperative localization of malignant tissues labeled with positron radiotracers opens up new prospects to improve the efficiency of cancer surgery. Because Silicon Photomultipliers (SiPM) introduced a breakthrough for the development of miniaturized imaging devices, we are currently designing two intraoperative beta probes based on this technology: a light imaging device with a small field of view (~5cm2) to perform tumor localization and post-operative control of the surgical cavity, and a miniaturized counting probe to guide in real time the excision of the tumor lesion. The first step of our project was focused on the characterization and optimization of SiPM devices as photodetectors for intraoperative beta detection. We studied the influence of temperature and bias voltage on the thermal and correlated noises and photon detection efficiency of different SiPM devices. The impact of these two parameters on the overall beta sensitivity was quantified as a function of the intensity of the scintillation light following a simple physical model. According to the results of this comprehensive study, the optimization of the detection head design of the two intraoperative probes was studied using Monte Carlo simulations. Detailed description of the simulation study as well as the performance characterization of the first prototypes will be presented at the conference.

A physics-based device simulation was used to study the charge carrier distribution and the electric field configuration inside simplified two-dimensional models for pixel layouts based on the ATLAS pixel sensor. In order to study the behavior of such detectors under different levels of irradiation, a three-level defect model was implemented into the simulation. Using these models, the number of guard rings, the dead edge width and the detector thickness were modified to investigate their influence on the detector depletion at the edge and on its internal electric field distribution in order to optimize the layout parameters. Simulations indicate that the number of guard rings can be reduced by a few hundred microns with respect to the layout used for the present ATLAS sensors, with a corresponding extension of the active area of the sensors. A study of the inter-pixel capacitance and of the capacitance between the implants and the high-voltage contact as a function of several parameters affecting the geometry and the doping level of the implants was also carried out. The results are needed in order to evaluate the noise and the cross-talk among neighboring pixels when connected to the front-end electronics.

This work reports on the characterization of the Multi-Pixel Photon Counter (MPPC) detectors as a function of the temperature and bias voltage. Devices of 1×1 mm 2 and 3×3 mm 2 total area and 50×50 μm 2 μcell size produced by Hamamatsu Photonics have been studied. The temperature has been varied from -110°C to -50°C using a cryostat cooled by liquid nitrogen and from 0 to 38°C using a climatic chamber. Important electrical parameters of the MPPC detectors as gain, breakdown voltage, quenching resistance, capacitance and dark count rate have been measured.

Electric field magnitude and depletion in the bulk of silicon pixel detectors, which influence its breakdown behaviour, was studied using finite-element method to solve the drift-diffusion equation coupled to Poisson's equation in a simplified two dimensional model of the ATLAS pixel sensor. Based on this model, the number of guard rings and dead edges width were modified to investigate their influence on the detector's depletion at the edge and on its internal electrical field distribution. Finally, the 3 level model was implemented into the simulation to study the behaviour of such detector under different level of irradiation.

A very high resolution small animal PET scanner that employs matrices of silicon photomultipliers as photodetectors is under development at the University of Pisa and INFN Pisa. The first SiPM matrices composed of 16 (4×4) 1mm×1mm pixel elements on a common substrate have been produced at FBK-irst, and are being evaluated for this application. The MAROC2 ASIC developed at LAL-Orsay has been employed for the readout of the SiPM matrices. The devices have been tested with pixelated and continuous LYSO crystals. The results show the good performance of the matrices and lead to the fabrication of matrices with 64 SiPM elements.

This work reports on the development of an electro-optical set-up for the characterization of the Silicon PhotoMultiplier (SiPM) devices as well as on the comparative study of the characteristics of different SiPM prototypes. The electrical set-up allows the measurement of the static (breakdown voltage, overvoltage quenching resistance) and dynamic (gain, dark count rate) characteristics. The optical set-up allows the estimation of the photon detection efficiency as a function of the wavelength and the operation voltage. The comparative study has been performed on SiPM devices covering an area of 1×1mm2 and supplied during 2007 by Photonique S.A. (Switzerland), FBK-irst (Italy), SensL (Ireland) and Hamamatsu (Japan).

This work reports on the electrical as well as the optical characterizations of a prototype matrix of Silicon PhotoMultipliers (SiPM). The electrical test consists of the measurement of the static (breakdown voltage, quenching resistance, post-breakdown dark current) as well as the dynamic characteristics (gain, dark count rate). The optical test consists of the estimation of the photon detection efficiency as a function of wavelength as well as operation voltage.

The Alpha Magnetic Spectrometer is designed for a long duration measurement of the cosmic-ray spectra at an altitude of 400km. The particle rigidity and specific energy loss are measured by a silicon tracker located in a 0.8T field. Ground results for the position resolution, detection efficiency and charge determination for singly and doubly charged relativistic particles are presented and discussed in the context of the spaceborne detector.