We present a novel design of fine segmented low gain avalanchediodes ('GAD) based on trench-isolation technique. The proposed design reduces the width of the no-gain inter-pad region down to less ...than 10 μm, from the 20-80 μm of the current 'GAD technology, enabling the production of sensors with small pixel pitch and high fill-factor. Prototypes of this new technologywere produced in the FBK laboratories. Their electrical characterization in terms of I-V, gain measurement and response to a focused laser, indicates that the trenches provide electrical isolation among pixels without any increase in the dark current level and without affecting the gain of the sensor. In addition, I-V measurements of p-i-n diodes with the same trench-isolation structure demonstrate that such termination scheme can withstand more than 500 Volts without reaching breakdown. This is well above the typical operating bias voltage of 'GADs, thus confirming that trench-isolation is a promising solution for finely pixelated 'GAD sensors.
Radiation resistant LGAD design Ferrero, M.; Arcidiacono, R.; Barozzi, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2019, Letnik:
919
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In this paper, we report on the radiation resistance of 50-micron thick Low Gain Avalanche Diodes (LGAD) manufactured at the Fondazione Bruno Kessler (FBK) employing different dopings in the gain ...layer. LGADs with a gain layer made of Boron, Boron low-diffusion, Gallium, Carbonated Boron and Carbonated Gallium have been designed and successfully produced at FBK. These sensors have been exposed to neutron fluences up to ϕn∼3⋅1016n∕cm2 and to proton fluences up to ϕp∼9⋅1015p∕cm2 to test their radiation resistance. The experimental results show that Gallium-doped LGAD are more heavily affected by the initial acceptor removal mechanism than those doped with Boron, while the addition of Carbon reduces this effect both for Gallium and Boron doping. The Boron low-diffusion gain layer shows a higher radiation resistance than that of standard Boron implant, indicating a dependence of the initial acceptor removal mechanism upon the implant density.
In this paper we present the numerical simulation of silicon detectors with internal gain as the main tool for 4-dimensional (4D) particle trackers design and optimization. The Low-Gain Avalanche ...Diode (LGAD) technology and its present limitations are reviewed with the aim of introducing the Resistive AC-Coupled Silicon Detectors (RSD) paradigm as a case study of our investigation. Authors here present Spice-like and 2D/3D Technological Computer-Aided Design (TCAD) simulations to characterize sensors in terms of both their electrostatic behavior, capacitive (dynamic) coupling and radiation-hardness performances, showing the methodological approach used in order to extract the set of layout rules allowing the release of RSD1, the incoming production run at Fondazione Bruno Kessler (FBK) of next-generation silicon detectors for 4D tracking with intrinsic 100% fill-factor.
The use of non-evaporable getter (NEG) pumps is common in many UHV applications, and the properties of the new sintered getters based on the ZAO®alloy make them appealing for applications dealing ...with large fluxes of hydrogen and its isotopes, as typically occurs in fusion research. In particular, the use of NEG pumps is interesting for the vacuum system of negative ion-based neutral beam injectors, which require huge deuterium gas throughputs for long durations. The key advantages of a NEG pumping solution are the high specific pumping speed and capacity, the ability to withstand a large number of absorption/desorption cycles, the ease of integration. In addition, NEG do not release hydrogen unless power is supplied to heat them, addressing an important safety issue related to uncontrolled release in case of power outage or subsystem failures.
This paper reports the experimental characterization of ZAO®sintered getters, in pressure regimes and sorption amounts relevant for the use in the next generation NBI. Single discs and complete pumps were characterized in different conditions of H2/D2 pressure between 10−4 and 10-1Pa and operating temperatures up to 150°C. In particular, the feasibility of getter regeneration within time windows compatible with current NBI operation scenarios was demonstrated.
Abstract
RSDs (Resistive AC-Coupled Silicon Detectors) are n-in-p silicon sensors based on the LGAD (Low-Gain Avalanche Diode) technology, featuring a continuous gain layer over the whole sensor ...area. The truly innovative feature of these sensors is that the signal induced by an ionising particle is seen on several pixels, allowing the use of reconstruction techniques that combine the information from many read-out channels.
In this contribution, the first application of a machine learning technique to RSD devices is presented. The spatial resolution of this technique is compared to that obtained with the standard RSD reconstruction methods that use analytical descriptions of the signal sharing mechanism. A Multi-Output regressor algorithm, trained with a combination of simulated and real data, leads to a spatial resolution of less than 2 μm for a sensor with a 100 μm pixel.
The prospects of future improvements are also discussed.
The upgrades of the CMS and ATLAS experiments for the high luminosity phase of the Large Hadron Collider will employ precision timing detectors based on Low Gain Avalanche Detectors (LGADs). We ...present a suite of results combining measurements from the Fermilab Test Beam Facility, a beta source telescope, and a probe station, allowing full characterization of the HPK type 3.1 production of LGAD prototypes developed for these detectors. We demonstrate that the LGAD response to high energy test beam particles is accurately reproduced with a beta source. We further establish that probe station measurements of the gain implant accurately predict the particle response and operating parameters of each sensor, and conclude that the uniformity of the gain implant in this production is sufficient to produce full-sized sensors for the ATLAS and CMS timing detectors.
Abstract
RSDs are LGAD silicon sensors with 100% fill factor, based on the principle of AC-coupled resistive read-out. Signal sharing and internal charge multiplication are the RSD key features to ...achieve picosecond-level time resolution and micron-level spatial resolution, thus making these sensors promising candidates as 4D-trackers for future experiments. This paper describes the use of a neural network to reconstruct the hit position of ionizing particles, an approach that can boost the performance of the RSD with respect to analytical models. The neural network has been trained in the laboratory and then validated on test beam data. The device-under-test in this work is a 450 μm-pitch matrix from the FBK RSD2 production, which achieved a resolution of about 65 μm at the DESY Test Beam Facility, a 50% improvement compared to a simple analytical reconstruction method, and a factor two better than the resolution of a standard pixel sensor of equal pitch size with binary read-out. The test beam result is compatible with the laboratory ones obtained during the neural network training, confirming the ability of the machine learning model to provide accurate predictions even in environments very different from the training one. Prospects for future improvements are also discussed.
Non Evaporable Getter (NEG) technology has been studied as an alternative pumping solution in facilities for fusion research since the 80 s. The recent development of a new generation of Zr-V-Ti-Al ...(ZAO®) getter alloys with improved features makes NEG technology an attractive option in several fusion applications, including in particular, Neutral Beam Injectors (NBI). The main advantages of ZAO® NEG pumps are related to the high pumping speed for H2, the high capacity that results into a very promising availability, the ease of integration and the low power consumption. From the vacuum point of view, research fusion facilities are in the high vacuum pressure range (e.g. 1∙10−6 ÷1∙10-5 Pa background pressure) and may present leaks and significant outgassing from internal components. Specific activities have been devoted to test the NEG pump robustness, i.e. the ability to maintain adequate performances in conditions very far from UHV. In particular, the effects of carbon oxides and hydrocarbon adsorption have been investigated, as well as the outgassing from materials like polyimide or even fluorinated polymers as PTFE. The results show that the ZAO® getter material is intrinsically robust, able to perform repeated H2 adsorption/desorption cycles with stable performances, and recover most of the original pumping speed even after significant exposure to hydrocarbons and fluorine species. These outcomes give promising indications for the future use of NEG solutions in real fusion facilities.
Experimental Study of Acceptor Removal in UFSD Jin, Y.; Ren, H.; Christie, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2020, Letnik:
983, Številka:
C
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The performance of the Ultra-Fast Silicon Detectors (UFSD) after irradiation with neutrons and protons is compromised by the removal of acceptors in the thin layer below the junction responsible for ...the gain. This effect is tested both with capacitance–voltage, C–V, measurements of the doping concentration and with measurements of charge collection, CC, using charged particles. We find a perfect linear correlation between the bias voltage to deplete the gain layer determined with C–V and the bias voltage to collect a defined charge, measured with charge collection. An example for the usefulness of this correlation is presented.
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