F. Cenna

Ultra-Fast Silicon Detectors for 4D tracking

We review the progress toward the development of a novel type of silicon detectors suited for tracking with a picosecond timing resolution, the so called Ultra-Fast Silicon Detectors. The goal is to create a new family of particle detectors merging excellent position and timing resolution with GHz counting capabilities, very low material budget, radiation resistance, fine granularity, low power, insensitivity to magnetic field, and affordability. We aim to achieve concurrent precisions of ~ 10 ps and ~ 10 μm with a 50 μm thick sensor. Ultra-Fast Silicon Detectors are based on the concept of Low-Gain Avalanche Detectors, which are silicon detectors with an internal multiplication mechanism so that they generate a signal which is factor ~ 10 larger than standard silicon detectors.

TOFFEE: a full custom amplifier-comparator chip for timing applications with silicon detectors

We report on the design of a full custom amplifier-comparator readout chip for silicon detectors with internal gain designed for precise timing applications. The ASIC has been developed in UMC 110 nm CMOS technology and is aimed to fulfill the CMS-TOTEM Precision Proton Spectrometer (CT-PPS) time resolution requirements (~ 30 ps per detector plane). It features LVDS outputs and the signal dynamic range matches the requirements of the High Precision TDC (HPTDC) system. The preliminary measurements results with a test board are included.

Temperature dependence of the response of ultra fast silicon detectors

The Ultra Fast Silicon Detectors (UFSD) are a novel concept of silicon detectors based on the Low Gain Avalanche Diode (LGAD) technology, which are able to obtain time resolution of the order of few tens of picoseconds. First prototypes with different geometries (pads/pixels/strips), thickness (300 and 50 μm) and gain (between 5 and 20) have been recently designed and manufactured by CNM (Centro Nacional de Microelectronica, Barcelona) and FBK (Fondazione Bruno Kessler, Trento). Several measurements on these devices have been performed in laboratory and in beam test and a dependence of the gain on the temperature has been observed. Some of the first measurements will be shown (leakage current, breakdown voltage, gain and time resolution on the 300 μm from FBK and gain on the 50 μm-thick sensor from CNM) and a comparison with the theoretically predicted trend will be discussed.

Developments and first measurements of Ultra-Fast Silicon Detectors produced at FBK

Segmented silicon sensors with internal gain, the so called Ultra-FAST Silicon Detectors (UFSD), have been produced at FBK for the first time. UFSD are based on the concept of Low-Gain Avalanche Detectors (LGAD), which are silicon detectors with an internal, low multiplication mechanism (gain ~ 10). This production houses two main type of devices: one type where the gain layer is on the same side of the read-out electrodes, the other type where the gain layer is on the side opposite to the pixellated electrodes (reverse-LGAD). Several technological splits have been included in the first production run, with the aim to tune the implantation dose of the multiplication layer, which controls the gain value of the detector. An extended testing on the wafers has been performed and the results are in line with simulations: the fabricated detectors show good performances, with breakdown voltages above 1000 Volts, and gain values in the range of 5–60 depending on the technological split. The detectors timing resolution has been measured by means of a laboratory setup based on an IR picosecond laser. The sample with higher gain shows time resolution of 55 ps at high reverse bias voltage, indicating very promising performance for future particle tracking applications.

Development of Ultra-Fast Silicon Detectors for 4D tracking

In this contribution we review the progress towards the development of a novel type of silicon detectors suited for tracking with a picosecond timing resolution, the so called Ultra-Fast Silicon Detectors. The goal is to create a new family of particle detectors merging excellent position and timing resolution with GHz counting capabilities, very low material budget, radiation resistance, fine granularity, low power, insensitivity to magnetic field, and affordability. We aim to achieve concurrent precisions of ~ 10 ps and ~ 10 μm with a 50 μm thick sensor. Ultra-Fast Silicon Detectors are based on the concept of Low-Gain Avalanche Detectors, which are silicon detectors with an internal multiplication mechanism so that they generate a signal which is factor ~10 larger than standard silicon detectors. The basic design of UFSD consists of a thin silicon sensor with moderate internal gain and pixelated electrodes coupled to full custom VLSI chip. An overview of test beam data on time resolution and the impact on this measurement of radiation doses at the level of those expected at HL-LHC is presented. First I-V and C-V measurements on a new FBK sensor production of UFSD, 50 μm thick, with B and Ga, activated at two diffusion temperatures, with and without C co-implantation (in Low and High concentrations), and with different effective doping concentrations in the Gain layer, are shown. Perspectives on current use of UFSD in HEP experiments (UFSD detectors have been installed in the CMS-TOTEM Precision Protons Spectrometer for the forward physics tracking, and are currently taking data) and proposed applications for a MIP timing layer in the HL-LHC upgrade are briefly discussed.

The 4D pixel challenge

Is it possible to design a detector able to concurrently measure time and position with high precision? This question is at the root of the research and development of silicon sensors presented in this contribution. Silicon sensors are the most common type of particle detectors used for charged particle tracking, however their rather poor time resolution limits their use as precise timing detectors. A few years ago we have picked up the gantlet of enhancing the remarkable position resolution of silicon sensors with precise timing capability. I will be presenting our results in the following pages.

Laboratory and beam test results of TOFFEE ASIC and ultra fast silicon detectors

In this report we present measurements performed on the full custom ASIC TOFFEE, designed to pre-amplify and discriminate signals of Ultra Fast Silicon Detectors. The ASIC has been characterized in laboratory with custom test boards, and with infrared laser light hitting the sensor emulating a minimum ionizing particle signal. Laser measurements show that a jitter term better than 50 (40) ps is achievable with a 10 (12) fC input charge. We also present some preliminary results on the TOFFEE performances, as obtained during recent beam tests with a 180 GeV/c pion beam, on the SPS-H8 beam line at CERN.

TOFFEE: A fully custom amplifier-comparator chip for silicon detectors with internal gain

We report on the design and tests results of a fully custom amplifier-comparator readout chip designed to be coupled to silicon detectors with internal charge multiplication for precise timing applications. The ASIC has been developed in UMC 110nm CMOS technology and aims to fulfill the CMS-TOTEM Precision Proton Spectrometer (CT-PPS) time resolution requirements (∼30 ps per detector plane). Both LVDS outputs and the signal dynamic range match the requirements of the High Precision TDC (HPTDC) system. Noise and signal amplitude measurements with a test board are included.