Low Gain Avalanche Detector (LGAD) is the baseline sensing technology of the recently proposed Minimum Ionizing Particle (MIP) end-cap timing detectors (MTD) at the Atlas and CMS experiments. The ...current MTD sensor is designed as a multi-pad matrix detector delivering a poor position resolution, due to the relatively large pad area, around 1 mm2; and a good timing resolution, around 20–30 ps. Besides, in his current technological incarnation, the timing resolution of the MTD LGAD sensors is severely degraded once the MIP particle hits the inter-pad region since the signal amplification is missing for this region. This limitation is named as the LGAD fill-factor problem. To overcome the fill factor problem and the poor position resolution of the MTD LGAD sensors, a p-in-p LGAD (iLGAD) was introduced. Contrary to the conventional LGAD, the iLGAD has a non-segmented deep p-well (the multiplication layer). Therefore, iLGADs should ideally present a constant gain value over all the sensitive region of the device without gain drops between the signal collecting electrodes; in other words, iLGADs should have a 100% fill-factor by design. In this paper, tracking and timing performance of the first iLGAD prototypes is presented.
The characterization of spacial and timing resolution of the novel Trench Isolated LGAD (TI-LGAD) technology is presented. This technology has been developed at FBK with the goal of achieving 4D ...pixels, where an accurate position resolution is combined in a single device with the precise timing determination for Minimum Ionizing Particles (MIPs). In the TI-LGAD technology, the pixelated LGAD pads are separated by physical trenches etched in the silicon. This technology can reduce the interpixel dead area, mitigating the fill factor problem. The TI-RD50 production studied in this work is the first one of pixelated TI-LGADs. The characterization was performed using a scanning TCT setup with an infrared laser and a 90Sr source setup.
Development of LGAD sensors at FBK Bisht, A.; Borghi, G.; Boscardin, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2022, Letnik:
1039
Journal Article
Recenzirano
The High Luminosity upgrade of the Large Hadron Collider highlighted the need for a time-tagging of tracks with a precision of tens of picoseconds. This requirement motivated the development of ...radiation hard silicon sensors dedicated to the time-of-interaction measurement of minimum ionizing particles. Low Gain Avalanche Diodes (LGADs) are silicon sensors with internal charge multiplication and are the baseline for the timing systems of the ATLAS and CMS experiments. These sensors use their gain to improve the signal to noise ratio (SNR) of detector systems and have been engineered to withstand the harsh radiation environment of the experiments. Fondazione Bruno Kessler (FBK) developed the LGAD technology through several production runs. The improved SNR and excellent time resolution made LGADs suitable also for medical, X-ray, and space applications. A feature of LGADs is the presence of a termination structure between regions with gain that results in areas without gain between the readout channels, reducing the fill factor of the devices. Different strategies to improve the fill factor of LGADs are being developed, such as double sided LGADs, resistive AC-coupled LGADs, and trench isolated LGADs. This paper summarizes the experience acquired at FBK with the realization of more than ten sensor batches. Selected results in radiation hardness, time resolution, fill factor, and different LGAD applications will be discussed.
Novel strategies for fine-segmented Low Gain Avalanche Diodes Paternoster, G.; Borghi, G.; Arcidiacono, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2021, Letnik:
987
Journal Article
Recenzirano
Low Gain Avalanche Diodes (LGADs) are now considered a viable solution for 4D-tracking thanks to their excellent time resolution and good resistance to high radiation fluence. However, the currently ...available LGAD technology is well suited only for applications that require coarse space precision, pixels with pitch in the range 500µm–1mm, due to the presence of a no-gain region between adjacent pixels of about 50μm, in which the gain is completely suppressed. In this paper, we will discuss the segmentation issues in the LGAD technology and we will present two new segmentation strategies aimed at producing LGADs with high spatial resolution and high fill factor. The first presented design is the so-called Trench-Isolated LGAD (TI-LGAD). Here, the pixel isolation is provided by trenches, physically etched in the silicon and then filled with silicon oxide. The second design is the Resistive AC-coupled Silicon Detector (RSD), an evolution of LGADs, where the segmentation is obtained by means of AC-coupled electrodes. Prototypes of both designs have been produced at FBK and characterized at the Laboratories for Innovative Silicon Sensors (INFN and University of Turin) by means of a laser setup to estimate the space resolution and the fill factor. The functional characterization shows that both the technologies yield fully working small pixel LGADs (down to 50µm), providing the first examples of sensors able to concurrently measure space and time with excellent precision.
Recent interest in pile-up mitigation through fast timing at the HL-LHC has focused attention on technologies that now achieve minimum ionising particle (MIP) time resolution of 30 picoseconds or ...less. The constraints of technical maturity and radiation tolerance narrowed the options in this rapidly developing field for the ATLAS and CMS upgrades to low gain avalanche detectors and silicon photomultipliers. In a variety of applications where occupancies and doses are lower, devices with pixel elements of order 1 cm2, nevertheless achieving 30ps, would be attractive.
In this paper, deep diffused Avalanche Photo Diodes (APDs) are examined as candidate timing detectors for HL-LHC applications.
Devices with an active area of 8 × 8 mm2 are characterised using a pulsed infrared laser and, in some cases, high energy particle beams. The timing performance as well as the uniformity of response are examined.
The effects of radiation damage on current, signal amplitude, noise, and timing of the APDs are evaluated using detectors with an active area of 2 × 2 mm2. These detectors were irradiated with neutrons up to a 1-MeV neutrons fluence Φeq=1015 cm−2. Their timing performance was characterised using a pulsed infrared laser.
While a time resolution of 27±1 ps was obtained in a beam test using an 8 × 8 mm2 sensor, the present study only demonstrates that gain loss can be compensated by increased detector bias up to fluences of Φeq=6⋅1013 cm−2. So it possibly falls short of the Φeq=1014 cm−2 requirement for the CMS barrel over the lifetime of the HL-LHC.
The basic principle of operation of silicon sensors with resistive read-out is built-in charge sharing. Resistive Silicon Detectors (RSD, also known as AC-LGAD), exploiting the signals seen on the ...electrodes surrounding the impact point, achieve excellent space and time resolutions even with very large pixels. In this paper, a TCT system using a 1064 nm picosecond laser is used to characterize RSD sensors produced by Fondazione Bruno Kessler. The paper first introduces the parametrization of the errors in the determination of the position and time coordinates in RSD, then outlines the reconstruction method, and finally presents the results. Three different pixel pitches are used in the analysis: 200 × 340, 450 × 450, and 1300 × 1300 μm2. At gain = 30, the 450 × 450 μm2 pixel achieves a time jitter of 20 ps and a spatial resolution of 15 μm concurrently, while the 1300 × 1300 μm2 pixel achieves 30 ps and 30 μm, respectively. The implementation of cross-shaped electrodes improves considerably the response uniformity over the pixel surface.
The first batch of compensated LGAD sensors Sola, V.; Paternoster, G.; Morozzi, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
July 2024, 2024-07-00, Letnik:
1064
Journal Article
Recenzirano
Odprti dostop
A new development of radiation-resistant silicon sensors is presented. The new sensors exploit the Low-Gain Avalanche Diode (LGAD) technology, with internal multiplication of the charge carriers, in ...combination with thin substrates, intrinsically less affected by radiation. An innovative design of the gain implant typical of the LGADs has been developed and fabricated, employing the compensation of acceptor and donor dopants to reproduce the effective acceptor doping dose of standard LGAD sensors.
At the end of 2022, the Fondazione Bruno Kessler (Italy) delivered the first batch of compensated LGAD sensors on 30μm thick p-type epitaxial substrates. Electrical and transient characterisation of the sensors has been performed before and after irradiation up to 5 ⋅1015 1 MeV equivalent n/cm2.
The ultimate goal is to develop and produce compensated LGAD sensors that can efficiently operate above fluences of 1017 1 MeV equivalent n/cm2.
DC-coupled resistive silicon detectors for 4D tracking Menzio, L.; Arcidiacono, R.; Borghi, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2022, Letnik:
1041
Journal Article
Recenzirano
In this work, we introduce a new design concept: the DC-coupled Resistive Silicon Detectors, based on the LGAD technology. This new design intends to address a few known drawbacks of the first ...generation of AC-coupled Resistive Silicon Detectors (RSD). The sensor behaviour is simulated using a fast hybrid approach based on a combination of two packages, Weightfield2 and LTSpice. The simulation demonstrates that the key features of the RSD design are maintained, yielding excellent space and time resolutions: a few tens of ps and a few microns. In this report, we will outline the optimization methodology and the results of the simulation. We will also present detailed studies on the effects induced by the choice of key design parameters on the space and time resolutions provided by this sensor.
Deep diffused Avalanche photodiodes for charged particles timing Centis Vignali, M.; Dias De Almeida, P.; Franconi, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The upgrades of ATLAS and CMS for the High Luminosity LHC (HL-LHC) highlighted physics objects timing as a tool to resolve primary interactions within a bunch crossing. Since the expected pile-up is ...around 200, with an r.m.s. time spread of 180ps, a time resolution of about 30ps is needed. The timing detectors will experience a 1-MeV neutron equivalent fluence of about Φeq=1014 and 1015cm−2 for the barrel and end-cap regions, respectively. In this contribution, deep diffused Avalanche Photo Diodes (APDs) produced by Radiation Monitoring Devices are examined as candidate timing detectors for HL-LHC applications. To improve the detector’s timing performance, the APDs are used to directly detect the traversing particles, without a radiator medium where light is produced. Devices with an active area of 8 × 8mm2 were characterized in beam tests. The timing performance and signal properties were measured as a function of position on the detector using a beam telescope and a microchannel plate photomultiplier (MCP-PMT). Devices with an active area of 2 × 2mm2 were used to determine the effects of radiation damage and characterized using a ps pulsed laser. These detectors were irradiated with neutrons up to Φeq=1015cm−2.
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