In this paper we report on the timing resolution obtained in a beam test with pions of 180 GeV/c momentum at CERN for the first production of 45 μm thick Ultra-Fast Silicon Detectors (UFSD). UFSD are ...based on the Low- Gain Avalanche Detector (LGAD) design, employing n-on-p silicon sensors with internal charge multiplication due to the presence of a thin, low-resistivity diffusion layer below the junction. The UFSD used in this test had a pad area of 1.7 mm2. The gain was measured to vary between 5 and 70 depending on the sensor bias voltage. The experimental setup included three UFSD and a fast trigger consisting of a quartz bar readout by a SiPM. The timing resolution was determined by doing Gaussian fits to the time-of-flight of the particles between one or more UFSD and the trigger counter. For a single UFSD the resolution was measured to be 34 ps for a bias voltage of 200 V, and 27 ps for a bias voltage of 230 V. For the combination of 3 UFSD the timing resolution was 20 ps for a bias voltage of 200 V, and 16 ps for a bias voltage of 230 V.
Abstract Thanks to their advantages in terms of easiness of manufacturing and reduced production costs, Monolithic Active Pixel Sensors (MAPS) represent an appealing solution for radiation imaging ...applications, which require to cover large areas with pixelated detectors. In the next upgrade of the ALICE detector, that will have to deal with the higher event rate resulting from the planned increase in the LHC luminosity, it is foreseen to include two additional sensor layers to perform Time of Flight (ToF) measurements. Trying to reach the challenging timing resolution required by the ALICE ToF layers, an internal gain layer has been included in the test structures of the third engineering run of the ARCADIA project to improve the timing performance of this MAPS technology. In the paper we will present an overview of the main results obtained from the electrical and the dynamic characterization of the fabricated devices, which have been compared with the behavior expected from the preliminary TCAD simulations carried out in the design phase. The experimental results confirmed the feasibility of embedding a gain layer in the ARCADIA 110 nm CMOS technology to develop monolithic LGADs.
Abstract In this paper we report on a set of characterisations carried out on the first monolithic LGAD prototype integrated in a customised 110 nm CMOS process having a depleted active volume ...thickness of 48 μm. This prototype is formed by a pixel array where each pixel has a total size of 100 μm× 250 μm and includes a high-speed front-end amplifier. After describing the sensor and the electronics architecture, both laboratory and in-beam measurements are reported and described. Optical characterisations performed with an IR pulsed laser setup have shown a sensor internal gain of about 2.5. With the same experimental setup, the electronic jitter was found to be between 50 ps and 150 ps, depending on the signal amplitude. Moreover, the analysis of a test beam performed at the Proton Synchrotron (PS) T10 facility of CERN with 10 GeV/c protons and pions indicated that the overall detector time resolution is in the range of 234 ps to 244 ps. Further TCAD investigations, based on the doping profile extracted from C(V) measurements, confirmed the multiplication gain measured on the test devices. Finally, TCAD simulations were used to tune the future doping concentration of the gain layer implant, targeting sensors with a higher avalanche gain. This adjustment is expected to enhance the timing performance of the sensors of the future productions, in order to cope with the high event rate expected in most of the near future high-energy and high-luminosity physics experiments, where the time resolution will be essential to disentangle overlapping events and it will also be crucial for Particle IDentification (PID).
This paper describes the new concept of the double LGAD (low-gain avalanche diodes). The goal was to increase the charge at the input of the electronics, keeping a time resolution equal to or better ...than a standard (single) LGAD; this has been realized by adding the charges of two coupled LGADs while still using a single front-end electronics. The study here reported has been done starting from single LGAD with a thickness of 25 µm, 35 µm and 50 µm.
This paper presents the measurements on first very thin Ultra-Fast Silicon Detectors (UFSDs) produced by Fondazione Bruno Kessler; the data have been collected in a beam test setup at the CERN PS, ...using beam with a momentum of 12 GeV/c. UFSDs with a nominal thickness of 25 and 35
μ
m and an area of 1
×
1
mm
2
have been considered, together with an additional HPK 50-
μ
m thick sensor, taken as reference. Their timing performances have been studied as a function of the applied voltage and gain. A time resolution of about 25 ps and of 22 ps at a voltage of 120 and 240 V has been obtained for the 25 and 35
μ
m thick UFSDs, respectively.
Abstract
The direct response of Silicon PhotoMultipliers being
traversed by a MIP charged particle have been studied in a
systematic way for the first time. Using beam test data, time
resolution and ...the crosstalk probability have been measured. A
characterization of the SiPM by means of a laser beam is also
reported. The results obtained for different sensors indicate a
measured time resolution around 40–70 ps. Although particles are
expected to traverse only one SPAD per event, crosstalk measurements
on different sensors indicate an unexpected higher value with
respect to the one related to the sensor noise.
In this paper, different Silicon PhotoMultiplier (SiPM) sensors have been tested with charged particles to characterize the Cherenkov light produced in the sensor protection layer. A careful position ...scan of the SiPM response has been performed with different prototypes, confirming the large number of firing cells and proving almost full efficiency, with the SiPM filling factor essentially negligible. This study also allowed us to study the time resolution of such devices as a function of the number of firing cells, reaching values below 20 ps. These measurements provide significant insight into the capabilities of SiPM sensors in direct detection of charged particles and their potential for several applications.
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 mum with a 50 mum 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.
In this paper, evidence that the increased response of SiPM sensors to the passage of charged particles is related mainly to Cherenkov light produced in the protection layer is reported. The response ...and timing properties of sensors with different protection layers have been studied.
Purpose
Our goal was to assess the computed tomo graphy (CT) imaging findings of thymoma and to correlate these features with Masaoka staging system and prognosis.
Materials and methods
CT findings ...of thymoma were analysed in 58 patients who had undergone surgery between January 2002 and September 2007. All cases were classified according to the Masaoka staging system. The presence of various CT findings was correlated with tumour invasiveness and recurrence. In statistical analysis, a
p
value <0.05 was interpreted as significant.
Results
The study found 26 noninvasive thymomas and 32 invasive thymomas. Invasive thymomas were more likely to be greater in size (
p
<0.01), with lobulated or irregular contours (
p
<0.02), a necrotic or cystic component (
p
<0.04), foci of calcification (
p
<0.05) and heterogeneous contrast enhancement (
p
<0.01) than were noninvasive thymomas. Disease progression developed in nine of 58 patients. Tumour recurrence and metastasis correlated with greater size (
p
<0.04), lobulated or irregular contours (
p
<0.01), complete mediastinal fat obliteration (
p
<0.01), great vessel invasion (
p
<0.01) and pleural implants (
p
<0.02).
Conclusions
CT is useful in differentiating invasive from noninvasive thymomas and plays an important role in evaluating and treating these patients for multimodal therapy with neoadjuvant approaches. Moreover, CT findings may serve as predictors of postoperative recurrence or metastasis.
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