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
Journal Article
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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.
A large number of particle detectors employ liquid argon as their target material owing to its high scintillation yield and its ability to drift ionization charge over large distances. Scintillation ...light from argon is peaked at 128 nm and a wavelength shifter is required for its efficient detection. In this work, we directly compare the light yield achieved in two identical liquid argon chambers, one of which is equipped with polyethylene naphthalate (PEN) and the other with tetraphenyl butadiene (TPB) wavelength shifter. Both chambers are lined with enhanced specular reflectors and instrumented with SiPMs with a coverage fraction of approximately 1%, which represents a geometry comparable to the future large scale detectors. We measured the light yield of the PEN chamber to be 39.4
±
0.4(stat)
±
1.9(syst)% of the yield of the TPB chamber. Using a Monte Carlo simulation this result is used to extract the wavelength shifting efficiency of PEN relative to TPB equal to 47.2
±
5.7%. This result paves the way for the use of easily available PEN foils as a wavelength shifter, which can substantially simplify the construction of future liquid argon detectors.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
First FBK production of 50 μm ultra-fast silicon detectors Sola, V.; Arcidiacono, R.; Boscardin, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2019, Letnik:
924
Journal Article
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Fondazione Bruno Kessler (FBK, Trento, Italy) has recently delivered its first 50 μm thick production of Ultra-Fast Silicon Detectors (UFSD), based on the Low-Gain Avalanche Diode design. These ...sensors use high resistivity Si-on-Si substrates, and have a variety of gain layer doping profiles and designs based on Boron, Gallium, Carbonated Boron and Carbonated Gallium to obtain a controlled multiplication mechanism. Such variety of gain layers will allow identifying the most radiation hard technology to be employed in the production of UFSD, to extend their radiation resistance beyond the current limit of ϕ∼ 1015 neq/cm2. In this paper, we present the characterisation, the timing performance, and the results on radiation damage tolerance of this new FBK production.
Time of flight (TOF) in positron emission tomography (PET) has experienced a revival of interest after its first introduction in the eighties. This is due to a significant progress in solid state ...photodetectors (SiPMs) and newly developed scintillators (LSO and its derivatives). Latest developments at Fondazione Bruno Kessler (FBK) lead to the NUV-HD SiPM with a very high photon detection efficiency of around 55%. Despite the large area of 4x4 mm super(2) it achieves a good single photon time resolution (SPTR) of 180+ or -5ps FWHM. Coincidence time resolution (CTR) measurements using LSO:Ce codoped with Ca scintillators yield best values of 73+ or -2ps FWHM for 2x2x3 mm super(3) and 117+ or -3ps for 2x2x20 mm super(3) crystal sizes. Increasing the crystal cross-section from 2x2 mm super(2) to 3x3 mm super(2) a non negligible CTR deterioration of approximately 7ps FWHM is observed. Measurements with LSO:Ce codoped Ca and LYSO:Ce scintillators with various cross-sections (1x1 mm super(2)- 4x4 mm super(2)) and lengths (3mm - 30mm) will be a basis for discussing on how the crystal geometry affects timing in TOF-PET. Special attention is given to SiPM parameters, e.g. SPTR and optical crosstalk, and their measured dependency on the crystal cross-section. Additionally, CTR measurements with LuAG:Ce, LuAG:Pr and GGAG:Ce samples are presented and the results are interpreted in terms of their scintillation properties, e.g. rise time, decay time, light yield and emission spectra.
Continuous positive airway pressure (CPAP) is an important therapeutic tool in COVID-19 acute respiratory distress syndrome (ARDS) since it improves oxygenation, reduces respiratory rate and can ...prevent intubation and intensive care unit (ICU) admission. CPAP during pronation has seldom been described and never during sedation.
Case series.
High dependency unit of San Carlo University Hospital (Potenza, Italy).
Eleven consecutive patients with COVID-19 ARDS.
Helmet CPAP in prone position after failing a CPAP trial in the supine position.
Data collection at baseline and then after 24, 48 and 72h of pronation. We measured PaO
/FIO
, pH, lactate, PaCO
, SpO
, respiratory rate and the status of the patients at 28-day follow up.
Patients were treated with helmet CPAP for a mean±SD of 7±2.7 days. Prone positioning was feasible in all patients, but in 7 of them dexmedetomidine improved comfort. PaO
/FIO
improved from 107.5±20.8 before starting pronation to 244.4±106.2 after 72h (p<.001). We also observed a significantly increase in Sp0
from 90.6±2.3 to 96±3.1 (p<.001) and a decrease in respiratory rate from 27.6±4.3 to 20.1±4.7 (p=.004). No difference was observed in PaCO
or pH. At 28 days two patients died after ICU admission, one was discharged in the main ward after ICU admission and eight were discharged home after being successfully managed outside the ICU.
Helmet CPAP during pronation was feasible and safe in COVID-19 ARDS managed outside the ICU and sedation with dexmedetomidine safely improved comfort. We recorded an increase in PaO
/FIO
, SpO
and a reduction in respiratory rate.
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