Results obtained with 3D columnar pixel sensors bump-bonded to the RD53A prototype readout chip are reported. The interconnected modules have been tested in a hadron beam before and after irradiation to a fluence of about $1times$$10^{16}$neq cm$^{-2}$ (1MeV equivalent neutrons). All presented results are part of the CMS R&D activities in view of the pixel detector upgrade for the High Luminosity phase of the LHC at CERN (HL-LHC). A preliminary analysis of the collected data shows hit detection efficiencies around 97% measured after proton irradiation.
Silicon Photo-Multipliers (SiPM) are becoming the photo-detector of choice for increasingly more particle detection applications, from fundamental physics to medical and societal applications. One major consideration for their use at high-luminosity colliders is the radiation damage induced by hadrons, which leads to a dramatic increase of the dark count rate. KETEK SiPMs have been exposed to various fluences of reactor neutrons up to $Phi_{neq}$ = 5$times$10$^{14}$ cm$^{-2}$ (1 MeV equivalent neutrons). Results from the I-V, and C-V measurements for temperatures between $-$30$^circ$C and $+$30$^circ$C are presented. We propose a new method to quantify the effect of radiation damage on the SiPM performance. Using the measured dark current the single pixel occupation probability as a function of temperature and excess voltage is determined. From the pixel occupation probability the operating conditions for given requirements can be optimized. The method is qualitatively verified using current measurements with the SiPM illuminated by blue LED light.
The ATLAS experiment at the LHC will replace its current inner tracker system for the HL-LHC era. 3D silicon pixel sensors are being considered as radiation-hard candidates for the innermost layers of the new fully silicon-based tracking detector. 3D sensors with a small pixel size of $mathrm{50 times 50~mu m^{2}}$ and $mathrm{25 times 100~mu m^{2}}$ compatible with the first prototype ASIC for the HL-LHC, the RD53A chip, have been studied in beam tests after uniform irradiation to $mathrm{5 times 10^{15}~n_{eq}/cm^{2}}$. An operation voltage of only 50 V is needed to achieve a 97% hit efficiency after this fluence.
We report results from the testing of 35 {mu}m thick Ultra-Fast Silicon Detectors (UFSD produced by Hamamatsu Photonics (HPK), Japan and the comparison of these new results to data reported before on 50 {mu}m thick UFSD produced by HPK. The 35 {mu}m thick sensors were irradiated with neutrons to fluences of 0, 1*10^14, 1*10^15, 3*10^15, 6*10^15 neq/cm^2. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90Sr b{eta}-source. The leakage current, capacitance, internal gain and the timing resolution were measured as a function of bias voltage at -20C and -27C. The timing resolution was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction method for both. Within the fluence range measured, the advantage of the 35 {mu}m thick UFSD in timing accuracy, bias voltage and power can be established.
Small-pitch 3D silicon pixel detectors have been investigated as radiation-hard candidates for the innermost layers of the HL-LHC pixel detector upgrades. Prototype 3D sensors with pixel sizes of 50$times$50 and 25$times$100 $mu$m$^{2}$ connected to the existing ATLAS FE-I4 readout chip have been produced by CNM Barcelona. Irradiations up to particle fluences of $3times10^{16}$ n$_{mathrm{eq}}$/cm$^2$, beyond the full expected HL-LHC fluences at the end of lifetime, have been carried out at Karlsruhe and CERN. The performance of the 50$times$50 $mu$m$^{2}$ devices has been measured in the laboratory and beam tests at CERN SPS. A high charge collected and a high hit efficiency of 98% were found up to the highest fluence. The bias voltage to reach the target efficiency of 97% at perpendicular beam incidence was found to be about 100 V at $1.4times10^{16}$ n$_{mathrm{eq}}$/cm$^2$ and 150 V at $2.8times10^{16}$ n$_{mathrm{eq}}$/cm$^2$, significantly lower than for the previous IBL 3D generation with larger inter-electrode distance and than for planar sensors. The power dissipation at -25$^{circ}$C and $1.4times10^{16}$ n$_{mathrm{eq}}$/cm$^2$ was found to be 13 mW/cm$^2$. Hence, 3D pixel detectors demonstrated superior radiation hardness and were chosen as the baseline for the inner layer of the ATLAS HL-LHC pixel detector upgrade.
A new module concept for future ATLAS pixel detector upgrades is presented, where thin n-in-p silicon sensors are connected to the front-end chip exploiting the novel Solid Liquid Interdiffusion technique (SLID) and the signals are read out via Inter Chip Vias (ICV) etched through the front-end. This should serve as a proof of principle for future four-side buttable pixel assemblies for the ATLAS upgrades, without the cantilever presently needed in the chip for the wire bonding. The SLID interconnection, developed by the Fraunhofer EMFT, is a possible alternative to the standard bump-bonding. It is characterized by a very thin eutectic Cu-Sn alloy and allows for stacking of different layers of chips on top of the first one, without destroying the pre-existing bonds. This paves the way for vertical integration technologies. Results of the characterization of the first pixel modules interconnected through SLID as well as of one sample irradiated to $2cdot10^{15}$, eqcm{} are discussed. Additionally, the etching of ICV into the front-end wafers was started. ICVs will be used to route the signals vertically through the front-end chip, to newly created pads on the backside. In the EMFT approach the chip wafer is thinned to (50--60),$mu$m.
M. Meschini
,R. Ceccarelli
,M. Dinardo
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(2019)
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"First Results on 3D Pixel Sensors Interconnected to the RD53A Readout Chip after Irradiation to $1times$$10^{16}$neq cm$^{-2}$"
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Marco Meschini Dr.
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