Whilst the thermal management needs of future silicon detectors are increasing, the required mass and volume minimization of all detector ancillaries gets more demanding. This requires highly ...effective active cooling in very small channels. In the context of the AIDA-2020 project, a new test stand has been developed to characterize, with unprecedented level of accuracy, boiling flows of CO2 in mini- and micro-channels with hydraulic diameter ranging from 2 down to 0.1 mm. The heat transfer coefficient and pressure drop behaviour in stainless steel tubular evaporators for saturation temperatures from ＋20 to −25 °C, mass fluxes from 1200 to 100 kg m−2 s−1 and heat fluxes from 0.5 to 3.5 W/cm2 are discussed for one diameter. In addition, high speed camera observations of CO2 flow patterns recorded on micro-structured silicon cold plates are used to help with the interpretation of the heat transfer coefficient and pressure drop trends reported.
In the last years, high-resolution time tagging has emerged as a promising tool to tackle the problem of high-track density in the detectors of the next generation of experiments at particle ...colliders. Time resolutions below 50 ps and event average repetition rates of tens of MHz on sensor pixels having a pitch of 50 μm are typical minimum requirements. This poses an important scientific and technological challenge on the development of particle sensors and processing electronics. The TIMESPOT initiative (which stands for TIME and SPace real-time Operating Tracker) aims at the development of a full prototype detection system suitable for the particle trackers of the next-to-come particle physics experiments. This paper describes the results obtained on the first batch of TIMESPOT silicon sensors, based on a novel 3D MEMS (micro electro-mechanical systems) design. We demonstrate that following this approach, the performance of other ongoing silicon sensor developments can be matched and overcome. In addition, 3D technology has already been proved to be robust against radiation damage. A time resolution of the order of 20 ps has been measured at room temperature suggesting also possible improvements after further optimisations of the front-end electronics processing stage.
Abstract
We show the developments carried out to improve the silicon sensor technology for the detection of soft X-rays with hybrid X-ray detectors. An optimization of the entrance window technology ...is required to improve the quantum efficiency. The LGAD technology can be used to amplify the signal generated by the X-rays and to increase the signal-to-noise ratio, making single photon resolution in the soft X-ray energy range possible. In this paper, we report first results obtained from an LGAD sensor production with an optimized thin entrance window. Single photon detection of soft X-rays down to 452 eV has been demonstrated from measurements, with a signal-to-noise ratio better than 20.
Abstract
The challenging demands of the ATLAS High Luminosity (HL-LHC) Upgrade aim for a complete swap of new generation sensors that should cope with the ultimate radiation hardness. FBK has been ...one of the prime foundries to develop and fabricate such radiation-hard 3D silicon (Si) sensors. These sensors are chosen to be deployed into the innermost layer of the ATLAS Inner Tracker (ITk). Recently, a pre-production batch of 3D Si sensors of 50 × 50 μm
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pixel geometry, compatible with the full-size ITKPix (RD53B) readout chip, was fabricated. Two wafers holding temporary metal were diced at IZM, Germany, and a systematic QC test campaign was carried out at the University of Trento electronics laboratory. The paper briefly describes the 3D Si sensor design for ATLAS ITk and the required QC characterization setups. It comprises electrical tests (i.e., I-V, C-V, and I-T) of non-irradiated RD53B sensors. In addition, the study of several parametric analyses, i.e., oxide charge density, oxide thickness, inter-pixel resistance, inter-pixel capacitance, etc., are reported with the aid of Process Control Monitor (PCM) structures.
Abstract We present first results obtained with a prototype 4D-tracking demonstrator, using sensors and electronics developed within the TimeSPOT project, and tested on a positive charged pion beam ...at CERN SPS. The setup consists of five small tracking layers in a row, having area of about 3 mm 2 each, three of which equipped with 3D-trench silicon sensors and two with 3D-column diamond sensors. The five layers are then read-out by a KC705 Xilinx board on a PC. We describe the demonstrator structure and operation and illustrate preliminary results on its tracking capabilities.
Owing to their intrinsic (geometry dependent) radiation hardness, 3D pixel sensors are promising candidates for the innermost tracking layers of the forthcoming experiment upgrades at the "Phase 2" ...High-Luminosity LHC (HL-LHC) . To this purpose, extreme radiation hardness up to the expected maximum fluence of 2 x 10 super(16) n sub(eq).cm super(-2) must come along with several technological improvements in a new generation of 3D pixels, i.e., increased pixel granularity (50 x 50 or 25 x 100 mu m super(2) cell size), thinner active region (~ 100 mum), narrower columnar electrodes (~ 5 mum diameter) with reduced inter-electrode spacing (~ 30 mum), and very slim edges (~ 100 mum). The fabrication of the first batch of these new 3D sensors was recently completed at FBK on Si-Si direct wafer bonded 6" substrates. Initial electrical test results, performed at wafer level on sensors and test structures, highlighted very promising performance, in good agreement with TCAD simulations: low leakage current (< 1 pA/column), intrinsic breakdown voltage of more than 150 V, capacitance of about 50 fF/column, thus assessing the validity of the design approach. A large variety of pixel sensors compatible with both existing (e.g., ATLAS FEI4 and CMS PSI46) and future (e.g., RD53) read-out chips were fabricated, that were also electrically tested on wafer using a temporary metal layer patterned as strips shorting rows of pixels together. This allowed a statistically significant distribution of the relevant electrical quantities to be obtained, thus gaining insight into the impact of process-induced defects. A few 3D strip test structures were irradiated with X-rays, showing inter-strip resistance of at least several GOmega even after 50 Mrad(Si) dose, thus proving the p-spray robustness. We present the most important design and technological aspects, and results obtained from the initial investigations.
In view of the LHC upgrade for the High Luminosity phase (HL-LHC), the ATLAS experiment plans to replace the Inner Detector with an all-silicon system. The n-on-p silicon technology is a promising ...candidate to achieve a large area instrumented with pixel sensors, since it is radiation hard and cost effective. The paper reports on the performance of thin 100 and 130μm n-in-p planar pixel sensors produced by FBK-CMM with active-edge technology in collaboration with LPNHE and INFN. Beam-test results are presented, with focus on the hit efficiency at the detector edge of a novel design consisting of a staggered deep trench.
Abstract
Single-photon detection of X-rays in the energy range of 250 eV to 1 keV is difficult for hybrid detectors because of the low quantum efficiency and low signal-to-noise ratio. The low ...quantum efficiency is caused by the absorption of soft X-rays in the entrance window of the silicon sensors. The entrance window consists of an insensitive layer on the surface and a highly doped layer, which is typically from a few hundred nanometers to a couple of micrometers thick and is comparable to the absorption depth of soft X-ray photons (e.g. the attenuation length of 250 eV X-ray photons is ∼100 nm in silicon). The low signal-to-noise ratio is mainly caused by the small signal amplitude (e.g. ca. 70 electrons for 250 eV X-ray photons in silicon) with respect to the electronic noise. To improve the quantum efficiency, the entrance window must be optimized by minimizing the absorption of soft X-rays in the insensitive layer, and reducing charge recombination at the Si-SiO
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interface and in the highly doped region. Low gain avalanche diodes (LGADs) with a multiplication factor between 5 and 10 increase the signal amplitude and therefore improve the signal-to-noise ratio for soft X-rays, enabling single-photon detection down to 250 eV. Combining LGAD technology with an optimized entrance window technology can thus allow hybrid detectors to become a useful tool also for soft X-ray detection. In this work we present the optimization of the entrance window by studying the internal quantum efficiency of eight different process technology variations. The sensors are characterized using light emitting diodes with a wavelength of 405 nm. At this wavelength, the light has an absorption depth of 125 nm, equivalent to that of 276 eV X-rays. The best variation achieves an internal quantum efficiency of 0.992 for 405 nm UV light. Based on this study, further optimization of the quantum efficiency for soft X-rays detection is planned.
This paper reports on the development of a dedicated technology for the fabrication of pixelated edgeless sensors to be used in X-ray imaging applications at free electron laser (FEL) facilities. The ...process was developed with the goal of producing planar sensors suitable for the tight FEL application requirements in terms of collection speed, spatial resolution, and radiation tolerance. At the same time, care has been taken to reduce the dead area at the borders of the sensors, thus minimizing the loss of information and distortion introduced when tiling several dies in a large area imager. Different active-edge and slim-edge terminations, designed with the aid of TCAD simulations, are discussed. Based on numerical simulations, a wafer layout was designed and devices with different configurations were fabricated. The experimental results from the electrical characterization of the produced p-on-n sensors and test structures are presented and discussed.
The high luminosities expected at collider experiments over the coming years will put stringent requirements on the vertex detectors used in these experiments. The increased pile up will require ...improved spatial and timing resolution to distinguish between particle tracks while also requiring the devices to have an increased radiation hardness. 3D sensors have already been proven as a viable technology with good radiation hardness due to the short distance between electrodes and are also capable of achieving the desired spatial resolution. 3D sensors have so far not been fully exploited to achieve good timing resolution due to the non-uniformity of the electric field in the sensors. The TIMESPOT project aims to develop a complete integrated system for tracking with high precision in both space and time. Novel 3D sensors are being developed for this purpose, providing the normal advantages of this technology (such as radiation hardness and low depletion voltage), with the trench geometry also providing more uniform electric and weighting fields, optimized for timing. TCAD simulations have been carried out to optimize the design of these sensors and to estimate their performance, finding a compromise between the capacitance and the intrinsic speed. Technological tests have also been carried out at FBK to determine the manufacturing constraints of these sensors. A first layout including pixel sensors compatible with the TIMEPIX read-out chip and several test structures has been prepared and production of the first batch of sensors is underway.
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