Characterization of FBK small-pitch 3D diodes after neutron irradiation up to 3.5x10**16 neq cm**-2

We report on the characterization by a position resolved laser system of small-pitch 3D diodes irradiated with neutrons up to an extremely high fluence of 3.5x10**16 neq cm**-2. We show that very high values of signal efficiency are obtained, in good agreement with the geometrical expectation based on the small values of the inter-electrode spacings, and also boosted by charge multiplication effects at high voltage. These results confirm the very high radiation tolerance of small-pitch 3D sensors well beyond the maximum fluences expected at the High Luminosity LHC.Comment: 10 pages, 7 figures, submitted to Proceedings of IWORID 2018 on JINS

Development of New 3D Pixel Sensors for Phase 2 Upgrades at LHC

We report on the development of new 3D pixel sensors for the Phase 2 Upgrades at the High-Luminosity LHC (HL-LHC). To cope with the requirements of increased pixel granularity (e.g., 50x50 or 25x100 um2 pixel size) and extreme radiation hardness (up to a fluence of 2e16 neq cm-2), thinner 3D sensors (~100 um) with electrodes having narrower size (~ 5 um) and reduced spacing (~ 30 um) are considered. The paper covers TCAD simulations, as well as technological and design aspects relevant to the first batch of these 3D sensors, that is currently being fabricated at FBK on 6-inch wafers.Comment: 4 pages, 8 figures, 2015 IEEE Nuclear Science Symposium and Medical Imaging Conferenc

A COMPACT ULTRA-WIDE BAND PRINTED LOG-PERIODIC ANTENNA USING A BOW-TIE STRUCTURE

In this letter, an ultra-wideband compact printed log periodic dipole (LPD) array antenna is designed to operate between 500MHz and 6 GHz frequencies. The proposed LPD antenna structure consists of one bow-tie dipole and 15 regular dipole elements. The bow-tie element is introduced to improve the antenna's performance at the lowest frequencies below 1 GHz and at the same time to reduce the antenna size maintaining a good performance. An experimental antenna prototype has been designed, optimized, fabricated, numerically and experimentally assessed. The obtained results are very promising, and they demonstrated that the presented antenna prototype is able to operate in the range between 500MHz and 6 GHz with an average gain of 6 dBi and a very compact size

First Production of New Thin 3D Sensors for HL-LHC at FBK

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 2e16 neq.cm-2 must come along with several technological improvements in a new generation of 3D pixels, i.e., increased pixel granularity (50x50 or 25x100 um2 cell size), thinner active region (~100 um), narrower columnar electrodes (~5 um diameter) with reduced inter-electrode spacing (~30 um), and very slim edges (~100 um). The fabrication of the first batch of these new 3D sensors was recently completed at FBK on Si-Si direct wafer bonded 6-inch 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 GOhm 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.Comment: 8 pages, 7 figures, 2016 IWORI

Parametric Resonance in Electrostatically Actuated Micromirrors

We consider an electrostatically actuated torsional micromirror, a key element of recent optical microdevices. The mechanical response is analyzed with specific emphasis on its nonlinear features. We show that the mirror motion is an example of parametric resonance, activated when the drive frequency is twice the natural frequency of the system. The numerical model, solved with a continuation approach, is validated with very good accuracy through an extensive experimental campaign

Combined Bulk and Surface Radiation Damage Effects at Very High Fluences in Silicon Detectors: Measurements and TCAD Simulations

In this work we propose a new combined TCAD radiation damage modelling scheme, featuring both bulk and surface radiation damage effects, for the analysis of silicon detectors aimed at the High Luminosity LHC. In particular, a surface damage model has been developed by introducing the relevant parameters (NOX, NIT) extracted from experimental measurements carried out on p-type substrate test structures after gamma irradiations at doses in the range 10-500 Mrad(Si). An extended bulk model, by considering impact ionization and deep-level cross-sections variation, was included as well. The model has been validated through the comparison of the simulation findings with experimental measurements carried out at very high fluences (2 10^16 1 MeV equivalent n/cm^2) thus fostering the application of this TCAD approach for the design and optimization of the new generation of silicon detectors to be used in future HEP experiments.Comment: 8 pages, 14 figures. arXiv admin note: text overlap with arXiv:1611.1013

Intrinsic time resolution of 3D-trench silicon pixels for charged particle detection

In the last years, high-resolution time tagging has emerged as the tool to tackle the problem of high-track density in the detectors of the next generation of experiments at particle colliders. Time resolutions below 50ps and event average repetition rates of tens of MHz on sensor pixels having a pitch of 50$\mu$m 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. Following this approach, the performance of other ongoing silicon sensor developments has been matched and overcome, while using a technology which is known to be robust against radiation degradation. A time resolution of the order of 20ps has been measured at room temperature suggesting also possible improvements after further optimisations of the front-end electronics processing stage.Comment: This version was accepted to be published on JINST on 21/07/202

Predictors of Response to Hydroxyurea and Switch to Ruxolitinib in HU-Resistant Polycythaemia VERA Patients: A Real-World PV-NET Study

In polycythemia vera (PV), the prognostic relevance of an ELN-defined complete response (CR) to hydroxyurea (HU), the predictors of response, and patients' triggers for switching to ruxolitinib are uncertain. In a real-world analysis, we evaluated the predictors of response, their impact on the clinical outcomes of CR to HU, and the correlations between partial or no response (PR/NR) and a patient switching to ruxolitinib. Among 563 PV patients receiving HU for ≥12 months, 166 (29.5%) achieved CR, 264 achieved PR, and 133 achieved NR. In a multivariate analysis, the absence of splenomegaly (p = 0.03), pruritus (p = 0.002), and a median HU dose of ≥1 g/day (p &lt; 0.001) remained associated with CR. Adverse events were more frequent with a median HU dose of ≥1 g/day. Overall, 283 PR/NR patients (71.3%) continued HU, and 114 switched to ruxolitinib. In the 449 patients receiving only HU, rates of thrombosis, hemorrhages, progression, and overall survival were comparable among the CR, PR, and NR groups. Many PV patients received underdosed HU, leading to lower CR and toxicity rates. In addition, many patients continued HU despite a PR/NR; however, splenomegaly and other symptoms were the main drivers of an early switch. Better HU management, standardization of the criteria for and timing of responses to HU, and adequate intervention in poor responders should be advised

Novel 3D Pixel Sensors for the Upgrade of the ATLAS Inner Tracker

The ATLAS experiment will undergo a full replacement of its inner detector to face the challenges posed by the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The new Inner Tracker (ITk) will have to deal with extreme particle fluences. Due to its superior radiation hardness the 3D silicon sensor technology has been chosen to instrument the innermost pixel layer of ITk, which is the most exposed to radiation damage. Three foundries (CNM, FBK, and SINTEF), have developed and fabricated novel 3D pixel sensors to meet the specifications of the new ITk pixel detector. These are produced in a single-side technology on either Silicon On Insulator (SOI) or Silicon on Silicon (Si-on-Si) bonded wafers by etching both n- and p-type columns from the same side. With respect to previous generations of 3D sensors they feature thinner active substrates and smaller pixel cells of 50 × 50 and 25 × 100 µm2. This paper reviews the main design and technological issues of these novel 3D sensors, and presents their characterization before and after exposure to large radiation doses close to the one expected for the innermost layer of ITk. The performance of pixel modules, where the sensors are interconnected to the recently developed RD53A chip prototype for HL-LHC, has been investigated in the laboratory and at beam tests. The results of these measurements demonstrate the excellent radiation hardness of this new generation of 3D pixel sensors that enabled the project to proceed with the pre-production for the ITk tracker.publishedVersio

Development of 3D Silicon radiation detectors for neutrons and high energy charged particles

In the past few years, several interesting developments in microstructured solid-state thermal neutron detectors have been pursued. These devices feature high aspect-ratio cavities, filled with neutron converter materials, so as to improve the neutron detection efficiency with respect to coated planar sensors. In the framework of the INFN HYDE (HYbrid Detectors for neutrons) project, we have designed new microstructured sensors aimed at thermal and fast neutron detection. Owing to the different cross section, neutron imaging is complementary to X-ray imaging allowing for a high contrast in soft materials. To this purpose, the possibility to have pixelated neutron detectors compatible with existing read-out chips (e.g., those from the Medipix/Timepix family) is an important goal that was achieved in this thesis. In this thesis the entire workflow will be described in detail, covering the design, simulations, fabrication and characterization of 3D neutron detectors for imaging produced at FBK. As a related topic, new 3D sensors for the "Phase-2" upgrades at High Luminosity LHC have been developed, and some aspects relevant to the device simulation and characterization are also reported in this thesis