The TIMESPOT project aims at the construction of a mini-tracker demonstrator implementing both high space and time resolutions at the single pixel level. The pixels have a pitch of 55 × 55 μm2. ...Specified time resolution is equal or better than 50 ps. Developed sensors are based both on 3D silicon and diamond technologies, whose layout and fabrication process have been suitably optimized for best time resolution. Read-out pixel electronics is being developed in 28-nm CMOS technology. The first batch of 3D silicon sensors, containing several test structures based on different geometries of the electrodes, has been delivered in June 2019 and has been tested against its timing performance both under laser and minimum ionizing particle beams. In the present paper, the output of these starting measurements is presented. The sensors show very good timing performance, having σ¡30 ps (sigma), although operated with non-optimized front-end electronics and in noisy environment. These results represent an important step forward in the development of pixels with timing operating at extremely high interaction rates and fluences, as required in the next generation of upgraded colliders.
•A crucial challenge about future vertex detectors consists in realizing pixel with timing capabilities.•In this respect, we need sensors and electronics having at the same time the following requirements: space resolutions of O(10 μm), time resolutions below 50 ps, radiation resistance ¿ 1016 1 MeV neutron equivalent per cm2.•We have developed and fabricated dedicated fast silicon sensors in 3D technology with a pitch of 55 μm.•They have been proved to have time resolutions below 30 ps.
3D sensors have already been proven as a viable and inherently radiation hard technology. While encouraging timing results have been obtained from small-pitch 3D test structure, new approaches are ...also being investigated to meet the challenges of the coming years.
One such approach, pursued in the framework of the INFN TIMESPOT project, is the development of 3D sensors with trenched electrodes. The trench geometry will provide more uniform electric and weighting fields than in current devices, allowing for good timing resolution, while also maintaining or improving upon the usual advantages of a 3D geometry.
We report the fabrication of the first batch of devices, consisting of TIMEPIX compatible pixel sensors, as well as a number of test devices that have been used to study the performance of different pixel geometries. Results highlighted good intrinsic properties, with leakage current of the order of 10 pA per pixel and opposite electrode pixel capacitance of approximately 70–75 fF per pixel, in good agreement with previous simulations of these devices.
A detector from single crystal synthetic diamond with conducting wires has been prepared with an improved femto-second laser process. The detector was characterised with a 4.5MeV proton micro-beam ...(Ruđer Bos̆ković Institute, Zagreb). The charge collection efficiency and the transient current response have been investigated with high spatial resolution. A hexagonal and square cell geometry is investigated. Both cell geometries show full charge collection at 40V bias voltage, and little charge sharing between neighbouring cells. The experimental data is compared to a simulation and qualitative agreement is observed.
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•3D diamond detector with hexagonal and cubic cells fabricated•Performance of hexagonal and cubic cells comparable•Differences in charge sharing observed, important for application scenario
To form a 3D diamond detector electrodes were produced in diamond by a femtosecond laser-induced phase transition of diamond to graphite. The process parameters were varied to study the influence on ...electrode resistivity and induced stress. A technique for a relative measurement of stress induced in 3D diamond detectors is described. The detector was characterised with a 15keV photon micro-beam (Diamond Light Source, Oxford) and a 4MeV proton micro-beam (Ruđer Bošković Institute, Zagreb). The detector shows characteristics consistent with full charge collection. Spatially resolved transient current measurements were obtained with protons for the first time, and the results were compared to simulations of the detector.
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•The effect of laser parameters on graphitic electrodes is characterised.•A comparative study using a photon and proton micro-beam is made for the first time.•Time Resolved Ion Beam Induced Current data is compared to simulation.
Simulation of 3D diamond detectors Forcolin, G.T.; Oh, A.; Murphy, S.A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2017, Letnik:
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3D diamond detectors present an interesting prospect for future Particle Physics experiments. They have been studied in detail at beam tests with 120GeV protons and 4MeV protons. To understand the ...observations that have been made, simulations have been carried out using Synopsys TCAD in order to explain the movement of charge carriers within the sample, as well as the effects of charge sharing. Reasonable agreement has been observed between simulation and experiment.
•TCAD successfully used to simulate the behavior of 3D Diamond devices.•Simulation used to understand negative signal observed in 120GeV proton Testbeam.•Observe position dependence of signal due to non uniformity field as expected.
Chemical Vapour Deposition (CVD) diamond is being considered as a material for particle detectors in a harsh radiation environment. This article presents beam test results of 3D pixel detectors ...fabricated with poly-crystalline CVD diamonds. The cells of the devices had a size of 50µm×50µm with columns 2.6µm in diameter. The cells were ganged in a 3×2 and 5×1 pattern to match the layouts of the pixel read-out electronics currently used in the CMS and ATLAS experiments at the Large Hadron Collider, respectively. In beam tests, using tracks reconstructed with a high precision tracking telescope, a tracking efficiency of 99.3% was achieved. The efficiency of both devices plateaus at a bias voltage of 30V. Also irradiated poly-crystalline CVD diamond pad detectors were investigated. In high rate beam tests with particle fluxes up to 20MHz/cm2 and irradiations up to 8 ⋅ 1015n/cm2 it was shown that the pulse height of irradiated poly-crystalline CVD diamonds does not depend on flux to the O2%.
Objective: Driver fatigue is considered to be a major contributor to road traffic crashes. Cardiac monitoring and heart rate variability (HRV) analysis is a candidate method for early and accurate ...detection of driver sleepiness. This study has 2 objectives: to evaluate the (1) suitability of different preprocessing strategies for detecting and removing outlier heartbeats and spectral transformation of HRV signals and their impact of driver sleepiness assessment and (2) relation between common HRV indices and subjective sleepiness reported by a large number of drivers in real driving situations, for the first time.
Methods: The study analyzed >3,500 5-min driving epochs from 76 drivers on a public motorway in Sweden. The electrocardiograph (ECG) data were recorded in 3 studies designed to evaluate the physiological differences between awake and sleepy drivers. The drivers reported their perceived level of sleepiness according to the Karolinska Sleepiness Scale (KSS) every 5 min. Two standard methods were used for identifying outlier heartbeats: (1) percentage change (PC), where outliers were defined as interbeat intervals deviating >30% from the mean of the four previous intervals and (2) standard deviation (SD), where outliers were defined as interbeat interval deviating >4 SD from the mean interval duration in the current epoch. Three standard methods were used for spectral transformation, which is needed for deriving HRV indices in the frequency domain: (1) Fourier transform; (2) autoregressive model; and (3) Lomb-Scargle periodogram. Different preprocessing strategies were compared regarding their impact on derivation of common HRV indices and their relation to KSS data distribution, using box plots and statistical tests such as analysis of variance (ANOVA) and Student's t test.
Results: The ability of HRV indices to discriminate between alert and sleepy drivers does not differ significantly depending on which outlier detection and spectral transformation methods are used. As expected, with increasing sleepiness, the heart rate decreased, whereas heart rate variability overall increased. Furthermore, HRV parameters representing the parasympathetic branch of the autonomous nervous system increased. An unexpected finding was that parameters representing the sympathetic branch of the autonomous nervous system also increased with increasing KSS level. We hypothesize that this increment was due to stress induced by trying to avoid an incident, because the drivers were in real driving situations.
Conclusions: The association of HRV indices to KSS did not depend on the preprocessing strategy. No preprocessing method showed superiority for HRV association to driver sleepiness. This was also true for combinations of methods for frequency domain HRV indices. The results prove clear relationships between HRV indices and perceived sleepiness. Thus, HRV analysis shows promise for driver sleepiness detection.
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