Characterization of FBK 3D pixel sensor modules based on RD53A readout chip for the ATLAS ITk

CERN is planning to upgrade its Large Hadron Collider to the High Luminosity phase (HL-LHC), pushing detector technologies to cope with unprecedently demanding performance in terms of particle rate and radiation hardness. The ATLAS experiment decided to equip the innermost layer (L0) of its Inner Tracker (ITk) with small-pitch 3D pixels of two different geometries, i.e., 25 µm × 100 µm for the central barrel and 50 µm × 50 µm for the lateral rings. A new generation of 3D pixels featuring these small-pitch dimensions and reduced active thickness (∼150 µm) has been developed to this purpose within a collaboration of INFN and FBK since 2014. Recently, the R&D activities have been focused on the characterization of modules based on sensors compatible with the RD53A readout chip, which were tested in laboratory and at beam lines. In this paper, we report on the characterization of modules irradiated with protons up to a fluence of 1 × 1016 neq/cm2, including threshold tuning and noise measurements, and results from beam tests performed at DESY. Moreover, we will discuss about the electrical characteristics at wafer level and at module level before and after irradiation.

Diffusion of Cosmic Rays in MHD Turbulence with Magnetic Mirrors

As the fundamental physical process with many astrophysical implications, the diffusion of cosmic rays (CRs) is determined by their interaction with magnetohydrodynamic (MHD) turbulence. We consider the magnetic mirroring effect arising from MHD turbulence on the diffusion of CRs. Due to the intrinsic superdiffusion of turbulent magnetic fields, CRs with large pitch angles that undergo mirror reflection, i.e., bouncing CRs, are not trapped between magnetic mirrors, but move diffusively along the turbulent magnetic field, leading to a new type of parallel diffusion, i.e., mirror diffusion. This mirror diffusion is in general slower than the diffusion of nonbouncing CRs with small pitch angles that undergo gyroresonant scattering. The critical pitch angle at the balance between magnetic mirroring and pitch-angle scattering is important for determining the diffusion coefficients of both bouncing and nonbouncing CRs and their scalings with the CR energy. We find nonuniversal energy scalings of diffusion coefficients, depending on the properties of MHD turbulence.

A Computational Study on the Aeroacoustics of a Multi-Rotor Unmanned Aerial System

The noise generated by a quadrotor biplane unmanned aerial system (UAS) is studied computationally for various conditions in terms of the UAS pitch angle, propellers rotating velocity (RPM), and the UAS speed to understand the physics involved in its aeroacoustics and structure-borne noise. The k-ω SST turbulence model and Ffowcs Williams-Hawkings equations are used to solve the flow and acoustics fields, respectively. The sound pressure level is measured using a circular array of microphones positioned around the UAS, as well as at specific locations on its structure. The local flow is studied to detect the noise sources and evaluate the pressure fluctuation on the UAS surface. This study found that the UAS noise increases with pitch angle and the propellers’ rotating velocity, but it shows an irregular trend with the vehicle speed. The major source of the UAS noise is from its propellers and their interactions with each other at small pitch angle. The propeller and CRC-3 structure interaction contributes to the noise at large pitch angle. The results also showed that the propellers and structure of the UAS impose unsteadiness on each other through a two-way mechanism, resulting in structure-born noises which depend on the propeller RPM, velocity and pitch angle.

Added-mass force on elliptic airfoils

Herein, exact algebraic expressions for the non-circulatory (added-mass) forces on elliptic airfoils are derived for any two-dimensional motion – including simultaneous rectilinear acceleration and rotation – embedded in a steady free-stream flow. Despite the lengthy history of the added-mass concept and its widespread application to cylinders of various cross-sections, such closed-form expressions for elliptic cylinders, in terms of kinematic and geometric parameters alone, have remained absent from the literature until now. Inspection of the derived equations reveals that for pure pitching about a point on the chord-line, increasing thickness always decreases the added-mass force magnitude. For any given motion of the chord-line, the difference in force between thick and thin airfoils is proportional to the square of the thickness, although this difference may be positive or negative for the general three-degree-of-freedom case. In the special case of zero thickness and small pitch angles, Theodorsen's added-mass lift force on rigid thin airfoils is recovered; for large pitch angles, an exact generalization of Theodorsen's expression, applicable to the chord-normal direction, is given.

Pitch and Pattern Effects On Streamwise Fluidelastic Instability in Tube Arrays

Fluidelastic instability (FEI) is well known to be a critical flow-induced vibration concern for the integrity of the tubes in nuclear steam generators. Traditionally, this has been assumed to occur in the direction transverse to the direction of flow but the tube failures at San Onofre Nuclear Generating Station (SONGS) in Los Angeles proved that this assumption is not generally valid. A simple tube-in-channel theoretical model was previously developed to predict streamwise as well as transverse FEI in a parallel triangular tube array. This predicted that this array geometry was particularly sensitive to streamwise FEI for high mass-damping parameters and small pitch ratios, the conditions in which the SONGS failures occurred. The advantage of this simple modelling approach is that no new empirical data are required for parametric studies of the effects of tube pattern and pitch ratio on FEI. The tube-in-channel model has been extended to in-line square, normal triangular and rotated square tube arrays and the stability of these geometric patterns are analyzed for the effects of varying pitch ratio and the mass-damping parameter. The results are compared with the available experimental data and conclusions are drawn regarding the relative vulnerability of these different tube array geometries to streamwise FEI.

Parametric study of flapwise and edgewise vibration of horizontal axis wind turbine blades

In this paper, flapwise and edgewise vibrations of a horizontal axis wind turbine (HAWT) blade are studied. Rayleigh-Ritz method is used in which; orthogonal mode functions of the Euler-Bernoulli beam having fixed-free boundary are introduced into the Lagrange function and then the dynamic equations are derived. Effect of gravity, pitch angle, centrifugal stiffening, and rotary inertia are considered. Nondimensional equations are obtained by defining nondimensional parameters like; natural frequency, blade rotation, slenderness ratio, and simple pendulum frequency. The stiffness term of the natural frequency has two speed dependent elements and it is shown that, for small pitch angles, flapwise natural frequencies of the blade are increased by the increasing blade speed while the edgewise natural frequencies of the blade are decreased with the increasing blade speed. Pitch angle values ranging from 0° to 15° has negligible effect on the nondimensional natural frequencies of the blade up to the nondimensional blade speed of 4. Since the natural frequencies are the function of the blade speed, rotor critical speeds should be calculated with Campbell diagrams. Vibrational response of the blade tip to the gravity is dominant and much greater than that of the wind speed in the edgewise and flapwise vibration.

Rapid Assessment of Non-Verbal Auditory Perception in Normal-Hearing Participants and Cochlear Implant Users

In the case of hearing loss, cochlear implants (CI) allow for the restoration of hearing. Despite the advantages of CIs for speech perception, CI users still complain about their poor perception of their auditory environment. Aiming to assess non-verbal auditory perception in CI users, we developed five listening tests. These tests measure pitch change detection, pitch direction identification, pitch short-term memory, auditory stream segregation, and emotional prosody recognition, along with perceived intensity ratings. In order to test the potential benefit of visual cues for pitch processing, the three pitch tests included half of the trials with visual indications to perform the task. We tested 10 normal-hearing (NH) participants with material being presented as original and vocoded sounds, and 10 post-lingually deaf CI users. With the vocoded sounds, the NH participants had reduced scores for the detection of small pitch differences, and reduced emotion recognition and streaming abilities compared to the original sounds. Similarly, the CI users had deficits for small differences in the pitch change detection task and emotion recognition, as well as a decreased streaming capacity. Overall, this assessment allows for the rapid detection of specific patterns of non-verbal auditory perception deficits. The current findings also open new perspectives about how to enhance pitch perception capacities using visual cues.

Influence of pitch size and goalkeepers on external and internal load during small-sided games in amateur soccer players

Purpose To analyse the influence of goalkeepers during 4-a-side small-sided games, played in pitches of two different sizes (small: 30 × 20 m, large: 40 × 30 m). Methods Total distance covered (TD), distance covered at low- (LSD), moderate- (MSD), high- (HSD) and very high-speed (VHSD), average and maximal speed, Edwards’ training load (Edw-TL), time spent above 90% of maximal heart rate (T90%) and rate of perceived exertion (RPE) were monitored, in 18 amateur soccer players. Results Higher TD (mean difference: + 181 m, Hedge’s g: 0.93 and + 400 m, 3.37), MSD (+ 85 m, 0.79 and + 146 m, 1.64), HSD (+ 101 m, 1.41 and + 179 m, 3.26), VHSD (+ 30 m, 1.89 and + 35 m, 1.26), average speed (+ 0.65 km h−1, 0.88 and + 1.47 km h−1, 3.31) and maximal speed (+ 3.60 km h−1, 1.40 and + 3.58 km h−1, 1.40) were found in large than small pitch, without and with goalkeepers, respectively. Goalkeeper’s presence increased Edw-TL (+ 8.4 AU, 0.70) and reduced TD (− 141 m, 0.75), HSD (− 54 m, 0.75) and average speed (− 0.54 km h−1, 0.76) in small pitch and maximal speed (1.59 km h−1, 0.60 and 1.61 km h−1, 0.66) in both small and large pitches, respectively. RPE was higher (+ 20, 1.52) in the large than small pitch when the goalkeepers were present. Conclusion Implementing small-sided games, coaches should be aware that lower external load with similar internal load could be provided using small pitch with goalkeeper rather than either small goals or larger pitch. Furthermore, large small-sided games without goalkeeper may be the best choice for eliciting high training load.

Light Extraction Enhancement Techniques for Inorganic Scintillators

Scintillators play a key role in the detection chain of several applications which rely on the use of ionizing radiation, and it is often mandatory to extract and detect the generated scintillation light as efficiently as possible. Typical inorganic scintillators do however feature a high index of refraction, which impacts light extraction efficiency in a negative way. Furthermore, several applications such as preclinical Positron Emission Tomography (PET) rely on pixelated scintillators with small pitch. In this case, applying reflectors on the crystal pixel surface, as done conventionally, can have a dramatic impact of the packing fraction and thus the overall system sensitivity. This paper presents a study on light extraction techniques, as well as combinations thereof, for two of the most used inorganic scintillators (LYSO and BGO). Novel approaches, employing Distributed Bragg Reflectors (DBRs), metal coatings, and a modified Photonic Crystal (PhC) structure, are described in detail and compared with commonly used techniques. The nanostructure of the PhC is surrounded by a hybrid organic/inorganic silica sol-gel buffer layer which ensures robustness while maintaining its performance unchanged. We observed in particular a maximum light gain of about 41% on light extraction and 21% on energy resolution for BGO, a scintillator which has gained interest in the recent past due to its prompt Cherenkov component and lower cost.