Open-slope, translational submarine landslide in a tectonically active volcanic continental margin (Licosa submarine landslide, southern Tyrrhenian Sea)

The southern Tyrrhenian continental margin is the product of Pliocene-Recent back-arc extension. An area of approximately 30 km of gentle (about 1.5°) lower slope of the last glacial outer shelf sedimentary wedge in water depths of between 200 and 300 m failed between 14 and 11 ka BP. We approached the landslide by multibeam and sub-bottom profiler surveying, high-resolution multichannel seismics, and coring for stratigraphic and geotechnical purposes. With regard to a slope-stability analysis, we carried out an assessment of the stratigraphic and structural setting of the area of the Licosa landslide. This analysis revealed that the landslide detached along a marker bed that was composed of the tephra layer Y-5 (c. 39 ka). Several previously unknown geological characteristics of the area are likely to have affected the slope stability. These are the basal erosion of the slope in the Licosa Channel, a high sedimentation rate in the sedimentary wedge, earthquake shaking, the volcanic ash nature of the detachment surface, subsurface gas/fluid migration, and lateral porewater flow from the depocentre of wedge to the base of the slope along the high-permeability ash layers. A newly discovered prominent structural discontinuity is identified as the fault whose activity may have triggered the landslide

Advanced Theoretical Models for Charge Collection in CdTe Radiation Detectors: A comparison based on experimental data

CdTe detectors performances are limited by trapping of carriers in crystal defects and an accurate evaluation of charge transport properties in the detector is essential to characterize the semiconductor quality, the detector technology and to determine the expected resolution of the system. In this paper, we present a comparison among different theoretical models for charge collection applied to the same experimental data. These advanced models, unlike the classical Hecht law, take into account second order effects like nonuniform absorption of the photons, influence of the surfaces and of localized spatial charge. The validity of these models and their limits have been evaluated on the base of experimental data acquired with a Schottky CdTe pixelated detector irradiated with an ^241 Am X-gamma source. Mobility-lifetime products for electrons in the bulk have been derived and compared. Moreover, surface recombination velocity and shape of the internal electric field are considered, allowing to assess the quality of the crystal and of the technology

ALTAIR: A Low Noise, Low Power and Wide Dynamic Range ASIC for X and γ Ray Applications with CdTe/CdZnTe Pixel Detectors

We present ALTAIR, an Application Specific Integrated Circuit (ASIC) designed for the readout of CdTe/CdZnTe detectors for X-gamma ray spectroscopic imaging. ALTAIR is composed of 16 channels each with analog and mixed signal sections and it is developed for high energy resolution, high rate applications with the constraint of low power consumption. The ASIC has three selectable input charge signal ranges covering the photon energy from few keV up to 300 keV. The power consumption is about 1.2 mW/ch. A minimum Equivalent Noise Charge of 40 electrons r.m.s (425 eV FWHM in CdTe) has been measured at 500 ns peaking time. With a CdTe pixel detector connected to ALTAIR, a pulser FWHM of 1.7 keV (160 el. r.m.s.) has been achieved at +24°C, mainly determined by the detector leakage current noise and by the stray capacitance due to the connection

Propagation of frontally confined subaqueous landslides: Insights from combining geophysical, sedimentological, and geotechnical analysis

Subaquatic mass movements are common in marine and lacustrine environments, but due to their barely pre- dictable nature, direct observations of these processes are limited so that knowledge is only indirectly obtained by investigating the resulting mass-transport deposits (MTDs). Most research focuses on the most common fron- tally emergent slides, fast-moving events able to generate turbidity currents and tsunamis. Geohazards of fron- tally confined slides and mechanisms behind their typical fold-and-thrust deformation structures are however still poorly understood. We investigate frontally confined MTDs in Lake Lucerne (Switzerland) by integrating bathymetric and high-res- olution seismic data with geotechnical information derived from in situ Cone Penetrometer Tests and short core analysis. Investigated MTDs consist of three units: i) a mass-slide deposit, located at the base of the slope consisting of a coherent slope sequence, ii) a fold-and-thrust system developed in basin sediments, and iii) an overrunning mass flow deposit, consisting of remolded slope sediments. The deformed and thrusted basin sed- iments show higher undrained shear strength compared to the undisturbed basin sequence. We propose that this strengthening is caused by lateral compression leading to fluid expulsion in the high-plasticity basin sedi- ments by the bulldozing sliding mass. Relative kinematic indicators document that the fold-and-thrust deforma- tion structures occur rapidly. Thus, they should be considered in tsunami hazard analysis. Furthermore, our data highlight that the slope angle of the gliding surface and basin topography are key controlling factors for slope sta- bility and propagation of basin-plain deformations, respectively. Our integrated study supports and refines prop- agation models proposed in marine environments, revealing the potential of investigating smaller-scale easier- to-access MTDs in lakes

ALTAIR: A Low-Noise, Low-Power High Speed and Wide Dynamic Range ASIC for X and γ Ray Spectroscopy with CdTe/CdZnTe Pixel Detectors

ALTAIR is an Application Specific Integrated Circuit (ASIC) developed for the readout of CdTe/CdZnTe detectors for X-γ ray spectroscopic imaging. ALTAIR is composed of 16 channels with analog and mixed-signal sections specifically designed for high energy resolution and high-rate applications with the constraints of a low power consumption and operation at room temperature. The ASIC has three selectable ranges for input charge signals covering photon energies up to 90 keV, 160 keV or 300 keV, which allow to optimize the signal to noise ratio under different experimental conditions. Eight peaking times of the pulse shaper are selectable from 200 ns up to 2.3 μs. ALTAIR includes a 180 bits register and an integrated SPI interface to configure the signal processing parameters globally or independently for each channel. The power consumption is 950 μW/channel or 1.35 mW/channel for single ended or differential output versions, respectively. A minimum Equivalent Noise Charge (ENC) of 37 electrons rms (386 eV FWHM in CdTe) has been measured at 500 ns peaking time and 90 keV energy range. With a CdTe pixel detector connected to ALTAIR and operated at +24°C, a pulser FWHM of 1.7 keV (160 el. rms) and 1.9 keV FWHM on 59.54 keV line of 241Am have been achieved at a peaking time of 500 ns

Performance at Cryogenic Temperatures of an Ultra Low Noise CMOS Front-end for Fano-limited X-ray Spectroscopy

We qualified the noise performance of Sirio CMOS Charge Sensitive Preamplifier as a function of temperature down to -92 °C. The goal is twofold: i) quantify the improvement of the ENC and ii) disentangle the temperature dependence of the individual noise contributions and identify critical design issues. The intrinsic noise of the preamplifier, without connection to any detector, has been measured by injecting charge pulses through a test capacitance. The main noise contributions (series white, series flicker, parallel white) have been extracted from the experimental data. The lowest measured ENC at the optimal peaking time is around 1 el. rms

A CdTe pixel detector–CMOS preamplifier for room temperature high sensitivity and energy resolution X and γ ray spectroscopic imaging

X and γ ray imaging devices with spectroscopic capabilities are strongly demanded in industrial, medical and scientific applications. CdTe detectors with Schottky contacts are very interesting due to their high absorption coefficient and the low leakage current of the reverse-biased rectifying junction even at room temperature. A CdTe detector with a pixel size of 0.75 mm × 0.75 mm has been coupled to SIRIO, a research-grade charge sensitive preamplifier with 1.2 electrons r.m.s. intrinsic noise. The system has been characterized at +20 °C for X and γ ray spectroscopy with a 241Am source. An intrinsic energy resolution of 326 eV FWHM has been measured and spectral line widths from 337 eV FWHM at 2.7 keV to 843 eV FWHM at 59.54 keV have been recorded. The linearity error of the spectrometer has been measured to be within ±0.1% in the 2.7 keV–59 keV energy range. Effects of escaping photons and fluorescences have been resolved and identified. The line widening sources and their effect on Fano factor determination have been discussed

Bias polarization characterization of Al/CdTe/Pt Schottky X-ray detector for industrial applications

Al/CdTe/Pt Schottky diodes are commonly used as X-ray and γ-ray detectors thanks to their high absorption coefficients and room temperature working conditions. One known drawback is the bias induced polarization, which downgrades the spectroscopic performances by progressively decreasing the charge collection efficiency. In the frame of charge accumulation model (CAM), the bias induced polarization is explained with Cd vacancies that create a deep acceptor level inside the gap: when a reverse voltage is applied, this level is thermally populated deforming the electric field inside the detector. We measured the reverse current transient at different temperatures and interpreted the experimental results with the CAM. In particular, we investigated the Schottky barrier height, its relation to the electric field at the anode, the ratio between deep trap concentration and de-trapping time and the energy of the deep acceptor level. We estimate an energy of 0.59eV above the valence band edge for the acceptor level. We propose a variation to the CAM that takes into account two deep acceptor levels, instead of only one, this allows to improve the fittings of the time dependence of the electric field at the anode