The charge collection properties of Cadmium–Telluride (CdTe) and Cadmium–Zinc–Telluride (CZT) in comparison with Silicon (Si) are presented using the transient-current technique (TCT) where the ...current pulses are generated by
α
-particles emitted from an
241Am source. From the recorded current pulse shapes, the charge collection efficiency, the charge carrier mobility and the electric field distribution inside the detectors are extracted. In particular, the signals of the compound semiconductors CdTe and CZT are interpreted with respect to the build-up of space–charges in the sensor volume and the subsequent deformation of the electric field. As high-quality CdTe and CZT samples are now commercially available, the knowledge of these material characteristics is of outmost importance for the application of CdTe and CZT in X-ray imaging.
In addition, the paper describes the influence of Ohmic and Schottky contacts on the current pulses in CdTe as well as the effects of polarization, i.e. the time-dependent degradation of the detector signals due to the accumulation of fixed charges within the sensor.
For the detection of secondary vertices of long lived particles containing bottom and charm quarks at the International Linear Collider (ILC), a DEPFET pixel detector is one of the technologically ...favored options. In a DEPFET sensor a MOSFET pixel detector is integrated on a sidewards depleted silicon bulk sensor, thus combining the advantages of a fully depleted silicon sensor with in-pixel amplification. DEPFET pixel matrices have been characterized in a high energy particle beam. Since the DEPFET is a very high precision device, given its large S/N (> 100) and small pixel size (36 × 22 ¿m 2 ), a DEPFET based pixel telescope consisting of 5 DEPFETs has been developed. The uncertainty on the predicted position for a device under test (DUT) positioned inside the telescope was found to be 1.4 ¿m with the existing device, due to the limited performance of two of the five DEPFET planes. A DEPFET telescope built of 5 modules equivalent to the best plane presented here, would have a track extrapolation error as low as 0.65 ¿m at the DUT plane.
The development of digital semiconductor based X-ray detectors necessitates a detailed understanding of the applied sensor material. Under this premise a broad-band transient current technique (TCT) ...setup has been developed and used to characterize different semiconductors. The measurements are based on the generation of electrical charges within the sensor material and the subsequent time-resolved analysis of the charge carrier movement. From the recorded current pulses the charge collection efficiency, the charge carrier mobility and the electric field profile have been extracted. The examined materials are silicon p in n diodes, ohmic and Schottky contacted CdTe detectors, CdZnTe (CZT) crystals with Schottky contacts as well as two single-crystal CVD-diamonds.
DEPFET, a monolithic active pixel sensor for the ILC Velthuis, J.J.; Kohrs, R.; Mathes, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2007, Letnik:
579, Številka:
2
Journal Article
Recenzirano
In a DEPleted Field Effect Transistor (DEPFET) sensor a MOSFET is integrated on a sidewards depleted p-on-n silicon detector, thereby combining the advantages of a fully depleted silicon sensor with ...in-pixel amplification. A 450
μm thick DEPFET was tested in a testbeam. The
S/
N was found to be larger than 110. The position resolution is better than 5
μm. At a seed cut of 7
σ, the efficiency and purity are both close to 100%. In the readout chip a zero-suppression capability is implemented. The functionality was demonstrated using a radio-active source. The predicted impact parameter resolution of a 50
μm thick DEPFET vertex detector, is much better than required for the International Linear Collider (ILC).
ECONF C0604032:0231,2006 We have developed a prototype system for the ILC vertex detector based on
DEPFET pixels. The system operates a 128x64 matrix (with ~35x25 square micron
large pixels) and uses ...two dedicated microchips, the SWITCHER II chip for
matrix steering and the CURO II chip for readout. The system development has
been driven by the final ILC requirements which above all demand a detector
thinned to 50 micron and a row wise read out with line rates of 20MHz and more.
The targeted noise performance for the DEPFET technology is in the range of
ENC=100 e-. The functionality of the system has been demonstrated using
different radioactive sources in an energy range from 6 to 40keV. In recent
test beam experiments using 6GeV electrons, a signal-to-noise ratio of S/N~120
has been achieved with present sensors being 450 micron thick. For improved
DEPFET systems using 50 micron thin sensors in future, a signal-to-noise of 40
is expected.
AbstractNappe oscillation and its potentially undesirable impact associated with significant noise production can be an issue for free-overfall hydraulic structures. Although nappe oscillation has ...been observed on various prototype free-overfall structures, this instability behavior may not be evident during the design process in which experimental and/or numerical modeling may be utilized. In addition, previous studies regarding nappe oscillation scalability using similitude or other relationships has received very limited attention in the literature. An experimental study aimed at investigating the possible size scale effects on nappe oscillations was undertaken utilizing two experimental facilities: a prototype-scale linear weir (3-m fall height) and a geometrically similar 1:3-scale model (1-m fall height). The nappe oscillation occurrence assessment and oscillation frequency evaluation were performed using sound and image analyses. Experiments on both models showed that the nappe oscillation phenomenon generally occurs over a fixed range of unit discharge and is independent of size scale. Nappe oscillation can therefore not be reproduced at different model scales according to standard similarity laws. This study also highlights the secondary influences of the crest profile and the fall height on the oscillation characteristics.
AbstractNappe oscillation is a phenomenon that can have an undesirable impact to the local environment (e.g., nearby residences, and parks) as the phenomenon has been observed to produce a ...significant level of noise caused by acoustic pressure waves. As a result, a detailed investigation was undertaken to identify practical and effective mitigation solutions to address these effects for free-overfall structures. Nappe oscillations were studied using a prototype-scale linear weir (weir length of 3.5 m and fall height of 3 m), a high-speed camera, and audio equipment. The effectiveness of various crest modifications to reduce nappe oscillation and any corresponding impacts to hydraulic efficiency were evaluated. The test matrix included the optimization (position and spacing of elements) of three mitigation solutions: 12 configurations with projecting elements, 5 configurations with deflectors, and 1 configuration with a step. These three countermeasures proved to be effective after the optimization of their characteristics. In particular, deflectors or a step produced the maximum noise reduction while decreasing the discharge coefficient by less than 3% over the range of experimental conditions.
We have developed a prototype system for the ILC vertex detector based on DEPFET pixels. The system operates a 128x64 matrix (with ~35x25 square micron large pixels) and uses two dedicated ...microchips, the SWITCHER II chip for matrix steering and the CURO II chip for readout. The system development has been driven by the final ILC requirements which above all demand a detector thinned to 50 micron and a row wise read out with line rates of 20MHz and more. The targeted noise performance for the DEPFET technology is in the range of ENC=100 e-. The functionality of the system has been demonstrated using different radioactive sources in an energy range from 6 to 40keV. In recent test beam experiments using 6GeV electrons, a signal-to-noise ratio of S/N~120 has been achieved with present sensors being 450 micron thick. For improved DEPFET systems using 50 micron thin sensors in future, a signal-to-noise of 40 is expected.
Scale effects in physical piano key weirs models Erpicum, Sebastien; Tullis, Blake P.; Lodomez, Maurine ...
Journal of hydraulic research,
11/2016, Letnik:
54, Številka:
6
Journal Article, Web Resource
Recenzirano
Odprti dostop
With inertia and gravity representing the dominant forces for most open channel flow applications (e.g. weir flow), Froude similitude is commonly used for scaling hydraulic performance data from the ...model to prototype structures. With weir flow, as the upstream head decreases, however, the relevance of surface tension and viscosity forces can increase to the point when the model and prototype similitude is not fully achieved through Froude scaling. Such discrepancies are referred as size-scale effects, and among other things, can result in variations in the head-discharge relationship, nappe trajectory, and air entrainment. Published criteria for avoiding significant size-scale effects for free flow over linear weirs have suggested that minimal heads of ∼0.02 to 0.07 m be respected, independently of the model size. In this study, the size-scale effect, minimum upstream head, and Weber number limits are investigated for four piano key weirs with geometric model scales of 1:1, 1:7, 1:15, and 1:25.
One of the main challenges for building high resolution PET scanners with sub-millimeter resolution is to compensate for the parallax error induced by the height of the detector elements. During the ...last years several approaches to extract depth of interaction information for pixilated scintillation detectors were evaluated. We investigate the feasibility of a two layer PET detector with single sided readout using digital SiPM (dSiPM) arrays whereby the depth information is encoded in the width of the light distribution.
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