Data acquisition system for dark matter detectors

Progress in Ge detector technology has resulted in ultralow backgrounds of less than 0.3 counts keV^–1 kg^–1 d^–1 at energies between 5 and 12 keV, and less than 1.0 counts kev^–1 kg^–1 d^–1 for energies between 3 and 5 keV. Coupled with good energy resolution, 0.4 keV FWHM at 10 keV, this allows searches for DM particles with m 8 GeV/c².Electromagnetic interference and acoustical pick-up are the main sources of background in the best Ge detectors. These problems are even more important in cryogenic WIMP detectors under development. A PC-based on line pulse shape analysis system is presented which permits rejection of about 95% percent of the EMI/ acoustical background. The hardware uses a low cost, commercially available digital storage oscilloscope. The software consists of about 20,000 lines of code in Pascal and assembly language. We tested this system using a low radioactive background Ge-system on the Earth's surface. For low energy events (27 keV photons) this system permits improvement in the background from 0.1 cpm to 2 cpd.     

Enhancing design-for-test for active analog filters by using CLP(ℜ)

We describe a computer-aided approach to automatic fault isolation in active analog filters which enhances the design-for-test (DFT) methodology proposed by Soma (1990). His primary concern was in increased controllability and observability while the fault isolation procedure was sketched only in general terms. We operationalize and extend the DFT methodology by using CLP() to model analog circuits and by a model-based diagnosis approach to implement a diagnostic algorithm. CLP() is a logic programming language which combines symbolic and numeric computation. The diagnostic algorithm uses different DFT test modes and results of voltage measurements for different frequencies and computes a set of suspected components. Ranking of suspected components is based on a measure of (normalized) standard deviations from predicted mean values of component parameters. The diagnosis is performed incrementally, in each step reducing the set of potential candidates for the detected fault. Case studies show encouraging results in isolation of soft faults of a given low-pass biquad filter.     

Optimization of Boundary Scan Tests Using FPGA-Based Efficient Scan Architectures

This paper presents a method for optimization of board-level scan test with the help of reconfigurable scan-chains (RSCs) implemented in a programmable logic of FPGA. Despite that the RSC concept is a well-known solution for scan-based test time reduction, the usage of RSC may lead to un-acceptable hardware overhead. In our work, we are targeting a completely new approach of exploiting on-board FPGA resources that being unconfigured are typically available during the manufacturing test phase for carrying out tests using temporarily implemented virtual RSC structures. As the allocated FPGA logic is re-claimed for functional use after the test is finished, the presented method delivers all the advantages of RSCs at no extra hardware cost. Experimental results show that the proposed virtual RSCs can fit into all available commercial FPGAs providing a significant test time reduction in comparison with state-of-the-art Boundary Scan test tecnique.     

Light-induced ultrafast proton-coupled electron transfer responsible for H2 evolution on silver plasmonics

Light-driven proton-coupled electron transfer (PCET) reactions on nanoplasmonics would bring temporal control of their reactive pathways, in particular, prolong their charge separation state. Using a silver nano-hybrid plasmonic structure, we observed that optical excitation of Ag-localized surface plasmon instigated electron injection into TiO₂ conduction band and oxidation of isopropanol alcoholic functionality. Femtosecond transient infrared absorption studies show that electron transfer from Ag to TiO₂ occurs in ca. 650?fs, while IPA molecules near the Ag surface undergo an ultrafast bidirectional PCET step within 400?fs. Our work demonstrates that ultrafast PCET reaction plays a determinant role in prolonging charge separation state, providing an innovative strategy for visible-light photocatalysis with plasmonic nanostructures.     

Evluation of Strength of Plane Microcracked Structural Elements Via Electrical Resistance Scanning

The paper focuses on experimental verification of a new approach to evaluate strength of structural elements via electrical resistance scanning. The approach utilizes explicit cross-property connections. In the case of multiple parallel cracks, we reconstruct certain characteristics of the microstructure from resistance measurements and evaluate the corresponding strength reduction. The results are compared to actual fracture tests of preconfigured specimens. Experimental strength measurements show strong correlation to the results predicted by the resistance scanning technique.     

Ignition of hydrogen–air mixtures using pulsed nanosecond dielectric barrier plasma discharges in plane-to-plane geometry

Ignition of preheated (400–500 K) H₂–air mixtures at low pressures (80–100 torr) excited by pulsed nanosecond dielectric barrier discharges is investigated through experiments and simulations. Time resolved absolute OH concentration and temperature data are obtained using Laser Induced Fluorescence (LIF) technique. Ignition is achieved in the decaying plasma after a burst of discharge pulses (repetition rate 10–40 kHz), with the time delay inferred from sudden rise in OH^* emission. One-dimensional simulations are performed to obtain information about the plasma generated radicals and heat release across the discharge gap. A plasma fluid formulation is used with ions and neutral species at gas temperature, and electrons in non-equilibrium. An accurate reduced chemistry mechanism is developed through sensitivity analysis to expedite the plasma simulations. The model predictions show excellent agreement with experimental measurements, validating the numerical framework and chemistry data. The input pulse energy and ignition characteristics are found to be highly sensitive to uncertainties in dielectric properties. Ignition delay exhibits a threshold-like dependence on input plasma energy, and increases steeply as the number of pulses in the burst is reduced. The nanosecond plasma assisted ignition is achieved through a two-step process. Firstly, the burst of discharge pulses produce a large pool of radicals and provide an average temperature rise of ∼1–2 K/pulse. In the next step, if the temperature exceeds a threshold value of ∼700 K, significant heat release from partial fuel oxidation is triggered. The process becomes self-sustaining and the temperature continues to rise even after the plasma source is switched off, accelerating the conventional H₂–O₂ chain branching pathways and leading to ignition. We provide conclusive evidence of large volume ignition with nanosecond plasma as opposed to thermal ignition at a hot-spot. Ignition is first observed at the center of the discharge gap, but the kernel expands rapidly to the entire volume, except near walls where heat losses keep the temperature low. It is demonstrated that the ignition occurs independently at different locations due to local plasma chemistry effects and heat transport does not play a significant role.     

Geometry,mechanical properties and mounting of perforated plates for ballistic application

In this paper, the ballistic resistance of perforated plates made of different types of steel, mounting and geometry was investigated. Different types of steel in various heat treatment conditions were tested. Target mounting was also varied: rigid, oblique and hanging. Furthermore, four different perforated plate geometries were tested: two plate thicknesses and two hole diameters. Their behaviour was tested using impact from firing 12.7 mm M-8 API ammunition at eleven perforated plate samples. These samples were placed by means of a steel frame over a 13 mm RHA plate, at two distances. Damaged area on targets was correlated to ballistic resistance of the whole armour to find the optimal perforated plate. It was found that perforated plates, in optimized case offer a frequent fracture of the penetrating core in up to five parts. This debris is unable to penetrate the basic plate, offering mass effectiveness of the whole armour model of 1.76 and the mass effectiveness of the perforated plate of 5.91.