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At least 235 records · Page 13Linked to original sources

arXiv2013

Resonant scattering and diffraction beamline P09 at PETRA III

The resonant scattering and diffraction beamline P09 at PETRA III is designed for X-ray experiments requiring small beams, energy tunability, variable polarization and high photon flux. It is highly flexible in terms of beam size and offers full higher harmonic suppression. A state of the art double phase retarder setup provides variable linear or circular polarization. A high precision Psi-diffractometer and a heavy load diffractometer in horizontal Psi-geometry allow the accommodation of a wide variety of sample environments. A 14 T cryo-magnet is available for scattering experiments in magnetic fields.

physics.ins-det↗

arXiv2013

First Neutron Spectrometry Measurement at the HL-2A Tokamak

A compact neutron spectrometer based on the liquid scintillator is presented for neutron energy spectrum measurements at the HL-2A tokamak. The spectrometer was well characterized and a fast digital pulse shape discrimination software was developed using the charge comparison method. A digitizer data acquisition system with a maximum frequency of 1 MHz can work under an environment with a high count rate at HL-2A tokamak. Specific radiation and magnetic shielding for the spectrometer were designed for the neutron spectrum measurement at the HL-2A tokamak. For pulse height spectrum analysis, dedicated numerical simulation utilizing NUBEAM combined with GENESIS was performed to obtain the neutron energy spectrum. Subsequently, the transportation process from the plasma to the detector was evaluated with Monte Carlo calculations. The distorted neutron energy spectrum was folded with the response matrix of the liquid scintillation spectrometer, and good consistency was found between the simulated and measured pulse height spectra. This neutron spectrometer based on a digital acquisition system could be well adopted for the investigation of the auxiliary heating behavior and the fast-ion related phenomenon on different tokamak devices.

physics.ins-det↗

arXiv2013

Improvement studies on neutron-gamma separation in HPGe detectors by using neural networks

The neutrons emitted in heavy-ion fusion-evaporation (HIFE) reactions together with the gamma-rays cause unwanted backgrounds in gamma-ray spectra. Especially in the nuclear reactions, where relativistic ion beams (RIBs) are used, these neutrons are serious problem. They have to be rejected in order to obtain clearer gamma-ray peaks. In this study, the radiation energy and three criteria which were previously determined for separation between neutron and gamma-rays in the HPGe detectors have been used in artificial neural network (ANN) for improving of the decomposition power. According to the preliminary results obtained from ANN method, the ratio of neutron rejection has been improved by a factor of 1.27 and the ratio of the lost in gamma-rays has been decreased by a factor of 0.50.

physics.ins-det↗

arXiv2013

Silicon Detector Dark Matter Results from the Final Exposure of CDMS II

We report results of a search for Weakly Interacting Massive Particles (WIMPS) with the silicon detectors of the CDMS II experiment. This blind analysis of 140.2 kg-days of data taken between July 2007 and September 2008 revealed three WIMP-candidate events with a surface-event background estimate of 0.41^{+0.20}_{-0.08}(stat.)^{+0.28}_{-0.24}(syst.). Other known backgrounds from neutrons and 206Pb are limited to < 0.13 and <0.08 events at the 90% confidence level, respectively. The exposure of this analysis is equivalent to 23.4 kg-days for a recoil energy range of 7-100 keV for a WIMP of mass 10 GeV/c2. The probability that the known backgrounds would produce three or more events in the signal region is 5.4%. A profile likelihood ratio test of the three events that includes the measured recoil energies gives a 0.19% probability for the known-background-only hypothesis when tested against the alternative WIMP+background hypothesis. The highest likelihood occurs for a WIMP mass of 8.6 GeV/c2 and WIMP-nucleon cross section of 1.9e-41 cm2.

hep-ex↗

arXiv2014

Femtosecond Time-resolved MeV Electron Diffraction

We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 femto-Coulomb (~3x10^4 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirm that electron beam has a normalized emittance of ~50 nm-rad. The corresponding transverse and longitudinal coherence length are ~11 nm and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~ 100 fs (rms). The temporal resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Our results demonstrate the advantages of MeV electron diffraction: such as longer coherent lengths, large scattering cross-section and larger signal-to-noise ratio, and the feasibility of ultimately realizing 10 fs time-resolved electron diffraction.

physics.ins-det↗

arXiv2013

Superconducting flux-flow type ultra-low-noise magnetic sensors - An alternative to dc-SQUIDs

A superconducting magnetometers based on the magnetic field dependence of the Eck step voltage in long Josephson tunnel junctions (LJTJs) is demonstrated. The field to be measured is applied perpendicular to a continuous superconducting pickup loop. Wherever the loop has a narrow constriction, the density of the flux-restoring circulating currents will become relatively high and will locally create a magnetic field large enough to bring a biased LJTJ in the flux-flow state, i.e., at a finite voltage proportional to the field strength. This method allows the realization of a novel family of robust and general-purpose superconducting devices which, despite their simplicity, function as ultra-low-noise, wide-band and high-dynamics magnetometers. The performances of low-T$_c$ sensor prototypes, among which a highly linear voltage responsivity and a magnetic spectral density $S_B^{1/2}< 3\,fT/Hz^{1/2}$, promise to be competitive with those of the best superconducting quantum interference devices.

cond-mat.mes-hall↗

arXiv2013

Improvement of Main Drift Chamber Monte-Carlo tuning model at BESIII

Based on real data, a new parameterized model of the Main Drift Chamber response is proposed. In this model, we tune the ratio of good hits and the residual distribution separately. The difference between simulation and data in track reconstruction efficiency reduces from 1% to 0.5%, and the momentum resolution agreement improves significantly.

physics.ins-det↗

arXiv2013

SOX: Short distance neutrino Oscillations with BoreXino

The very low radioactive background of the Borexino detector, its large size, and the well proved capability to detect both low energy neutrino and anti-neutrino make an ideal case for the study of short distance neutrino oscillations with artificial sources at Gran Sasso. This paper describes the possible layouts of 51Cr neutrino and 144Ce-144Pr anti-neutrino source experiments in Borexino and shows the expected sensitivity for three possible different phases of the experiment.

physics.ins-det↗

arXiv2013

Latest results from XENON100 data

XENON100 is the current phase of the XENON dark matter program, which aims for the direct detection of WIMPs with liquid xenon time-projection chambers. We present the status of the experiment after 224.6 live days taken in 2011 and 2012 during which the detector successfully improved in terms of more calibration data, higher xenon purity, lower threshold and better background removal. The analysis has yielded no evidence for dark matter interactions. The status of the next generation XENON1T detector will be briefly described.

hep-ex↗

arXiv2013

The BABAR Detector: Upgrades, Operation and Performance

The BABAR detector operated successfully at the PEP-II asymmetric e+e- collider at the SLAC National Accelerator Laboratory from 1999 to 2008. This report covers upgrades, operation, and performance of the collider and the detector systems, as well as the trigger, online and offline computing, and aspects of event reconstruction since the beginning of data taking.

physics.ins-det↗

arXiv2013

Magnetic monopoles at the LHC and in the Cosmos

The magnetic monopole was postulated in 1931 by Dirac to explain electric charge quantisation. Searches for pair-produced monopoles are performed at accelerator facilities whenever a new energy regime is made available. In addition, monopoles with masses too high to be accessible at colliders would still have been produced in the early Universe and such relics can be searched for either in flight or trapped in matter. Here we discuss recent results and future prospects for direct monopole detection at the LHC and in bulk matter searches, with emphasis on the complementarity between the various techniques. Significant improvements of the results from the ATLAS experiment are expected with the development of new triggers. Dedicated LHC experiments will allow to probe wider ranges of monopole charges and masses: the MoEDAL experiment using both nuclear-track detectors and absorbing arrays, and searches for trapped monopoles in accelerator material. Finally, it is highlighted how the first search for monopoles trapped in polar volcanic rocks allows to set new constraints on the abundance of monopoles bound to matter in the Earth's interior and by extension in the primary material that formed the Solar System.

hep-ex↗

arXiv2013

Construction of a Gas Electron Multiplier (GEM) Detector for Medical Imaging

A prototype Gas Electron Multiplier (GEM) detector is under construction for medical imaging purposes. A single thick GEM of size 10x10 cm^2 is assembled inside a square shaped air-tight box which is made of Perspex glass. In order to ionize gas inside the drift field two types of voltage supplier circuits were fabricated, and array of 2x4 pads of each size 4x8 mm^2 were utilized for collecting avalanche charges. Preliminary testing results show that the circuit which produces high voltage and low current is better than that of low voltage and high current supplier circuit in terms of x-ray signal counting rates.

physics.ins-det↗

arXiv2013

Beam studies of novel THGEM-based potential sampling elements for Digital Hadron Calorimetry

Beam studies of thin single- and double-stage THGEM-based detectors are presented. Several 10 x 10 cm^2 configurations with a total thickness of 5-6 mm (excluding readout electronics), with 1 x 1 cm^2 pads inductively coupled through a resistive layer to APV-SRS readout electronics, were investigated with muons and pions. Detection efficiencies in the 98% range were recorded with an average pad-multiplicity of ~1.1. The resistive anode resulted in efficient discharge damping, with few-volt potential drops; discharge probabilities were ~10^{-7} for muons and 10^{-6} for pions in the double-stage configuration, at rates of a few kHz/cm^2. These results, together with the robustness of THGEM electrodes against spark damage and their suitability for economic production over large areas make THGEM-based detectors highly competitive compared to the other technologies considered for the SiD-DHCAL.

physics.ins-det↗

arXiv2013

Novel detector systems for the Positron Emission Tomography

In this contribution we describe a novel solution for the construction of Positron Emission Tomograph. We present the device allowing for determination of the impact position as well as time and deph of interaction of the annihilation gamma quanta. The device is comprised of scintillation chamber consisting of organic scintillators surrounding the body of the patient. We discuss two possible solutions: (i) the tomograph built out of scintillator strips, and (ii) the tomograph built out of the scintillator plates. The application of the fast scintillators will enable to take advantage of the difference between time of the registration of the annihilation quanta. The invented method will permit to use a thick layers of detector material with the possibility of measuring the depth of the gamma quantum interaction (DOI) and the determination of their time of flight (TOF), and will allow for increasing the size of the diagnostic chamber without a significant increase of costs. The method is a subject of two patent applications which are based on the techniques used in the particle physics experiments.

physics.med-ph↗

arXiv2013

TOF-PET detector concept based on organic scintillators

In this contribution we present a new concept of the large acceptance detector systems based on organic scintillators which may allow for simultaneous diagnostic of large fraction of the human body. Novelty of the concept lies in employing large blocks of polymer scintillators instead of crystals as detectors of annihilation quanta, and in using predominantly the timing of signals instead of their amplitudes.

physics.ins-det↗

arXiv2013

STRIP-PET: a novel detector concept for the TOF-PET scanner

We briefly present a design of a new PET scanner based on strips of polymer scintillators arranged in a barrel constituting a large acceptance detector. The solution proposed is based on the superior timing properties of the polymer scintillators. The position and time of the reaction of the gamma quanta in the detector material will be determined based on the time of arrival of light signals to the edges of the scintillator strips.

physics.ins-det↗

arXiv2013

Emerging Ideas in Nanocantilever based Biological Sensors

In this review article, we focus on emerging nanocantilever based biological sensors and discuss the response of nanocantilevers towards bio-molecules capture. The article guides the reader through various modes of operation (e.g., static or dynamic) to detect the change in characteristics (e.g., mass, stiffness, and/or surface stress) of cantilever due to adsorption of bio-molecules on cantilever surface. First, we explain the classical linear resonant mode mass sensors and static stress based sensors. The effect of operating the cantilever in nonlinear regime is then illustrated through examples of bifurcation based mass sensors and electromechanical coupling based Flexure-FET biosensors. We believe that a new class of nonlinear sensors, with their extraordinary sensitivity towards bio-molecules capture, could be the potential candidate for low cost point-of-care applications.

physics.ins-det↗

arXiv2014

Design of Wideband Microstrip Filters with Non-Equiripple Responses and Low Sensitivity

This paper presents a novel design procedure for wideband microstrip bandpass filters with non-equiripple filtering frequency responses and low sensitivity. Different from the traditional Chebyshev transfer function filters, the return loss zeros of the proposed non-equiripple filters can be redistributed within the operating passband. For the industrial applications, the proposed filters have a reduced sensitivity to manufacturing errors and exhibit good tolerance control for both specified bandwidth and maximum in-band reflection loss. By deriving the transfer functions, a synthesis approach with a set of non-linear equations can be established according to the specifications such as the bandwidth and predetermined reflection lobes. Without performing any post optimization in the full-wave simulation, the non-equiripple synthesized results have less sensitivity and fractional bandwidth (delta) error in comparison with those obtained from traditional Chebyshev transfer functions with equiripple frequency responses. As design examples, a four-pole bandpass filter with delta=60% and a five-pole bandpass filter with delta=82.5% are designed and fabricated. Measured results show a good agreement with those obtained from the prediction, without any tuning or adjustments.

physics.ins-det↗