Search results for " sensor"

Simulation of propagation characteristics of ultrasonic guided waves in fractured long bone

2008

Using ultrasonic guided waves (GW) to assess fractures in long bones has gained considerable attention. This paper focuses on using an improved hybrid boundary element method (HBEM) to analyze and calculate reflection coefficients (RC) and transmission coefficients (TC) of low-order GWs for cracks with different depth-to-width ratios (d/w) in fractured long bones. The results showed that the primary received modes, which include the transmitted and reflected modes, are the same as the incident modes. For some values of d/w, the TC of different GW always had local maxima at adjacent frequencies. For some other cracks with different d/w, most of the TC curves had local maxima of which frequen…

Reconfigurable Shack-Hartmann sensor without moving elements.

2010

We demonstrate wavefront sensing with variable measurement sensitivity and dynamic range by means of a programmable microlens array implemented onto an off-the-shelf twisted nematic liquid crystal display operating as a phase-only spatial light modulator. Electronic control of the optical power of a liquid lens inserted at the aperture stop of a telecentric relay system allows sensing reconfigurability without moving components. Results of laboratory experiments show the ability of the setup to detect both smooth and highly aberrated wavefronts with adequate sensitivity.

An optical pulse modulator based on an all-fiber mirror

1996

Self-referenced phase reconstruction proposal of Ghz bandwidth non-periodical optical pulses by in-fiber semi-differintegration

2011

Abstract We propose two new techniques able to retrieve the phase profile of a given temporal optical pulse based on the use of in-fiber semi-differintegral operators, where by semi-differintegration we mean either a 0.5th-order differentiation or integration. In both cases, the signal's temporal phase can be obtained by simple dividing two temporal intensity profiles, namely the intensities of the input and output pulses of a spectrally shifted semi-differintegral operator. In both cases, we obtained simple analytical expressions for the phase profile. The techniques are self-referenced and well-suited for real-time applications. We numerically prove the viability of these proposals.

Operation of transition-edge sensors with excess thermal noise

2006

The superconducting transition-edge sensor (TES) is currently one of the most attractive choices for ultra-high resolution calorimetry in the keV x-ray band, and is being considered for future ESA and NASA missions. We have performed a study on the noise characteristics of Au/Ti bilayer TESs, at operating temperatures around ~100 mK, with the SQUID readout at 1.5 K. Experimental results indicate that without modifications the back-action noise from the SQUID chip degrades the noise characteristics significantly. We present a simple and effective solution to the problem: by installing an extra shunt resistor which absorbs the excess radiation from the SQUID input, we have reduced the excess …

DEPFET Macropixel Detectors for MIXS: First Electrical Qualification Measurements

2010

The Mercury Imaging X-ray Spectrometer (MIXS) is one of the instruments on board the Mercury Planetary Orbiter of the fifth European Space Agency (ESA) cornerstone mission BepiColombo. This spectrometer comprises two instruments and allows imaging X-ray spectroscopy of the Mercurian surface. The focal plane arrays for the energy and spatial resolved detection of X-rays are based on depleted P-channel FET (DEPFET) macropixel detectors. We report on the first electrical qualification measurements of DEPFET macropixel flight hardware, which are done at room temperature. The measurement of the transistor properties of all DEPFET pixels allows the selection of 100% electrically defect-free devic…

A $B_4C$-silicon target for the detection of neutrino interactions

1998

This note describes the construction of a target for neutrino interactions composed of passive boron carbide plates interleaved with silicon microstrip detectors. The target contains four layers of passive material with a total mass of 45 kg and 600 single--sided silicon microstrip detectors with a total surface of 1.14 m$^2$ distributed over five layers. It is installed in the NOMAD spectrometer at the CERN SPS neutrino beam. During the 1997 run about 8000 \nm\ charged current interactions were estimated to have occurred in the target. For these events it will be possible to perform a precise measurement of both vertex and kinematical variables. This will provide invaluable experience towa…

Development of a Temperature Distributed Monitoring System Based On Raman Scattering in Harsh Environment

2014

Raman Distributed Temperature Sensors (RDTSs) offer exceptional advantages to monitor the envisioned French deep geological repository for nuclear wastes, called Cigeo. Both $\gamma $ -ray and hydrogen release from nuclear wastes can strongly affect the temperature measurements made with RDTS. We present experimental studies on how the performances of RDTS evolve in harsh environments like those associated with $\gamma $ -rays or combined radiations and ${{\rm H}_2}$ release. The response of two standard and one radiation tolerant multimode fibers (MMFs) are investigated. In all fibers the differential induced attenuation between Stokes and anti-Stokes signal, ${({{\alpha _{\rm AS}} - {\alp…

Optimizing the operating temperature of a transition edge sensor

2006

We discuss the theory for optimizing the operating temperature of a voltage biased superconducting transition edge sensor (TES) in terms of energy resolution and speed, considering only internal detector noise sources. The noise processes included in the modeling are the unavoidable Johnson and phonon noise. The phonon noise is calculated for the case of ballistic transport. If other external and excess internal noise sources are not dominant, an optimal operating temperature can be found to minimize the energy resolution. The detector slows down by approximately a factor of two at the optimal energy resolution point.

Silicon detector for a Compton camera in nuclear medical imaging

2002

Electronically collimated gamma ca\-me\-ras based on Com\-pton scattering in silicon pad sensors may improve imaging in nuclear medicine and bio-medical research. The work described here concentrates on the silicon pad detector developed for a prototype Compton camera. The silicon pad sensors are read out using low noise VLSI CMOS chips and novel fast triggering chips. Depending on the application a light weight and dense packaging of sensors and its readout electronics on a hybrid is required. We describe the silicon pad sensor and their readout with the newly designed hybrid. %The silicon detector of a Compton camera %may contain up to $10^5$~analogue channels requiring %a fast and low co…