Physical Sciences

Identifying Objects via Encased X-Ray- Fluorescent Materials — the Bar Code Inside

XRF spectra would be used as labels, similarly to bar codes, inside a product.

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The THz Hot-Electron Photon Counter Concept

Abstract¡ªWe discuss an implementation of a hot-electron transition-edge sensor   (TES) capable of counting THz photons. The main need for such a THz calorimeter   is spectroscopy on future space telescopes with a background limited NEP ~ 10-20   W/Hz1/2. The micromachined bolometers will unlikely reach such sensitivity at   temperatures above 10 mK. The hot-electron TES with sufficient sensitivity will   still have a time constant ~ 0.1-1.0 ms that is too short for integrating a   flux of THz background photons arriving at a rate of < 100 s-1. The Hot-Electron   Photon Counter based on a submicron-size superconducting Ti bridge with Nb Andreev   contacts will be able to detect individual photons above 170 GHz due to its   very low heat capacity. A discrimination of the low energy fluctuations with   a threshold device would allow for realization of an NEP ~ 10-20 W/Hz1/2 at   ¡Ý 1 THz while operating at 300 mK. With the sensor time constant of a few microseconds,   the dynamic range is ~ 30-40 dB. A compact array of the antenna-coupled counters   can be fabricated on a silicon wafer without membranes. Index Terms¡ªradiation   detectors, submillimeter wave detectors, bolometers, superconducting devices.   I. INTRODUCTION Several new advanced space submillimeter (SMM) astronomy missions   (Single-Aperture FIR Observatory ¨C SAFIR [1,2], Submillimeter Probe of the   Evolution of Cosmic Structure ¨C SPECS [3], Space Infrared Telescope for Cosmology   and Astrophysics ¨C SPICA [4]) have been recently proposed. They are expected   to make a dramatic impact on the attainable sensitivity in the moderate resolution   mode  where direct   detectors are typically used. This will be achieved by active cooling of telescope   mirrors to 4-5 K. For all existing platforms, the radiation of the atmosphere   and/or the temperature of the telescope set the sensitivity limit. Deep cooling   of a telescope mirror to ~4K would almost completely eliminate the effect of   the telescope emissivity. Then the limiting noise equivalent power (NEP) would   be set by the background fluctuation at the level of  in the most of the SMM range (see Fig. 1).

Posted in: Physical Sciences, Briefs, TSP

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Vacuum Attachment for XRF Scanner

A greater range of elements could be analyzed.

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Gas-Tolerant Device Senses Electrical Conductivity of Liquid

Bubbles are not trapped in this device.

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Chemical Sensors Based on Optical Ring

Resonance wavelengths are shifted by absorption of chemicals into polymer cladding layers. Chemical sensors based on optical ring resonators are undergoing development. A ring resonator according to this concept is a closed-circuit dielectric optical waveguide. The outermost layer of this waveguide, analogous to the optical cladding layer on an optical fiber, is a made of a polymer that (1) has an index of refraction lower than that of the waveguide core and (2) absorbs chemicals from the surrounding air. The index of refraction of the polymer changes with the concentration of absorbed chemical(s). The resonator is designed to operate with relatively strong evanescent-wave coupling between the outer polymer layer and the electromagnetic field propagating along the waveguide core. By virtue of this coupling, the chemically induced change in index of refraction of the polymer causes a measurable shift in the resonance peaks of the ring.

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Automatic Focus Adjustment of a Microscope

AUTOFOCUS is a computer program for use in a control system that automatically adjusts the position of an instrument arm that carries a microscope equipped with an electronic camera.

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A Broad-Band Phase-Contrast Wave-Front Sensor

The intrinsic 90° phase shift of an ideal beam splitter would be exploited. A broadband phase-contrast wave-front sensor has been proposed as a real-time wave-front sensor in an adaptive-optics system. The proposed sensor would offer an alternative to the Shack-Hartmann wave-front sensors now used in high order adaptive-optics systems of some astronomical telescopes. Broadband sensing gives higher sensitivity than does narrow- band sensing, and it appears that for a given bandwidth, the sensitivity of the proposed phase-contrast sensor could exceed that of a Shack-Hartmann sensor. Relative to a Shack-Hartmann sensor, the proposed sensor may be optically and mechanically simpler.

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