6,753 research outputs found
Re-testing the JET-X Flight Module No. 2 at the PANTER facility
The Joint European X-ray Telescope (JET-X) was the core instrument of the
Russian Spectrum-X-gamma space observatory. It consisted of two identical soft
X-ray (0.3 - 10 keV) telescopes with focusing optical modules having a measured
angular resolution of nearly 15 arcsec. Soon after the payload completion, the
mission was cancelled and the two optical flight modules (FM) were brought to
the Brera Astronomical Observatory where they had been manufactured. After 16
years of storage, we have utilized the JET-X FM2 to test at the PANTER X-ray
facility a prototype of a novel X-ray polarimetric telescope, using a Gas Pixel
Detector (GPD) with polarimetric capabilities in the focal plane of the FM2.
The GPD was developed by a collaboration between INFN-Pisa and INAF-IAPS. In
the first phase of the test campaign, we have re-tested the FM2 at PANTER to
have an up-to-date characterization in terms of angular resolution and
effective area, while in the second part of the test the GPD has been placed in
the focal plane of the FM2. In this paper we report the results of the tests of
the sole FM2, using an unpolarized X-ray source, comparing the results with the
calibration done in 1996.Comment: Author's accepted manuscript posted to arXiv.org as permitted by
Springer's Self-Archiving Policy. The final publication is available at
http://rd.springer.com/article/10.1007%2Fs10686-013-9365-
High precision dynamic multi-interface profilometry with optical coherence tomography
Optical coherence tomography (OCT) has mostly been used for high speed volume imaging but its profilometry potentials have not been fully exploited. This paper demonstrates high precision (as good as ~50nm) multi-interface profilometry using a Fourier domain OCT system without special anti-vibration devices. The precision is up to two orders of magnitudes better than the depth resolution of the OCT. Detailed analysis of the precision achieved for different surfaces is presented. The multi-interface profiles are obtained as a by-product of the tomography data. OCT has advantage in speed and sensitivity at detecting rough and internal interfaces compared to conventional optical profilometry. An application of the technique to the dynamic monitoring of varnish drying on paint-like substrates is demonstrated, which provides a better understanding of the formation of surface roughness. The technique has potential benefits in the field of art conservation, coatings technology and soft matter physics
Optical power meter using radiation pressure measurement
This paper describes a radiation pressure meter based on a diamagnetic
spring. We take advantage of the diamagnetic property of pyrolytic carbon to
make an elementary levitated system. It is equivalent to a torsional
spring-mass-damper system consisting of a small pyrolytic carbon disc levitated
above a permanent magnet array. There are several possible measurement modes.
In this paper, only the angular response to an optical power single-step is
described. An optical detection composed of a laser diode, a mirror and a
position sensitive detector (PSD) allow measurement of the angular deflection
proportional to the voltage delivered by the PSD. Once the parameters of the
levitated system depending on its geometrical and physical characteristics have
been determined regardless of any optical power, by applying a simple physical
law, one can deduce the value of the optical power to be measured from the
measurement of the first maximum of the output voltage amplitude
Reversible compression of an optical piston through Kramers dynamics
We study the reversible crossover between stable and bistable phases of an
over-damped Brownian bead inside an optical piston. The interaction potentials
are solved developing a method based on Kramers' theory that exploits the
statistical properties of the stochastic motion of the bead. We evaluate
precisely the energy balance of the crossover. We show that the deformation of
the optical potentials induced by the compression of the piston is related to a
production of heat which measures the non-adiabatic character of the crossover.
This reveals how specific thermodynamic processes can be designed and
controlled with a high level of precision by tailoring the optical landscapes
of the piston.Comment: 9 pages, 9 figure
Turbidimeter based on a refractometer using a charge-coupled device
International audienceSalinity and turbidity are two important seawater properties in oceanography. We have studied the use of a high resolution refractometer to measure the salinity of seawater. The requirement of a multifunctional sensor makes the turbidity measurement based on our refractometer valuable. We measure turbidity according to the attenuation of the laser beam caused by the scattering. With the configuration of our refractometer, several issues impact the laserbeamattenuation measurement, while the measurement of salinity is impacted by the scattering as well. All these issues make light distribution nonsensitive sensors such as position sensitive devices unsuitable for building the refracto-turbidimeters. To overcome these issues, a charge-coupled device combined with a new location algorithm is used to measure both the refractive index and the attenuation. Several simulations and experiments are carried out to evaluate this new method. According to the results, the way to improve the resolution is discussed as well. The validation of our method is proved by comparison to the nephelometer specified by the nephelometric turbidity unit standar
Substrate curvature measurement system
Industry often requires, in a variety of processes, the measurement of deformation induced in a solid object by mechanical stress. One such process is during the manufacture of very large scale integrated circuits (VLSI). During this process a substrate is coated with a thin film to protect the micro circuitry formed on the substrate. Due to the differences in thermal expansions between film and substrate, mechanical stresses can develop which may lead to deformation of the substrate surface. Any deformation of the substrate surface will result in mechanical stress in the interconnections of the circuitry, which could result in severe damage to the operation of the circuit. Different measurement techniques are available to measure the spherical deformation of substrates, with the latest known technique being a combination of a laser beam deflection and light scattering techniques. Many of the existing techniques reveal shortcomings, one of which is a 2-dimensional scanning capability with a minimum of moving components. Another shortcoming is the incapability of previous techniques to calculate the relative error which the measuring technique induces into the results. The aim of this study has been to develop an electro-optical system embodying the successful principles of these techniques in a system which will eliminate the shortcomings and produce results in excess of those previously recorded. In this work, we have concentrated on discussing the development of a system which will produce in situ real time monitoring of mechanical stresses in a solid. The system includes the minimization of system induced errors through the calculation of error voltage gains, and the introduction of a 2-dimensional scanning capability to determine the true position of the laser beam without prior knowledge of the initial substrate curvature. A four-quadrant position sensitive detector (PSD) with relevant Lab View software and programs were also introduced into the system
Efficient Microparticle Trapping with Plasmonic Annular Apertures Arrays
In this work, we demonstrate trapping of microparticles using a plasmonic
tweezers based on arrays of annular apertures. The transmission spectra and the
E- field distribution are simulated to calibrate the arrays. Theoretically, we
observe sharp peaks in the transmission spectra for dipole resonance modes and
these are redshifted as the size of the annular aperture is reduced. We also
expect an absorption peak at approximately 1,115 um for the localised plasmon
resonance. Using a laser frequency between the two resonances, multiple
plasmonic hotspots are created and used to trap and transport micron and
submicron particles. Experimentally, we demonstrate trapping of individual 0.5
um and 1 um polystyrene particles and particle transportation over the surface
of the annular apertures using less than 1.5 mW/um2 incident laser intensity at
980 nm
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