1,721,081 research outputs found
Virgo calibration and reconstruction of the gravitationnal wave strain during VSR1
No full textVirgo is a kilometer-length interferometer for gravitationnal waves detection located near Pisa. Its first science run, VSR1, occured from May to October 2007. The aims of the calibration are to measure the detector sensitivity and to reconstruct the time series of the gravitationnal wave strain h(t). The absolute length calibration is based on an original non-linear reconstruction of the differential arm length variations in free swinging Michelson configurations. It uses the laser wavelength as length standard. This method is used to calibrate the frequency dependent response of the Virgo mirror actuators and derive the detector in-loop response and sensitivity within ∼ 5%. The principle of the strain reconstruction is highlighted and the h(t) systematic errors are estimated. A photon calibrator is used to check the sign of h(t). The reconstructed h(t) during VSR1 is valid from 10 Hz up to 10 kHz with systematic errors estimated to 6% in amplitude. The phase error is estimated to be 70 mrad below 1.9 kHz and 6 μs above
X-ray emission from plasma produced by a Nd:YAG/glass laser on a Cu target: A preliminary analysis
No full textIn this article, we present a preliminary study of the soft X-ray emission by a Cu plasma, obtained by focalizing a Nd:YAG/glass laser beam on a copper target at λ =532nm (second harmonic) at a laser intensity I ≈ 10 12W/cm 2. The pulse duration is tL=6ns and the laser shot energy E L ranges from 200 to 300mJ. We have measured the average X-ray spectral emission and determined the X-ray conversion efficiency, (% 2 π sr) in the aluminum transmission window at 70eV with a harder X-ray tail at about 700eV. A study of angular distribution of X-ray intensity emitted from the plasma is presented too
Noise from scattered light in Virgo's second science run data
No full textVirgo is one of the large, ground-based interferometers aimed at detecting gravitational waves. One of the technical problems limiting its sensitivity is caused by light in the output beams which is backscattered by seismically excited surfaces and couples back into the main beam of the interferometer. The resulting noise was thoroughly studied, measured and mitigated before Virgo's second science run (VSR2). The residual noise during VSR2, which increases in periods with a large microseism activity, is accurately predicted by the theoretical model. The scattered light has been associated with transient events in the gravitational-wave signal of the interferometer
Study of plasma evolution in argon-filled capillary Z-pinch devoted to x-ray production
No full textThe high-current (up to 40 kA) fast electrical discharge Z-pinch in an argon-filled capillary has been developed to produce pulses of intense soft x-ray radiation in the spectral region of 2-50 nm. We present results of an experimental analysis of plasma evolution in the Z-pinch and discuss them in comparison with a theoretical model. The effects of the electrical circuit parameters and the initial discharge conditions on the plasma evolution are studied. The current was produced by a water dielectric capacitor (C = 3 or 10 nF) resonantly charged to the selected voltages (up to 450 kV) by a six-stage Marx generator. The current pulse with amplitude ranging from 20 to 40 kA and a half-cycle duration of 90 or 170 ns was generated through a 14.5 cm long, 5 mm diameter Al2O3 ceramic channel. The capillary was filled by argon to a selected pressure in the region 0.1-1 Torr. The experimental results are in good agreement with the predictions of the so-called 'simple model of Z-pinch'
Capillary discharge experiment for collisional excitation soft X-ray laser
No full textThe realization of a capillary discharge soft X-ray source, for soft x ray laser generation by high temperature (> 100 eV) plasma column excitation in small diameter (4 mm) ceramic capillary, is reported. Radiation at 46.9 nm, produced by a very fast high voltage pulse (∼50 ns, 300 kV) in Neon-like argon, according to a technique initiated by J.J.Rocca et al., has been investigated by multilayer mirrors. Evidence is given for Z-pinch in the plasma column at about 40 kA, with associated X-ray generation. Application of this table-top X-ray source have been considered in different fields as X-ray microscopy and lithography
Toward a full optimization of a highly saturated soft-X-ray laser beam produced in extremely long capillary discharge amplifiers
No full textWe report a substantial improvement of the output characteristics of a capillary discharge single-pass 46.9 nm Ne-like Ar soft-X-ray laser obtained by increasing the length of laser amplifier from 20 up to 45 cm. The longest plasma amplifier is characterized by an aspect ratio well exceeding 1000:1. The plasma columns are pumped by long 180 ns half-cycle duration, low amplitude 17-20 kA current pulses inside 3 mm in diameter alumina capillary channels filled with Ar at pressures of 0.25-0.55 Torr. Through the elongation of the plasma we produce a highly saturated regime of operation, where the plasma medium is three times the saturation length, the output pulse energy is of 300 μJ and the pulse duration of 1.7 ns. The far-field intensity distribution, reaching value <1 mrad and the coherence properties of the laser, both have been also shown to improve with the increase of the capillary length. The stable operation of the laser has been produced at pulse repetition rate up to 0.1 Hz. © 2003 Elsevier B.V. All rights reserved
Search for gravitational waves from intermediate mass binary black holes
No full textWe present the results of a weakly modeled burst search for gravitational waves from mergers of nonspinning intermediate mass black holes in the total mass range 100-450Msun and with the component mass ratios between 1∶1 and 4∶1. The search was conducted on data collected by the LIGO and Virgo detectors between November of 2005 and October of 2007. No plausible signals were observed by the search which constrains the astrophysical rates of the intermediate mass black holes mergers as a function of the component masses. In the most efficiently detected bin centered on 88+88Msun, for nonspinning sources, the rate density upper limit is 0.13 per Mpc3 per Myr at the 90% confidence level
Soft X-ray plasma source for atmospheric-pressure microscopy, radiobiology and other applications
No full textA large-volume non-conventional XeCl excimer laser (Hercules) emitting long pulses (from 10 ns up to 120 ns at a wavelength of 308 nm) has been used to drive a soft X-ray plasma source. The X-rays pulse duration and the energy conversion efficiency in different spectral regions have been measured; X-rays emission lasting up to 100 ns has been obtained in the 70 eV region. The dependence of X-ray pulse duration on the size of the laser spot is discussed. The X-ray source can be operated both in vacuum and in helium at atmospheric pressure. This allows irradiating over a large area both for contact microscopy of living specimens (up to 1 mm2 windows) and for radiobiology (up to few cm2 windows). The experimental results obtained for these two applications as well as for radiographic images of living insects are discussed. © Società Italiana di Fisica
Applications des plasmas produits par le laser à excimères HERCULES-L : Du recuit du silicium à la lithographie par rayons X
No full textUn laser à excimères de grand volume, HERCULES-L, a été développé dans le cadre d'un programme européen pour des applications industrielles concernant le traitement de surface du silicium et la génération de plasmas par laser. Les performances de ce laser sont particulièrement adaptées pour le traitement de grandes surfaces et pour la création de photons EUV (hv ~ 100 eV) par plasma assisté par laser
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