scholarly journals A High Resolution XUV Grating Monochromator for the Spectral Selection of Ultrashort Harmonic Pulses

2019 ◽  
Vol 9 (12) ◽  
pp. 2502
Author(s):  
Nicola Fabris ◽  
Paolo Miotti ◽  
Fabio Frassetto ◽  
Luca Poletto
Keyword(s):  
Extreme Ultraviolet ◽  
Spectral Lines ◽  
Resolving Power ◽  
High Spectral Resolution ◽  
Test Case ◽  
Optical Elements ◽  
Broad Energy Range ◽  
Grating Monochromator ◽  
Set Up ◽  
Selection Of

A new monochromator with high spectral resolution in the extreme ultraviolet (XUV) has been developed for high-order laser harmonics selection. The system has three optical elements—a cylindrical (or spherical) focusing mirror, a uniform-line-spaced plane grating, and a plane mirror. The last element is required to maintain the focus on a fixed vertical slit when the grating subtended angle is changed in order to minimize the spectral defocusing aberration. The parameters of the focusing mirror are determined to introduce a coma that compensates for the coma given by the grating. The possibility of using two interchangeable gratings made the set-up optimized for a broad energy range of 12–50 eV. As a design test case, the set-up has been applied to a selection of the discrete spectral lines emitted by a gas-discharge lamp as the XUV source, obtaining a resolving power E/ Δ E > 3000.

Application of Multiwavelength Pyrometry in Microwave Processing of Materials

1996 ◽  
Vol 430 ◽  
Author(s):  
R. S. Donnan ◽  
M. Samandi
Keyword(s):  
Resolving Power ◽  
Single Element ◽  
The Past ◽  
Multiple Wavelength ◽  
High Temperature Measurement ◽  
Wide Range ◽  
Multiwavelength Pyrometry ◽  
Grating Monochromator ◽  
Microwave Applicator ◽  
Set Up

AbstractOver the past decade microwave energy has been increasingly used in materials processing, especially for sintering and more recently for the joining of advanced ceramics. However the hostile electromagnetic and plasma environment within a high power (1–6 kW) microwave applicator poses serious problems for very accurate high temperature measurement by precluding the use of existing classes of thermometry. For instance, conventional probe-based thermometry, multiple-wavelength ratio pyrometry and even the more recently developed technologies of optical fibre thermometry by fluoroptics and radiometry, are either incompatible or of restricted application. The main aim of this paper is to propose multiwavelength pyrometry as a viable technique for wide range (500–5000 K) thermometry in hostile electromagnetic and plasma environments. After briefly reviewing the physical basis of its operation, the experimental set up of the multiwavelength pyrometer is outlined, and consists of a comparatively inexpensive low resolving power grating monochromator and a PbS infrared single element detector. Results are presented that compare the measurements during conventional/microwave heating trials, from this multiwavelength pyrometer and from a K-type thermocouple, a double-wavelength ratio pyrometer and a single wavelength pyrometer aimed at a dummy target (carbon/metal).

scholarly journals Photospheric molecular line profiles in cool stars

1981 ◽  
Vol 59 ◽  
pp. 119-124
Author(s):  
S.T. Ridgway ◽  
E.D. Friel
Keyword(s):  
Spectral Lines ◽  
High Spectral Resolution ◽  
High Signal ◽  
Line Profiles ◽  
Signal To Noise ◽  
Molecular Line ◽  
Ejection Process ◽  
Cool Stars ◽  
Mass Ejection ◽  
Selection Of

AbstractSpectral lines of the ΔV=2 rotation vibration bands of CO are well suited for study of photospheric motions and the mass ejection process in cool stars. We have obtained high spectral resolution (1.8 km/sec) and high signal-to-noise (>102) line profiles for a selection of K and M giants. These profiles are being studied for evidence of gas motions in the photosphere and near circumstellar regions.

A high-efficiency and high-spectral-resolution EUV/soft X-ray monochromator based on off-plane diffraction

2020 ◽  
Vol 27 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Werner Jark
Keyword(s):  
Spectral Resolution ◽  
High Efficiency ◽  
Extreme Ultraviolet ◽  
Incident Beam ◽  
Grazing Incidence ◽  
Incident Radiation ◽  
High Spectral Resolution ◽  
X Ray ◽  
Grating Monochromator ◽  
Plane Diffraction

The most efficient diffraction at a periodic grating structure is expected to take place when the incident radiation can be considered to have been specularly reflected off the inclined part of grooves that are positioned parallel to the trajectory of the incident beam. Very encouraging results for this configuration, in which the diffraction takes place off-plane, have been reported recently for a grating to be used in a spectrometer for space science investigations. This grating provided high efficiency for a relatively large groove density and a large blaze angle. High efficiency was observed even in higher diffraction orders up to the fourth order. Here the performance parameters, especially for the combination of diffraction efficiency and achievable spectral resolution, will be discussed for a grating used in a grazing-incidence plane-grating monochromator for monochromatization of synchrotron radiation in the extreme ultraviolet (EUV) and soft X-ray range with photon energies between 30 eV and 2000 eV. It is found that the instrument can provide competitive spectral resolution in comparison with the use of in-plane diffraction. In the case of comparable spectral resolution, the off-plane diffraction is found to provide superior efficiency.

On obtaining high spectral resolution in extreme ultraviolet/soft X-ray monochromators operating off-plane diffraction in a divergent incident beam

2020 ◽  
Vol 27 (6) ◽  
pp. 1499-1509
Author(s):  
Werner Jark
Keyword(s):  
Spectral Resolution ◽  
Extreme Ultraviolet ◽  
Specular Reflection ◽  
Incident Beam ◽  
Diffraction Order ◽  
Source Size ◽  
Resolving Power ◽  
High Spectral Resolution ◽  
Radiation Beam ◽  
X Ray

When the trajectory of an incident beam is oriented parallel to the grooves of a periodic grating structure the radiation beam is diffracted off-plane orthogonal to the plane of incidence. The diffraction efficiency in this condition is very high and in a grating with a sawtooth profile it can approach the reflection coefficient for a simple mirror, when the diffraction order of interest follows the direction for specular reflection at the flat part of the steps. When this concept is used in a plane grating in a monochromator for synchrotron radiation sources, the incident beam is almost always collimated in order to minimize any deterioration of the beam properties due to aberrations, which will be introduced in the diffraction process when an uncollimated beam is used. These aberrations are very severe when the groove density is constant. It will be shown that the effect of these aberrations can be corrected after the diffraction by the use of astigmatic focusing. The latter can be provided by a crossed mirror pair with different focal lengths in the corresponding orthogonal directions. Then a monochromator based on this concept can provide source size limited spectral resolution in an uncollimated incident beam. This is identical to the spectral resolution that can be provided by the same grating when operated at the same position in a collimated incident beam. The source size limited spectral resolution in this case corresponds to a high spectral resolving power of better than ΔE/E = 10 000 for photon energies around 300 eV in the soft X-ray range.

scholarly journals Zeeman Doppler Imaging

1995 ◽  
Vol 149 ◽  
pp. 340-349
Author(s):  
M. Semel
Keyword(s):  
Magnetic Field ◽  
Spectral Lines ◽  
Doppler Imaging ◽  
High Spectral Resolution ◽  
Two Dimensional ◽  
Stellar Rotation ◽  
Time Variations ◽  
Set Up ◽  
Star Surface ◽  
The Magnetic Field

AbstractStellar rotation maps the surface of a star into its line spectrum and gives a dimension to a point on the star - the Doppler dimension. This is of great importance for the detection of Zeeman polarization especially in certain cases. Typically a magnetic configuration will exhibit both polarities, thus the polarization signals of oposite signs may superpose and cancel. The Doppler coordinate will be in general different for parts of the stars having different polarities and therefore the polarization signals will also appear at different wavelengths and will not cancel. Moreover, the time variations plus the Doppler coordinate constitutes two variables that may allow the reconstruction of two dimensional map of the magnetic field over the star surface.Attention will be given to the set-up that allows spectropolarimetry with high spectral resolution and high S/N ratio. The use of cross dispersion spectrographs allows one to observe several tens of spectral lines. The method of adding signals to increase S/N ratio will be indicated.

scholarly journals Lensless Reflection Imaging of Obliquely Illuminated Objects I: Choosing a Domain for Phase Retrieval and Ptychography

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1439
Author(s):  
Igor A. Artyukov ◽  
Nikolay L. Popov ◽  
Alexander V. Vinogradov
Keyword(s):  
Inverse Problem ◽  
Phase Retrieval ◽  
Extreme Ultraviolet ◽  
X Rays ◽  
Reflection Mode ◽  
Optical Elements ◽  
Diffraction Integral ◽  
Diffraction Patterns ◽  
Set Up ◽  
Object Material

Ptychography is a lensless imaging technology that is validated from hard X-rays to terahertz spectral range. It is most attractive for extreme ultraviolet (EUV) and X-rays as optical elements are expensive and often not available. Typically, the set up involves coherently illuminated object that directs the scattered radiation normally to detector which is parallel to the object plane. Computer processing of diffraction patterns obtained when scanning the object gives the image, more precisely, the distribution of intensity and phase on its surface. However, this scheme is inefficient for EUV and X-rays due to poor reflectivity and low penetration in all materials. Reflection mode ptychography solves the problem if illumination angles do not exceed the critical angle of object material. Changing the geometry of experiment changes physical and mathematical model of image formation. Including: diffraction integral describing beam propagation from object to detector, inverse problem, optimization of object illumination angle, position and orientation of detector, choosing size and grid of coordinate and frequency computer domains. This paper considers the wavefield scattered to detector by obliquely illuminated object and determines a domain for processing of obtained scans. Solution of inverse problem with phase retrieval and resulting numerical images will be presented in the next paper.

Platelet Anti-Aggregating Activity and Tolerance of Clopidogrel in Atherosclerotic Patients

1996 ◽  
Vol 76 (06) ◽  
pp. 0939-0943 ◽  
Author(s):  
B Boneu ◽  
G Destelle ◽  
Keyword(s):  
Platelet Aggregation ◽  
Large Scale ◽  
Bleeding Time ◽  
Antithrombotic Activity ◽  
Ambulatory Patients ◽  
Patients At Risk ◽  
Set Up ◽  
Ischemic Events ◽  
Large Scale Clinical Trial ◽  
Selection Of

SummaryThe anti-aggregating activity of five rising doses of clopidogrel has been compared to that of ticlopidine in atherosclerotic patients. The aim of this study was to determine the dose of clopidogrel which should be tested in a large scale clinical trial of secondary prevention of ischemic events in patients suffering from vascular manifestations of atherosclerosis [CAPRIE (Clopidogrel vs Aspirin in Patients at Risk of Ischemic Events) trial]. A multicenter study involving 9 haematological laboratories and 29 clinical centers was set up. One hundred and fifty ambulatory patients were randomized into one of the seven following groups: clopidogrel at doses of 10, 25, 50,75 or 100 mg OD, ticlopidine 250 mg BID or placebo. ADP and collagen-induced platelet aggregation tests were performed before starting treatment and after 7 and 28 days. Bleeding time was performed on days 0 and 28. Patients were seen on days 0, 7 and 28 to check the clinical and biological tolerability of the treatment. Clopidogrel exerted a dose-related inhibition of ADP-induced platelet aggregation and bleeding time prolongation. In the presence of ADP (5 \lM) this inhibition ranged between 29% and 44% in comparison to pretreatment values. The bleeding times were prolonged by 1.5 to 1.7 times. These effects were non significantly different from those produced by ticlopidine. The clinical tolerability was good or fair in 97.5% of the patients. No haematological adverse events were recorded. These results allowed the selection of 75 mg once a day to evaluate and compare the antithrombotic activity of clopidogrel to that of aspirin in the CAPRIE trial.

The Emergence of Rabbinic Culture from the Perspective of Qumran

2015 ◽  
Vol 6 (2) ◽  
pp. 253-274
Author(s):  
Vered Noam
Keyword(s):  
Early Stage ◽  
Second Temple ◽  
Test Case ◽  
Literary Works ◽  
Jewish Culture ◽  
The Bible ◽  
Set Up

The rabbinic halakhic system, with its many facets and the literary works that comprise it, reflects a new Jewish culture, almost completely distinct in its halakhic content and scope from the biblical and postbiblical culture that preceded it. By examining Jewish legislation in the area of corpse impurity as a test case, the article studies the implications of Qumranic halakhah, as a way-station between the Bible and the Mishnah, for understanding how Tannaitic halakhah developed. The impression obtained from the material reviewed in the article is that the direction of the “Tannaitic revolution” was charted, its methods set up, and its principles established, at a surprisingly early stage, before the destruction of the Second Temple, and thus at the same time that the Qumran literature was created.

STUDY OF INACCURACY IN THE OPERATION OF THE MAIN CONTROLLER OF STB MACHINE

2019 ◽  
Keyword(s):  
Normal Distribution ◽  
Stable Process ◽  
Random Errors ◽  
Actual Length ◽  
Experimental Data Processing ◽  
Set Up ◽  
Main Regulator ◽  
Transmission Gear ◽  
Selection Of

At production of fabrics, including fabrics for agricultural purpose, an important role is played by the cor-rect adjustment of operation of machine main regulator. The quality of setup of machine main controller is determined by the proper selection of rotation angle of warp beam weaving per one filling thread. In the pro-cess of using the regulator as a result of mistakes in adjustment, wear of transmission gear and backlashes in connections of details there are random changes in threads length. The purpose of the article is the research of property of random errors of basis giving by STB machine regulator. Mistakes can be both negative, and positive. In case of emergence only negative or only positive mistakes operation of the machine becomes im-possible as there will be a consecutive accumulation of mistakes. As a result of experimental data processing for stable process of weaving and the invariable diameter of basis threads winding of threads it is revealed that the random error of giving is set up as linear function of the accidental length having normal distribution. Measurements of accidental deviations in giving of a basis by the main regulator allowed to construct a curve of normal distribution of its actual length for one pass of weft thread. The presented curve of distribution of random errors in giving of a basis is the displaced curve of normal distribution of the accidental sizes. Also we define the density of probability of normal distribution of basis giving errors connected with a margin er-ror operation of the main regulator knowing of which allows to plan ways of their decrease that is important for improvement of quality of the produced fabrics.

Sign in / Sign up

Export Citation Format

Share Document