scholarly journals Simulating a dual beam combiner at SUSI for narrow-angle astrometry

2013 ◽  
Vol 36 (1-2) ◽  
pp. 195-221 ◽  
Author(s):  
Yitping Kok ◽  
Vicente Maestro ◽  
Michael J. Ireland ◽  
Peter G. Tuthill ◽  
J. Gordon Robertson
Keyword(s):  
Narrow Angle ◽  
Dual Beam ◽  
Beam Combiner

scholarly journals PHASE-REFERENCED INTERFEROMETRY AND NARROW-ANGLE ASTROMETRY WITH SUSI

2013 ◽  
Vol 02 (02) ◽  
pp. 1340011 ◽  
Author(s):  
Y. KOK ◽  
M. J. IRELAND ◽  
P. G. TUTHILL ◽  
J. G. ROBERTSON ◽  
B. A. WARRINGTON ◽  
...  
Keyword(s):  
Binary Stars ◽  
Photon Counting ◽  
Current Phase ◽  
Common Path ◽  
Narrow Angle ◽  
Stellar Interferometer ◽  
Dual Beam ◽  
Beam Combiner ◽  
Visible Wavelengths ◽  
Fringe Tracking

The Sydney University Stellar Interferometer (SUSI) now incorporates a new beam combiner, called the Microarc-second University of Sydney Companion Astrometry instrument (MUSCA), for the purpose of high precision differential astrometry of bright binary stars. Operating in the visible wavelength regime where photon-counting and post-processing fringe tracking is possible, MUSCA will be used in tandem with SUSI's primary beam combiner, Precision Astronomical Visible Observations (PAVO), to record high spatial resolution fringes and thereby measure the separation of fringe packets of binary stars. In its current phase of development, the dual beam combiner configuration has successfully demonstrated for the first time a dual-star phase-referencing operation in visible wavelengths. This paper describes the beam combiner optics and hardware, the network of metrology systems employed to measure every non-common path between the two beam combiners and also reports on a recent narrow-angle astrometric observation of δ Orionis A (HR 1852) as the project enters its on-sky testing phase.

scholarly journals Astrometry with the VLTI: calibration of the Fringe Sensor Unit for the PRIMA astrometric camera

2007 ◽  
Vol 3 (S248) ◽  
pp. 124-125 ◽  
Author(s):  
J. Sahlmann ◽  
R. Abuter ◽  
S. Ménardi ◽  
G. Vasisht
Keyword(s):  
Group Delay ◽  
Angular Separation ◽  
Calibration Procedure ◽  
Primary Objective ◽  
Stellar Objects ◽  
Phase Measurements ◽  
Sensor Unit ◽  
Narrow Angle ◽  
Dual Beam ◽  
Laser Metrology

AbstractThe future PRIMA facility at the Very Large Telescope Interferometer (VLTI) in astrometric mode offers the possibility to perform relative narrow-angle astrometry with 10 micro-arcsecond accuracy. This is achieved with a dual-beam interferometer concept, where a reference star and the scientific target, confined in a 60 arcsecond field, are observed simultaneously. The angular separation of the two stellar objects gives rise to an optical delay in the interferometer, which is measured by the Fringe Sensor Unit (FSU) and an internal laser metrology. PRIMA is using two FSU fringe detectors, each observing the interference of stellar beams coming from one of the two objects and measuring the corresponding phase and group delay. The astrometric observable, yielding the angular separation, is deduced from the group delay difference observed between the two objects. In addition, the FSU phase delay estimate is used as error signal for the fringe stabilisation loop of the VLTI. Both functions of the FSU require high precision fringe phase measurements with a goal of 1 nm rms (corresponding to λ/2000). These can only be achieved by applying a calibration procedure prior to the observing run. We discuss the FSU measurement principle and the applied algorithms. The calibration strategy and the methods used to derive the calibration parameters are presented. Special attention is given to the achieved measurement linearity and repeatability. The quality of the FSU calibration is crucial in order to achieve the ultimate accuracy and to fulfill the primary objective of PRIMA astrometry: the detection and characterisation of extrasolar planetary systems.

scholarly journals The Potential of Differential Astrometric Interferometry from the High Antarctic Plateau

2002 ◽  
Vol 19 (3) ◽  
pp. 318-322 ◽  
Author(s):  
James P. Lloyd ◽  
Ben R. Oppenheimer ◽  
James R. Graham
Keyword(s):  
Orbit Determination ◽  
Planet Detection ◽  
Antarctic Plateau ◽  
Narrow Angle ◽  
The Poor ◽  
Dual Beam ◽  
Infrared Background ◽  
Astrometric Observation ◽  
The Mean ◽  
The Antarctic

AbstractThe low infrared background and high atmospheric transparency are the principal advantages of Antarctic Plateau sites for astronomy. However, the poor seeing (between 1 and 3 as) negates much of the sensitivity improvements that the Antarctic atmosphere offers, compared to mid-latitude sites such as Mauna Kea or Cerro Paranal. The seeing at mid-latitude sites, though smaller in amplitude, is dominated by turbulence at altitudes of 10–20 km. Over the Antarctic Plateau, virtually no high altitude turbulence is present in the winter. The mean square error for an astrometric measurement with a dual-beam, differential astrometric interferometer in the very narrow angle regime is proportional to the integral of h2C2N(h). Therefore, sites at which the turbulence occurs only at low altitudes offer large gains in astrometric precision. We show that a modest interferometer at the South Pole can achieve 10 μ as differential astrometry 300 times faster than a comparable interferometer at a good mid-latitude site, in median conditions. Science programs that would benefit from such an instrument include planet detection and orbit determination, and astrometric observation of stars microlensed by dark matter candidates.

scholarly journals Single-mode waveguides for GRAVITY

2018 ◽  
Vol 614 ◽  
pp. A70 ◽  
Author(s):  
K. Perraut ◽  
L. Jocou ◽  
J. P. Berger ◽  
A. Chabli ◽  
V. Cardin ◽  
...  
Keyword(s):  
Integrated Optics ◽  
Near Infrared ◽  
Thermal Emission ◽  
Spectral Band ◽  
Polarized Light ◽  
Single Mode ◽  
Galactic Centre ◽  
Interferometric Imaging ◽  
Narrow Angle ◽  
Beam Combiner

Context. Within the framework of the second-generation instrumentation of the Very Large Telescope Interferometer of the European Southern Observatory we have developed the four-telescope beam combiner in integrated optics. Aims. We optimized the performance of such beam combiners, for the first time in the near-infrared K band, for the GRAVITY instrument dedicated to the study of the close environment of the galactic centre black hole by precision narrow-angle astrometry and interferometric imaging. Methods. We optimized the design of the integrated optics chip and the manufacturing technology as well, to fulfil the very demanding throughput specification. We also designed an integrated optics assembly able to operate at 200 K in the GRAVITY cryostat to reduce thermal emission. Results. We manufactured about 50 beam combiners by silica-on-silicon etching technology. We glued the best combiners to single-mode fluoride fibre arrays that inject the VLTI light into the integrated optics beam combiners. The final integrated optics assemblies have been fully characterized in the laboratory and through on-site calibrations: their global throughput over the K band is higher than 55% and the instrumental contrast reaches more than 95% in polarized light, which is well within the GRAVITY specifications. Conclusions. While integrated optics technology is known to be mature enough to provide efficient and reliable beam combiners for astronomical interferometry in the H band, we managed to successfully extend it to the longest wavelengths of the K band and to manufacture the most complex integrated optics beam combiner in this specific spectral band.

Influence of the Aperture Edge Diffraction Effects on the Mutual Coupling Compensation Technique in Small Planar Antenna Arrays

2011 ◽  
Vol 57 (1) ◽  
pp. 115-120 ◽  
Author(s):  
Mariusz Zamłyński ◽  
Piotr Słobodzian
Keyword(s):  
Antenna Arrays ◽  
Mutual Coupling ◽  
Planar Antenna ◽  
Sidelobe Level ◽  
Edge Diffraction ◽  
Narrow Angle ◽  
Compensation Technique ◽  
Diffraction Effects ◽  
Linear Antenna Arrays

Influence of the Aperture Edge Diffraction Effects on the Mutual Coupling Compensation Technique in Small Planar Antenna Arrays In this paper the quality of a technique to compensate for mutual coupling (and other phenomena) in small linear antenna arrays is investigated. The technique consists in calculation of a coupling matrix, which is than used to determine corrected antenna array excitation coefficients. Although the technique is known for more than 20 years, there is still very little information about how different phenomena existing in a real antenna arrays influence its performance. In this paper two models of antenna arrays are used. In the first model the effect of mutual coupling is separated from the aperture edge diffraction. In the second model antenna both mutual coupling and aperture edge diffraction effects are included. It is shown that mutual coupling itself can be compensated very well and an ultralow sidelobe level (i.e. -50 dB) could be achieved in practice. In the presence of diffraction effects -46.3 dB sidelobe level has been attained, but radiation pattern can be controled only in narrow angle range (i.e. up to ±60°).

3D Investigations of Plasma Erosion Craters using FIB/SEM Dual-Beam Techniques

2006 ◽  
Vol 43 (9) ◽  
pp. 470-482 ◽  
Author(s):  
Nicolas Jeanvoine ◽  
Christian Holzapfel ◽  
Flavio Soldera ◽  
Frank Mücklich
Keyword(s):  
Dual Beam ◽  
Plasma Erosion

Application of Automated FIB for TEM Sample Preparation in Semiconductor Failure Analysis

2014 ◽  
Author(s):  
Jie Zhu ◽  
Soo Sien Seah ◽  
Irene Tee ◽  
Bing Hai Liu ◽  
Eddie Er ◽  
...  
Keyword(s):  
Sample Preparation ◽  
Success Rate ◽  
Protective Layer ◽  
Factors Affecting ◽  
Dual Beam ◽  
Lamella Thickness ◽  
Surface Patterns ◽  
Working Parameters ◽  
Practical Factors ◽  
High Flexibility

Abstract In this paper, we describe automated FIB for TEM sample preparation using iFast software on a Helios 450HP dual-beam system. A robust iFast automation recipe needs to consider as many variables as possible in order to ensure consistent sample quality and high success rate. Variations mainly come from samples of different materials, structures, surface patterns, surface topography and surface charging. The recipe also needs to be user-friendly and provide high flexibility by allowing users to choose preferable working parameters for specific types of samples, such as: grounding, protective layer coating, milling steps, and final TEM lamella thickness/width. In addition to the iFast recipe, other practical factors affecting automation success rate are also discussed and highlighted.

To Eliminate Curtain Effect of FIB TEM Samples by a Combination of Sample Dicing and Backside Milling

2014 ◽  
Author(s):  
Jian-Shing Luo ◽  
Hsiu Ting Lee
Keyword(s):  
Sample Preparation ◽  
Focused Ion Beam ◽  
Preparation Method ◽  
Low Cost ◽  
Ion Beam ◽  
Sample Preparation Method ◽  
Site Specific ◽  
Dual Beam ◽  
Transmission Electron

Abstract Several methods are used to invert samples 180 deg in a dual beam focused ion beam (FIB) system for backside milling by a specific in-situ lift out system or stages. However, most of those methods occupied too much time on FIB systems or requires a specific in-situ lift out system. This paper provides a novel transmission electron microscopy (TEM) sample preparation method to eliminate the curtain effect completely by a combination of backside milling and sample dicing with low cost and less FIB time. The procedures of the TEM pre-thinned sample preparation method using a combination of sample dicing and backside milling are described step by step. From the analysis results, the method has applied successfully to eliminate the curtain effect of dual beam FIB TEM samples for both random and site specific addresses.

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