565 research outputs found
W. M. Keck Observatory's next-generation adaptive optics facility
We report on the preliminary design of W.M. Keck Observatory's (WMKO's) next-generation adaptive optics (NGAO) facility. This facility is designed to address key science questions including understanding the formation and evolution of today's galaxies, measuring dark matter in our galaxy and beyond, testing the theory of general relativity in the Galactic Center, understanding the formation of planetary systems around nearby stars, and exploring the origins of our own solar system. The requirements derived from these science questions have resulted in NGAO being designed to have near diffraction-limited performance in the near-IR (K-Strehl ~ 80%) over narrow fields (< 30" diameter) with modest correction down to ~ 700 nm, high sky coverage, improved sensitivity and contrast and improved photometric and astrometric accuracy. The resultant key design features include multi-laser tomography to measure the wavefront and correct for the cone effect, open loop AO-corrected near-IR tip-tilt sensors with MEMS deformable mirrors (DMs) for high sky coverage, a high order MEMS DM for the correction of atmospheric and telescope static errors to support high Strehls and high contrast companion sensitivity, point spread function (PSF) calibration to benefit quantitative astronomy, a cooled science path to reduce thermal background, and a high-efficiency science instrument providing imaging and integral field spectroscopy
The infrared imaging spectrograph (IRIS) for TMT: spectrograph design
The Infra-Red Imaging Spectrograph (IRIS) is one of the three first light
instruments for the Thirty Meter Telescope (TMT) and is the only one to
directly sample the diffraction limit. The instrument consists of a parallel
imager and off-axis Integral Field Spectrograph (IFS) for optimum use of the
near infrared (0.84um-2.4um) Adaptive Optics corrected focal surface. We
present an overview of the IRIS spectrograph that is designed to probe a range
of scientific targets from the dynamics and morphology of high-z galaxies to
studying the atmospheres and surfaces of solar system objects, the latter
requiring a narrow field and high Strehl performance. The IRIS spectrograph is
a hybrid system consisting of two state of the art IFS technologies providing
four plate scales (4mas, 9mas, 25mas, 50mas spaxel sizes). We present the
design of the unique hybrid system that combines the power of a lenslet
spectrograph and image slicer spectrograph in a configuration where major
hardware is shared. The result is a powerful yet economical solution to what
would otherwise require two separate 30m-class instruments.Comment: 15 pages, 11 figure
To robotize chemistry laboratories. An example of organic synthesis: 2-Boc-amino-N-hydroxy-3-phenyl-propionamide
The paper describes the development of periodic modules used for the peptide synthesis of hydroxamic acid. A powder conveyor using the principle of positive weighing distribution is described. Purification is provided using automatic filtration and a liquid— liquid extraction module separation device. Device quality is improved using failure mode and effects analysis
Optimization of control parameters of a hot cold controller by means of Simplex type methods
This paper describes a hot/cold controller for regulating crystallization
operations. The system was identified with a common method (the Broida method) and the parameters were obtained by the Ziegler-Nichols method. The paper shows that this empirical method will only allow a qualitative approach to regulation and that, in some instances, the parameters obtained are unreliable and therefore cannot be used to cancel variations between the set point and the actual values. Optimization methods were used to
determine the regulation parameters and solve this identcation problem. It was found that the weighted centroid method was the best one
Dynamic multilateral markets
We study dynamic multilateral markets, in which players' payoffs result from intra-coalitional bargaining. The latter is modeled as the ultimatum game with exogenous (time-invariant) recognition probabilities and unanimity acceptance rule. Players in agreeing coalitions leave the market and are replaced by their replicas, which keeps the pool of market participants constant over time. In this infinite game, we establish payoff uniqueness of stationary equilibria and the emergence of endogenous cooperation structures when traders experience some degree of (heterogeneous) bargaining frictions. When we focus on market games with different player types, we derive, under mild conditions, an explicit formula for each type's equilibrium payoff as the market frictions vanish
Lyot-plane phase masks for improved high-contrast imaging with a vortex coronagraph
Context. The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, a crucial capability for direct detection and characterization of exoplanets and circumstellar disks. Telescopes with aperture obstructions, such as secondary mirrors and spider support structures, require advanced coronagraph designs to provide adequate starlight suppression.
Aims. We introduce a phase-only Lyot-plane optic to the vortex coronagraph, which offers improved contrast performance on telescopes with complicated apertures. Potential solutions for the European Extremely Large Telescope (E-ELT) are described.
Methods. Adding a Lyot-plane phase mask relocates residual starlight away from a region of the image plane, thereby reducing stellar noise and improving sensitivity to off-axis companions. The phase mask is calculated using an iterative phase retrieval algorithm.
Results. Numerically, we achieve a contrast on the order of 10-6 for a companion with angular displacement as small as 4λ/D with an E-ELT type aperture. Even in the presence of aberrations, improved performance is expected compared to either a conventional vortex coronagraph or an optimized pupil plane phase element alone
W. M. Keck Observatory's next-generation adaptive optics facility
We report on the preliminary design of W.M. Keck Observatory's (WMKO's) next-generation adaptive optics (NGAO) facility. This facility is designed to address key science questions including understanding the formation and evolution of today's galaxies, measuring dark matter in our galaxy and beyond, testing the theory of general relativity in the Galactic Center, understanding the formation of planetary systems around nearby stars, and exploring the origins of our own solar system. The requirements derived from these science questions have resulted in NGAO being designed to have near diffraction-limited performance in the near-IR (K-Strehl ~ 80%) over narrow fields (< 30" diameter) with modest correction down to ~ 700 nm, high sky coverage, improved sensitivity and contrast and improved photometric and astrometric accuracy. The resultant key design features include multi-laser tomography to measure the wavefront and correct for the cone effect, open loop AO-corrected near-IR tip-tilt sensors with MEMS deformable mirrors (DMs) for high sky coverage, a high order MEMS DM for the correction of atmospheric and telescope static errors to support high Strehls and high contrast companion sensitivity, point spread function (PSF) calibration to benefit quantitative astronomy, a cooled science path to reduce thermal background, and a high-efficiency science instrument providing imaging and integral field spectroscopy
The VORTEX project: first results and perspectives
(abridged) Vortex coronagraphs are among the most promising solutions to
perform high contrast imaging at small angular separations. They feature a very
small inner working angle, a clear 360 degree discovery space, have
demonstrated very high contrast capabilities, are easy to implement on
high-contrast imaging instruments, and have already been extensively tested on
the sky. Since 2005, we have been designing, developing and testing an
implementation of the charge-2 vector vortex phase mask based on concentric
subwavelength gratings, referred to as the Annular Groove Phase Mask (AGPM).
Science-grade mid-infrared AGPMs were produced in 2012 for the first time,
using plasma etching on synthetic diamond substrates. They have been validated
on a coronagraphic test bench, showing broadband peak rejection up to 500:1 in
the L band, which translates into a raw contrast of about at
. Three of them have now been installed on world-leading
diffraction-limited infrared cameras (VLT/NACO, VLT/VISIR and LBT/LMIRCam).
During the science verification observations with our L-band AGPM on NACO, we
observed the beta Pictoris system and obtained unprecedented sensitivity limits
to planetary companions down to the diffraction limit (). More recently,
we obtained new images of the HR 8799 system at L band during the AGPM first
light on LMIRCam. After reviewing these first results obtained with
mid-infrared AGPMs, we will discuss the short- and mid-term goals of the
on-going VORTEX project, which aims to improve the performance of our vortex
phase masks for future applications on second-generation high-contrast imagers
and on future extremely large telescopes (ELTs).Comment: To appear in SPIE proceedings vol. 914
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