27,153 research outputs found
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
Comb-calibrated solar spectroscopy through a multiplexed single-mode fiber channel
We investigate a new scheme for astronomical spectrograph calibration using
the laser frequency comb at the Solar Vacuum Tower Telescope on Tenerife. Our
concept is based upon a single-mode fiber channel, that simultaneously feeds
the spectrograph with comb light and sunlight. This yields nearly perfect
spatial mode matching between the two sources. In combination with the absolute
calibration provided by the frequency comb, this method enables extremely
robust and accurate spectroscopic measurements. The performance of this scheme
is compared to a sequence of alternating comb and sunlight, and to absorption
lines from Earth's atmosphere. We also show how the method can be used for
radial-velocity detection by measuring the well-explored 5-minute oscillations
averaged over the full solar disk. Our method is currently restricted to solar
spectroscopy, but with further evolving fiber-injection techniques it could
become an option even for faint astronomical targets.Comment: 21 pages, 11 figures. A video abstract for this paper is available on
youtube. For watching the video, please follow
https://www.youtube.com/watch?v=oshdZgrt89I . The video abstract is also
available for streaming and download on the related article website of New
Journal of Physic
Properties and Performance of Two Wide Field of View Cherenkov/Fluorescence Telescope Array Prototypes
A wide field of view Cherenkov/fluorescence telescope array is one of the
main components of the Large High Altitude Air Shower Observatory project. To
serve as Cherenkov and fluorescence detectors, a flexible and mobile design is
adopted for easy reconfiguring of the telescope array. Two prototype telescopes
have been constructed and successfully run at the site of the ARGO-YBJ
experiment in Tibet. The features and performance of the telescopes are
presented
SparsePak: A Formatted Fiber Field-Unit for The WIYN Telescope Bench Spectrograph. II. On-Sky Performance
We present a performance analysis of SparsePak and the WIYN Bench
Spectrograph for precision studies of stellar and ionized gas kinematics of
external galaxies. We focus on spectrograph configurations with echelle and
low-order gratings yielding spectral resolutions of ~10000 between 500-900nm.
These configurations are of general relevance to the spectrograph performance.
Benchmarks include spectral resolution, sampling, vignetting, scattered light,
and an estimate of the system absolute throughput. Comparisons are made to
other, existing, fiber feeds on the WIYN Bench Spectrograph. Vignetting and
relative throughput are found to agree with a geometric model of the optical
system. An aperture-correction protocol for spectrophotometric standard-star
calibrations has been established using independent WIYN imaging data and the
unique capabilities of the SparsePak fiber array. The WIYN
point-spread-function is well-fit by a Moffat profile with a constant power-law
outer slope of index -4.4. We use SparsePak commissioning data to debunk a
long-standing myth concerning sky-subtraction with fibers: By properly treating
the multi-fiber data as a ``long-slit'' it is possible to achieve precision sky
subtraction with a signal-to-noise performance as good or better than
conventional long-slit spectroscopy. No beam-switching is required, and hence
the method is efficient. Finally, we give several examples of science
measurements which SparsePak now makes routine. These include H
velocity fields of low surface-brightness disks, gas and stellar
velocity-fields of nearly face-on disks, and stellar absorption-line profiles
of galaxy disks at spectral resolutions of ~24,000.Comment: To appear in ApJSupp (Feb 2005); 19 pages text; 7 tables; 27 figures
(embedded); high-resolution version at
http://www.astro.wisc.edu/~mab/publications/spkII_pre.pd
Testing QoE in Different 3D HDTV Technologies
The three dimensional (3D) display technology has started flooding the consumer television market. There is a number of different systems available with different marketing strategies and different advertised advantages. The main goal of the experiment described in this paper is to compare the systems in terms of achievable Quality of Experience (QoE) in different situations. The display systems considered are the liquid crystal display using polarized light and passive lightweight glasses for the separation of the left- and right-eye images, a plasma display with time multiplexed images and active shutter glasses and a projection system with time multiplexed images and active shutter glasses. As no standardized test methodology has been defined for testing of stereoscopic systems, we develop our own approach to testing different aspects of QoE on different systems without reference using semantic differential scales. We present an analysis of scores with respect to different phenomena under study and define which of the tested aspects can really express a difference in the performance of the considered display technologies
Beam instrumentation for the Tevatron Collider
The Tevatron in Collider Run II (2001-present) is operating with six times
more bunches and many times higher beam intensities and luminosities than in
Run I (1992-1995). Beam diagnostics were crucial for the machine start-up and
the never-ending luminosity upgrade campaign. We present the overall picture of
the Tevatron diagnostics development for Run II, outline machine needs for new
instrumentation, present several notable examples that led to Tevatron
performance improvements, and discuss the lessons for future colliders
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