81 research outputs found
Radiation imaging apparatus
A radiation imaging system using a charge multiplier and a position sensitive anode in the form of periodically arranged sets of interconnected anode regions for detecting the position of the centroid of a charge cloud arriving thereat from the charge multiplier. Various forms of improved position sensitive anodes having single plane electrode connections are disclosed. Various analog and digital signal processing systems are disclosed, including systems which use the fast response of microchannel plates, anodes and preamps to perform scintillation pulse height analysis digitally
FAUST Observations in the Fourth Galactic Quadrant
We analyze UV observations with FAUST of four sky fields in the general
direction of the fourth Galactic quadrant, in which we detect 777 UV sources.
This is ~50% more than detected originally by Bowyer et al (1995). We discuss
the source detection process and the identification of UV sources with optical
counterparts. For the first time in this project we use ground-based
objective-prism information for two of the fields, to select the best-matching
optical objects with which to identify the UV sources. Using this, and
correlations with existing catalogs, we present reliable identifications for
\~75% of the sources. Most of the remaining sources have assigned optical
counterparts, but lacking additional information we offer only plausible
identification. We discuss the types of objects found, and compare the observed
population with predictions of our UV Galaxy model.Comment: Dedicated to the memory of Barry Lasker. MNRAS in press. 95 pages, 9
figures. Figures 1-4 are very large; this version contains reduced-format
images. The full images are available at
ftp://wise3.tau.ac.il/ftp/pub/noah/M83_*.p
Hidden Subluminous sd/wd among the FAUST UV sources toward OPHIUCHUS
A UV image in the direction of Ophiuchus, obtained with the FAUST instrument
is analysed. Suitable candidates as unrecognized subluminous stars are selected
comparing the observed UV flux to the predicted one. The uv-excess objects were
observed at the 1.0 m Wise telescope. This method yields to the detection of
eight broad Balmer lines objects. Six are classified as sds and two wds,
comparing the Hbeta line profile with that of stellar model atmospheres.Comment: 2 pages, including 2 figures. To appear in the Proceedings of the
13th European Workshop on White Dwarfs. NATO Science Series II, Kluwer
Academic Publishe
Fabrication of the DESI Corrector Lenses
The Dark Energy Spectroscopic Instrument (DESI) is under construction to
measure the expansion history of the Universe using the Baryon Acoustic
Oscillation technique. The spectra of 35 million galaxies and quasars over
14000 square degrees will be measured during the life of the experiment. A new
prime focus corrector for the KPNO Mayall telescope will deliver light to 5000
fiber optic positioners. The fibers in turn feed ten broad-band spectrographs.
We describe the DESI corrector optics, a series of six fused silica and
borosilicate lenses. The lens diameters range from 0.8 to 1.1 meters, and their
weights 84 to 237 kg. Most lens surfaces are spherical, and two are challenging
10th-order polynomial aspheres. The lenses have been successfully polished and
treated with an antireflection coating at multiple subcontractors, and are now
being integrated into the DESI corrector barrel assembly at University College
London. We describe the final performance of the lenses in terms of their
various parameters, including surface figure, homogeneity, and others, and
compare their final performance against the demanding DESI corrector
requirements. Also we describe the reoptimization of the lens spacing in their
corrector barrel after their final measurements are known. Finally we assess
the performance of the corrector as a whole, compared to early budgeted
estimates
Evidence Against the Sciama Model of Radiative Decay of Massive Neutrinos
We report on spectral observations of the night sky in the band around 900
angstroms where the emission line in the Sciama model of radiatively decaying
massive neutrinos would be present. The data were obtained with a high
resolution, high sensitivity spectrometer flown on the Spanish MINISAT
satellite. The observed emission is far less intense than that expected in the
Sciama model.Comment: 9 pages, accepted to Ap
Far Ultraviolet Absolute Flux of alpha Virginis
We present the far ultraviolet spectrum of alpha Virginis taken with EURD
spectrograph on-board MINISAT-01. The spectral range covered is from ~900 to
1080 A with 5 A spectral resolution. We have fitted Kurucz models to IUE
spectra of alpha Vir and compared the extension of the model to our wavelengths
with EURD data. This comparison shows that EURD fluxes are consistent with the
prediction of the model within 20-30%, depending on the reddening assumed. EURD
fluxes are consistent with Voyager observations but are ~60% higher than most
previous rocket observations of alpha Vir.Comment: 13 pages, 4 figures. Submitted to The Astrophysical Journa
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