15,169 research outputs found
JPCam: A 1.2Gpixel camera for the J-PAS survey
JPCam is a 14-CCD mosaic camera, using the new e2v 9k-by-9k 10microm-pixel
16-channel detectors, to be deployed on a dedicated 2.55m wide-field telescope
at the OAJ (Observatorio Astrofisico de Javalambre) in Aragon, Spain. The
camera is designed to perform a Baryon Acoustic Oscillations (BAO) survey of
the northern sky. The J-PAS survey strategy will use 54 relatively narrow-band
(~13.8nm) filters equi-spaced between 370 and 920nm plus 3 broad-band filters
to achieve unprecedented photometric red-shift accuracies for faint galaxies
over ~8000 square degrees of sky. The cryostat, detector mosaic and read
electronics is being supplied by e2v under contract to J-PAS while the
mechanical structure, housing the shutter and filter assembly, is being
designed and constructed by a Brazilian consortium led by INPE (Instituto
Nacional de Pesquisas Espaciais). Four sets of 14 filters are placed in the
ambient environment, just above the dewar window but directly in line with the
detectors, leading to a mosaic having ~10mm gaps between each CCD. The massive
500mm aperture shutter is expected to be supplied by the Argelander-Institut
fur Astronomie, Bonn. We will present an overview of JPCam, from the filter
configuration through to the CCD mosaic camera. A brief outline of the main
J-PAS science projects will be included.Comment: 11 pages and 9 figure
Research and Development for a Gadolinium Doped Water Cherenkov Detector
The proposed introduction of a soluble gadolinium (Gd) compound into water
Cherenkov detectors can result in a high efficiency for the detection of free
neutrons capturing on the Gd. The delayed 8 MeV gamma cascades produced by
these captures, in coincidence with a prompt positron signal, serve to uniquely
identify electron antineutrinos interacting via inverse beta decay. Such
coincidence detection can reduce backgrounds, allowing a large Gd-enhanced
water Cherenkov detector to make the first observation of supernova relic
neutrinos and high precision measurements of Japan's reactor antineutrino flux,
while still allowing for all current physics studies to be continued. Now, a
dedicated Gd test facility is operating in the Kamioka Mine. This new facility
houses everything needed to successfully operate a Gd doped water Cherenkov
detector. Successful running of this facility will demonstrate that adding Gd
salt to SK is both safe for the detector and is capable of delivering the
expected physics benefits.Comment: Proceedings from the Technology and Instrumentation for Particle
Physics 2011 (TIPP 2011) conferenc
Comparison of filters for detecting gravitational wave bursts in interferometric detectors
Filters developed in order to detect short bursts of gravitational waves in
interferometric detector outputs are compared according to three main points.
Conventional Receiver Operating Characteristics (ROC) are first built for all
the considered filters and for three typical burst signals. Optimized ROC are
shown for a simple pulse signal in order to estimate the best detection
efficiency of the filters in the ideal case, while realistic ones obtained with
filters working with several ``templates'' show how detection efficiencies can
be degraded in a practical implementation. Secondly, estimations of biases and
statistical errors on the reconstruction of the time of arrival of pulse-like
signals are then given for each filter. Such results are crucial for future
coincidence studies between Gravitational Wave detectors but also with neutrino
or optical detectors. As most of the filters require a pre-whitening of the
detector noise, the sensitivity to a non perfect noise whitening procedure is
finally analysed. For this purpose lines of various frequencies and amplitudes
are added to a Gaussian white noise and the outputs of the filters are studied
in order to monitor the excess of false alarms induced by the lines. The
comparison of the performances of the different filters finally show that they
are complementary rather than competitive.Comment: 32 pages (14 figures), accepted for publication in Phys. Rev.
Destiny: A Candidate Architecture for the Joint Dark Energy Mission
Destiny is a simple, direct, low cost mission to determine the properties of
dark energy by obtaining a cosmologically deep supernova (SN) type Ia Hubble
diagram. Operated at L2, its science instrument is a 1.65m space telescope,
featuring a grism-fed near-infrared (NIR) (0.85-1.7micron) survey
camera/spectrometer with a 0.12 square degree field of view. During its
two-year primary mission, Destiny will detect, observe, and characterize ~3000
SN Ia events over the redshift interval 0.4<z<1.7 within a 3 square degree
survey area. In conjunction with ongoing ground-based SN Ia surveys for z<0.8,
Destiny mission data will be used to construct a high-precision Hubble diagram
and thereby constrain the dark energy equation of state from a time when it was
strongly matter-dominated to the present when dark energy dominates. The
grism-images simultaneously provide broad-band photometry, redshifts, and SN
classification, as well as time-resolved diagnostic data for investigating
additional SN luminosity diagnostics. Destiny will be used in its third year as
a high resolution, wide-field imager to conduct a multicolor NIR weak lensing
(WL) survey covering 1000 square degrees. The large-scale mass power spectrum
derived from weak lensing distortions of field galaxies as a function of
redshift will provide independent and complementary constraints on the dark
energy equation of state. The combination of SN and WL is much more powerful
than either technique on its own. Used together, these surveys will have more
than an order of magnitude greater sensitivity than will be provided by ongoing
ground-based projects. The dark energy parameters, w_0 and w_a, will be
measured to a precision of 0.05 and 0.2 respectively.Comment: Contains full color figure
Fast and precise map-making for massively multi-detector CMB experiments
Future cosmic microwave background (CMB) polarisation experiments aim to
measure an unprecedentedly small signal - the primordial gravity wave component
of the polarisation field B-mode. To achieve this, they will analyse huge
datasets, involving years worth of time-ordered data (TOD) from massively
multi-detector focal planes. This creates the need for fast and precise methods
to complement the M-L approach in analysis pipelines. In this paper, we
investigate fast map-making methods as applied to long duration, massively
multi-detector, ground-based experiments, in the context of the search for
B-modes. We focus on two alternative map-making approaches: destriping and TOD
filtering, comparing their performance on simulated multi-detector polarisation
data. We have written an optimised, parallel destriping code, the DEStriping
CARTographer DESCART, that is generalised for massive focal planes, including
the potential effect of cross-correlated TOD 1/f noise. We also determine the
scaling of computing time for destriping as applied to a simulated full-season
data-set for a realistic experiment. We find that destriping can out-perform
filtering in estimating both the large-scale E and B-mode angular power
spectra. In particular, filtering can produce significant spurious B-mode power
via EB mixing. Whilst this can be removed, it contributes to the variance of
B-mode bandpower estimates at scales near the primordial B-mode peak. For the
experimental configuration we simulate, this has an effect on the possible
detection significance for primordial B-modes. Destriping is a viable
alternative fast method to the full M-L approach that does not cause the
problems associated with filtering, and is flexible enough to fit into both M-L
and Monte-Carlo pseudo-Cl pipelines.Comment: 16 pages, 14 figures. MNRAS accepted. Typos corrected and computing
time/memory requirement orders-of-magnitude numbers in section 4 replaced by
precise number
Exploring the NRO Opportunity for a Hubble-sized Wide-field Near-IR Space Telescope -- NEW WFIRST
We discuss scientific, technical and programmatic issues related to the use
of an NRO 2.4m telescope for the WFIRST initiative of the 2010 Decadal Survey.
We show that this implementation of WFIRST, which we call "NEW WFIRST," would
achieve the goals of the NWNH Decadal Survey for the WFIRST core programs of
Dark Energy and Microlensing Planet Finding, with the crucial benefit of deeper
and/or wider near-IR surveys for GO science and a potentially Hubble-like Guest
Observer program. NEW WFIRST could also include a coronagraphic imager for
direct detection of dust disks and planets around neighboring stars, a
high-priority science and technology precursor for future ambitious programs to
image Earth-like planets around neighboring stars.Comment: 76 pages, 26 figures -- associated with the Princeton "New Telescope
Meeting
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