X-ray polarimetry promises to give qualitatively new information about high-energy astrophysical sources, such as binary black hole systems, micro-quasars, active galactic nuclei, neutron stars, and ...gamma-ray bursts. We designed, built and tested a X-ray polarimeter, X-Calibur, to be used in the focal plane of the balloon-borne InFOCuS grazing incidence X-ray telescope. X-Calibur combines a low-Z scatterer with a CZT detector assembly to measure the polarization of 20-80keV X-rays making use of the fact that polarized photons scatter preferentially perpendicular to the electric field orientation. X-Calibur achieves a high detection efficiency of ~80%. The X-Calibur detector assembly is completed, tested, and fully calibrated. The response to a polarized X-ray beam was measured successfully at the Cornell High Energy Synchrotron Source. This paper describes the design, calibration and performance of the X-Calibur polarimeter. In principle, a similar space-borne scattering polarimeter could operate over the broader 2-100keV energy band.
Phys.Rev.Lett.96:171101,2006 We report new limits on cosmic neutrino fluxes from the test flight of the
Antarctic Impulsive Transient Antenna (ANITA) experiment, which completed an
18.4 day flight of ...a prototype long-duration balloon payload, called
ANITA-lite, in early 2004. We search for impulsive events that could be
associated with ultra-high energy neutrino interactions in the ice, and derive
limits that constrain several models for ultra-high energy neutrino fluxes. We
rule out the long-standing Z-burst model as the source for the ultra-high
energy cosmic rays.
Phys.Rev.Lett.99:171101,2007 We report on the first observations of the Askaryan effect in ice: coherent
impulsive radio Cherenkov radiation from the charge asymmetry in an
electromagnetic (EM) ...shower. Such radiation has been observed in silica sand
and rock salt, but this is the first direct observation from an EM shower in
ice. These measurements are important since the majority of experiments to date
that rely on the effect for ultra-high energy neutrino detection are being
performed using ice as the target medium. As part of the complete validation
process for the Antarctic Impulsive Transient Antenna (ANITA) experiment, we
performed an experiment at the Stanford Linear Accelerator Center (SLAC) in
June 2006 using a 7.5 metric ton ice target, yielding results fully consistent
with theoretical expectations.
ECONF C041213:2516,2004 The Antarctic Impulsive Transient Antenna (ANITA) experiment is being
developed to search for ultra-high-energy (UHE) neutrino interactions
($>3\times10^{18}$ eV) in the ...Antarctic ice cap. A neutrino interaction in the
ice will produce a radio pulse by the means of the Askaryan effect. The large
radio transparency of ice allows for such a pulse to be recorded by a cluster
of balloon-borne antennas. The details of the ANITA instrument, now in a
construction phase, and the science we hope to achieve is discussed. In order
to prepare for the main mission, we have flown ANITA-lite during the 2003/04
austral season. ANITA-lite consisted of two quad-ridge horn antennas and a
prototype RF (radio frequency) triggering and recording system. Here we present
the results of an impulsive RF background survey of Antarctica, as well as
proof-of-principle gain, tracking, and timing calibrations conducted by
observing solar radio emissions and calibration radio-pulses. A preliminary UHE
neutrino flux limit based on ANITA-lite data is also presented.
NATO Sci.Ser.II 209:297-306,2005 We describe a new experiment to search for neutrinos with energies above 3 x
10^18 eV based on the observation of short duration radio pulses that are
emitted from ...neutrino-initiated cascades. The primary objective of the
ANtarctic Impulse Transient Antenna (ANITA) mission is to measure the flux of
Greisen-Zatsepin-Kuzmin (GZK) neutrinos and search for neutrinos from Active
Galactic Nuclei (AGN). We present first results obtained from the successful
launch of a 2-antenna prototype instrument (called ANITA-lite) that circled
Antarctica for 18 days during the 03/04 Antarctic campaign and show preliminary
results from attenuation length studies of electromagnetic waves at radio
frequencies in Antarctic ice. The ANITA detector is funded by NASA, and the
first flight is scheduled for December 2006.
Radiowave detection of the Cherenkov radiation produced by neutrino-ice collisions requires an understanding of the radiofrequency (RF) response of cold polar ice. We herein report on a series of ...radioglaciological measurements performed approximately 10 km north of Taylor Dome Station, Antarctica from Dec. 6, 2006 - Dec. 16, 2006. Using RF signals broadcast from: a) an englacial discone, submerged to a depth of 100 meters and broadcasting to a surface dual polarization horn receiver, and b) a dual-polarization horn antenna on the surface transmitting signals which reflect off the underlying bed and back up to the surface receiver, we have made time-domain estimates of both the real (index-of-refraction) and imaginary (attenuation length) components of the complex ice dielectric constant. We have also measured the uniformity of ice response along two orthogonal axes in the horizontal plane. We observe a wavespeed asymmetry of order 0.1%, projected onto the vertical propagation axis, consistent with some previous measurements, but somewhat lower than others.
We report new limits on cosmic neutrino fluxes from the test flight of the Antarctic Impulsive Transient Antenna (ANITA) experiment, which completed an 18.4 day flight of a prototype long-duration ...balloon payload, called ANITA-lite, in early 2004. We search for impulsive events that could be associated with ultra-high energy neutrino interactions in the ice, and derive limits that constrain several models for ultra-high energy neutrino fluxes. We rule out the long-standing Z-burst model as the source for the ultra-high energy cosmic rays.
We report on the first observations of the Askaryan effect in ice: coherent impulsive radio Cherenkov radiation from the charge asymmetry in an electromagnetic (EM) shower. Such radiation has been ...observed in silica sand and rock salt, but this is the first direct observation from an EM shower in ice. These measurements are important since the majority of experiments to date that rely on the effect for ultra-high energy neutrino detection are being performed using ice as the target medium. As part of the complete validation process for the Antarctic Impulsive Transient Antenna (ANITA) experiment, we performed an experiment at the Stanford Linear Accelerator Center (SLAC) in June 2006 using a 7.5 metric ton ice target, yielding results fully consistent with theoretical expectations.
We describe a new experiment to search for neutrinos with energies above 3 x 10^18 eV based on the observation of short duration radio pulses that are emitted from neutrino-initiated cascades. The ...primary objective of the ANtarctic Impulse Transient Antenna (ANITA) mission is to measure the flux of Greisen-Zatsepin-Kuzmin (GZK) neutrinos and search for neutrinos from Active Galactic Nuclei (AGN). We present first results obtained from the successful launch of a 2-antenna prototype instrument (called ANITA-lite) that circled Antarctica for 18 days during the 03/04 Antarctic campaign and show preliminary results from attenuation length studies of electromagnetic waves at radio frequencies in Antarctic ice. The ANITA detector is funded by NASA, and the first flight is scheduled for December 2006.
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