83 research outputs found
Estimate of the impact of background particles on the X-Ray Microcalorimeter Spectrometer on IXO
We present the results of a study on the impact of particles of galactic
(GCR) and solar origin for the X-ray Microcalorimeter Spectrometer (XMS) aboard
an astronomical satellite flying in an orbit at the second Lagrangian point
(L2). The detailed configuration presented in this paper is the one adopted for
the International X-Ray Observatory (IXO) study, however the derived estimates
can be considered a conservative limit for ATHENA, that is the IXO redefined
mission proposed to ESA. This work is aimed at the estimate of the residual
background level expected on the focal plane detector during the mission
lifetime, a crucial information in the development of any instrumental
configuration that optimizes the XMS scientific performances. We used the
Geant4 toolkit, a Monte Carlo based simulator, to investigate the rejection
efficiency of the anticoincidence system and assess the residual background on
the detector.Comment: 18 pages, 9 figure
An iterative destriping technique for diffuse background polarization data
We describe a simple but effective iterative procedure specifically designed
to destripe Q and U Stokes parameter data as those collected by the SPOrt
experiment onboard the International Space Station (ISS). The method is general
enough to be useful for other experiments, both in polarization and total
intensity. The only requirement for the algorithm to work properly is that the
receiver knee frequency must be lower than the signal modulation frequency,
corresponding in our case to the ISS orbit period. Detailed performances of the
technique are presented in the context of the SPOrt experiment, both in terms
of added rms noise and residual correlated noise.Comment: Accepted for publication by A&A (8 pages, 6 figures
Effects of Thermal Fluctuations in the SPOrt Experiment
The role of systematic errors induced by thermal fluctuations is analyzed for
the SPOrt experiment with the aim at estimating their impact on the measurement
of the Cosmic Microwave Background Polarization (CMBP). The transfer functions
of the antenna devices from temperature to data fluctuations are computed, by
writing them in terms of both instrument and thermal environment parameters. In
addition, the corresponding contamination maps are estimated, along with their
polarized power spectra, for different behaviours of the instabilities. The
result is that thermal effects are at a negligible level even for fluctuations
correlated with the Sun illumination provided their frequency is
larger than that of the Sun illumination () by a factor , which defines a requirement for the statistical properties of
the temperature behaviour as well. The analysis with actual SPOrt operative
parameters shows that the instrument is only weakly sensitive to temperature
instabilities, the main contribution coming from the cryogenic stage. The
contamination on the E-mode spectrum does not significantly pollute the CMBP
signal and no specific data cleaning seems to be needed.Comment: 12 pages, 11 figures. Accepted for publication in A&
In-orbit background of X-ray microcalorimeters and its effects on observations
Methods.There are no experimental data about the background experienced by
microcalorimeters in the L2 orbit, and thus the particle background levels were
calculated by means of Monte Carlo simulations: we considered the original
design configuration and an improved configuration aimed to reduce the
unrejected background, and tested them in the L2 orbit and in the low Earth
orbit, comparing the results with experimental data reported by other X-ray
instruments.To show the results obtainable with the improved configuration we
simulated the observation of a faint, high-redshift, point source (F[0.5-10
keV]~6.4E-16 erg cm-2 s-1, z=3.7), and of a hot galaxy cluster at R200
(Sb[0.5-2 keV]=8.61E-16 erg cm-2 s-1 arcmin-2,T=6.6 keV). Results.First we
confirm that implementing an active cryogenic anticoincidence reduces the
particle background by an order of magnitude and brings it close to the
required level.The implementation and test of several design solutions can
reduce the particle background level by a further factor of 6 with respect to
the original configuration.The best background level achievable in the L2 orbit
with the implementation of ad-hoc passive shielding for secondary particles is
similar to that measured in the more favorable LEO environment without the
passive shielding, allowing us to exploit the advantages of the L2 orbit.We
define a reference model for the diffuse background and collect all the
available information on its variation with epoch and pointing direction.With
this background level the ATHENA mission with the X-IFU instrument is able to
detect ~4100 new obscured AGNs with F>6.4E-16 erg cm-2 s-1 during three years,
to characterize cluster of galaxies with Sb(0.5-2 keV)>9.4E-16 erg cm-2 s-1
sr-1 on timescales of 50 ks (500 ks) with errors <40% (<12%) on
metallicity,<16% (4.8%) on temperature,2.6% (0.72%) on the gas density, and
several single-element abundances.Comment: the PDF has poor quality, it will be improved in the futur
Monte-Carlo Simulations of the Suzaku-XRS Residual Background Spectrum
Cryogenic micro-calorimeters are suitable to detect small amounts of energy deposited by electromagnetic and nuclear interactions, which makes them attractive in a variety of applications on ground and in space. The only X-ray microcalorimeter that operated in orbit to date is the X-Ray Spectrometer on-board of the Japanese Suzaku satellite. We discuss the analysis of the components of its residual background spectrum with the support of Monte-Carlo simulations
The BaR-SPOrt Experiment
BaR-SPOrt (Balloon-borne Radiometers for Sky Polarisation Observations) is an
experiment to measure the linearly polarized emission of sky patches at 32 and
90 GHz with sub-degree angular resolution. It is equipped with high sensitivity
correlation polarimeters for simultaneous detection of both the U and Q stokes
parameters of the incident radiation. On-axis telescope is used to observe
angular scales where the expected polarization of the Cosmic Microwave
Background (CMBP) peaks. This project shares most of the know-how and
sophisticated technology developed for the SPOrt experiment onboard the
International Space Station. The payload is designed to flight onboard long
duration stratospheric balloons both in the Northern and Southern hemispheres
where low foreground emission sky patches are accessible. Due to the weakness
of the expected CMBP signal (in the range of microK), much care has been spent
to optimize the instrument design with respect to the systematics generation,
observing time efficiency and long term stability. In this contribution we
present the instrument design, and first tests on some components of the 32 GHz
radiometer.Comment: 12 pages, 10 figures, Astronomical Telescopes and Instrumentation
(Polaimetry in Astronomy) Hawaii August 2002 SPIE Meetin
The mechanical and EM simulations of the CryoAC for the ATHENA X-IFU
The design phase of the CryoAC DM for the ATHENA X-IFU has concerned numerical simulations to exploit different fabrication possibilities. The mechanical simulations have accounted for the peculiar detector structure: 4 silicon chips asymmetrically suspended by means of 4 microbridges each. A preliminary study was performed to analyze the response to acceleration spectra in the frequency domain, shocks and time domain random displacement, prior to a real vibration test campaign. EM simulations to spot unwanted magnetic fields have been conducted as well. In this work we will show the latest advance in the design of the new detectors, showing the main results coming from various simulations
The TES-based Cryogenic AntiCoincidence Detector (CryoAC) of ATHENA X-IFU: a large area silicon microcalorimeter for background particles detection
We are developing the Cryogenic AntiCoincidence detector (CryoAC) of the
ATHENA X-IFU spectrometer. It is a TES-based particle detector aimed to reduce
the background of the instrument. Here, we present the result obtained with the
last CryoAC single-pixel prototype. It is based on a 1 cm2 silicon absorber
sensed by a single 2mm x 1mm Ir/Au TES, featuring an on-chip heater for
calibration and diagnostic purposes. We have illuminated the sample with 55Fe
(6 keV line) and 241Am (60 keV line) radioactive sources, thus studying the
detector response and the heater calibration accuracy at low energy.
Furthermore, we have operated the sample in combination with a past-generation
CryoAC prototype. Here, by analyzing the coincident detections between the two
detectors, we have been able to characterize the background spectrum of the
laboratory environment and disentangle the primary (i.e. cosmic muons) and
secondaries (mostly secondary photons and electrons) signatures in the spectral
shape.Comment: Accepted for publication in the Journal of Low Temperature Physics
for LTD-20 special issu
SPOrt: an Experiment Aimed at Measuring the Large Scale Cosmic Microwave Background Polarization
SPOrt (Sky Polarization Observatory) is a space experiment to be flown on the
International Space Station during Early Utilization Phase aimed at measuring
the microwave polarized emission with FWHM = 7deg, in the frequency range 22-90
GHz. The Galactic polarized emission can be observed at the lower frequencies
and the polarization of Cosmic Microwave Background (CMB) at 90 GHz, where
contaminants are expected to be less important. The extremely low level of the
CMB Polarization signal (< 1 uK) calls for intrinsically stable radiometers.
The SPOrt instrument is expressly devoted to CMB polarization measurements and
the whole design has been optimized for minimizing instrumental polarization
effects. In this contribution we present the receiver architecture based on
correlation techniques, the analysis showing its intrinsic stability and the
custom hardware development carried out to detect such a low signal.Comment: 9 pages, 5 figures, conference proceeding, to appear in "Polarimetry
in Astronomy", SPIE Symposium on 'Astronomical Telescopes and
Instrumentation', Waikoloa, August 22-28 200
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