973 research outputs found
First optical validation of a Schwarzschild Couder telescope: the ASTRI SST-2M Cherenkov telescope
The Cherenkov Telescope Array (CTA) represents the most advanced facility
designed for Cherenkov Astronomy. ASTRI SST-2M has been developed as a
demonstrator for the Small Size Telescope in the context of the upcoming CTA.
Its main innovation consists in the optical layout which implements the
Schwarzschild-Couder configuration and is fully validated for the first time.
The ASTRI SST-2M optical system represents the first qualified example for two
mirrors telescope for Cherenkov Astronomy.
This configuration permits to (i) maintain a high optical quality across a
large FoV (ii) de-magnify the plate scale, (iii) exploit new technological
solutions for focal plane sensors. The goal of the paper is to present the
optical qualification of the ASTRI SST-2M telescope. The qualification has been
obtained measuring the PSF sizes generated in the focal plane at various
distance from the optical axis. These values have been compared with the
performances expected by design.
After an introduction on the Gamma Astronomy from the ground, the optical
design and how it has been implemented for ASTRI SST-2M is discussed. Moreover
the description of the setup used to qualify the telescope over the full field
of view is shown.
We report the results of the first--light optical qualification. The required
specification of a flat PSF of arcmin in a large field of view ~10
deg has been demonstrated. These results validate the design specifications,
opening a new scenario for Cherenkov Gamma ray Astronomy and, in particular,
for the detection of high energy (5 - 300 TeV) gamma rays and wide-field
observations with CTA.Comment: 6 pages, 5 figure
Pt-Sn/C as a possible methanol-tolerant cathode catalyst for DMFC
An effective method was developed for preparing highly dispersed nano-sized PtâSn/C electrocatalyst synthesised by a modified polyol reduction method. From XRD patterns, the PtâSn/C peaks shifted slightly to lower 2Ξ angles when compared with commercial Pt/C catalyst, suggesting that Sn formed alloy with Pt. Based on HR-TEM images, the PtâSn/C nanoparticles showed small particle sizes and well dispersed onto the carbon support with a narrow particle distribution. The methanol oxidation reaction on the as-prepared PtâSn/C catalyst appeared at lower currents (+7.08 mA at +480 mV vs. Ag/AgCl) compared to the commercial Pt/C (+8.25 mA at +480 mV vs. Ag/AgCl) suggesting that the PtâSn/C catalyst has âmethanol tolerance capabilitiesâ. PtâSn/C HA Slurry pH3 catalysts showed better activity towards the oxygen-reduction reaction (ORR) than commercial Pt/C which could be attributed to smaller particle sizes. In our study, the PtâSn/C catalyst appears to be a promising methanol-tolerant catalyst with activity towards the ORR in the DMFC.Web of Scienc
Search for massive rare particles with MACRO
Massive rare particles have been searched for in the penetrating cosmic
radiation using the MACRO apparatus at the Gran Sasso National Laboratories.
Liquid scintillators, streamer tubes and nuclear track detectors have been used
to search for magnetic monopoles (MMs).
Based on no observation of such signals, stringent flux limits are
established for MMs as slow as a few 10^(-5)c. The methods based on the
scintillator and on the nuclear track subdetectors were also applied to search
for nuclearites. Preliminary results of the searches for charged Q-balls are
also presented.Comment: 20 pages, 9 EPS figures included with epsfi
The Observation of Up-going Charged Particles Produced by High Energy Muons in Underground Detectors
An experimental study of the production of up-going charged particles in
inelastic interactions of down-going underground muons is reported, using data
obtained from the MACRO detector at the Gran Sasso Laboratory. In a sample of
12.2 10^6 single muons, corresponding to a detector livetime of 1.55 y, 243
events are observed having an up-going particle associated with a down-going
muon. These events are analysed to determine the range and emission angle
distributions of the up-going particle, corrected for detection and
reconstruction efficiency. Measurements of the muon neutrino flux by
underground detectors are often based on the observation of through-going and
stopping muons produced in interactions in the rock below the
detector. Up-going particles produced by an undetected down-going muon are a
potential background source in these measurements. The implications of this
background for neutrino studies using MACRO are discussed.Comment: 18 pages, 9 figures. Accepted by Astrop. Physic
Limits on dark matter WIMPs using upward-going muons in the MACRO detector
We perform an indirect search for Weakly Interacting Massive Particles
(WIMPs) using the MACRO detector to look for neutrino-induced upward-going
muons resulting from the annihilation of WIMPs trapped in the Sun and Earth.
The search is conducted in various angular cones centered on the Sun and Earth
to accommodate a range of WIMP masses. No significant excess over the
background from atmospheric neutrinos is seen and limits are placed on the
upward-going muon fluxes from Sun and Earth. These limits are used to constrain
neutralino particle parameters from supersymmetric theory, including those
suggested by recent results from DAMA/NaI.Comment: 14 pages, 7 figures, submitted to Phys. Rev.
Search for Nucleon Decays induced by GUT Magnetic Monopoles with the MACRO Experiment
The interaction of a Grand Unification Magnetic Monopole with a nucleon can
lead to a barion-number violating process in which the nucleon decays into a
lepton and one or more mesons (catalysis of nucleon decay). In this paper we
report an experimental study of the effects of a catalysis process in the MACRO
detector. Using a dedicated analysis we obtain new magnetic monopole (MM) flux
upper limits at the level of for
, based on the search for
catalysis events in the MACRO data. We also analyze the dependence of the MM
flux limit on the catalysis cross section.Comment: 12 pages, Latex, 10 figures and 2 Table
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