1,126 research outputs found
A new solution for mirror coating in -ray Cherenkov Astronomy
In the -ray Cherenkov Astronomy framework mirror coating plays a
crucial role in defining the light response of the telescope. We carried out a
study for new mirror coating solutions with both a numerical simulation
software and a vacuum chamber for small sample production. In this article, we
present a new mirror coating solution consisting of a 28-layer interferometric
SiO-TiO-HfO design deposited on a glass substrate, whose
average reflectance is above for normally incident light in the
wavelength range between 300 and 550 nm.Comment: 6 pages, 5 figures. Article submitted to Experimental Astronomy, the
final publication is available at link.springer.co
The Mirror Alignment and Control System for CT5 of the H.E.S.S. experiment
The High Energy Stereoscopic System (H.E.S.S.) experiment is one of the
largest observatories for gamma-ray astronomy. It consists of four telescopes
with a reflecting dish diameter of 12m (CT1 to CT4) and a newer large telescope
(CT5) with a reflecting dish diameter of 28m. On CT5 876 mirror facets are
mounted, all of them equipped with a computerised system for their alignment.
The design of the mirror alignment and control system and the performance of
the hardware installed to the telescope are presented. Furthermore the achieved
point spread function of the telescope over the full operational elevation
range as well as the stability of the alignment over an extended period of time
are shown
System-size dependence of strangeness production in high-energy A+A collisions and percolation of strings
We argue that the shape of the system-size dependence of strangeness production in nucleus-nucleus collisions can be understood in a picture that is based on the formation of clusters of overlapping strings. A string percolation model combined with a statistical description of the hadronization yields a quantitative agreement with the data at sqrt s_NN = 17.3 GeV. The model is also applied to RHIC energies
Impact of atmospheric parameters on the atmospheric Cherenkov technique
Atmospheric density profiles as well as several light absorption and
scattering processes depend on geographic position and are generally
time-variable. Their impact on the atmospheric Cherenkov technique in general
(imaging or non-imaging) is investigated. Different density profiles lead to
differences in Cherenkov light density of up to 60%. Seasonal variations at
mid-latitude sites are of the order of 15-20%. The quest for improved energy
calibration of Cherenkov experiments also shows the need for improved
transmission calculations, taking all relevant processes into account and using
realistic profiles of absorbers. Simulations including the scattering
mechanisms also reveal the relevance of Rayleigh and Mie scattering for
atmospheric Cherenkov experiments. Refraction and the differences between
treating the atmosphere in plane-parallel or spherical geometry are also
investigated.Comment: 23 pages, 15 figures. Accepted by Astroparticle Physic
X- and gamma-ray studies of HESS J1731-347 coincident with a newly discovered SNR
In the survey of the Galactic plane conducted with H.E.S.S., many VHE
gamma-ray sources were discovered for which no clear counterpart at other
wavelengths could be identified. HESS J1731-347 initially belonged to this
source class. Recently however, the new shell-type supernova remnant (SNR)
G353.6-0.7 was discovered in radio data, positionally coinciding with the VHE
source. We will present new X-ray observations that cover a fraction of the VHE
source, revealing nonthermal emission that most likely can be interpreted as
synchrotron emission from high-energy electrons. This, along with a larger
H.E.S.S. data set which comprises more than twice the observation time used in
the discovery paper, allows us to test whether the VHE source may indeed be
attributed to shell-type emission from that new SNR. If true, this would make
HESS J1731-347 a new object in the small but growing class of non-thermal
shell-type supernova remnants with VHE emission.Comment: 4 pages, 5 figures, to appear in proceedings of the 31st ICRC, Lodz,
Polan
- …