795 research outputs found
Alternative Linear Chiral Models for Nuclear Matter
The equation of state of a family of alternative linear chiral models in the
mean field approximation is discussed. We investigate the analogy between some
of these models with current models in the literature, and we show that it is
possible to reproduce very well the saturation properties of nuclear matter.Comment: 11 pages in Latex, 4 ps figures include
Design of a SiPM-based cluster for the Large Size Telescope camera of CTA
A Silicon Photomultiplier (SiPM)-based photodetector is being built to
demonstrate its feasibility for an alternative silicon-based camera design for
the Large Size Telescope (LST) of the Cherenkov Telescope Array. It has been
designed to match the size of the standard Photomultiplier Tube (PMT) cluster
unit and to be compatible with mechanics, electronics and focal plane optics of
the first LST camera. Here, we describe the overall SiPM cluster design along
with the main differences with respect to the currently used PMT cluster unit.
The fast electronics of the SiPM pixel and its layout are also presented. In
order to derive the best working condition for the final unit, we measured the
SiPM performances in terms of gain, photo-detection efficiency and cross-talk.
One pixel, a unit of 14 SiPMs, has been built. We will discuss also some
preliminary results regarding this device and we will highlight the future
steps of this project.Comment: submitted to NIM
DigiCam - Fully Digital Compact Read-out and Trigger Electronics for the SST-1M Telescope proposed for the Cherenkov Telescope Array
The SST-1M is one of three prototype small-sized telescope designs proposed
for the Cherenkov Telescope Array, and is built by a consortium of Polish and
Swiss institutions. The SST-1M will operate with DigiCam - an innovative,
compact camera with fully digital read-out and trigger electronics. A high
level of integration will be achieved by massively deploying state-of-the-art
multi-gigabit transmission channels, beginning from the ADC flash converters,
through the internal data and trigger signals transmission over backplanes and
cables, to the camera's server link. Such an approach makes it possible to
design the camera to fit the size and weight requirements of the SST-1M
exactly, and provide low power consumption, high reliability and long lifetime.
The structure of the digital electronics will be presented, along with main
physical building blocks and the internal architecture of FPGA functional
subsystems.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
Using muon rings for the optical throughput calibration of the SST-1M prototype for the Cherenkov Telescope Array
Imaging Atmospheric Cherenkov Telescopes (IACTs) are ground-based instruments
devoted to the study of very high energy gamma-rays coming from space. The
detection technique consists of observing images created by the Cherenkov light
emitted when gamma rays, or more generally cosmic rays, propagate through the
atmosphere. While in the case of protons or gamma-rays the images present a
filled and more or less elongated shape, energetic muons penetrating the
atmosphere are visualised as characteristic circular rings or arcs. A
relatively simple analysis of the ring images allows the reconstruction of all
the relevant parameters of the detected muons, such as the energy, the impact
parameter, and the incoming direction, with the final aim to use them to
calibrate the total optical throughput of the given IACT telescope. We present
the results of preliminary studies on the use of images created by muons as
optical throughput calibrators of the single mirror small size telescope
prototype SST-1M proposed for the Cherenkov Telescope Array.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
Software design for the control system for Small-Size Telescopes with single-mirror of the Cherenkov Telescope Array
The Small-Size Telescope with single-mirror (SST-1M) is a 4 m Davies-Cotton
telescope and is among the proposed telescope designs for the Cherenkov
Telescope Array (CTA). It is conceived to provide the high-energy ( few TeV)
coverage. The SST-1M contains proven technology for the telescope structure and
innovative electronics and photosensors for the camera. Its design is meant to
be simple, low-budget and easy-to-build industrially.
Each device subsystem of an SST-1M telescope is made visible to CTA through a
dedicated industrial standard server. The software is being developed in
collaboration with the CTA Medium-Size Telescopes to ensure compatibility and
uniformity of the array control. Early operations of the SST-1M prototype will
be performed with a subset of the CTA central array control system based on the
Alma Common Software (ACS). The triggered event data are time stamped,
formatted and finally transmitted to the CTA data acquisition.
The software system developed to control the devices of an SST-1M telescope
is described, as well as the interface between the telescope abstraction to the
CTA central control and the data acquisition system.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
Prototype of the SST-1M Telescope Structure for the Cherenkov Telescope Array
A single-mirror small-size (SST-1M) Davies-Cotton telescope with a dish
diameter of 4 m has been built by a consortium of Polish and Swiss institutions
as a prototype for one of the proposed small-size telescopes for the southern
observatory of the Cherenkov Telescope Array (CTA). The design represents a
very simple, reliable, and cheap solution. The mechanical structure prototype
with its drive system is now being tested at the Institute of Nuclear Physics
PAS in Krakow. Here we present the design of the prototype and results of the
performance tests of the structure and the drive and control system.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
The SST-1M camera for the Cherenkov Telescope Array
The prototype camera of the single-mirror Small Size Telescopes (SST-1M)
proposed for the Cherenkov Telescope Array (CTA) project has been designed to
be very compact and to deliver high performance over thirty years of operation.
The camera is composed of an hexagonal photo-detection plane made of custom
designed large area hexagonal silicon photomultipliers and a high throughput,
highly configurable, fully digital readout and trigger system (DigiCam). The
camera will be installed on the telescope structure at the H.
Niewodnicza{\'n}ski institute of Nuclear Physics in Krakow in fall 2015. In
this contribution, we review the steps that led to the development of the
innovative photo-detection plane and readout electronics, and we describe the
test and calibration strategy adopted.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.05894; Full consortium author list at http://cta-observatory.or
MAGIC upper limits on the very high energy emission from GRBs
The fast repositioning system of the MAGIC Telescope has allowed during its
first data cycle, between 2005 and the beginning of year 2006, observing nine
different GRBs as possible sources of very high energy gammas. These
observations were triggered by alerts from Swift, HETE-II, and Integral; they
started as fast as possible after the alerts and lasted for several minutes,
with an energy threshold varying between 80 and 200 GeV, depending upon the
zenith angle of the burst. No evidence for gamma signals was found, and upper
limits for the flux were derived for all events, using the standard analysis
chain of MAGIC. For the bursts with measured redshift, the upper limits are
compatible with a power law extrapolation, when the intrinsic fluxes are
evaluated taking into account the attenuation due to the scattering in the
Metagalactic Radiation Field (MRF).Comment: 25 pages, 9 figures, final version accepted by ApJ. Changet title to
"MAGIC upped limits on the VERY high energy emission from GRBs", re-organized
chapter with description of observation, removed non necessaries figures,
added plot of effective area depending on zenith angle, added an appendix
explaining the upper limit calculation, added some reference
Systematic search for VHE gamma-ray emission from X-ray bright high-frequency BL Lac objects
All but three (M87, BL Lac and 3C 279) extragalactic sources detected so far
at very high energy (VHE) gamma-rays belong to the class of high-frequency
peaked BL Lac (HBL) objects. This suggested to us a systematic scan of
candidate sources with the MAGIC telescope, based on the compilation of X-ray
blazars by Donato et al. (2001). The observations took place from December 2004
to March 2006 and cover sources on the northern sky visible under small zenith
distances zd < 30 degrees at culmination. The sensitivity of the search was
planned for detecting X-ray bright F(1 keV) > 2 uJy) sources emitting at least
the same energy flux at 200 GeV as at 1 keV. In order to avoid strong gamma-ray
attenuation close to the energy threshold, the redshift of the sources was
constrained to values z<0.3. Of the fourteen sources observed, 1ES 1218+304 and
1ES 2344+514 have been detected in addition to the known bright TeV blazars Mrk
421 and Mrk 501. A marginal excess of 3.5 sigma from the position of 1ES
1011+496 was observed and has been confirmed as a source of VHE gamma-rays by a
second MAGIC observation triggered by a high optical state (Albert et al.
2007). For the remaining sources, we present here the 99% confidence level
upper limits on the integral flux above ~200 GeV. We characterize the sample of
HBLs (including all HBLs detected at VHE so far) by looking for correlations
between their multi-frequency spectral indices determined from simultaneous
optical, archival X-ray, and radio luminosities, finding that the VHE emitting
HBLs do not seem to constitute a unique subclass. The absorption corrected
gamma-ray luminosities at 200 GeV of the HBLs are generally not higher than
their X-ray luminosities at 1 keV.Comment: 15 pages, 7 figures, 5 tables, submitted to ApJ (revised version
MAGIC observations of very high energy gamma-rays from HESS J1813-178
Recently, the HESS collaboration has reported the detection of gamma-ray
emission above a few hundred GeV from eight new sources located close to the
Galactic Plane. The source HESS J1813-178 has sparked particular interest, as
subsequent radio observations imply an association with SNR G12.82-0.02.
Triggered by the detection in VHE gamma-rays, a positionally coincident source
has also been found in INTEGRAL and ASCA data. In this Letter we present MAGIC
observations of HESS J1813-178, resulting in the detection of a differential
gamma-ray flux consistent with a hard-slope power law, described as dN/(dA dt
dE) = (3.3+/-0.5)*10^{-12} (E/TeV)^{-2.1+/-0.2} cm^(-2)s^(-1)TeV^(-1). We
briefly discuss the observational technique used, the procedure implemented for
the data analysis, and put this detection in the perspective of multifrequency
observations.Comment: Accepted by ApJ Letter
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