P. Assis

Autonomous RPCs for a Cosmic Ray ground array

We report on the behaviour of Resistive Plate Chambers (RPC) developed for muon detection in ultra-high energy cosmic ray (UHECR) experiments. The RPCs were developed for the MARTA project and were tested on field conditions. These RPCs cover an area of

MARTA: a high-energy cosmic-ray detector concept for high-accuracy muon measurement

1.5 \times 1.2\,{m^2}

LATTES: a novel detector concept for a gamma-ray experiment in the Southern hemisphere

and are instrumented with 64 pickup electrodes providing a segmentation better than

Solar panels as cosmic-ray detectors

20\,

FAMOUS: a prototype silicon-photomultiplier telescope for the fluorescence detection of ultra-high-energy cosmic rays

cm. By shielding the detector units with enough slant mass to absorb the electromagnetic component in the air showers, a clean measurement of the muon content is allowed, a concept to be implemented in a next generation of UHECR experiments. The operation of a ground array detector poses challenging demands, as the RPC must operate remotely under extreme environmental conditions, with limited budgets for power and minimal maintenance. The RPC, DAQ, High Voltage and monitoring systems are enclosed in an aluminium-sealed case, providing a compact and robust unit suited for outdoor environments, which can be easily deployed and connected. The RPCs developed at LIP-Coimbra are able to operate using a very low gas flux, which allows running them for few years with a small gas reservoir. Several prototypes have already been built and tested both in the laboratory and outdoors. We report on the most recent tests done in the field that show that the developed RPCs have operated in a stable way for more than 2 years in field conditions.

Characteristics and Performance of the GAW Experiment for a Large Field of View Cerenkov Gamma-ray Telescope

A new concept for the direct measurement of muons in air showers is presented. The concept is based on resistive plate chambers (RPCs), which can directly measure muons with very good space and time resolution. The muon detector is shielded by placing it under another detector able to absorb and measure the electromagnetic component of the showers such as a water-Cherenkov detector, commonly used in air shower arrays. The combination of the two detectors in a single, compact detector unit provides a unique measurement that opens rich possibilities in the study of air showers.

DIFFUSED ČERENKOV LIGHT MEASUREMENTS FOR THE EUSO PROJECT

The Large Array Telescope for Tracking Energetic Sources (LATTES), is a novel concept for an array of hybrid EAS array detectors, composed of a Resistive Plate Counter array coupled to a Water Cherenkov Detector, planned to cover gamma rays from less than 100 GeV up to 100 TeVs. This experiment, to be installed at high altitude in South America, could cover the existing gap in sensitivity between satellite and ground arrays. The low energy threshold, large duty cycle and wide field of view of LATTES makes it a powerful tool to detect transient phenomena and perform long term observations of variable sources. Moreover, given its characteristics, it would be fully complementary to the planned Cherenkov Telescope Array (CTA) as it would be able to issue alerts. In this talk, a description of its main features and capabilities, as well as results on its expected performance, and sensitivity, will be presented.

Status of the Silicon Photomultiplier Telescope FAMOUS for the Fluorescence Detection of UHECRs

Due to fundamental limitations of accelerators, only cosmic rays can give access to centre-of- mass energies more than one order of magnitude above those reached at the LHC. In fact, extreme energy cosmic rays (1018 eV - 1020 eV) are the only possibility to explore the 100 TeV energy scale in the years to come. This leap by one order of magnitude gives a unique way to open new horizons: new families of particles, new physics scales, in-depth investigations of the Lorentz symmetries. However, the flux of cosmic rays decreases rapidly, being less than one particle per square kilometer per year above 1019 eV: one needs to sample large surfaces. A way to develop large-effective area, low cost, detectors, is to build a solar panel-based device which can be used in parallel for power generation and Cherenkov light detection. Using solar panels for Cherenkov light detection would combine power generation and a non-standard detection device.

Measurements of the UV Nocturnal Atmospheric Background in the 300-400 nm Wavelength Band with the Experiment BaBy during a Transmediterranean Balloon Flight

A sophisticated technique to study ultra-high-energy cosmic rays is to measure the extensive air showers they cause in the atmosphere. Upon impact on the atmosphere, the cosmic rays generate a cascade of secondary particles, forming the air shower. The shower particles excite the atmospheric nitrogen molecules, which emit fluorescence light in the near ultraviolet regime when de-exciting. Observation of the fluorescence light with suitable optical telescopes allows a reconstruction of the energy and arrival direction of the initial particle. Due to their high photon detection efficiency, silicon photomultipliers (SiPMs) promise to improve current photomultipliertube- based fluorescence telescopes. We present the design and a full detector simulation of an SiPM-based fluorescence telescope prototype, together with the expected telescope performance, and our first construction steps. The simulation includes the air showers, the propagation of the fluorescence light through the atmosphere and its detection by our refracting telescope. We have also developed a phenomenological SiPM model based on measurements in our laboratories, simulating the electrical response. This model contains the photon detection efficiency, its dependence on the incidence angle of light and the effects of thermal and correlated noise. We have made a full performance analysis for the detection of air showers including the environmental background light. Moreover, we will present the RandD in compact modular electronics using photon counting techniques for the telescope readout.

Extensive air showers and diffused Cherenkov light detection: The ULTRA experiment

One of the intents of the ground-based gamma-ray astronomy is to obtain a sky survey in the TeV energy region, and nowadays this target can be reached with giant arrays of telescopes, which however need many pointings due to their small field of view. A different approach is on the basis of GAW, acronym for Gamma Air Watch, an array of three relatively small Cerenkov telescopes which differentiate from the existing and presently planned telescopes for two main features: the adoption of a refractive optics system as light collector with a large field of view capability, and the use of single photoelectron counting as detector working mode. During a first phase, the focal plane detector of the GAW telescopes will be implemented in a reduced configuration to test the sensitivity and to prove the feasibility of the method; then the focal plane will be enlarged to cover a field of view of 24°×24°; pointing along different North-South directions, GAW would reach a survey of 360°×60° region of the sky. In this paper, the GAW expected performance are reported as evaluated in the case of the Calar Alto site, Spain, 2150 m a.s.l., where GAW is planned to be located within 2007. GAW is a collaboration effort of Research Institutes in Italy, Portugal and Spain.