[en] VERITAS is an array of four 12-m imaging atmospheric Cherenkov telescopes operated by an international collaboration in Arizona for the study of very high-energy (VHE, E>100GeV) gamma rays. The array has been in regular operation since 2007 and was recently reconfigured to improve the sensitivity and resolution. Here we give a brief update on the performance of the instrument, and highlight several recent results from our program of observation of galactic and extragalactic sources, as well as from our indirect searches for dark-matter annihilation.

[en] The CAT imaging telescope is sensitive to the Cherenkov light emitted in the atmosphere and thus it is sensitive to a substantial flux of hard muons (E ≥ 5 GeV). A detailed study of these events will help to both calibrate the instrument and to understand the background that they represent in the search for gamma-ray showers. Resorting to simulated events the paper illustrates the use of the muon image reconstruction methods. This consist in fitting a circle on the pixels touched in the chamber by taking into account the muon impact parameter and the dN/dφ. The fitting method contains a parameter r which is the ratio between the number of detected photoelectrons and the number expected from the ring geometry. Besides the effort devoted to the reconstruction procedures we have put into operation two muon detectors. Each of them is composed of a tightly sealed can containing two fast photomultipliers to detect the Cherenkov light locally emitted. A coincidence signal from the two fast photomultipliers indicates the passage of a particle with the threshold higher than the Cherenkov one and gives a signal which is recorded with the telescope data. One of the detectors is mounted on the imaging telescope while the other one is nearby and can be moved in order to catch different values of the ρ/R (the ratio of the distance separating the mirror center and the muon impact location to the mirror radius). Due to this data analysis we are now really able to study the amount of the collected light as well as the observed muon counting rate

[en] The Solenoid Detector Collaboration (SDC) has proposed to construct and operate a large, general-purpose, solenoidal detector that combines excellent charged particle detection, a hermetic, scintillator-based calorimeter and a large muon identification system. A principal component of the SDC detector is the outer tracker that provides precise momentum measurement of charged particles from a radius of 85 cm to 165 cm from the proton beam. The outer tracker front-end electronics capture and digitize the data it produces and a data collection circuit (DCC) collects this data and passes it to the SDC data acquisition (DAQ) system. The authors describe in this article the specifications and design of the outer tracker DCC

[en] The CAT imaging Cherenkov telescope has now been operational for nearly a year, and has collected data on a variety of astrophysical sources. This scanning telescope allows obtaining high quality images of the Cherenkov radiation originating from atmospheric showers. The main advantage of this chamber is its high pixel granularity amounting to 546 phototubes of 11 mm. The telescope is a reflector of Davies-Cotton type for which 90 spherical mirrors of 50 cm diameter and 12 m radius are installed onto a metallic rack. Two methods of data processing are described. The most spectacular results concerning the Crab nebula and active galactic nucleus Markarian 501 are presented. Presently the CAT scanning telescope is operating on a routine-base for source observations. The threshold of the device which is around 250 GeV will be determined in the near future with high accuracy and new point-like and extended sources will be analyzed following the next planned measuring runs

[en] The initial test phase of the CELESTE experiment operated from October 1996 to February 1997. Two groups of three heliostats were used to reflect Cherenkov photons onto two secondary mirrors in the central tower. Fast photomultipliers in the focal plane of these secondary mirrors each 'see' only a single heliostats, allowing six-fold coincidences. We have studied coincidence rates as a function of the heliostats pointing altitude and as a function of the phototube (i.e. heliostats) threshold in photoelectrons. Pulse shape analysis and the event triggering will be a critical point and originality of the experiment

[en] During the data taking run ending June 1, 1989, the CDF experiment took data at the Fermilab Tevatron anti p-p collider using a four-level trigger filtering scheme. The fourth level, level 3, used ACP(Fermilab's Advanced Computer Program)-designed VME processors executing algorithms written in Fortran. At the end of the run, level 3 was rejecting 70% of the events. (orig.)

[en] We describe the design and performance of the Solar Tower Atmospheric Cherenkov Effect Experiment detector in its initial configuration (STACEE-32). STACEE is a new ground-based gamma-ray detector using the atmospheric Cherenkov technique. In STACEE, the heliostats of a solar energy research array are used to collect and focus the Cherenkov photons produced in gamma-ray induced air showers. The large Cherenkov photon collection area of STACEE results in a gamma-ray energy threshold below that of previous detectors

[en] We discuss the architecture, operation, and performance of the Level 3 trigger used in the Fermilab CDF experiment in 1988-1989. This trigger used an on-line computer farm of 58 Motorola 68020 processors operating in parallel. The on-line programs were written mainly in Fortran and run in an environment similar to that used for off-line analysis. (orig.)

[en] The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a new low-threshold atmospheric Cherenkov detector, using heliostat mirrors at a solar research facility to achieve a large collection area for Cherenkov light. The newest version of this detector, STACEE-64, should run at a threshold of 70 GeV or lower. Possible science for STACEE-64 in this energy range includes the study of AGN, supernova remnants, the extragalactic UV background, and exotic dark matter

[en] The STACEE experiment is being developed to study very high energy astrophysical gamma rays between 50 and 500 GeV. During the last few years this previously unexplored region has received much attention due to the detection of sources up to about 10 GeV by the EGRET instrument on board the CGRO. However, the paucity of detected sources at ∼1 TeV indicates that fundamental processes working within these sources and/or in the intergalactic space are responsible for the cutoff in the photon spectra of the EGRET sources. The cutoff or the spectral change of these sources can be observed with ground-based Cherenkov detectors with a very low threshold. The use of large arrays of mirrors at solar power facilities is a promising way of lowering the threshold. Using this concept a series of tests were conducted at the National Solar Thermal Test Facility (NSTTF) at Sandia National Laboratories (Albuquerque, NM) with a full size prototype of the STACEE telescope system. The tests show that STACEE will be capable of meaningful exploration of the gamma-ray sky between 50 and 500 GeV with good sensitivity