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Register a new userThe reflecting surface of the MAGIC-II Telescope
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Authors
D. Bastieri
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The MAGIC Collaboration is building a second telescope, MAGIC II, improving the design of the current MAGIC Telescope. MAGIC II is being built at 85 m of distance from MAGIC I, and will also feature a huge reflecting surface of ~240 m$^2$ of area. One of the improvement is the design for the mirror of MAGIC II, that are lighter and larger, being square of 1 m of side and weighting around 15 kg. For the development and production of the new mirrors, two different techniques, both reliable and affordable in price, were selected: the diamond milling of aluminium surfaces and the cold slumping of thin glass panes. As tests for the second one are still ongoing, we present a description of the diamond milling technique, and its application and performance to the produced mirrors.
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The MAGIC 17m diameter Cherenkov telescope will be upgraded with a second telescope within the year 2007. The camera of MAGIC-II will include several new features compared to the MAGIC-I camera. Photomultipliers with the highest available photon collection efficiency have been selected. A modular design allows easier access and flexibility to test new photodetector technologies. The camera will be uniformly equipped with 0.1 degree diamter pixels, which allows the use of an increased trigger area. Finally, the overall signal chain features a large bandwidth to retain the shape of the very fast Cherenkov signals.
MAGIC comprises two 17m diameter IACTs to be operated in stereo mode. Currently we are commissioning the second telescope, MAGIC II. The camera of the second telescope has been equipped with 1039 pixels of 0.1-degree diameter. Always seven pixels are grouped in a hexagonal configuration to form a cluster. This modular design allows easier control and maintenance of the camera. The pixel sensors are high quantum efficiency photomultiplier tubes (PMTs) from Hamamatsu (superbialkali type, QE ~ 32% at the peak wavelength) that we operate at rather low gain of 30 k. This allows us to also perform extended observations under moderate moonlight. The system of two MAGIC telescopes will at least double the sensitivity compared to MAGIC I and also will allow us to lower the energy threshold.Here we will report the performances of the Camera of the second MAGIC telescope.
In this contribution we describe the hardware, firmware and software components of the readout system of the MAGIC-II Cherenkov telescope on the Canary island La Palma. The PMT analog signals are transmitted by means of optical fibers from the MAGIC-II camera to the 80 m away counting house where they are routed to the new high bandwidth and fully programmable receiver boards (MONSTER), which convert back the signals from optical to electrical ones. Then the signals are split, one half provide the input signals for the level ONE trigger system while the other half is sent to the digitizing units. The fast Cherenkov pulses are sampled by low-power Domino Ring Sampler chips (DRS2) and temporarily stored in an array of 1024 capacitors. Signals are sampled at the ultra-fast speed of 2 GSample/s, which allows a very precise measurement of the signal arrival times in all pixels. They are then digitized with 12-bit resolution by an external ADC readout at 40 MHz speed. The Domino samplers are integrated in the newly designed mezzanines which equip a set of fourteen multi-purpose PULSAR boards. Finally, the data are sent through an S-LINK optical interface to a single computer. The entire DAQ hardware is controlled through a VME interface and steered by the slow control software program (MIR). The Data AcQuisition software program (DAQ) proceeds finally to the event building and data storage.
One of the main design goals of the MAGIC telescopes is the very fast repositioning in case of Gamma Ray Burst (GRB) alarms, implying a low weight of the telescope dish. This is accomplished by using a space frame made of carbon fiber epoxy tubes, resulting in a strong but not very rigid support structure. Therefore it is necessary to readjust the individual mirror tiles to correct for deformations of the dish under varying gravitational load while tracking an object. We present the concept of the Active Mirror Control (AMC) as implemented in the MAGIC telescopes and the actual performance reached. Additionally we show that also telescopes using a stiff structure can benefit from using an AMC.
We report on the results from the observations in very high energy band (VHE, E_gamma > 100GeV) of the black hole X-ray binary (BHXB) Cygnus X-1. The observations were performed with the MAGIC telescope, for a total of 40 hours during 26 nights, spanning the period between June and November 2006. We report on the results of the searches for steady and variable gamma-ray signals, including the first experimental evidence for an intense flare, of duration between 1.5 and 24 hours.
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