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 Physics , 2015, Abstract: The Cherenkov Telescope Array (CTA) is the next generation ground-based very high energy gamma-ray observatory. The Large-Sized Telescope (LST) of CTA targets 20 GeV -- 1 TeV gamma rays and has 1855 photomultiplier tubes (PMTs) installed in the focal plane camera. With the 23 m mirror dish, the night sky background (NSB) rate amounts to several hundreds MHz per pixel. In order to record clean images of gamma-ray showers with minimal NSB contamination, a fast sampling of the signal waveform is required so that the signal integration time can be as short as the Cherenkov light flash duration (a few ns). We have developed a readout board which samples waveforms of seven PMTs per board at a GHz rate. Since a GHz FADC has a high power consumption, leading to large heat dissipation, we adopted the analog memory ASIC "DRS4". The sampler has 1024 capacitors per channel and can sample the waveform at a GHz rate. Four channels of a chip are cascaded to obtain deeper sampling depth with 4096 capacitors. After a trigger is generated in a mezzanine on the board, the waveform stored in the capacitor array is subsequently digitized with a low speed (33 MHz) ADC and transferred via the FPGA-based Gigabit Ethernet to a data acquisition system. Both a low power consumption (2.64 W per channel) and high speed sampling with a bandwidth of $>$300 MHz have been achieved. In addition, in order to increase the dynamic range of the readout we adopted a two gain system achieving from 0.2 up to 2000 photoelectrons in total. We finalized the board design for the first LST and proceeded to mass production. Performance of produced boards are being checked with a series of quality control (QC) tests. We report the readout board specifications and QC results.
 Physics , 2015, Abstract: The FlashCam group is currently preparing photomultiplier-tube based cameras proposed for the medium-sized telescopes (MST) of the Cherenkov Telescope Array (CTA). The cameras are designed around the FlashCam readout concept which is the first fully-digital readout system for Cherenkov cameras, based on commercial FADCs and FPGAs as key components for the front-end electronics modules and a high performance camera server as back-end. This contribution describes the progress of the full-scale FlashCam camera prototype currently under construction, as well as performance results also obtained with earlier demonstrator setups. Plans towards the production and implementation of FlashCams on site are also briefly presented.
 Physics , 2013, DOI: 10.1117/12.2023778 Abstract: Photomultiplier tube technology has been the photodetector of choice for the technique of imaging atmospheric Cherenkov telescopes since its birth more than 50 years ago. Recently, new types of photosensors are being contemplated for the next generation Cherenkov Telescope Array. It is envisioned that the array will be partly composed of telescopes using a Schwarzschild-Couder two mirror design never built before which has significantly improved optics. The camera of this novel optical design has a small plate scale which enables the use of compact photosensors. We present an extensive and detailed study of the two most promising devices being considered for this telescope design: the silicon photomultiplier and the multi-anode photomultiplier tube. We evaluated their most critical performance characteristics for imaging gamma-ray showers, and we present our results in a cohesive manner to clearly evaluate the advantages and disadvantages that both types of device have to offer in the context of GeV-TeV gamma-ray astronomy.
 Physics , 2012, DOI: 10.1016/j.nima.2012.03.011 Abstract: We performed photometric calibration of the PhotoMultiplier Tube (PMT) and readout electronics used for the new fluorescence detectors of the Telescope Array (TA) experiment using Rayleigh scattered photons from a pulsed nitrogen laser beam. The experimental setup, measurement procedure, and results of calibration are described. The total systematic uncertainty of the calibration is estimated to be 7.2%. An additional uncertainty of 3.7% is introduced by the transport of the calibrated PMTs from the laboratory to the TA experimental site.
 B. K. Lubsandorzhiev Physics , 2006, DOI: 10.1016/j.nima.2006.05.221 Abstract: In this very short note we review some historical aspects of photomultiplier tube invention. It is our tribute to the memory of great Soviet-Russian physicist and engineer Leonid Aleksandrovitch Kubetsky whose life and scientific achievements are described briefly. Particular efforts are made to shed light on a controversial issue of who invented the first photomultiplier tube. It is asserted that if to recognize L.A.Kubetsky's priority on the photomultiplier tube invention the last Beaune Conference would be held on the eve of the 75th Anniversary of that great event.
 Physics , 2011, DOI: 10.7529/ICRC2011/V09/1065 Abstract: We have developed an application-specific integrated circui (ASIC) for photomultipler tube (PMT) waveform digitization which is well-suited for the Schwarzschild-Couder optical system under development for the Cherenkov Telescope Array (CTA) project. The key feature of the "TARGET" ASIC is the ability to read 16 channels in parallel at a sampling speed of 1 GSa/s or faster. In combination with a focal plane instrumented with 64-channel multi-anode PMTs (MAPMTs), TARGET digitizers will enable CTA to achieve a wider field of view than the current Cherenkov telescopes and significantly reduce the cost per channel of the camera and readout electronics. We have also developed a prototype camera module, consisting of 4 TARGET ASICs and a 64-channel MAPMT. We report results from performance testing of the camera module and of the TARGET ASIC itself.
 Physics , 2015, Abstract: We present the development of a novel 11328 pixel silicon photomultiplier (SiPM) camera for use with a ground-based Cherenkov telescope with Schwarzschild-Couder optics as a possible medium-sized telescope for the Cherenkov Telescope Array (CTA). The finely pixelated camera samples air-shower images with more than twice the optical resolution of cameras that are used in current Cherenkov telescopes. Advantages of the higher resolution will be a better event reconstruction yielding improved background suppression and angular resolution of the reconstructed gamma-ray events, which is crucial in morphology studies of, for example, Galactic particle accelerators and the search for gamma-ray halos around extragalactic sources. Packing such a large number of pixels into an area of only half a square meter and having a fast readout directly attached to the back of the sensors is a challenging task. For the prototype camera development, SiPMs from Hamamatsu with through silicon via (TSV) technology are used. We give a status report of the camera design and highlight a number of technological advancements that made this development possible.
 Physics , 2015, Abstract: The camera of the Large Size Telescopes (LSTs) of the Cherenkov Telescope Array (CTA) consists of 265 photosensor modules, each of them containing 7 photomultiplier tubes (PMTs), a slow control board (SCB), a readout board, and a trigger logic. We have developed the SCB, which is installed between the 7 PMTs and the readout board. The main task for SCBs is the controlling of the high voltages for the PMTs and the monitoring of their anode currents. In addition, the SCB provides the functionality to create test pulses that can be injected at the input of the PMT preamplifier in order to emulate a PMT signal without the need of setting a high voltage, or even without the PMT itself. The test pulses have a very similar width as the PMT pulses (less than 3 ns FWHM) and their amplitude can be adjusted in a wide dynamic range. These features allow us not only to test the functionality of the camera modules but also to fully characterize these. We report on the design and the functions of the SCB together with the results of test measurements.
 Physics , 2013, Abstract: The Cherenkov Telescope Array (CTA) is a next-generation ground-based observatory for g -rays with energies between some ten GeV and a few hundred TeV. CTA is currently in the advanced design phase and will consist of arrays with different size of prime-focus Cherenkov telescopes, to ensure a proper energy coverage from the threshold up to the highest energies. The extension of the CTA array with double-mirror Schwarzschild- Couder telescopes is planned to improve the array angular resolution over wider field of view.We present an end-to-end Monte-Carlo comparison of trigger concepts for the different imaging cameras that will be used on the Cherenkov telescopes. The comparison comprises three alternative trigger schemes (analog, majority, flexible pattern analysis) for each camera design. The study also addresses the influence of the properties of the readout system (analog bandwidth of the electronics, length of the readout window in time) and uses an offline shower reconstruction to investigate the impact on key performances such as energy threshold and flux sensitivity
 Physics , 2015, Abstract: An established technique for the measurement of ultra-high-energy-cosmic-rays is the detection of the fluorescence light induced in the atmosphere of the Earth, by means of telescopes equipped with photomultiplier tubes. Silicon photomultipliers (SiPMs) promise an increase in the photon detection efficiency which outperforms conventional photomultiplier tubes. In combination with their compact package, a moderate bias voltage of several ten volt and single photon resolution, the use of SiPMs can improve the energy and spatial resolution of air fluorescence measurements, and lead to a gain in information on the primary particle. Though, drawbacks like a high dark-noise-rate and a strong temperature dependency have to be managed. FAMOUS is a refracting telescope prototype instrumented with 64 SiPMs of which the main optical element is a Fresnel lens of 549.7 mm diameter and 502.1 mm focal length. The sensitive area of the SiPMs is increased by a special light collection system consisting of Winston cones. The total field of view of the telescope is approximately 12 $^\circ$. The frontend electronics automatically compensates for the temperature dependency of the SiPMs and will provide trigger information for the readout. Already for this prototype, the Geant4 detector simulation indicates full detection efficiency of extensive air showers of $E=10^{18}\,\text{eV}$ up to a distance of 6 km. We present the first working version of FAMOUS with a focal plane prototype providing seven active pixels.
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