Geometry and optics calibration of WFCTA prototype telescopes using star light
Lingling MaYunxiang BaiZ. CaoMingjun ChenLihong ChenS. Z. ChenYao ChenKai-Qi DingH. H. HeJia LiuJiali LiuXiaoxiao LiXinhua MaX. D. ShengGang XiaoM. ZhaShoushan ZhangYong ZhangJing ZhaoBin Zhou
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Abstract:
The Large High Altitude Air Shower Observatory project is proposed to study high energy gamma ray astronomy ( 40 GeV-1 PeV ) and cosmic ray physics ( 20 TeV-1 EeV ). The wide field of view Cherenkov telescope array, as a component of the LHAASO project, will be used to study energy spectrum and compositions of cosmic ray by measuring the total Cherenkov light generated by air showers and shower maximum depth. Two prototype telescopes have been in operation since 2008. The pointing accuracy of each telescope is crucial to the direction reconstruction of the primary particles. On the other hand the primary energy reconstruction relies on the shape of the Cherenkov image on the camera and the unrecorded photons due to the imperfect connections between photomultiplier tubes. UV bright stars are used as point-like objects to calibrate the pointing and to study the optical properties of the camera, the spot size and the fractions of unrecorded photons in the insensitive areas of the camera.Keywords:
Air shower
Cherenkov Telescope Array
Optical telescope
Cherenkov detector
Silicon Photomultiplier
Ultraviolet
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Cherenkov detector
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System for photomultiplier tubes characterization and data acquisition for water Cherenkov detectors
A water Cherenkov detector uses the emission of Cherenkov radiation for detecting the trace of secondary particles generated by extensive air shower cascades traversing a purified water tank. These are used for the detection of high energy gamma-rays. A fundamental component of the detectors consists of the photomultiplier tubes (PMTs) used for detection of the Cherenkov radiation that is produced by very high energy particles moving faster than the speed of of light in the medium. INAOE, being one of the leading institutions of HAWC, decided to develop a system to characterize the PMTs that includes measurement of dark current, linear response region determination, response to a photoelectron and hence the gain. This characterization is indispensable when several PMTs operate in an array of water Cherenkov detectors. The system was further developed to simultaneously acquire data of several phototubes, allowing also to measure coincidences. Additionally, the VME scalers modules will be used to monitor up to 32 phototubes. This system has been used to characterize the PMTs of the LAGO experiment and can be used in the future for any type of PMT system.
Cherenkov detector
Particle detector
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Many high-energy physic experiments use Cherenkov radiation as a detection method. Photomultiplier tubes are typically used to convert the radiation into an electrical signal. In this work, we present the development of a new device dedicated to the detection of Cherenkov radiation photons that could replace photomultiplier tubes in experiments that detect this radiation. C-Arapuca is the name given to this device, as it uses the concept of photon trapping in a box, already used in the Deep Underground Neutrino Experiment, but now adapted for the detection of a range of energies of Cherenkov radiation photons. Calculations of efficiency, design, and performance of the C-Arapuca are described, highlighting its performance compared to photomultiplier tube in the detection of Cherenkov radiation. A shortpass dichroic filter with a cut-off wavelength at 400 nm was used in the C-Arapuca window, and the inner part of the box, covered with highly reflective material, contains a blue-emitting wavelength-shifting plastic slab and Hamamatsu silicon photomultipliers. In this study, a cylindrical tank containing 550 liters of ultrapure water was used, in which two C-Arapucas and a photomultiplier tube with a photocathode of 110 mm in diameter were installed. The useful area of the optical window of a C-Arapuca is 70.0 x 93.0 mm². Relativistic muons from local cosmic radiation passing through the water volume were used as a source of Cherenkov radiation detected by both the C-Arapucas and the photomultiplier tube, allowing for a relative comparison of the performance of the new device.
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Cherenkov detector
Silicon Photomultiplier
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Cherenkov detector
Photoelectric effect
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Calorimeter (particle physics)
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Two air shower Cherenkov telescopes, as prototype detector of a wide field of view (FOV) Cerenkov/fluorescence telescope array (WFCA), are operated at the ARGO-YBJ experiment site in Tibet. Using the Cherenkov signal in the shower images recorded by the Cherenkov telescopes and shower geometry measured by the ARGO-YBJ detector, shower energy can be reconstructed. With the help of such Coincident events an absolute calibration of the energy scale for the ground based experiment will be established by comparing with the balloon borne experimental results.
Air shower
Cherenkov detector
Shower
Gamma-Ray Astronomy
Cherenkov Telescope Array
Energy spectrum
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The ASTRI Mini-Array is an INAF project aimed at observing astronomical objects that emit photons in the TeV and multi-TeV spectral bands. It consists of an array of nine innovative imaging atmospheric Cherenkov telescopes under deployment at the Observatorio del Teide (Tenerife, Spain). Detailed simulations of atmospheric showers of Cherenkov events using Monte Carlo methods are needed to estimate the expected performance of the ASTRI Mini-Array under different observing conditions, to validate the Monte Carlo simulation chain, for calibration purposes and for the development of ancillary instruments, and finally to allow the reconstruction of the real data collected by the array. The production of events detected by Cherenkov telescopes comprises the simulation of the development of particle cascade in the atmosphere with the associated emission of Cherenkov light and the simulation of the response of telescopes to the impinging light; the first task is carried out with the CoRSiKa software (which also simulates the emission of Cherenkov light), while the second is achieved with the sim_telarray package by simulating the transmission of Cherenkov light from the emission point to the telescope and the response of the telescope itself. In this contribution, we present the ASTRI Mini-Array simulation system, describing in detail the software pipeline adopted for the generation of Monte Carlo events, the hardware facilities dedicated to run the simulations at the offsite ASTRI Data Center, and the final products delivered for the Cherenkov data analysis.
Cherenkov Telescope Array
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The latest achievements in the development of gaseous detectors for registering UV and visible photons are described. Possible modifications of their design for some particular applications such as the readout of crystal scintillators. noble liquids, fibers and for large area Cherenkov detectors are discussed.
Cherenkov detector
Particle detector
Silicon Photomultiplier
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The photon detection efficiency of two sets of R10560-100-20 superbialkali photomultiplier tubes from Hamamatsu were measured between 200 nm and 750 nm to quantify a possible degradation of the photocathode sensitivity after four years of operation in the cameras of the VERITAS Cherenkov telescopes. A sample of 20 photomultiplier tubes, which was removed from the telescopes was compared with a sample of 20 spare photomultiplier tubes, which had been kept in storage. It is found that the average photocathode sensitivity marginally increased below 300 nm and dropped by 10% to 30% above 500 nm. The average photocathode sensitivity folded with the Cherenkov spectrum emitted by particles in air showers, however, reveals a consistent detection yield of 18.9 ± 0.2% and 19.1 ± 0.2% for the sample removed from the telescope and the spare sample, respectively.
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Silicon Photomultiplier
Cherenkov detector
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Imaging Atmospheric Cherenkov Telescopes (IACTs) have opened a new astronomical window at photon energies exceeding tens of GeV during the last decades. The technique relies on the detection of Cherenkov light produced by electromagnetic showers in the Earth’s atmosphere using telescope mirrors with diameters of a few to tens of meters. A world-wide community is behind the design and construction of the next generation Cherenkov Telescope Array (CTA), consisting of two arrays of IACTs at the northern and southern hemispheres. I will review the astrophysics that IACTs are revealing at these energies, cover the design characteristics of CTA, the status of the project and the physics prospects of the instrument.
Cherenkov Telescope Array
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