Abstract
The focal plane camera is the core component of the Wide Field-of-view Cherenkov/fluorescence Telescope Array (WFCTA) of the Large High-Altitude Air Shower Observatory (LHAASO). Because of the capability of working under moonlight without aging, silicon photomultipliers (SiPM) have been proven to be not only an alternative but also an improvement to conventional photomultiplier tubes (PMT) in this application. Eighteen SiPM-based cameras with square light funnels have been built for WFCTA. The telescopes have collected more than 100 million cosmic ray events and preliminary results indicate that these cameras are capable of working under moonlight. The characteristics of the light funnels and SiPMs pose challenges (e.g. dynamic range, dark count rate, assembly techniques). In this paper, we present the design features, manufacturing techniques and performances of these cameras. Finally, the test facilities, the test methods and results of SiPMs in the cameras are reported here.
Highlights
The energy spectrum of cosmic rays (CRs) exhibits several interesting features that provide a wealth of informationM
The focal plane camera which has a field of view (FoV) of 16◦ × 16◦ is composed by an array of 32 × 32 pixels, each with an angular size of 0.5◦ × 0.5◦, featuring a silicon photomultipliers (SiPM) coupled to a square light funnel
If the angular distance between the edge of the telescope FoV and the moon is less than 1 ◦, the HV power supply will be turned off automatically to avoid exposing the camera to the direct moonlight, which may lead to the power supply working in the maximum current limiting output state
Summary
The energy spectrum of cosmic rays (CRs) exhibits several interesting features that provide a wealth of information. EAS produce a large number of secondary photons which can be detected by the camera of the imaging atmosphere Cherenkov telescopes (IACT). The main information about the telescopes of WFCTA can be found in Sect. 3, the WFCTA SiPM camera structure and main features are described. 5. Each telescope of WFCTA consists of a segmented spherical mirror of about 5 m2 with a SiPM-based camera installed at its focal plane. The focal plane camera which has a field of view (FoV) of 16◦ × 16◦ is composed by an array of 32 × 32 pixels, each with an angular size of 0.5◦ × 0.5◦, featuring a SiPM coupled to a square light funnel.
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