Development of an atmospheric Cherenkov imaging camera for the CANGAROO-III experiment

Abstract

A Cherenkov imaging camera for the CANGAROO-III experiment has been developed for observations of gamma-ray induced air-showers at energies from 10 11 to 10 14 eV. The camera consists of 427 pixels, arranged in a hexagonal shape at 0.17 • intervals, each of which is a 3/4-inch diameter photomultiplier module with a Winston-cone-shaped light guide. The camera was designed to have a large dynamic range of signal linearity, a wider field of view, and an improvement in photon collection efficiency compared with the CANGAROO-II camera. The camera, and a number of the calibration experiments made to test its performance, are described in detail in this paper.

Prototyping hexagonal light concentrators using high-reflectance specular films for the large-sized telescopes of the Cherenkov Telescope Array

“…II telescope has a diameter of 28 m, achieving threshold trigger energies of ∼50 GeV and ∼20 GeV, respectively [5,7]. It is, however, known from an internal CTA study that the construction cost of a large IACT increases roughly by a power of 1.35 as the mirror area increases [23]; thus, maximizing the collection efficiency of camera pixels using a less expensive technology to produce light concentrators is a cost-effective way to build a number of IACTs.The focal-plane cameras of IACTs are covered by UV-sensitive photodetector pixels on which hexagonal light concentrators are usually attached to reduce the dead area between photodetectors [6,10,12,19,21]. Compound parabolic concentrators (CPC or so-called Winston cones) [26] with hexagonal entrance apertures have been widely used in IACTs for this purpose because they can selectively guide photons coming from the telescope-mirror direction to the sensitive area of photodetectors and because those from directions outside the mirror are rejected efficiently at the same time.The use of Winston cones in IACTs was first proposed for the CAT experiment in 1994 [20].…”

CANGAROO-III OBSERVATION OF TeV GAMMA RAYS FROM THE UNIDENTIFIED GAMMA-RAY SOURCE HESS J1614–518

“…Each telescope has a 10 m diameter reflector which consists of 114 segmented fiber reinforced plastic spherical mirrors mounted on a parabolic frame (Kawachi et al 2001). The imaging camera system consists of 427 photomultipliers (PMTs) and has an FOV of 4.0 deg (Kabuki et al 2003). The PMT signals are digitized by charge analog-to-digital converters (ADCs) and multi-hit time-to-digital converters (TDCs; Kubo et al 2001).…”

Air Cherenkov methods in cosmic rays: Review and some history

“…(iii) Most modern air Cherenkov telescopes make stereoscopic observations using several large mirrors. The Japanese-Australian telescope CANGAROO-III in Australia (Kabuki et al, 2003) and German telescope HESS in Namibia (Bernlöhr et al, 2003) have 4 mirrors separated by about 100 m. The project VERITAS (Weekes et al, 2002) includes seven 10-12 m reflectors similar to that used in the first Whipple telescope. Among these telescopes of last generation only MAGIC has a single reflector, but recently it has been announced that the twin MAGIC-II telescope is under construction.…”