| Abstract : | The TACTIC (TeV Atmospheric Cherenkov Telescope with Imaging Camera) γ- ray telescope has been operational for several years at Mt. Abu (24.60 N, 72.70 E, 1300m asl), India, to study TeV gamma-ray emission from celestial sources. The telescope has a 9.5m2 tessellated light collector and a 349-pixel medium-resolution imaging camera. The light-collector of the TACTIC telescope uses 34 front-face, aluminium-coated, circular spherical mirrors, each 60 cm in diameter, with a focal length of∼4000 mm. The dead space of the telescope basket employing the present circular mirror arrangement accounts for ~ 30% of the total area. The two largest contributors to the dead space are the gap left between the circular mirrors and the projection of the clamps on the mirror surface.
A feasibility study was conducted to investigate the effect of replacing the current mirrors with 60 square diamond-turned metallic mirrors, each of size 445 x 445 mm, which results in ~25% increase in light collection area. Preliminary calculations show that the telescope's threshold energy will be reduced from 850 GeV to 600 GeV due to an estimated increase in light collection area. The telescope sensitivity is also expected to improve with the source detection time of ~ 7 hours at 5σ statistical significance level, instead of the current ~12 hrs.
The proposed design of the light collector area of the telescope employing the square metallic mirrors, its support mechanism and preliminary sensitivity estimates would be presented in the meeting.
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