Abstract Details

Name: Dr V K Dhar
Affiliation: Bhabha Atomic Research Centre
Conference ID: ASI2017_1285
Title : Fabrication, alignment and vibration testing of diamond turned metallic mirrors for the MACE γ-ray telescope.
Authors and Co-Authors : V. K. Dhar, K.K.Singh, K. Venugopal, N. Kumar, N. Chouhan, A. K. Tickoo, R. C. Rannot, R. Koul, S. Norlah, T. Rinchen, Keshav N, R. Balasubramanium, A.K.Sinha, P.I. Hadagali, A Kumar, P. K. Biswas, S.P. Srivastava, D. Udupa, N. K. Sahoo and R. B. Tokas.
Abstract Type : Poster
Abstract Category : Instrumentation and Techniques
Abstract : A Cherenkov imaging telescope, MACE is presently being setup at Hanle(32.7°N, 79.0°E, 4270m) near Leh (J&K state), for the study of cosmos in the energy range ~20GeV-5TeV. The telescope, comprising of a parabolic 21m diameter tessellated light collector is made up of diamond turned aluminum mirrors developed for the first time in the country. The telescope, comprising of ~ 337 square meter light collector area will be the largest telescope of its kind in the Northern hemisphere. MACE telescope will deploy ~ 1 m x 1m panels, with each panel consisting of 4 diamond turned spherical mirrors of size ~0.5m x 0.5m. A total of 1564 such diamond turned metallic mirrors of varying focal lengths have been fabricated for MACE. The mean spot size of these mirrors measured using a standard 2f method is D80 ≤3.5mm (where D80 is the radius of the circle within which 80% of rays are captured). A major challenge after fabrication of these metallic mirrors is to align 4 mirrors on a single panel so as to replicate a single 1mX1m mirror with a spot size of D80 ≤6mm at the focal length, without compromising on the individual mirror facet spot size. Apart from this, the arrangement should withstand vibrations which the telescope will encounter during the actual course of observations. Again, an indigenous design based on usage of ball and socket joints has been employed to meet this requirement. To quantify the alignment design, the aligned panels have been subjected to rigorous vibration testing. Details of the manufacturing process, experimental set used for qualifying the mirrors, reflectivity measurements, panel alignment methodology and vibration testing will be presented in the paper.