Speaker
Description
The sensitivity achievable with stellar intensity interferometers using Imaging Atmospheric Cherenkov Telescopes (IACTs) can be significantly enhanced with the use of ultra-fast single-photon detectors. Conventional inter-telescope baselines of ∼100 m probe angular scales of order ~1 mas, while correlations between sections of a telescope mirror provide access to larger structures of order >~ 5 mas.
Within this context, we present the development and first tests of the "Butterfly's Eye" concept, an approach designed to exploit the segmented reflector of the MAGIC telescopes while enabling the use of photodetectors with transit-time spreads below 100 ps. By coupling narrow-band filtered light from selected mirror facets to Hybrid Photodiodes (HPDs) optimized for single-photon timing, photon arrival times can be recorded with tens-of-picoseconds precision and correlated in real time.
Laboratory measurements at the Instituto de Astrofísica de Canarias demonstrate correlation peaks with widths of approximately 60 ps, two orders of magnitude narrower than those obtained in our MAGIC intensity interferometry system. Building on these results, a hardware system was developed at CIEMAT to install it on the MAGIC-2 camera lid, allowing mounting and removal in a few minutes. First stellar observations show correlation excesses at the expected delay, validating the end-to-end concept.
We will discuss the optical design, detector performance, laboratory characterization, telescope deployment, and the results obtained during the observing campaigns. These studies are a technological pathfinder for future high-time-resolution intensity interferometers based on IACTs.
