Prototype Schwarzschild-Couder Telescope (pSCT, see Fig. 1), one of prototype telescopes developed for the Cherenkov Telescope Array (CTA) project, observed the Crab Nebula and successfully detected very-high-energy gamma rays from the object with a statistical significance of 8.3σ (Figs. 2-4). The viability of two new technologies used in pSCT, the Schwarzschild-Couder optical system with a large field of view of 8 degrees and a small camera pixel size of 6 mm realized by using silicone photomultipliers (SiPMs), have been proved by this observations.

Prof. Hiroyasu Tajima and Dr. Akira Okumura of the Cosmic-ray Research Division have been actively working in the hardware and software development of several different CTA telescope designs. For the pSCT development, the ISEE group contributed in development of SiPMs, development of waveform sampling and readout electronics, camera control and data acquisition software development, and ray-tracing simulation of the telescope.

CTA is the next-generation ground-based gamma-ray observatory to be built in both the Northern (La Palma, Spain) and Southern Hemisphere (Paranal, Chile). It will observe high-energy objects with an energy coverage from 20 GeV to beyond 300 TeV by deploying more than 100 gamma-ray telescopes.

Fig. 1: The pSCT Inauguration ceremony held at the Fred Lawrence Whipple Observatory in Arizona, US on Jan 17, 2019. (Credit: Deivid Ribeiro, Columbia University)

Fig. 2: Significance map of the pSCT gamma-ray observations. The Crab Nebula is located at the image center. (Credit：CTA/SCT Consortium)

Fig. 3: Gamma-ray events imaged by pSCT. Every frame shows Cherenkov photons emitted in a gamma-ray induced air shower. (Credit：CTA/SCT Consortium)

Fig. 4: Distributions of the angular differences between the Crab Nebula direction and gamma-ray image axes (red for Crab Nebular observations and black for background-region observations). (Credit：CTA/SCT Consortium)