Evaluation of the effective mirror area of CTA Small-Sized Telescopes for camera design and Monte Carlo simulation

TL;DR

This paper assesses the effective mirror area of CTA Small-Sized Telescopes using detailed 3D ray-tracing simulations to optimize camera design and account for structural shadowing effects.

Contribution

It introduces a complex 3D modeling approach with ROBAST to accurately evaluate mirror area and shadowing in SSTs, improving upon simplified models.

Findings

Complex 3D models reveal significant shadowing effects.

Optimized camera size minimizes photon loss.

Effective area meets SST requirements.

Abstract

The effective mirror area of an imaging atmospheric Cherenkov telescope is a crucial key parameter for trigger threshold determination and energy calibration. It is usually calculated by 3D ray-tracing simulation using a simplified telescope model, and the result is used in Monte Carlo simulations. However, simplified telescope and camera models are not adequate for the Schwarzschild-Couder configuration to be used in Small-Sized Telescopes (SSTs) of the Cherenkov Telescope Array. This is because the complex 3D structure of the secondary mirror, telescope masts, and camera body block a significant fraction of Cherenkov and night-sky photons. To evaluate the effective mirror area of an SST and to finalize its camera body design with minimal shadowing, a complex 3D model was built and simulated using the ROBAST ray-tracing library. A camera body size of 570 mm and a window size of 430 mm were selected for the final camera design based on the evaluation of shadowing by simulation. A non-axisymmetric effective area distribution was determined via the modeling of the complex telescope structure, while meeting the SST effective area requirement.