ROBAST: Development of a Non-sequential Ray-tracing Simulation Library and its Applications in the Cherenkov Telescope Array

Abstract

We have developed a non-sequential ray-tracing simulation library, ROot-BAsed Simulator for ray Tracing (ROBAST), which is aimed for wide use in optical simulations of cosmicray (CR) and gamma-ray telescopes. The library is written in C++ and fully utilizes the geometry library of the ROOT analysis framework. Despite the importance of optics simulations in CR experiments, no open-source software for ray-tracing simulations that can be widely used existed. To reduce the unnecessary effort demanded when different research groups develop multiple raytracing simulators, we have successfully used ROBAST for many years to perform optics simulations for the Cherenkov Telescope Array (CTA). Among the proposed telescope designs for CTA, ROBAST is currently being used for three telescopes: a Schwarzschild-Couder telescope, one of the Schwarzschild-Couder small-sized telescopes, and a large-sized telescope (LST). ROBAST is also used for the simulations and the development of hexagonal light concentrators that has been proposed for the LST focal plane. By fully utilizing the ROOT geometry library with additional ROBAST classes, building complex optics geometries that are typically used in CR experiments and ground-based gamma-ray telescopes is possible. We introduce ROBAST and show several successful applications for CTA.

Assessment of the GCT Prototype’s Optical System Implementation and Other Key Performances for the Cherenkov Telescope Array

“…The PSF, which can be decomposed into two Gaussian functions, can be reproduced by light diffusion on both the M1 and M2 mirrors in a Gaussian distribution with standard deviation σ of 4.3 arc minutes. As proved with ROBAST simulations [9], and in agreement with theoretical…”

SiPM Based Focal Plane Instrumentation Prototype for the MAGIC Atmospheric Cherenkov Telescope

“…Each concentrator should ideally accept all light coming from the telescope mirror, and reject light from the ground or other objects located adjacent to the mirror surface. The light concentrators were optimized for an acceptance angle of ~30 o using the ROBAST simulation program developed for simulating IACT light concentrators [5]. The maximum acceptance angle of the SiPM devices was measured in the laboratory at six separate wavelengths between 309 and 598 nm for both S and P polarization orientations (Fig.…”