Simulation of a Typical Wolter-I X-ray Telescope Using the Geant4 Toolkit

Wolter-I is the most common optics in X-ray telescopes. In addition to using high-reflectivity mirrors, it is necessary to use more than a single Wolter-I shell and an appropriate number of shells in a telescope structure to collect the highest number of photons at the detector position. By considering various parameters such as the weight of the telescope, the desired wavelength range, and the available technology, the proper number of Wolter-I shells and their specifications can be determined. In the present work, using our Geant4-based X-ray telescope simulation application, we have simulated an X-ray telescope with 58 shells similar to XMM-Newton telescope. Based on the characteristics of XMM-Newton telescope, we developed a set of procedures to define the properties of the shells and constructed them in the application. The performance of the simulated telescope in collecting specified X-rays has been investigated. We executed the application at five energies, including 1, 2, 3, 4, and 5 keV. These energies are in the energy range in which XMM-Newton mirrors are most efficient. We also investigated the telescope's performance for some widely used materials as the surface of mirrors with a thickness of one nanometer. The simulation results confirmed that the presence of more shells with different radii increases the telescope's ability to collect photons over a broader range of energy. Also, the simulated telescope performed better for shells with smaller radii for every material and in all the energies.