Einstein probe wide field telescope flight mirror module characterization at PANTER test facility

Abstract

The Einstein Probe Wide-field X-ray Telescope (WXT), planned to launch in late 2023, is dedicated to the study of time-domain high-energy astrophysics to monitor variable objects in the range of 0.5 to 4.0 keV. The full wide-field telescope is made up of 12 Lobster-eye modules. Each module consists of an optics assembly of 36 Micro Pore Optic (MPO) chips divided into four sectors and four CMOS detectors positioned in the respective focal plane of each sector. At the PANTER x-ray test facility, we characterize the performance of one of the 12 flight mirror modules. The full flight model calibration includes measurements for detailed focus searches, extended mosaic scans of the on-axis Point Spread Function (PSF), and Focal Plane Mappings (FPM) covering various off-axis, and one on-axis exposure, performed for each individual mirror sector and at various energies. The best focus positions were determined at the energies C-K, O-K, Cu-L, and Ti-K. The optic was characterized in terms of Half Energy Width (HEW) and effective area on-axis and off-axis at the energies C-K (only FPM), Ti-L, O-K, Cu-L, Al-K, W-M, and Ti-K, and two broad energy ranges, very low Energy band continuum (vlEbc 0.2 to 2.0 keV), and low Energy band continuum (lEbc 0.8 to 4.0 keV). The measurements were made using the TRoPIC detector (pnCCD), a prototype of the eROSITA cameras, and a high spatial resolution detector (PIXI). The focal plane mapping results show symmetrically distributed Point Spread Functions (PSFs) over the large field of view of ±4.7 degrees of each sector. The effective area results of the energy band continua match well with the theoretical model. We will discuss the test setup, measurements, and results of the full performance of the WXT Flight Mirror module (FM5) tested at PANTER.