Current progress of x-ray multilayer telescope optics based on thermally slumping glass for eXTP mission

The enhanced X-ray Timing and Polarimetry (eXTP) is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. One of the approaches to obtain large collecting areas is mounting the thermally slumping glass segments (SG) in a nested conical approximation Wolter-I design telescope. In the last two years, we have made a great progress in the research of telescope on the base of thermally slumping glass technology, and successfully fabricated several prototypes for the eXTP SFA mission. This paper intends to provide an overview of the progress. Now we can routinely produce cylindrical glasses with 36-60″ resolution (HPD) and the best mirror produced has an angular resolution of 36″ (HPD). The glass substrates coated with Pt and C layers to obtain high reflectivity of X-ray at 1-10keV, and the reliability of multilayers coating studies are under way as well. The in-situ measurement system and 3-dimention ray-tracing program have developed and can feed measurement data back into the assembly process for improving upon the later mounted mirrors in real time. We fabricated a 3-layer telescope prototype with the diameter of 106mm and focal length of 2000mm, and tested the focusing performance in SSRF, China. The measured HPD is 66″, and W90 is 168″, which meets the requirement of angular resolution of eXTP/SFA.

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