Filters for X-ray detectors on Space missions

TL;DR

This paper reviews the design, materials, and calibration of X-ray filters used in space missions, focusing on their role in protecting detectors and optimizing quantum efficiency at low energies.

Contribution

It provides a comprehensive overview of filter materials, design considerations, modeling, testing, and calibration techniques for space-based X-ray detectors, including future technologies.

Findings

Filter materials and designs are crucial for detector performance.

Modeling and calibration are essential for accurate filter response.

Emerging materials are under investigation for future missions.

Abstract

Thin filters and gas tight windows are used in Space to protect sensitive X-ray detectors from out-of-band electromagnetic radiation, low-energy particles, and molecular contamination. Though very thin and made of light materials, filters are not fully transparent to X-rays. For this reason, they ultimately define the detector quantum efficiency at low energies. In this chapter, we initially provide a brief overview of filter materials and specific designs adopted on space experiments with main focus on detectors operating at the focal plane of grazing incidence X-ray telescopes. We then provide a series of inputs driving the design and development of filters for high-energy astrophysics space missions. We begin with the identification of the main functional goals and requirements driving the preliminary design, and identify modeling tools and experimental characterization techniques needed to prove the technology and consolidate the design. Finally, we describe the calibration activities required to derive the filter response with high accuracy.We conclude with some hints on materials and technologies presently under investigation for future X-ray missions.