Very High Resolution Solar X-ray Imaging Using Diffractive Optics

TL;DR

This paper presents the development of high-resolution X-ray diffractive optics for solar flare imaging, enabling detailed observation of hot plasma regions with unprecedented angular resolution to advance solar physics research.

Contribution

It introduces the design, fabrication, and testing of phase zone plate X-ray lenses capable of 0.1 arcsec resolution for solar flare imaging, and discusses a formation-flying mission concept.

Findings

Designed phase zone plate X-ray lenses with ~100 m focal length.

Demonstrated feasibility of a two-spacecraft formation-flying mission for high-resolution imaging.

Enabled potential to resolve magnetic loop cross-sections and flare energy regions.

Abstract

This paper describes the development of X-ray diffractive optics for imaging solar flares with better than 0.1 arcsec angular resolution. X-ray images with this resolution of the \geq10 MK plasma in solar active regions and solar flares would allow the cross-sectional area of magnetic loops to be resolved and the coronal flare energy release region itself to be probed. The objective of this work is to obtain X-ray images in the iron-line complex at 6.7 keV observed during solar flares with an angular resolution as fine as 0.1 arcsec - over an order of magnitude finer than is now possible. This line emission is from highly ionized iron atoms, primarily Fe xxv, in the hottest flare plasma at temperatures in excess of \approx10 MK. It provides information on the flare morphology, the iron abundance, and the distribution of the hot plasma. Studying how this plasma is heated to such high temperatures in such short times during solar flares is of critical importance in understanding these powerful transient events, one of the major objectives of solar physics. We describe the design, fabrication, and testing of phase zone plate X-ray lenses with focal lengths of \approx100 m at these energies that would be capable of achieving these objectives. We show how such lenses could be included on a two-spacecraft formation-flying mission with the lenses on the spacecraft closest to the Sun and an X-ray imaging array on the second spacecraft in the focal plane \approx100 m away. High resolution X-ray images could be obtained when the two spacecraft are aligned with the region of interest on the Sun. Requirements and constraints for the control of the two spacecraft are discussed together with the overall feasibility of such a formation-flying mission.