Develop a perfect spectrometer in water window

TL;DR

This paper introduces a universal grazing incidence spectrometer design optimized for the water window, achieving high spectral resolution and intensity by eliminating aberrations and precisely focusing across the spectral range.

Contribution

The paper presents a novel spectrometer design that provides excellent meridional flat field and eliminates sagittal astigmatism, enhancing spectral resolution and intensity in the water window range.

Findings

Achieves spectral resolving power of 6000-18000 for 200um source size.

Potential to reach 20000-40000 resolution with smaller sources.

Provides a universal scheme applicable across the water window spectrum.

Abstract

We report a novelly universal scheme for design of a grazing incidence spectrometer, which creates an excellent meridional flat field in its detector domain to deliver the desired spectral resolution throughout the full designated spectral range, while eliminates the sagittal astigmatism to enhance the spectral intensity simultaneously. The intrinsic optical properties of the system are thoroughly investigated and optimized, especially how the detector plane approaches to the actual meridional or sagittal focal curves is well quantified. We demonstrated within the "water window", i.e. 2-5nm wavelength range, the resolving power of 6000-18000 could be achieved for the effective meridional source size of 200um r.m.s.; and it would be further improved to 20000-40000 if the source size is confined down to 50um r.m.s.