Upgrades to x-ray microcalorimeter fusion diagnostic to improve calibration, spectral bandwidth selection, and count rate adjustment.

This paper presents progress made toward the overarching goal to adapt single-photon-counting microcalorimeters to magnetic fusion energy research and demonstrate the value of such measurements for fusion. Microcalorimeter spectrometers combine the best characteristics of x-ray instrumentation currently available on fusion devices: high spectral resolution similar to an x-ray crystal spectrometer and broad spectral coverage sufficient to measure impurity species from Be to W. As a proof-of-principle experiment, a NASA-built x-ray microcalorimeter spectrometer has been installed on the Madison Symmetric Torus (MST) at the Wisconsin Plasma Physics Laboratory.

MINFLUX fluorescence nanoscopy in biological tissue.

Optical imaging access to nanometer-level protein distributions in intact tissue is a highly sought-after goal, as it would provide visualization in physiologically relevant contexts. Under the unfavorable signal-to-background conditions of increased absorption and scattering of the excitation and fluorescence light in the complex tissue sample, superresolution fluorescence microscopy methods are severely challenged in attaining precise localization of molecules. We reasoned that the typical use of a confocal detection pinhole in MINFLUX nanoscopy, suppressing background and providing optical sectioning, should facilitate the detection and resolution of single fluorophores even amid scattering and optically challenging tissue environments.

Simultaneous multicolor fluorescence imaging using PSF splitting.

We present a way to encode more information in fluorescence imaging by splitting the original point spread function (PSF), which offers broadband operation and compatibility with other PSF engineering modalities and existing analysis tools. We demonstrate the approach using the 'Circulator', an add-on that encodes the fluorophore emission band into the PSF, enabling simultaneous multicolor super-resolution and single-molecule microscopy using essentially the full field of view.

New Measurement Resolves Key Astrophysical Fe XVII Oscillator Strength Problem.

One of the most enduring and intensively studied problems of x-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA III synchrotron facility by increasing the resolving power 2.5 times and the signal-to-noise ratio thousandfold compared with our previous work.

Calibration of Deformable Mirrors for Open-Loop Control.

Deformable mirrors enable the control of wave fronts for the compensation of aberrations in optical systems and/or for beam scanning. Manufacturers of deformable mirrors typically provide calibration data that encode for the fabrication tolerances among the actuators and mirror segments to support open-loop control with high wave front fidelity and accuracy. We report a calibration method that enables users of the deformable mirrors to measure the response of the mirror itself to validate and improve the calibration data.