Enhanced Laboratory X-ray Particle Tracking Velocimetry With Newly Developed Tungsten-Coated O(50 $\mu$m) Tracers

TL;DR

This paper introduces tungsten-coated hollow carbon sphere tracers for X-ray particle tracking velocimetry, demonstrating improved contrast and localization, enabling more precise flow measurements with current photon counting detectors.

Contribution

The study presents a new scalable tracer particle design and validates its effectiveness in laboratory XPTV, showing compatibility with existing photon counting detectors and potential for multi-species tracking.

Findings

W tungsten-coated particles outperform silver-coated tracers in contrast and localization.

Laboratory XPTV is feasible with current photon counting detectors despite lower resolution.

Energy-thresholding can enable multi-tracer and scalar field tracking.

Abstract

Tracer particles designed specifically for X-ray particle tracking and imaging velocimetry (XPTV and XPIV) are necessary to widen the range of flows that can be studied with these techniques. In this study, we demonstrate in-lab XPTV using new, custom-designed $O$(50 $\mu$m) diameter tungsten-coated hollow carbon spheres and a single energy threshold photon counting detector. To explore the measurement quality enhancement enabled by the new tracer particles and photon counting detector, a well understood Poiseulle pipe flow is measured. The data show agreement with the analytical solution for the depth-averaged velocity profile. The experiment also shows that the tungsten-coated particles achieve higher contrast and are better localized than previously available silver-coated particles, making faster and more precise measurements attainable. The particles are manufactured with a readily scalable chemical vapor deposition process. We further show that laboratory XPTV is practical with currently available energy-resolving photon counting detectors (PCDs), despite their presently lower spatiotemporal resolution compared to scintillating detectors. This finding suggests that energy-thresholding identification of different classes of tracers is feasible, further motivating the exploration of the X-ray tracer particle design space. The latest generation of PCDs are incorporating multiple energy thresholds, and have higher count rate limits. In the near future one could potentially expand on the work presented and track multiple tracer species and scalar fields simultaneously.