The National Ignition Facility modular Kirkpatrick-Baez microscope

Abstract

Current two-dimensional X-ray imaging at the National Ignition Facility (NIF) uses time resolved pinhole cameras with ∼10-25 μm pinholes. This method has limitations in the smallest resolvable features that can be imaged with reasonable photon statistics for inertial confinement fusion (ICF) applications. ICF sources have a broadband self-emission spectrum that causes the pinhole images obtained, through thin foil filters, to contain a similarly broadband spectrum complicating the interpretation of structure in the source. In order to study phenomena on the scale of ∼5 μm, such as dopant mix in the ICF capsule, a narrow energy band, higher spatial resolution microscope system with improved signal/noise has been developed using X-ray optics. Utilizing grazing incidence mirrors in a Kirkpatrick-Baez microscope (KBM) configuration [P. Kirkpatrick and A. V. Baez, J. Opt. Soc. Am. 38, 766-774 (1948)], an X-ray microscope has been designed and fielded on NIF with four imaging channels. The KBM has ∼12 × magnification, <8 μm resolution, and higher throughput in comparison to similar pinhole systems. The first KBM mirrors are coated with a multilayer mirror to allow a "narrow band" energy response at 10.2 keV with ΔE ∼ 3 keV. By adjusting the mirror coating only, the energy response can be matched to the future experimental requirements. Several mirror packs have been commissioned and are interchangeable in the diagnostic snout.

Turbulent hydrodynamics experiments in high energy density plasmas: scientific case and preliminary results of the TurboHEDP project

“…The need of a large (0.5 mm) field of view 2D X-ray imager with the spatial resolution <10 µm has been identified on large scale laser facilities. These capabilities could be achieved with grazing angle-of-incidence mirrors imaging systems like Kirkpatrick-Baez microscopes [44][45][46] , which offer the best solution in terms of resolution versus signal to noise ratio. The X-ray imagers of the LIL facility were all based on the Kirkpatrick-Baez microscope [45] and the first LMJ imager operational in 2014 also works with grazing incidence mirrors [46] .…”

“…The X-ray imagers of the LIL facility were all based on the Kirkpatrick-Baez microscope [45] and the first LMJ imager operational in 2014 also works with grazing incidence mirrors [46] . A high-resolution X-ray imaging diagnostic is operational on the NIF [44] , and under development on LMJ [47] . In the following, we will present a novel diagnostic, based on lithium fluoride detectors.…”

High-resolution X-ray flash radiography of Ti characteristic lines with multilayer Kirkpatrick–Baez microscope at the Shenguang-II Update laser facility

“…A multi-channel KB microscope for long-pulse X-ray imaging is currently being developed. L.A. Pickworth et al are developing a four-channel KB microscope for Ge Heα line (10.2keV) imaging on NIF with a spatial resolution of 4 μm [11] . F.J. Marshall and S.Z.…”

Advanced high resolution x-ray diagnostic for HEDP experiments

“…Fresnel zone plates have been used to measure the spots of XFELs to a precision of 10 s of nm 23 , as well as the X-rays produced in laser target interactions 24 , yet their field of view is only several µm and hence are not compatible with HEDP experiments. Other methods, such as, Kirkpatrick-Baez systems are employed at XFELs 25 or in ICF experiments 26 to achieve a resolution of up to 8 µm, and a field of view on the order of tens of µm, yet for the latter case, this is still not sufficient to provide quality imaging for the capsule implosion. Talbot-Lau interferometers can give access to density gradients in a particular direction, but are still limited to a resolution of several tens of µm 27 and a field of view of less than 1 mm.…”