Long duration backlighter experiments at Omega.

Area of Science:

• High-energy-density physics
• X-ray imaging
• Plasma diagnostics

Background:

• Pinhole-apertured point-projection backlighting is crucial for diagnosing time-evolving phenomena in inertial confinement fusion experiments.
• Existing backlighting techniques require further development to meet the temporal resolution needs of next-generation facilities.

Purpose of the Study:

• To demonstrate a novel pinhole-apertured backlighter with a 7.5 ns duration.
• To assess its suitability for imaging dynamic features in high-energy-density experiments.

Main Methods:

• A backlighter was constructed using a 20 micrometer (µm) diameter pinhole in a 75 µm tantalum substrate.
• A zinc (Zn) emitter (9 keV) was positioned behind the pinhole, separated by a 400 µm high-density carbon (HDC) piece.
• The HDC layer mitigated shock propagation and x-ray ablation of the pinhole substrate.

Main Results:

• A backlighter with a 7.5 ns pulse duration was successfully demonstrated at the Omega laser facility.
• X-ray framing camera images of a gold grid revealed a source-limited resolution significantly smaller than the pinhole diameter, attributed to the pinhole's high aspect ratio.
• Resolution remained consistent at later times, indicating stable performance.

Conclusions:

• The developed pinhole-apertured backlighter meets the 8 ns imaging requirements for experiments at the National Ignition Facility.
• The design effectively minimizes substrate ablation and maintains high resolution, making it a valuable diagnostic tool.