Development of a Big Area BackLighter for high energy density experiments

Area of Science:

• Physics
• Plasma Physics
• X-ray Science

Background:

• The National Ignition Facility (NIF) requires advanced diagnostics for high energy density (HED) experiments.
• Pinhole-Apertured point-projection Backlighting (PABL) faces spatial limitations in NIF's equatorial plane.
• Unconverted laser light poses risks to PABL components.

Purpose of the Study:

• To develop and characterize a large-area laser-driven X-ray backlighter for NIF.
• To provide an alternative to PABL with a larger field of view.
• To overcome the spatial constraints and risks associated with PABL in the NIF target chamber.

Main Methods:

• Development of the Big Area BackLighter (BABL) with a 7.5 mm² area.
• Illumination of the BABL with 132 kJ of NIF laser energy at 8.52 × 10¹⁴ W/cm² intensity.
• Transmission experiments to evaluate X-ray conversion efficiency and image quality.

Main Results:

• Achieved a conversion efficiency greater than 3.5% into K-shell emission.
• Produced approximately 4.6 kJ of high-energy X-rays.
• Generated high-contrast images with a uniform background, consistent with simulations.

Conclusions:

• The Big Area BackLighter (BABL) is a viable alternative to PABL for NIF HED experiments.
• BABL effectively overcomes the spatial limitations and risks of PABL.
• The developed BABL system demonstrates excellent performance in X-ray generation and imaging.