Multibeam seeded brillouin sidescatter in inertial confinement fusion experiments

Area of Science:

• Plasma physics
• Laser-plasma interactions
• Inertial confinement fusion (ICF)

Background:

• Brillouin sidescatter is a significant loss mechanism in ICF.
• Weakly seeded Brillouin sidescatter has not been previously observed or quantified.
• Accurate energy coupling and drive symmetry calculations require understanding all loss processes.

Purpose of the Study:

• To report the first observations of multibeam weakly seeded Brillouin sidescatter in ICF.
• To identify and quantify the mechanisms responsible for seeding Brillouin sidescatter.
• To assess the impact of seeded sidescatter on energy coupling and its potential for diagnostics.

Main Methods:

• Experiments were conducted using indirect-drive ICF.
• Two specific seeding mechanisms were identified: specular reflection (glint) and backscatter from neighboring beams.
• The contributions of each seeding mechanism were quantified.

Main Results:

• Multibeam weakly seeded Brillouin sidescatter was observed and documented.
• Specular reflections (glint) from opposite beams were identified as a primary seeding source.
• Brillouin backscatter from neighboring beams also contributed to seeding.
• Seeded sidescatter was shown to potentially dominate coupling losses.

Conclusions:

• Seeded Brillouin sidescatter is a critical factor in ICF energy coupling.
• Understanding glint and backscatter seeding is essential for accurate ICF performance predictions.
• Glint-seeded scattered light offers a potential new method for probing ICF target hydrodynamics.