Development of a full aperture backscatter system for the Orion laser

Area of Science:

• Laser-plasma interactions
• Inertial confinement fusion diagnostics

Background:

• Scattered light from SBS and SRS can degrade fusion target compression and inhibit ignition.
• Uncontrolled scattered light can lead to hotter electrons and preheating, negatively impacting fusion performance.
• Secondary instabilities, such as two-ion decay, can be triggered by scattered light itself.

Purpose of the Study:

• To develop and implement a Full Aperture Backscatter System (FABS) on the Orion laser.
• To measure scattered light energy resulting from stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) processes.
• To gain insight into laser-plasma instabilities and quantify scattered light losses for improved energy coupling.

Main Methods:

• Collecting backscattered light through the full aperture of the final optic assembly.
• Directing fractions of the collected light to an optics table for measurement.
• Characterizing optical components, including filters and streak cameras, and performing desktop alignment.

Main Results:

• Development of the FABS diagnostic is underway on the Orion laser.
• Progress includes characterization of filters, alignment of optics, and streak camera calibration.
• The system aims to provide quantitative data on SBS and SRS losses.

Conclusions:

• The FABS diagnostic is expected to enhance the plasma diagnostics suite on Orion.
• Quantitative measurements of scattered light will guide efforts to increase energy coupling.
• Understanding and mitigating SBS and SRS is crucial for successful inertial confinement fusion.