Heating mechanisms in short-pulse laser-driven cone targets.

Area of Science:

• Physics
• Plasma Physics
• Fusion Energy

Background:

• The fast ignitor is a laser fusion approach using short-pulse lasers to initiate thermonuclear burn.
• Relativistic electrons driven by the laser deliver energy to precompressed fusion targets.
• Cones are employed to facilitate laser access to the target core through the surrounding plasma cloud.

Purpose of the Study:

• To investigate the primary mechanisms responsible for peak ion temperatures in recent cone-target experiments within the fast ignitor concept.
• To understand the role of return current joule heating, relativistic electron drag, and magnetic fields in heating fusion targets.

Main Methods:

• Utilized the ANTHEM implicit hybrid simulation model.
• Simulated recent cone-target experiments in the context of fast ignitor laser fusion.

Main Results:

• Peak ion temperatures were found to predominantly originate from return current joule heating.
• Relativistic electron drag provided a mild supplementary heating effect.
• Magnetic fields had a minor impact on overall heating but were crucial for capturing hot electrons and inducing filamentation of the electron stream near the cone surface.

Conclusions:

• Return current joule heating is the dominant mechanism for achieving high ion temperatures in this fast ignitor configuration.
• Magnetic fields play a significant role in electron dynamics, influencing energy deposition and beam propagation.
• These findings are critical for optimizing laser-target coupling and energy transfer in inertial confinement fusion research.