Optimal control of laser plasma instabilities using Spike Trains of Uneven Duration and Delay (STUD pulses) for ICF and IFE

TL;DR

This paper proposes STUD pulses, a novel adaptive laser modulation technique that controls plasma instabilities in ICF and IFE by dynamically adjusting laser intensity profiles to mitigate growth and damage.

Contribution

Introduction of STUD pulses with temporal modulation and speckle scrambling to adaptively control laser plasma instabilities in fusion applications.

Findings

Effective damping of driven waves demonstrated.

Speckle scrambling reduces hot spot recurrence.

Temporal staggering controls beam interactions.

Abstract

An adaptive method of controlling parametric instabilities in laser produced plasmas is proposed. It involves fast temporal modulation of a laser pulse on the fastest instability's amplification time scale, adapting to changing and unknown plasma conditions. These pulses are comprised of on and off sequences having at least one or two orders of magnitude contrast between them. Such laser illumination profiles are called STUD pulses for Spike Trains of Uneven Duration and Delay. The STUD pulse program includes scrambling the speckle patterns spatially in between the laser spikes. The off times allow damping of driven waves. The scrambling of the hot spots allows tens of damping times to elapse before hot spot locations experience recurring high intensity spikes. Damping in the meantime will have healed the scars of past growth. Another unique feature of STUD pulses on crossing beams is that their temporal profiles can be interlaced or staggered, and their interactions thus controlled with an on-off switch and a dimmer.