Polychromatic drivers for inertial fusion energy

Abstract

Although tremendous achievements have been made toward inertial confinement fusion, laser plasma instabilities (LPIs) remain to be an inevitable problem for current drive schemes. To mitigate these instabilities, significant efforts have been paid to produce high-power broadband ultraviolet lasers. However, no practical scheme has been demonstrated up to now for efficient triple-frequency conversion of broadband laser. Here we propose the design of polychromatic drivers for the generation of multicolor beams mainly based upon the optical parametric amplification, which can significantly enhance the third-harmonic conversion efficiency. Each polychromatic light has four colors of monochromatic beamlets with a full spectrum width of 3\%, and the beamlet colors of any two adjacent flanges are different. The suppression effects of such polychromatic lights have been investigated via large scale particle-in-cell simulations, which indicate that more than 35\% of the incident energy can be saved from the LPIs compared with monochromatic lasers for the direct-drive scheme, or high-density filled target for the indirect-drive scheme. The proposed polychromatic drivers are based on the matured technologies, and thus may pave the way towards realization of robust and high-efficiency fusion ignition.

Control of laser-plasma instabilities by non-collinear polychromatic light

“…The hot electrons are almost completely suppressed by the decoupled NCPLs with δω 0 = 0.7%ω 0 . The cross beams transfer their energies through stimulated IAWs [46,73], where one of the pump beams is a seed light to develop SBS via beating with the other one. The temporal evolutions of the shared ion modes driven by different types of lights are displayed in figure 7(e).…”

“…At present, no practical scheme has been demonstrated for the efficient third-harmonic generation (THG) of broadband lasers [39][40][41][42] because the phase-matching conditions required for THG are difficult to satisfy [43][44][45]. Collinear polychromatic light (CPL) with multicolor beamlet propagation in the same direction was thus proposed [46,47], which can effectively mitigate LPIs without technical obstacles. However, the optical system is complicated and overloaded for practical applications because each CPL requires at least four color collinear beamlets.…”

Simulations of hot electron transport in radiation-ablated plasma

“…[15] Then the advective terms in space and energy are differenced in a conservative form. In our simulation, the hot electron transport module is coupled to the Lagrangian radiation hydrodynamic code MULTI1D, [12] which has been upgraded by using the two-temperature model. The solved hydrodynamic equations in Lagrangian frame are given by…”

“…( 8), which includes laser deposition. [12] Here, electron heat transport is modelled as flux-limited heat transport, and the flux limiter of 0.06. The real equations of state based on an input table are also included.…”

“…In the present work, we use the reduced kinetic model to develop a hot electron transport code, which combines the radiation hydrodynamic code MULTI1D. [12] Then the slowing down process of mono-energetic electron beam is simulated to verify our code. The formation of shock wave driven by hot electrons is also simulated in the dense deuterium tritium (DT) plasma, the ablation pressure is obtained, and the corresponding scaling formula is confirmed in our simulations.…”