Anomalous mix induced by a collisionless shock wave in an inertial confinement fusion hohlraum

Abstract

The anomalous mix at the high-Z and low-Z plasma interfaces in an inertial confinement fusion hohlraum is a current topic of interest. The mechanism for such an anomalous mix in the interpenetration layer at the high-Z and low-Z plasma interface and its effects on the laser plasma instabilities have been investigated by particle-in-cell simulations. It is found that a diffusion-driven collisionless shock wave can be generated from an initially sharp high-Z and low-Z plasma interface with total pressure balance and constant temperature in the laser propagation channel. This purely electrostatic shock wave propagates into the high-Z plasma and leads to mix of different species of ions which is significantly faster than a classical mix in the presence of the large electric field. The mix layer width, measured as a separation distance affected by the shock, grows as δd ∝ t α , where α ∼ 1. The effect of the anomalous mix on the linear growth rate of laser plasma instabilities is evaluated.

Enhancement of nuclear reactions via the kinetic Weibel instability in plasmas

“…Note that here the sharp peaks in the cross section profile of the DT reaction are a key factor that is used to achieve the enhancement of nuclear reactions. In astrophysics, many nuclear reactions have such characteristics for the cross section profiles, for example, the 12 C(p, γ) 13 N reaction, one of the most important reactions in stellar nucleosynthesis. According to [43], the cross section of the 12 C(p, γ) 13 N reaction has much more prominent resonance peaks up to several orders of magnitude enhancement.…”

“…In astrophysics, many nuclear reactions have such characteristics for the cross section profiles, for example, the 12 C(p, γ) 13 N reaction, one of the most important reactions in stellar nucleosynthesis. According to [43], the cross section of the 12 C(p, γ) 13 N reaction has much more prominent resonance peaks up to several orders of magnitude enhancement. Assuming that the relative velocity of proton and carbon is 14 000 km s −1 , corresponding to the ⟨σv⟩ i ≈ 1.66 × 10 −27 m 3 s −1 , similarly, as above, we can estimate that the final ion temperature that the colliding plasma can have after evolution is about 370 keV, resulting in ⟨σv⟩ f ≈ 4.13 × 10 −26 m 3 s −1 by 25 times enhancement due to the WI.…”

“…For nuclear reactions in collisional plasmas, such as in the fuel of controlled fusion [1], cores of the stars [5] and/or Big Bang plasmas [4], it is known that the nuclear reaction probability is enhanced due to the highdensity and hightemperature of plasmas [5], where the plasma screening effects also play roles [9][10][11][12]. On the other hand, collisionless plasmas also widely exist in many environments, such as the hohlraum of inertial confinement fusion [13], supernovae remnants [14], γ-ray bursts [15] and solar winds in astrophysics [16], where nuclei collisions can also occur, resulting in nuclear reactions on a rather large spatial scale, though with comparatively low probability. In collisionless plasma, the plasma system can be kept in the nonthermal equilibrium for a long time and particle motions can be modified by self-generated electromagnetic fields, originating from kinetic effects such as the Biermann battery effect and Weibel instability (WI).…”

“…The simulation results show that, for the t(d, n)α reaction, the product yield is enhanced four times due to the WI. For nuclear reactions with more prominent peaks of nuclear resonance, like 12 C(p, γ) 13 N, it is expected that such enhancement can reach up to one or several orders of magnitude.…”

Enhanced Proton Acceleration by Laser-Driven Collisionless Shock in the Near-Critical Density Target Embedding with Solid Nanolayers

“…Ion acceleration via laser-plasma interaction [1] has attracted extensive attention with the rapid development of ultrashort, ultraintense laser technology in recent decades. For its unique characteristics such as high energy and small divergence [2], it has potential scientific applications in a variety of aspects such as inertial confinement fusion (ICF) [3][4][5][6], tumor therapy [7,8], and proton imaging [9,10]. Several mechanisms for laserdriven ion acceleration have been proposed and observed experimentally over the past decades, including target normal sheath acceleration (TNSA) [11,12], radiation pressure acceleration (RPA) [13][14][15], break-out afterburner (BOA) [16,17], magnetic vortex acceleration (MVA) [18,19], and collisionless shock acceleration (CSA) [20][21][22].…”