Anomalous neutron yield in indirect-drive inertial-confinement-fusion due to the formation of collisionless shocks in the corona

Abstract

Observations of anomalous neutron yield in the indirect-drive inertial confinement fusion implosion experiments conducted at SG-III prototype and SG-II upgrade laser facilities are interpreted. The anomalous mechanism results in a neutron yield which is 100-times higher than that predicted by 1D radiation-hydrodynamic simulations. 2D radiation-hydrodynamic simulations show that the supersonic, radially directed gold (Au) plasma jets arising from the laser-hohlraum interactions can collide with the carbon-deuterium (CD) corona plasma of the compressed pellet. It is found that in the interaction front of the high-Z jet with the low-Z corona, with low density ∼ − 10 cm 20 3 and high temperature ∼keV, kinetic effects become important. Particle-in-cell simulations indicate that an electrostatic shock wave can be driven when the high-temperature Au jet expands into the low-temperature CD corona. Deuterium ions with an amount of ∼10 15 can be accelerated to ∼25 keV by the collisionless shock wave, thus causing efficient neutron productions though the beam-target method by stopping these energetic ions in the corona. The evaluated neutron yield is consistent with the experiments conducted at SG laser facilities.

On the formation and properties of fluid shocks and collisionless shock waves in astrophysical plasmas

“…Similar situations can be found in the context of inertial confinement fusion (Zhang et al. 2017). While the medium considered here are spatially homogeneous, it would be worth studying how a shock transiting from one kind of medium to another, evolves.…”

“…We leave a detailed study of the spectra expected under various conditions to future work. Similar situations can be found in the context of Inertial Confinement Fusion [55]. While the medium considered here are spatially homogeneous, it would be worth studying how a shock transiting from one kind of medium to another, evolves.…”

Improved numerical simulation model for nuclear reaction rate calculations in high-speed plasma collisions

“…The beam-target reaction and thermonuclear reaction dominate in different stages and the peak neutron yield is 10 3 and 10 5 J −1 , respectively. Zhang et al (2017) observed anomalous neutron yield in indirect-drive ICF, and they attributed it to electrostatic shock wave collisions. Some of the deuterium particles are accelerated to high energy by the electrostatic shock wave and react with centre plasmas by means of the beam-target reaction (Zhang et al 2017;Shan et al 2018).…”

“…Zhang et al (2017) observed anomalous neutron yield in indirect-drive ICF, and they attributed it to electrostatic shock wave collisions. Some of the deuterium particles are accelerated to high energy by the electrostatic shock wave and react with centre plasmas by means of the beam-target reaction (Zhang et al 2017;Shan et al 2018). Other research such as that concerning laser-driven plasma collider (Fu et al 2015) also takes the beam-target reaction into account.…”

“…It is necessary to employ a precise calculation method in order to evaluate quantitatively the importance of the beam-target reaction rate in fusion. However, the traditional method (Yue et al 1993;Perkins et al 2000;He et al 2015;Zhang et al 2017;Shan et al 2018) ignores the transport process and may introduce large errors when the temperature and density along the transport path of incident plasmas vary obviously. An improved method is proposed in this paper, in which we take the transport process into account to eliminate the errors.…”