Interaction Physics of the Fast Ignitor Concept

Abstract

The interaction of relativistic electrons produced by ultrafast lasers focusing them on strongly precompressed thermonuclear fuel is analytically modeled. Energy loss to target electrons is treated through binary collisions and Langmuir wave excitation. The overall penetration depth is determined by quasielastic and multiple scattering on target ions. It thus appears possible to ignite efficient hot spots in a target with density larger than 300 g/cm 3 . [S0031-9007(96)01191-X]

Evidence of anomalous resistivity for hot electron propagation through a dense fusion core in fast ignition experiments

“…The temperature is consistent with the experimental results estimated from the neutron measurements. It is interesting to see that electrons as energetic as 15 MeV are stopped by the core as shown in figure 2(a), in contradiction to the prevalent notion that only low-energy electrons (up to 1 MeV) can be stopped by a dense core [4]- [7].…”

“…Hopes thus engendered of the feasibility of FI, however, continue to encounter skepticism regarding the appropriate transport of MA electron currents through the tens of microns distance of the compressed core at number densities as high as 10 25 cm −3 . This skepticism is fueled by (a) the considerable existing knowledge of the complexities of relativistic electron transport at normal densities on the one hand and (b) the total paucity of experimental information of transport through high-density cores on the other [4]- [7]. Here we highlight this deficiency by offering direct, quantitative experimental evidence of the fast ignition process.…”

Kinetic model for energy deposition in fast ignition

“…Fast electrons incident into highly overdense core plasmas, the energy loss and deposition to the background is mainly due to collisions [1,2,4]. The collisions between fast electrons and background particles generally fall into two types, namely, the short-range and the long-rang collisions, depending on the impact parameter l. The former refers to the binary Coulomb collisions with impact parameter less than Debye length (l < D ), which is well described by Fokker-Planck (FP) collision operator.…”

“…It has great potential advantages over conventional ICF, notably in relaxing the requirements of implosion symmetry and hydrodynamic instabilities, leading to higher gains with lower driver energy, which has drawn significant attention worldwide [2][3][4][5][6][7][8][9]. In FI scheme, fast electrons generated via ultraintense (∼10 20 W/cm 2 ) short-pulse (∼ 20 ps) laser interaction with plasmas will transport into the pre-compressed dense core to deposit energy locally, forming the hot spot.…”

Self-focusing of a high-intensity laser pulse by a magnetized plasma lens in sub-relativistic regime

“…It has been seen that intense magnetic fields are generated in the laser plasma interaction [5]. These self-generated (or externally applied) transverse and axial magnetic fields affect the propagation of laser pulses in plasmas since the canonical momentum in a magnetized plasma is not conserved [6,7]. Furthermore, laser pulse interaction with magnetized plasmas finds various applications for different branches such as: nonlinear interaction [8], wakefield excitation [9], modulation instability [10,11], laser fusion schemas [12,13], and fast ignition schemes in inertial confinement fusion (ICF) [14].…”