Control of an electron beam using strong magnetic field for efficient core heating in fast ignition

Abstract

Abstract. For enhancing the core heating efficiency in electron-driven fast ignition, we proposed the fast electron beam guiding using externally applied longitudinal magnetic fields. Based on the PIC simulations for the FIREXclass experiments, we demonstrated the sufficient beam guiding performance in the collisional dense plasma by kT-class external magnetic fields for the case with moderate mirror ratio ( 10 ≤ ). Boring of the mirror field was found through the formation of magnetic pipe structure due to the resistive effects, which indicates a possibility of beam guiding in high mirror field for higher laser intensity and/or longer pulse duration.-1-

Study of fast electron generation using multi beam of LFEX-class laser

“…Simply, a large divergence angle does not significantly affect the coupling efficiency if the core is located near the fast electrons generation point, but it strongly affects it if the core is far from the fast electron generation point. Fast electron guiding via external, laser-generated magnetic fields may solve the disadvantage of interference effects [7]. To optimize the target design for fast ignition, these conflicting effects, namely effects of higher absorption and wider fast electron divergence due to interference, should be clarified via full-scale PIC-Hybrid-Hydro simulation under the realistic conditions, including implosion, fast electron generation, and core heating processes.…”

A pathway to laser fusion energy in Japan

“…After the contrast improvement, 50% of the total REB energy is carried by a low energy component of the REB, whose slope temperature is close to the ponderomotive scaling value (~1 MeV). To guide the electron beam, we apply strong external magnetic field to the REB transport region [42][43][44]. Guiding of the REB by 0.6 kT field in a planar geometry has already been demonstrated at LULI 2000 laser facility, in a collaborative experiment lead by CELIA-Univ.…”

Electron beam guiding by external magnetic fields in imploded fuel plasma

“…Such a moderate mirror configuration is feasible for REB guiding and focusing [4]. Such a moderate compression of magnetic field and mirror ratio is due to the lower compression of the fuel target and the high magnetic duffusivity in the cold CD solid region.…”

“…Otherwise, the fast electron escape from the strong magnetic field region (see Fig.2). This requirement is consist with the previous PIC simulations [3,4].…”

“…For improving the efficiency in FIREX project [1], we proposed the REB guiding by externally applied kilo-tesla (kT) -class longitudinal magnetic fields generated by a capacitor-coil target [2] and evaluated its effects by 2D PIC simulations [3,4]. It was demonstrated that the REB with a large divergence angle generated by a relativistic laser plasma interaction with a laser of intensity 3x10 19 W/cm 2 and duration 1 ps can successfully focused by the moderately-converging fields (mirror ratio R M  20) [4]. In addition, formation of a magnetic-pipe like structure due to the resistive effects was shown, which indicates a possibility of the beam focusing even under the higher mirror fields that may be achieved in the ignition-scale or high-gain target implosion.…”