Review of progress in Fast Ignition

Abstract

Marshall Rosenbluth's extensive contributions included seminal analysis of the physics of the laser-plasma interaction and review and advocacy of the inertial fusion program. Over the last decade he avidly followed the efforts of many scientists around the world who have studied Fast Ignition, an alternate form of inertial fusion. In this scheme, the fuel is first compressed by a conventional inertial confinement fusion driver and then ignited by a short ͑ϳ10 ps͒ pulse, high-power laser. Due to technological advances, such short-pulse lasers can focus power equivalent to that produced by the hydrodynamic stagnation of conventional inertial fusion capsules. This review will discuss the ignition requirements and gain curves starting from simple models and then describe how these are modified, as more detailed physics understanding is included. The critical design issues revolve around two questions: How can the compressed fuel be efficiently assembled? And how can power from the driver be delivered efficiently to the ignition region? Schemes to shorten the distance between the critical surface where the ignitor laser energy is nominally deposited and the ignition region will de discussed. The current status of Fast Ignition research is compared with our requirements for success. Future research directions will also be outlined.

The effect of grading the atomic number at resistive guide element interface on magnetic collimation

“…This implies that the product of B / L / needs to be larger than the fast electron momentum to reflect the fast electrons back towards the guide axis. The resistive guide has been suggested for applications such as the Fast Ignition approach to the inertial confinement fusion scheme 6,7 where the energetic fast electrons need to be guided through an overdense stand-off distance of 100 lm or more 8 and deposited into the compressed core of deuterium-tritium (DT) plasma. It has been suggested that a resistive guide element can also be used as a driver in hydrodynamic experiments 4,9 since strong heating occurs where the fast electron beam is collimated.…”

Short-Pulse Laser-Produced Plasmas

“…Recent improvements in particle energy spread [6] may allow compact laser-based radiation sources to be useful someday for cancer hadrontherapy [7] and as injectors into conventional accelerators [8], which are critical tools for x-ray and nuclear physics research. They might also be used for "fast ignition" [9] of inertial fusion targets. The ultrashort pulse duration of these particle bursts and the x rays they can produce, hold great promise as well to resolve chemical, biological or physical reactions on ultrafast time scales and on the spatial scale of atoms [10].…”

Effects of laser temporal profile on fast electron characteristics

“…Many studies have intensively been performed since this proposal [2,3]. In Japan, the FIREX-I project [4] has been started for the sake of heating the core up to the temperature of 5 keV.…”