Some aspects of laser-produced plasmas

Abstract

This paper reviews progress i n understar,ding some of the mechanisms involved in, and applications of, laser produced plasmas which have been made since the f i r s t observation of the phenomenon some 2 1 years ago. scattering and reflective properties and some spectroscopic applications of pulsed plasmas will be discussed. resonantly tuned lasers will be given. Visual characteristics, formation mechanisms, certainA brief account of work on plasmas initialised and sustained by I&TRODUCTION This year i s the 21st anniversary of the announcement of an entirely new plasma phenomenon.The phenomenon was the production of a plasma in a gas by the action of light alone.The announcement was made almost simultaneously by Maker and his colleagues a t the Third International Congress on Quantum Electronics held i n Paris, and by Meyerand and Haught in the USA, followed quickly by Zeldovich and Raizer i n the USSR.

Plasma boundary phenomena in tokamaks

“…We thus have the prediction that the recycling flux (thus also, for example, the H a light) varies as the square of the plasma density and T P varies inversely as n (assuming D x , etc., constant). Such observations have in fact been reported, at least on large tokamaks such as TFTR [272] and JET [262].…”

“…where R, the global recycling coefficient, is defined by this equation (since r p and T* are experimentally measurable). Experimentally, it is often observed that N(t) scarcely decays when external sources are turned off, T* > 10 s not being uncommon, implying R = 1 [245,262,263]. In order to precisely establish the value of R, and of T P , it is necessary to measure $ as well as N (Eq.…”

“…Up to this point, it has been assumed that a steady state exists, with $ in = $ out , for the walls and limiters. Such conditions can exist during the flat-top (Hg, I p ) part of discharges with a global recycling coefficient of about unity [262] (carbon limiters). During start-up and ramp-down of the discharge, however, $ in y* $ out , generally [262].…”

“…Such conditions can exist during the flat-top (Hg, I p ) part of discharges with a global recycling coefficient of about unity [262] (carbon limiters). During start-up and ramp-down of the discharge, however, $ in y* $ out , generally [262]. In addition, it can be very advantageous (for high T E modes, Section 7.2) to suppress wall recycling during the flat-top by net wall pumping.…”

“Ultracold” Neutral Plasmas at Room Temperature

“…Laser-produced plasmas (LPPs) span a wide range of temperatures and densities [1]. At one extreme, lasers are used to achieve fusion conditions [2] with plasma densities near n = 10 23 cm −3 .…”