Electron- and ion-beam transportation channel formation by laser ionization based on resonance saturation—LIBORS

Abstract

Articles you may be interested inElectronic processes during ion-beam sputtering of metals studied by resonance laser ionization mass spectrometry AIP Conf.Resonance ionization spectroscopy investigations of electronic processes during ion-beam sputtering of metal atoms AIP Conf.We have been able to show that "laser ionization based on resonance saturation", LIBORS, represents a powerful new form of laser interaction that can be used to efficiently couple laser energy into either a cold gas or a plasma. In essence, the dense population of resonance-state atoms resulting from laser resonance saturation represents both a reservoir of energy that rapidly provides translation energy to the free electrons through superelastic collisions and a large pool of atoms having an ionization energy reduced by the laser photon energy. We show that over a wide range of conditions LIBORS can be superior to both multiphoton ionization and inverse bremsstrahlung by many orders of magnitude. Indeed, LIBORS appears to be particularly well suited to create long plasma channels needed for electronor ion-beam transportation in future inertial fusion schemes. We have estimated that a suitably tuned laser pulse of about 0.7 J and 400-nsec duration should be capable of creating a plasma channel with an electron density of close to 10 15 cm -3 over an area of 0.2 cm 2 for a length of 5 m m sodium vapor of about 0.1 Torr. A similar result should be possible in lithium vapor.

Spectral diagnostic of a resonantly laser created plasma

“…The first mechanism was overlooked in earlier numerical studies of resonant breakdown (Measures et al 1979). When the incoming intensity is large enough, 75% of the atoms are in the 3P state which can be considered as a pseudo-ground state for Boltzmann equilibrium.…”

“…N a = 10 16 cm" 3 , a) T e (t); b) A^t), broken lines: model without energy pooling afterDrewell (1979), solid lines: present model including energy pooling. N a = 10 16 cm" 3 , a) T e (t); b) A^t), broken lines: model without energy pooling afterDrewell (1979), solid lines: present model including energy pooling.…”

Laser-induced plasmas in metal vapors

“…In the above, we have not included a discussion of superelastic electron effects, which are clearly important in short pulse laser-induced plasmas (Measures et al 1979). However, it is very hard to distinguish between the effects of a Na (3p) collision and a superelastic electron collision where the superelastic electron has a kinetic energy equal to the 3s-3p transition energy.…”

Inversions de population lors de la création, par interaction laser résonnante, de plasmas complètement ionisés

“…Un modele numérique permettant de calculer revolution au cours du temps des populations de 20 niveaux atomiques de la densité et de la temperature electronique, avait été conçu et exploite par Measures et al [4]. Mais il ne comporte aucun mecanisme de collisions entre atomes excites au contraire de celui que nous presentons ici.…”

“…En ce qui conceme les collisions entre atomes excites, il existe un certain nombre de mesures sur I'ionisation associative [10, 11, [14]. Sa forme est tres semblable a celle donnee en [4] avec en plus pour les niveaux 3S, 3P, 5S, 4D les termes correspondant aux collisions entre atomes excites. La resolution se fait au moyen d'une methode Runge-Kutta au 3e ordre (schema aux differences centrées) sur un ordinateur IRIS-80.…”