Physical mechanism of ion entrainment by the electron space charge in acceleration by the gradients of static magnetic and of electromagnetic fields

Abstract

A theory of the physical mechanism of ion entrainment by accelerated electrons is presented. It is shown that under the influence of these fields the electrons describe helixes whose diameter and pitch vary along the axis of motion as a function of the difference between the cyclotron frequency and the frequency of the applied hf field. The space charge thus created accelerates the ions. The coupling between the equations of motion of the electron and ion fluids calls for the introduction of a tensor mass; viz., that of the relativistic mass of the electrons in the two equations in x and y describing the transverse movement of the electrons, and that of the ions in the axial motion equation in z. The physical consequences of this theoretical study are then discussed, and three typical experimental results are given that illustrate three of these consequences.

Flux of D+ ions with pléiade

“…II semble done demontre que les structures resonnantes (a) C e= COHF) a champs mixtes (HF -f-magnetique statique) peuvent acceierer des faisceaux de plasma a electrons et ions de forte energie (essentiellement perpendiculaire pour les premiers, axiale pour les seconds). Dans cette derniere mesure du flux et de l'energie des ions, on a recherche pour les deutons avant tout l'obtention d'energie eievee (>20keV), afin d'utiliser les techniques nucieaires pour compieter comme, on l'a dit dans l'introduction, l'eventail des methodes de mesures et confirmer les resultats deja obtenus [1][2][3][4].…”

“…Le montage Pieaide II [2] est une extrapolation de Pieaide I deja decrit dans les publications anterieures [1,3]. La disposition generale des differents elements est la meme (fig.…”

“…Nous avons, dans d'autres publications [1,2], expose en detail le principe et la the"orie d'une structure acce'le'ratrice de plasma (appele"e Pieiade), fondle sur une combinaison de gradients de champs HF et magne"tique statique, et de*crit les dispositifs expe"rimentaux ainsi que les re*sultats obtenus. Deux regimes de fonctionnement distincts ont 6t6 mis en Evidence dans la gamme des pressions infe'rieures a 5 • 10~5 Torr [3], Les moyens de diagnostic utilises dans ces deux regimes permettaient de mesurer sdpariment, d'une part, l'^nergie des ions par un analyseur electrostatique et, d'autre part, les flux globaux de particules (ions -+-Electrons) par des cibles calorime'triques et pyrometriques.…”

Electrostatic stability of gyrating electron streams

“…The instabilities found near £co ge and its harmonics are dangerous if Thus, in general, only for large m is there instability. However, these instabilities are the easiest to control, by a kind of phase mixing if the electron guiding centers do not all lie on the same line of force, or if due to the important charge separation existing in the real machines [9,10] the E o X B o drifts perturb the Larmor helixes into more complicated trajectories.…”

“…The anisotropic velocity distributions [1][2][3][4][5] and the double-stream distributions [6][7][8] may lead to electrostatic (linear) instabilities. Our discussion of the finite radial size of the streams is relevant to experiments at Saclay in the machines Ple"iade and Circe" [9][10].…”