Some experimental observations of the characteristics of hydromagnetic ionizing fronts

SummaryMeasurements of the electron density of a transient hydrogen plasma have been made by a study of the Stark broadening of the emitted Hfl radiation. The plasma is formed by the passage of a strong ionizing shock wave through a neutral gas in the pressure range 100 .;;; p .;;; 400 mtorr. The instantaneous Stark· broadened line profiles have been constructed by simultaneously sampling the light intensities at a number of wavelengths within the Hflline by the use of an eight. channel poly. chromator.It is shown that this approach yields information about the density and homo· geneity of the plasma which is not available from laser interferometer measurements. Evidence is also presented which suggests that the ionizing shock waves presently obtained may have marked snow· plough characteristics.

Section: Optic Axismentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Investigation of the Plasma Produced by a Normal Ionizing Shock Wave Using Polychromator Techniques

Brennan¹,

Fletcher²,

Morrow³

et al. 1969

“…To prepare the plasma, a pulse line of impedance 0·7 Q, charged to +20 kV, is discharged through a series resistance of 1·05 Q to the end electrode; the gas breaks down and a hydromagnetic ionizing shock front, driven by the discharge current of 6·3 kA, travels down the tube. The characteristics of the shock front have been studied here and are reported by Brennan, Brown, et al (1963). Behind the front the plasma is left rotating.…”

Section: Experimental Methods (A) Apparatusmentioning

confidence: 99%

Some Experimental Observations of the Attenuation of Alfven Waves in a Laboratory Plasma

Brown¹

1965

SummaryAn experiment is described in which the velocity and attenuation of torsional, azimuthally symmetric, hydromagnetic waves are measured in a hydrogenous plasma, from low frequencies where ion-neutral collisions are unimportant to the wave damping, to frequencies where such collisions profoundly affect the damping. A theory including both ion-electron and ion-neutral collisions is outlined, and the attenuation results are compared with the theoretical values. An estimate is made, from the frequency dependence of the attenuation, of the hydrogen ion-atom collision cross section for momentum transfer.

“…The equality is exact in a cartesian geometry but not in a cylindrical rotating plasma since for rotational stability and hold on the macroscopic scale (Brennan et al 1963). On the microscopic scale it can be readily shown that the difference between VOi and vOe occurs because of the r -1 dependence of the electric field: ions at radius r have been accelerated in a slightly higher (lower) magnitude E field for Er positive (negative) than have the electrons at that same radius.…”

Section: Ion-neutral Collisionsmentioning

confidence: 99%

Ion Currents, Ion-Neutral Collisions and Plasma Transport Phenomena

Millar¹

1976

It is pointed out that, in the commonly encountered plasma configuration of perpendicular electric and magnetic fields, the Pedersen current (in the E direction) is carried by thtl ions, the Hall current (in the E x B direction) is carried by both ions and electrons in nearly equal and mutually cancelling parts, and the Birkeland current (in the B direction) is carried by the electrons. One of the consequences of the ion current's existence is that the massive ions are accelerated directly by the fields and not, as in a metallic conductor, through momentum transfer from the electrons. Another is that in the presence of a third neutral component of a partially ionized plasma, again a commonly encountered situation, the electron component of the plasma may be in effect collisionless, the ion component collision-dominated, and the plasma resistivity may then be expected to differ markedly from the resistivity calculated on the basis of Coulomb collisions between electrons and ions. It is shown, for example, that the current structure of an ionizing shock may be adequately explained in terms of an ion-carried current subject to a resistivity, determined solely by ion-neutral collisions, of value two orders of magnitude greater than the Coulomb..:collision resistivity. In this, as in the other similarly affected plasma transport phenomenon of diffusion, there is no anomaly nor is there need to invoke plasma instability or filK