Physics and engineering of crossed-field discharge devices

Abstract

The physics of devices such as the Penning cell, anode layer ion source, and cylindrical and planar magnetrons is reviewed, with particular emphasis on new developments in the field. These crossed-field discharge devices are specially designed to operate at gas pressures below 10 −2 Torr which makes them attractive for a wide range of applications. Due to effective electron confinement in crossed electric and magnetic fields some of these devices (e.g. inverted magnetron) can even run at pressures as low as 10 −10 Torr. At such low pressures the electron confinement time is much longer than the ion transit time so that the discharge is practically pure electron plasma. The review covers not only the physics of the discharges themselves, but also their interactions with electromagnetic fields. The latter allow additional control over the discharge parameters. Important historical steps in development of E × B discharge devices as well as their characteristics and differences are described and some possible future research directions are discussed.

Boron-rich plasma by high power impulse magnetron sputtering of lanthanum hexaboride

“…Oscillations are indicators for plasma instabilities, and HiPIMS discharges are known to exhibit a wealth of waves and instabilities, 4,16 as do all E×B discharges. 17 The voltage cut off at about -125 V, clearly visible in the 120 A example, is not an artifact. A similar cutoff, albeit about at potential near zero, was also observed in other experiments, 18 however, the explanation invoking the "emergence of emission sites" seems not substantiated.…”

Rotating structures in low temperature magnetized plasmas—insight from particle simulations

“…More details and references can be found in the early review of low pressure magnetically confined discharges by Hooper [1], in the paper on instabilities in low pressure crossed-field devices by Redhead [2] and in the more recent reviews on E × B devices by Keidar and Billis [3], and Abolmasov [4]. Depending on pressure, magnetic field, and applied voltage, different regimes of the discharges in the E × B configurations of Figure 1 can be observed and Abolmassov [4] proposed a classification of these regimes based on the categories defined by Schuurman [5] for Penning discharges. We will not go in the details of this classification here, but we will distinguish two important regimes where the physics and applications are quite different:…”

Centrifugal instability in the regime of fast rotation

“…In laboratory plasmas, this drift can be exploited to fulfil a particular role by adequately tailoring the field topology and strength. For example, the electron E × B drift is key in the efficiency of Hall thrusters 4,5 , Penning plasma sources and magnetron discharges 3 . Another application of crossed field configurations is plasma rotation control, where the field orientation is chosen so that charged particles drift azimuthally.…”