A technique to control cross-field diffusion of plasma across a transverse magnetic field

Abstract

A study to control charged particle transport across a transverse magnetic field (TMF), popularly known as the magnetic filter in a negative ion source, has been carried out in a double plasma device. In the experimental setup, the TMF placed between the two magnetic cages divides the whole plasma chamber into two distinct regions, viz., the source and the target on the basis of the plasma production and the corresponding electron temperature. The plasma produced in the source region by the filament discharge method diffuses into the target region through the TMF. Data are acquired by the Langmuir probe and are compared in different source configurations, in terms of external biasing applied to metallic plates inserted in the TMF plane but in the orthogonal direction. The effect of the direction of current between the two plates in either polarity of bias in the presence of TMF on the plasma parameters and the cross-field transport of charge particles are discussed.

Effect of cage bias and electron emission on the two-electron temperature groups in a hot cathode discharge

“…The electron-ion collision frequency (ν ei ∼10 6 Hz) and electron-neutral collision frequency (ν en ∼8 × 10 5 Hz) were found to be much less than Ω e . Thus, electrons are strongly magnetized at the region of the magnetic filter [14,19,27].…”

“…To produce plasma, five tungsten filaments of diameter 2 × 10 −4 m and length 0.05 m are used in the source cage. A detailed description of the experimental device is given in the references [14,19,20].…”

“…Hence it follows from equation (3) that when the magnetic field strength and the temperature increase, the cross-field diffusion for electrons decreases. The study of the electron and the ion transportation through the magnetic filter has been done previously and is presented in the following works [19,21,27]. Usually, the plasma in the target region is due to their diffusion from the source region and also due to local ionization in the target region [14,28,29].…”

Observation of electron temperature anisotropy in the magnetic filter of a hot cathode discharge

“…Similar to the magnetic cage, the magnetic filter is also made up of two stainless-steel columns which contain strontium ferrite and whose surface field strength is ∼100 G. The two magnetic columns are tied to the target cage using fiberglass insulation sleeves (figure 1(b)) and made to face each other in such a way that one side of the column is the north pole and the other is the south pole so that the field lines move from the north pole of one column to the south pole of the other, as shown in figure 1(c) [12][13][14][15].…”

A new ion–ion plasma thruster with an annular geometry

“…Inhomogeneous light distribution as well as asymetry in plasma properties and charged particle currents have been observed and studied in several low-pressure partly magnetized discharges operating with electropositive as well as electronegative gases [20][21][22][23]. The key factor for generating an asymmetry is the magnetic field topology.…”