Performance of large electron energy filter in large volume plasma device

Abstract

This paper describes an in-house designed large Electron Energy Filter (EEF) utilized in the Large Volume Plasma Device (LVPD) [S. K. Mattoo, V. P. Anita, L. M. Awasthi, and G. Ravi, Rev. Sci. Instrum. 72, 3864 (2001)] to secure objectives of (a) removing the presence of remnant primary ionizing energetic electrons and the non-thermal electrons, (b) introducing a radial gradient in plasma electron temperature without greatly affecting the radial profile of plasma density, and (c) providing a control on the scale length of gradient in electron temperature. A set of 19 independent coils of EEF make a variable aspect ratio, rectangular solenoid producing a magnetic field (B(x)) of 100 G along its axis and transverse to the ambient axial field (B(z) ~ 6.2 G) of LVPD, when all its coils are used. Outside the EEF, magnetic field reduces rapidly to 1 G at a distance of 20 cm from the center of the solenoid on either side of target and source plasma. The EEF divides LVPD plasma into three distinct regions of source, EEF and target plasma. We report that the target plasma (n(e) ~ 2 × 10(11) cm(-3) and T(e) ~ 2 eV) has no detectable energetic electrons and the radial gradients in its electron temperature can be established with scale length between 50 and 600 cm by controlling EEF magnetic field. Our observations reveal that the role of the EEF magnetic field is manifested by the energy dependence of transverse electron transport and enhanced transport caused by the plasma turbulence in the EEF plasma.

Observation of electromagnetic fluctuation induced particle transport in ETG dominated large laboratory plasma

“…The sandwiched EEF plasma region proposes a complex plasma scenario. We observed that energetic electrons are trapped in the mirror of the solenoid field of the EEF in the source plasma region of LVPD and no trace of these electrons is observed in the target region [36]. The transport across EEF magnetic field helps in producing a plasma profile suitable for the excitation of ETG instability, in axially far-off region, approximately away from the EEF surface.…”

“…Also, establishing an independent control over density and temperature profiles is proved to be a difficult task. We dressed LVPD plasma to meet these requirements by inventing a large-sized electron energy filter [1,36] . The filter is a solenoid having rectangular cross section with 82% transparency and is placed across the diameter of the LVPD.…”

“…A comparison of plasma parameters in the three regions is given in table 1. A detailed description of LVPD, EEF, information about characteristic features of different plasma regions and details of conventional diagnostics is already described in the referred work [32,36,37] . The present study focuses on the target region, where scale length of the gradient in density and electron temperature satisfies the ETG threshold conditions.…”

Investigations into growth of whistlers with energy of energetic electrons

“…The magnet coils are powered with a power supply of capacity 600 A/300 V. A rectangular solenoid with varying aspect ratio but with a constant axial width of 0.04 m, called as electron energy filter (EEF), is installed at the axial center of the device. The EEF [19] produces a strong transverse (B EEF (x) ⊥B z ) magnetic field, B EEF ∼ 0.016 T with respect to the axial magnetic field, B z ∼ −6.2 × 10 −4 T. The EEF redefines the plasma volume in LVPD as source, EEF and target plasma regions. The present investigations are limited to the source plasma region, as marked in figure 1.…”

Plasma potential measurement using centre tapped emissive probe (CTEP) in laboratory plasma

“…x respectively. The pulsed Argon plasma (∆ = t 9.2 ms) is produced at a fill pressure of = × − P 4 10 mbar 4 by using a tungsten based multi-filamentary cathode [23].…”