A large volume plasma device

Abstract

Investigation of highly complex electromagnetic phenomena responsible for fundamental processes in geospace plasma calls for a laboratory device, large enough to provide minimum boundary effects on the electromagnetic waves under concern. The production of large volume, uniform, and quiescent plasma of density ∼1012 cm−3 requires a suitable large area plasma source. The influence of energetic electrons on the phenomena under study can be eliminated using pulsed, highly reproducible discharges so that the afterglow, devoid of energetic electrons, becomes the experimental plasma. Measurement over a large volume with high spatial and temporal resolution, acquisition, and storage of voluminous data form other difficult tasks. The requirement to have tasks of plasma generation, wave excitation, and data acquisition automatically sequenced, also demands a sophisticated control system. A large volume plasma device (LVPD), possessing the following unique features, has been developed in our laboratory: (i) a large area multifilamentary source, (ii) a pulsed power system (width ⩽15 ms and turn off time ≈10 μs), (iii) a three-axes probe drive, (iv) data acquisition and control system with 1 GS/s sampling rate and ≈20 GB memory, and (v) an extended magnet coil system giving desired field profile. The achieved plasma parameters include, ne∼1012 cm−3, Te≈8 eV in the main glow, and ne≈3×1011 cm−3 and Te≈2 eV in the after glow, and plasma uniformity within 5% over 1 m in axial and radial extents. The present article describes the LVPD device.