A Large Double Plasma Device for Plasma Beam and Wave Studies

The DP (or double plasma) device consists of two essentially collisionless plasmas that are separated from each other (for electrons only) by a negatively biased grid. Large cross section beams of ions are produced in one plasma by raising the potential of the other. Ion waves or shocks are produced in one plasma by oscillatory or large sudden (or ramp) potential changes in the other. Electrons emitted from two electrically separate spatial arrays of small filaments produce the two plasmas with densities in the range from below 10⁸ to ∼10¹⁰ ion/cm³ with noise levels ${\text{〈δn/n〉≈5×10}}^{\text{−4}}$ .