The Inverse Mode of Thermionic Current Flow from a Hot Cathode Through a Plasma
Abstract
Understanding the plasma and sheaths under intense thermionic current is important for modeling many hot cathode devices. The conventional view is that when the current is space-charge limited (SCL) the cathode sheath consumes the electrode bias and an electric field proportional to the resistivity drives the current through the plasma. In our last GEC talk, we showed that SCL modes cannot exist. Instead, the current-limited equilibrium of a plasma diode should have an inverse cathode sheath. Recently, the unique properties of the inverse current mode were modeled analytically and verified in simulations. Unlike classical or SCL cathode sheath modes, in the inverse mode (a) plasma ions are trapped, (b) the electric field in the plasma is zero, i.e. no field from resistivity or presheath, (c) the anode sheath consumes the electrode bias. Also, the power loss and cathode sputtering can be minimized in the inverse mode, so it may be benificial to design future devices to operate in this mode.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344, and supported by US DOE, Office of Science, Fusion Energy Sciences.- Publication:
-
APS Annual Gaseous Electronics Meeting Abstracts
- Pub Date:
- 2018
- Bibcode:
- 2018APS..GECGT1035C