Why is a seed material added to the hot gas in an MHD generator?

In a magnetohydrodynamic (MHD) power generator, a seed material is added to the hot gas to increase its electrical conductivity, which is essential for efficient power generation.1

For an MHD generator to operate with good performance and reasonable physical dimensions, the plasma must achieve an adequate electrical conductivity, typically between 10 and 50 siemens per metre. By injecting a small amount—usually about 1 percent by mass—of a readily ionizable alkali material, such as cesium, potassium carbonate, or sodium, the gas becomes sufficiently conductive to interact effectively with the magnetic field. Because the power output of the generator is proportional to this gas conductivity, the use of a seed is critical for creating a competitive and functional energy system.1