ELECTRON INJECTIONS FROM A FLOATED PLATE INTO A COLLISIONLESS PLASMA

Measurements are performed on plasma responses to electron injections from a floated emissive endplate into a magnetized collisionless plasm a column produced in a single-ended Q machine. When low-energy and hig h-density electrons are injected, the plate can be charged up positive ly, forming a stable potential barrier to prevent ions from flowing to ward the plate. There appears a drastic increase in the plasma density . In case of high-energy and low-density electrons injected, however, a large electron sheath formed in front of the plate is always accompa nied by a periodic change of plasma structure.