Creation and evolution of a low-energy electon beam in a double-plasma device (DPD)

There are plenty of ways to produce electron beams, mostly using electron guns and with beam energies on the order of keV and above. Here, a new method of introducing large cross-section low-energy electron beam (tens of eV) in a DPD is presented. Previous difficulties of producing recognizable beam electrons was the ion sheath near the separation grid in the DPD, which repels electrons from passing through. By blocking out the outer region of the grid (120 mm aperture) and reasonably biasing the voltages on boundaries, a continuous potential rise from the source, through the grid, to the target chamber was achieved, yielding an electron beam, which could be distinguished from the I-V trace of a probe.

The beam energy could be controlled by adjusting the biases on the chamber walls. When the beam energy was around the ionization energy, the beam would propagate a long distance (over 150 mm), although the plasma density was relatively low. If the beam energy substantially exceeded the ionization energy, intense glow discharge was observed and beam would be rapidly dissipated, resulting in higher plasma density.

This study might act as a high efficiency plasma source using low-energy electron beams, which could be used to investigate beam-plasma interactions.