Patent ID: 7875867

Claim:
An electron beam generating device, comprising: a first chamber usable to contain a feed gas and a plasma formed using the feed gas, the first chamber having a first end wall having an opening through which the feed gas is able to exit the first chamber; a gas supply tube usable to supply the feed gas into the first chamber, the gas supply tube extending at least into the first chamber; a conductive surface provided within the first chamber, the conductive surface electrically connected to an at least relatively negative potential source that is usable to place an at least relatively negative potential onto the conductive surface; at least one radio-frequency antenna placed around the first chamber and usable to ionize the feed gas within the first chamber to form a plasma; and an electron extraction ring provided adjacent to the first end wall of the first chamber and relative to the opening in the first end wall, the electron extraction ring electrically connected to a reference ground potential source and having an electron extraction aperture, wherein: the potential placed on the conductive surface is negative relative to the plasma and the electron extraction ring; at least an electron sheath forms within the first chamber relative to the electron extraction ring, the electron sheath permitting electrons and neutral particles to pass out of the plasma toward the electron extraction ring and preventing positively-charged ions from moving towards the electron extraction ring; and the electron extraction ring extracts and outputs at least a beam of electrons from the electron beam generating device.