Effects of ambient plasma md background temperature on the beam-plasma instability and beam-plasma discharge at low pressures in bounded systems

The electrostatic instability of bounded beam-plasma systems as well as its consequences on the ignition of the beam-plasma discharge (BPD) at low pressures and magnetic field strengths are investigated. For this purpose, configurations consisting of a finite radius electron-beam-plasma system whose edge is far away from a confining coaxial metallic container are considered; an ambient, partially ionized gas filling the container is also present. Calculations include threshold conditions, growth rates and ionization-end loss balance conditions; special attention is paid to the effect of ambient plasma as well as to that of background and ambient plasma temperatures. The results obtained explain recent BPD experiments performed under conditions similar to those stated above.