Deflection of carbon dioxide laser and helium‐neon laser beams in a long‐pulse relativistic electron beam diode

Abstract

Deflection of carbon dioxide and helium‐neon laser beams has been used to measure plasma and neutral density gradients during the operating mode and after the shorting time of a long‐pulse field‐emission electron beam diode. Plasma density gradients of (1014–1015) cm−4 were observed throughout the diode during the final microsecond of the 2–3 μs electron beam pulse. The neutral density gradient was less than 1×1018 cm−4 during the electron beam pulse. Upon diode shorting, neutral density gradients increased to (1018–1019) cm−4 over ∼1 μs, and decayed over many microseconds. Plasma density gradients of ∼1015 cm−4 were also observed after shorting. These experiments demonstrate the value of carbon‐dioxide laser and helium‐neon laser deflection for diagnosing plasma and neutral particles in long‐pulse electron beam diodes.