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

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 (10’4-10’5) cme4 were observed throughout the diode during the fmal microsecond of the 2-3 ps electron beam pulse. The neutral density gradient was less than 1 X lo’* cm 4 during the electron beam pulse. Upon diode shorting, neutral density gradients increased to ( 10t81019) cme4 over 1 p.s, and decayed over many microseconds. Plasma density gradients of lOi 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.