Plasma wakefield diagnostics using probe electron beam and microchannel plates

The analytical and numerical investigations of trajectories of the probe beam electrons in the two dimensional wakefield, excited in plasma by a dense bunch of relativistic electrons with Gauss longitudinal and transverse distribution of density is carried out. On the basis of calculations of probe beam deviations, the diagnostic instrument is developed for parameters of experiments conducted in NSC KIPT. The diagnostic instruments consist of an electron gun forming the electron beam with energy 10 KeV, current 10 μA and diameter 2 mm which passes through the chamber of interaction and falls on a collector of diameter 10 mm. A collector (screen) is placed in front of the first plate of a microchannel amplifier which consists of three microchannel plates (MCP) with sizes 20-30 mm. The voltage of 3 kV was applied to each plate. Total amplification of MCP amplifier is 10⁴-10⁵ in dependence on quantity of particles, falling on the first plate. As a result the deviations of probe beam by excited wakefield the electrons fall on the first plate of the amplifier and are registered by the anode of the amplifier, located behind the third plates. Calculated probe beam deviations and obtained amplification of MCP amplifier permit investigation of the electrical wakefields, excited by the sequence of relativistic bunches (number of particles in bunch is 2·10⁹ , energy is 14 MeV) in plasma of density 10¹¹-10¹³ cm^-3. The maximal value of the fields registered by such a technique is not less 2 kV/cm