Picosecond imaging of low-density plasmas by electron deflectometry

Abstract

We have imaged optical-field ionized plasmas with electron densities as low as 10¹³ cm^-3 on a picosecond timescale using ultrashort electron pulses. Electric fields generated by the separation of charges are imprinted on a 20 keV probe electron pulse and reveal a cloud of electrons expanding away from a positively charged plasma core. Our method allows for a direct measurement of the electron energy required to escape the plasma and the total charge. Simulations reproduce the main features of the experiment and allow determination of the energy of the electrons. © 2009 Optical Society of America.