Picosecond imaging of low-density plasmas by electron deflectometry

Area of Science:

• Plasma Physics
• Ultrafast Science
• Electron Microscopy

Background:

• Optical-field ionized plasmas are crucial in various scientific fields.
• Understanding plasma dynamics requires advanced imaging techniques.
• Previous methods lacked resolution for low-density, picosecond plasmas.

Purpose of the Study:

• To develop and demonstrate a novel imaging technique for ultrafast, low-density plasmas.
• To directly measure electron escape energies and total charge within these plasmas.
• To provide insights into the fundamental physics of charge separation and expansion in plasmas.

Main Methods:

• Utilized ultrashort electron pulses (20 keV) for probing.
• Imaged optical-field ionized plasmas with electron densities as low as 10^13 cm^-3.
• Analyzed the imprint of electric fields on the probe electron pulse to reconstruct plasma properties.

Main Results:

• Successfully imaged picosecond-timescale plasma expansion.
• Revealed electron clouds expanding from positively charged plasma cores.
• Enabled direct measurement of electron energy required for plasma escape.
• Quantified the total charge within the plasma.

Conclusions:

• The developed technique offers a direct and precise method for characterizing ultrafast, low-density plasmas.
• Experimental results were validated by simulations, confirming the energy of escaping electrons.
• This imaging approach advances the study of fundamental plasma processes and charge dynamics.