Ultra-bright pulsed electron beam with low longitudinal emittance
View Patent ↗A high-brightness pulsed electron source, which has the potential for many useful applications in electron microscopy, inverse photo-emission, low energy electron scattering experiments, and electron holography has been described. The source makes use of Cs atoms in an atomic beam. The source is cycled beginning with a laser pulse that excites a single Cs atom on average to a band of high-lying Rydberg nP states. The resulting valence electron Rydberg wave packet evolves in a nearly classical Kepler orbit. When the electron reaches apogee, an electric field pulse is applied that ionizes the atom and accelerates the electron away from its parent ion. The collection of electron wave packets thus generated in a series of cycles can occupy a phase volume near the quantum limit and it can possess very high brightness. Each wave packet can exhibit a considerable degree of coherence.
1. A pulsed electron source, comprising:
a beam of neutral atoms;
two lasers intersecting to define, at least partially, an interaction volume, the two lasers capable of causing a first excitation, but not an ionization, of a neutral atom from the beam of neutral atoms;
a pulsed laser at least partially defining the interaction volume, the pulsed laser capable of causing a second excitation of the neutral atom, the second excitation taking the neutral atom to an extreme Rydberg state;
a pulsed voltage source, the voltage source capable of removing an electron from the neutral atom in the extreme Rydberg state; and
an accelerating electric field capable of accelerating the electron to an operating energy.
2. A method of producing a pulsed electron beam, comprising:
a) exciting a neutral atom in an interaction region to an extreme Rydberg state;
b) extracting an electron from the neutral atom in the interaction region when the electron is at orbit apogee, thus creating an ionized atom;
c) removing the electron from the interaction region;
d) removing the ionized atom from the interaction region after step c;
e) accelerating the electron to a desired operating energy, thus producing an electron pulse; and
f) repeating steps a-e to produce a series of electron pulses.