Figure 1: CAES.
From: High-coherence picosecond electron bunches from cold atoms
(a) Schematic representation of the experimental setup11. A shaped 110-fs laser pulse is used to excite a pepper-pot distribution of atoms in the x–y plane, which are subsequently photoionized by a 5-ns laser pulse focused using a cylindrical lens to select a source plane. The electrons are accelerated for 2.5 cm by a 40 kV m−1 electric field, expand under free propagation for 21.5 cm and are imaged using a phosphor-coupled microchannel plate (MCP) detector. (b) Simplified energy-level structure of rubidium. (c) MCP voltage (front ground plane) as electron pulses are detected, for femtosecond excitation (red) 
and for microsecond excitation (blue) 
.
