T. van Oudheusden

Compression of subrelativistic space-charge-dominated electron bunches for single-shot femtosecond electron diffraction.

We demonstrate the compression of 95 keV, space-charge-dominated electron bunches to sub-100 fs durations. These bunches have sufficient charge (200 fC) and are of sufficient quality to capture a diffraction pattern with a single shot, which we demonstrate by a diffraction experiment on a polycrystalline gold foil. Compression is realized by means of velocity bunching by inverting the positive space-charge-induced velocity chirp. This inversion is induced by the oscillatory longitudinal electric field of a 3 GHz radio-frequency cavity. The arrival time jitter is measured to be 80 fs.

Electron source concept for single-shot sub-100 fs electron diffraction in the 100 keV range

We present a method for producing sub-100 fs electron bunches that are suitable for single-shot ultrafast electron diffraction experiments in the 100 keV energy range. A combination of analytical estimates and state-of-the-art particle tracking simulations show that it is possible to create 100 keV, 0.1 pC, 30 fs electron bunches with a spot size smaller than 500 μm and a transverse coherence length of 3 nm, using established technologies in a table-top setup. The system operates in the space-charge dominated regime to produce energy-correlated bunches that are recompressed by radio-frequency techniques. With this approach we overcome the Coulomb expansion of the bunch, providing a single-shot, ultrafast electron diffraction source concept.

3 GHz RF streak camera for diagnosis of sub-100 fs, 100 keV electron bunches

We have designed and built a 3 GHz radio-frequency cavity for use as an ultrafast streak camera to measure with 10 fs resolution the duration of electron bunches that are suitable for single-shot ultrafast electron diffraction experiments. We present our first measurements of 10 ps electron bunches and explain how we will measure sub-100 fs bunch durations.

Single-Shot, Femtosecond Electron Diffraction

High-quality electron diffraction patterns can be recorded in a single sub-picosecond shot by using radio-frequency compression techniques to overcome the Coulomb expansion of the required electron bunches. First single-shot diffraction measurements are presented.