Compact femtosecond electron diffractometer with 100 keV electron bunches approaching the single-electron pulse duration limit

TL;DR

This paper introduces a compact femtosecond electron diffractometer operating at 100 keV, capable of generating electron pulses with durations approaching single-electron wavepacket limits, enabling ultrafast material dynamics studies.

Contribution

The authors design and simulate a highly compact electron diffractometer that produces near-single-electron pulse durations at high electron energies, advancing ultrafast electron diffraction technology.

Findings

Electron bunches with thousands of electrons are only weakly affected by space-charge effects.

The setup achieves electron pulses below 100 femtoseconds with up to 5000 electrons.

Ultrafast energy transfer in titanium is observed within a few hundred femtoseconds.

Abstract

We present the design and implementation of a highly compact femtosecond electron diffractometer working at electron energies up to 100 keV. We use a multi-body particle tracing code to simulate electron bunch propagation through the setup and to calculate pulse durations at the sample position. Our simulations show that electron bunches containing few thousands of electrons per bunch are only weakly broadened by space-charge effects and their pulse duration is thus close to the one of a single-electron wavepacket. With our compact setup we can create electron bunches containing up to 5000 electrons with a pulse duration below 100 femtoseconds on the sample. We use the diffractometer to track the energy transfer from photoexcited electrons to the lattice in a thin film of titanium. This process takes place on the timescale of few-hundred femtoseconds and a fully equilibrated state is reached within one picosecond.