The first electron diffraction experiments have been successfully performed on VELA. Single shot patterns have been recorded from platinum, gold and aluminium samples with sub-pC of charge transported to the detector screen. Modelling low charge transport in VELA shows that bunch lengths at the current sample position of the order of 100 fs can be achieved with 1 pC charge, but taking the sample closer to the photocathode in future will allow sub-100 fs time resolution. Dr Jonathan Underwood (University College London) states:
“this development should not be understated; with the capability for relativistic electron diffraction at VELA coupled with the synchronized femtosecond laser systems, this instrument will have the ability to take ultrafast snapshots during physical and chemical change of matter at the atomic length scale. This exact capability is being directly targeted internationally by the construction of X-ray FELs (eg. XFEL, LCLS). With these capabilities at VELA, the UK now has the potential to leap-frog those international developments.”
