REGAE
Time resolved diffraction with relativistic electrons
Time resolved diffraction with relativistic electrons
Time resolved diffraction with relativistic electrons
REGAE Home
DESY is operating the Relativistic Electron Gun for Atomic Exploration (REGAE) for Ultrafast Electron Diffraction experiments (UED). REGAE is based on a linear accelerator generating ultrashort electron pulses with energies ranging from 2 to 5 MeV, pulse durations below 20 fs, and pulse charges of up typically 100 fC, which are utilized for (time resolved) diffraction experiments. REGAE is capable of operating at repetition rates of up to 50 Hz, but is most of the time operated at 12.5 Hz. The main electron beam parameters of REGAE are summarized in Table 1.
Table 1: Electron beam parameters of REGAE for UED and Electron Diffraction (ED) experiments in fs-timing and microbeam mode.
REGAE can be operated in two different modes: In the ‘fs-timing mode’ for ultrafast electron diffraction experiments, ultrashort electron pulses with a duration down to 20 fs are generated. In addition, a ‘microbeam mode’ is available for experiments, which require a very small electron beam, for example for nano- and microdiffraction and in-situ and operando experiments. Here the charge is spread over several thousands of micro bunches forming a bunch train with a duration of 1.5 µs. For diffraction experiments REGAE is equipped with a large experimental chamber, a fs-laser system for pump-probe experiments, and a highly sensitive 1M-Jungfrau-detector capable of direct electron detection and single shot experiments. An on-axis microscope and a high-precision crystallography goniometer are installed in the experimental chamber.
Basic principle of accelerator-based high-energy electron diffraction: Upon excitation with UV-laser pulses electrons are emitted from a photocathode and immediately accelerated in an RF-gun to energies of 2 – 5 MeV. In a downstream buncher cavity, the electron pulses are compressed to a pulse duration of less than 20 fs before they interact with the sample. The diffraction images are recorded with a Jungfrau 1M detector.