AQS end station

The Atomic-like Quantum Systems (AQS) experimental station is tailored to study fundamental quantum systems, i.e. free atoms or small molecules. The vacuum chamber hosts different spectrometers for detection of charged particles, and, later, also of fluorescence photons.

Two interaction regions spaced by 35 cm allow for different spectrometers to be mounted simultaneously.Rapid changes from one setup to the other can be realized in this way without venting or moving the chamber.

At the upstream position, three identical Electron Time-Of-Flight (eTOF) spectrometers are mounted in the dipole plane (perpendicular to the beam propagation axis), and three further eTOFS are installed in the backward hemisphere for measurements of non-dipole effects. In combination with a fast digitizer, they can record high-resolution electron spectra at the full 4.5 MHz repetition rate.

The vertical (bottom) eTOF can also be used for ion detection when switching the polarity of the applied voltages. All etofs can be operated simultaneously or in coincidence with the VMI spectrometer, enabled by fast switching of the high voltages on the VMI.

A Velocity Map Imaging (VMI) spectrometer is mounted from the top side at the same interaction point as the eTOFs. It can be used to record angle-resolved kinetic energy spectra of (high-energy) electrons. When coupled with a commercial camera, the readout rate is limited to 10 Hz. For single-pulse-resolved electron images, the VMI can be combined with the timestamping Timepix3 camera (click for more infos).

A Magnetic Bottle Electron Spectrometer (MBES) can be mounted in the downstream position of the AQS chamber. The magnetic bottle allows highly efficient time-of-flight spectroscopy of electrons with transmission rates up to 100%. The combination with a Wiley/McLaren ion Time-Of-Flight spectrometer (iTOF) provides the possibility to carry out coincidence measurements of electrons and ions over the full energy range of SQS.

An imaging RIXS spectrometer can be installed in the F1’ focus position of the AQS chamber, replacing the magnetic bottle spectrometer. This imaging spectrometer employs a cylindrical Wolter mirror pair to allow for one dimensional imaging of an extended source. A cylindrical grating mounted in the perpendicular plane provides energy dispersion so that the detector records an image with wavelength dispersion in one direction and spatial resolution in the other. In order to comply with the fixed focal length of the Wolter mirror pair, wavelength range selection is made by repositioning the grating. The spectrometer covers the energy range 140 – 1150 eV using two gratings with 280 lines/mm or 950 lines/mm. The energy resolution is estimated to be about 70 meV at 250 eV and 100 meV at 540 eV. It images a line source of up to 2 mm length with a resolution of 15 µm. The spectrometer will be equipped with a novel 128 channel multi delay-line MCP detector that can acquire frames at the 4.5 MHz rate of the FEL photon burst pattern, allowing one count per pulse per delay line to be detected.

Further information can be found here.