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.

Electron time-of-flight spectrometers

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.

 

sample:   gas, from needle or jet
detected particles:   electrons or ions
detector:   MCP, 450 ps timing resolution
maximum rep. rate:   4.5 MHz
kinetic energy range:   10 eV - 5 keV
energy resolution:   70 meV at 800 eV kin. en. (measured)
angles (dipole plane):   0, 90, 54.7
acceptance angle:   0.14% of 4π (different apertures possible)

Velocity map imaging spectrometer

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 either ions or electrons, depending on the polarity of the applied voltages. It is designed such that, when operated in a pulsed mode, it is possible to simultaneously detect electrons with the eTOFs and ions with the VMI.

When coupled with a commercial camera, the readout rate is limited to 10 Hz. Therefore, when using multi-bunch operation, integrated images or images from a single pulse within the train (selected by pulsing the detector bias) have to be recorded. A project to integrate a time-stamping camera, which allows recording single-shot images in the burst mode, is in progress.

 

sample:
  gas, from needle or jet
detected particles:
  electrons or ions
detector:
  MCP + phosphor screen
maximum rep. rate:
  10 Hz with sCMOS camera
kinetic energy range:
  up to 1.2 keV
energy resolution:
  2% measured
  1% simulated
acceptance angle:
  100% of 4π

Magnetic bottle electron spectrometer & ion time-of-flight spectrometer

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.

 

sample:
  gas, from needle or jet
detected particles:
  electrons and ions
detector:
  MCP + phosphor screen
maximum rep. rate:
  4.5 MHz (electrons)
kinetic energy range:
  0 - 3 keV
energy resolution:
  up to 0.2% simulated (MBES)
mass resolution:   up to 1% (iTOF)
acceptance angle:
  up to 100% of 4π