The Gas-phase end station (GPES), shown in the photo below, has been designed for photoelectron-photoion coincidence (PEPICO) experiments of gas phase targets and samples with high vapour pressure [1]. The main instruments are a Scienta R4000 electron spectrometer and a momentum imaging multi-hit-capable ion Time-of-Flight (TOF) spectrometer. They are equipped with fast position-sensitive detectors that are specifically designed for coincidence measurements. The electron and ion spectrometers can also be used independently for high-resolution electron and ion spectroscopy or to collect electron and ion yields as a function of photon energy. The coincidence set-up is controlled by tailor-made software.

The GPES has been designed to accommodate a variety of sample preparation systems, provided by the FinEstBeAMS consortium, LDM group at MAX IV or external users. Available sample delivery systems include a gas inlet with a narrow needle, a vaporisation oven for solid targets, and a liquid microjet source.

A second, exchangeable chamber can be mounted downstream of the electron-ion coincidence set-up. An empty vacuum chamber with a support is available to users whose instruments do not fit or cannot be used in the GPES. It is a replica of the GPES vacuum chamber [1] but without m-metal shielding. This second chamber can be moved to the focal plane of the beamline for the best experimental conditions, when a connection pipe between the GPES and the beamline is removed.

A new setup has been developed for negative-ion/positive-ion coincidence (NIPICO) experiments. It is composed of two TOF spectrometers mounted opposite one another. The TOF spectrometer for positive ions is loaned from the GPES, while the other TOF spectrometer, which is used to detect negative ions, is specifically dedicated to this setup. In NIPICO experiments, the flow of electrons to the detector of negative particles is reduced with an external magnetic field. By removing the magnets, this setup can also be used to measure such PEPICO spectra where it is not necessary to know the kinetic energies of emitted electrons.

Single-bunch operation can be requested on a limited number of beamline commissioning days (Tuesdays). In that operation mode, the time interval between light pulses is 320 ns, instead of the usual 10 ns in the multi-bunch operation. If you want to add a single-bunch day to your regular beamtime proposal, please check the box “23 h Single-bunch operation on Tuesday” as a detector under the selection of the Gas-phase end station during the proposal submission in DUO. Please describe in the proposal what kind of measurements you would like to perform during the single-bunch day and how those measurements will benefit your research. It is not guaranteed that all approved proposals will receive a single-bunch operation day even if it was requested. The final decision will be made after beamtime scheduling and it will depend on the merits of the proposal, the ring operation schedule and willingness of the other beamlines to allow single-bunch operation on beamline commissioning days.

A whole week (30 shifts) of single-bunch operation will be available to users in week 23 of 2021 and perhaps in another week before the end of the cycle (February 2022). If you want to apply for a beamtime in a single-bunch week, you should indicate that clearly in your beamtime proposal. In that case, the scientific motivation of your proposal should be based on the use of single-bunch operation.

Please note that FinEstBeAMS does not have a chopper in the beamline.


[1] K. Kooser et al., J. Synchrotron Rad. 27, 1080 (2020).












Gas-phase endstation at FinEstBeAMS.