Ambient pressure instrument POLARIS

Experiments at Polaris a run exclusively in collaboration with the Group of Anders Nilsson at University Stockholm. Please get in touch well in advance with the beam line staff or the Nilsson Group prior to proposal submission!

The POLARIS setup is dedicated to investigate catalytic processes on surfaces and interfaces under realistic conditions; i.e., pressures beyond 1 bar and temperatures up to 450°C during the measurement.

The study of chemical processes in operando conditions is an important field of materials science. HAXPES is expected to provide valuable insights towards an understanding of catalytic chemical transformations at interfaces between solids and liquids or gases. The key requirement here is to probe catalytic surfaces under operational conditions at high gas pressures or at solid-liquid interfaces to detect intermediates and rearrangement of catalytic material itself. For this purpose, the “ambient-pressure” HAXPES setup POLARIS has been developed by the group of Anders Nielsson at Stockholm University. The isntrument of stationed at at P22 and was commissioned in the spring of 2018.

Example of Rh 3d spectra measured during the initial commissioning of the instrument in April 2018. Spectra were recorded at a Helium pressure of 0.01 and 2000 mbar. Please note the short acquisition times.

POLARIS is based on a R4000-Hipp2 electron spectrometer (Scienta Omicron) which combines a high-resolution electron analyzer with a pre-lens to effectively separate the high-pressure regime from the vacuum necessary to run the detector. Windowless operation of the instrument at pressures around and beyond 1 bar is facilitated by a novel pressure-cell design that integrates the front cone of the electron analyzer. Two high-precision manipulators allow positioning the sample in 6 degrees of freedom with sub-μm resolution with respect to the front cone and the X-ray beam. Using a combination of LN2 cooling and laser heating, the temperature of single crystal samples can be controlled from –150 to 950°C. Recently, HAXPES measurements have been achieved at pressures up to 2 bars using He and temperatures up to 450°C, allowing for the study of catalytic reactions under real conditions while the catalytic surface is turning over the reaction.

The POLARIS instrument allows standard sputtering, annealing, and plasma cleaning of samples. It can accommodate electrochemical cells and offers additional ports for customer-dedicated feedthroughs. The formation of reaction products can be followed with a residual gas analyzer being placed in the differential pumping section of the electron analyzer.

Experiments at Polaris a run in exclusively in collaboration with the Group of Anders Nilsson at University Stockholm. Please get in touch well in advance with the beam line staff or the Nilsson Group prior to proposal submission!