PSI, Villigen PSI, Switzerland
In spring 2016 a project was started to renew the high-resolution ARPES endstation of the Surface/Interface Spectroscopy (SIS) beamline at PSI. The focus lay on achieving sample temperatures below 4 K while maintaining 6 degrees of freedom. This made it necessary to redesign all thermally active parts, such as the connection to the cryostat, the flexible braid that enables the tilt and azimuthal movement, the sample clamping as well as the thermal isolators that hold the clamping device in place. A newly introduced shield in the main analyser chamber, cooled by separate cryopumps, is used to remove nearly all radiation heat load. A major milestone has recently been taken, by running cryogenic tests on a test stand. The simplified setup reached sample temperatures of 3.35 K. The temperature loss from the cryostat to the sample was as low as 0.6 K. Encouraged by these results, it is believed that the final endstation will be able to reach temperatures even below 3 K. With the new cryo concept, the thermal performance seems to be mainly limited by the radiative heat load emitted by the analyser lens. The new endstation is planned to be in operation by spring 2019.
