Total Reflection X-ray Fluorescence attachment module modified for analysis in vacuum

Abstract

Based on the design of the low cost Total Reflection X-Ray Fluorescence attachment module available since 1986 from Atominstitut (WOBRAUSCHEK-Module) which can be attached to existing X-ray equipment, a new version was developed which allows the analysis of samples in vacuum. This design was in particular possible as the Peltier cooled light weight Silicon Drift Detector is following all adjustment procedures for total reflection as angle rotation and lincar motion. The detector is mounted through a vacuum feed and O-ring tightening to the small vacuum chamber. The standard 30 mm round quartz, Si-wafer or Plexiglas reflectors are used to carry the samples. The reflectors are placed on the reference plane with the dried sample down looking facing in about 0,5 mm distance the up looking detector window. The reflectors are resting on 3 steel balls defining precisely the reference plane for the adjustment procedure. As the rotation axis of the module is in the plane of the reflectors surface, angle dependent experiments can be made to distinguish between film and particulate type contamination of samples. Operating with a Mo anode to 50 kV and 40 mA with a closely attached multilayer monochromator and using a 10 mm² KETEK silicon drift detector with 8 γm Be window, a sensitivity of 70 cps/ng for Rb was measuremend and detection limits of 2 pg were obtained.