A helium beam path for an imaging-plate detector system

A helium beam path for the marresearch imaging plate detector system (X-ray Research GmbH, Norderstedt, Germany) is described. The helium beam path is designed to minimize unwanted air scattering of the primary beam and to reduce absorption of the diffracted beam. The standard marresearch detector system, consisting of the imaging plate detector (online scanner) and the detector base with integrated collimation system, remains unchanged. The beam path consists of a polyethylene bag with the open end fixed to a metal ring. The ring is pressed against the entry window of the imaging plate detector. In this way a sealed volume is created. The primary beam enters into the helium bag through an additional collimating system which is sealed with a thin polyimide window. The crystal and the goniometer head are located inside the helium bag and are connected to the outside spindle axis via a linear and rotary motion feedthrough.