This part is a component of a scintillator-photomultiplier tube detector for a scanning x-ray microscope. The detector converts x-rays into easily measureable electrical signals. Most scanning x-ray microscopes operate at low to moderate vacuum. The light pipes in those instruments are made of a type of transparent plastic, which can be heated up to 80 °C.
The pipes are included in a new microscope, which operate under ultra-high vacuum (UHV) and are occasionally heated to 100 °C. The customer decided to produce the light pipes out of glass because, besides the high temperature resistance, glass is compatible with a clean UHV environment. Other requirements, concerning the internal reflections in the pipe, could also be realized using glass.