Ultra-low-temperature X-ray data collection with a newly developed 0.1 mm Kapton-film cylinder for a closed-cycle helium cryostat

A 0.1 mm Kapton-film vacuum chamber was constructed to be mounted on the cold head of a closed-cycle helium cryostat. The use of Kapton instead of beryllium results in a low and practically non-structured background, which is thus tolerable on the area-detection frames of modern CCD detectors. The Kapton chamber is only fixed at the upper and lower holders of the cryostat and its counterweight, and is stabilized by spanning with fine pitch threads, holding constant the necessary vacuum of 10⁻⁶ mbar for at least several days. Low costs and non-toxicity are further advantages of this material; moreover, the sample remains visible even after cooling. Data collections on strychnine single crystals at 15 K showed improved I/σ ratios of high-order reflections compared with 100 K data, most favourably when synchrotron primary radiation was used.