Powder pattern at high pressure and temperatures as low as 20 K can be recorded. Exit windows are made of Al and Be. They contribute to the diffraction pattern and can cause significant overlap or loss of sample diffraction peaks.
- Pressure determination via internal standards.
- Large exit aperture (+/-45 deg) available.
- DAC (p<30GPa) available (opening +/-25deg) and provided by I15
Please contact beam line staff before applying for beamtime.
We use a cryogen-free top loading pulse-tube cryostat. It reaches a base temperature of currently 20K (cooling power is approx 0.3 W at 4.2K). Initial cool-down time is about 6 hours (depending on heat load). The sample (e.g. pressure cell) can easily be changed by removing the dip stick while the cryostat is running. Cool down time of the changed sample is approx. 2 hours. Vibrations of the sample are minimized due to the separation of cold head and rotary valve.
The left image shows the cryostat mounted on the mu-stage of the diffractometer. The cryostat can be moved in x-, y-, and z- direction and rotated by about 3 degree around the vertical axis (phi-rotation). The MAR345 was used to collect the powder pattern. The right image shows the large Be-window attached to the downstream side of the cryostat. With this set-up powder pattern at temperatures as low as 20 K and up to 30 GPa can be collected.
As diamond anvil cell we use the Holzapfel-Syassen type of DAC. It is equipped with diamonds to reach about 30 GPa. Its overall dimensions suit the restrictions implied by the cryostat bore diameter (49mm). It provides an opening angle of about 25 degree.
The image shows the DAC mounted to the cold head.