Gas Purification System

The purification system is shown in figure . It consisted of commercially available Oxisorb and Hydrosorb filters . The gas was delivered in individual bottles. It was passed through the filters and liquefied into two 220 litre stainless steel barrels. All transfer lines and vessels were carefully cleaned and baked out before use. The complete system was evacuated and leak tested down to mbar l/s to avoid contamination with air during the purification. To remove dust particles coming from the filters, the transfer line in front of the receiving barrels contained a self-made dust filter with a pore size of 0.5 m. Each barrel was mounted inside a Dewar which was filled with liquid nitrogen so that the krypton froze after liquefaction. Liquid nitrogen was automatically topped up during krypton storage. The flow rate of krypton gas through the filters and the pressures before and after the filters of the gas purification system were monitored. In this way, conditions could be kept constant and the amount of liquefied krypton was known.