4.5 billion years – this is the unimaginably large number that researchers today estimate to be the age of our Earth. In comparison, the age of geochronology (i.e., the science of the age of the Earth) seems rather modest: Although since the late Middle Ages there have been increasing doubts about the official church doctrine of world creation within 7 days or a world age of about 6,000 years, it would take until well into the twentieth century before scientists were able to develop direct methods for determining the absolute age of rocks.

The first pioneering step on this truly rocky road was taken by a Swedish geologist named Gerard De Geer, who, around the turn of the twentieth century, discovered how to infer the age of a rock by analyzing its annual layers. The discovery of radioactivity finally brought the breakthrough: Among other things, it was discovered that each radioactive isotope has a characteristic half-life such that when it decays, the proportions of the decay products shift predictably with time. If the amount of radiogenic isotopes present in a rock sample is a direct function of time, then the absolute age of the sample can be derived from their ratio! Thus, the radioactive substances naturally occurring in rocks, such as potassium-40 or uranium-235, became the midwives of modern geochronology: What time witnesses and calendar entries are for the historian, the quantity ratios of radioisotopes are for geochronologists.

Professors have entrusted the challenging task of shielding the ultraclean interior of the purification system from the room atmosphere to about a dozen PRECESS all metal valve, several manual PRECESS valves with high-vacuum elastomer seals, and several PRECESS gate valves. The valves separate the different process volumes (laser heating and cleaning chamber, cryogenic concentration volume, pumps) and establish a clear line of separation between the gas processing system and the mass spectrometer itself. Becker explains the underlying challenge: "All these valves have to work absolutely reliably and must not contribute anything to the sample gas themselves. In my experience, PRECESS valves are best suited for this."

Their reliability is no coincidence: PRECESS all-metal valves are baked at up to 350° C during their manufacture, which gives them particularly high purity and extremely low outgassing. For this reason, BGC also relies on the highly efficient PRECESS valve technology for numerous other geochronological analysis instruments. According to the professor, the cooperation between BGC and PRECESS is a long-standing success story: "For example, when we were developing a new high-precision mass spectrometer in 2010, it became apparent at a very early stage of development that impurities were accumulating in the interior of the instrument - too much to ensure the desired measurement accuracy. At that time, a PRECESS expert provided us with very valuable support in finding a solution. Ultimately, the key to solving the problem was a switch to gold-coated PRECESS RING valve disc seals in all process-critical parts of the device. In the standard version, the hard-on-hard sealing gaskets are silver-coated, but in view of the enormously high precision requirements in this device, silver simply proved to be insufficiently inert. This finding may not sound particularly exciting to the interested layperson, but it caused quite a stir in the geochronology community at the time!"