Vienna and nuclear clocks

I have just returned from a visit to Vienna, which was primarily to visit research collaborators at the Vienna University of Technology, but also to visit the city. The city itself is one of the nicest I have been to. Full of history, with interesting buildings everywhere, but still friendly and laid back. I flew from London Heathrow with BA on a direct flight, and because I didn’t know the city, I took a taxi to the hotel. The taxi cost 30 euros, which was reasonable compared with the fast train which I took on the way back (which cost 10 euros per person, and there were 2 of us). However, I can definitely recommend the fast train, the ‘CAT’, which travels from the airport to Wien Mitte station in about 16 minutes!

I only had a day of sight-seeing, but I tried to make the most of it by taking the sightseeing bus tour which enabled me to see most of the important sights of the city in about 2 hours. There are 3 tours which all start from the State Opera, and you can go from one to the next if you wish. I definitely recommend them if you have limited time. Even if you have a few days, doing the tour first gives an idea of the places to be visited, and you can then return to them later.

As for the scientific reason for the visit, I was visiting Dr Thorsten Schumm and his team, who are developing nuclear clocks using 229-Th doped into CaF2. My role is (guess what) to model the material and make predictions about the effects on the material of doping with Th. The calculations are progressing, and we are planning a paper which I will summarise in a later post. But the most exciting thing was that they now have crystals of Th-doped CaF2 (see below). Because of the cost of the 229 isotope (about $5ok/mg), these ‘practice’ crystals were grown using the cheaper 232 isotope, but the principle has now been established, and crystals containing 229-Th will be grown when facilities are available.

The first Thorium doped CaF2 crystal!

The reason for growing these crystals, as I have described previously, is the unusually low nuclear transition of Th-229 which can be excited by vacuum UV radiation, which affords the possibility of time standard devices 6 orders of magnitude more accurate than atomic clocks, which use electronic transitions. By embedding the isotope in a transparent crystal, the development of devices becomes possible. More of this in a future post!