Sunday, October 14, 2012

Lecture announcement: Low Temperature Physics

It's a real pleasure to do the Low Temperature Physics lecture again this winter term. This is a so-called "Modulvorlesung" and "Wahlpflichtfach" (compulsory optional subject?), meaning you'll be able to pick it as examination subject for the MSc physics (possibly also for other courses as e.g. chemistry). Slides are in English, the lecture itself will be in German unless the audience requests otherwise.  In short, we'll be covering the following topics: 
  • properties of cold gases and liquids
  • cryotechnology
  • properties of cold solids (all except superconductivity)
  • superconductivity
  • low-temperature nanophysics
A lot more information can be found on the homepage of the lecture itself. For legal reasons, the slides are only available to participants; I'll tell you the password during the first lecture. So, see you on tuesday morning 8:00ct, PHY 5.0.21!

Wednesday, October 10, 2012

Kudos to Lenovo / IBM service

Since over a year I'm the happy owner of a Lenovo Thinkpad T520, and on the whole I can only recommend it as a power-user Linux machine. Excellent for day-to-day work as well as measurement data processing, Gentoo runs on it nicely, and with a Core i5 and 8G RAM even app-office/libreoffice has lost its horrors. Since I'm travelling often and also tend to working on the weekend in one of these beautiful cafes in the historic city centre of Regensburg, I'm relying on it a lot. So when I bought it, I added a ThinkPlus warranty upgrade to the basket, according to the paperwork 3 years next-workday on-site service for 87€.
The surprise of last friday evening was the laptop's complete refusal to boot. Just some blinking of the power indicator, nothing else. No idea what caused it... Anyway. I started worrying, even took out the harddrive and replaced it with a blank one I had lying around, and prepared myself for being laptop-less for a while.
Called service tuesday morning. A technician called me back wednesday morning, and came along wednesday afternoon. After about 90min, the laptop was completely disassembled, reassembled with a new mainboard and the original hard drive, and worked flawlessly. Yay! One happy customer.

Monday, October 1, 2012

New dilution refrigerator arriving!

We've been waiting patiently for this for quite some time, but now, it seems, our brand new Oxford Instruments Kelvinox HA400 dilution refrigerator is about to arrive in our lab. Yay! The first two boxes are already there... and another seven, I've been told, are on the way from the UK.
The first picture on the right shows the main insert assembly, which is later dipped into a liquid helium-4 bath for precooling. (Remember, we're going to the millikelvin range, so liquid helium-4 at 4.2K is pretty hot.) The lower, copper-coated part of the insert is a vacuum can, the so-called IVC, and inside there, thermally shielded by the vacuum, all the ultra-low temperature cooling goes on. The lower end of this can finally with a slender tail fits into the 3" central bore of a small superconducting magnet. Some experiments which do not need a magnetic field can be conducted directly at the last cooling stage, others are mounted at the center of this tail, i.e. in the center of the magnet.
The second picture shows the actual main cooling circuit, the so-called dilution unit, which will be mounted into the vacuum can when the system is undergoing final assembly. The cooling process is based on the quantum mechanical properties of liquid helium-3 and helium-4 at temperatures below 0.9K; this particular model can reach temperatures down to 7mK (yes that's 0.007 degrees above the absolute zero of temperature). A simplified description of the process can be found on the dilution refrigerator wikipedia page. We'll post some more and nicer pictures once the final assembly is on the way...