Lab tasks which make me wish I was a theorist

It’s not all fun and games in the lab. Here is a list of the top 10 (in my opinion) most boring tasks that need doing in a Low Temperature device laboratory:

10.) Chiselling ice off the cold traps
You have to do this otherwise you can’t get them out. Some cold traps are better than others, the ones I have on my fridge aren’t very good, they get iced up quite often.

9.) Adding exchange gas to the IVC.
I use Hydrogen exchange gas, which allows the innards of the vacuum can to cool by conduction and convection, before the temperature gets low enough to freeze out the Hydrogen (at which point it becomes a pretty good vacuum). However, adding it to the IVC is slightly irritating as you need to connect up a vacuum pump, balloon of Hydrogen, etc.

8.) Calibrating thermometers
Thermometry is a pain. Alas, it is also one of the most important parts of the apparatus, as temperature is a rather important variable in most experiments. Writing software calibrations, entering long tables of values, using generic calibrations if you’ve lost the long tables of values….

7.) Making leak-tight He-4 to vacuum feedthroughs.
Stycast is your friend 🙂 They have to be tested by being dipped into a dewar of helium, via a hollow feedthrough rod to which they are soldered in place at one end, whilst the other end is simultaneously connected to a leak detector.

6.) Winding magnets / making superconducting persistent mode magnets
Spot welding superconducting joints for heat switches and winding/potting/quench training magnets – argh!

5.) Making custom filters
Commercial kit just doesn’t work at low temperatures. I’ve had commercial filters fail a few times, and it’s not an easy bug to fix, especially when they only stop working at liquid helium temperatures…

4.) Soldering coaxial cables/adapters
Luckily I now almost exclusively use CuNi cables, which will accept standard solder. Prior to that, stainless steel was the only real option. Soldering to stainless steel is difficult.

3.) Leak testing apparatus
It isn’t fun but it really does need doing each time you remake an Indium seal (for example). The hassle a leak would give you once the apparatus is cold isn’t really worth the few hours it takes to do a leak test.

2.) Fixing leaks in the apparatus
Whilst leak testing is irritating, fixing a leak is even more so. Especially superleaks (leaks that only occur at Liquid He tempertaure). A world of pain.

1.) Filling the fridges
Yep, it’s the most boring job in the world. It takes hours and needs doing every couple of days depending on how hungry your fridge is feeling. Luckily, closed cycle systems are becoming ever more popular. Here’s to a bright, cryogen free future! 🙂

If people can think of any more I’d be happy to add them to the list…