Ankur Week 2 Post 1

In the last 3 days we completed the first project and are now working on the second project. The first project was very simple, and all we had to do was connect the charcoal trap and storage bottle with stainless steel wires and fittings which is a little challenging because stainless steel is not bendable and flexible like copper wire is. However, stainless steel pieces are cleaner, stronger, more leak-tight, and more durable. Geoffrey introduced me to a new piece of equipment called a "Leak-checker" (at least that's what we call it). 

It is a pretty neat piece of equipment which is used to test the leak-tightness of a system to avoid any contamination. First it pumps down the steel wires and fittings ("pump down" is a common term for "sucks out all the air out of") hence creating a vacuum. Of course, high pressure moves to low pressure. As a result any air that is outside (high pressure) will try its hardest to enter the system (low pressure) through any loose fittings and possible punctures in the system. However, the Leak-checker detects specifically helium down to tiny tiny values. So, we pump down the system to about 10^-3 mbar then use a helium bottle and blow helium on to all the fittings and wire and watch for the Leak-checker to detect hints of helium. Because it's almost instant, we have to pay close attention to see where we were blowing helium in correspondence to the time the Leak-checker detected helium. This was a relatively small system so it only took about 20 minutes. 

We didn't find any substantial leaks so then we pumped down the system with a turbo pump to about 10^-7 mbar. The Leak-checker has a pump as well, but it is not as strong as the Turbo pump so we used the Turbo pump before we passed the gas through the lines. The Turbo pump takes a while, so it must be left for a large amount of time (60-80 minutes) and plus it cannot be touched for 30 minutes after it has finished pumping while it is cooling down. Once there was a good vacuum inside the wires we closed the valves to air so that we would avoid any air contamination.

Finally, we opened the valve from the charcoal trap at about 405psi into the storage bottle which was evacuated (10^-6 mbar = 1.5 x 10^-8 psi). The pressure disparity of course made the argon gas diffuse through the system filling up the storage bottle until pressure equilibrium was reached. Once the two tanks reached equilibrium we closed the valves and disconnected the wires.

We also started some of the plumbing for the 2nd project, however it is much more complex compared to the first project, so I will discuss it in the next post.

Ankur