Ha! I wondered about the tank color, but I wasn't sure, so I glossed over it.

Liquid Helium in an open beaker?

HA Hahahahahahaha!!

It would be gone like that!

LN2 would last at least a little while; it's often used in Physics demonstrations and such. But LHe is nasty stuff to work with, much colder, and would evaporate explosively in an open container. Not to mention far too expensive to waste like that.

Low-temperature Physics labs keep the stuff in very high-quality dewars (basically super-duper thermos bottles) and dole it out with an eyedropper (figuratively speaking).