Good luck!! It is an absolute blast working in the national labs. Literally
Look at vacuum systems and high voltage lay out. Just getting a "hands touching" on some of that stuff (when the power is removed!!) gives you an excellent feel for how to build things. Feed throughs for power and signals from vacuum chambers, where pumps are, where computers are placed for low noise, what data rates are needed, just about everything is really fun and amazing. Soak it up!!
Radiation safety, shielding, interlocks, 2 phase power conversion, RF supplies in the megawatt (or higher) range, etc., etc., etc.... Simply knowing the state of the art in one area helps you build better stuff in another area because there are links between laboratories that are not obvious.
So good luck, I hope you make it in!