The medium-energy electron storage ring (3 billion electron-volts) is made up of over 200 long (and a few short) precision machined, extruded aluminum chambers. Each chamber utilizes multiple Atlas bimetal flanges of various sizes, approx. 1500 total, to connect the chambers that comprise the ring. Aluminum was chosen “for the resistive wall impedance for the short bunch electron beam,” says Vacuum Group Leader, Dick Hseuh. “Aluminum is much better than stainless”. In this case, aluminum ultimately wins over high performing copper due to low cost.