Light emitted from farther away, and thus older, quasars lacked this wavelength, because the light was getting absorbed by neutral helium as well as helium with a single ion-or charged particle.

And He2 plus is observed in helium plasmas at high pressure, He2 but not neutral He2.

The Neutral Beam Injection (NBI) system requires a clean high vacuum environment. The liquid helium cryocondensation pump with high pumping speed is an ideal vacuum obtain device.