Most lasers are either friendly tabletop devices or so small that you don’t even notice them. But if you want to do something special like image the structure of a delicate protein, you need a very short wavelength and very high-power laser. That means a free electron laser (FEL).
I love FELs, but they’re expensive. A laser produces one beam, and that beam is usually limited to one or two users at a time. So competition for beam time at FELs is fierce. That may be about to change, though. An unexpected experimental result at the Linac Coherent Light Source may be the key to making multiple beams from a single FEL undulator line.
OK, time for some physics-to-almost-English translation. Let’s start with some FEL goodness.