Physicists Build Super-Powerful Tabletop Particle Accelerator | Popular Science: "We have accelerated about half a billion electrons to 2 gigaelectronvolts over a distance of about 1 inch," Mike Downer, professor of physics says in a statement. "Until now that degree of energy and focus has required a conventional accelerator that stretches more than the length of two football fields. It's a downsizing of a factor of approximately 10,000..."
In order to create electrons of the energy level required to produce these X-rays, the team employed laser-plasma acceleration, which involves firing a brief but intensely powerful laser pulse into a puff of gas, using the Texas Petawatt Laser. Though the method was conceived of in the 1970s, a lack of sufficiently powerful lasers to perform it has kept scientists limited at 1 GeV accelerators.