Whitehall,

I was surfing around the web and found this:

http://www.freepatentsonline.com/3823325.html

The filing date of the patent was 07/23/1973 (pre-Starwars). The patent assignee was the US Atomic Energy Commission. Here’s the fun bit:

“An x-ray laser utilizing flash-heating of a lasing medium to temperatures of the order of the K-shell binding energy of the medium comprising: means for producing a beam of laser radiation having a pulse of up to about 10-12 seconds, a longitudinally extending lasing medium of material having a diameter of up to about 1 micron and a Z in the range between 2 and 30 and an optical phasing network positioned intermediate said radiation producing means and said lasing medium, said lasing medium being axially aligned with said beam of radiation such that said beam produces flash-heating of said lasing medium producing a traveling heat pulse passing longitudinally along the lasing medium at the group velocity of x-radiation through the heated lasing medium causing a population inversion and lasing of the material.”