IN SANDIA'S "Z" MACHINE millions of amps of current are passed through a tiny spool of tungsten wires, producing a flood of x rays. Essentially the most powerful terrestrial producer of x rays, the Z device recently achieved the following milestones during a test shot: temperatures of 1.8 million K, a power output of 290 terawatts, and an energy release of 2.0 megajoules. The researchers believe nuclear fusion could be attained inside the device (by bombarding a fuel pellet with x rays) if the conditions were pushed further, to temperatures of 3.5 million K and power levels of 1000 terawatts. Sandia officials have encapsulated these ideas in a proposal for a larger machine, to be called X-1. (Sandia press release, April 9.)