GAMMA RAYS FROM A FREE ELECTRON LASER. Physicists at Duke University scatter ultraviolet photons from 500-MeV electrons inside a free electron laser facility to produce 12-MeV gamma-ray photons. By collimating the gamma flux, one can achieve a nearly monoenergetic beam. The emittance (the divergence) of the beam is so low that even after collimation the intensity of the gamma beam is 1000 times greater than that produced with conventional laser systems. A beam like this will be useful for cancer therapy and for high-precision gamma-ray transmission radiography. It can also be used to produce positrons and to perform sensitive studies of the atomic nucleus. ( Phys. Rev. Lett., 16 June.)