* Astronomy

A new calculation shows that x rays, produced at machines planned or under construction, might be convertible into gamma rays or other particles using a process that is analogous to what happens when radio waves strike an antenna. In a conventional antenna, radio waves excite the motion of electrons over an extended region; in a rooftop antenna, for instance, electron interactions with incoming radio waves are spread out over the size of the antenna, typically a meter or more.
The concerted electron excitation is then amplified into a more energetic signal in a tuned circuit in a radio receiver set. Michael Kuchiev, a physicist at the University of New South Wales  has contrived a nuclear equivalent of all this, a process in which x rays can interact in an antenna and be amplified into a new form of energy---in the form of particles. Doing this requires just the right circumstances.
The theory of quantum electrodynamics (QED) suggests that such conversion of laser light, in the vicinity of an atomic nucleus, can occur in strong electric fields on the order of 10^18 V/m and at laser power densities of more than 10^29 W/cm² 2. Such conditions might be reached in upcoming x-ray free electron laser (FEL) facilities.

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