Pyroelectric Accelerator

In a pyroelectric crystal held below a critical temperature (the Curie temperature) heating or cooling causes distortions in the lattice of atoms which in turn creates strong electric fields at the surface of the crystal. James Brownridge of the State University of New York at Binghamton (jdbjdb@binghamton.edu) and Stephen Shafroth of the University of North Carolina (919-962-3015, shafroth@physics.unc.edu) have used these electric fields to create stable, self-focused electron beams with energies as high as 170 keV.

The energy conversion is not especially efficient: inputting watts of heating energy produces only microwatts of output electron beam energy, but this might not be important. Pyroelectric crystals (such as those made of LiNbO₃) are widely used as detectors of infrared and THz radiation, but the discovery by Brownridge that they can also be used to produce energetic electron beams if heated or cooled in dilute gas atmospheres means that they can be used to produce x-ray fluorescence for elemental analysis of complex materials, such as tree leaves, rocks, air filters, blood samples, etc. Portable economical x-ray fluorescence is now a real possibility. (Applied Physics Letters, 12 Nov. 2001; also see Brownridge's website.)