LINEAR ELECTRON ACCELERATOR PROJECT.

Research with Mark II and Mark III continued with both accelerators operating reliably. The colliding beams experiment achieved a major break through in that wide angle electron-electron scattering events were observed with a high signal to background ratio. The number of observed events corresponds within a factor of two to the number expected from the experimentally measured beam parameters. Although the rate of events is small it will be sufficient to provide an interesting test of quantum electrodynamics. The beam switchyard for the new target area is now completed to the extent that we are ready for preliminary runs using the new target area. The electron scattering program on Mark II has recently included a study of elastic scattering at 180 degrees. The measurements extend into a region of lower momentum transfer than is conveniently available on Mark II and thus they are a valuable complement to these interesting studies of the static magnetic moments of nuclei. The elastic scattering of electrons from the deuteron at large angles where magnetic scattering dominates, shows an interesting effect which could be the result of meson currents. The effect was first observed using the 180 degrees scattering apparatus at Mark II. A more pronounced effect using Mark III at momentum transfers of about 500 MeVc has now been observed. Author