E164 & E164X: Purpose

For the past four years, the E157 and E162 collaborations have been studying key issues related to the applicability of plasmas to future high-energy accelerators.  In particular, we have been examing the beam-driven plasma wakefield accelerator (PWFA) scheme and electron/positron focusing by plasmas in the context of an electron-positron linear collider.  This is because plasmas can provide accelerating gradients and focusing forces that are order of magnitude greater than those obtained using conventional technology.

For the E164 & E164X experiments we are working to attain ultrahigh gradient plasma-wakefield acceleration.  Ultrahigh gradient, in this context, refers to peak acceleration gradients of >10 GeV/m.  These accelerating gradients are now possible due to the inclusion of a chicane installed along the linac as well as a dogleg at the beginning of the FFTB.  This chicane and dogleg combination allows us to compress the bunch length of the incoming electron beam from 600 microns (E157 & E162 parameters) down to 50-12 microns for the E164 experiments.  The accelerating gradient of the PWFA is inversely proportional to the square of the bunch length.  So a change in bunch from 600 microns to 12 microns should increase the accelerating gradient by 2500.

We believe that a successful demonstration of this experiment will be a truly significant and defining accomplishment in the advanced accelerator research field.