Chopper or zipper?

The answer is “chopper.” This is one of two chopper schemes under development for the Project X Injector Experiment, or PXIE. Particle beams are made of series of particle packets called bunches. The chopper allows scientists to prescribe specific bunch patterns for a particle beam, dictating which bunches can remain in the beam and which have to go. As a particle beam travels down the length of the chopper, each of the rectangular plates lined up along the chopper’s axis sets up an electrostatic pulse that kicks the bunch farther and farther away from the beamline, chopping it out. Photo: Reidar Hahn