Tuesday, March 5, 2019
We report our study on the internal dark current generation by multipactor inside a 17 GHz single cell standing wave disk-loaded waveguide accelerator structure. The multipactor takes place on the side wall of the central cell, driven by the local rf electric and magnetic field and marked by sudden formations of electron cloud over the metal surface. Our calculation shows that the multipactor can have several modes turned on at different acceleration gradients and that the electron cloud layer formed does not detune the structure out of resonance. The multipactor modes have been confirmed in the high power experiments and we are working on resolving the energy spectrum of the multipactor dark current by applying probes with dc biasing.