Euclid TechLabs, LLC, Solon, Ohio, USA
IAP/RAS, Nizhny Novgorod, Russia
Gradients on the order of 1 GV/m have been obtained via single cycle (~1 ps) THz pulses produced by the conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). For electron beam acceleration with such broadband (0.1- 5 THz) pulses, we propose arrays of parabolic focusing micro-mirrors with common central. To measure energy gain of electrons in the THz structure we propose applying a voltage (up to 400 kV) to the structure respecting the cathode and anode. Electrons become preliminary accelerated at the entrance that makes design of the structure simpler, because velocity of particles is near to be constant and almost equals the speed of light. On the other hand, the anode can be reached only by the electrons accelerated in the THz field so that one can directly measure the resulting energy gain at the anode.
Euclid TechLabs, LLC, Solon, Ohio, USA
ANL, Lemont, Illinois, USA
Beam halo measurement is important, because novel x-ray free electron lasers like LCLS-II have very high repetition rates, and the average power in the halo can become destructive to a beamline. Diamond quad detectors were previously used for electron beam halo measurements at KEK*. Diamond is the radiation hard material which can be used to measure the flux of passing particles based on a particle-induced conductivity effect. However, the quad detectors have metallic contacts for charge collection. Their performance degrades over time due to the deterioration of the contacts under electron impact. We recently demonstrated a diamond electrodeless x-ray flux monitor based on a microwave measurement of the change in the resonator coupling and eigen frequency**. We propose similar measurements with a diamond put in a resonator that intercepts the halo. Without electrodes, such a device is more radiation resistant. By measuring the change in RF properties of the resonator, one can infer the beam halo parameters. In a similar manner to traditional beam halo monitors, the diamond plate can be scanned across the beam to map its transverse distribution.
* S.Liu et al., Nuclear Instruments and Methods in Physics Research A832 (2016) 231-242.
** S.Antipov et al., Proceeding of IPAC2018, DOI:10.18429/JACoW-IPAC2018-WEPAF058.