Low Level RF and Timing System Design for the Cool Copper Collider

Abstract

The Cool Copper Collider (C3) is a linear accelerator (LINAC) concept based on compact, high gradient, and normal conducting accelerator technology to support Higgs boson studies at 250 GeV and 550 GeV center of mass. The C3 accelerator is ten kilometers in scale and consist of 2,200 RF stations for 550 GeV center of mass. To maintain the stringent beam quality required by the collider across the LINACs, each of the cavities has a dedicated low-level RF (LLRF) system to stabilize the phase and amplitude of the field in the cavities from pulse to pulse and to compensate the fluctuation of the RF field within each pulse introduced by the beam loading process. To meet the design goals of being compact and affordable for future accelerators, we have designed the next generation LLRF (NG-LLRF) with a higher integration level based on radio frequency system-on-chip (RFSoC) technology. The NG-LLRF system samples RF signals directly and performs RF mixing digitally. The NG-LLRF has been characterized in loopback mode to evaluate the performance of the system and has also been tested with a standing-wave accelerating structure, a prototype structure for the C3 with peak RF power level up to 16.45 MW. This paper will focus on introducing the LLRF system design and timing system for C3 and the current NG-LLRF design. The high-power test results at different stages of the test setup with several pulse modulation schemes, including square pulse, pulse with phase reversals, and pulse trains, will be summarized, analyzed, and discussed.