High field radio frequency (RF) accelerating structures are an essential component of modern linear accelerators (linacs) with applications in photon production and ultrafast electron diffraction. Most advanced designs favor compact, high shunt impedance structures in order to minimize the size and cost of the machines as well as the power consumption. However, breakdown phenomena constitute an intrinsic limitation to high field operation which ultimately affects the performance of a given structure requiring dedicated tests. The introduction of a recent design based on cryogenic distributed coupling structures working at C-band (~6 GHz) allows to increase the shunt impedance by use of alternative distribution schemes for the RF power while mitigating the breakdowns thanks to the low temperature. In this paper we introduce the plan for high field and breakdown tests envisioned for a simple two-cell version of the aforementioned structure. Moreover, we discuss the joining procedure utilized to unify the two fabricated halves of such a structure and relying on the diffusion bonding technique which constitutes an attractive alternative to the brazing approach.

FLASH Therapy, an innovative cancer treatment, minimizes radiation damage to healthy tissue while maintaining the same efficacy in tumor cure as conventional radiotherapy. Successful integration of FLASH therapy into clinical practice, specifically for treating deep-seated tumors with electrons, relies on achieving Very High Electron Energy (VHEE) within the 50-150 MeV range. In collaboration with INFN, Sapienza University actively develops a compact C-band high-gradient VHEE FLASH linac called SAFEST. This paper presents the general layout and the main characteristics of the machine and the first prototype set for deployment at Sapienza University of Rome. This endeavor is a significant step towards the clinical implementation of FLASH Therapy.