Superconducting Radiofrequency Technology for Accelerators

2 SRF Fundamentals Review

2.1 SRF Basics

We briefly review the key figures of merit that characterize the performance of an SRF cavity or structure, referring the reader to [4, 5] for in-depth coverage. The first important parameter – the accelerating voltage V_c – is the ratio of the maximum energy gain that a particle moving along the cavity axis can achieve, to the charge of that particle. As all existing high-β multicell SRF structures operate in a π standing-wave mode, the optimal length (active length) of the cavity cells is βλ/2. Here λ is the rf wavelength. Next, the accelerating gradient is the ratio of the accelerating voltage per cell to the cell length, or E_acc = V_c/(βλ/2). The cavity quality factor Q₀ determines the number of ...