Optimization of the resolution of a streaking setup

Abstract

The combination of a transverse deflecting structure (TDS) and a downstream screen is a well-established setup for the characterization of particle bunch length, detailed current profile, or in conjunction with a dipole spectrometer, the full longitudinal phase space. In low-γ regimes, the inevitable induced energy spread together with longitudinal dispersion during the drift through the TDS can alter the phase space of the particle bunch to be characterized. The consequential bunch lengthening can render measuring ultrashort bunches impossible, even for high available streaking powers and hence theoretical resolution. In this work, the resulting effective resolution of a TDS is estimated analytically and the optimal streaking voltage V_{opt} is determined. The findings are subsequently benchmarked using matrix-based particle tracking. Furthermore, additional transverse, as well as other resolution limiting effects of a realistic streaking setup are discussed. A potential mitigation scheme using an additional downstream focusing element is evaluated. The findings presented in this work can substantially broaden the usable beam energy range of existing TDS setups and overall support the design of new setups.