N. Baboi

Resolution study of higher-order-mode-based beam position diagnostics using custom-built electronics in strongly coupled 3.9-GHz multi-cavity accelerating module

Beam-excited higher order modes (HOMs) can provide remote diagnostics information of the beam position and cavity misalignment. In this paper we report on recent studies on the resolution with specially selected series of modes with custom-built electronics. This constitutes the first report of measurements of these cavities in which we obtained a resolution of 20 micron in beam offset. Details of the setup of the electronics and HOM measurements are provided.

Higher-Order Mode-Based Cavity Misalignment Measurements at the Free-Electron Laser FLASH

Author(s): Hellert, T; Baboi, N; Shi, L | Abstract:

Erratum: Eigenmode Compendium of the Third Harmonic Module of the European X-ray Free Electron Laser [Phys. Rev. Accel. Beams 20 , 042002 (2017)]

We regret the oversight of not acknowledging the significant amount of work by several colleagues in the field (see [1–4] and references therein). In particular, we would like to highlight the work performed at the Istituto Nazionale di Fisica Nucleare (INFN) for the realization of the third harmonic system of the European XFEL. We are also grateful to W.-D. Möller and E. Vogel from DESY and H. Edwards and T. Khabiboulline from FNAL for facilitating rapid access to the technical drawings of the FLASH third harmonic module ACC39. Based on drawings of the FLASHmodule and articles on the module for the European XFEL such as [5], the CADmodel of the third harmonic cavity string, which is available via [6], was assembled. Furthermore, wewould like to thank the colleagues from INFN and DESY, in particular P. Pierini, E. Vogel and the XFEL operation team for supporting and facilitating our measurements at the third harmonic module during the busy injector commissioning period. We also would like to express our appreciation to J. Chen from INFN for sharing his experience in measured and simulated rf properties of the third harmonic cavities, especially for the modes with field energy strongly localized at the region of the first cell, the main coupler and the nearby beam pipe (see modes with the indices 105 to 112 in the compendium [7]).