Dedicated beam position monitor pair for model-independent lattice characterization at NSLS-II

Abstract

This paper reports recent lattice characterization results obtained at the National Synchrotron Light Source II (NSLS-II) storage ring, conducted without reliance on a lattice model. A pair of beam position monitors (BPMs) with bunch-by-bunch (B$\times$B) resolution, were recently installed in a section of the storage ring free of magnetic fields. The new BPM pair measured the beam, or bunch's transverse Poincaré map precisely after the beam was excited. Linear one-turn-matrices (OTM) were then derived, and from these, the 4-dimensional coupled Twiss parameters were extracted at the locations of the BPM pair. By normalizing beam oscillation amplitudes with the Twiss parameters, the global action-variables were obtained. These action-variables facilitated the measurement of the local Twiss parameters observed by other BPMs independent on lattice model. This method is general, and particularly useful in certain scenarios such as a round beam mode in a diffraction-limited light source ring. We applied it to assess both weakly and strongly coupled lattices at the NSLS-II ring. Through analysis of the strongly coupled lattice, the quadrupole tilt errors were estimated to be less than 400 \siμrad. Utilizing the BPMs' B$\times$B resolution, for the first time we observed the variations of the linear lattice along a long bunch-train.

28 pages, 16 figures, accepted by Nuclear Inst. and Methods in Physics Research, A

References in corpus (2)

• Betatron motion with coupling of horizontal and vertical degrees of freedom
• Designing linear lattices for round beam in electron storage rings using the solution by linear matrices analysis

Cited by in corpus (3)

• Online regularization of Poincaré map of storage rings with Shannon entropy
• Sextupole reduction via chaos suppression at the National Synchrotron Light Source II
• Coupled Twiss Parameters Estimation from Turn-by-Turn Data