U.S. Particle Accelerator School

Beam-Based Diagnostics course

Sponsoring University:

University of California, Santa Barbara


Beam-Based Diagnostics


David Robin and Christoph Steier, LBNL; James Safranek, SLAC

Charged particle storage rings are used for a variety of science and technology applications --- for example as synchrotron radiation light sources for biology, chemistry, and materials science, as colliders for high-energy physics or as damping rings to reduce the beam emittance for linear colliders. To achieve small equilibrium emittances or to minimize the beam size at the interaction points, strong quadrupoles are necessary to focus the beam, resulting in large chromatic aberrations. The correction of those aberrations requires strong sextupoles creating non-linearities, which can cause the particle motion at large amplitudes to become unstable (dynamic aperture). The dynamic aperture limits the performance in many current accelerators. To optimize the performance, a good knowledge of the machine model is required. To achieve the required accuracy of the machine model, beam based measurements have proven to be essential.

We will present beam-based methods for characterizing and controlling the linear and nonlinear optics of a storage ring. We will cover tune, chromaticity, and dispersion measurement; beam-based alignment; orbit response matrix analysis; analysis of turn-by-turn orbit data; beam size measurement; methods of coupling correction; measurement of dynamic aperture; measurement of energy aperture; characterization of resonances; tune shift with amplitude; model independent analysis; and impedance characterization using turn-by-turn and closed orbit measurements. Prerequisites: understanding of basic accelerator physics, electrodynamics and classical mechanics.