Calibration of the nonlinear ring model at the Diamond Light Source

Abstract

Nonlinear beam dynamics plays a crucial role in defining the performance of a storage ring. The beam lifetime, the injection efficiency, and the dynamic and momentum apertures available to the beam are optimized during the design phase by a proper optimization of the linear lattice and of the distribution of sextupole families. The correct implementation of the design model, especially the nonlinear part, is a nontrivial accelerator physics task. Several parameters of the nonlinear dynamics can be used to compare the real machine with the model and eventually to correct the accelerator. Most of these parameters are extracted from the analysis of turn-by-turn data after the excitation of betatron oscillations of the particles in the ring. We present the experimental results of the campaign of measurements carried out at the Diamond storage ring to characterize the nonlinear beam dynamics. A combination of frequency map analysis with the detuning with momentum measurements has allowed for a precise calibration of the nonlinear model that can accurately reproduce the nonlinear beam dynamics in Diamond.

On-line control of the nonlinear dynamics for synchrotrons

“…In order to obtain a reasonable signal, the working point must often be moved close to each individual resonance. Although the turn-by-turn beam quality can be improved, and indeed meaningful information on the S01 (S1A) S02 (S1A) S03 (S1A) S04 (S2A) S05 (S2A) S06 (S2A) S07 (S1B) S08 (S1B) S09 (S1B) S10 (S2B) S11 (S2B) S12 (S2B) S13 (S1C) S14 (S1C) S15 (S1C) S16 (S2C) S17 (S2C) S18 (S2C) S19 (S1D) S20 (S1D) S21 (S1D) S22 ( driving terms can be extracted [6][7][8][11][12][13][14][15], we opted for the use of the observed beam loss on a beam current monitor as the main signal, indicating the strength of a resonance. We progressively moved the working point closer to the resonance, using quadrupoles, and adjusted the cosine-and sine terms of the corresponding resonant driving term with the inverted SRM tool and monitored the beam losses.…”

“…Long term stability issues in colliders, and dynamics and momentum aperture enhancement in synchrotron light sources, have stimulated the development of a wealth of techniques to analyze and correct the nonlinear dynamics in storage rings [2][3][4][5][6][7][8].…”

First optics and beam dynamics studies on the MAX IV 3 GeV storage ring

“…Nonlinear tuning by adjusting the three octupole families and/or symmetrization of the five sextupole families (e.g. [40][41][42]) will then be employed to achieve the storage ring's design performance.…”

Characterization of the double-double bend achromat lattice modification to the Diamond Light Source storage ring

“…The amplitude of kick in each plane was increased in steps until the whole beam was lost, and for each kick the turn-by-turn data was recorded from all BPMs for post-processing. The method of converting the raw BPM button data into actual beam position on each turn is described in [20], along with the method for projecting these amplitudes back to the injection point using the model. The dynamic aperture for one such measurement is shown in Fig.…”