Abstract

In order to improve machine performance, the optics parameters of the storage ring need to be measured accurately. The commonly used accelerator optics parameters, including momentum compaction factor and dispersion function, are key parameters that reflect the state of the machine. It is difficult to measure them with traditional methods during the user operation run. Based on a high-resolution bunch-by-bunch three-dimensional measurement system, a noninvasive measurement of momentum compaction factor and the dispersion function was performed at the Shanghai synchrotron radiation facility (SSRF). The dispersion function can be obtained purely from the direct observation results of the bunch-by bunch 3D position, based on the definition of the dispersion function during normal user operation run without perturbing the beam. The theoretical background and experimental results of the method are discussed in this paper. The measurement results are in good agreement with the design values.

Highlights

  • Precise knowledge of key accelerator parameters are important for the analysis of many beam dynamics measurements and user experiments, as well as to tweak the related model of the accelerator [1]

  • In this paper we present a new noninvasive method to measure the momentum compaction factor and dispersion function, based on high-resolution, bunch-by-bunch, threedimensional beam position monitoring (BPM) system

  • We improved the performance of this bunch-by-bunch measurement system, the resolution of longitudinal phase is better than 0.2 ps, the resolution of transverse position is better than 10 μm and the charge resolution is 0.3%

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Summary

INTRODUCTION

Precise knowledge of key accelerator parameters are important for the analysis of many beam dynamics measurements and user experiments, as well as to tweak the related model of the accelerator [1]. The momentum compaction factor and dispersion function cannot be measured noninvasive without disturbing the ordinary light supply of the synchrotron radiation facility by conventional means. The reason is, traditional methods to measure these optics parameters require a large variation of the beam energy and orbit, by altering the rf (radio frequency) frequency, which are incompatible with the daily operation of a synchrotron radiation facility [6,7,8,9]. In this paper we present a new noninvasive method to measure the momentum compaction factor and dispersion function, based on high-resolution, bunch-by-bunch, threedimensional beam position monitoring (BPM) system.

THEORETICAL BACKGROUND
THE MEASUREMENT SYSTEM
EXPERIMENTS RESULTS
Momentum compaction factor
Dispersion function
PERFORMANCE EVALUATION
PROOF EXPERIMENT
Injection transient with empty storage ring
CONCLUSION
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