Abstract

As the multibend achromats had been applied to the lattice design in latest light sources to achieve ultralow beam emittance, whereas its performance is restricted by the strong sextupoles and concomitant nonlinearities to a certain extent. Contractive dynamic aperture becomes an inevitable but pivotal characteristic of future diffraction-limited storage rings, which lead to the exclusion of the conventional off-axis injection schemes. In this paper we will present a new on-axis injection scheme in allusion to future light sources, which is based on a triple-frequency rf system. By means of delicate superposition of rf voltages with fundamental, 2nd and 3rd hamonic frequencies, a commodious and rational main bucket which can accommodate an injected bunch and a circulating bunch simultaneously is able to be formed. The injected bunch can be captured by the longitudinal acceptance on-axis in a reasonable time offset with respect to the circulating bunch, utilizing the ultrafast pulse kicker, and ultimately merging to the center of the main bucket through synchrotron radiation damping. Detailed construction of the triple-frequency rf system and application of this scheme to the High Energy Photon Source will be discussed in the paper, relevant simulation studies and discussions are also presented.

Highlights

  • Along with the increasing newly constructions and upgrade projects of the light source worldwide, it has been become a strong embranchment in the accelerator field, driving the development of corresponding physics and technologies

  • To achieve the ultimate target in this vigorous field, which is alleged diffraction-limited storage ring (DLSR) [1], the innovative multibend achromat (MBA) lattice design [2] and its variants have turned into the requisite approach to beat this target nowadays

  • Through delicately designed the multipole magnet as kicker, quad or higher multipole, which enables the circulating bunches pass through the center of the kicker without disturbance, the injected bunch with a horizontal offset can be kicked appropriately by a special nonlinear pulse waveform, and captured by the horizontal acceptance. Apart from these off-axis injection schemes, more efficient approaches to relax the requirement to the dynamic aperture are the on-axis injection schemes

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Summary

INTRODUCTION

Along with the increasing newly constructions and upgrade projects of the light source worldwide, it has been become a strong embranchment in the accelerator field, driving the development of corresponding physics and technologies. Through delicately designed the multipole magnet as kicker, quad or higher multipole, which enables the circulating bunches pass through the center of the kicker without disturbance, the injected bunch with a horizontal offset can be kicked appropriately by a special nonlinear pulse waveform, and captured by the horizontal acceptance Apart from these off-axis injection schemes, more efficient approaches to relax the requirement to the dynamic aperture are the on-axis injection schemes. Besides it can be injected into the bucket with a designed energy deviation and time offset with respect to the circulating bunch, being described as the “golf club” effect This injection scheme tactfully transfers the pressure from the severe restriction of the dynamic aperture to the pulse kicker design.

THE INJECTION REQUIREMENTS OF HEPS
CONSTRUCTION OF THE TRIPLE-FREQUENCY RF SYSTEM
RELEVANT SIMULATION STUDIES USING THE ABOVE TRIPLE-FREQUENCY
CONSIDERING THE ENERGY LOSS PER TURN RELATED TO THE MOMENTUM DEVIATION
E0 T 0
CONCLUSION
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