Abstract
Radio frequency (rf) accelerating system noise can have a detrimental impact on the Large Hadron Collider (LHC) performance through longitudinal motion and longitudinal emittance growth. A theoretical formalism has been developed to relate the beam and rf station dynamics with the bunch length growth [T. Mastorides et al., Phys. Rev. ST Accel. Beams 13, 102801 (2010)]. Measurements were conducted at LHC to determine the performance limiting rf components and validate the formalism through studies of the beam diffusion dependence on rf noise. As a result, a noise threshold was established for acceptable performance which provides the foundation for beam diffusion estimates for higher energies and intensities. Measurements were also conducted to determine the low level rf noise spectrum and its major contributions, as well as to validate models and simulations of this system.
Highlights
The synchrotron radiation damping in a hadron accelerator is usually very low
The relationship between the energy lost to synchrotron radiation and the noise injected to the beam by the rf accelerating voltage determines the growth of the longitudinal energy spread and longitudinal emittance
The theoretical formalism presented in [1] suggests that the noise experienced by the beam depends on the accelerating voltage phase noise power spectrum, aliased to a band between DC and the first revolution harmonic, due to the periodic sampling of the accelerating voltage Vc by the beam
Summary
The synchrotron radiation damping in a hadron accelerator is usually very low. Particles in the Large Hadron Collider (LHC) lose 7 keV per turn for the nominal energy of 7 TeV. The dependence of the rf accelerating voltage noise spectrum on the low level rf (LLRF) configurations has been predicted using time-domain simulations and models described in [2]. Measurements at the LHC supporting the above theoretical formalism and simulation predictions are presented. This paper follows the work previously presented by the authors in [1,3]
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