Abstract
CERN's Super Proton Synchrotron (SPS) accelerates protons to $450\text{ }\text{ }\mathrm{GeV}/c$ and transfers them into the Large Hadron Collider (LHC). It is currently one of the limiting factors in increasing the beam intensity and thus the luminosity of the LHC. As part of the LHC injectors upgrade project, the SPS 200 MHz rf system has been modified during the CERN long shutdown 2 (January 2019--April 2021), resulting in a new layout containing two additional cavities. The goal is to improve longitudinal stability required for the planned doubling of the beam intensity for the high luminosity LHC. In parallel with the upgrade of the high-power rf, a new low-level rf (LLRF) system has been designed, including a new cavity field regulation system. This work presents a model of the beam-rf interaction which includes a detailed representation of the LLRF controlling the cavity. This model is used to determine the optimal LLRF design for maximum loop stability and beam loading compensation. Finally, the performance of the upgraded LLRF is estimated.
Highlights
The goal is to improve longitudinal stability required by the planned doubling of the beam intensity for the high luminosity Large Hadron Collider (LHC) (HL-LHC) [5]
The one-turn delay feedback (OTFB) (Fig. 1) was designed to cope with this long loop delay. It is a feedback around the cavity/amplifier in which the loop delay has been intentionally extended to one exact turn, and the gain is limited to narrow frequency bands around the revolution harmonics [9]
As part of the LHC injectors upgrade project (LIU), the Super Proton Synchrotron (SPS) rf system has been modified during long shutdown 2 (LS2, January 2019–April 2021), resulting in a new layout containing four three-section and two four-section 200 MHz traveling wave cavities
Summary
The protons accelerated in the LHC first pass through a chain of accelerators, the last of which is the Super Proton Synchrotron (SPS). The high uncompensated transient beam loading leads to significant phase variation along the SPS bunch train, which in turn causes high beam losses during both the beam injection into the SPS and the extraction to the LHC [1]. It is a problem for the phasing of the harmonic cavities (800 MHz) required for beam stabilization through Landau damping [2].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
