Emittance growth in coast in the SPS at CERN

F Antoniou,A Alekou,R Calaga,H Bartosik,T Bohl,J Repond,L R Carver,G Vandoni

doi:10.1088/1742-6596/1067/2/022008

Abstract

The HL-LHC prototype crab-cavities are installed in the CERN SPS, which, for the first time, will allow for a comprehensive beam test with high energy protons. As the time available for experimental beam dynamics studies with the crab cavities installed in the machine will be limited, a very good preparation is required. One of the main concerns is the induced emittance growth, driven by phase amplitude jitter in the crab cavities. In this respect, several machine development (MD) studies were performed during the past years to quantify and characterize the long term emittance evolution of proton beams in the SPS. In these proceedings, the experimental observations from past years are summarized and the MD studies from 2016 and 2017 are presented.

Highlights

For the LHC upgrade, the use of a crab-crossing scheme is foreseen, aiming to restore an effective head-on collision at the interaction regions [1, 2]
One of the important concerns that needs to be addressed in the SPS experiments is the induced emittance growth, driven by phase jitter in the crab cavities
Only a limited time will be available for dedicated long-term emittance growth studies, a good preparation in advance is essential for efficient testing

Summary

INTRODUCTION

For the LHC upgrade, the use of a crab-crossing scheme is foreseen, aiming to restore an effective head-on collision at the interaction regions [1, 2]. For this reason, two LHC prototype crab cavities were installed in the SPS during the technical stop at the end of 2017 and will be tested in 2018 in special machine development (MD) sessions. Several MD sessions were devoted in the past years to the long-term emittance growth studies in the SPS [4]. For these experiments special cycles with constant energy at a long plateau were set-up in the SPS, called "coast" beam cycles (with bunched beams). The results from past studies (2010-2015) are summarized and the MD studies of 2016-2017 are presented

PAST STUDIES

Impact of Chromaticity

Other Sources of Emittance Growth

SUMMARY