Performance limitations of the CERN SPS collider
The SPS has now accumulated more than 10 months of operation as a proton-antiproton collider spread over 3 long physics runs. During this time the peak luminosity has been pushed up to 3.5X10SZ cm Ss and the luminosity lifetime to almost 30 hours. Different physical phenomena limit the machine performance at various times during injection and storage. The peak luminosity is governed by the number of bunches per beam and the emittance and intensity per bunch as well as by the horizontal and vertical beta values at the experimental insertions. Although the transverse emittances and antiproton intensity are defined by the injector chain, the proton bunch intensity is mainly limited by the microwave instability in the SPS itself. The low-beta insertions have been pushed to the limit of available quadrupole strength and chromaticity correction capability at the maximum storage momentum of 315 GeV/c (US /SUB H/ = lm, US /SUB V/ = 0,5m). The luminosity lifetime in the first few hours of storage is limited by the transverse emittance growth of the dense proton bunches due to intrabeam scattering. As the store progresses, the proton bunch decay rate increases due to the growth of the longitudinal emittance (also through intrabeam scattering), finally becoming the dominant contributing factor in governing the luminosity lifetime. The beam-beam interaction limits the usable area in tune space to a very small region free of 10th order resonances. Consequently, the total tune spread must be kept below 0.025, allowing only 3 bunches per beam without separation at the unwanted crossings. Recent work has shown that the behaviour of the weak antiproton beam is quite significantly influenced by tiny periodic parasitic current spikes on the main dipoles.
- Research Organization:
- CERN, Geneva
- OSTI ID:
- 6189169
- Report Number(s):
- CONF-850504-; TRN: 86-004373
- Journal Information:
- IEEE Trans. Nucl. Sci.; (United States), Vol. NS-32:5; Conference: Particle accelerator conference, Vancouver, Canada, 13 May 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANTIPROTON BEAMS
LUMINOSITY
CERN SPS SYNCHROTRON
PERFORMANCE
COLLIDING BEAMS
BEAM BUNCHING
BEAM DYNAMICS
BEAM EMITTANCE
BEAM-BEAM INTERACTIONS
BETA RATIO
INSTABILITY GROWTH RATES
LIFETIME
LIMITING VALUES
PROTON-ANTIPROTON INTERACTIONS
ACCELERATORS
ANTINUCLEON BEAMS
ANTIPARTICLE BEAMS
BARYON-BARYON INTERACTIONS
BEAMS
CYCLIC ACCELERATORS
HADRON-HADRON INTERACTIONS
INTERACTIONS
NUCLEON-ANTINUCLEON INTERACTIONS
OPTICAL PROPERTIES
PARTICLE INTERACTIONS
PHYSICAL PROPERTIES
SYNCHROTRONS
430303* - Particle Accelerators- Experimental Facilities & Equipment
430200 - Particle Accelerators- Beam Dynamics
Field Calculations
& Ion Optics