Energy Calibration of the SPS with Proton and Lead Ion Beams

Abstract

The momentum of the 450 GeV/c proton beam of the CERN Super Proton Synchrotron was determined by a high precision measurement of the revolution frequencies of proton and lead ion beams. To minimize systematic errors the magnetic cycle of the SPS had to be rigorously identical for both beams, and corrections due to Earth tides had to be taken into account. This paper presents how the beam momentum was determined from the RF frequency for which the beams are centred in the machine sextupoles. The measured beam momentum is 449.16 +-0.14 GeV/c for a nominal momentum of 450 GeV/c, and the accuracy is limited by systematic errors. EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH CERN -AB Department Energy Calibration of the SPS with Proton and Lead Ion BeamsJ. Wenninger, G. Arduini, C. Arimatea, T. Bohl, P. Collier, K. Cornelis, CERN, Geneva AbstractThe momentum of the 450 GeV/c proton beam of the CERN Super Proton Synchrotron was determined by a high precision measurement of the revolution frequencies of proton and lead ion beams. To minimize systematic errors the magnetic cycle of the SPS had to be rigorously identical for both beams, and corrections due to Earth tides had to be taken into account. This paper presents how the beam momentum was determined from the RF frequency for which the beams are centered in the machine sextupoles. The measured beam momentum is 449.16 ± 0.14 GeV/c for a nominal momentum of 450 GeV/c, and the accuracy is limited by systematic errors.

Optimal injection voltage in the LHC

“…A good energy matching between the SPS and the LHC is crucial when transferring the beam from the 200 MHz main rf system of the SPS to the half-as-long buckets of the LHC. The calibration and the long-term stability of the beam energy at SPS extraction were studied extensively during the construction of the LHC [19,20]. The original calibration of the SPS dipole field with ion and lowintensity proton beams at 450 GeV showed a reproducibility of 10 −4 in the relative momentum offset, over the timescale of months.…”

Commissioning of the LHC Beam Transfer Line TI 8

“…At the start of the test the energy of the TI 8 line was set to 449.2 GeV, following the energy calibrations done with ions in 2003 [3]. After the beam absorber at the top of TI 8 was moved out, the beam travelled all the way down the transfer line without the need for any beam threading.…”

Optics Studies of the LHC Beam Transfer Line TI 8

“…The momentum of the line was set to 449.2 GeV to match the SPS extraction energy that was measured precisely using Lead ions [2]. Trajectory measurements indicate that the momentum of the extracted SPS beam and the transfer line settings where matched within a few 10 −4 of relative momentum difference, the measurement accuracy being limited by the relatively low sampling of the trajectory by Beam Position Monitors (BPMs).…”