Optics Studies of the LHC Beam Transfer Line TI 8

Abstract

The optics of the newly commissioned LHC beam transfer line TI 8 was studied with beam trajectories, dispersion and profile measurements. Steering magnet response measurements were used to analyze the quality of the steering magnets and of the beam position monitors. A simultaneous fit of the quadrupole strengths was used to search for setting or calibration errors. Residual coupling between the planes was evaluated using high statistics samples of trajectories. Initial conditions for the optics at the entrance of the transfer line were reconstructed from beam profile measurements with Optical Transition Radiation monitors. The paper presents the various analysis methods and their errors. The expected emittance growth arising from optical mismatch into the LHC is evaluated. Large Hadron Collider Project AbstractThe optics of the newly commissioned LHC beam transfer line TI 8 was studied with beam trajectories, dispersion and profile measurements. Steering magnet response measurements were used to analyze the quality of the steering magnets and of the beam position monitors. A simultaneous fit of the quadrupole strengths was used to search for setting or calibration errors. Residual coupling between the planes was evaluated using high statistics samples of trajectories. Initial conditions for the optics at the entrance of the transfer line were reconstructed from beam profile measurements with Optical Transition Radiation monitors. The paper presents the various analysis methods and their errors. The expected emittance growth arising from optical mismatch into the LHC is evaluated.

Commissioning of the LHC Beam Transfer Line TI 8

“…This error in the optics was also identified by the trajectory response measurements. This was corrected for the second test weekend, after which the optics model agreed very well with the measured dispersion and the trajectory response measurements [7].…”

“…Only a brief summary is given here; more details can be found in other PAC05 contributions [6,7,8,9].…”

Expected Emittance Growth and Beam Tail Repopulation-From Errors at Injection into the LHC

“…For the LHC transfer lines κ should be zero, and was measured in 2004 in TI 8 at ∼3% [5]. The resulting emittance increase is 0.05 %.…”

“…The TI 8 tests in 2004 [5] showed that λ could be expected to be corrected to about 1.10. The total mismatch is estimated at 1.15, which includes a 5 % margin for drifts of the LHC optics during the injection process.…”

“…For the effects identified below, each contribution should be below a few %, and the total below 5 The details of the particle distributions are also important, since large tail populations can cause transient losses at injection which risk quenching superconducting magnets. The beams will be scraped to about 3.5 σ in the SPS, but some mismatch effects (for example the geometrical tilt) can lead to significant tail repopulation at large amplitudes, although the effect on the emittance may remain small.…”