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SPS Orbit stability: LHC injection quality and transfer lines

SPS Orbit stability: LHC injection quality and transfer lines. Lene Drøsdal. LHC Injection quality. Injection quality is monitored by the IQC – main indictors of injection quality are: Beam losses Transfer line trajectories Injection oscillations (LHC trajectory first turn)

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SPS Orbit stability: LHC injection quality and transfer lines

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  1. SPS Orbit stability: LHC injection quality and transfer lines LeneDrøsdal

  2. LHC Injection quality • Injection quality is monitored by the IQC – main indictors of injection quality are: • Beam losses • Transfer line trajectories • Injection oscillations (LHC trajectory first turn) • Trajectory variations are mitigated by steeringthe transfer lines • Beam losses come from many sources: trajectory offsets, longitudinal distribution, transverse tail population... LIU SPS Orbit Correction Review

  3. SPS orbit variations Two main effects of SPS orbit variations are seen at LHC injection: • SPS orbit variations at extraction cause trajectory variations in LHC and transfer lines • Variations lead to frequent correction of transfer lines • Sources identified by trajectory stability analysis • SPS tail scraping varies due to SPS orbit variations and need to be adjusted to maintain correct scraping LIU SPS Orbit Correction Review

  4. Analysis of Trajectory variations

  5. Transfer line stability • Over time the trajectories in the transfer lines are drifting and the lines need to be corrected • Corrections are done weekly to daily • By analysing uncorrected trajectoriessources of variations can be investigated • From YASP data the corrections are calculated and subtracted from the trajectories • The resulting trajectories are analysed using MIA (Model Independent Analysis) LIU SPS Orbit Correction Review

  6. trajectory variations TI2 – Oct/Nov 2012 TI8 – Oct/Nov 2012 Horizontal plane: Variations of 3mm Vertical plane: Variations of 1mm LIU SPS Orbit Correction Review

  7. Sources of variation I • From the difference trajectories sources of variation can be identified using MIA to find the eigenmodesof variation • For both TI2 and TI8 there are • 2 strong sources in the horizontal plane • 1-2 sources in the vertical plane • The sources are betatron oscillations starting at the beginning of the line  SPS LIU SPS Orbit Correction Review

  8. Sources of variation II By MAD-X simulations of possible errors the sources are identified: • Horizontal plane: • SPS Orbit • MSE (Extraction septum) • Vertical plane: • SPS Orbit • Same sources match for TI2 and TI8 LIU SPS Orbit Correction Review

  9. SPS ORBIT VARIATIONS • Over a period of two weeks orbits were analysed by Hannes/Eliana • Measured orbit variations give trajectory variations around 1 mm • The resulting trajectory variations is a combination the two sources – for a longer time scale the Orbit contribution increase TI2 variations ~5weeks TI2 variations ~1weeks

  10. MSE Current variations • Current variations of the MSE has been identified as the main source of shot-by-shot trajectory variations • The size of the current variations do not grow significantly over time  SPS orbit is the main source of trajectory drifts over time MSE current variations ~3 weeks LIU SPS Orbit Correction Review

  11. SPS TAIL scraping

  12. SPS Scraping • To minimize LHC injection losses from transverse tailsthe beam is scraped in the SPS before extraction • With no scraping losses are high enough to cause an LHC beam dump • 1-2 % of the beam is scraped in each plane • Over time the scraper settings need to be adjusted to maintain correct scraping LIU SPS Orbit Correction Review

  13. Scraper setting variations • Before each fill the scraper settings are checked by the SPS crew • Every 2-3 fills the settings are adjusted • Takes a few minutes • Within each fill the scraper settings are not changed and the amount scraped is stable LIU SPS Orbit Correction Review

  14. SPS orbit variations • In SPS MDs the beams were scanned to monitor beam variations at the scrapers • The measurements show that the changed in scraper settings follow the movement of the beam • During these tests the beam position changed by ~4mm in V and ~1mm in H LIU SPS Orbit Correction Review

  15. Summary • The main effect of SPS orbit variations on injection quality is trajectory drifts • Because of trajectory drifts the transfer lines must be corrected regularly • The MSE also plays a role, but the variations are fast • Due to SPS orbit variations the scraper settings need to be adjusted to maintain correct scraping • Setting need to be checked every fill, but acceptable • During a fill the amount scraped remains stable • Other considerations • Losses at TPSG (from extraction bump)? LIU SPS Orbit Correction Review

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