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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 LeneDrøsdal
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
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
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
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
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
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
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
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
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
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
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
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