1 / 15

SPS: Beam stability and tail population at scrapers

SPS: Beam stability and tail population at scrapers. Lene Drosdal + Verena Kain , Karel Cornelis , Eric Veyrunes …. LIU-SPS-BL-P-TL. Outline. Beam scraping in the SPS for LHC injection Scraper scans to measure beam parameters Stability of beam parameters over time Full beam scan

jeb
Download Presentation

SPS: Beam stability and tail population at scrapers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SPS: Beam stability and tail population at scrapers • LeneDrosdal • +VerenaKain, KarelCornelis, • Eric Veyrunes… • LIU-SPS-BL-P-TL

  2. Outline • Beam scraping in the SPS for LHC injection • Scraper scans to measure beam parameters • Stability of beam parameters over time • Full beam scan • Measurement errors • Stability from 100% scans • Summary and outlook

  3. Beam Scraping • High intensity LHC beams are scraped in the SPS before the end of the ramp (403 GeV) • Typical intensity scraped: 1-3 % SPS cycle with scraping:

  4. LHC Injection Quality • Particles from the tails are lost at the transfer line collimators close to the LHC and can trigger a protection beam dump. For un-scraped beam: • 12 bunches, operational emittance: ~10 % • 12 bunches, nominal emittance (blow-up): ~26 % Injection losses – scrapers out [Injection quality MD 2011]  Not possible to inject full intensity without beam scraping!

  5. Scraping strategy • Correct scraper position: Injection losses can be reduced to an acceptable level while preserving the emittance Injection quality MD 2011 • If beam is stable: Keep scraper fixed at correct position, BUT the scraping is not constant and scrapers need to be moved  Need to investigate stability of beam

  6. Scraper scans • Procedure: Scraper in one plane retracted, the other is moved step-wise towards the beam centre: PLOTS • For each step the scraped intensity is calculated, 3 measurements are used per step • A Gaussian fit is calculated to find the beam size s and beam centre x0 with respect to the scraper

  7. Beam stability 1 • Scraper scans were done throughout May/June: • Beam centre seem to be moving by ~0.7mm BUT.. we assumed that tails are not over-populated and scraping up to ~30% is enough to fit – Only if we assume Gaussian beams!

  8. Beam stability 2 • Scraping at setting: •  Scrapers are moved because beam is changing •  Scraping is not constant Result of beam centre moving or are the beam estimates biased from a large tail population?

  9. Impact of large tail population • If the beam has very large tails the beam size is over-estimated by our fits!  A better fit can be found only using parts of the measurements closer to the core: Fit of all points Cut-off at 60%

  10. Matching with the wire scanners • Using only the beam core (>60%) we match the wire scan measurement: Expected s at scraper location:s = 0.360 * = 0.429

  11. Errors from scraping only until x% • If we scrape only until 30% the beam size is largely overestimated if we have tails! • Beam position also moved by ~0.8 mm  Same magnitude as estimated variations!

  12. Large tails  method break-down • If the tails population is large only a complete scan can be used to estimate the beam parameters and tail population: • Do we always have large tails? • Is the beam position stable? • If we have large tails scraping at a fixed % is also not a sufficient to define the scraper settings • Full beam scans to be repeated • More time consumed than for 30% scans • BLM thresholds need to be opened

  13. Stability from full scans • Scraper scan 9 July: • 36 bunches, horizontal plane • Average intensity per bunch: 1.48 e11 • Scraper position: -8.2mm • Beam size from wire scan: 0.429mm • Fit [50, 100%]: • X0 = -5.925mm • s = 0.453mm • Scraper scan 17 July: • 36 bunches, horizontal plane • Average intensity per bunch: 1.53 e11 • Scraper position: -8.3mm • Beam size from wire scan: 0.462mm • Fit [50, 100%]: • X0 = -6.574mm • s = 0.539mm Beam has moved by ~0.6mm

  14. Vertical plane • Scraper scan 17 July: • 36 bunches, vertical plane • Average intensity per bunch: 1.52 e11 • Scraper position: 3.2mm • Fit [50, 100%]: • X0 = 5.590mm • s = 0.425mm • Only one scan done in the vertical plane: • Large tails also in the vertical plane • Need to check wire scan measurement • Need more scans..

  15. Conclusions & Outlook • Full beam scans show that we have large tails • Necessary to do a full scan to measure beam parameters • Scraping at 1-3% is not sufficient to setup the scrapers • Where are the tails coming from? • The beam centre is moving at the scrapers (H) • Further scans will be done to measure the stability • Orbit stability (BPMs) needs further attention • Use the full beam scan as a tool to estimate the tail population using a double Gaussian fit:I(x) = +

More Related