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Loss mechanisms

Losses at extraction from SPS LSS4 B.Goddard Input from E.Chapochnikova, W.Hofle, G.Arduini, E.Gaxiola, F.Roncarolo. Loss mechanisms. Scraping of transverse beam tails in H and V planes, on tight septum aperture Particles in the “beam-free” extraction kicker gap. Measured profiles.

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Loss mechanisms

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  1. Losses at extraction from SPS LSS4B.GoddardInput from E.Chapochnikova, W.Hofle, G.Arduini, E.Gaxiola, F.Roncarolo

  2. Loss mechanisms • Scraping of transverse beam tails in H and V planes, on tight septum aperture • Particles in the “beam-free” extraction kicker gap

  3. Measured profiles

  4. Fitted profiles 1s normalised 1s

  5. Settings for extraction MPSH41402.41402[KICK] : 0.0000 MPLH41672.41672[KICK] : 0.5004 MPLH41994.41994[KICK] : 0.3394 MPSH42198.42198[KICK] : 0.1438 MKE1.F[KICK] : 0.110 MKE2.F[KICK] : 0.121 MSE418.F[KICK] : 2.0828 Bump amplitude 31.05 mm at BPCE.41801. Bump amplitude 33.0 mm at QFA.41810. Kicker Voltage 50 kV Opening at TPSG is 49.4 mm. Girder positions: Upstream 47.00 mm Downstream 110.00 mm

  6. Nominal H trajectory ±4 s envelope plotted TPSG diluter MSE septa 1 - 6

  7. Assumptions for loss calculations • Worst-case transverse emittance: factor ~2 above measured values: H: 12p mm.mrad V: 10p mm.mrad • MKE overshoot / ripple: maximum tolerable: ±1.5% • SPS orbit stability: factor ~2 above measured values: ± 0.2 sx/y • Setting-up precision and dynamic mechanical tolerances ± 2 mm

  8. H aperture and losses • Minimum aperture after all tolerances still above 5s. • Total losses <2x106, i.e. <5x10-8 level…seems negligible. • To reach 10-3 losses, ~5.8 mm error in trajectory.

  9. V aperture and losses • Minimum aperture after all tolerances still above 6s. • Total losses <3x102p+, i.e. negligible. • To reach 10-3 losses, ~5.9 mm error in trajectory.

  10. Losses during the extraction gap • 1.05 ms gaps between two PS batches • Gap does not look very clean (PS extraction) • 0.5 - 0.7% of the beam in one of the gaps • Filled bunches near the edges Photo: T.Bohl 9/04

  11. Losses during the extraction gap • Impact TPSG from 33-76% of MKE kick • Central 43% of sweep (bunch 70-160 of 210) • Filled bunches at the edges will scrape • Assuming constant sweep speed and constant 0.7% p+ density in gap • Total of 3x10-3 losses on TPSG • Need to reduce this population to about 0.2% to keep losses at 10-3 level • Lower would of course be better: 0.1%?

  12. Conclusion • Transverse plane : • Expect losses to be below level for nominal operation • Losses approach 10-3 level when trajectory / settings / tolerance errors reach about 5 mm • Extraction gaps • Studies of density profile in gap to complete picture • 0.7 % in gap give losses of about 0.3% on TPSG • Need to reduce population to 0.2 or 0.1% level

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