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Lessons from SPS MDs in 2010 estimate of potential and needs for low emittances

Lessons from SPS MDs in 2010 estimate of potential and needs for low emittances. E. Shaposhnikova for SPSU SG, SPS RF team and … LIU Session/Chamonix2011 10.11.2010. SPS MDs in 2010 (related to the upgrade). Nominal LHC beam 25 ns, 50 ns, 75 ns, (150 ns) spacings

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Lessons from SPS MDs in 2010 estimate of potential and needs for low emittances

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  1. Lessonsfrom SPS MDs in 2010estimate of potential and needs for lowemittances E. Shaposhnikova for SPSU SG, SPS RF team and … LIU Session/Chamonix2011 10.11.2010

  2. SPS MDs in 2010 (related to the upgrade) • Nominal LHC beam • 25 ns, 50 ns, 75 ns, (150 ns) spacings • Ultimate LHC beam • 25 ns, 50 ns spacings • Single bunch with small and nominal transverse emittances • nominal intensity (stability in double RF system) • ultimate intensity (TMCI, long. instability) • very high intensities (up to 3.5 1011 injected) • Low γt optics • single bunch, high intensities, TMCI But… MDs still continue (50 ns LHC beam yesterday) Most of the data has not yet been analysed

  3. Some results for 2010 • Low beam losses (5%) for nominal LHC intensity (with low vertical chromaticity) • No TMCI at injection for ultimate bunches. Ultimate bunch accelerated to 450 GeV/c with low loss and low chromaticity. More problems/losses for small transverse emittances. Some transv. emittance blow-up. • Ultimate LHC beam – 25 ns: large losses, unstable beam on FT, large emittances • 50 ns: 10% losses, no transv. emittance blow-up • No limitation from ZS after change of settings by BT group and from MOPOS at the end of run MD limitations: MKE heating and outgassing (MD SC), transverse emittance measurements (no bunch-by-bunch), time allocation

  4. List of MD studies for SPS upgrade(MSWG 18/06/2010) • a-C coating: e-cloud suppression, ageing, outgassing: • nominal and higher intensity LHC beam, ions • limitations with “above nominal” intensity beams (beam losses, e-cloud scaling with intensity, beam quality,…) • multi-bunch: increase intensity in steps (more work in injectors, but…) • single bunch with highest possible intensity • TMCI threshold with nominal LHC emittances (FB specification): • single bunch of ultimate intensity • stability and emittance blow-up in double RF system • nominal and above nominal intensity LHC beam, single bunch • impedance identification and follow-up (reference measurements) • nominal and lower intensity LHC beam with 25 ns, 50 ns, 75 ns and 150 ns spacing • single bunch with constant longitudinal parameters and variable intensity

  5. Questions • source of limitations/bottlenecks → e-cloud (25 ns), beam loading, coupled bunch instabilities • possible cures and mitigation measures → e-cloud mitigation, RF system modification, impedance reduction • p/b and emittance as a function of the distance between bunches today and after upgrade • … • what should be done for delivering smaller transverse emittances at ultimate beam current? → beam from PS for studies, improvement of transverse emittance measurements, e-cloud mitigation (25 ns spacing), transverse impedance reduction, transverse damper/FB improvement

  6. Intensity limitations (LHC beam with 25 ns bunch spacing)

  7. SPS beams now and in future * single batch injection in PS

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