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RF measurements during long MD in Week 17 23 & 25 April 2012

RF measurements during long MD in Week 17 23 & 25 April 2012. Faraday Cage : T. Argyropoulos , T. Bohl , J . E. Muller, E. Shaposhnikova CCC : H. Bartosik , Y . Papaphilippou , G. Rumolo , B . Salvant , SPS OP + …. SPSU-BD 31/05/2012. MD aims.

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RF measurements during long MD in Week 17 23 & 25 April 2012

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  1. RF measurements during long MD in Week 17 23 & 25 April 2012 Faraday Cage: T. Argyropoulos, T. Bohl, J. E. Muller, E. Shaposhnikova CCC: H. Bartosik, Y. Papaphilippou, G. Rumolo, B. Salvant, SPS OP + … SPSU-BD 31/05/2012

  2. MD aims • Single bunch studies in nominal (Q26) and low γt (Q20) optics. • Intensity threshold comparison in single RF between the two • optics with and without phase loop. • scan of the relative phase between the two RF systems (φ800) • with and without phase loop in nominal intensities (~1x1011). • Few remarks: • Many problems (23rd - PS POPS, 25th - 2 RF TX were tripping)  • limited the number of data acquired. • MDs on different nights  not the same conditions for the comparison • (voltage programs, long. dampers etc.)

  3. Q20 – MD on 23/04 – single RF • injected bunch lengths (~3.95 ns) • V200 programmed for constant bucket area of 0.65 eVs (5.25 MV at flat bottom) • with injection at 3 MV and rise to 7 MV at flat top • no controlled emittance blow –up. • low longitudinal emittances (~ 0.33 eVs) at flat bottom • long. dampers ON • total losses ~ 5 % Bunch length evolution along the cycle Phase loop OFF • Intensity ~ 1.8x1011 • Instability starts at ~ 15.7 s • Intensity ~ 1.70x1011 • stable • jump in bunch lengths after 15 s • for some cases (and bunch peak) • threshold is higher than • 1.5x1011 p but not enough • measurements to define it • accurately • dipole oscillations (from bunch • profiles) don’t show much • Small improvement with • phase loop ON

  4. Q26 – MD on 25/04 – single RF Voltage program • injected bunch lengths (~3.7 ns) • no controlled emittance blow –up. • low longitudinal emittances (~ 0.32 eVs) at FB • long. dampers OFF • very few good measurements due to RF TX and • time limit (+ correction of chromaticity) Bunch length evolution along the cycle Phase loop OFF • more time is needed to damp the initial oscillations • threshold seem to be around 1.0x1011 p? • (mainly from visual observations) • similar with phase loop ON • Intensity ~ 0.75x1011 • stable along the ramp

  5. Summary plots (preliminary) Δτ : bunch length amplitude oscillations during the ramp better analysis of these files is needed due to scope saturation The horizontal line in the plots indicates the noise level

  6. Conclusions – future plans • Q20 : intensity threshold > 1.5x1011 • Q26 : intensity threshold ~ 1.0x1011(?) • analysis of the latest measurements (last week) showing lower threshold in • Q20 (1.0x1011)  compare the parameters between the MDs (V200, εL, τ …) • chromaticity control for highest intensities • define the energy threshold N ~ 1/E5/4 • more statistics is needed to define accurate the thresholds!

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