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Review MDs Transverse Damper from Run1 to Run2. r eported by W. Hofle for ADT & friends. A. Butterworth G. Kotzian T. Levens D. Valuch. LHC MSWG Special Meeting 02.09.2014. Overview. Run 1: Three types of “Sessions”: Commissioning Operational Developments Machine Developments
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W. Hofle @ LHC Studies WG Day 2.09.2014 Review MDs Transverse Damper from Run1 to Run2 reported by W. Hofle for ADT & friends A. Butterworth G. Kotzian T. Levens D. Valuch LHC MSWG Special Meeting 02.09.2014
W. Hofle @ LHC Studies WG Day 2.09.2014 Overview • Run 1: Three types of “Sessions”: • Commissioning • Operational Developments • Machine Developments • Future ADT contributions to MDs dealt also elsewhere in today’s review: • Halo Cleaning (s. Redaelli) • Abort gap cleaning (AGC) and injection slot cleaning (J. Uythoven) • Quench Limits (B. Auchmann) • Instabilities (T. Pieloni) • Goals for ADT Team for 2015: • Re-commission features developed in Run 1 with new hardware and software following the upgrade of ADT electronics • Contribute to diagnostics for instability observation • Develop new modes of operation and complete pending developments • Investigate noise properties of ADT
W. Hofle @ LHC Studies WG Day 2.09.2014 LHC Transverse Feedback - Post LS1 Plan Major upgrade in LS1 (2013-2014) • doubling # of pick-ups • complete re-cabling of PUs • new digital hardware • multiple ADCs and DACs • reduction of noise • flexibility for gain control • instability diagnostics (trigger !) • tune diagnostics (GPU) Pickup Q8 Pickup Q10 Production run of new digital board ready for SPS Re-commissioning SPS now testbed D. Valuchet al. Evian 2014: https://indico.cern.ch/event/310353/session/4/contribution/14/material/paper/2.pdf
W. Hofle @ LHC Studies WG Day 2.09.2014 Past and Future MD Subjects / operational development • Run 1: • Abort Gap and Injection Gap Cleaning • Transverse blow-up with noise • Modulation of Gain for Tune Loop compatibility • Tune measurement from ADT with active excitation • Tune measurement from ADT with passive excitation • Variation of gain in ramp • Damper noise and emittance blow-up with colliding beams • Run 2: Subjects not completed and to be continued: • Improvements to Abort Gap Cleaning (bipolar pulse) • Tune Measurement • Tuning of 25 ns operation • Noise studies • Run 2: New subjects: • Halo Cleaning with coherent excitation Stefano • Improvements to Loss Maps (loss maps with full beam & energy) Stefano • New modes of operation (digital filters) to be tested on upgraded SPS damper first
W. Hofle @ LHC Studies WG Day 2.09.2014 Abort Gap Cleaning (Abort Gap Monitor (Synchrotron Light) 2009 3 ms Time (turns) Time (within turn) • Abort Gap Cleaning by ADT (DDS) in V-plane stepping through a range of frequencies • Injection Gap Cleaning by ADT in H-plane • New ADT development: bi-polar envelope for start-up • New BSRT development: automatic switch on in coast M. Meddahi et al. IPAC’10 B. Goddard et al. IPAC’11 E. Gianfelice-Wendt et al. IPAC’12
W. Hofle @ LHC Studies WG Day 2.09.2014 Selective Transverse Blow-up gate, 11 ms (example) • “White noise” i.e. pseudo-random numbers generated on FPGA • clocked at 40 MS/s • aperture measurements by blow-up • loss maps for collimation set-up • dynamic aperture • collimation quench tests (500+ kW) • knock out of bunches • any kind of excitation can be gated • (also DDS produced narrow band) Wire scanner measurements (normalized transverse emittance) 2 mm 18 mm IPAC’12 MOPWO050 stops at 18 mm aperture aperture measurement using blow-up with transverse damper
W. Hofle @ LHC Studies WG Day 2.09.2014 Comparison loss maps 3rd order resonance damper loss map New development plan for 2015: making loss maps with gated excitation at end of fill with full beam intensity at top energy and in ramp Loss Maps: V. J. Moens, S. Redaelliet al. IPAC’13 MOPWO050
W. Hofle @ LHC Studies WG Day 2.09.2014 Impact on Tune Measurement System (LHC) feedback gain with damper, max gain used • less broadening with lower gain • reduction of tune peak, i.e. • increase residual oscillations by more than 20 dB R. Steinhagen PAC’11, N.Y. • solution deployed in 2012: ADT gain modulation within turn and gated BBQ • 6 bunches are used for the Tune Measurement, these have low ADT gain
W. Hofle @ LHC Studies WG Day 2.09.2014 ADT through the cycle - gain LSA:0.25 LSA:0.02 D. Valuch @ Evian 2011
W. Hofle @ LHC Studies WG Day 2.09.2014 Fast Losses with ADT Simulating “UFO” Type Losses for Quench Test evolution of beam oscillation amplitude Fast losses (BLM signal) 1 ms Transverse Feedback was used as exciter in three quench tests carried out in February 2013 IPAC’13 M. Sapinski et al. WEPME044 and THEA045 (Fast Losses and Quench Tests)
W. Hofle @ LHC Studies WG Day 2.09.2014 Shaping Time Domain Response Condition for h(nTb) = 0 symmetry of roll off • Motivated by appearance of single bunch instabilities • Used operationally for squeeze • and 25 ns spacing tests • Causes additional blow-up • follow-up W. Hofle et al., IPAC’13 WEPME043
W. Hofle @ LHC Studies WG Day 2.09.2014 Performance with Bunch Trains in LHC 2012 50 ns bunch spacing standard + hold 144 bunches (4x36) 25 ns bunch spacing enhanced bandwidth 144 bunches (2x72) Injection oscillation damping IPAC’13 W. Hofle et al., WEPME43
W. Hofle @ LHC Studies WG Day 2.09.2014 Bunch-by-Bunch cont’d – 25 ns sensitivity to internal bunch motion even for 2015 odd shortest MD: two shots August 26, 2011 [in midst of 25 ns setting-up] G. Kotzian, ABP-HSC meeting 22.01.2014 D. Valuch et al., Evian 2014
W. Hofle @ LHC Studies WG Day 2.09.2014 Tune Measurement from ADT data - active ADT excitation • 2730 turns resolution too limited to clearly resolve peaks • (20 Hz apart) • Repeat in 2015 • lower gain on leading 6 (12 bunches) • Longer acquisition buffers F. Dubouchet et al. IBIC’13, TUPF29
W. Hofle @ LHC Studies WG Day 2.09.2014 Tune Measurement from ADT data- passive observation cleaning (injection) time high gain (@450 GeV) (trench @tune) lower gain (average over 6 bunches) parasitic lines ! (ramp) tune change at start of squeeze (0.280.31) (4 TeV) tune (H) F. Dubouchet et al. IBIC’13 TUPF29 Based on recording of 6 bunches (horizontal plane) (also considering and tested excitation by short burst gated on 6 bunches)
W. Hofle @ LHC Studies WG Day 2.09.2014 Proposal from 2012: ADT MD with noise and gain variation for LHC MD block 2 / 2012 Motivation: Probe interplay of damper gain and noise for minimization of emittance blow-up • two ramps with • 8 bunches per beam at 1.5x1011 • filling pattern with at least one bunch with • no collisions • collisions in IP1 and IP5 • collisions in IP1, IP5 and IP8 • collisions in IP8 only • With colliding beams at 4 TeV in adjust: • 1st fill: different levels of noise with ADT at constant ADT gain • measure blow-up and bunch-by-bunch lumi • 2nd fill: based on results of previous fill inject a fixed level of noise with ADT and • observe the effect of a change of gain on the lumi and the emittance • 2012: Joint MD with BB team: not sufficient time to complete the program above 2015 V. Lebedev et al. IPAC’11, MOPO013
W. Hofle @ LHC Studies WG Day 2.09.2014 Summary Incoming Operational Development 2015 • Exploration of injection oscillation and instability diagnostics via Observation Box • Abort Gap Cleaning improvements (as needed) • Damping of Scrubbing Beam, optimization of 25 ns running (when scheduled) • Tune Measurement with ADT: active excitation of leading bunch train 1st priority • When stable ADT tune measurement tune loop using ADT can be envisaged • Tune measurement with observation box w/o excitation when operational • Efficient loss maps with full beam / during ramp and end of fill Proposed (real) MDs for 2015 • Halo Cleaning using Transverse Damper (S.R.) • Bench mark of blow-up equation with injected noise (W.H.)