Wire, flat beams and beam-beam MDs in 2017 LHC MD day 2017, March 31st, 2017 Wire, flat beams and beam-beam MDs in 2017 Y.Papaphilippou Thanks to the Beam-beam and luminosity working group and in particular F.Antoniou,  R.Alemany Fernandez, G.Arduini, R.Bruce, X.Buffat, S.Fartoukh, K.Fuchsberger, M.Hostettler, R.Jones, G.Iadarola, N.Karastathis, E.Metral, D.Pellegrini, S.Papadopoulou, T.Pieloni, M.Pojer, S.Redaelli, A.Rossi, B.Salvachua, H.Schmickler, G.Sterbini, G.Trad, R.Tomas, J.Wenninger (CERN), M.Fitterer, A.Patapenka, A.Valishev (FNAL)

Outline Long-range beam-beam effects and wire compensation Other long-range MDs Levelling, Head-on beam-beam and noise Beam-beam and optics Emittance evolution

Long-range Wire Compensation MDs Four DC wires embedded in collimators (TCTs) Two per IP compensating only beam 2 Installed in IP5 (2017) and in IP1 (2018) Prove compensation of long range effect Various observables Lifetime, halo (special diagnostics), tune-spread Tests with wires first in IP5 (2017) and then IP1 (2018) S.Valishev, et al.

Wire impact on single beam Goal: Test and calibrate the effect of the wires in a single beam (first at injection, then at flat top) Align wires with respect to the beam by measuring vertical orbit (or coupling) Measure impact of wires on beam orbit and tune and calibrate theoretical feed-forward functions Other optics measurements (linear and non-linear chromaticity, beta-beating, tune-spread, RDTs ) Similar measurements for the external wires and with a non-zero vertical position Estimate impact in lifetime and emittance (tails, halo?) and compensate with other wire (lower priority) G.Sterbini, A.Rossi, et al. Commissioning 2X8h already scheduled If time permits

Wire impact on single beam Goal: Test and calibrate the effect of the wires in a single beam (first at injection, then at flat top) Align wires with respect to the beam by measuring vertical orbit (or coupling) Measure impact of wires on beam orbit and tune and calibrate theoretical feed-forward functions Other optics measurements (linear and non-linear chromaticity, beta-beating, tune-spread, RDTs ) Similar measurements for the external wires and with a non-zero vertical position Estimate impact in lifetime and emittance (tails, halo?) and compensate with other wire (lower priority) G.Sterbini, A.Rossi, et al. Commissioning 2X8h already scheduled If time permits Energy: All can be done at 450 GeV. Qualification of tune and orbit feed-forward at 6.5 TeV Beams required: Only beam 2. Compatible with parallel studies using beam 1 Beam composition and intensity: Single nominal bunches of 1.3 x 1011 ppb Some tests can function already with probe Emittances: Nominal BCMS, i.e. ~1.5-2.0 μm.rad Optics: Nominal @ injection with nominal injection tunes, octupoles and chromaticity settings More exotic options if testing compensation or lifetime impact can be foreseen

BBLR Compensation preparation Goal: Measure the crossing angle reduction impact on lifetime Ideally, part of the intensity ramp-up Synergy with crossing angle levelling setting-up J.Wenninger et al.

BBLR Compensation preparation Goal: Measure the crossing angle reduction impact on lifetime Ideally, part of the intensity ramp-up Synergy with crossing angle levelling setting-up Energy: 6.5 TeV Beam composition: 2-3 colliding trains in beam1 and 2 (without/with IR8), a few single bunches in beam 2 With full long-range, PACMAN-L/R, non-colliding Intensity: Nominal @ 1.25 x 1011 ppb Emittances: Nominal for trains i.e. 2.5 μm.rad for BCMS, some nominal single bunches and some blown up by ADT to 4-5μm Optics measurements can be done with pilot Optics: Nominal @ collision with nominal tunes, octupoles and chromaticity settings β* of 40 cm, but probably 33 cm when commissioned J.Wenninger et al.

BBLR Compensation preparation Goal: Measure the crossing angle reduction impact on lifetime Ideally, part of the intensity ramp-up Synergy with crossing angle levelling setting-up Energy: 6.5 TeV Beam composition: 2-3 colliding trains in beam1 and 2 (without/with IR8), a few single bunches in beam 2 With full long-range, PACMAN-L/R, non-colliding Intensity: Nominal @ 1.25 x 1011 ppb Emittances: Nominal for trains i.e. 2.5 μm.rad for BCMS, some nominal single bunches and some blown up by ADT to 4-5μm Optics measurements can be done with pilot Optics: Nominal @ collision with nominal tunes, octupoles and chromaticity settings β* of 40 cm, but probably 33 cm when commissioned Procedure: Reduce crossing angle in steps Measure impact on lifetime of different bunches, while keeping constant orbit and tune Monitor impact in emittances, luminosity, halo, losses Measure optics if time permits J.Wenninger et al.

BBLR Wire Compensation Goal: Prove BBLR compensation with powering wire when crossing angle reduction impacts beam lifetime Leading order octupole effect compensation possible with present hardware

BBLR Wire Compensation Goal: Prove BBLR compensation with powering wire when crossing angle reduction impacts beam lifetime Leading order octupole effect compensation possible with present hardware Energy: 6.5 TeV Partially squeezed optics @ injection could be envisaged (simulation work to be done and optics commissioning overhead) Beam composition A few single bunches (around 3-4) in beam 2 (weak beam) spaced far enough for machine protection (abort gap kicker rise time) With full long-range, 1 non-colliding As many trains in beam 1 Intensity: Nominal of 1.25 x 1011 ppb for beam 1 (or highest possible from SPS) Emittances: Nominal for trains i.e. 2.5 μm.rad for BCMS, some nominal single bunches and some blown up by ADT to 4-5μm

BBLR Wire Compensation Goal: Prove BBLR compensation with powering wire when crossing angle reduction impacts beam lifetime Leading order octupole effect compensation possible with present hardware Energy: 6.5 TeV Partially squeezed optics @ injection could be envisaged (simulation work to be done and optics commissioning overhead) Beam composition A few single bunches (around 3-4) in beam 2 (weak beam) spaced far enough for machine protection (abort gap kicker rise time) With full long-range, 1 non-colliding As many trains in beam 1 Intensity: Nominal of 1.25 x 1011 ppb for beam 1 (or highest possible from SPS) Emittances: Nominal for trains i.e. 2.5 μm.rad for BCMS, some nominal single bunches and some blown up by ADT to 4-5μm Optics: Nominal @ collision with nominal tunes, octupoles and chromaticity settings β* of 40 cm, but probably 33 cm if commissioned Un-squeezed optics in IR1 (only if commissioned for IR compensation MD) Crossing angle: Start with nominal in both IR1 and 5, no collisions in IR2 and 8 Moving only one IR crossing angle could be envisaged

BBLR Compensation procedure Inject and ramp up a few bunches in beam 2 to commission orbit and tune feed-forward with wire (ideally during commissioning phase) and blow-up effect of ADT Compatible with parallel tests in beam 1 Inject, ramp-up and collide strong (beam 1) and weak beam (beam 2) Set internal TCT/L jaw at 5-6σcol (including other collimation adjustments enabling this) Reduce crossing angle in steps, while keeping orbit and tune constant Observe lifetime reduction and ramp-up the current of each wire in steps, observing lifetime recovery in colliding weak beam Monitor emittance, luminosity, halo, losses Repeat the test with different weak beam flavours (Pacman-L, Pacman-R, without HO and non-colliding)

BBLR Compensation procedure Inject and ramp up a few bunches in beam 2 to commission orbit and tune feed-forward with wire (ideally during commissioning phase) and blow-up effect of ADT Compatible with parallel tests in beam 1 Inject, ramp-up and collide strong (beam 1) and weak beam (beam 2) Set internal TCT/L jaw at 5-6σcol (including other collimation adjustments enabling this) Reduce crossing angle in steps, while keeping orbit and tune constant Observe lifetime reduction and ramp-up the current of each wire in steps, observing lifetime recovery in colliding weak beam Monitor emittance, luminosity, halo, losses Repeat the test with different weak beam flavours (Pacman-L, Pacman-R, without HO and non-colliding) Measure optics, e.g. beta-beating, coupling, chromaticity, tune spread, RDTs, with wire compensation Repeat the test with IR1 crossing angle fixed and/or separated in IR1 Repeat the test using the wires in external jaw If time permits

Other Long-range B-B MDs Round optics (operational but also pushed β*) LR limits (crossing angle vs. lifetime and losses) Different chromaticity, octupole and triplet corrector settings IP1/5 phase advance scan Higher intensity/brightness tests (ultimate 25ns, BCMS, 50ns) Tune-scan (during physics fills) Flat optics Passive compensation of tune during leveling ATS telescopic optics Octupole compensation D.Pellegrini, G.Iadarola, et al. S.Fartoukh et al.

Head-on B-B and noise Effect of low frequency noise Leveling by separation (and β*) In parallel plane (HV in IR1/5), or crossing plane (VH in IR1/5), or skew plane (45deg/135 deg) End (or beginning) of fill MD with trains or during intensity ramp up Head-on beam-beam limit and high frequency noise on colliding beams Emittance growth for “single” colliding bunches with different brightness against noise levels and damper gain Effect of low frequency noise Mimicking triplet eigen-frequencies with ADT Effect 50Hz noise (PC filters) Short test at injection and/or in conjunction with other MDs J.Wenninger, et al. X.Buffat, T.Pieloni, et al. M.Fitterer, et al.

Beam-Beam and optics Beta-beating driven by beam-beam T.Pieloni, R.Tomas, et al. Beta-beating driven by beam-beam Pilot vs High-brightness bunch Beta-beating measurement and correction Injection and then flat top Chromaticity variation due to LRs Measure chromaticity of pilot vs train Vary crossing angle Can be combined with tune-spread measurements @ collision

Emittance evolution Evolution of the beam distribution through the LHC cycle Single bunches with different brightness and profile measurements Can be parasitic (transverse and longitudinal profile logging) Observation of single beam parameter evolution at flat top Non-colliding bunches emittance evolution (parasitic MDs) Stability (different chromaticity and octupoles) Dependence on number of LRs “OP scans” for determining emittance through luminosity Parasitic MDs Beam stability for scans at IP1 Perform scans at both IPs simultaneously Impact of longitudinal profiles S.Papadopoulou et al. M.Hostettler et al.

Summary Theme LHC HL-LHC FCC Shifts Priority Wire impact on single beam x 2 (COM) 1 LR compensation preparation (X-angle scan) 2 (IR) LR wire compensation 3 LR Limits ATS/flat/low β* optics 2-3 1-2 LR limits tune-scan (BoF) Leveling by separation and β* 2 (IR, P) HO B-B limit and High/Low frequency noise Beam-beam and optics 2 Evolution of beam distributions Evolution of single beam parameters in flat top (P) OP scans COM: Commissioning, IR: Intensity Ramp-up, BoF: Beginning of Fill, P: Physics

Summary Theme LHC HL-LHC FCC Shifts Priority Wire impact on single beam x 2 (COM) 1 LR compensation preparation (X-angle scan) 2 (IR) LR wire compensation 3 LR Limits ATS/flat/low β* optics 2-3 1-2 LR limits tune-scan (BoF) Leveling by separation and β* 2 (IR, P) HO B-B limit and High/Low frequency noise Beam-beam and optics 2 Evolution of beam distributions Evolution of single beam parameters in flat top (P) OP scans Total of 11 (+5) MD shifts COM: Commissioning, IR: Intensity Ramp-up, BoF: Beginning of Fill, P: Physics