LHC Emittance Measurement Preparation during LHC Commissioning LBOC Meeting February 17, 2015 Maria Kuhn – February 17, 2015

LHC Motivation Goal for LHC commissioning: operational emittance measurement tools at end of first two months with beam − Measure optics − Obtain optimum wire scanner working point − Operational BSRT − Quantify emittance growth through the LHC cycle Motivation: oStatus quo after LS1: − No fully trustable emittance measurements for LHC Run 1 oProblems: − Instruments could not be fully commissioned at the start of Run 1 Parasitic commissioning not possible, MDs not sufficient − Instruments partially not working 2 M. Kuhn - 17/02/2015

LHC First 2 Months of LHC Commissioning M. Kuhn - 17/02/2015 InstrumentTask Injection energy Flattop energy Squeezed optics Wire scanner Confirm BLM thresholds:  find wire scan limits ~ 30 min Orbit bump calibration:  validate calibration of all eight wire scanners ~ 80 min Qualify photo-multiplier saturation:  find optimum wire scanner working points ~ 180 min Optics measure- ments K-modulation in IR4:  measure  in the vicinity of the transverse profile monitors ~ 60 min K-modulation in the IPs:  measure  * ~ 240 min 3  Need low intensity beams – very few bunches  Extra time needed to set up beams and the machine

LHC Wire Scanners oOrbit bump calibration oPhotomultiplier saturation measurements 4 M. Kuhn - 17/02/2015

LHC oOrbit bumps at injection and flattop energy − For all 8 wire scanners Operational and spare LHC wire scanners oGoing from +3 mm to -3 mm in 1 mm steps − Usually takes ~ 10 min per wire scanner and energy  ~ 80 min in total per energy plateau Wire Scanner Orbit Bump Calibration M. Kuhn - 17/02/ Single bunches ~ bunches Low bunch intensity Before: upper wire scanner intensity limit to be checked BSRT in parallel if possible

LHC Wire Scanner Photomultiplier Saturation oFind optimum wire scanner working point! oChange filter and voltage of wire scanner photomultipliers − All 8 wire scanners in parallel − ~ 3 hour in total per energy plateau M. Kuhn - 17/02/ Single bunches ~ bunches Low bunch intensity Example photomultiplier saturation curve of a wire scanner in the Booster. Courtesy G. Sterbini

LHC New LHC Wire Scanner Application Layout of the new operational wire scanner application for the LHC: 7 M. Kuhn - 16/02/2015 Wire scan limits with sublimation limits and BLM thresholds will be implemented in front end (like in 2012). New photomultipliers installed!

LHC K-Modulation oBeta function measurements in IR4 − Turn-by-turn phase advance measurents absolutely necessary including optics measurements through the ramp (not possible with k- modulation)  * measurements! 8 M. Kuhn - 17/02/2015

LHC IP4 oMeasure  at quadrupoles in IR4 at injection, flattop and with squeezed optics oOne quadrupole at a time (~ 5 – 10 min per quadrupole) − Step or sine modulation possible − ~ 1 hour required per beam mode oRequired beam conditions: − Transverse damper off − Injection tunes (less coupling) − Only one nominal bunch or pilot beam K-Modulation in IR4 Beam 1MQY.5L4.B1MQY.5R4.B1MQY.6R4.B1MQM.7R4.B1 Beam 2MQY.5L4.B2MQY.5R4.B2MQY.6L4.B2 M. Kuhn - 17/02/2015 9

LHC K-Modulation in the IPs LeftMQXA1.L1MQXA1.L2MQXA1.L5MQXA1.L8 RightMQXA1.R1MQXA1.R2MQXA1.R5MQXA1.R8 M. Kuhn - 17/02/

LHC New K-Modulation Tool for the CCC 11 M. Kuhn - 17/02/2015

LHC SPS K-Modulation 12.November 2014 Screenshot of the application: − Note: very good tune signal and response in the vertical plane! 12 M. Kuhn - 03/12/2014

LHC Planning oWire scanner calibration and k-modulation into LHC commissioning plan oLHC commissioning planning: slides from Jorg‘s LMC talk (December 10, 2014) 13 M. Kuhn - 17/02/2015

LHC LHC Commissioning - Requests 1.Injection – probe bunch − 60 min dedicated k-modulation in IR4 at 450 GeV − Optional: 30 min parasitic wire scans to confirm BLM thresholds 2.Ramp – probe bunch − 60 min dedicated k-modulation in IR4 at 6.5 TeV − Optional: 30 min parasitic wire scans to confirm BLM thresholds 3.Squeeze - probe bunch − 60 min dedicated k-modulation in IR4 with squeezed optics − 240 min dedicated k-modulation to measure  * 4.Injection – nominal bunch − 80 min dedicated wire scanner orbit bump calibration − 180 min (parasitic) wire scanner photomultiplier saturation studies 5.Ramp, squeeze, collide – nominal bunch − 80 min dedicated wire scanner orbit bump calibration − 180 min (parasitic) wire scanner photomultiplier saturation studies 14 M. Kuhn - 17/02/2015

LHC Injection – probe bunch Injection Squeeze Ramp Collide  First turn.  Capture and closed orbit. o No bumps (Xing & separation) at this stage.  Tune, chromaticity & optics - measure & correct.  RF loops, correct buckets.  Basic instrumentation checks (calibrations, signal swaps,…).  Settings up of orbit and tune feedbacks. o Systematic check of tune, chromaticity and orbit corrector circuit polarities. flat probe 1 hour dedicated k- modulation in IR4 needed 0.5 hours parasitic wire scans needed to confirm BLM thresholds M. Kuhn - 17/02/

LHC Ramp – probe bunch Injection Squeeze Ramp Collide  First ramps with probe bunches, orbit and tune feedbacks ON. o Flat orbit, coarse collimators (TCP, TCDQ).  Optics measurement and correction on flat top. o On the fly optics measurements in the ramp.  Coarse collimator setup / check on flat top. o Preparation for squeeze – TCP and TCDQ.  Dump checks at different energies along ramp. flat probe coarse 1 hour dedicated k- modulation in IR4 at flattop energy needed M. Kuhn - 17/02/ hours parasitic wire scans needed to confirm BLM thresholds at flattop energy

LHC Squeeze – probe bunch Injection Squeeze Ramp Collide  Squeeze in steps to 40 cm, optics measurements, orbit & tune & Q’ corrections. o Flat orbit, coarse collimators (TCP, TCDQ).  Repeat with optics corrections in place, measure corrected optics. o Iterate corrections (or cycles) if required.  Local triplet apertures to asses  * reach. o Confirm measurements at injection. o At  * of 40 or 80 cm – tbd. 40 cm flat probe coarse 1 hour dedicated k- modulation in IR4 with squeezed optics needed M. Kuhn - 17/02/ hours k-modulation to measure  *

LHC Injection – nominal bunch M. Kuhn - 17/02/2015 Injection Squeeze Ramp Collide  Establish flat reference orbit for cycle.  Switch on bumps (Xing and separation) and experiments magnets.  Injection and transfer line fine setup.  Alignment of collimators and protection devices (dump, injection).  Aperture measurements (global, local: triplets, injection, dump).  Beam instrumentation checkout.  RF and ADT set up.  FIDEL measurements and corrections.  And much more. bumps nominal tight 80 min dedicated wire scanner orbit bump calibration + 3 hours (parasitic) wire scanner photomultiplier saturation studies 18

LHC RSC – nominal bunch Injection Squeeze Ramp Collide  Ramp nominal bunch with longitudinal blowup.  Collimator setup (IR7+3) on flat top.  Ramp and squeeze to 80 cm with bumps (Xing & separation). o Align TCTs: FT, end of squeeze.  Collide - find collisions (if not already done). o Align TCTs and TCLs, possibly also roman pots. 80 cm bumps nominal tight M. Kuhn - 17/02/ min dedicated wire scanner orbit bump calibration + 3 hours (parasitic) wire scanner photomultiplier saturation studies at flattop energy Measure cycles with wire scanner and BSRT (parasitic)

LHC Emittance Measurements oInjection oRamp oFlattop oSqueeze oCollisions 20 M. Kuhn - 17/02/2015

LHC After LHC Cycle Setup oRequirement: BSRT has to be commissioned early on as well! oMeasurements with few bunches during many ramps − Mainly with wire scanners and BSRT oMeasurements with few bunches during the entire cycle including collisions − Mainly with wire scanners and BSRT − (BGI not possible for protons, BGV only later in 2015) − Comparison with emittance from luminosity if applicable oComparison of transverse profile measurements during Van der Meer scans at the end of LHC commissioning phase − With wire scanners, BRST and LHCb SMOG − Comparison with emittance from luminosity M. Kuhn - 17/02/ Not possible! Beam intensity too high.

LHC 2015 Q2 oFrom Mike‘s LMC talk (Jan 28, 215) M. Kuhn - 17/02/ Use the first week of collisions to compare emittances from wire scans and BSRT to emittances from luminosity and LHCb SMOG data during stable beams!

LHC Stable beams M. Kuhn - 17/02/2015 Injection Squeeze Ramp Collide  First stable beams with few bunches. 80 cm bumps STABLE BEAMS nominal tight  Squeeze + collide part to be repeated for medium  * (20-40 m). Measure parasitically with wire scanners and BSRT. Close LHCb Velo and measure with SMOG in parallel! 23

LHC Planning First Week of Collisions oTentative dates: week 21 (May 18 – 22, 2015) oWire scan limit at 6.5 TeV: ~ 10 bunches per beam! oATLAS/CMS luminosity not calibrated before Van der Meer scans, but could be analysed later − Need colliding bunches oFor LHCb SMOG the Velo needs to be closed − Need stable beams declared − Minimum 1 colliding bunch per beam − At least 6 non colliding bunches for meaningful measurement Could collide in ATLAS/CMS to obtain emittance from lumi in parallel − Minimum stable beams time ~ 1 hour M. Kuhn - 17/02/

LHC Emittance Measurements Run 2 oDuring LHC Run 1 it was possible to measure bunch-by-bunch emittances of the first 144 bunch batch at injection of physics fills − Can be compared to emittanc from peak luminosity − Important for evolution of growth through the year oConsiderations for emittance measurements during LHC Run 2 − Injection scans Problem: wire scans not possible with 288 bunches! − Question: start of filling scheme with 144 bunches possible? To be able to measure emittances at injection of physics fills 25 M. Kuhn - 17/02/2015

LHC Summary During LHC commissioning we want to: 1.Measure beta functions 2.Fully calibrate wire scanners and BSRTs 3.Quantify transverse emittance growth during the LHC cycle − Including injection, ramp, squeeze, and collisions Due to time constraints and high beam current we will not have the possibility to complete these measurements during the run! 26 M. Kuhn - 17/02/2015

LHC Thanks for your attention! Questions? Comments? M. Kuhn - 17/02/

LHC Spare Slides 28 M. Kuhn - 17/02/2015

LHC K-Modulation Overview M. Kuhn - 17/02/2015 Set Up 60 min Inject ion 10 min K-mod IR4 60 min Prepare + ramp 30 min K-mod IR4 60 min Squeeze 30 min K-mod IR4 + IPs 300 min 450 GeV injection energy 6.5 TeV collision energy Single bunches One or two nominal bunches Transverse damper off Injection tunes In total ~ 10 hours measurememt time Optional dump + re-inject 29

LHC Wire Scanner Calibration Overview M. Kuhn - 17/02/2015 Set Up 30 min Injec tion 10 min Orbit bumps 80 min PM satura tion 60 min Prepare + ramp 30 min Orbit bumps 80 min PM satura tion 60 min Squeeze + collide 60 min 450 GeV injection energy 6.5 TeV collision energy optional Single bunches ~ bunches Low bunch intensity Upper wire scanner intensity limit to be checked In total ~ 6 – 8 hours measurememt time Optional dump + re-inject 30

LHC First Measurements in the SPS oRequirements − Relatively long magnetic plateau (10 s or more) − Low energy (26 GeV) − Good tune signal (turn on chirp) oNote: SPS magnets are conventional (room-temperature) electromagnets 31 M. Kuhn - 03/12/2014 oTesting sinusoidal k-modulation: − Modulation to quadrupole directly at power converter − Power converter parameters: number of periods, amplitude, frequency

LHC SPS Tune Signal oEasily detectable tune peak in the vertical plane 32 M. Kuhn - 03/12/2014

LHC K-Modulation Analysis (1) oUnfortunately power converter data was not saved correctly oRepeated measurement on 13 November 2014 − Caveat: tune acquisition not during entire cycle oReminder: 33 M. Kuhn - 03/12/2014 Example:

LHC K-Modulation Analysis (2) 34 M. Kuhn - 03/12/2014 First tests of sinusoidal k-modulation were successful - proof of principle. To do: implement analysis in the application! Work in progress: further tests in the SPS and the LHC will follow.

LHC Measurement Precision Comparison oComparison of  function measurement accuracy: 35 M. Kuhn - 03/12/2014 Accelerator  uncertainty MethodYear TevatronBPM phase advance 1995 LEP~ 1%K-modulation2001 SPS~ %BPM phase advance 2012 LHC IP1/53 – 5 %K-modulation2011 LHC wire scanner 1.3 – 10.9 %K-modulation2012 LHC wire scanner 0.7 – 9.4 %BPM phase advance 2012

LHC LHC Inner Triplet –  * Measurement MQXA3MQXB2 MQXA1 36 M. Kuhn - 03/12/2014 IP1/5 Q3Q1 Q2 Modulation of quadrupole Q1 with power converter RTQX1 Nested circuits!

LHC First Step Modulation in the LHC oPower converter in simulation, no beam 37 M. Kuhn - 03/12/2014

LHC First Sinusoidal Modulation in the LHC oPower converter in simulation, no beam 38 M. Kuhn - 03/12/2014

LHC First Sinusoidal Modulation of the LHC Triplets oPower converter in simulation, no beam 39 M. Kuhn - 03/12/2014

LHC Quench Protection System (QPS) oQuench detector output while the power converter of the corresponding circuit performs a sinusoidal current modulation: − sinusoidal current of 15 A amplitude and a frequency of 0.25 Hz resulting in a maximum dI/dt of about 24 A/s − maximum inductance of 21 mH per coil  250 mV sinusoidal voltage oThe common mode caused by sinusoidal excitation is well suppressed: For QPS the sinusoidal excitation will be transparent! 40 M. Kuhn - 03/12/2014 J. Steckert The green line is the voltage difference between the compared coils in the magnet which are used to detect a quench.