Commissioning and First Performance of the LHC Beam Instrumentation May 2 nd - 6 th 2010 Santa Fe, New Mexico, USA. Rhodri Jones (CERN Beam Instrumentation Group)

● 2008 ● Accelerator complete ● Ring cold and under vacuum ● September 10 th 2008 ● First beams around – made it to Google LHC Commissioning – 2008 Timeline 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

First Beams Circulate in the LHC 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

Beam Threading ● Threading the beam round the LHC ring ● One beam at a time, one hour per beam. ● Collimators were used to intercept the beam (1 bunch, 2×10 9 protons) ● Beam through 1 sector (1/8 ring) ● correct trajectory, open collimator and move on Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) Beam 2 threading BPM availability ~ 99% Courtesy of CMS Courtesy of ATLAS

The Wide Band Time Normaliser 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) A B 1.5ns B + 1.5ns A B Beam Splitter Delay lines Combiner Pick-up  t depends on position

● Orbit & BPM Stability ● Short term stability (15 minutes) better than 10  m ● Alternating high/low peaks follow the beta function indicating that: ● large fraction of this noise results from beam itself ● resolution & stability of BPM system orbit mode with single pilot bunch ~5  m ● BUT - surface electronics sensitive to temperature (~50  m per °C) ● Active rack temperature stabilisation being looked into LHC BPM System Performance 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

LHC Beam TV (BTV) System 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) ● Beam Profile Measurements in the LHC ● For injection, dump & matching ● 1mm Alumina (scintillator screen) ● 12  m Titanium Foil (OTR screen) Dump line BTV tanks awaiting final installation

LHC BTV System 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) ● All screens fully commissioned ● 18 BTV in the LHC transfer lines ● 13 BTV in the LHC ring ● 6 BTV in the LHC dump lines ● Both video link and digitised data acquired on first shot ● Still to do ● Gradual replacement of 13 LHC ring CCD cameras with radiation tolerant cameras ● Turn by turn acquisition for matching measurements using fast cameras First Beam in the LHC 8/8/2008 First full turn as seen by the BTV 10/9/2008 Uncaptured beam sweeps through he dump line

● 2008 ● Accelerator complete ● Ring cold and under vacuum ● September 10 th 2008 ● First beams around – made it to Google ● September 19 th 2008 ● The incident ● 2008 – 2009 ● 14 months of major repairs and consolidation ● New Quench Protection System for online monitoring and protection of all joints ● However… LHC Commissioning – 2008 Timeline 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

Magnet Interconnection 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) Dipole busbar Melted by arc

● During repair work in the damaged sector, inspection of the joints revealed systematic voids caused by the welding procedure ● Extensive simulations and measurements in the lab have shown that there is potential for thermal run away in case of a bus-bar quench Issues with Joint Quality 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) bus U-profile bus wedge SolderNo solder

● A complete splice consolidation campaign is required ● options under examination: To go to 7 TeV per Beam 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● Splice issues not yet fully resolved ● To be 100% sure that we can go safely to 7 TeV per beam ● eradication of joint issue required ● implies a complete warm-up and long shutdown (2012) ● The LHC is limited to 3.5 TeV per beam in 2010/2011 ● Will run continuously at this energy until end 2011 ● In the meantime ● New Quench Protection System fully deployed and tested ● Continuously measures splice resistance for all splices ● All magnet circuits qualified for 3.5 TeV ● Thermal runaway unlikely even in worst case scenarios ● Main bends and quads to 6000 A and looking good so far To Conclude on this Issue 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● November 20th 2009 ● First beams around again ● November 29th 2009 ● Both beams accelerated to 1.18 TeV simultaneously ● LHC officially the World’s Highest Energy Accelerator ● December 8th 2009 ● 2 x 2 accelerated to 1.18 TeV ● First collisions seen in ATLAS before beam lost! ● December 14th 2009 ● Stable 2 x 2 at 1.18 TeV ● Collisions in all four experiments LHC Commissioning – 2009 Timeline 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● DCCT Noise Performance: ● Actual performance : 7.6×10 8 charges rms (1.4µA for 1s integration time) ● Foreseen performance : resolution of 1µA with 1 s integration time ● Fast BCT Performance ● Noise at the 10 8 charge level for 20ms integration ● Has allowed lifetime measurements of hundreds of hours ● Agreement between DCCT and Fast BCT at the few % level ● Beam intensity still too low at the moment for a precise cross-calibration BCT Commissioning 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) ● Fast BCT sees first circulating beam & first captured beam ● DCCT at limit of sensitivity sees first circulating protons

Beam Loss Detectors 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) ● Design criteria: Signal speed and reliability ● Dynamic range (> 10 9 ) limited by leakage current through insulator ceramics (lower) and saturation due to space charge (upper) Secondary Emission Monitor SEM (~300): ● Length 10 cm ● P < 10-7 bar ● ~ times smaller gain Ionization chamber (~3500): ● N 2 gas filling at 100 mbar over-pressure ● Length 50 cm ● Sensitive volume 1.5 l ● Ion collection time 85  s Both monitors: ● Parallel electrodes (Al or Ti) separated by 0.5 cm ● Low pass filter at the HV input ● Voltage 1.5 kV

Installed BLM Monitors 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) 4000 BLMs installed throughout the LHC

● Losses integrated & compared to threshold table ● 12 time intervals and 32 energy ranges! BLM Acquisition Electronics 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) Implemented on BDI DAB64x

BLM Detection Range DIPAC09 - May 2009 LHC Beam Instrumentation ● Pilot bunch of 5×10 9 close to damage level at 7TeV ● Loss of of nominal beam can create a quench at 7TeV 1 pilot bunch Full LHC fill

● Are the thresholds safely above the noise levels? ● YES up to 5TeV ● Noise proportional to cable length ● May require RadHard ASIC CFC for full performance at 7TeV ● Would allow mounting front-end electronics near BLM Thresholds Compared to Noise Levels 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) (40 µs)

● Full collimation setup at injection in 2009 ● Beam cleaning efficiencies ≥ 99.98% ~ as designed BLMs & Collimation 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) Measurement noise Peak leakage to SC magnets Loss at primary collimator Collimation Momentum Cleaning Collimation Betatron Cleaning Beam Dump Protection

● 27 th February 2010 ● First injection ● 28 th Feb - 15 th March ● Both beams circulating ● Set-up at 450 GeV LHC Commissioning Timeline 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● Kickers in the ejection line sweep during 1 LHC turn to dilute the intensity on the dump Setting-up of the Beam Dump 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● One operational & one spare H & V wire-scanner per beam ● Design based on the second generation SPS linear wire-scanners ● Scan speed of 1m/s ● Detection using downstream photomultiplier ● Acquisition electronics ● Based on logarithmic amplifier averaging over many bunches ● Bunch by bunch system (still to be commissioned) ● Based on LHCb 40MHz integrator ASIC LHC Wire Scanner 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● Linearity ● Wire scanners beam centroid measured while applying closed orbit bumps ● Linearity better than 5% in all cases ● Linearity of BPMs and orbit correctors at the 1% level ● Resolution & Reproducibility ● Preliminary results indicate that this is better than 50  m for both LHC Wire Scanner - Performance 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● When does the wire break? ● Simulations corroborated by SPS measurements show that a 30  m carbon wire scanned at 1ms -1 will survive ( T < 4000K ) with: ● 25% of nominal LHC beam at injection energy (limitation at 450GeV) ● 7% of nominal LHC beam at top energy (a function of beam size not energy) ● When do we quench the downstream magnets? ● Simulations show that ● Limitation is first downstream quadrupole ● Wire scanner works to between 0.4% to 2% of nominal LHC beam at 7 TeV LHC Wire Scanner - Limitations 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● 27 th February 2010 ● First injection ● 28 th Feb - 15 th March ● Both beams circulating ● Set-up at 450 GeV ● 15 th – 18 th March ● Technical stop – main bends & quads good for 6 kA ● 19 th March – 29 th March ● Ramp to & set-up at 3.5 TeV LHC Commissioning Timeline 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

Controlling Tune & Chromaticity using the Base Band Q Measurement (BBQ) System 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) Direct Diode Detection (3D) Base band operation Excellent 24 bit audio ADCs available Signal conditioning / processing is easy

● The Hump ● Wandering perturbation in vertical plane of both beams ● Fast varying component makes it show up as wide frequency hump in spectra ● Slow component with ~7 minute period can move it across the tune ● Assuming single dipolar pertubation source the kick is less than 1 nRad ● Causes emittance blow-up, beam-loss & life-time reduction when it drifts onto tune ● Base Band Tune (BBQ) Measurement System ● Worked from the first injections ● Shows extremely high sensitivity with most measurements possible with residual beam oscillations ● Coherent micron level tune oscillations nearly always observed ● Typical tune measurement resolution in the range … LHC Tune System Commissioning 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) 40 nm The effect of the Hump on Lifetime as it crosses the Tune with a period of ~ 7 minutes The Hump

● Tune diagnostics throughout the ramp ● Early ramps had poor tune control ● Beam loss observed every time tune crossed resonance line LHC Ramp Commissioning 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● With full pre-cycling the fill-to-fill stability is now typically 2-3·10 -3 ● Variations frequently increase up to 0.02 ● Due to partial or different magnet pre-cycles after e.g. access or sector trips. ● Tune-FB routinely used for most ramps to compensate these effects ● Using peak fit on FFT with Hz Bandwidth (PLL still to be fully commissioned) Tune Feedback in the LHC 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) Hor. spectrum with Tune-FB OFFHor spectrum with Tune-FB ON The 'hump'

● Q'-Tracker demodulates sinusoidal frequency trims ● Increased original modulation of Δp/p from 10 Hz to 10 ● Mitigates tune stability effects at injection (ΔQres ~ 3-4·10 -4 ) ● Achieved nominal Q' resolutions → used as feed-forward for next ramp ● Feedback requires interplay between trims & QPS system to be resolved Chromaticity Measurement in the LHC 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) Q (dotted) and Q' (solid) during snap-back horizontal vertical

● Light Sources ● Below 1.2 TeV : 2 period, 5T SC undulator ● Above 1.2 TeV : Separation dipole ● Dipole edge radiation ( 1.2 to 3 TeV ) ● Central dipole radiation ( 3 to 7 TeV ) ● Spectrum and focus change during ramping ● Main components ● High reflectivity extraction mirror ● 4.8m optical table with heavy shielding ● Motorized delay line to change focus ● Horizontal Slits to select beam position Synchrotron Light in the LHC 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) Alignment and calibration 150-mm and 600-mm stages Focus trombone F1 Attenuator filter wheels Slit F2 PMT Fast Camera Slow Camera Extraction mirror (BSRTM) Mirror 1 Colour filter wheel Attenuator filter wheels Pulsed LED Laser-insertion mirror on 150-mm stage Beam 1 Beam 2

● Monitoring of the 3  s abort gap ● Every 100ms detect if gap population over 10% of quench level ● 10 5 protons in100ns at 7TeV but plenty of photons ● Most challenging at 1.2TeV with low light levels (5×10 7 prot / 100ns) ● Uses gated MCP / PMT ● Gated photomultiplier gets ~15% of collected light ● PMT gated off except during the 3  s abort gap ● Integration using LHCb integrator ASIC ● Gap observed in 30 bins with 100ns resolution ● Single pilot debunching when the RF is switched OFF The LHC Abort Gap Monitor 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● Used from very early stage to investigate emittance growth ● Blow-up from as yet unidentified source causes systematic blow- up of Beam 2 vertical plane The LHC Synchrotron Light Monitors 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)  h = 0.68mm  v = 0.56mm  h = 0.70mm  v = 1.05mm Beam 1Beam 2

● Effect of multiple light sources clearly visible during ramp ● Will be countered by slit selection of source ● Agreement between wirescanners (blue) and synchrotron light seen to diverge as beam size becomes smaller during acceleration ● Wavelength selection using Blue filter seen to improve the situation Beam Size Throughout the Ramp 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN) RAMP START Trombone focusing Blue Filter Beam Size Calculated Emittance

● 27 th February 2010 ● First injection ● 28 th Feb - 15 th March ● Both beams circulating ● Set-up at 450 GeV ● 15 th – 18 th March ● Technical stop – main bends & quads good for 6 kA ● 19 th March – 29 th March ● Ramp to & set-up at 3.5 TeV ● 30 th March ● 3.5 TeV collision under ‘stable’ beam conditions ● 25 th April ● Squeezed stable beams (  * = 2m) – 30 hour fill LHC Commissioning Timeline 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

First Collisions at 3.5TeV 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

First Collisions at 3.5TeV 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)

● Our “baby” (the LHC) has learnt to walk surprisingly quickly ● Routine ramps with 2×10 10 p to 3.5 TeV (just below the safe beam limit) ● Squeeze in all 4 IR’s to 2m  * starts to run smoothly ● Squeezed optics fully qualified for protection ● In parallel important progress towards higher intensities ● Stored nominal bunch intensity at 450GeV with excellent lifetimes ● Injected, accelerated & stored multiple bunches ● All of this made possible in a large part due to very good instrumentation ● Orbit system working reliably from day 1 ● BLM system protecting the machine & allowing accurate collimation set-up ● Tune & chromaticity systems with unprecedented resolution ● Feedback on tune quickly operational to allow fast ramp development ● BCTs providing machine protection flags & lifetime measurements for optimisation ● Emittance devices up & running to provide continuous & calibrated beam sizes ● Collision rate monitors ready to see first collisions ● US through LARP has had a big role to play in this success ● Years testing tune & chromaticity techniques in collaboration with RHIC & Tevatron ● Help with redesign & commissioning of the synchrotron light monitors ● Delivery & initial commissioning of US-LARP hardware systems ● Luminosity monitors based on fast ionisation chambers for the two high luminosity IRs ● Schottky systems - have seen coherent signals but still await first clear Schottky signals Conclusion 2010 Beam Instrumentation Workshop - Santa Fe, New Mexico, USA. Rhodri Jones (CERN)