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LHC Instrumentation Status and Challenges

LHC Instrumentation Status and Challenges. 12 th Beam Instrumentation Workshop Fermilab 1 st - 4 th May 2006 Rhodri Jones (CERN Beam Instrumentation Group). Overview. General LHC construction status Instrumentation What’s required & when Status of Distributed Systems

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LHC Instrumentation Status and Challenges

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  1. LHC InstrumentationStatus and Challenges 12th Beam Instrumentation Workshop Fermilab 1st - 4th May 2006 Rhodri Jones (CERN Beam Instrumentation Group)

  2. Overview • General LHC construction status Instrumentation • What’s required & when • Status of Distributed Systems • Beam position measurement • Beam loss measurement • Status of Systems with US-LARP involvement • Tune, chromaticity & coupling measurement • Luminosity Monitors • Schottky Monitors 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  3. TI8 successfully commissioned in 2004 LHC Construction Status Nearly 3/8ths of the LHC Installed with over 500 cryomagnets in place 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  4. LHC Construction Status Final Magnet Preparation 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  5. LHC Construction Status Magnet Lowering & transportation 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  6. LHC Construction Status 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  7. LHC Construction Status 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  8. Instrumentation - what’s required & when • Sector test & first turn (end 2006 or early 2007) • Screens, BPMs, fast BCT, BLMs • Circulating beams at 450 GeV (end 2007) • DC BCT & lifetime • Tune Coupling & Chromaticity • Emittance: wire scanners. • Snapback and Ramp • Continuous Orbit, Tune, Coupling & Chromaticity (+ feedback) • Continuous emittance monitoring: synchrotron light, IPM • First Collisions • Luminosity • Schottky 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  9. Beam Position System Challenges • Choice of button electrode pick-up • Requires feedthroughs that can operate at ~4K • Maximise aperture & signal strength • Minimise transverse impedance • Dynamic Range • From 1 bunch of 1×109 charges to 2808 bunches of 1.7×1011 charges • 114dB dynamic range • Linearity • Better than 1% of half radius, ~130μm for arc BPMs • Over whole intensity range • Over large fraction of the aperture • Resolution • In the micron range for accurate global orbit control • Driven by collimation requirements • Over 120 collimator jaws in the LHC 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  10. Fast normalisation (< 25ns) bunch to bunch measurement Reduced number of channels (x2) normalisation at the front-end Signal dynamic independent of the number of bunches Input dynamic range ~45 dB Full LHC dynamic range ~114dB No need for gain selection ~10 dB compression of the position dynamic due to the recombination of signals Independent of external timing Currently reserved for beams with empty RF buckets between bunches LHC 400MHz RF 1 bunch every 10 buckets Tight time adjustment No Intensity information Propagation delay stability and switching time uncertainty are the limiting performance factors BPM Acquisition Electronics Amplitude to Time Normaliser Advantages Limitations 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  11. A + (B + 1.5ns) A B Beam 1.5ns B + 1.5ns The Wide Band Time Normaliser A B 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  12. A B A + 1.5ns 1.5ns B + (A + 1.5ns) Dt depends on position The Wide Band Time Normaliser A + (B + 1.5ns) A B 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  13. The Wide Band Time Normaliser A B A+(B+1.5ns) B+(A+1.5ns)+10ns Interval = 10  1.5ns System output 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  14. LHC Beam Position System Layout 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  15. What one can do with such a System Used extensively in CERN-SPS for electron cloud & instability studies. 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  16. ~ measurement noise !! Orbit feedback results from the CERN-SPS feedback off BPM Reading (m) 450 GeV Time (ms) feedback on ramp injection at 26 GeV Position distribution @ 100 Hz s = 8.5 mm 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  17. The LHC Beam Loss SystemCoping with a Huge Stored Beam Energy 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  18. The LHC Beam Loss System Role of the BLM system: • Protect the LHC from damage • Dump the beam to avoid magnet quenches • Diagnostic tool to improve the performance of the LHC 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  19. Full LHC fill 1 pilot bunch Dynamic Range Arc: 108 Collimator: 1013 BLM Detection Range • Pilot bunch of 5×109 close to damage level at 7TeV • Loss of 0.003% of nominal beam over 1s can create a quench at 7TeV 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  20. Design criteria: Signal speed and reliability Dynamic range (> 109) limited by leakage current through insulator ceramics (lower) and saturation due to space charge (upper) Secondary Emission Monitor (SEM): Length 10 cm P < 10-7 bar ~ 30000 times smaller gain Ionization chamber: N2 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, SEM: Ti) separated by 0.5 cm Low pass filter at the HV input Voltage 1.5 kV Beam Loss Detectors 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  21. BLM Threshold Level Estimation 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  22. BLM Acquisition Electronics Implemented on BDI DAB64x Threshold Comparator: Losses integrated and compared to threshold table (12 time intervals and 32 energy ranges). 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  23. Tune, Chromaticity & Coupling • Clear three step approach:1) Day 1 with kicked beams and classical motion analysis • Q kicker for both planes & both beams (limited to 2Hz rep rate) • Base Band Tune (BBQ) system for tune & coupling • Head-tail system for chromaticity • Chirp excitation using the transverse damper • allows faster repetition rate if required 2) Day N with PLL tune tracking (US-LARP) • Dp/p modulation via RF will allow chromaticity measurement 3) Day N++ with PLL measurement & Feedback (US-LARP) • Tune, chromaticity & coupling • For operational beams the additional problems will be: • lowering the excitation level to an insignificant level • coping with coupling • achieving compatibility with resistive transverse damping Collaboration with BNL via US-LARP 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  24. Measuring with Little or No Excitation – The Base Band Q Measurement (BBQ) System Direct Diode Detection (3D) 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  25. Record from the RHIC BBQ system Horizontal plane – no added excitation! 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  26. The BBQ System for the LHC • Will be installed in the LHC as: • Standard Q-meter • The acquisition system for the PLL system • Advantages • Sensitivity (noise floor of RHIC system in the 10 nm range) • Virtually impossible to saturate • Simplicity and low cost • Base band operation • Excellent 24 bit audio ADCs available • Signal conditioning / processing is easy • Independent of the machine filling pattern • Disadvantages • It is sensitive to the "bunch majority” • Gating needed to measure separate bunches (successful in Tevatron for pbars) • This is NOT foreseen for LHC start-up • Sensitive to rapid intensity changes (RHIC experience with beam loss) Test systems now installed in the SPS, PS, LEIR, RHIC & Tevatron 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  27. PLL Tune Measurement System Collaboration with BNL as part of the US-LARP programme • Advantages • Provides a continuous tune measurement & can be used for feedback • Precision a function of bandwidth (~10-5 for 1-10Hz) • Necessary for continuous coupling and chromaticity measurements • Can be used in a feedback loop • Problems • Requires constant excitation • For proton & heavy ion machines this implies small amplitudes. • PLL functioning strongly linked to Coupling • Large coupling can • cause PLL to jump from H to V tune peaks • break any tune feedback loop • Coexistence with transverse damping 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  28. Only horizontal tune shows up in horizontal FFT Vertical mode shows up & frequencies shift D Measurement of Coupling using a PLL Tune Tracker Start with decoupled machine Gradually increase coupling Fully coupled machine: D = |C-| FFT of Horizontal Acquisition Plane Ver Set Tunes V H Amplitude Hor Frequency 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  29. Measurement of Coupling using a PLL Tune Tracker Tracking the vertical mode in the horizontal plane & vice-versa allows the coupling parameters to be calculated 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  30. Tunes entirely defined by coupling Fully coupled Measurement of Coupling using a PLL Tune Tracker (RHIC Example) 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  31. Tune & Coupling Feedback at RHIC (2006) 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  32. TAN Luminosity Monitoring • Requires a region where signal is proportional to collision rate • Can be found in the neutral absorber (TAN) at ~150m from the IP • Ionisation chambers supplied by LBNL (Berkeley) as part of US-LARP • The Challenges • Has to withstand harsh radiation environment • Has to provide 40MHz bunch by bunch data with 1% relative accuracy 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  33. Copper Electrodes Ground Plane Macor Shell TAN Luminosity Monitor 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  34. Pre Amp Shaper 1FF ADC S&H 100ns 25ns 40MHz TAN Luminosity Monitor Cu Dipole 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  35. A1 A2 W1 W2 f2 f1 LHC Schottky Monitors • What does Schottky measurement offer • Non-invasive tune, chromaticity, momentum & emittance measurement • The Challenges • Obtaining Schottky data above coherent spectrum (GHz regime) • Allowing bunch to bunch measurements • Increasing signal to noise ratio to allow pilot bunch measurement • Keeping the impedance seen by the beam low in the coherent spectrum Tevatron Example 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  36. The LHC Schottky System 4.8 GHz 60 x 60 mm aperture x 1.5 meters long 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  37. LHC Schottky Monitors • LHC System Specifications • Based on FNAL travelling wave pick-up • 4.8 GHz center frequency • 200 MHz bandwidth minimum to allow bunch by bunch gating • One Horizontal and Vertical tank for each LHC ring • Gating on single or multiple bunches • Double down conversion • RF synchronous LO from 4.8GHz to 40MHz • Fixed LO from 40MHz to <100kHz • Digitisation using 24bit audio ADC 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

  38. Summary • The LHC beam instrumentation has moved from the R&D stage to the construction stage • Installation of most monitors is foreseen for the Autumn of 2006 • Significant progress made to address the remaining challenges • Much of this has been made possible through the US-LARP collaboration and the testing of new techniques on existing machines such as RHIC and Tevatron. • LHC to turn on with a comprehensive set of beam instrumentation Acknowledgements Many thanks to all the members of the Beam Instrumentation Group at CERN & our US-LARP collaborators for their input for this presentation. 12th Beam Instrumentation Workshop, May 2006 - Rhodri Jones (CERN - AB/BI)

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