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The LHC Beam Position System

The LHC Beam Position System. Ad-hoc Working Group on LHC Experiment-Machine Parameter and Signal Exchange 26 th March 2002 Rhodri Jones (SL/BI). LHC BPM System - General. 100 Warm, Button Electrode BPMs (LEP) for TI2 & TI8 922 Button Electrode BPMs (24mm) for Arc & DS

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The LHC Beam Position System

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  1. The LHC Beam Position System Ad-hoc Working Group on LHC Experiment-Machine Parameter and Signal Exchange 26th March 2002 Rhodri Jones (SL/BI)

  2. LHC BPM System - General • 100 Warm, Button Electrode BPMs (LEP) for TI2 & TI8 • 922 Button Electrode BPMs (24mm) for Arc & DS • 44 Warm Button Electrodes BPMs for IR3 & IR7 • 44 Enlarged Button BPMs (34mm) for IR1,2,5 & 8 • 24 Directional Couplers for IR1,2,5 & 8 • ~ 24 Special BPMs for Transverse Damper, Tune & Chromaticity Measurements in IR4 • 1 BPTX “timing pick-up” per incoming beam for IR1,2,5 & 8 • Total of 1166 BPMs for the LHC and its Transfer Lines LEMPSE - Rhodri Jones (SL/BI)

  3. The Arc BPM - SSS Layout LEMPSE - Rhodri Jones (SL/BI)

  4. 49mm aperture 24mm button Arc BPM - Button Feedthrough Button Feedthrough Beam Screen Liquid Helium Cooling Capillary LEMPSE - Rhodri Jones (SL/BI)

  5. Interaction Region BPMs Liquid Helium Capillaries • Stripline length 120mm to give same response as button • 2 Types • Warm Coupler - capable of withstanding bake-out to 200°C • Cold Coupler - located in Q2 cryostat (tilted by 45° for cryostat integration) • Directivity measured as 28dB at 200MHz Stripline Electrode Q2 Coupler LEMPSE - Rhodri Jones (SL/BI)

  6. The Front-End Electronics LEMPSE - Rhodri Jones (SL/BI)

  7. A + (B + 1.5ns) A B Beam 1.5ns B + 1.5ns The Wide Band Time Normaliser A B LEMPSE - Rhodri Jones (SL/BI)

  8. 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 LEMPSE - Rhodri Jones (SL/BI)

  9. The Wide Band Time Normaliser A B A+(B+1.5ns) B+(A+1.5ns)+10ns Interval = 10  1.5ns System output LEMPSE - Rhodri Jones (SL/BI)

  10. The Wide Band Time Normaliser LEMPSE - Rhodri Jones (SL/BI)

  11. WBTN - Linearity v Intensity For LHC Arc BPMs 1% ~ 130mm LEMPSE - Rhodri Jones (SL/BI)

  12. WBTN - Linearity v Position For LHC Arc BPMs 1% ~ 130mm LEMPSE - Rhodri Jones (SL/BI)

  13. Very Front-End WBTN Card 70MHz Low Pass Filters Supplied by TRIUMF (Canada) 1310nm Diode Laser Transmitter Single-Mode Fibre-Optic Link VME based Digital Acquisition Board TRIUMF (Canada) WBTN Mezzanine Card (10bit digitisation at 40MHz) The LHC BPM Acquisition System Tunnel Surface LEMPSE - Rhodri Jones (SL/BI)

  14. 3 = 750mm 20% of 4mm Closed Orbit ‘budget’ (Spec = 500mm) Accuracy and Resolution LEMPSE - Rhodri Jones (SL/BI)

  15. ~150m to the IP Timing Pick-up for the Experiments(BPTX) • Located ~150m from the IP in front of the D2 Magnet • One BPTX either side of the IP on the incoming beam • Exclusively used by the experiments LEMPSE - Rhodri Jones (SL/BI)

  16. BPTX Requirements? Choice of Pick-up? • Stripline Coupler? • Peak voltage (one button) of ~20V after 200m of cable for nominal bunch • Peak voltage (one button) of ~1V after 200m of cable for pilot bunch • Button Electrode BPM? • Peak voltage (one button) of ~5V after 200m of cable for nominal bunch • Peak voltage (one button) of ~250mV after 200m of cable for pilot bunch • Other Type of Pick-up? Type of Signal? • Sum signal (sum of all 4 pick-up electrodes  2  peak voltage)? • Virtually independent of position & requires only 1 cable • Sum and Delta Signal? • Requires 3 cables to give sum, horizontal position & vertical position • Other Type of Signal? LEMPSE - Rhodri Jones (SL/BI)

  17. Next Steps SL/BI will supply: • 2 BPTX Pick-ups per Experiment • Choice of pick-up in collaboration with Experiments Experiments responsible for: • Cabling • All machine cabling to be defined by 15th March 2002! • All machine cabling to be ordered by 15th May 2002 • Any subsequent electronics • Keep in mind radiation resistance for electronics in the tunnel LEMPSE - Rhodri Jones (SL/BI)

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