1. 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)

2. The LHC BPM System LEMPSE - 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 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

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

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

5. The LHC BPM System LEMPSE - Rhodri Jones (SL/BI) Interaction Region BPMs 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 Liquid Helium Capillaries Q2 Coupler

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

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

8. The LHC BPM System LEMPSE - Rhodri Jones (SL/BI) 1.5ns A B A + 1.5ns B + (A + 1.5ns) A + (B + 1.5ns) A B The Wide Band Time Normaliser  t depends on position

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

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

11. The LHC BPM System LEMPSE - Rhodri Jones (SL/BI) WBTN - Linearity v Intensity For LHC Arc BPMs 1% ~ 130  m

12. The LHC BPM System LEMPSE - Rhodri Jones (SL/BI) WBTN - Linearity v Position For LHC Arc BPMs 1% ~ 130  m

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

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

15. The LHC BPM System LEMPSE - Rhodri Jones (SL/BI) Timing Pick-up for the Experiments (BPTX) ~150m to the IP 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

16. The LHC BPM System LEMPSE - Rhodri Jones (SL/BI) 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?

17. The LHC BPM System LEMPSE - Rhodri Jones (SL/BI) 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 15 th March 2002!  All machine cabling to be ordered by 15 th May 2002 Any subsequent electronics  Keep in mind radiation resistance for electronics in the tunnel