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    BI/TB on AWAKE BPM electronics, LHC BCW calibration electronics and LHC readiness

    → Europe/Zurich
    864 2-B14 (JB Adams) (CERN)

    864 2-B14 (JB Adams)

    CERN
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    AWAKE BPM

    • Spec
      • Single bunch 5E9 to 3.5e11 (37dB)
      • 100um resolution with 50um near plasma cell
    • System
      • 4 BPK, 21 button
      • F-E electronics in tunnel
      • Series communication via copper links or optical fibres
    • F-E Electronics
      • 800MHz LP adapters
      • 77MHz LP + 20MHz BP
      • Log Amp which produces sum & difference internally
    • Acquisition
      • Sampling at 40MS/s
    • Tests
      • Slope changes slightly with intensity
        • Due to DC coupling or LogAmp characteristics
      • Button - 1dB ~1mm
        • For high intensity achieve ~50um resolution
        • For low intensity achieve ~500um resolution
      • Added amplifier to increase signal for low intensity
    • Status
      • 100 Adapters under production
      • 30 F-E crates & PS ready
      • 50 ADC boards to be tested
      • 60 Log-amp boards under production
      • Firmware
        • Transmission protocol complete
        • Data processing under development
    • Installation and hardware commissioning:
      • TT41 installation foreseen early May
      • Transfer-line accessed from SPS will have to wait technical stop (early June)
      • (First beam tests foreseen July)

    FBCT Calibration

    • WCM internal PCB
      • Beam current
        • Low impedance & good RF performance
      • Calibration path
        • Low DC resistance & high RF impedance to decouple from beam
        • Made for calibration with current
    • Beam coupling to calibration winding introduces error to beam current measurement
      • Decoupling with ferrite beads (-30dB @ 40MHz)
    • For 2016 using DABs & IBMS
      • Cross calibration with DCCTs
      • Bench top 5us square pulse generator for cross channel correction
    • For future with FMS ADCs
      • Only need amplitude
      • Precise calibration only with current source
        • Slow pulses tens of us
      • Low load is essential to avoid power dissipation in PCB
    • Proposal for new calibrator - first version
      • Use 1 current source with switches to distribute between WCMs
      • Current source with 10ppm shot-to-shot stability
      • 100ppm accuracy
      • 5us switch-on-time
      • 1.5A for R-cal 10 Ohms & R-ref 5 Ohms
        • Could increase current if R-ref is reduced (Hermann)
      • Current measurement using half-bridge principle
        • Know Vref with Rref & zero bridge
        • Rely on zero measurement - offsets?
    • Next version
      • Controls
      • Internal ADCs to monitor reference voltage
    • Further discussion:
      • Cross check calibration with antenna measurement
      • How to calibrate at 1% of full scale with this generator?
      • Should not have ethernet connection to avoid calibration with beam present
        • WCM will be used for dI/dt in 2016

    LHC Status:

    • Question about new BPM firmware to be decided shortly
    • Present schedule says first beam week after Easter (25/3)
    • Likely some transfer-line shots during week before Easter if possible.
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