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Other Utilities of ALBA LLRF

Other Utilities of ALBA LLRF. Angela Salom. CWRF 2010, CELLS – Barcelona. Introduction. ALBA LLRF System Based on a commercial FPGA board (Lyrtech VHS-ADAC) Analog Front Ends for pre-processing of RF signals Amplitude, phase and tuning loops implemented. Analog Front End.

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Other Utilities of ALBA LLRF

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  1. Other Utilities of ALBA LLRF Angela Salom CWRF 2010, CELLS – Barcelona

  2. Introduction ALBA LLRF System • Based on a commercial FPGA board (Lyrtech VHS-ADAC) • Analog Front Ends for pre-processing of RF signals • Amplitude, phase and tuning loops implemented Analog Front End Lyrtech Digital Board Main Feature of Digital Systems: Flexible and Fast

  3. Other LLRF Utilities Other Capabilities integrated in LLRF • Automated Start-up • Conditioning Manual Automatic • Fast Diagnostics (Fast Data Logger) • Fast Interlocks • Frequency modulation for tuning Features implemented in the same LLRF Hardware All features available in all the RF plants

  4. Automated Start-up After a trip LLRF set all parameters to minimum • Low RF Drive • Tuning Disable • Amplitude and Phase loops opened Reset the interlock and switch on transmitter LLRF detects RF presence in cavity LLRF tune cavity before increasing power LLRF closes Loops (Amp & Ph) Smooth power increase Message: Ready for beam operation RF Power Tuning pulses Plungers direction

  5. Manual Conditioning RF Drive square modulated • Duty Cycle of pulses adjustable (1-100%) • Amplitude adjustable • Time between pulses = 100ms (10Hz) • Tuning Loop only enable at top of the pulses Drawbacks • Operator needed to adjust amplitude and duty cycle • Vacuum levels not considered by LLRF  frequent interlocks

  6. Automated Conditioning • Amplitude and duty cycle increase depending on vacuum levels • Amplitude increase rate (slope): adjusted by operator • Vacuum signal connected to LLRF Voltage Increase rate set to 0.03mV/s Voltage Decrease rate set to 1mV/s • Vacuum < Limit Down  Voltage Amplitude Increases/Decreases • Vacuum > Limit Up  Voltage Amplitude remains constant until vacuum is below limit down

  7. Vacuum Trip at 47kW Cav Volt 35μs Reflected Trip at 35kW Arc at 41kW Cav Volt Cav Volt Fw IOT Fw Cav Fw Cav 4μs Rv Cav Rv Cav Rv Cav Cavity Discharged in 35μs Cavity Discharged in 0.8μs Cavity Discharged in 1.2μs RF Fast Diagnostics Fast Data Acquisition (MHz) for post-mortem trip analysis: Vacuum, Arcs and Ref Power)

  8. Reference Cav Volt Characterization of Cavity Transfer Function • Transfer Function: Mathematical representation of a system (model) • to be calculated analytically • to be measured experimentally • Experimentally: Step response in Open Loop System Characterization (1st Order) • Delay = 1.93μs • ζ(63%) = 9.7 μs • Gain = 0.8 • Filling time = 29.3 μs (DAMPY Cavity) Transfer Function

  9. Master FPGA Board QRef IRef + I Ctrl - DAC 1 PI RF Drive Modulator + - PI DAC 2 Q Ctrl RF Cavity voltage IQ Phase RF Switch ( IF ) Δφ demod detector PI DAC 8 - IQ ( Cordic ) Master + MO demod Fw Cav ( IF ) RF Output φ reference GPIO RF Synthesizer Switch Control Frequency Input ( LVTTL ) modulator Freq Control Frequency Tuning Frequency Tuning for Startup (RFQ Cavity) • Sometimes during startup, tuning by cooling control cannot cope with the temperature increase induced by RF power  Freq Tuning • Cavity Resonance Frequency varies freely • RF Drive modulation to follow the resonance frequency of cavity

  10. Fast Interlocks integrated in LLRF Main Functionality • To cut RF Drive when an interlock happens (<10 μs) Interlock Conditions • Reflected power above limits (RF Inputs) • Vacuum peaks (Digital Input) • Arcs (Digital Input) • External Input from general control system Other Fast Interlock Actions • Circular buffer trigger • Loops Disable • DACs Disable • Communication to general control system

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