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Low Level RF of ALBA (A preliminary study) Hooman Hassanzadegan

Low Level RF of ALBA (A preliminary study) Hooman Hassanzadegan. Cavity voltage (V probe ). Incident and reflected powers. Master Oscillator (500MHz). Circulator. Cavity. Drive signal. LLRF system. MO. Hi-power Amplifier. Tuner. Tuning control. Control system. Beam. HVPS.

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Low Level RF of ALBA (A preliminary study) Hooman Hassanzadegan

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  1. Low Level RF of ALBA (A preliminary study) Hooman Hassanzadegan

  2. Cavity voltage (Vprobe) Incident and reflected powers Master Oscillator (500MHz) Circulator Cavity Drive signal LLRF system MO Hi-power Amplifier Tuner Tuning control Control system Beam HVPS High Voltage Power Supply General view of the RF system The task of the LLRF is the regulation of the amplitude, frequency and phase of the RF wave.

  3. LLRF - hardware • Sensors for the incident, reflected and cavity power (Pinc, Prefl, Pprobe) • The required hardware for the isolation and amplification of the RF signals • The required Digital / Analog circuits for regulation, interfacing, ADC, DAC, signal processing, etc. • Drive power amplifier • PIN diode • Master oscillator • Other modules including auxiliary power supplies, PLL, Interlock, etc.

  4. Master Oscillator Control System Master Oscillator Drive Signal Control System Drive Signal Phase Regulation Phase Regulation Motor Control Mech. Phase Shifter Amplitude Regulation Variable Attenuator Phase Control Amplitude Control Elec. Phase Shifter RF Switch Mech. Phase Shifter Amplitude Regulation Pre - amplifier Klystron Amplifier Klystron Amplifier Cavity Cavity Amplitude and phase regulation loops a) Amplitude Regulation b) Phase Regulation

  5. Q Aprobe phase I I to I + Iin Iout - I to Q Q to I + Qin Qout + Q to Q I-Q demodulator and rotation matrix Demodulation: Modulation: Rotation matrix:

  6. General suggestions for ALBA LLRF • I-Q demodulation is more favourable, because two identical regulators will be used acting on baseband signals with wider phase control range compared to the traditional amplitude-phase loops. • It’s more desirable to use digital electronics which provides more flexibility, possibility of future changes by the software, better diagnostics and higher functionality compared to analog electronics.

  7. Amplitude / phase control (analog and digital) Digital module Ethernet Processor board (VME processor or Industrial PC) GUI Transition boards IP DAC DAC DAC DAC ADC Interlock Analog module Cosθ, Sinθ FF Gain Set Probe I+ I-Q mod Rotation Matrix I-Q dem I- Q+ Q- Pprobe MO 500 MHz Klystron Amplifier Cavity

  8. Amplitude / phase control (all digital) Digital Interface RF + + Learn Delay Cavity Amplifier + Set Points PID 2x2 Dig. to RF + + - Feed Forward Klystron Control IQ to ρφ ρφ Set points Forward IQ to ρφ RF to Dig. Reflected Resonance Control RF to Dig. Cavity RF to Dig.

  9. Tuner control Cavity RF IQ demodulator I Drive RF Q • Cavity tuner control: • An IQ demodulator detects the phase difference between the drive RF and the actual cavity voltage • The LLRF system drives the phase using the relation Arctan(Q/I) • The LLRF drives the cavity to maintain the desired phase difference

  10. Inputs / Outputs for LLRF controls • Cavity voltage control inputs: • Reference RF • Cavity Voltage • Cavity In-phase setpoint (FB) • Cavity Quadrature setpoint (FB) • IQ regulator gains • Cavity In-phase setpoint (FF) • Cavity Quadrature setpoint (FF) • Rotation matrix parameters • Cavity tuner control inputs: • Cavity voltage • Derive RF • Cavity tuner control outputs: • Cavity tuning In-phase (I) • Cavity tuning Quadrature (Q) Electrical and performance specifications of the Input / Output signals still have to be defined. • Cavity voltage control outputs: • Power amplifier drive • Cavity voltage In-phase monitor • Cavity voltage Quadrature monitor

  11. The first step – IQ demodulator • We’ll need it with both Digital and Analog Reg. • Detailed design is available • Comparably easy to build • Can be tested with a function generator

  12. The next steps I-Q demodulator (AD8348 from Analog Devices) - Can be designed and made at CELLS - Test with a function generator Other parts of the “Analog module” ADC, DAC and processor boards (“Digital Module”) - Off the shelf, but still need programming - will be done in collaboration with the Control Group 4. Test with simulated system Interfacing with the control system and GUI - Will be done mainly by the Control Group 6. Commissioning and trouble-shooting

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