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Low Level RF

Low Level RF. Outline Scope Local feedback loop requirements Solutions Costs How this fits into global feedback Other signals Conclusions. Scope. The low level RF controls system consists of RF phase and amplitude controls at these locations: Laser Gun L0-A (a.k.a. L0-1)

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Low Level RF

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  1. Low Level RF • Outline • Scope • Local feedback loop requirements • Solutions • Costs • How this fits into global feedback • Other signals • Conclusions

  2. Scope • The low level RF controls system consists of RF phase and amplitude controls at these locations: • Laser • Gun • L0-A (a.k.a. L0-1) • L0-B (a.k.a. L0-2) • L0 Transverse cavity • L1-S • L1-X • L2 – using 2 klystrons to control avg phase/ampl of L2 • L3 Transverse cavity • L3 - here is a bit different (lots of klystrons!)

  3. Local feedback loop requirements • At each of these locations, the klystron’s phase and amplitude will be controlled • Inputs are listed in Appendix A • Example inputs (for the gun) are: • Cell 1 RF monitor. ½” heliax. Phas/ampl 5us 120 Hz • Cell 2 RF monitor ½” heliax. Phas/ampl 5us 120 Hz • RF in FOR. ½” heliax. Phas/ampl 5us 120 Hz

  4. Off-the-shelf solution

  5. Off-the-shelf solution • Test/measure digitizer performance: when clock increases from 105 MHz to 119 MHz, are bits lost? • Talking to vendors re: arbitrary function generator (ensure noise < 0.1% ) for pulse shaping with carrier board • Define interface to PAD • Adapt available driver and device support for digitizer to RTEMS

  6. In-house solution

  7. In-house solution: alternate choice • Requires development of FPGA-based board with ethernet • On-board processing capability for local feedback • Places the digitizers next to the low noise RF components (eliminates transmission of low noise analog signals outside the chassis)

  8. L3 solution

  9. Costs • In operation, 9 instances of • VME chassis: 6000 € • PowerPC: 5000 USD • Fast digitizer: 5000 USD • Fast DAC module in carrier board: $unknown • Additional digitizer for waveforms: ~3000K • Analog module for temperatures: ~2000K And 1 instance (of same) for testing/spares • At L3, 1 instance of • VME chassis: 6000 € • PowerPC: 5000 USD • Additional digitizer for waveforms: ~3000K • Analog module for temperatures: ~2000K

  10. How this fits into global feedback

  11. How this fits into global feedback

  12. How this fits into global feedback

  13. How this fits into global feedback

  14. How this fits into global feedback

  15. How this fits into global feedback

  16. Other signals – (listed in Appendix A) • Control signals • This is the feedback’s calculated new phase/amplitude • Need pulse shaping • Pulse shaping would be entered manually • Don’t know where yet • Very low processing load

  17. Conclusions • By using multiple VME chassis (10 over injector, sectors 24 & 30), the LCLS LLRF raw signals can be processed by the CPU in time to send out phase and amplitude corrections and have them settle within a beam pulse. • When there is beam, this system will integrate with the beam-based longitudinal feedback by accepting the latter’s RF phase and amplitude corrections and passing them on.

  18. Appendix A RF Cables - Monitor and Control Signals – from LCLS ESD 1.2-137 (Akre, Hill) Legend: Monitor. Feedback. Control. From RF HUT Sub-system Signal Name Cable Type To Location Signal Type Laser RF Reference 1/2" Heliax Laser Room Phas/Ampl CW Laser Oscillator Out 1/2" Heliax Laser Room Phas/Ampl CW 120Hz Laser Pulse 1/2" Heliax Laser Room Phas/Ampl picoSec RF Control RF Hut Phas/Ampl CW Gun Cell 1 RF Monitor 1/2" Heliax Gun Phas/Ampl 5uS 120Hz Cell 2 RF Monitor 1/2" Heliax Gun Phas/Ampl 5uS 120Hz RF In FOR 1/2" Heliax Gun Phas/Ampl 5uS 120Hz RF In REFL 1/2" Heliax Gun Phas/Ampl 5uS 120Hz RF Control 1/2" Heliax 20-6 120Hz

  19. Appendix A continued L0-A RF In FOR 1/2" Heliax L0-1 Phas/Ampl 5uS 120Hz RF In REFL 1/2" Heliax L0-1 Phas/Ampl 5uS 120Hz Load FOR 1/2" Heliax L0-1 Phas/Ampl 5uS 120Hz Load REFL 1/2" Heliax L0-1 Phas/Ampl 5uS 120Hz RF Control 1/2" Heliax 20-7 120Hz L0-B RF In FOR 1/2" Heliax L0-2 Phas/Ampl 5uS 120Hz RF In REFL 1/2" Heliax L0-2 Phas/Ampl 5uS 120Hz Load FOR 1/2" Heliax L0-2 Phas/Ampl 5uS 120Hz Load REFL 1/2" Heliax L0-2 Phas/Ampl 5uS 120Hz RF Control 1/2" Heliax 20-8 120Hz

  20. Appendix A continued L0- Transverse RF In FOR 1/2" Heliax L0- Transverse Phas/Ampl 5uS 120Hz RF In REFL 1/2" Heliax L0- Transverse Phas/Ampl 5uS 120Hz Load FOR 1/2" Heliax L0- Transverse Phas/Ampl 5uS 120Hz Load REFL 1/2" Heliax L0- Transverse Phas/Ampl 5uS 120Hz RF Control 1/2" Heliax 20-5 120Hz L1-S SLED Out FOR 1/2" Heliax 21-1 SLED Out REFL 1/2" Heliax 21-1 ACC A/B In FOR 1/2" Heliax 21-1 Phas/Ampl 5uS 120Hz ACC A/B In REFL 1/2" Heliax 21-1 Phas/Ampl 5uS 120Hz ACC C IN FOR 1/2" Heliax 21-1 Phas/Ampl 5uS 120Hz ACC C IN REFL 1/2" Heliax 21-1 Phas/Ampl 5uS 120Hz Load A/B FOR 1/2" Heliax 21-1 Phas/Ampl 5uS 120Hz Load A/B REFL 1/2" Heliax 21-1 Phas/Ampl 5uS 120Hz Load C FOR 1/2" Heliax 21-1 Phas/Ampl 5uS 120Hz Load C REFL 1/2" Heliax 21-1 Phas/Ampl 5uS 120Hz RF Control 1/2" Heliax 21-1 120Hz

  21. Appendix A continued L1-X KLY Out RF FOR 3/8" Heliax 21-2 Phas/Ampl 2uS 120Hz KLY Out RF REFL 3/8" Heliax 21-2 Phas/Ampl 2uS 120Hz ACC In FOR 3/8" Heliax 21-2 Phas/Ampl 2uS 120Hz ACC In REFL 3/8" Heliax 21-2 Phas/Ampl 2uS 120Hz Load FOR 3/8" Heliax 21-2 Phas/Ampl 2uS 120Hz Load REFL 3/8" Heliax 21-2 Phas/Ampl 2uS 120Hz FB Control 3/8" Heliax 21-2 120Hz L3-Transverse RF In FOR 1/2" Heliax 25-5A Phas/Ampl 5uS 120Hz RF In REFL 1/2" Heliax 25-5A Phas/Ampl 5uS 120Hz Load FOR 1/2" Heliax 25-5A Phas/Ampl 5uS 120Hz Load REFL 1/2" Heliax 25-5A Phas/Ampl 5uS 120Hz RF Control 1/2" Heliax 24-8 120Hz

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