Low Level RF

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 klystrons 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 lt 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 feedbacks calculated new
  phase/amplitude
• Need pulse shaping
• Pulse shaping would be entered manually
• Dont 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 latters 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