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Design Parameters Cavity Requirements Power Sources Distribution options

Explore the essential design parameters and cavity options for the EMMA RF system in the FFAG accelerator, including power source choices, distribution methods, and tuning requirements.

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Design Parameters Cavity Requirements Power Sources Distribution options

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  1. EMMA RF System Carl Beard, Emma Wooldridge, Peter McIntosh, Peter Corlett, Andy Moss, James Rogers, Joe OrrettASTeC, Daresbury Laboratory • Design Parameters • Cavity Requirements • Power Sources • Distribution options FFAG 07 Carl Beard

  2. EMMA RF Specification FFAG 07 Carl Beard

  3. Design Parameters • 1.3 GHz chosen for EMMA to both: • Match ERLP RF systems and • To utilise developed RF infrastructure: • RF power sources • LLRF systems • Compact Size • Updated RF cavity design constraints: • Beam aperture 40mm • Cavity length (flange to flange) 86mm (110mm) • Accelerating voltage per cavity of 120kV (for 19) up to 180kV Future Upgrade • RF power source availability i.e. IOTs or klystrons FFAG 07 Carl Beard

  4. Proposed Cavity Design * LLRF + Distribution FFAG 07 Carl Beard 40mm 90mm 86mm

  5. Cavity Tuning • Single Tuner • Optimised for required tuning range • +1.5 to – 4 MHz. • Reduction in Rsh to 4.15 FFAG 07 Carl Beard

  6. RF Leakage • Broadening of the beam pipe leads to leakage of RF flux • The field strength has to be low enough to avoid interference with the BPMs • At 150 mm, the fields have decayed to 0.1V • Requirement is <0.5V • Closest BPM is located ~200mm away FFAG 07 Carl Beard

  7. Options Thales IOT 30 kW (Pulsed) No PSU e2v Amplifier 20 kW (Pulsed) e2v Klystron 160 kW (CW) >170 kW (Pulsed) CPI IOT 30 kW (CW) No PSU etc FFAG 07 Carl Beard

  8. IOTs • e2v 116LS • 16kW CW integrated amplifier system • Dual 19”rack configuration • Integrated HVPS, IOT and controls • Tests at DL in Mar 2006  achieved 20kW pulsed at 1.5ms/20Hz • Multiple IOTs to be powered from 1 PSU • Thales TH713 • 20kW CW independent IOT • Thales are developing an IOT amplifier solution • Tests at Thonon in Sept 2006  achieved 30kW pulsed at 1.5ms/20Hz • CPI CHK51320W • 30kW CW independent IOT • CPI are developing IOT amplifier solution • >30kW Pulsed should be possible, but no indication of figure available. FFAG 07 Carl Beard

  9. IOT Options • PSU, Controls and Pre-amp required for CPI/Thales IOT (integrated Amplifier is being developed for both) FFAG 07 Carl Beard

  10. Klystron Options • 160kW (possibly 170 kW) klystrons are available from e2v • PSU, Pre-amp, Cooling systems required • PSU Requirements - 45kV, 5.8A FFAG 07 Carl Beard

  11. Klystron Overhead large, even at 180 kV per cavity Single device Cost for the PSU and time to reconfigure very large Single failure of the Klystron would result in long down time Efficiency and linearity of Klystrons mean the power delivered to the cavity is much reduced IOT Off the shelf product – fast replacement Integrated amplifier would be simplest option High efficiency Minimal overhead required for power Single failure of the Klystron would result in long down time Full reconfiguration would be required to upgrade to 180 kV per cavity. Power Source Options FFAG 07 Carl Beard

  12. PSU’s On-site • Thales PSU • 0.5 MW • 10 Amps, 50 kV. • Currently in use on SRS • Available from 2009, Upgrade for EMMA is costly • Crowbar Power Supply • 0.8 MW • 52 kV – 16 Amps • Original SRS/NINA Klystron PSU • Needed to operate 2 e2v klystrons FFAG 07 Carl Beard

  13. Distribution Losses • RF Losses in Waveguide << Losses in Coax. • To minimise losses waveguide needs to be close to the cavity • Coaxial Lines Losses can be as high as 0.5dB • Mainly due to connectors • Also dependent on length of Line Connector Losses = (-0.012 dB x F(GHz)) x 2 Cable Losses = -0.05 dB/Foot x 10 = 0.5 dB Total Losses = 0.6 dB Therefore Assume 1 dB Losses (20%) For a 2 M Coaxial Cable FFAG 07 Carl Beard

  14. Cascaded Distribution Circulator 7dB 6dB 3dB 4.8dB Load IOT 3-Stub Tuner • The same regardless of number of splits. • Compact System • Single Cavity Amplitude Phase and Amplitude not possible • Klystron option similar (1 Klystron feeds all 19 cavities) FFAG 07 Carl Beard

  15. IOT Distribution (Split) • Fewer Circulators are required • Odd Number splits complicate the system. • Single Cavity Amplitude Phase and Amplitude not possible • Large Waveguide Distribution 3dB 3dB 7dB IOT 3dB FFAG 07 Carl Beard

  16. LLRF Distribution Phase Shifter SS Amp Amplitude Control Master Oscillator IOT Comparator Level Detector Comparator Mixer • In the combined systems only takes feedback from a single cavity • Phase control of the cavity group is possible • Individual IOTs for each cavity required for separate Amplitude and Phase adjustment • The string of cavities would be phased locked to the control cavity FFAG 07 Carl Beard

  17. Cavity Splitter Klystron IOT IOT + Vastly Simplified RF distribution - Requires development – RF and Mechanical Design FFAG 07 Carl Beard

  18. Prototype Combiner FFAG 07 Carl Beard

  19. Summary • Cavity has been designed with sufficient tuning range, and high efficiency to reduce the demand on the RF power requirement • Fields are sufficiently small to avoid interference with BPMs • Cascaded RF Distribution would be the optimum since space is valuable. • Fast, individual cavity amplitude and phase control not possible with this system. • Slow Phase adjustment is possible through motorised Phase shifters. • Klystron option would have the highest risk in case of Klystron failure. • IOT Amplifier option would be the advised option. FFAG 07 Carl Beard

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