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PSB C04 RF system Consolidation or upgrade? M. Paoluzzi – CERN BE-RF

PSB C04 RF system Consolidation or upgrade? M. Paoluzzi – CERN BE-RF. C02 : 4 cavities in 2 straight sections freq= 0.6-1.8 MHz Vgap=8 kV Rs≈350 Ω seen by the beam C04 : 4 cavities in 1 straight section freq 1.2 3.6 MHz Vgap=8 kV Rs≈350 Ω seen by the beam

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PSB C04 RF system Consolidation or upgrade? M. Paoluzzi – CERN BE-RF

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  1. PSB C04 RF system Consolidation or upgrade? M. Paoluzzi – CERN BE-RF

  2. C02 : 4 cavities in 2 straight sections freq= 0.6-1.8 MHz Vgap=8 kV Rs≈350Ωseen by the beam C04 : 4 cavities in 1 straight section freq 1.2 3.6 MHz Vgap=8 kV Rs≈350Ωseen by the beam C16 : 4 cavities in 1 straight section freq 6.0- 16 MHz Vgap=6 kV Rs≈2 kΩ seen by the beam

  3. Consolidation foreseen C02, C16 • Replacement of ITL, power supplies, cables • (rebuilt the systems keeping the cavities and amplifiers) • Possibly move AVC and Tuning loops to Low Level • Consolidation foreseen C04 • Same as above but power stage replacement • (improve mean available power and current for beam • loading compensation) • Is it the time to envisage a technology change?

  4. Narrow band Tuned systems Highly optimized Almost no room for Vgap increase Further reduction of Rs very difficult

  5. Finemet LEIR Cavity • A single cavity covers the range 0.35÷5 MHz • Cavity length 0.5 m • Gap voltage 4 kV (tested at 5 kV) • No tuning • AVC integrated in Low Level • But… • … diameter incompatible with PSB overlapped rings

  6. Finemet in PSB • Maximum outer diameter OD=330mm • Inner diameter ID=200mm • Standard Finemet thickness 25mm • Two kind of material: • Standard LEIR like : FT3M (data available from small rings) • New low loss : FT3L (Thanks to KEK and Chihiro Ohmori for • providing data)

  7. Air cooling test on small rings (OD=133mm) : • Simple blower on each ring side • With 500kW/m3 t MAX≈70°C • Maximum inside temperature unknown • Limit temperature • Suggested from Hitachi t MAX≤100°C • KEK booster experience t MAX≈100°C • J-PARC experience t MAX≈200°C for few hours

  8. Minimum peak voltage 380V for FT3L 300V for FT3M @ 1 MHz Note: f Injection ≈1 MHz with LINAC4 One C04 cavity contains 50 rings In the range 1÷4 MHz : VGAP=15÷17 kV with FT3M VGAP=19÷29 kV with FT3L

  9. Basically working on a capacitor Almost no difference with increased number of rings

  10. Alternative approach based: use two rings (FT3L) and 1 gap Each ring can accept 500pF and still cover the 1÷4 MHz band . RPmin is ≈100 Ω (per ring) P≈1500W for 700V across two rings This can be supplied by a solid-state amplifier (in PSB solid state amps used since 1987!!!)

  11. Sine shape approximation Beam current φL , TL For a pure h1 or h2 beam, the beam peak current is 22.7 A @ ej 1st rf harmonic : ÎH1 = 9.56 A 2nd rf harmonic: ÎH2 = 6.06 A w/o acceleration, the h1 bunch length: φL 138o (2.4 rad or 220 nsh1 @ej.) Total charges per bunch= 2 E13h1 (sinus shape approx.) Slide provided by A. Blas CERN BE-RF

  12. MRF157 Mosfet 600W up to 80MHz To provide 800W (2 units push-pull) ID-peak≈32A ID-DC≈10A MRF151 Mosfet 150W to 175MHz To provide 200W (2 units push-pull) ID-peak≈12A ID-DC≈4A

  13. Shunt resistance of each gap Rs≈200 Ω • To get the present 8kV need 12 gaps • Total impedance seen by the beam Rstot≈2400 Ω • Impedance of present cavities (including FB) ≈350 Ω • We must reduce Rstot and compensate beam loading with: • ≈20 dB RF feedback seems possible with 10 ns delay in the loop. • 1 turn feedback: difficult (nevertheless possible) because revolution time is only ≈500 ns at extraction. • Combination of both

  14. The cavity could be used as combiner for push-pull operation and driven by 2 amplifiers similar to the LEIR 1kW drivers. The total power could easily be brought to 2 x 2 kW simply increasing the DC supply by 15%. The 120W (200W) power module delay is 12 ns and the 9 ways combiner 4ns. Both could be reduced and 10 ns total seems within reach.

  15. Simulated system response: 1 Finemet ring driven by 9 combined 200W modules and feedback including delay . 200W module. 1 ring impedance. Amplification chain response.

  16. Advantages • Modular system. • Reduced machine space and/or increased installed voltage. • Possibility of installing spare cavities as hot back-up. • No tuning loop. • Simplified solid-state system. • Risks • Additional new system at restart with LINAC4. • New technology and configuration. • Complete new design.

  17. How could we proceed… • 2010-2011 Design and produce a first section. • … if successful then: • 2012 produce and install and test a full set of cavities for the required 8 kV. • They should fit in the place of one of the present C04 cavities. • 2013 Tests with beam (1 ring and C02 system still in place) • … if successful then: • 2014-2015 Proceed with full scale construction and • C02/C16 renovation • 2016 Installation • … but for security • 2011 Design a first C04 improved RF power amplifier. • 2012 Produce and install C04 improved RF power amplifier. • 2013 Tests with beam (1 ring) • 2014-2015 Depending on 2013 tests start C02/C04/C16 renovation or • stop C04 renovation it and proceed with new system. • 2016 Installation

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