Transcript Slide 1
PSB C04 RF system Consolidation or upgrade? M. Paoluzzi – CERN BE-RF 7/18/2015 1 C02 : 4 cavities in 2 straight sections freq= 0.6-1.8 MHz Vgap=8 kV Rs≈350Ω seen by the beam C04 : 4 cavities in 1 straight section freq 1.2 3.6 MHz Vgap=8 kV Rs≈350Ω seen 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 7/18/2015 2 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? 7/18/2015 3 Narrow band Tuned systems Highly optimized Almost no room for Vgap increase Further reduction of Rs very difficult 7/18/2015 4 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 7/18/2015 5 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) 7/18/2015 6 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 7/18/2015 7 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 7/18/2015 8 Basically working on a capacitor Almost no difference with increased number of rings 7/18/2015 9 Alternative approach based: use two rings (FT3L) and 1 gap 10 -15 CM A RI NI FN I EM E T VACUUM CH AM BER G AP Each ring can accept 500pF and A RI O U T 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!!!) 7/18/2015 10 Beam current Sine shape approximation ˆsin ( )d d 0 0 L arg e ˆ BunchCh BunchCh arg e 2 L L cos L 0 L BunchCh arg e L L Iˆ dQ d ˆ 2 2BunchCh arg e ˆdQ I max max dt d dt T T RF RF L φ L , TL 19 13 6 2 1.610 210 3.210 6 ˆ@ I ej 13 10 F 22 .7A @ ej RF peak T 138 180 T 0 . 77 RF RF 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.) 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 Slide provided by A. Blas CERN BE-RF 11 7/18/2015 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 7/18/2015 12 • 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 7/18/2015 13 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. 7/18/2015 14 Simulated system response: 1 Finemet ring driven by 9 combined 200W modules and feedback including delay . 200W module. Amplification chain response. 7/18/2015 1 ring impedance. 15 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. 7/18/2015 16 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 7/18/2015 17