1 / 27

C oupled C avity L inac RF design

C oupled C avity L inac RF design. G. De Michele, PhD. Outline. CCL RF design Tank Design Bridge Coupler Design RF F eedthrough Design Low Power Measurements Beadpull Measurements and Tuning High Power Measurements. Outline. CCL RF design Tank Design Bridge Coupler Design

fiona-english
Download Presentation

C oupled C avity L inac RF design

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CoupledCavityLinacRF design ADAM SA G. De Michele, PhD

  2. Outline • CCL RF design • Tank Design • Bridge Coupler Design • RF Feedthrough Design • Low Power Measurements • Beadpull Measurements and Tuning • High Power Measurements ADAM SA

  3. Outline • CCL RF design • Tank Design • Bridge Coupler Design • RF Feedthrough Design • Low Power Measurements • Beadpull Measurements and Tuning • High Power Measurements ADAM SA

  4. CCL Overview ~24 m CoupledCavityLinac ADAM SA • Use 10 power units, 7.5 MW each • Maximum power /unit = 5.2 MW (70% of 7.5MW) • Kilpatrick factor < 2.0 • ΔETOT : 32 MeV  230 MeV • ΔEp ≤ 20 MeV / klystron 20cm beam CouplingCells AcceleratingCells End Cells ~27cm

  5. CCL RF Design • A tank is designed with the main design parameters: • Cell length, gap length, septum thickness, the number of cells • With the following objectives: • The tankis resonant at the design frequency of 2998MHz • The cell length is consistent with the particle speed (l=β·λ/2) & RF phase • The effective shunt impedance is maximum (within constraints) • The constraints are: • The peak field • The feasible range of geometrical dimensions • Tracing the synchronous particle, we find a new energy & RF phase. • Design the next tank until: • The design energy is reached or • The available klystron power is used up ADAM SA

  6. Double Chain of Resonators • The double chain of resonatorsoperates in the so-calledπ/2 mode • Very stable working mode w.r.t. the geometry variations • The spacingbetween the workingfrequency and itsneighbor modes is largerthan in anyother mode • Requirements • Stop Band (SB) about 1MHz • Couplingbetween the accelerating (ACs) and coupling (CCs) cells at about 3%  better modes separation • Field uniformity • Field in CCs about 1% fields in ACs ADAM SA SB=fπ/2-(f+ - f-)/2 π/2 mode

  7. SimplifiedGeometry for RF 3D Design • 5 cells (2 ACs and 3 CCs) geometry • Adjustcells dimensions to uniform the E field, right workingfrequencyand minimize the E fieldinside the CCs • Replicatethe geometry for the full tank design and introduce at the same time the End Cells • Nowthe structure isfinite. The End Cells have to beadjusted in order to keep the fielduniformitywithinspecs Advantages: simulation time drasticallyreduced. Only fine tuningwillbeperformed on the wholesimulated tank. ADAM SA

  8. CCL Tank Design Vacuum Model • Hic suntleones ADAM SA k=2.8% SB=950kHz

  9. Final Geometrical Tank Parameters ADAM SA

  10. Tolerances The fielduniformity of the tank willdramaticallyget worse for a variation of +/-20um on the outer corner radius of the end cells. ADAM SA ±10um The freq. variation of the accelerating cellis1.3MHz/10um. ± 20um

  11. Outline • CCL RF design • Tank Design • Bridge Coupler Design • RF Feedthrough Design • Low Power Measurements • Beadpull Measurements and Tuning • High Power Measurements ADAM SA

  12. Bridge Coupler Design Input Power Input Power ADAM SA

  13. Bridge Coupler for the First Unit ADAM SA Tank 2 Tank 1

  14. Outline • CCL RF design • Tank Design • Bridge Coupler Design • RF Feedthrough Design • Low Power Measurements • Beadpull Measurements and Tuning • High Power Measurements ADAM SA

  15. RF Feedthrough Design • Magnetic pick-up (loop) for high power operation. • The coupling has to belessthan 40dB in order to couple few watts, to reduce at minimum the operating mode frequency shift, to reduce at minimum the losses on the pick-up thatcouldbring at a reduceQ-value ADAM SA 3.50mm 1.52mm L_pk

  16. Different pick-up length 3.50mm 1.52mm ADAM SA L_pk

  17. CCL RF Design – Conclusions • Consistent • Particle Energy & Phase • Design Parameters & Constraints • Complete • Tank and Module Design • Tuners for Stabilization • Power Coupler & Feedthroughs ADAM SA

  18. Outline • CCL RF design • Tank Design • Bridge Coupler Design • RF Feedthrough Design • Low Power Measurements • Beadpull Measurements and Tuning • High Power Measurements ADAM SA

  19. Low Power Measurements - Motivation • Low power measurements have to be performed in order to find the resonance frequency, quality factor, coupling parameter beta of the power coupler, length of the tuners • Tolerances, thermal expansion, possible numerical code frequency deviation, define the maximum frequency error • The tuners in the accelerating and coupling cells will compensate part of these frequency errors • All cells have tuners in order to actlocally. The fielduniformitycouldbeadjusted by local tuning ADAM SA

  20. Low Power Measurements - How • RF pick-ups(antennas, loops) willbeused in order to find the spectrum of each tank, so the operating frequency and the quality • Beadpullmeasurementswillbeperformed in order to check the E fielduniformity ADAM SA

  21. Outline • CCL RF design • Tank Design • Bridge Coupler Design • RF Feedthrough Design • Low Power Measurements • Beadpull Measurements and Tuning • High Power Measurements ADAM SA

  22. High Power Measurements - Motivation • Modules AcceptanceTest • Pre-conditioningprior to acceleratoroperation Goal: stable operationwithrequired input power and reflected power below 10% Locations where power measurementswillbeperformed (Pfw, Prev, Pcav) ADAM SA

  23. Thank you for your attention ADAM SA

  24. Back up ADAM SA

  25. Drawbacks of RelaxedTolerances • Local temperaturerisedifferentfromexpected • Couldbring to an important frequency shift of single cellsthatcouldbecovered (if in the acceptable tuning range) by tuners BUT only if ALL cellswillbemeasuredaftermachining • Field uniformity off fromdesignedvalue • Differentacceleration in eachcell: the particlewillbe out of phase in the nextcell • Frequency shift • Couldbecovered by tuners at the cost of more dissipated power • Extra field in the coupledcells • Low power efficiency i.e. more dissipated power ADAM SA NB. The number of tuners has been limited at 2 per cell in order to preserve the quality factor of the cells and to reducecomplexity

  26. Testing and conditioning procedure • Low power to high power • Short to long pulses • Low to high repetition rate • Limitation of power rise by hardware thresholds (vacuum, powers, water temperature) • Vacuum and reflected power feedback loop to keep the SW interlocks far from the HW interlocks ADAM SA • HW interlocks • modules temperature, input water temperature • vacuum • water flow • forward, reverse, cavity powers • SW interlocks • all the HW interlocks • thresholds are tighter than HW interlocks in order to reduce RF-off time

  27. 5cells - half CC termination – fπ/2 vs tuner length(4mm diameter) ADAM SA

More Related