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MuCool Cavity RF Simulation Studies

MuCool Cavity RF Simulation Studies. Zenghai Li Lixin Ge , Chris Adolphsen , SLAC, Daniel Bowring, Derun Li, Tianhuan Luo , LBNL MAP Collaboration Meeting 06/21/2013. Outline. Multi-physics Modeling tool ACE3P Modeling effort with ACE3P 805 MHz Be-wall modular cavity

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MuCool Cavity RF Simulation Studies

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  1. MuCool CavityRF Simulation Studies Zenghai Li LixinGe, Chris Adolphsen, SLAC, Daniel Bowring, Derun Li, TianhuanLuo, LBNL MAP Collaboration Meeting 06/21/2013

  2. Outline • Multi-physics Modeling tool ACE3P • Modeling effort with ACE3P • 805 MHz Be-wall modular cavity • 201 MHz cavity (Tianhuan’s talk) • Cavity length study • Summary and outlook Z. Li - RF Simulation Studies, MAP 6/21/2013

  3. Accelerator Modeling with EM Code Suite ACE3P SLAC’s suite of conformal, higher-order, C++/MPI based parallel finite-element electromagnetic codes. Implemented on NERSC super computers https://slacportal.slac.stanford.edu/sites/ard_public/bpd/acd/Pages/Default.aspx ACE3P (Advanced Computational Electromagnetics3P) Frequency Domain: Omega3P – Eigensolver (damping) S3P – S-Parameter Time Domain:T3P – Wakefields and Transients Particle Tracking: Track3P – Multipacting and Dark Current EM Particle-in-cell:Pic3P– RF guns & klystrons Multi-physics: TEM3P – EM, Thermal & Structural effects • Have been applied to cavity and rf component design for various accelerator projects • Cavity design and optimization, HOM damping, coupler design,multipacting, thermal and mechanical analysis, etc • As numerical probe to help understand experimental data (e.g. identifying trapped modes, understand bead-pull results, MP barriers, etc) Z. Li - RF Simulation Studies, MAP 6/21/2013

  4. Be-Wall Modular Cavity Modular cavity 104.4 mm in length • Coupler optimization • MP simulation and mitigation - for B=0T and B=3T • Shape optimization • TiN coating • Thermal analysis Z. Li - RF Simulation Studies, MAP 6/21/2013

  5. The Coupler • Side coupling • Reduced height waveguide to reduce transverse size, step transition to full height • Beta=1.35 Z. Li - RF Simulation Studies, MAP 6/21/2013

  6. MP Around Coupler Iris – initial design • Waveguide stub: 36.85mm • Iris neck rounding: 6.25mm simulation using Track3P Resonant particles on iris neck region and end of the waveguide stub B=3T B=0T • Resonant particles only occur around coupler iris region • Strong MP barrier around 7.5 MV/m Z. Li - RF Simulation Studies, MAP 6/21/2013

  7. Coupler Modification to Minimize MP Band (h) 43mm stub, racetrack neck (c) 36.85mm stub, 12mm rounding Z. Li - RF Simulation Studies, MAP 6/21/2013

  8. MP Around Coupler Iris – Prototype Design WG stub:43mm, racetrack iris neck (h) Coating Area (Z-X plot) • B=3T • B=0T cavity outer wall coupler neck Z. Li - RF Simulation Studies, MAP 6/21/2013

  9. Field Enhancement at Viewport • Frequency shift due to viewport: 23kHz/port • B field at viewport: 0.78*B_coupling_slot Z. Li - RF Simulation Studies, MAP 6/21/2013

  10. MP at Viewport, TiN Coating Area B=3T MP, need coating (coating area) B=0T Z. Li - RF Simulation Studies, MAP 6/21/2013

  11. MP on Be Wall, B=3T • Two point MP resonant particles on Be window • Impact energies much higher than energy of peak SEY (~ 250eV) • Not likely to MP (though high energy field emission current possible) F. Le Pimpec, et al, SLAC-TN-04-046 \ LCC-0146 Z. Li - RF Simulation Studies, MAP 6/21/2013

  12. Fields at Pump Slot E field B field No significant enhancement at the slots Z. Li - RF Simulation Studies, MAP 6/21/2013

  13. Field in waveguide • Single step transition from reduced height waveguide to full height waveguide • Field is ~3.6 times the field in full height waveguide Z. Li - RF Simulation Studies, MAP 6/21/2013

  14. Thermal Mechanical Modeling Using TEM3P • Using same data structure as EM components of ACE3P • RF heat load calculation using higher-order EM fields from Omega3P/S3P/T3P • Higher-order thermal and mechanical solvers • Realistic linear and nonlinear material properties • Calculate geometry distortion and effect on RF Z. Li - RF Simulation Studies, MAP 6/21/2013

  15. Modular Cavity Material Composition Stainless steel with copper coating inside Stainless Steel Copper ring Beryllium wall Courtesy David Martin Z. Li - RF Simulation Studies, MAP 6/21/2013

  16. RF Thermo-Elastic Simulation Results Cooling channel added to minimize ΔT across the Be endplate B Fields Z. Li - RF Simulation Studies, MAP 6/21/2013

  17. 201 MHz cavity MP Analysis See Tianhuan’s talk for details Cavity Model Curved window Coupler region Z. Li - RF Simulation Studies, MAP 6/21/2013

  18. 201 MHz Cavity MP Comparison – with vs without external B field See Tianhuan’s talk for details NO external B field With 3T external B field NO resonant particles on Window Z. Li - RF Simulation Studies, MAP 6/21/2013

  19. Dark Current Effect vs Cavity Length • Using a simple pillbox cavity model under strong B field • Calculate • Impact Energy: V • FN current: J • “Impact power” : V*J v.s. cavity length, Es and effective gradient Eacc • --> To understand parameter optimization for cavities under strong magnetic field Z. Li - RF Simulation Studies, MAP 6/21/2013

  20. Dark Current - Impact Energy & V*J (beta_FN=50) Es=25MV/m max at L=81mm • At same Es • Max V*J at around 80mm length • V*J drops by more than factor of 2 at a length of lambda*/2 • But, higher V*J with longer length for the same effective accelerating gradient (next slide) Z. Li - RF Simulation Studies, MAP 6/21/2013

  21. V*J at Same Effective Acc Gradient • Effective Gradient: 25MV/m • Longer cell require higher ES to achieve same acceleration gradient – higher V*J • Optimal RF power requirement at L~100 mm (5mm space between cavities assumed for packing factor) ES/Gaccvs cavity length (due to Ttransient) PACC/L Testing cavities of different lengths will help understanding the effects of DC, and parameters for cavity optimization Z. Li - RF Simulation Studies, MAP 6/21/2013

  22. Summary and Outlook ACE3Pis a suite of high performance computing EM thermal/mechanical codes Modular cavity prototype design • Coupler geometry optimized • MP analyzed, mitigation of MP at coupling iris and viewport incorporated in the engineering design • Thermal stress analyzed using TEM3P, cooling channels incorporated in the thermal design to reduce stress on Be wall • Cavity being manufactured 201 MHz cavity simulation • MP analysis with realistic external B field map (Tianhuan, Lixin) Outlook – simulation effort with ACE3P • Assist users on using ACE3P • Support rf design and optimization of cavity and components • Modular cavity and test setups • Dark current and RF breakdown studies Z. Li - RF Simulation Studies, MAP 6/21/2013

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