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9MHz LeRHIC Cavity Design

9MHz LeRHIC Cavity Design. Salvatore Polizzo RF Design Engineer May 16, 2014. Topic Outline. LeRHIC Program Summary Review Conceptual Cavity Designs Outline Current Cavity Design Present EM Simulation Methods & Results. Low Energy RHIC Program Summary.

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9MHz LeRHIC Cavity Design

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  1. 9MHz LeRHIC Cavity Design Salvatore Polizzo RF Design Engineer May 16, 2014

  2. Topic Outline • LeRHIC Program Summary • Review Conceptual Cavity Designs • Outline Current Cavity Design • Present EM Simulation Methods & Results

  3. Low Energy RHIC Program Summary We are in search of the “critical point” where matter violently transitions back from a Quark-Gluon Plasma to a Hadron Gas. QCD phase diagram for nuclear matter.

  4. Low Energy RHIC Program Summary We are in search of the “critical point” where matter violently transitions back from a Quark-Gluon Plasma to a Hadron Gas. A new low frequency RF system is required to reduce the space charge limitations that prohibit strong electron cooling. QCD phase diagram for nuclear matter.

  5. Cavity Conceptual Design History • Dielectric Loaded Folded Cavity • 4.5MHz cavity length = 2m • Combines gap and cavity foreshortening functions • High Q when compared to ferrite cavities (Wesgo AL-995 tan(δ) = 3e-5) Air Vacuum

  6. Cavity Conceptual Design History • Dielectric Loaded Folded Cavity • Vp = 40kV (80kV Total) • fo = 4.5MHz • Qo ≈ 3000 Air Vacuum

  7. Cavity Conceptual Design History • Dielectric Loaded Folded Cavity • Vp = 40kV (80kV Total) • fo = 4.5MHz (L Increases 25% with 9MHz) • Qo ≈ 3000 Want More Luminosity! Air Vacuum

  8. Cavity Conceptual Design History • 9 MHz Alumina Loaded Gap Cavity (Need 160kV Total) • Vp = 53.4kV • fo = 9MHz • Qo ≈ 6000+ (Wesgo AL-995 tan(δ) = 3e-5) Air Vacuum

  9. Cavity Conceptual Design History • 9 MHz Alumina Loaded Gap Cavity (Need 160kV Total) • Vp = 53.4kV • fo = 9MHz (Difficult to fabricate) • Qo ≈ 6000+ (Wesgo AL-995 tan(δ) = 3e-5) Lacking The Warm Fuzzy! Air Vacuum

  10. Cap Gap Cavity RF Design Concept • fo = 9MHz • Qsim = 8400 • Gap C = 350pF • R/Q = 50Ω Air Air Vacuum

  11. Cap Gap Cavity RF Design Concept • fo = 9MHz • Qsim = 8400 • Gap C = 350pF • R/Q = 50Ω • Drive Power ≈ 8kW • Vp = 80kV+ (160kV Total) • Irms(80kV) ≈ 1200A Air Air Vacuum

  12. Cap Gap Cavity RF Design Concept • fo = 9MHz • Qsim = 8400 • Gap C = 350pF • R/Q = 50Ω • Drive Power ≈ 8kW • Vp = 80kV+ (160kV Total) • Irms(80kV) ≈ 1200A • Length = 2m • Cavity Radius = .45m • Center Conductor Radius = 8cm • Beam Pipe Inner Radius = 5cm Air Air Vacuum

  13. Final RF System Design Requirements Au Storage SC Dipole SC Dipole 3 Cavities 3 Cavities Stochastic Cooling

  14. Current Cavity RF Model • Drive Power ≈ 8kW • Vp* = 60kV+ • Irms(60kV) ≈ 900A • fo = 8.7 – 9.4MHz • Qsim = 8400 • Gap C = 360pF • R/Q = 50Ω • Length = 2.5m • Cavity Radius = .45m • Center Conductor Radius = 8cm • Beam Pipe Inner Radius = 5cm The resulting capacitor gap assembly is the product of an ongoing collaboration between BNL and Comet Technologies * Additional RF conditioning will be required to reach 80kV

  15. Gap Cap Features & Benefits • Monetary Savings • Combines capacitive foreshortening and beam gap

  16. Gap Cap Features & Benefits • Monetary Savings • Combines capacitive foreshortening and beam gap • No vacuum required in the cavity body • Eliminates Cavity Vacuum Seals • Inherently reduces Multipactoring

  17. Gap Cap Features & Benefits • Monetary Savings • Combines capacitive foreshortening and beam gap • No vacuum required in the cavity body • Eliminates Cavity Vacuum Seals • Inherently reduces Multipactoring • Isolated gap and capacitor vacuum • Loss of Ring Vacuum ≠ Capacitor Failure

  18. Gap Cap Features & Benefits • Monetary Savings • Combines capacitive foreshortening and beam gap • No vacuum required in the cavity body • Eliminates Cavity Vacuum Seals • Inherently reduces Multipactoring • Isolated gap and capacitor vacuum • Loss of Ring Vacuum ≠ Capacitor Failure • Highly Configurable • The cavity frequency can be easily be changed by swapping the gap cap

  19. Gap Cap Specification - - - - 80kV Operation ------- 60kV Operation

  20. Frequency Domain Simulation E Field along beam line (.5W Input Power) ʃEdz ≈ 600V ∴ Voltage Scale Factor ≈ 134 Vp = 80kV V/m m

  21. Frequency Domain Simulation H Field around beam line (.5W Input Power) L ≈ .54m ʃHdϕ ≈ 9Arms Irms ≈ 1200A A/m

  22. Frequency Domain Simulation Input Impedance Input Coupling Loop 1.4M Tetrahedral Mesh Cells (Memory Intensive) * Defined 5 different local mesh groups

  23. Fundamental Mode Field Distribution E Field Peak Field Air ≈ 2.5MV/m Peak Field Vacuum Gap ≈ 3.4MV/m H Field Peak Field ≈ 3250A/m

  24. Distribution of Power Dissipation Power Dissipated ≈ 8.3kW 1.4kW 22W 200W 250W 1.3kW 5kW 350W

  25. Conclusion • Good progress has been made on Gap Cap design. • Currently finalizing design • Future work • Complete Cavity Mechanical Design • Tuner Design (Complete band or bimodal?) • Fundamental Mode Coupling Loop

  26. Acknowledgments BNL – A. Zaltsman, J.M. Brennan, M. Blaskiewicz, I. Ben-Zvi, S. Verdu Andres, A. Fedotev, J. Woods, J. Fite, J. Brodowski, J. Tuozzolo, RF Group Comet – M. Bonner, T. Weber, W. Bigler, M. Abrecht, W. Brunhart, M. Mildner

  27. Thank You!

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