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Introduction Modal Analysis: Elliptical Cavity
Technical Division *under Contract No. DE-AC02-07CH11359
Project X
Project X is a proposed proton accelerator complex at Fermilab The CW low current operation of the Project X requires superconducting cavities to operate at a high loaded Q Therefore it requires mechanical design optimization of cavities to minimize the sensitivity to microphonics We present our experience in using COMSOL Multiphysics for evaluation of sensitivity of operatingfrequency shift due to both fluctuations in the helium pressure (df/dP) and mechanical resonances
Conclusion and References
M. Awida, I. Gonin, T. Khabiboulline, Y. Pischalnikov, W. Schappert, and V. Yakovlev Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL, 60510, USA
Optimization of Mechanical Properties of Superconducting Cavities for Project X LINAC
Fermilab
Microphonics: Spoke Cavity
EM
• Eigen frequency simulation to findthe resonant frequency (f0)
Solid
Mech
• Find the deformation under givenpressure load (PL)
Moving Mesh
• Update the mesh after deformation
EM
• Eigen frequency simulation to findthe resonant frequency afterdeformation (fp)
Study1
• Eigen-frequency (tofind f0)
Study2
• Stationary (solvingonly for solidmechanics andmoving mesh)
• Eigen-frequency (tofind fp)
Electromagnetic Waves
• Solving only for the RFdomain
• Applying the proberboundary conditions
Solid Mechanics
• Solving only for the CavityVessel
• Applying the proper fixedconstraints, symmetries,displacements, andboundary load
Moving Mesh
• Solving for all domains
• Applying the properprescribed and free meshdeformation/displacement
Two Simulation Studies
Three Multiphysic
Modules
Niobium Shell
RF Domain
Stainless Steel Vessel
PMC
PEC
Fixed Constraint
Symmetry Boundaries
Pressure Boundary
Load
EM
• Eigen frequency simulation to find theresonant frequency (f0)
Solid
Mech
• Solid Model analysis in “mechanical”domain
Moving Mesh
• Update the mesh after deformation
EM
• Eigen frequency simulation to find theresonant frequency after deformation (fp)
Frequency shifts due helium pressure fluctuations is a major issue in superconducting RF cavities Here is an example for how df/dP is calulcated using COMSOL for a spoke cavity
Prescribed Displacement
u,v,w
Multiphysics analysis is essentially needed to model components for particle accelerators Frequency shifts due to pressure fluctuation needs to be carefully modeled in SRF cavities COMSOL as a multiphysics tool helped us a lot inthat perspective
References: 1. S. D. Holmes,”Project X functional requirementsspecification”, IPAC’12, New Orleans, THPPP090
𝒅𝒇
𝒅𝒑=𝒇𝒑−𝒇
𝟎
𝑷𝑳
Mechanical resonances are another concern for SRF cavities Here is an example for how we used COMSOLto resolve this issue for an elliptical cavity
df/dP [Hz/Torr]