Optimized design of triple-spoke superconducting resonator for application in high-power accelerators

Peter N. Ostroumov, Physics Division, Argonne National Laboratory

Kwang-Je Kim, University of Chicago

Mark Champion, Fermilab

ANL-FNAL Collaboration Meeting, June 27, 2008

Triple-spoke superconducting resonator June 27, 2008 2

Triple Spoke Resonators (TSR)

Proposed by K. Shepard (ANL) in 2002 First publication to show all benefits of TSRs:

– High-Energy Ion Linacs Based on Superconducting Spoke Cavities, K. W. Shepard, P. N. Ostroumov, and J. R. Delayen, Phys. Rev. ST – AB 6, 080101 (2003).

Two types of TSRs (beta=0.5 and beta=0.62) were developed and tested for FRIB (Facility for Rare Isotope Beams)

In the velocity range from 0.4c to 0.7c TSRs provide:– High Q and high accelerating gradients (demonstrated at ANL)

– Excellent mechanical stability, minimizing the difficulty of tuning and phase control in the presence of microphonics or/and dynamic Lorentz detuning. Requires optimized design.

– High shunt impedance – reduced cryogenic load

– Low frequency – large longitudinal acceptance, reduced sensitivity to phase errors in the cavity resonance control

– Low shunt impedance of HOM: very attractive for high-current FEL (beta=1)

– Being considered for application in variety of projects worldwide

Triple-spoke superconducting resonator June 27, 2008

Project X Linac structure

325 MHz 1300 MHz

Major Linac Sections

Front end ILC, beta=0.81 Standard ILC

0.065 2.5 10 33 110 4100.065 2.5 10 33 110 4100.05 2.5 10 32 123 420

Will be installed in the Meson Lab (60 MeV)

SSR-2

Triple-spoke superconducting resonator June 27, 2008

ANL TSR performance 345 MHz

CW operation Residual resistance is ~5 n (2K),

Accelerating field is10 MV/m Mechanical design is optimized

to reduce

Very low microphonics (=1.04 Hz)

Not optimized to reduce Lorentz detuning ~7.3 Hz/(MV/m)2

Fast tuners (piezoelectric and magnetostrictive) were demonstrated

p

f

Triple-spoke superconducting resonator June 27, 2008

FNAL 325 MHz TSR, optimized to reduce surface fields

Electrodynamics optimization by Ivan Gonin (FNAL)

A

1

A2

B1

B2

Triple-spoke superconducting resonator June 27, 2008

Proposed tasks

Optimize mechanical design of the 325 MHz pulsed TSR – include helium vessel, coupling ports

– Minimize Lorentz detuning

– Locate best place for the slow and fast tuners

Improve electrodynamics design – Keep surface fields at minimum for given accelerating gradient

Iterate mechanical and electrodynamics design Develop mechanical design of the resonator (the second

year) for pulsed operation and application in Project X Incorporate into the resonator design:

– Slow tuner

– Fast tuner

– High-power coupler

Triple-spoke superconducting resonator June 27, 2008

Preliminary studies of the new TSR design using ANSYS

Thermal contraction (300K 2K) Helium pressure

Helium vessel

Deformations in the1/8th of the model, symmetries applied

Triple-spoke superconducting resonator June 27, 2008

To achieve the proposed tasks

Build collaboration in the specific area of triple-spoke resonators and engage collaborators at UChicago, Fermilab and Argonne

Use broad ANL experience in development, construction and test of TSRs

Engage ANL Nuclear Engineering Division for thermal, structural analysis and mechanical design of the TSR

Use FNAL experience in design, construction and test of a single-spoke resonator for HINS

Enhance accelerator physics R&D in UoC Involve students and post-doc for the optimized design of

triple spoke resonators