CLASSE: SRF

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CORNELL LABORATORY FOR ACCELERATOR-BASED SCIENCES AND EDUCATION

Ferrite HOM load for B-cell cavity

HOM load photo

"porcupine" load

The beam tubes of the CESR B-cell cavity have been designed so that all of the higher-order modes (HOMs) propagate out of the cavity. To damp these modes to Q factor values of ~100, it was proposed to use ferrite HOM loads that are an integral part of the beam tube and are located outside the cryostat [1, 2]. A so-called "porcupine" load has a modular design [3, 4]. It consists of a stainless steel shell with 18 Elkonite plates bolted along the inside. The absorbing medium is ferrite tiles which are bonded to the plates. Copper tubing is brazed to each plate to provide water cooling. Ferrite can absorb power density up to 25 W/cm2, at which point the ferrite crackes. This corresponds to a total absorbed HOM power of 18 kW per load.

test setup

Test setup

The modular design of the load allows to individually test each Elkonite plate with ferrite tiles prior to assembly. The test set-up consists of 1 kW S-band power source connected to a rectangular waveguide. The Elkonite plate is attached to the waveguide and ferrite temperature is monitored with an ifra-red camera.

Ferrite temperature

Ferrite temperature

References

  1. D. Moffat, et al. Design and Fabrication of a Ferrite-lined HOM Load for CESR-B. In Proceedings of the 1993 Particle Accelerator Conference,, 977-979.
  2. W. Hartung, et al. The Interaction of a Beam WIth a Beam Line Higher-Order-Mode Absorber. In Proceedings of the 1993 Particle Accelerator Conference, 5 , 3450-3452.
  3. S. Belomestnykh, et al. Comparison of the Predicted and Measured Loss Factor of the Superconducting Cavity Assembly for the CESR Upgrade. In Proceedings of the 1995 Particle Accelerator Conference, 5 , 3394-3396.
  4. E. Cojnacki, et al. Beamline RF Load Development at Cornell. In Proceedings of the 1999 Particle Accelerator Conference, in print.