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| WEPTY008 | Superconducting Harmonic Cavity for the Advanced Photon Source Upgrade | 3267 |
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| A new bunch lengthening cryomodule using a single-cell ‘higher-harmonic’ superconducting cavity (HHC) based on the TESLA shape and operating at the 4th harmonic (1408 MHz) of the main RF is under development at Argonne. The system will be used to improve the Touschek lifetime and increase the single-bunch current limit in the upgraded multibend achromat lattice of the Advanced Photon Source electron storage ring. The 4 K cryomodule will fit within one half of a straight section, ~2.5 meters, of the ring. The system will use a pair of moveable 20 kW (each) CW RF power couplers to adjust the loaded Q and extract power from the beam. This will provide the flexibility to adjust the impedance presented to the beam and run at various beam currents. Higher-order modes (HOMs) induced by the circulating electron beam will be extracted along the beam axis and damped using a pair of room temperature beam line absorbers. Engineering designs and the prototyping status for the cavity, power couplers and HOM absorbers are discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY008 | |
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| WEPTY009 | Preservation of Quality Factor of Half Wave Resonator during Quenching in the Presence of Solenoid Field | 3270 |
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Funding: This work was supported by the U.S. Department of energy, Offices of High-Energy Physics and Nuclear Physics, under Contract No. DE-AC02-76-CH03000 and DE-AC02-06CH11357. The Proton Improvement Plan II at FNAL relies upon a 162.5 MHz superconducting half-wave resonator cryomodule to accelerate H− beams from 2.1 to 10 MeV. This cryomodule contains 8 resonators with 8 superconducting solenoid magnets interspersed between them. X-Y steering coils are integrated with a package of the superconducting solenoid magnets. The center of the solenoids is located within ~50 cm of the high surface magnetic field of the half-wave resonators and in this study we assess whether or not magnetic flux generated by this magnet is trapped into the half-wave resonators niobium surface and increases the RF losses to liquid helium. To test this we assembled a solenoid with a 162.5 MHz half-wave resonator spaced as they will be in the cryomodule. We measured the quality factor of the cavity before and after the cavity quenched as a function of field level in the coils. No measurable change in the quality factor was observed. In this paper, we will present details of the measurements and discuss the magnetic field map. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY009 | |
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| WEPTY010 | Electropolishing for Low-Beta and Quasi-Waveguide SRF Cavities | 3273 |
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| Argonne National Laboratory (ANL) has extended high quality electropolishing techniques based on those developed for the International Linear Collider to several more complex superconducting RF cavities. These include the co-axial TEM-mode quarter-wave and half-wave cavities as well as a 2.8 GHz quasi-waveguide structure intended for beam bunch rotation. This system is an improved version of the one developed for 1.3 GHz 9-cell cavities and includes easy provision for direct water cooling using the helium jacket. The performance of these SRF cavities both in terms of RF fields and losses equals or exceeds that of most 9-cell elliptical cavities built and tested today. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY010 | |
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