| Paper |
Title |
Page |
| TUP032 |
Comparison of SNS Superconducting Cavity Calibration Methods
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315 |
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- Y. Zhang, I. E. Campisi, P. Chu, J. Galambos, S. Henderson, D.-O. Jeon, K.-U. Kasemir, A. P. Shishlo
ORNL, Oak Ridge, Tennessee
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Three different methods have been used to calibrate the SNS superconducting cavity RF field amplitude. Two are beam based and the other strictly RF based. One beam based method uses time-of-flight signature matching (phase scan method), and the other uses the beam-cavity interaction itself (drifting beam method). Both of these methods can be used to precisely calibrate the pickup probe of a SC cavity and determine the synchronous phase. The initial comparisons of the beam based techniques at SNS did not achieve the desired precision of 1% due to the influence of calibration errors, noise and coherent interfaces in the system. To date the beam-based SC cavity pickup probe calibrations agree within approximately 4%, comparable to the conventional RF calibrations.
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| THP005 |
Digital Control of Cavity Fields in the Spallation Neutron Source Superconducting Linac
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571 |
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- H. Ma, M. S. Champion, M. T. Crofford, K.-U. Kasemir, M. F. Piller
ORNL, Oak Ridge, Tennessee
- A. Brandt
DESY, Hamburg
- L. R. Doolittle, A. Ratti
LBNL, Berkeley, California
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Control of the pulsed RF cavity fields in the Spallation Neutron Source (SNS) superconducting Linac uses both the real-time feedback regulation and the pulse-to-pulse adaptive feed-forward compensation. This control combination is required to deal with the typical issues associated with superconducting cavities, such as the Lorentz force detuning, mechanical resonance modes, and cavity filling. The all-digital implementation of this system provides the capabilities and flexibility necessary for achieving the required performance, and to accommodate the needs of various control schemes. The low-latency design of the digital hardware has successfully produced a wide control bandwidth, and the developed adaptive feed forward algorithms have proved to be essential for the controlled cavity filling, the suppression of the cavity mechanical resonances, and the beam loading compensation. As of this time, all 96 LLRF systems throughout the Linac have been commissioned and are in operation.
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