| Paper |
Title |
Page |
| THP004 |
Digital Low-Level RF Control Using Non-IQ Sampling
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568 |
| |
- L. R. Doolittle
LBNL, Berkeley, California
- M. S. Champion, H. Ma
ORNL, Oak Ridge, Tennessee
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The success of digital feedback with synchronous IQ sampling for cavity field control in recent accelerator projects make this LLRF control scheme a popular choice. This short-period synchronous sampling does not, however, average out well-known defects in modern ADC and DAC hardware. That limits the achievable control precision for digital IQ LLRF controllers, while demands for precision are increasing for future accelerators such as International Linear Collider. For this reason, a collaborative effort is developing a digital LLRF control evaluation platform to experiment using coherent sampling with much longer synchronous periods, on the order of the cavity closed-loop bandwidth. This exercise will develop and test the hardware and software needed to meet greater future RF control challenges.
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| THP005 |
Digital Control of Cavity Fields in the Spallation Neutron Source Superconducting Linac
|
571 |
| |
- 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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