| Paper | Title | Page |
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| TUP76 | Adaptive Feedforward Cancellation of Sinusoidal Disturbances in Superconducting RF Cavities | 447 |
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| A control method, known as adaptive feedforward cancellation (AFC) is applied to damp sinusoidal disturbances due to microphonics in superconducting RF (SRF) cavities. AFC provides a method for damping internal, and external sinusoidal disturbances with known frequencies. It is preferred over other schemes because it uses rudimentary information about the frequency response at the disturbance frequencies, without the necessity of knowing an analytic model (transfer function) of the system. It estimates the magnitude and phase of the sinusoidal disturbance inputs and generates a control signal to cancel their effect. AFC, along with a frequency estimation process, is shown to be very successful in the cancellation of sinusoidal signals from different sources. The results of this research may significantly reduce the power requirements and increase the stability for lightly loaded continuous-wave SRF systems. | ||
| THP66 | Measurement and Control of Microphonics in High Loaded-Q Superconducting RF Cavities | 763 |
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Superconducting radio frequency (SRF) linacs with light beam loading, such as the CEBAF upgrade, RIA and energy recovery linacs, operate more efficiently with loaded-Q values >1·107. The narrow band-width puts stringent limits on acceptable levels of vibration, also called microphonics, that detune the SRF cavities. Typical sources of vibration are rotating machinery, fluid fluctuations and ground motion. A prototype RIA 805 MHz v/c=0.47 cryomodule is presently under test in realistic operating conditions [1]. Real-time frequency detuning measurements were made for modulation rates from DC to 1 kHz. At 2 K the maximum frequency deviation was less than 100 Hz peak-to-peak, and was consistent with high loaded-Q operation. The measured modulation spectrum was primarily made up of discrete Fourier components with modulation frequencies less than 80 Hz. Using an accelerometer and helium pressure transducer, the primary sources of vibration were determined to be the high power cryoplant motors and 2 K helium fluctuations. Adaptive feedforward was used to decrease the magnitude of individual Fourier components by four to ten times [2]. Details of the experimental setup and measurements will be presented.
[1] “Experimental Study of an 805 MHz Cryomodule for the Rare Isotope Accelerator”, T.L. Grimm et al., THP70, these proceedings. [2] “Adaptive Feedforward Cancellation (AFC) of Sinusoidal Disturbances in SRF Cavities”, H. Khalil et al., TUP76, these proceedings. |
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