[Triumf-seminars] TRIUMF Accelerator Seminar today at 14:00

[TRIUMF Seminars]

Date/Time: Wed 2014-07-16 at 14:00

Location:  ISAC II Conf Rm     

Speaker:   Ramona Leewe (TRIUMF)

Title:     Control of RF Cavity Resonance Frequency using Reflected Power Measurements

Abstract: Control of the natural resonance frequency of an RF cavity is essential for acceleration structures due to their high cavity sensitivity to internal and external vibrations. The quality of an accelerated beam is directly dependent on the stability of the amplitude and the phase of the acceleration field developed in these cavities. Various methods can be used to regulate the tune of the cavity. To date, however, all operational cavity tuning methods have involved measuring the input and the output phase of the cavity, then using this information to adjust the resonance frequency by changing the geometry of the cavity. The major drawback of this technique is given by the phase measurement which can be inexact due to drifts caused by thermal effects on amplifier and cables which leads to periodic manual adjustments. To eliminate the phase measurement a new control approach based on reflected power measurements will be presented. Reflected power measurements are robust with respect to external influences and can lead to a more accurate control system without manual adjustment.  A difference in cavity operation for normal and superconducting cavities is given by under or over coupling for the superconducting cavities yielding to a different reflected power function. The presented system was developed with respect to normal conducting cavities. The control approach is based on a relatively new and modified extremum seeking sliding mode algorithm. A short Lyapunov analysis proves the stability of the closed loop system. First simulation results regarding the performance of the system will be shown. An outlook regarding future plans will show how the system can physically be realized.



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