Method of longitudinal impedance measurement for accelerator elements in wide frequency region using double Fourier transform

The double Fourier transform method is discussed, which allows measurement of the impedance of a distributed continuity for both low and high frequencies. The main causes of errors are considered and the results of measurements are given. It is possible to observe besides the main transmitted pulse many reflected pulses caused by mismatches at matching sections consisting of adapters, cable junctions and other elements which are needed for the measurement set-up. For removing these reflections, the time filtering and space separation of the reflected pulses are used. Two additional metal segments of a waveguide must be embedded in a scheme of measurements; they are located at both sides of a measured element and permit elimination of reflected pulses from the main pulse in some time interval tau . The results show that at a correctly chosen tau longitudinal impedance of a distributed discontinuity may be estimated with good accuracy in the full frequency region of interest without spacers.<
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