Theory, Design and Tests on a Prototype Module of a Compact ...

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66 4. CIRCUIT MODEL 120 100 80 60 40 20 0 (Vci − 0.999) · 10 5 87 0 88 0 87 0 85 1 2 3 4 5 6 7 # cell Figure 4.6. The relative level of field in the cavities for the best disposition of the cavities, N = 8, δω0/ω0 = 0.001, K = 0.04 <strong>and</strong> σrms = 4.54 · 10 −10 . The computed values are normalized to the unity, but are shown using the formula (Vci − 0.999) · 10 5 for a better visualization. they are affect by a measurement error. Therefore, the procedure of optimization is effective when the measurement error is proportionally smaller than the measured values.
CHAPTER 5 Radiofrequency Measurement In this chapter a detailed description of the radiofrequency (RF) measurement performed on LIBO prototypes is presented. RF measurement are very important on this type of structures, since they are the only way to correct the unavoidable errors that are mirrors of the mechanical machining tolerances. Note that the errors we have dealings with can big enough to need a correction to get the desired design value for the main electromagnetic parameters, even if they are very small (for example, the frequency error of each cavity is typically included within the 0.1%). In the following, each section begins with an overview on the technique, the instruments <strong>and</strong> the tools used for the specific measurement explained: single cavity <strong>and</strong> coupled cavities measurement are presented, <strong>and</strong> for each type of measurement, specific tasks for LIBO are illustrated. The tuning procedure to obtain a flat longitudinal electric field for the whole LIBO module is also presented. 1. Introduction In the analysis of structures where the geometrical dimensions are comparable with the wavelength of the electromagnetic signals, it is correct to use the concept of reflected <strong>and</strong> transmitted waves rather then currents <strong>and</strong> voltages, since propagation effects become very important. In this frame, the parameters of interest are the scattering parameters, namely the reflection <strong>and</strong> the transmission coefficients [33]. The sequence of RF measurement to perform is quite the opposite of the one used for the design. Indeed, the tiles with two half cavities are normally the first pieces built <strong>and</strong> then the first measurement is on the single cavities. In figure 5.1 it is shown a flux diagram of the procedures adopted with LIBO to build up the module, involving both measurement <strong>and</strong> machining on the copper pieces. First, as we said, one starts from the measurement on the tiles, as they come out from the mechanical workshop. On these pieces three types of measurement are performed: coupled cells measurement giving coupling coefficients <strong>and</strong> resonant frequencies, single frequency measurement <strong>and</strong> stacked cell measurement that gives the π/2 mode frequency <strong>and</strong> the stop-b<strong>and</strong> amplitude. If the values are not correct <strong>and</strong>/or present a large dispersion around the design values, one can 67
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UNIVERSITÀ DEGLI STUDI DI NAPOLI F
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ii CONTENTS List of Figures 105 Ack
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iv INTRODUCTION In the state of art
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2 1. INTRODUCTION TO THE HADRONTHER
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Page 110 and 111: 104 BIBLIOGRAPHY [23] U. Amaldi, B.
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