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

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68 5. RADIOFREQUENCY MEASUREMENT Rings Machining No No Coupled Cells Measurement Bead Pulling Measurement Discard k1, k2, f Tiles Are the values correct? Single Cavity Measurement Yes Stacked Cells Measurement Whole Module Brazing Bridge Coupler Cavities Coupled Cells Measurement Are the values in the range of tuners? Tank Brazing BC Brazing Discard Are the values in the range of tuners? Frequencies Measurement Yes Rod Tuners (final) Brazing f Yes Yes Rod Tuners Regulation Bead Pulling Measurement Are the values correct? Frequencies Measurement k1, k2, f Figure 5.1. The flux diagram of the measurement <strong>and</strong> machining procedure. work on the rings in the half cavities to change the frequency <strong>and</strong> on the slot dimensions to change the coupling. Then, the tiles are brazed together to make a tank. On this structure frequency <strong>and</strong> bead pulling measurement are done; first measurement changing the lateral rod tuners positions can be made as well, in order to control that the No No
2. RF MEASUREMENT ON A SINGLE CAVITY 69 design parameters are reachable. This step is repeated for all the tanks in the same way. On the other h<strong>and</strong>, the bridge coupler pieces are stacked to make coupled cells measurement <strong>and</strong> to control that the design values are in the movable tuner range. Once these steps are finished, the whole module brazing is made, <strong>and</strong> after, one deals with a structure where it is still possible to move the rod tuners in the cavities <strong>and</strong> the tuners in the three bridge couplers. Last, the hard point has to be fixed: after regulations on all those tuners, one control the π/2 mode, by means of a frequency measurement, <strong>and</strong> the axial electric field by means of a bead pulling measurement. The procedure go ahead with the help of the empirical criteria found with the equivalent model <strong>and</strong> with lots of patience <strong>and</strong> skill operators. At the same time, one has to control the coupling between the waveguide <strong>and</strong> the whole module <strong>and</strong> has to choose the length of the short-circuited waveguide (see figure 3.11). Finally, after the parameters are fixed within the design ranges, the rod tuners are also brazed <strong>and</strong> the module is ready for the power tests. 2. RF Measurement on a single cavity As it is shown in the previous chapters, a resonant mode of an electromagnetic cavity can be fully represented by only three parameters: resonant frequency, quality factor <strong>and</strong> shunt impedance. By using a network analyzer <strong>and</strong> some mechanical <strong>and</strong> electrical tools, it is possible to measure all these three parameters. In principle, these measurements are very easy, but a big effort has to be made in order to get correct results <strong>and</strong> to avoid systematic errors when one measures the cavities of a structure such a LIBO. 2.1. Measurement of the resonant frequency. The measurement of resonant frequency on a closed cavity (excepted for the beam holes) is performed using probes which penetrate until the inner surface of the cavity. One probe allows the measurement of reflection coefficient, whereas two probes allow measurement of transmission coefficient. It is apparent that the cavity should has one or two holes for the probes, unless the beam holes are used. The probes are realized in the following two ways: • electric pick-up which is a rigid coaxial cable, whose internal conductor juts out of about 4 mm over the external one. This type of antenna should be used where the electric field is strong 1 . In figure 5.2 an example of realization is shown. • magnetic loop which is a rigid coaxial cable, whose internal conductor juts out over the external one <strong>and</strong> realizes a loop 1 It could be put along the axis of the cavity through the beam hole where the longitudinal electric field should be strong.
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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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8 2. LINAC AND SCL ACCELERATORS par
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10 2. LINAC AND SCL ACCELERATORS wh
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12 2. LINAC AND SCL ACCELERATORS at
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14 2. LINAC AND SCL ACCELERATORS 2.
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16 2. LINAC AND SCL ACCELERATORS f
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Page 29 and 30: CHAPTER 3 Design T
Page 31 and 32: 1. GLOBAL PARAMETERS OF THE ACCELER
Page 33 and 34: 2. ANALYSIS OF COUPLED CAVITIES 27
Page 35 and 36: 3. SINGLE CAVITY DESIGN 29 Spice ha
Page 37 and 38: 20mA 15mA 10mA 5mA 3. SINGLE CAVITY
Page 39 and 40: 3. SINGLE CAVITY DESIGN 33 • HFSS
Page 41 and 42: 4. BRIDGE COUPLERS DESIGN 35 4. Bri
Page 43 and 44: 5. COUPLING BETWEEN WAVEGUIDE AND B
Page 49: 5. COUPLING BETWEEN WAVEGUIDE AND B
Page 52 and 53: 46 4. CIRCUIT MODEL where the matri
Page 54 and 55: 48 4. CIRCUIT MODEL For the latest
Page 56 and 57: 50 4. CIRCUIT MODEL left side of th
Page 58 and 59: 52 4. CIRCUIT MODEL and</st
Page 60 and 61: 54 4. CIRCUIT MODEL Under this hypo
Page 62 and 63: 56 4. CIRCUIT MODEL matrix of the w
Page 64 and 65: 58 4. CIRCUIT MODEL For the derivat
Page 66 and 67: 60 4. CIRCUIT MODEL Remembering the
Page 68 and 69: 62 4. CIRCUIT MODEL the bars is pro
Page 70 and 71: 64 4. CIRCUIT MODEL is unitary, one
Page 72 and 73: 66 4. CIRCUIT MODEL 120 100 80 60 4
Page 76 and 77: 70 5. RADIOFREQUENCY MEASUREMENT Fi
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Page 105 and 106: Conclusions and Ou
Page 107: CONCLUSIONS AND OUTLOOK 101 Finally
Page 110 and 111: 104 BIBLIOGRAPHY [23] U. Amaldi, B.
Page 112 and 113: 106 LIST OF FIGURES 2.12 Drawing of
Page 114 and 115: 108 LIST OF FIGURES methods, in add
Page 116: 110 ACKNOWLEDGEMENTS Naples, Italy
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