Beam Signal Detection&Transmission Technology Research For Button-type Pickup

As one of the beam diagnostic component, button-type pickup is the keyequipment to the commissioning and machine study of an accelerator. Signaldetection technologies such as the geometric size, signal-noise ratio andbeam impedance of the electrode have been focused on while the transmissiontechnologies of the beam signal such as the structure of the feedthroughhave not been paid fully attention to. This thesis is trying to make somenew progresses on the methods of detecting the signals and designing thetransmission structure of this type of electrode by taking advantage ofthe applications on the storage ring of Shanghai Synchrotron RadiationFacility (SSRF).The design of the button-type electrode was traditionally accomplished bycombining the analytical formulae and the modeling established by thefinite element analysis (FEA) simulation software such as MAFIA or CST.The performance of the result depends on the finesse of the modeling whichmay still take considerable computational time and it’s not helpful whenthe structure of the electrode needs to be modified frequently. Thisarticle discusses a new and convenient method to design the structure. Itseparates the electrode and transmission pieces with differentcharacteristic parameters into multiple coaxial transmission lines, anddescribes the electronic behavior of the electrode by using the seriescircuits of the coaxial lines, so that the simple elegant theories inelectricity could be used to analyze and compute the transmission procedure.The button-type electrodes in SSRF are used to illustrate the modeling andanalysis of the effect of the characteristic parameters of the structure.The results could provide the guide to the optimization of the operationmode of SSRF and further upgrades as well as the design experiences to othersimilar facilities. The thermodynamic performance of the electrode could also affect themeasurement in addition to the electrical property. The main purpose ofthe button-type electrode is to measurement the transverse position of thebeam. Thermal deformation is inevitable so not only additional systematicdeviation to the measurement is probable but also the equipment might bedestroyed in extreme situations. The button-type electrodes in SSRF areemployed again to demonstrate the analysis of the modeling of the heat loadeffect under different currents and different filling patterns in ANSYS.The results show that the thermal deformations caused by the heat load ofthe beam under any designed operation modes in SSRF are all small comparedto the tolerance. The effect on the position measurement is negligible,but the temperature of the electrode could reach270degree Celsius inextreme conditions. Further solution is needed to deal with the risk ofpotential damages of the equipment.