Research On Low Beta Superconducting Cavity Testing

The low beta superconducting cavity is used for a proton or a heavy ionsuperconducting linac as the accelerating part. Before the low beta superconductingcavity online operation, testing the performance of the cavity is essential. So the mainresearch issue of this thesis is the testing of low beta superconducting cavities.First of all, the testing of low beta superconducting cavities is inseparable from thedesign, the machining and the surface treatment of the cavity. Many measurementparameters, such as the average accelerating field, the peak electric field, etc., dependon electromagnetic simulation parameters of the cavity design. Good machining andsurface processing of the cavity are also necessary conditions for testing successfully.So the thesis expounds the working principle of the low beta superconducting cavity,introduces the design, the machining, the surface processing, and the design concept ofessential fundamental infrastructures in the beginning.Secondly, the testing of low beta superconducting cavities belongs to the RFmeasurement domain. So the thesis bases on the principle of the RF measurement,explains the theory of the superconducting cavity testing. The VCO-PLL (voltagecontrolled oscillator phase lock loop) is the most important technique. It can be used tolock the eigen frequency of the superconducting cavity. Based on the theory of the PLL,the application condition is verified by the modeling and the simulation.After that, the thesis describes the design of the test plant for low beta cavities indetail. It includes fundamental infrastructures, accessory equipments, hardwares, softwares, and protecting interlocks.The chapter five of the thesis explains the choice method of the coupling antennalength through the RF measurement. It also explains the method of the cable calibrationand measuring parameters such as df/dp, Q0, Epkand Lorentz detuning in detail. It alsoshows the test result of IMP-HWR010-S superconducting cavities.The last chapter of the thesis analyses various physical phenomena which haveemerged in the low temperature test of low beta superconducting cavities. This chapterespecially analyses the forced vibration effect of the superconducting cavity. Thephenomenon of this effect in the superconducting cavity is that perplexing twofrequency peaks appear on the spectrum analyzer. The thesis explains this phenomenonby mean of the math of the forced vibration and simulation tools. And this researchbecame an innovative point of the thesis. Finally, contraposing various physicalphenomena in the test, RF conditioning techniques of the low beta superconductingcavities have been discussed.