Design Of Beam Diagnostics System For High-Brightness Injector In HLS

Beam diagnostics is an essential constituent of any accelerator. It is the ’organ of sense’ showing the properties and the behavior of the beam. It deals with the real beam including all possible imperfections of a real technical installation, which plays a vital role in knowing the real state of the machine and improving the quality of beam. This dissertation is devoted to extensively investigating advanced beam diagnostics at the high-bightness injector in Hefei Light Source (HLS) and finding possible way to improve the beam quality. The emphasis of this dissertation is to introduce how to set up all beam diagnostics system in the injector and the measurement results using the beam diagnostics system.Firstly, this paper introduces the system structure of high-brightness injector. The function and related parameters of each sub-system are also introduced. Then, how to set up and test the beam diagnostics system for high-brightness injector are discussed in detail. The applications of the diagnostics system are also presented.In the beam transverse size measurement system, the solution consisting of YAG crystal screen and GigE Vision network camera are chosen. In this system, the camera zoom factor (real object dimension over pixel number occupied in the image) can be gotten in an easy and fast way. Using this system, the beam size with different machine parameters and at different measurement positions along the beam direction are measured. The error sources in the measurement are analyzed.We perform systematical investigations on low emittance measurement with the photocathode RF gun developed in HLS. Solenoid scan method is applied to measure the thermal emittance while the beam charge is very low. Multi-slit and Single Slit scan method are applied to measure the transverse emittance while the beam charge is high, in which the beam is space charge dominated. The measurement results using both methods are compared.In the beam charge measurement system, an integrating current transformer (ICT) and a fast current transformer (FCT) are applied as the non-intercepting tools to measure the beam charge. An online beam charge measurement system is developed using Matlab software and oscilloscope. With the help of this measurement system, we can measure the beam charge, the charge of dark current with different solenoid current at different klystron power level and the quantum efficiency (QE) of cathode material, which is copper in our case.For energy and energy spread measurements, we used magnetic analysis system. Simulations are done to choose the suitable dimensions of vacuum pipe. With the help of this system, the beam momentum at different klystron power level is measured, and then the measurement results are compared with the simulation results.Concerning the beam position measurement, stripline beam position monitor (BPM) and Digital Beam Position Processor-Libera are applied in our system. The variation of beam position during the operation time is measured. The beam charge information gotten from BPM signal is compared with the output from ICT.Finally, the problems which limite the operation of the gun and the beam parameter measurements are discussed and analyzed; some advises for the future optimization of the facility are provided.