Development of Timing Sync Circuit of Photo-cathode Rf Gun and Research on Application Possibility of Radically Polarized Laser
|School||University of Science and Technology of China|
|Course||Nuclear Technology and Applications|
|Keywords||free electron lasers (FEL) Photocathode RF gun driving laser time synchronization radically polarized laser hollow photocathode|
The free electron lasers (FEL) with short wavelength require that it’s photoinjector could provide high quality electron bunches of low emittance, low energy dispersion, and high peak current. In kinds of electron guns, The Photocathode RF gun becomes the first choice of the short wavelength FEL driven by a linac because of it’s unique advantages on those aspect. The structure of Photocathode RF gun is very complex and it involves many disciplines. We need to choose and optimize many technical proposals such as incidence pattern of laser, polarization of laser, cathode material and structure, time synchronization. Study and choice of various technical proposals are help for saving construct cost ,and ,more important , can improve the quality of electron beam. Base on practical situation of our FEL facility, the work of this paper was mainly focused on two aspects as follows: 1). synchronizing system. 2). Study on application of laser polarization. In general, we successfully developed the timing synchronization circuit of Photocathode RF gun of Hefei Light Source(HLS), and made a particular research and analysis for the issue on application possibility of radically polarized laser.In this paper, we firstly reviewed the basic principle , characteristic, application, and status of development about FEL ,then give a brief introduction of electron gun especially The Photocathode RF gun.Components about time synchronization of Photocathode RF gun at Hefei light source are described in detail. We developed the timing synchronization circuit of Photocathode RF gun with AVR MEGA128 MCU and got good precision of timing synchronization. The Photocathode RF gun successfully generate electron beam with the timing synchronization circuit, and the whole system works well. Design scheme of circuit and software are provided. On the basis of experimental result, we analysed the cause and quantity of jitter and explained current precision. Finally, on this basis, we proposed schemes of higher precision. In addition, we analysed the drift of locked phase in experiment, found out the reason, and proposed solution through consulting literature.Based on the detailed investigation of the related literatures about the Photocathode RF gun, we chosen some valuable new ideas and technologies, and gave a detailed introduction of them, such as, radically polarized laser, hollow photocathode structure. As for utilizing those new concepts on our present Photocathode RF gun, we proposed several special schemes, and made some initial, semi-quantitative analysis about what would happen with new schemes, at last, we got some constructive conclusions.