| The THz and X-ray light sources. based on FEL or ERL. all requires low emit-tance and high brightness electron beam, which can be provided only by photo-injector. Based on the successful compact Thz-FEL light source, China academy of Engineering physics(CAEP) has been trying to build a high average power THz-FEL and a THz-ERL light sources. To minimize the emittance in electron gun and to get high average current by cathode are very important for ERL.The topic of this thesis is the high-brightness photo-injector, which includes three parts:analyzing the emittance growth effected by higher order mode in RF gun, study-ing and compensating the emittance in CAEP DC-gun, and introducing and studying a diamond amplified cathode.First of all in order to obtain high-brightness electron beam, the emittance in photo-injector must be studied systematically and deeply. This thesis introduces the main emittance growth mechanisms in injector. And the3th RF effect on beam trans-verse and longitudinal RMS radius and emittance is studied in theory. It is found that only the beam energy disperse is changed.Emittance growth induced by space charge effect is very important, especially for CW DC-gun photo-injector. In order to obtain high-brightness electron beam, it needs to be compensated. In this thesis, the linear space charge force and its effect on electron transverse emittance is studied, principle and properties of emittance compensation by solenoid are analyzed. The China Academy of Engineering Physics DC-gun photo-injector with a solenoid is also simulated by code Parmela. Simulated results indicate that the normalized transverse emittance of80pC bunch at the350keV DC-gun exist is5.14mm·mrad. And after compensated by a solenoid, it becomes1.27mm·mrad. The emittance of beam is well compensated.To obtain high-brightness electron beam, the cathode which could be able to pro-vide high average current is also important. The diamond-amplifier cathode offers an-other and more widely applicable way to form high average-current, high brightness, and low thermal emittance electron beams. In this thesis, The mechanism, physical properties and the electron beam qualities of diamond-amplifier cathode are present-ed. Also, in this thesis, we have implemented a2D Monte Carlo model to simulate secondary electron transport in diamond. We have found that the drift velocity is sen-sitive to diamond temperature and electric field applied, but not sensitive to the low impurity density(<1017/cm-3). With the simulation, it is get that saturation velocity of secondary electron is1.88×107cm/s, and mobility without applied field is3731.55cm2/Vs. Also, we have studied properties of a secondary electron bunch transported in diamond, and found the effect of space charge under our considered electron cloud density is small.The nature of the diamond thin film materials is the critical factor in diamond am-plifier cathode experiment. The thesis not only studies the diamond amplifier cathode theoretically, but also measurements the secondary electron gain in transmission-mode which is the first stage of experiment. The result of gain is2-3in our primary ex-periment which is not good enough for diamond amplifier cathode. With better quality diamond and better experiment conditions, we expect that the electron transmission through diamond will be appropriate for diamond amplifier cathode. |
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