Preliminary Physical And Principle Studies Of Diamond Amplified Electron Gun

As a novel concept which can produce high current,low emittance,high brightness electron beam,diamond amplifier photocathode(DAP)can be applied into some advanced accelerator apparatus,such as high power XFEL,energy recovery linac light source,electron cooling hadron collider and so on.DAP was first proposed by Ben-Zvi,et al.at BNL,USA,and have been under a series of simulations and experiments for over ten years.It had been approved by experiments that secondary transmission gain exceeded 200,and the highest emission gain reached 178.The key component of DAP is the diamond film window(DFM)made of high purity CVD diamond with the thickness of 30?m.One side of the film is coated with metal and another side is hydrogenated to have negative electron affinity(NEA)so that secondary electrons can be emitted more easily.Functionally,DFM can be taken as the intermediate amplification emitter for primary electrons.Primary electrons generated from the conventional photocathode,firstly be accelerated up to 10keV,then penetrate through the coated metal and finally enter into the diamond.Two orders of magnitude of the amplified secondary electrons will be produced in the region with thickness of less than 1?m close to the incident surface.Afterwards,under the applied strong external field,the secondaries will transport towards the NEA surface,and finally be emitted into vacuum.In this thesis,the characteristics of secondary electron in diamond were studied theoretically and simulated,and verified by transmission mode experiment.This thesis mainly includes four parts,they are Monte Carlo simulation for secondary amplification process,numerical simulation for secodnary transmission process,introduction of theory and experimental results for secondary emission process and experimental verification of secondary amplification in transmission mode.The first part introduced in detail the Monte Carlo simulation method and calculation results for secodnary amplification process.We simulated the amplification process by self-complied 3D Monte Carlo program,quantitatively analyzed the energy loss of primary electrons caused by four kinds of metal,the range of primary electrons,the spatial distribution and yield of secondary electrons,and obtained the secondary distribution function along the path.The second part simulated the transmission process of secondary electrons.The diffusion-drift euqation and Poisson equation of electrons and holes were deduced,and the numerical calcualtion method was realized.The response of electrons and holes to different initial electron beams and applied fields was quantitatively analyzed.The third part was a summary of some theoretical knowledge and experimental results involved in the secondary emission process.This part would be helpful to guide the experiment of amplified secondary emission of diamond in the future.The fourth part was the most important,which introduced the related transmission mode experimental work.We had built a secondary amplification transmission mode experimental platform,designed and improved the sample holder,and studied the secondary transmission gain for electronic grade polycrystalline diamond.Some results showed that for the initial 10keV electron beam,the maximum observed gain exceeded 500.