Measurements and studies of secondary electron emission of diamond amplified photocathode.

摘要

The Diamond Amplifier Photocathode (DAP) provides a very promising new approach to provide high-average-current, high-brightness electron source for accelerators.;High purity Chemical Vapor Deposition diamond films are used as the amplifier of the electron beam. Primary electrons are provided by a traditional photocathode and are bombarded onto tens of nanometer thick metal coating and into the diamond sample. Within 1 micron travel in the diamond, the primary electrons generate secondary electrons by collision on the order of two magnitudes increase in number. Secondary electrons are accelerated through the diamond and will emit into vacuum through surface with hydrogen termination. The electrons emitted should have very low thermal emittance, for the electrons are constrained to the bottom of the conduction band. The entire sample preparing process includes severe chemical etching, metallization coating, and hydrogenation. Measurements are done with specific equipments, and the quality of preparation is controlled by the Atomic Force Microscope and electron or photon spectroscopy.;This thesis covers all aspects of this project, and will focus on the physics of electron transfer within and out of the diamond sample. The measurements of the gain are taken and compared under different conditions for obtaining the highest amplification. The experiments have already demonstrated the secondary electron gain of over 200 in the diamond and over 70 for emission into the vacuum. The diamond will also act as a vacuum barrier, protecting the photocathode from contamination by the accelerator vacuum. The emittance measurement is carefully designed to reach the precision of 0.1eV. Theoretical calculations and computational simulation are developed to fit with our experimental results.