The Secondary Electron Yield for High-Energy Proton Bombardment on Aluminum Target

Abstract

The phenomenon of secondary electron emission was discovered in the beginning of the 20th century. 1 It is well known that there are two mechanisms contributing to the secondary electron emission, 1 potential emission and kinetic emission. The former may proceed in front of the surface either by Auger neutralization or by resonance neutralization following Auger deexcitation when the potential energy of the projectile is two times larger than that of the work function. The latter is more important than the former in the MeV range of projectile energies. It is dominant in many ion-beam analyses since they are usually performed with MeV ion beams. Secondary electron emission is the dominant surface yield when MeV-energy protons enter metallic targets, with the yields of sputtered ions or reflected protons being insignificant. 2 The source of these electrons is the Coulomb interaction of the fast protons with electrons within about 100 A of the surface of the target. In the experiment described here, the secondary-electron emission coefficient is measured for 33, 39 and 42 MeV protons from the cyclotron accelerator passing through aluminum surfaces. When we measure the beam current, it is hard to get exact incident beam current because of excessive evaluation by reason of secondary electron. We try to get down it using negative electron voltage, it is very hard to get down because secondary electron energy is very high in case of high energy incident beam. So we need exact data for these but that is poor, and we can't correct its present situation. In this study, we try to measure this secondary electron using cyclotron accelerator it is many used for isotope production. 3,4