Secondary Electron Production at the SNS Storage Ring Collimator*

S.Y. Zhang Brookhaven National Laboratory, Upton, lWZ USA CWJ-j perpendicular rncident hasanangle8= O,and a range of Secondary electron (SE) production is briefly reviewed. If the collimator of the SNS storage ring allows proton beam scraping to take place, the electron yield might be quite large. At the AGS Booster, by steering the AU3’+ ion beam into the electrostatic rnflector,beam scraping effect on SE production is studied. The results of this experiment can be lmnslated into the situation of proton beam scraping at the SNS collimator. It seems sufficient to support a new look of the SNS ring collimator design. Secondary Electron Production Insecondary electron emission, the electronic stopping (Coulomb collision) is dominant if the projectile velocity is larger than the Bohr velocity 2.18x 108cm/ s(# = 0.0073). If the primaryion, proton, or electron have the same velocity, the kinetics of the collision is very similar [1,2]. The Seiler model shows that the peak SE production energy of projectile is aroundEk =0.9 A4eV I Z@ = 0.044). AlsQ according to this model, the SE production rate at the SNS beam energy, Ek = LOGeVl u(# = 0.875), is about 10% of the peak yield. Since the’ electronic stopping power of the target is approximately proportionalto q2, whereq is the charge state of the projectile, it was believed that the SE yield Y also has a q2dependence [5,6]. However, experimental results have shown that it is more likely a