Neutral Molecule Desorption from SS(304) and A1(6061) Due to Particle Bombardments
The pressure in both electron and proton storage rings is dependent on the particle wall bombardment molecular desorption rates due in one case (proton storage rings) to ~ keV ions while in the other to ~ 100 eV electrons. Also in order to minimize secondary electron amplification effects in both types of machines the secondary electron emission coefficient should be as low as possible. The above quantities have been measured on A1(6061) and SS(304) materials having had various treatments including a sputter deposition of Ti and TiN in the case of A1. The results indicate for both electron and proton storage rings that SS(304) materials properly prepared have particular advantages over A1 considering both molecular desorption yields and secondary electron emission effects.
Secondary electron amplification in high energy proton accelerators
Abstract A model is presented which may result in secondary electron growth during multiampere, bunched beam operation of proton accelerators or storage rings.
Monte carlo simulation of events with Drell-Yan lepton pairs from antiproton-proton collisions
The complete knowledge of the nucleon spin structure at leading twist requires also addressing the transverse spin distribution of quarks, or transversity, which is yet unexplored because of its chiral-odd nature. Transversity can be best extracted from single-spin asymmetries in fully polarized Drell-Yan processes with antiprotons, where valence contributions are involved anyway. Alternatively, in single-polarized Drell-Yan the transversity happens convoluted with another chiral-odd function, which is likely to be responsible for the well known (and yet unexplained) violation of the Lam-Tung sum rule in the corresponding unpolarized cross section. We present Monte Carlo simulations for the unpolarized and single-polarized Drell-Yan pp{sup ({up_arrow}}{sup )}{yields}{mu}{sup +}{mu}{sup -}X at different center-of-mass energies in both configurations where the antiproton beam hits a fixed proton target or it collides on another proton beam. The goal is to estimate the minimum number of events needed to extract the above chiral-odd distributions from future measurements at the high energy storage ring (HESR) at GSI. It is important to study the feasibility of such experiments at HESR in order to demonstrate that interesting spin physics can be explored already using unpolarized antiprotons.