Ground-motion effects on the SSC

Abstract

Ground motion at the one-micron level can seriously degrade the collider performance. Motion of the quadrupole magnets is the main concern. Because of the high magnetic gradients in the quadrupoles, a small horizontal or vertical motion can result in a significant change in the central (closed) orbit in each of the two rings. Furthermore, for a proton-proton collider, the orbit changes in the two rings are different because the quadrupoles are arranged asymmetrically in the two rings -- i.e., a focusing quadrupole in one ring always occurs with a defocusing quadrupole in the other ring. As a consequence, at each of the four collision points, the changes in the two closed orbits due to ground motion are likely to be different, thus causing the two beam centers to miss each other with a consequent reduction in luminosity. In this report we examine these effects quantitatively for plane waves, for spreading waves from point sources, and for waves from a distribution of point sources, such as a train, but in an ideal, uniform, and semi-infinite model of the SSC site. More data on ground motion and attenuation effects at the actual SSC site are certainly needed. 8 refs., 12 figs., 1more » tab.« less