Interaction Region Issues at the Nlc”

The Z&AC-based NLC working group’ has been considering issues relevant to the operation of an X-band 0.5-l .O TeV collider. This report summarizes some of the results the group has achieved to date. The NLC2 will collide trains of closely spaced bunches of lOlo particles. Typical parameters are 1.4 ns for the inter-bunch spacing, 100 bunches/train, and 180 trains/set. Its final focus (FF) will provide spot sizes at the interaction point (IP) of dimensions ox = 300400 nm, oy = 2-3 nm, and crz = 100 l.trn. The closely spaced bunches and the desire to have each bunch interact only with its partner imply that there must be a crossing angle at the IP. The high charge density will cause backgrounds due to electromagnetic beambeam interactions and particle detectors with good timing resolution will be required to separate hits from the interaction causing the trigger from the background hits arising from other bunches in the train. The 2 nm beam spots will challenge experimenters to get and keep the beams in collision. They will require special consideration to be given to issues of alignment, ground motion, and vibrations induced by the transfer of cooling fluids. The detector masking must be able to reduce to manageable levels the backgrounds due to synchrotron radiation in the final quadrupoles and to the beam-beam interaction. Simulations of these backgrounds should consider the worst case of 2 beam trains of 1012 particles each at 500 GeV.