Proposed ILC Parameters(LCC-0003)

Abstract

In this note, we describe the proposed working parameter set for the KEK-SLAC ILC linear collider and discuss the reasons leading to the values listed; more extensive discussion of the optimization process will be found in subsequent notes. The parameter set is listed in Table 1 and is compared with the JLC 3-97 parameters and the NLC ZDR parameters in Table 2. The new parameter set has an operating plane which ranges from low IP emittances and high luminosity (cases A) to large IP emittances and smaller luminosity (cases C). Over this range, the bunch charge, bunch length, and IP beta functions are varied, however, the parameters have been chosen so that the tolerances on the accelerating structures are roughly constant. The collider must be designed to operate over the entire parameter range. In all cases, the parameters were optimized for 120 Hz operation. The scaling to 150 Hz is straightforward--either the beam parameters are held constant and the luminosity and ac power are increased or there are small reductions in the bunch charge and an ensuing loosening of the tolerances. Similarly, scaling to 100 Hz operation is also possible, although, if one wants to maintain the luminosity in thismore » case, the bunch charge must be increased and the beamstrahlung energy loss increases to as much as 15%. In arriving at the parameters, most of the emphasis has been on cost reduction. Thus, at times, we have sacrificed the rf and ac efficiency to obtain a situation that requires fewer rf power sources or significantly looser tolerances; this will be discussed further below. The other issues considered in the parameter determination include: the bunch spacing and beam pulse length limits, the rf structure length, the iris radii ({alpha}/{lambda}), and the upgrade path from 500 GeV to 1 TeV cms; each of these issues will be discussed further subsequently.« less