R.M. Jones* (SLAC), N.M. Kroll* ** (UCSD & SLAC), R.H. Miller*, and G.V. Stupakov* (SLAC)
In the NLC scenario thousands of X-band linacs will be used to accelerate the beam from 10 GeV to collide at a CEM (center of mass) energy of 1 TeV. Small misalignments of each of the individual structures (or the cells of which each individual structure is composed) will give rise to wakesfields which kick the beam from its electrical axis. This wakefield can resonantly drive the beam into an instability known as BBU (beam break up) or at the very least it will dilute the emittance of the beam. In previous work  a Gaussian distribution in the frequencies of the cells was utilized to prevent constructive interference of the modes of which the wakefield is composed. Geometrical errors in fabricating the structures can lead to the beam being resonantly driven and BBU will result. In order to avoid this worst-case situation a new distribution of frequencies is considered in which the wakefield ideally falls off rapidly in a Sinc^4(x) fashion. A comparison between the wakefield resulting from the new distribution and a Gaussian distribution is given. The progress of the beam through 5,000 or so structures is monitored in phase space and results on this are presented.
 R.M.Jones et al, 'Advanced Damped Detuned Structure Development at SLAC', Proc. of the 17th Particle Accelerator Conference (PAC), p548,(1997)
*Work supported at SLAC under U.S. Department of Energy grant number DE-AC03-76SF00515.
**Work supported under U.S. Department of Energy grant number DE-FG03-93ER40759
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