# Abstracts

## XX International Linac Conference

## TU301 (Invited)

**Presenter: **Roger H. Miller (SLAC)

** email: **rhm@slac.stanford.edu

**Status: **Complete

**FullText: **
ps.gz
or pdf
# Accelerator Structures for Linear Colliders

R.H. Miller (SLAC)

Linear Colliders require high gradient (to reduce length dependent
costs), high shunt impedance (to reduce power dependent costs) accelerator structures
in which the long range dipole wakefields have been reduced by 2 to 3 orders of
magnitude. The precise dipole wake reduction factor required depends on many factors
including the beam intensity and time structure, the accelerator aperture and
accelerating gradient, the strength of the focussing, the alignment precision and
position stability of accelerator structures and the focussing elements, the
effectiveness of the tuning procedures and feedback system, the pulse to pulse
stability of the injected beam, and the required emittance at the final focus. For
the purposes of this paper we accept that large reduction factors are required and
discuss various approaches to achieving them. There are basically two approaches:
detuning and damping, which can be used very effectively in combination. Damping can
be accomplished either by introducing loss selectively into regions of the
accelerating structure cells, or by coupling the dipole modes out of the accelerating
region and absorbing them in external loads of lossy materials. Detuning can be
accomplished within each accelerator section or from section to section or both. The
goal of detuning is to avoid the coherent summation of the wakefields from all cells
in an accelerator, and it is possible to achieve destructive interference so that the
wakefields from different cells in the accelerator cancel each other as seen by the
bunches of electrons travelling through the linac. Several different approaches have
achieved 2 orders of magnitude or more reduction in the long range dipole wakefields
so that they pose no restriction on the length of the bunch trains which can be used
for linear colliders.

Linac2000 Author Index

Linac2000 Menu
Comments or Questions to
linac2000@slac.stanford.edu