Theory, Design and Tests on a Prototype Module of a Compact ...

4. BEAD PULLING MEASUREMENT 81
Figure 5.10. Measurement for the coupling for stacked
cavities. In order to apply line <strong>and</strong> parabola methods,
in addition to the AC <strong>and</strong> CC screws, one can move also
(*) rod to change the CC frequency.
Figure 5.11. Measurement for the second order coupling
for stacked cavities. In order to apply line <strong>and</strong>
parabola methods, in addition to the AC <strong>and</strong> CC screws,
you can move also (*) rod to change the CC frequency.
as the resonant frequency, or of the coupled cavities, as the coupling
factor, or of the whole multi-cell structure.
For the whole structure, the parameter of interest is the electric
field distribution along the axis, which is the field that the particles
experience during their travel through the accelerator. It is very important
that the electric field level in the accelerating cavities is flat
within a certain tolerance.
In fact, a distribution field which present big relative differences
between cavities could imply different results with respect to the longitudinal
dynamic of the particles [21, 20].
Furthermore, as explained in chapter 2 the Kilpatrick criterion [26]
will limit the maximum level of field reachable, since this one will be
set for the cavity which presents the highest level, whereas in case of
flat field this condition is the same for all the cavities.