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The beam-beam effects are mainly due to nonlinearity of interaction of
colliding bunches, and complete theory of the beam-beam effects is yet
unavailable. At the same time, the linear part of the beam-beam force is
readily accounted for in the linear lattice analysis at the weak-strong
approach. In electron-positron colliders, effect of the lattice
modification by opposing bunch focusing on the equilibrium radiation
emittance is important at high values of the space charge parameter, so one
should correctly evaluate this dynamic radiation emittance of the weak
beam, which may differ a lot from the nominal emittance, already in the
linear beam-beam force model. The correct evaluation of the dynamic
radiation emittance at high space charge parameters is important in
analysis of the beam-beam effects. Specifically, it is essential in the
flip-flop effect models for strong-strong interaction.
The linearized beam-beam force is equivalent to focusing insertion in
linear lattice of the collider. Its action leads to beta-beat around the
arc and results in variation of the equilibrium radiation emittance as
function of the beam-beam parameter.
And very often an estimate made with the equivalent thin lens insertion at
the Interaction Point (IP), already gives an idea of the lattice function
distortion due to the linearized beam-beam interaction (known as the
dynamic beta-function). For more exact quantitative fit with experiment it
is required to take into account the longitudinal distribution of a
particles in the bunch.
The observation system for transverse beam sizes in storage ring based on
the 16 digital CCD cameras will be allow to control in detail the dynamic
beta effect and to evaluate of the dynamic radiation emittance of the beams
at different values of space charge parameters. Figure 1 shows a variation
of the transverse beam sizes which arising due to insertion of the focusing
lens (opposing buch) at interaction points (IP1, 2).

[pic]

Fig. 1. Transverse beam sizies in VEPP-2000 storage ring without opposing
bunch
(dashed lines) and its availability (solid lines) at space charge
parameters 0.05.
The black points are observation places of the transverse beam sizes.