Deflector: Spatial
Separation
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The
deflector is essentially a parallel plate capacitor. The electric field between
the plates accelerates fragments of different charge-to-mass ratios at
different rates in a direction perpendicular to the ion beam axis. Suppose that
the electric field
is uniform and confined to the region between
the plates. Let the y-axis point in the direction of the electric field of the
deflector. The acceleration
of a fragment with charge
and
mass
in the y direction will be:
Suppose that the deflector is
length in the ion beam direction. If the fragment
enters the deflector with a velocity
in the ion beam direction then the time
that it spends inside the deflector is:
When the fragment exits the
deflector it will have a velocity in the y-direction given by:
Therefore the fragment will be
deflected by an angle measured from the axis of the ion beam (z-axis)
given by:
Letting ,
we can express
as:
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