Run II at the Tevatron will begin with 36 bunches and
eventually be upgraded to about 100 bunches (132 nsec running).
With 36 bunches there are twelve potential collision
points around the Tevatron ring. The use of electrostatic separators
allows the beams to collide with a zero crossing angle at the
DØ and CDF interaction
points, but have a 5
separation at the other parasitic crossings.
With 132 nsec running, however, it will no longer be possible to avoid
the first parasitic crossing without the introduction of
a crossing angle to separate the beams within the low beta quadrupoles.
A preliminary study of 132 nsec running [40, 41]
indicates that a crossing angle of about 140 
rad will provide
a 3 separation
of the beams at the first parasitic crossing
(roughly the quadrupole
spectrometer Roman pot
locations)
and 6.5 at the other undesirable crossing points.
The dipole spectrometer situation is improved by the addition of the
crossing angle which will result in a 2.3 mm separation of the
p and 
beams [40], with the proton beam located
farthest away from the pots. It should be possible to move the
pots slightly closer to the beam in this case, due to the
smaller beam width.
Figure 22 shows the effect of a crossing angle on the
quadrupole spectrometers.
There is no longer symmetric acceptance in the plane of the crossing
angle. The current scenario assumes that
the crossing angle is split among
the x and y directions, and results in a 
separation
of the beam in each plane [40].
For the case of proton side pots, the effect of the separated
beams is that one spectrometer is still 
from the proton beam
but the other side now has the beam in the way and can only be
inserted to 
( from the beam separation and 
from the effective width of the beam). The overall acceptance
for this side will thus drop by almost a factor of two, since
pot displacements give an acceptance almost 10 times smaller than .
For the anti-proton side pots, the acceptance is actually increased
by about 50% as for one
spectrometer the pots can be lowered to from the beam
(which gives an increase of about a factor of 3),
while the other side spectrometer will be at 
and can be ignored.
Figure 22: The pot locations in a crossing angle
scenario are shown. The proton and anti-proton beams
are separated by resulting in effective pot
positions of 8 and 10 for p pots and
7 and 11 for pots.
The addition of a crossing angle, although not desirable from complexity and symmetry arguments, does not significantly affect the overall acceptance and does not compromise the goals of the FPD.