\subsection {Silicon Tracker Alignment and Operations}

The Canadian group made two hardware contributions to the CDF-II
silicon tracker. These consisted of a set of precisely positionable
feet for the three SVX-II barrels, allowing them to be aligned
parallel to one another to better than 40 $\mu$rad, and a set of
remote controlled positioning motors that enables us to re-orient the
whole silicon tracker with a precision of better than 10
$\mu$rad. Both of these are necessary to ensure optimal
operation of our silicon track trigger, which reconstructs track
impact parameters in the plane perpendicular to the detector axis.
These hardware contributions led naturally to our playing
major roles in assembly and installation of the silicon tracker. We 
have also led interventions on two occasions, since then, to re-orient 
the silicon tracker when the beam has drifted more than 100 $\mu$rad from the
silicon tracker axis, the most recent of these dates back to 2003. We no
longer foresee having to re-orient the silicon detector, although we
continue to monitor the orientation of the tracker with respect to
the beamline. Our experience in silicon position monitoring was extended
by Vollrath, with supervision from Savard, to monitor the position of
the end-plug calorimeters. After openings to service the tracker, or
(infrequent) quenches of the CDF solenoid, these detectors can move
by several millimeters. Prototype optical position monitors were installed
on the end-plug calorimeters in late 2004 and their effectiveness is
being evaluated.

Our involvement in the silicon tracker has led naturally to two sets
of detector performance studies. Lai and Sabik have led the effort to
understand the shape of the interaction region in CDF with supervision
from Trischuk. Over the last year, our interaction region shape
measurements have been scrutinized by Tevatron machine experts
searching for clues to couplings between the horizontal and vertical
machine tunes that could explain the 10\% differences in instantaneous
luminosity seen between CDF and D0.  We have also become heavily
involved in the alignment of the silicon tracker. Since late 2002, one
of us (Trischuk) has led the silicon detector performance study group
(that has about a dozen active studies). Two of our students who
recently graduated focused their service work on the effort to
understand the intrinsic resolution of our novel innermost ``layer
00'' silicon ladders. This device is mounted directly on the beampipe
at radii between 1.5 and 1.7 cm from the beam line. As a result of
their work, layer 00 is now an integral part of our physics studies and
will be a key to improving the incisiveness of CDF's measurement of
the $B_s^0$ oscillation rate.

As a result of his work in the silicon studies group, Trischuk took on
the added responsibility of overall silicon project co-leader in
2003-04. There he led a group of graduate students, postdocs, and other
researchers/faculty members (about 20 FTE from ten institutions) in
the collaboration and was responsible for all aspects of the silicon
detector's operation, maintenance, and exploitation. One of the main
emphases of his time as silicon project leader was the streamlining of
silicon operations that was becoming more and more critical as the
emphasis of the collaboration shifted to data analysis, or hardware
projects that were not part of the CDF programme.

We will continue our detector performance studies of the silicon
tracker, as performance needs fed back from physics studies dictate
and as student effort is available. Although we are very close to the
design resolutions of all elements of the detector, the issues will
focus more on maintaining this performance as occupancies increase --
with higher luminosities -- as well as monitoring detector performance
as the sensors begin to approach their radiation dose lifetime. This
experience will be invaluable as similar fates await the silicon
trackers in ATLAS at the LHC. This work provides the
basis for service work contributions to the collaboration of at least
one faculty member and one or more students.
