The original observations and measurements defining the new positions of
the lead and D counter can be found on pages 10-13 of log book 4. Here
is a summary derived from these measurements:
Midplane of the lead plate is at z = 149.82.
The x,y coordinates should be the same as before. We positioned the lead
so that it is 2 inches from the 2.5 inch diameter beam pipe. The
coordinates that I calculate for the corners of the lead are:
x y
5.13 -0.53
10.78 5.13
5.13 10.78
-0.53 5.13
Midplane of the D counter is at z = 157.19 (but see below).
>From the measurements we took, I infer the corners of the D counter to
be at the following coordinates:
x y
5.64 -6.82
-1.81 7.55
12.40 14.91
19.85 0.54
The D counter could not be set truly perpendicular to the beam direction
because of interference with a chamber electonics stand. It was set at a
slight angle (as viewed from above) which I measured crudely to be about
5 degrees from the true perpendicular. The sense of the angle is such
that corridor edge of the counters is upstream of the beam side edge.
The z coordinate quoted above applies to the beam side.
Chambers 122 and 124 were readjusted (in situ) to be at a greater stereo
angle. Previously they had been set at 5 degrees, now they are set at 10
degrees. I will communicate new alignment numbers when I have calculated
them.
In rebuilding the D counter stand, we inadvertently interchanged the
positions of D-top and D-bottom. The cabling was made to follow the
counters. So "D-top" and "D-bottom" are names of counters and do not
refer to their positions.
The kicker counters had to be removed during the access because the
kicker magnet was being changed. We tried to replace them in their
original positions but, as before and after photographs show, the
counter designated BH2 (horizontal under the kicker) was rotated 90
degrees about its long axis. So its next-to-longest axis is now
horizontal instead of vertical.
Tom