Enclosed are five jpg's summarizing the results of a survey mapping
the pulse height response of the prototype (preproduction) chamber.
All measurements were made with a Fe55 source, HV at 1800V, and
running Ar/Iso 25/75 gas mixture. Diagram.jpg is a sketch showing
the location, relative orientation and labeling of the lines across
the chamber tracked by the source during the mapping, and referred to
on the subsequent graphs. The positions are in cm. This diagram also
shows the approximate location of the crack in the glass sheet on
the outer side of the V plane (ie does not affect the U plane. As you
can see from the U plane graphs, wire 50 is almost dead. I've 
determined the problem is not in the cabling, but won't know more till
the chamber is opened. Measurements were taken over a few days, and
changing atmospheric pressure and temperature substantially affected
pulse height. Only one of the graphs contains data which compromised
internal consistency due to this effect(uplane2.jpg) and there is a note
attached to the graph addressing this. The difference in overall
pulse height between the U and V plane is due to this weather effect,
and a note on the V plane graphs points this out.

Note that the pulses trail off at +/-19cm at the centre wire of
the U plane, and ~ +/-17cm at wire 20 and 61. These wires are
8.6 cm from the centre line, and a little quick trig reveals that
+/-17cm is consistent with a 19cm active radius. On the V plane
however, the centre wire trails off at around +/-17.5cm, and wire
20 and 61 at around +/-15.5cm, consistent with an active radius
of 17.5 cm. As we know the active radius should be ~17cm for
both planes, this requires a little explanation. The answer is that
the Fe55 source is not perfectly collimated, and for the U plane
measurements, it was mounted a bit further from the surface of
the chamber. Thus the signal recorded for radius >17cm represents
off-axis x-rays sriking within the active region of the chamber.
It was observed that the signal intensity was much reduced in
this region, which is consistent with this explanation.

Pete Vincent,
TRIUMF
Nov 2-4,'99

Filename: DIAGRAM.JPG

Filename: UPLANE1.JPG

Filename: UPLANE2.JPG

Filename: VPLANE1.JPG

Filename: VPLANE2.JPG

Created for the The Center for Subatomic Research E614 Project Projects Page.

Created by The CoCoBoard.