The scintillating fibers were procured in spools. Fiber strands of
approximately 3 m in length were cut and their ends were polished
using 3 grades of sandpaper (1500 grit, 3 micron and 0.3 m)
from a fiber polishing kit. A microscope was used to inspect each
fiber end and polishing was continued until the ends looked flat and
with as few imperfections as possible.
The fibers were then bundled (nine fibers per bundle) and inserted in
black electical-grade tubing. As this tubing was not entirely opaque,
for the cosmic ray tests it was wrapped with black electrical tape to
eliminate light leaks and to hold the fibers in place. Approximately
5 cm of bare fibers protruded from each end, and these were inserted
in a 3 mm-diameter, 1 cm-deep hole drilled in a 1
''
plexiglass light rod that was subsequently coupled to a standard
dynode-chain PMT (8575 2'' Burle PMT [7]) using optical
grease [8]. The same optical grease was also inserted in the
hole and smeared on the ends of the fibers. The fibers and PMT's were
placed in the ``coffin'', a black wooden box approximately 4 m in
length designed to block out light completely [9]. Two
scintillator paddle counters were used to provide the ``trigger'' or
interaction point of the cosmic rays with the SciFi, as depicted in
Figure 1.
This method of fiber coupling worked reasonably well for the cosmic ray tests since the fiber ends and the PMT's were not moved. Instead, the trigger counters were scanned across the length of the fiber bundles. However, for the TRIUMF tests the fiber bundles had to be moved to place different points in the beam. This motion caused problems in being able to reproduce the fiber coupling and, therefore, the black tubing method (termed ``loose mode'') was abandoned in favour of a new arrangement.
The new arrangement began with a 3 m-long piece of 2''-wide black optical tape that was placed sticky side up on a long table and was held down at intervals by narrow 1''-wide black optical tape. Five fibers were placed parallel to one another on the sticky side of the wide tape, leaving about 5 cm free at each end. Short (1''-2'' long) pieces of large cable ties were placed at intervals along the edge of the two outermost fibers and parallel to them to hold all five fibers in place. An additional four fibers were placed on top of the original five and staggered so that each of the upper-layer fibers fell between two lower-layer ones, and then another piece of the wide black optical tape was placed on top to seal them from light leaks and to hold them in place. The fiber ends were then inserted into the light rod as described above, and these new fiber ribbons (termed ``5/4 stack'') were held firmly against the PMT housing by using wide optical tape. The description of this arrangement may be found as well in reference [10].
It should be mentioned that in 1992 the KLOE collaboration had determined that the Kuraray fibers exhibited a sensitivity to UV light, whereas the Pol.Hi.Tech. batches did not. By 1994, Pol.Hi.Tech. modified the doping in their scintillating fibers which resulted in an improvement of their light attenuation. However, this most likely rendered these fibers sensitive to UV light. In the preparations in Regina and TRIUMF precautions were taken to avoid exposure of the fibers to fluorescent lighting. (Prior to learning about this UV sensitivity, the Y2000 batch of Kuraray fibers had been exposed to UV lighting for a total of approximately two hours.)