During the summer of 2001, measurements were obtained of the performance of scintillating fibers, using cosmic rays at Regina and 100 MeV pions at the TRIUMF M11 beam line. Three types of fibers were tested in various configurations: Kuraray SCSF-81 single-clad, and Pol.Hi.Tech.0046 single- and multi-clad.
The results for the attenuation length and timing resolution measurements are summarized in Table 3, and compared with equivalent results published by the KLOE Collaboration [4]. It should be mentioned that the KLOE Collaboration also tested BICRON [13] scintillating fibers, but recent price quotes from BICRON revealed that these are too costly for the Hall D project and so were excluded from testing for this reason.
|
As was mentioned in Section 5, the Kuraray fibers showed a consistenly superior performance as per the light attenuation coefficient. They also exhibited a better timing resolution. However, the Pol.Hi.Tech. multi-clad fibers performed better in terms of light yield, based simply on the observation that for the same bias and gain the mean of the ADC spectra for these fibers was higher. In this respect the multi-clad fibers appear to be superior to the single-clad ones, and as far as the light attenuation is concerned, the Kuraray were overall better than the Pol.Hi.Tech. Thus, it was concluded, that multi-clad fibers should be ordered from Kuraray and tested as well.
Regarding the timing resolution, all fiber bundles gave
ps. This is consistent with the KLOE results [4]
which had
ps for the Pol.Hi.Tech. and Kuraray fibers
and 400 ps for the Bicron fibers, when the number of photo-electrons
collected was
. These numbers rise to 500-800 ps for
. From the TRIUMF measurements, fitting of the ADC
spectra yielded
. Thus, the TRIUMF results are
consistent, at least qualitatively, with those from KLOE.
A more detailed analysis of the TRIUMF results will be carried out in
the near future, and an understanding of the systematically higher
values for the light attenuation coefficient in the cosmics tests will
be sought. In addition, the 5/4 stack fiber bundles will be tested
with cosmic rays at Regina once again, to improve the statistics over
those obtained last summer. Future measurements with a prototype BCAL
segment will cetainly yield in the tens of photo-electrons
and thus allow a more direct comparison to the KLOE numbers.