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Summary and Conclusions

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.


Table 3: Attenuation length determined using 2" PMT's following the cosmics runs and the TRIUMF beam tests. The results are compared to those from KLOE [4] and also separately reported [12].
Batch Fiber Type (mode) Attenuation Length (cm)
    Cosmics TRIUMF KLOE
1992 Bicron BCF-12     226 $\pm$ 3
1993 Bicron BCF-12     286 $\pm$ 8
N/A Kuraray SCSF-81 single-clad     321 $\pm$ 5
1992 Pol.Hi.Tech.0046 single-clad     284 $\pm$ 5
1993 Pol.Hi.Tech.0046 single-clad     267 $\pm$ 6
2000 Kuraray SCSF-81 single-clad (loose) 321 $\pm$ 22 285 $\pm$ 7  
2000 Kuraray SCSF-81 single-clad (5/4 stack)   283 $\pm$ 2  
2001 Kuraray SCSF-81 single-clad (5/4 stack)   273 $\pm$ 3  
2000 Pol.Hi.Tech.0046 single-clad (loose) 259 $\pm$ 20    
2000 Pol.Hi.Tech.0046 multi-clad (loose) 247 $\pm$ 47    
2000 Pol.Hi.Tech.0046 single-clad (5/4 stack)   Broken  
2000 Pol.Hi.Tech.0046 multi-clad (5/4 stack)   234 $\pm$ 3  


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 $\sigma =
550-700$ ps. This is consistent with the KLOE results [4] which had $\sigma = 300$ ps for the Pol.Hi.Tech. and Kuraray fibers and 400 ps for the Bicron fibers, when the number of photo-electrons collected was $N(p.e.)=30$. These numbers rise to 500-800 ps for $N(p.e.) \le 10$. From the TRIUMF measurements, fitting of the ADC spectra yielded $N(p.e.) \le 4$. 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 $N(p.e.)$ in the tens of photo-electrons and thus allow a more direct comparison to the KLOE numbers.


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2001-10-29