The electromagnetic calorimeter for the new muon (g-2) experiment at Fermilab will consist of arrays of PbF2 Cherenkov crystals read out by large-area silicon photo-multiplier (SiPM) sensors. We report here on measurements and simulations using 2.0 -- 4.5 GeV electrons with a 28-element prototype array. All data were obtained using fast waveform digitizers to accurately capture signal pulse shapes versus energy, impact position, angle, and crystal wrapping. The SiPMs were gain matched using a laser-based calibration system, which also provided a stabilization procedure that allowed gain correction to a level of 1e-4 per hour. After accounting for longitudinal fluctuation losses, those crystals wrapped in a white, diffusive wrapping exhibited an energy resolution sigma/E of (3.4 +- 0.1) % per sqrt(E/GeV), while those wrapped in a black, absorptive wrapping had (4.6 +- 0.3) % per sqrt(E/GeV). The white-wrapped crystals---having nearly twice the total light collection---display a generally wider and impact-position-dependent pulse shape owing to the dynamics of the light propagation, in comparison to the black-wrapped crystals, which have a narrower pulse shape that is insensitive to impact position.
@article{arxiv.1412.5525,
title = {Studies of an array of PbF2 Cherenkov crystals with large-area SiPM readout},
author = {A. T. Fienberg and L. P. Alonzi and A. Anastasi and R. Bjorkquist and D. Cauz and R. Fatemi and C. Ferrari and A. Fioretti and A. Frankenthal and C. Gabbanini and L. K. Gibbons and K. Giovanetti and S. D. Goadhouse and W. P. Gohn and T. P. Gorringe and D. W. Hertzog and M. Iacovacci and P. Kammel and J. Kaspar and B. Kiburg and L. Li and S. Mastroianni and G. Pauletta and D. A. Peterson and D. Pocanic and M. W. Smith and D. A. Sweigart and V. Tishchenko and G. Venanzoni and T. D. Van Wechel and K. B. Wall and P. Winter and K. Yai},
journal= {arXiv preprint arXiv:1412.5525},
year = {2015}
}
Comments
14 pages, 19 figures, accepted to Nucl.Instrum.Meth. A. In v2, edited Figures 14,15, and 17 for clarity, improved explanation of energy resolution systematics, added reference to SiPM