Abstract
In the framework of the HISTARS (HIE-ISOLDE Timing Array for Reaction Studies) project at ISOLDE/CERN it is planned to install a $\gamma$-ray array for fast-timing measurements. State-of-the-art crystals are LaBr$_3$(Ce)[1][2][3] or CeBr$_3$[4][5] inorganic scintillators, which are customarily fitted with fast photomultiplier tubes (PMTs) or SiPMs.
In this work, we have characterized four different head-on PMTs with bialkali photocathode by Hamamatsu in combination with a LaBr$_3$(Ce) crystal with the shape of a truncated cone 1.5" in height and with bases of 1.5" and 1" in diameter. Among the chosen PMTs a customized version of the 2-inch 8-stage bialkali photocathode R9779[6] in the assembly H10570 is used as a reference. The other three, newer PMTs, are a 1.5-inch 8-stage R13408[7], and a 2-inch 8-stage R13089 model[7], in two different assemblies, H13719-Y006 and H13719-Y007.
We report on the time response at $^{22}$Na and $^{60}$Co photon energies using a fast digitizer module and signal processing methods based on a genetic algorithm for the time pick-up[8]. Results on energy resolution, linearity, and time walk will also be presented.
Keywords: photomultiplier tube, Hamamatsu R9779, Hamamatsu R13408, Hamamatsu R13089, inorganic scintillator, LaBr$_{3}$(Ce), digital signal processing, time resolution, time walk, fast timing
References
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[2] V. Vedia, M. Carmona-Gallardo, L. Fraile, H. Mach, J. Udías, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 857, 98 (2017). DOI https://doi.org/10.1016/j.nima.2017.03.030. URL https://www.sciencedirect.com/science/article/pii/S0168900217303704
[3] L. Fraile, V. Sánchez-Tembleque, J. Benito, M. García-Díez, J. Udías, V. Vedia, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 463, 394 (2020). DOI https://doi.org/10.1016/j.nimb.2019.04.044. URL https://www.sciencedirect.com/science/article/pii/S0168583X19302289
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[5] L. Fraile, H. Mach, V. Vedia, B. Olaizola, V. Paziy, E. Picado, J. Udías, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 701, 235 (2013). DOI https://doi.org/10.1016/j.nima.2012.11.009. URL https://www.sciencedirect.com/science/article/pii/S0168900212013010
[6] Hamamatsu. Hamamatsu Photonic Systems R9779 datasheet. URL https://www.digchip.com/datasheets/parts/datasheet/190/r9779-pdf.php
