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arXiv · 2501.13755

The Impact of Helium Exposure on the PMTs of the SuperNEMO Experiment

SuperNEMO Collaboration·X. Aguerre·A. S. Barabash·A. Basharina-Freshville·M. Bongrand·Ch. Bourgeois·D. Breton·R. Breier·J. Busto·C. Cerna·M. Ceschia·E. Chauveau·A. Chopra·L. Dawson·D. Duchesneau·J. J. Evans·D. Filosofov·X. Garrido·C. Girard-Carillo·M. Granjon·M. Hoballah·R. Hodák·G. Horner·M. H. Hussain·A. Islam·A. Jérémie·S. Jullian·J. Kaizer·A. Klimenko·O. Kochetov·F. Koňařík·S. I. Konovalov·T. Křižák·S. Kovalenko·A. Lahaie·K. Lang·Y. Lemière·P. Li·J. Maalmi·M. Macko·F. Mamedov·C. Marquet·F. Mauger·A. Mendl·B. Morgan·I. Nemchenok·M. Nomachi·V. Palušová·C. Patrick·T. Pavicic·F. Perrot·M. Petro·F. Piquemal·P. Povinec·S. Pratt·M. Proga·W. S. Quinn·Y. A. Ramachers·C. L. Riddle·N. Rukhadze·R. Saakyan·R. Salazar·J. Sedgbeer·Yu. Shitov·L. Simard·F. Šimkovic·A. Smolnikov·S. Söldner-Rembold·I. Štekl·J. Suhonen·H. Tedjditi·J. Thomas·V. Timkin·V. I. Tretyak·Vl. I. Tretyak·G. Turnbull·V. I. Umatov·Y. Vereshchaka·D. Waters
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Abstract

The performance of Hamamatsu 8" photomultiplier tubes (PMTs) of the type used in the SuperNEMO neutrinoless double-beta decay experiment (R5912-MOD), is investigated as a function of exposure to helium (He) gas. Two PMTs were monitored for over a year, one exposed to varying concentrations of He, and the other kept in standard atmospheric conditions as a control. Both PMTs were exposed to light signals generated by a Bi-207 radioactive source that provided consistent large input PMT signals similar to those that are typical of the SuperNEMO experiment. The energy resolution of PMT signals corresponding to 1 MeV energy scale determined from the Bi-207 decay spectrum, shows a negligible degradation with He exposure; however the rate of after-pulsing shows a clear increase with He exposure, which is modelled and compared to diffusion theory. A method for reconstructing the partial pressure of He within the PMT and a method for determining the He breakdown point, are introduced. The implications for long-term SuperNEMO operations are briefly discussed.

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SuperNEMO Collaboration, X. Aguerre, A. S. Barabash, A. Basharina-Freshville, M. Bongrand, Ch. Bourgeois, D. Breton, R. Breier, J. Busto, C. Cerna, M. Ceschia, E. Chauveau, A. Chopra, L. Dawson, D. Duchesneau, J. J. Evans, D. Filosofov, X. Garrido, C. Girard-Carillo, M. Granjon, M. Hoballah, R. Hodák, G. Horner, M. H. Hussain, A. Islam, A. Jérémie, S. Jullian, J. Kaizer, A. Klimenko, O. Kochetov, F. Koňařík, S. I. Konovalov, T. Křižák, S. Kovalenko, A. Lahaie, K. Lang, Y. Lemière, P. Li, J. Maalmi, M. Macko, F. Mamedov, C. Marquet, F. Mauger, A. Mendl, B. Morgan, I. Nemchenok, M. Nomachi, V. Palušová, C. Patrick, T. Pavicic, F. Perrot, M. Petro, F. Piquemal, P. Povinec, S. Pratt, M. Proga, W. S. Quinn, Y. A. Ramachers, C. L. Riddle, N. Rukhadze, R. Saakyan, R. Salazar, J. Sedgbeer, Yu. Shitov, L. Simard, F. Šimkovic, A. Smolnikov, S. Söldner-Rembold, I. Štekl, J. Suhonen, H. Tedjditi, J. Thomas, V. Timkin, V. I. Tretyak, Vl. I. Tretyak, G. Turnbull, V. I. Umatov, Y. Vereshchaka, D. Waters. 2025-01-23. The Impact of Helium Exposure on the PMTs of the SuperNEMO Experiment. https://arxiv.org/abs/2501.13755

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