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