@article{597c5a35e25345a1b4164e80ecd793db,
title = "Electroluminescence TPCs at the thermal diffusion limit",
abstract = "The NEXT experiment aims at searching for the hypothetical neutrinoless double-beta decay from the 136Xe isotope using a high-purity xenon TPC. Efficient discrimination of the events through pattern recognition of the topology of primary ionisation tracks is a major requirement for the experiment. However, it is limited by the diffusion of electrons. It is known that the addition of a small fraction of a molecular gas to xenon reduces electron diffusion. On the other hand, the electroluminescence (EL) yield drops and the achievable energy resolution may be compromised. We have studied the effect of adding several molecular gases to xenon (CO2, CH4 and CF4) on the EL yield and energy resolution obtained in a small prototype of driftless gas proportional scintillation counter. We have compared our results on the scintillation characteristics (EL yield and energy resolution) with a microscopic simulation, obtaining the diffusion coefficients in those conditions as well. Accordingly, electron diffusion may be reduced from about 10 mm/m for pure xenon down to 2.5 mm/m using additive concentrations of about 0.05%, 0.2% and 0.02% for CO2, CH4 and CF4, respectively. Our results show that CF4 admixtures present the highest EL yield in those conditions, but very poor energy resolution as a result of huge fluctuations observed in the EL formation. CH4 presents the best energy resolution despite the EL yield being the lowest. The results obtained with xenon admixtures are extrapolated to the operational conditions of the NEXT-100 TPC. CO2 and CH4 show potential as molecular additives in a large xenon TPC. While CO2 has some operational constraints, making it difficult to be used in a large TPC, CH4 shows the best performance and stability as molecular additive to be used in the NEXT-100 TPC, with an extrapolated energy resolution of 0.4% at 2.45 MeV for concentrations below 0.4%, which is only slightly worse than the one obtained for pure xenon. We demonstrate the possibility to have an electroluminescence TPC operating very close to the thermal diffusion limit without jeopardizing the TPC performance, if CO2 or CH4 are chosen as additives.[Figure not available: see fulltext.]",
keywords = "Dark Matter and Double Beta Decay (experiments), Particle correlations and fluctuations, Photon production, Rare decay",
author = "{The NEXT collaboration} and Henriques, {C. A.O.} and Monteiro, {C. M.B.} and D. Gonz{\'a}lez-D{\'i}az and Azevedo, {C. D.R.} and Freitas, {E. D.C.} and Mano, {R. D.P.} and Jorge, {M. R.} and Fernandes, {A. F.M.} and G{\'o}mez-Cadenas, {J. J.} and Fernandes, {L. M.P.} and C. Adams and V. {\'A}lvarez and L. Arazi and K. Bailey and F. Ballester and Benlloch-Rodr{\'i}guez, {J. M.} and Borges, {F. I.G.M.} and A. Botas and S. C{\'a}rcel and Carri{\'o}n, {J. V.} and S. Cebri{\'a}n and Conde, {C. A.N.} and J. D{\'i}az and M. Diesburg and J. Escada and R. Esteve and R. Felkai and P. Ferrario and Ferreira, {A. L.} and J. Generowicz and A. Goldschmidt and R. Guenette and Guti{\'e}rrez, {R. M.} and K. Hafidi and J. Hauptman and Hernandez, {A. I.} and {Hernando Morata}, {J. A.} and V. Herrero and S. Johnston and Jones, {B. J.P.} and M. Kekic and L. Labarga and A. Laing and P. Lebrun and N. L{\'o}pez-March and M. Losada and J. Mart{\'i}n-Albo and A. Mart{\'i}nez and G. Mart{\'i}nez-Lema and A. McDonald",
note = "Funding Information: Article funded by SCOAP3. Funding Information: The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT; the European Union{\textquoteright}s Framework Programme for Research and Innovation Horizon 2020 (2014-2020) under the Marie Sklo dowska-Curie Grant Agreements No. 674896, 690575 and 740055; the Ministerio de Econom{\'i}a y Competitividad of Spain under grants FIS2014-53371-C04, the Severo Ochoa Program SEV-2014-0398 and the Mar{\'i}a de Maetzu Program MDM-2016-0692; the GVA of Spain under grants PROMETEO/2016/120 and SEJI/2017/011; the Portuguese FCT under project PTDC/FIS-NUC/2525/2014, under project UID/FIS/04559/2013 to fund the activities of LIBPhys, and under grants PD/BD/105921/2014, SFRH/BPD/109180/2015 and SFRH/BPD/76842/2011; the U.S. Department of Energy under contracts number DE-AC02-07CH11359 (Fermi National Accelerator Laboratory), DE-AC02-06CH11357 (Argonne National Laboratory), DE-FG02-13ER42020 (Texas A&M) and DE-SC0017721 (University of Texas at Arlington); and the University of Texas at Arlington. DGD acknowledges Ramon y Cajal program (Spain) under contract number RYC-2015-18820. We also warmly acknowledge the Laboratori Nazionali del Gran Sasso (LNGS) and the Dark Side collaboration for their help with TPB coating of various parts of the NEXT-White TPC. Finally, we are grateful to the Laboratorio Subterr{\'a}neo de Canfranc for hosting and supporting the NEXT experiment.",
year = "2019",
month = jan,
day = "1",
doi = "10.1007/JHEP01(2019)027",
language = "English (US)",
volume = "2019",
journal = "Journal of High Energy Physics",
issn = "1126-6708",
publisher = "Springer Verlag",
number = "1",
}