Characterization of the Hamamatsu S8664 Avalanche Photodiode for X-Ray and VUV-light detection

We present the first operation of the Avalanche Photodiode (APD) from Hamamatsu to xenon scintillation light and to direct X-rays of 22.1 keV and 5.9 keV. A large non-linear response was observed for the direct X-ray detection. At 415 V APD bias voltage it was of about 30 % for 22.1 keV and about 45 % for 5.9 keV. The quantum efficiency for 172 nm photons has been measured to be 69 +/- 15 %.Comment: 11 pages, 3 figures, submitted to Elsevie

Primary and secondary scintillation measurements in a xenon Gas Proportional Scintillation Counter

NEXT is a new experiment to search for neutrinoless double beta decay using a 100 kg radio-pure high-pressure gaseous xenon TPC. The detector requires excellent energy resolution, which can be achieved in a Xe TPC with electroluminescence readout. Hamamatsu R8520-06SEL photomultipliers are good candidates for the scintillation readout. The performance of this photomultiplier, used as VUV photosensor in a gas proportional scintillation counter, was investigated. Initial results for the detection of primary and secondary scintillation produced as a result of the interaction of 5.9 keV X-rays in gaseous xenon, at room temperature and at pressures up to 3 bar, are presented. An energy resolution of 8.0% was obtained for secondary scintillation produced by 5.9 keV X-rays. No significant variation of the primary scintillation was observed for different pressures (1, 2 and 3 bar) and for electric fields up to 0.8 V cm-1 torr-1 in the drift region, demonstrating negligible recombination luminescence. A primary scintillation yield of 81 \pm 7 photons was obtained for 5.9 keV X-rays, corresponding to a mean energy of 72 \pm 6 eV to produce a primary scintillation photon in xenon.Comment: 16 pages, 10 figures, accepted for publication in JINS

Low-diffusion Xe-He gas mixtures for rare-event detection: electroluminescence yield

[EN] High pressure xenon Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification are being proposed for rare event detection such as directional dark matter, double electron capture and double beta decay detection. The discrimination of the rare event through the topological signature of primary ionisation trails is a major asset for this type of TPC when compared to single liquid or double-phase TPCs, limited mainly by the high electron diffusion in pure xenon. Helium admixtures with xenon can be an attractive solution to reduce the electron diffu- sion significantly, improving the discrimination efficiency of these optical TPCs. We have measured the electroluminescence (EL) yield of Xe-He mixtures, in the range of 0 to 30% He and demonstrated the small impact on the EL yield of the addition of helium to pure xenon. For a typical reduced electric field of 2.5 kV/cm/bar in the EL region, the EL yield is lowered by similar to 2%, 3%, 6% and 10% for 10%, 15%, 20% and 30% of helium concentration, respectively. This decrease is less than what has been obtained from the most recent simulation framework in the literature. The impact of the addition of helium on EL statistical fluctuations is negligible, within the experimental uncertainties. The present results are an important benchmark for the simulation tools to be applied to future optical TPCs based on Xe-He mixtures.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's Framework Programme for Research and Innovation Horizon 2020 (2014-2020) under the Marie Sklodowska-Curie Grant Agreements No. 674896, 690575 and 740055; the Ministerio de Economa y Competitividad of Spain under grants FIS2014-53371-C04, RTI2018-095979, the Severo Ochoa Program SEV-2014-0398 and the Mara 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; the U.S. Department of Energy under contracts number DEAC02-06CH11357 (Argonne National Laboratory), DE-AC0207CH11359 (Fermi National Accelerator Laboratory), DE-FG02-13ER42020 (Texas A& M) and DE-SC0019223/DESC0019054 (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 Subterraneo de Canfranc for hosting and supporting the NEXT experiment.Fernandes, A.; Henriques, C.; Mano, R.; González-Díaz, D.; Azevedo, C.; Silva, P.; Gómez-Cadenas, J.... (2020). Low-diffusion Xe-He gas mixtures for rare-event detection: electroluminescence yield. Journal of High Energy Physics (Online). (4):1-18. https://doi.org/10.1007/JHEP04(2020)034S1184D.R. Nygren, Columnar recombination: a tool for nuclear recoil directional sensitivity in a xenon-based direct detection WIMP search, J. Phys. Conf. Ser.460 (2013) 012006 [INSPIRE].G. Mohlabeng et al., Dark matter directionality revisited with a high pressure xenon gas detector, JHEP07 (2015) 092 [arXiv:1503.03937] [INSPIRE].N.S. Phan, R.J. Lauer, E.R. Lee, D. Loomba, J.A.J. Matthews and E.H. Miller, GEM-based TPC with CCD Imaging for Directional Dark Matter Detection, Astropart. Phys.84 (2016) 82 [arXiv:1510.02170] [INSPIRE].J. Martin-Albo et al., Sensitivity of NEXT-100 to neutrinoless double beta decay, JHEP05 (2016) 159 [arXiv:1511.09246] [INSPIRE].K. Nakamura et al., AXEL — a high pressure xenon gas TPC for neutrinoless double beta decay search, Nucl. Instrum. Meth.A 845 (2017) 394 [INSPIRE].D. Yu. Akimov, A.A. Burenkov, V.F. Kuzichev, V.L. Morgunov and V.N. Solovev, Low background experiments with high pressure gas scintillation proportional detector, physics/9704021 [INSPIRE].Yu. M. Gavrilyuk et al., A technique for searching for the 2K capture in124Xe with a copper proportional counter, Phys. Atom. Nucl.78 (2015) 1563 [INSPIRE].Yu. M. Gavrilyuk et al., Results of In-Depth Analysis of Data Obtained in the Experimental Search for 2K (2ν)-Capture in78Kr, Phys. Part. Nucl.49 (2018) 540 [INSPIRE].C.A.N. Conde and A.J.P.L. Policarpo, A Gas Proportional Scintillation Counter, Nucl. Instrum. Meth.53 (1967) 7.A.J.P.L. Policarpo, M.A.F. Alves and C.A.N. Conde, The Argon-Nitrogen Proportional Scintillation Counter, Nucl. Instrum. Meth.55 (1967) 105.J.M.F. dos Santos et al., Development of portable gas proportional scintillation counters for x-ray spectrometry, X-Ray Spectrom.30 (2001) 373.NEXT collaboration, Accurate γ and MeV-electron track reconstruction with an ultra-low diffusion Xenon/TMA TPC at 10 atm, Nucl. Instrum. Meth.A 804 (2015) 8 [arXiv:1504.03678] [INSPIRE].NEXT collaboration, Characterisation of NEXT-DEMO using xenon KαX-rays, 2014 JINST9 P10007 [arXiv:1407.3966] [INSPIRE].NEXT collaboration, Energy calibration of the NEXT-White detector with 1% resolution near Qββof136Xe, JHEP10 (2019) 230 [arXiv:1905.13110] [INSPIRE].R. Lüscher et al., Search for beta beta decay in Xe-136: New results from the Gotthard experiment, Phys. Lett.B 434 (1998) 407 [INSPIRE].NEXT collaboration, First proof of topological signature in the high pressure xenon gas TPC with electroluminescence amplification for the NEXT experiment, JHEP01 (2016) 104 [arXiv:1507.05902] [INSPIRE].NEXT collaboration, Background rejection in NEXT using deep neural networks, 2017 JINST12 T01004 [arXiv:1609.06202] [INSPIRE].NEXT collaboration, The Next White (NEW) Detector, 2018 JINST13 P12010 [arXiv:1804.02409] [INSPIRE].H. Qiao et al., Signal-background discrimination with convolutional neural networks in the PandaX-III experiment using MC simulation, Sci. China Phys. Mech. Astron.61 (2018) 101007 [arXiv:1802.03489] [INSPIRE].NEXT collaboration, Secondary scintillation yield of xenon with sub-percent levels of CO2additive for rare-event detection, Phys. Lett.B 773 (2017) 663 [arXiv:1704.01623] [INSPIRE].C.M.B. Monteiro et al., Secondary Scintillation Yield in Pure Xenon, 2007 JINST2 P05001 [physics/0702142] [INSPIRE].C.M.B. Monteiro, J.A.M. Lopes, J.F. C.A. Veloso and J.M.F. dos Santos, Secondary scintillation yield in pure argon, Phys. Lett.B 668 (2008) 167 [INSPIRE].C.A.B. Oliveira et al., A simulation toolkit for electroluminescence assessment in rare event experiments, Phys. Lett.B 703 (2011) 217 [arXiv:1103.6237] [INSPIRE].E.D.C. Freitas et al., Secondary scintillation yield in high-pressure xenon gas for neutrinoless double beta decay (0νββ) search, Phys. Lett.B 684 (2010) 205 [INSPIRE].C.M.B. Monteiro et al., Secondary scintillation yield from gaseous micropattern electron multipliers in direct dark matter detection, Phys. Lett.B 677 (2009) 133 [INSPIRE].C.M.B. Monteiro, L.M.P. Fernandes, J.F. C.A. Veloso, C.A.B. Oliveira and J.M.F. dos Santos, Secondary scintillation yield from GEM and THGEM gaseous electron multipliers for direct dark matter search, Phys. Lett.B 714 (2012) 18 [INSPIRE].C. Balan et al., MicrOMEGAs operation in high pressure xenon: Charge and scintillation readout, 2011 JINST6 P02006 [arXiv:1009.2960] [INSPIRE].C.M.B. Monteiro, L.M.P. Fernandes, J.F. C.A. Veloso and J.M.F. dos Santos, Secondary scintillation readout from GEM and THGEM with a large area avalanche photodiode, 2012 JINST7 P06012 [INSPIRE].C.D.R. Azevedo et al., An homeopathic cure to pure Xenon large diffusion, 2016 JINST11 C02007 [arXiv:1511.07189] [INSPIRE].C.D.R. Azevedo et al., Microscopic simulation of xenon-based optical TPCs in the presence of molecular additives, Nucl. Intrum. Meth.A 877 (2018) 157 [arXiv:1705.09481] [INSPIRE].NEXT collaboration, Electroluminescence TPCs at the Thermal Diffusion Limit, JHEP01 (2019) 027 [arXiv:1806.05891] [INSPIRE].R.C. Lanza et al., Gas scintillators for imaging of low energy isotopes, IEEE Trans. Nucl. Sci.34 (1987) 406.R. Felkai et al., Helium-Xenon mixtures to improve the topological signature in high pressure gas xenon TPCs, Nucl. Intrum. Meth.A 905 (2018) 82 [arXiv:1710.05600] [INSPIRE].NEXT collaboration, Electron Drift and Longitudinal Diffusion in High Pressure Xenon-Helium Gas Mixtures, 2019 JINST14 P08009 [arXiv:1902.05544] [INSPIRE].J.A.M. Lopes et al., A xenon gas proportional scintillation counter with a UV-sensitive large-area avalanche photodiode, IEEE Trans. Nucl. Sci.48 (2001) 312.C.M.B. Monteiro et al., An argon gas proportional scintillation counter with UV avalanche photodiode scintillation readout, IEEE Trans. Nucl. Sci.48 (2001) 1081.Advanced Photonix, Inc., 1240 Avenida Acaso, Camarillo, CA 93012, U.S.A. .L.M.P. Fernandes et al., Characterization of large area avalanche photodiodes in X-ray and VUV-light detection, 2007 JINST2 P08005 [physics/0702130] [INSPIRE].L.M.P. Fernandes, E.D.C. Freitas, M. Ball, J.J. Gomez-Cadenas, C.M.B. Monteiro, N. Yahlali et al., Primary and secondary scintillation measurements in a xenon Gas Proportional Scintillation Counter, 2010 JINST5 P09006 [Erratum ibid.5 (2010) A12001] [arXiv:1009.2719] [INSPIRE].C.A.B. Oliveira, M. Sorel, J. Martin-Albo, J.J. Gomez-Cadenas, A.L. Ferreira and J.F. C.A. Veloso, Energy Resolution studies for NEXT, 2011 JINST6 P05007 [arXiv:1105.2954] [INSPIRE].D.F. Anderson et al., A large area, gas scintillation proportional counter, Nucl. Instrum. Meth.163 (1979) 125.T.Z. Kowalski et al., Fano factor implications from gas scintillation proportional counter measurements, Nucl. Instrum. Meth.A 279 (1989) 567.T. Doke, Basic properties of high pressure xenon gas as detector medium, in Proceedings of the XeSAT, Tokyo Japan (2005), pg. 92.S.J.C. do Carmo et al., Experimental Study of the ω-Values and Fano Factors of Gaseous Xenon and Ar-Xe Mixtures for X-Rays, IEEE Trans. Nucl. Sci.55 (2008) 2637.A. Buzulutskov, E. Shemyakina, A. Bondar, A. Dolgov, E. Frolov, V. Nosov et al., Revealing neutral bremsstrahlung in two-phase argon electroluminescence, Astropart. Phys.103 (2018) 29 [arXiv:1803.05329] [INSPIRE]

Evaluation of turbulent dissipation rate retrievals from Doppler Cloud Radar

Turbulent dissipation rate retrievals from cloud radar Doppler velocity measurements are evaluated using independent, in situ observations in Arctic stratocumulus clouds. In situ validation data sets of dissipation rate are derived using sonic anemometer measurements from a tethered balloon and high frequency pressure variation observations from a research aircraft, both flown in proximity to stationary, ground-based radars. Modest biases are found among the data sets in particularly low- or high-turbulence regimes, but in general the radar-retrieved values correspond well with the in situ measurements. Root mean square differences are typically a factor of 4-6 relative to any given magnitude of dissipation rate. These differences are no larger than those found when comparing dissipation rates computed from tetheredballoon and meteorological tower-mounted sonic anemometer measurements made at spatial distances of a few hundred meters. Temporal lag analyses suggest that approximately half of the observed differences are due to spatial sampling considerations, such that the anticipated radar-based retrieval uncertainty is on the order of a factor of 2-3. Moreover, radar retrievals are clearly able to capture the vertical dissipation rate structure observed by the in situ sensors, while offering substantially more information on the time variability of turbulence profiles. Together these evaluations indicate that radar-based retrievals can, at a minimum, be used to determine the vertical structure of turbulence in Arctic stratocumulus clouds

Low-diffusion Xe-He gas mixtures for rare-event detection: electroluminescence yield

High pressure xenon Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification are being proposed for rare event detection such as directional dark matter, double electron capture and double beta decay detection. The discrimination of the rare event through the topological signature of primary ionisation trails is a major asset for this type of TPC when compared to single liquid or double-phase TPCs, limited mainly by the high electron diffusion in pure xenon. Helium admixtures with xenon can be an attractive solution to reduce the electron diffu- sion significantly, improving the discrimination efficiency of these optical TPCs. We have measured the electroluminescence (EL) yield of Xe–He mixtures, in the range of 0 to 30% He and demonstrated the small impact on the EL yield of the addition of helium to pure xenon. For a typical reduced electric field of 2.5 kV/cm/bar in the EL region, the EL yield is lowered by ∼ 2%, 3%, 6% and 10% for 10%, 15%, 20% and 30% of helium concentration, respectively. This decrease is less than what has been obtained from the most recent simulation framework in the literature. The impact of the addition of helium on EL statistical fluctuations is negligible, within the experimental uncertainties. The present results are an important benchmark for the simulation tools to be applied to future optical TPCs based on Xe-He mixtures. [Figure not available: see fulltext.]

The Lamb shift in muonic hydrogen and the proton radius

By means of pulsed laser spectroscopy applied to muonic hydrogen (μ− p) we have measured the 2S F = 1 1/2 − 2PF = 2 3/2 transition frequency to be 49881.88(76) GHz. By comparing this measurement with its theoretical prediction based on bound-state QED we have determined a proton radius value of rp = 0.84184 (67) fm. This new value is an order of magnitude preciser than previous results but disagrees by 5 standard deviations from the CODATA and the electronproton scattering values. An overview of the present effort attempting to solve the observed discrepancy is given. Using the measured isotope shift of the 1S-2S transition in regular hydrogen and deuterium also the rms charge radius of the deuteron rd = 2.12809 (31) fm has been determined. Moreover we present here the motivations for the measurements of the μ 4He + and μ 3He + 2S-2P splittings. The alpha and triton charge radii are extracted from these measurements with relative accuracies of few 10 − 4. Measurements could help to solve the observed discrepancy, lead to the best test of hydrogen-like energy levels and provide crucial tests for few-nucleon ab-initio theories and potentials

An improved measurement of electron-ion recombination in high-pressure xenon gas

We report on results obtained with the NEXT-DEMO prototype of the NEXT-100 high-pressure xenon gas time projection chamber (TPC), exposed to an alpha decay calibration source. Compared to our previous measurements with alpha particles, an upgraded detector and improved analysis techniques have been used. We measure event-by-event correlated fluctuations between ionization and scintillation due to electron-ion recombination in the gas, with correlation coeffcients between -0.80 and -0.56 depending on the drift field conditions. By combining the two signals, we obtain a 2.8% FWHM energy resolution for 5.49 MeV alpha particles and a measurement of the optical gain of the electroluminescent TPC. The improved energy resolution also allows us to measure the specific activity of the radon in the gas due to natural impurities. Finally, we measure the average ratio of excited to ionized atoms produced in the xenon gas by alpha particles to be 0:561 0:045, translating into an average energy to produce a primary scintillation photon ofWex = (39:2 3:2) eV.This work was supported by the following agencies and institutions: the European Research Council under the Advanced Grant 339787-NEXT; the Ministerio de Economia y Competitividad of Spain under grants CONSOLIDER-Ingenio 2010 CSD2008-0037 (CUP), FPA2009-13697-C04 and FIS2012-37947-C04; the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02-05CH11231; and the Portuguese FCT and FEDER through the program COMPETE, project PTDC/FIS/103860/2008.Serra, L.; Sorel, M.; Alvarez, V.; Borges, FIG.; Camargo, M.; Carcel, S.; Cebrian, S.... (2015). An improved measurement of electron-ion recombination in high-pressure xenon gas. Journal of Instrumentation. 10:1-19. https://doi.org/10.1088/1748-0221/10/03/P03025S1191

The NEXT White (NEW) detector

Conceived to host 5 kg of xenon at a pressure of 15 bar in the fiducial volume, the NEXT-White apparatus is currently the largest high pressure xenon gas TPC using electroluminescent amplification in the world. It is also a 1:2 scale model of the NEXT-100 detector for Xe-136 beta beta 0 nu decay searches, scheduled to start operations in 2019. Both detectors measure the energy of the event using a plane of photomultipliers located behind a transparent cathode. They can also reconstruct the trajectories of charged tracks in the dense gas of the TPC with the help of a plane of silicon photomultipliers located behind the anode. A sophisticated gas system, common to both detectors, allows the high gas purity needed to guarantee a long electron lifetime. NEXT-White has been operating since October 2016 at the Laboratorio Subterraneo de Canfranc (LSC), in Spain. This paper describes the detector and associated infrastructures, as well as the main aspects of its initial operation

Measurement of radon-induced backgrounds in the NEXT double beta decay experiment

The measurement of the internal 222Rn activity in the NEXT-White detector during the so-called Run-II period with 136Xe-depleted xenon is discussed in detail, together with its implications for double beta decay searches in NEXT. The activity is measured through the alpha production rate induced in the fiducial volume by 222Rn and its alpha-emitting progeny. The specific activity is measured to be (38.1 ± 2.2 (stat.) ± 5.9 (syst.)) mBq/m3. Radon-induced electrons have also been characterized from the decay of the 214Bi daughter ions plating out on the cathode of the time projection chamber. From our studies, we conclude that radon-induced backgrounds are sufficiently low to enable a successful NEXT-100 physics program, as the projected rate contribution should not exceed 0.1 counts/yr in the neutrinoless double beta decay sample