P.A. (Sander) Breur Nikhef, Netherlands Radon signals in XENON1T XeSAT 2017 XENON1T Our goal: Our setup: 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 2 XENON1T is taking science data 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 3 XENON1T is taking science data 10/2016 03/2017 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 4 Radon expectations 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 5 MC background expectation Physics reach of the XENON1T dark matter experiment, http://arxiv.org/abs/1512.07501 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 6 Reducing radon • Surface cleaning/coating • Emanation measurements • Expectation: 10 μBq/kg for XENON1T More info: “Radon depletion in xenon boil-off gas” (arXiv:1611.03737) and “Online 222Rn removal by cryogenic distillation in the Radon emanation paper in preparation XENON100 experiment” (arXiv: 1702.06942) 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 7 The 'radon' spectrum 5.6 MeV Low energy Low 7.8 MeV 5.4 MeV 6.1 MeV Isotope Energy [MeV] Half-life 210Po 5.4 138 d 222Rn 5.6 3.8 d 218Po 6.1 3.1 m Physics reach of the XENON1T dark matter experiment, http://arxiv.org/abs/1512.07501 214Po 7.8 162.3 us 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 8 Radon signals in XENON1T 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 9 The four alpha lines of Radon 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 10 The four alpha lines of Radon • 214Po has a half life of 164μs • 214Bi and 214Po are always recorded in the same event window S1alpha S2beta S1beta S2alpha 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 11 The alpha spectrum • One day of background data • Depth slice (-20 > Z > -60 cm) • Fit: Crystal Ball & 3 Gaussians Isotope Energy [MeV] Half-life 210Po 5.4 138 d 222Rn 5.6 3.8 d 218Po 6.1 3.1 m 214Po 7.8 162.3 μs 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 12 Radon evolution over time • The 218Po and 214Bi Po concentration give the upper limit and lower limits for 214Pb • XENON1T has reached its background goal of 10 μBq/kg • Additionally the distillation column in reverse mode decreases the radon concentration by almost 20% (→ See talk by M. Murra) 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 13 Radon for calibration 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 14 222Rn: Electron lifetime • Daily measurements to monitor purity • 222Rn and 218Po only 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 15 222Rn: Electron lifetime • Daily measurements to monitor purity • 222Rn and 218Po only 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 16 222Rn: Light & Charge yield monitoring 218Po 222Rn ArXiv:0910.4956v1 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 17 220Rn for low energy calibration • 220Rn source successfully deployed for electronic recoil band in XENON1T More info: “A Rn-220 source for the calibration of low-background experiments” (arXiv:1602.01138) 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 18 The next steps 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 19 Spatial tracking of radon isotopes 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 20 Desaturation of alpha signals 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 21 Radon distillation • XENON100: Reduction factor R > 27 at 95% C.L. XENON100 • XENON1T: first test shows a 20% decrease More info: “Online 222Rn removal by cryogenic distillation in the XENON100 experiment” (arXiv:1702.06942) 05/04/2017 Xesat 2017 - P.A. Breur (Nikhef) - XENON 22 Conclusion • XENON1T achieved the lowest background level of all LXe experiments • 222Rn used as a ‘free’ daily calibration source • 220Rn source successfully deployed for low energy calibration • Radon background can be mitigated by distillation and spatial isotope tracking.