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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) - 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 ” (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: 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

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