Long-lived radon daughters are a critical background source in experiments searching for low-energy rare events. Originating from radon in ambient air, radioactive polonium, bismuth and lead isotopes ...plate-out on materials that are later employed in the experiment. In this paper, we examine cleaning procedures for their capability to remove radon daughters from PTFE surfaces, a material often used in liquid xenon TPCs. We find a large difference between the removal efficiency obtained for the decay chains of
222
Rn and
220
Rn. This indicates that the plate-out mechanism has an effect on the cleaning success. While the long-lived
222
Rn daughters can be reduced by a factor of 2, the removal of
220
Rn daughters is up to 10 times more efficient depending on the treatment. Furthermore, the impact of a nitric acid based PTFE cleaning on the liquid xenon purity is investigated in a small-scale liquid xenon TPC.
The XENON1T dark matter experiment Aalbers, J.; Alfonsi, M.; Amaro, F. D. ...
European physical journal. C, Particles and fields,
12/2017, Letnik:
77, Številka:
12
Journal Article
Recenzirano
Odprti dostop
The XENON1T experiment at the Laboratori Nazionali del Gran Sasso (LNGS) is the first WIMP dark matter detector operating with a liquid xenon target mass above the ton-scale. Out of its 3.2 t liquid ...xenon inventory, 2.0 t constitute the active target of the dual-phase time projection chamber. The scintillation and ionization signals from particle interactions are detected with low-background photomultipliers. This article describes the XENON1T instrument and its subsystems as well as strategies to achieve an unprecedented low background level. First results on the detector response and the performance of the subsystems are also presented.
Radon depletion in xenon boil-off gas Bruenner, S.; Cichon, D.; Lindemann, S. ...
European physical journal. C, Particles and fields,
03/2017, Letnik:
77, Številka:
3
Journal Article
Recenzirano
Odprti dostop
An important background in detectors using liquid xenon for rare event searches arises from the decays of radon and its daughters. We report for the first time a reduction of
222
Rn in the gas phase ...above a liquid xenon reservoir. We show a reduction factor of
≳
4
for the
222
Rn concentration in boil-off xenon gas compared to the radon enriched liquid phase. A semiconductor-based
α
-detector and miniaturized proportional counters are used to detect the radon. As the radon depletion in the boil-off gas is understood as a single-stage distillation process, this result establishes the suitability of cryogenic distillation to separate radon from xenon down to the
10
-
15
mol/mol level.
The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410 has been developed by Hamamatsu for dark matter direct detection experiments using liquid xenon as the target material. ...We present the results from the joint effort between the XENON collaboration and the Hamamatsu company to produce a highly radio-pure photosensor (version R11410-21) for the XENON1T dark matter experiment. After introducing the photosensor and its components, we show the methods and results of the radioactive contamination measurements of the individual materials employed in the photomultiplier production. We then discuss the adopted strategies to reduce the radioactivity of the various PMT versions. Finally, we detail the results from screening 286 tubes with ultra-low background germanium detectors, as well as their implications for the expected electronic and nuclear recoil background of the XENON1T experiment.
Abstract
A novel online distillation technique was developed for the XENON1T dark matter experiment to reduce intrinsic background components more volatile than xenon, such as krypton or argon, while ...the detector was operating. The method is based on a continuous purification of the gaseous volume of the detector system using the XENON1T cryogenic distillation column. A krypton-in-xenon concentration of (360 ± 60) ppq was achieved. It is the lowest concentration measured in the fiducial volume of an operating dark matter detector to date. A model was developed and fitted to the data to describe the krypton evolution in the liquid and gas volumes of the detector system for several operation modes over the time span of 550 days, including the commissioning and science runs of XENON1T. The online distillation was also successfully applied to remove 37Ar after its injection for a low-energy calibration in XENON1T. This makes the usage of 37Ar as a regular calibration source possible in the future. The online distillation can be applied to next-generation liquid xenon time projection chamber experiments to remove krypton prior to, or during, any science run. The model developed here allows further optimization of the distillation strategy for future large-scale detectors.
Xenon dual-phase time projection chambers designed to search for weakly interacting massive particles have so far shown a relative energy resolution which degrades with energy above
∼
200 keV due to ...the saturation effects. This has limited their sensitivity in the search for rare events like the neutrinoless double-beta decay of
136
Xe
at its
Q
value,
Q
β
β
≃
2.46
MeV
. For the XENON1T dual-phase time projection chamber, we demonstrate that the relative energy resolution at
1
σ
/
μ
is as low as (
0.80
±
0.02
) % in its one-ton fiducial mass, and for single-site interactions at
Q
β
β
. We also present a new signal correction method to rectify the saturation effects of the signal readout system, resulting in more accurate position reconstruction and indirectly improving the energy resolution. The very good result achieved in XENON1T opens up new windows for the xenon dual-phase dark matter detectors to simultaneously search for other rare events.
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