Distillation of Liquid Xenon to Remove Krypton
K. Abe, J. Hosaka, T. Iida, M. Ikeda, K. Kobayashi, Y. Koshio, A. Minamino, M. Miura, S. Moriyama, M. Nakahata, Y. Nakajima, T. Namba, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, K. Ueshima, M. Yamashita, K. Kaneyuki, Y. Ebizuka, J. Kikuchi, A. Ota, S. Suzuki, T. Takahashi, H. Hagiwara, T. Kamei, K. Miyamoto, T. Nagase, S. Nakamura, Y. Ozaki, T. Sato, Y. Fukuda, T. Sato, K. Nishijima, M. Sakurai, T. Maruyama, D. Motoki, Y. Itow, H. Ohsumi, S. Tasaka, S. B. Kim, Y. D. Kim, J. I. Lee, S. H. Moon, Y. Urakawa, M. Uchino, Y. Kamioka
构建了一个从氙气中去除氪的高效蒸馏系统，并实现了Kr/Xe = $\sim 3 \times 10^{-12}$的纯度水平。这一发展对于促进高灵敏度低背景实验至关重要，例如在宇宙中寻找暗物质。
A high performance distillation system to remove krypton from xenon was constructed, and a purity level of Kr/Xe = $\sim 3 \times 10^{-12}$ was achieved. This development is crucial in facilitating high sensitivity low background experiments such as the search for dark matter in the universe.
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Krypton assay in xenon at the ppq level using a gas chromatographic system and mass spectrometer
我们已经开发出一种新的方法来测量氙中前所未有的低浓度氪痕量。这是许多不久的将来低本底粒子物理探测器的强制性任务。我们的系统使用低温气相色谱法从氙中分离氪。然后使用质谱仪定量氪的量。我们表明，该系统已达到8 ppq（每四次方份）的检测限，目前的结果与氪浓度低于1 ppt的蒸馏氙。
Detection of krypton in xenon for dark matter applications
我们扩展我们的技术，观察非常小的浓度的杂质在氙气氪检测的问题。我们使用传统的质谱仪来识别氙中的氪含量，但我们用液氮冷阱将设备的灵敏度提高了约五个数量级。我们发现氙的绝对氪浓度可以从质谱测量中推断出来，并且我们在低至0.5 × 10 ^{-12} mol/mol（Kr/Xe）的浓度下识别出氪信号。这种技术简化了在液态氙中进行WIMP暗物质搜索时对氪本底的监测。
In situ measurements of Krypton in Xenon gas with a quadrupole mass spectrometer following a cold-trap at a temporarily reduced pumping speed
本文提出了一种用冷阱和残余气体分析器测量氙中微量氪的新方法。该方法通过暂时降低抽气速度，同时消耗最少量的氙，从而提高了灵敏度。通过部分关闭测量室和分子泵之间的定制蝶阀，已达到40 ppt的灵敏度。该方法已在液化空气公司的超纯气体样品上进行了测试，该样品具有未知的固有氪浓度，产生$330 \pm 200$ ppt的氪浓度。
An efficient cryogenic distillation system was designed and constructed for PandaX-4T dark matter detector based on the McCabe-Thiele (M-T) method and the conservation of mass and energy. This distillation system is designed to reduce the concentration of krypton in commercial xenon from 5X$10^{-7}$ mol/mol to $10^{-14}$ mol/mol with 99% xenon collection efficiency at a maximum flow rate of 10 kg/h. The offline distillation operation has been completed and 5.75 tons of ultra-high purity xenon was produced, which is used as the detection medium in PandaX-4T detector. The krypton concentration o…
An online cryogenic distillation system for the removal of krypton and radon from xenon was designed and constructed for PandaX-4T, a highly sensitive dark matter detection experiment. The krypton content in a commercial xenon product is expected to be reduced by 7 orders of magnitude with 99% xenon collection efficiency at a flow rate of 10 kg/h by design. The same system can reduce radon content in xenon by reversed operation, with an expected radon reduction factor of about 1.8 in PandaX-4T under a flow rate of 56.5 kg/h. The commissioning of this system was completed, with krypton and rado…
Improved and automated krypton assay for low-background xenon detectors with Auto-RGMS
本研究开发了全自动稀有气体质谱仪系统 Auto-RGMS，通过改进色谱分离阶段和自动化操作，克服了传统手动 RGMS 的局限，实现了 ppq 级氪检测限，为下一代低背景氙探测器提供关键支持。
The XENON1T experiment aims for the direct detection of dark matter in a cryostat filled with 3.3 tons of liquid xenon. In order to achieve the desired sensitivity, the background induced by radioactive decays inside the detector has to be sufficiently low. One major contributor is the $β$-emitter $^{85}$Kr which is an intrinsic contamination of the xenon. For the XENON1T experiment a concentration of natural krypton in xenon $\rm{^{nat}}$Kr/Xe < 200 ppq (parts per quadrillion, 1 ppq = 10$^{-15}$ mol/mol) is required. In this work, the design of a novel cryogenic distillation column using the …
Measuring the abundance and isotopic composition of noble gases in planetary atmospheres can answer fundamental questions in cosmochemistry and comparative planetology. However, noble gases are rare elements, a feature making their measurement challenging even on Earth. Furthermore, in space applications, power consumption, volume and mass constraints on spacecraft instrument accommodations require the development of compact innovative instruments able to meet the engineering requirements of the mission while still meeting the science requirements. Here we demonstrate the ability of the quadru…
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 $(360 \pm 60)$ 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 fit to the data to describe the kr…
We discuss an in-situ evaluation of the $^{85}$Kr, $^{222}$Rn, and $^{220}$Rn background in PandaX-I, a 120-kg liquid xenon dark matter direct detection experiment. Combining with a simulation, their contributions to the low energy electron-recoil background in the dark matter search region are obtained.
The Large Underground Xenon (LUX) experiment operates at the Sanford Underground Research Facility to detect nuclear recoils from the hypothetical Weakly Interacting Massive Particles (WIMPs) on a liquid xenon target. Liquid xenon typically contains trace amounts of the noble radioactive isotopes $^{85}$Kr and $^{39}$Ar that are not removed by the in situ gas purification system. The decays of these isotopes at concentrations typical of research-grade xenon would be a dominant background for a WIMP search exmperiment. To remove these impurities from the liquid xenon, a chromatographic separati…
Krypton-85 is an anthropogenic beta-decaying isotope which produces low energy backgrounds in dark matter and neutrino experiments, especially those based upon liquid xenon. Several technologies have been developed to reduce the Kr concentration in such experiments. We propose to augment those separation technologies by first adding to the xenon an 85Kr-free sample of krypton in an amount much larger than the natural krypton that is already present. After the purification system reduces the total Kr concentration to the same level, the final 85Kr concentration will have been reduced even furth…
A simple high-sensitivity technique for purity analysis of xenon gas
我们报告的发展和性能的高灵敏度纯度分析技术的气态氙。使用UHV泄漏阀在宏观压力下从感兴趣的系统中对气体进行采样。用液氮冷阱除去样品中存在的氙，用标准真空质谱仪观察剩余的杂质。使用已知杂质水平的氙气校准样品，我们发现N2，O2和甲烷的最低可检测水平分别为1 ppb，160 ppt和60 ppt。与没有冷阱的情况下进行的测量相比，这表示约10，000倍的改进。
$\rm ^{83m}Kr$, with a short lifetime, is an ideal calibration source for liquid xenon or liquid argon detectors. The $\rm ^{83m}Kr$ isomer can be generated through the decay of $\rm ^{83} Rb$ isotope which is usually produced by proton beams bombarding natural krypton atoms. In this paper, we report a successful production of $\rm ^{83}Rb/^{83m}Kr$ with a proton beam energy of 3.4 MeV, and the first measurement of the production rate with such low energy proton beams. Another production attempt is performed using the newly available 20 MeV proton beam in China, and the measured production rat…
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 found a large difference between the removal efficiency obtained for the decay chains of $^{222}$Rn and $^{220}$Rn, respectively. This indicates that the plate-out mechanism …
nEXO is a proposed tonne-scale neutrinoless double beta decay ($0νββ$) experiment using liquid ${}^{136}Xe$ (LXe) in a Time Projection Chamber (TPC) to read out ionization and scintillation signals. Between the field cage and the LXe vessel, a layer of LXe ("skin" LXe) is present, where no ionization signal is collected. Only scintillation photons are detected, owing to the lack of optical barrier around the field cage. In this work, we show that the light originating in the skin LXe region can be used to improve background discrimination by 5% over previous published estimates. This improveme…
We describe a system to transport and identify barium ions produced in liquid xenon, as part of R&D towards the second phase of a double beta decay experiment, nEXO. The goal is to identify the Ba ion resulting from an extremely rare nuclear decay of the isotope $^{136}$Xe, hence providing a confirmation of the occurrence of the decay. This is achieved through Resonance Ionization Spectroscopy (RIS). In the test setup described here, Ba ions can be produced in liquid xenon or vacuum and collected on a clean substrate. This substrate is then removed to an analysis chamber under vacuum, where la…
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