Drift Paths Research Articles

Longitudinal Variations of Energetic Electrons Scattered by NWC Transmitter: DEMETER Observations

AbstractLow‐Earth orbit (LEO) satellites often observe wisp‐like energy spectra, characterized by lower energies at higher L values of energetic electrons, resulting from the scattering effect of the narrow‐band artificial transmitter signals. Typically, the flux levels of wisp energy spectra increase as they approach the South Atlantic Anomaly (SAA). Here, we report, for the first time, the longitudinal variations of wisp positions in the energy‐L coordinate based on observations from the DEMETER satellite. The L‐values of wisps decrease at the longitudes <180° and increase at the longitudes >180°. By considering the satellite's orbital characteristics, we found that the longitudinal variations of wisp are essentially the MLT‐dependent radial transport of electrons. This finding indicates that the electron drift paths can be modified within a single drift period. We propose a duskward convection electric field as a potential mechanism to explain the longitudinal variations of wisps. By assuming a uniform duskward convection electric field with an amplitude of ∼1.5 mV/m, our simulations can reasonably reproduce the longitudinal variations of wisps observed in the southern hemisphere on 21 March 2009. Our results support the existence of a convection electric field in the inner belt and suggest that this electric field significantly contributes to the variations in energies and L values of energetic electrons within one drift period.

Two-stage auxiliary drifting path tracking control for distributed driving three-axle commercial vehicles

When maneuvering corners at high speeds, commercial vehicles experience significant sideslip angles and tire force saturation, which can lead to severe traffic accidents. Incorporating intelligent driving technology to develop a controllable scheme that surpasses stability constraints and maintains the vehicle in a drift state is crucial for enhancing driving safety. Therefore, based on the model characteristics of distributed drive three-axle(DDTA) commercial vehicles, a two-stage auxiliary drift controller is proposed. In the auxiliary drift stage, time-varying model predictive control (MPC) is employed to track the desired states and achieve steady-state drift path tracking under extreme working conditions. A two-stage controller switching strategy is implemented based on road information. In the yaw stability control stage, an advanced auxiliary system facilitates cooperative control to smoothly restore tire attachment and vehicle yaw. Simulation results demonstrate that the control strategy ensures consistent path tracking performance even when adhesion of the middle and rear axle saturates and peak vehicle sideslip angle reaches 32.09°. After completing the drifting, vehicle yaw successfully returns to a stable state. Subsequently, miniaturized vehicle tests qualitatively analyze relevant conclusions by elucidating transient instability evolution in vehicles subjected to steering and distributed drive. The controllable stability boundary of the vehicle is thus expanded, thereby enhancing the engineering feasibility of drift technology.

Accurate Collisional Cross Section Measurement by Multipass Cyclic Ion Mobility Spectrometry.

Ion mobility-mass spectrometry (IM-MS) is a powerful analytical tool for structural characterization. IM measurement provides collision cross section (CCS) values that facilitate analyte identification. While CCS values can be directly calculated from mobility measurements obtained using drift tube ion mobility spectrometry (DT-IMS), this method has limited mobility resolution due to the practical constraints on the length of the ion drift path. Consequently, DT-IMS cannot differentiate analytes with similar mobilities or resolve fine mobility features of individual ions. Cyclic IMS (cIMS) instruments leverage a cyclic path enabled by traveling wave ion mobility (TWIM) technology and offer increased mobility solution to address this challenge. While TWIM devices must first be calibrated to enable CCS measurements, current calibration strategies are primarily tailored for single-pass analyses. This preference is partly attributed to the challenges associated with multipass calibration methods, which require both calibrants and analytes to experience the same number of passes. Achieving this consistency can be complicated due to factors like peak splitting and diffusion, and may not be feasible for online IM-MS analyses. A recent report employed average ion velocities obtained from multiple measurements under different separation pathlengths as a path length-independent metric for CCS calibration. However, the ability to exploit this averaging approach is limited by observed variation in ion drift time/velocity in these measurements. In this study, we introduce a novel calibration strategy designed for multipass cIMS analyses, directly targeting the root cause for the path length- and mobility-dependent variations in ion drift time. With this method, we demonstrate that CCS values derived from multipass measurements closely align with those obtained from single-pass analyses, with an average deviation of 0.1%. We apply this method to characterize four isomeric trisaccharides. Our approach not only results in excellent agreement between our measured cIMSCCS values and the reported DTCCS values, with an average difference of only 0.5%, but also allows us to effectively identify subtle mobility characteristics of each compound and determine their respective CCS values. This level of detail and accuracy was previously unattainable using DT-IMS or single-pass cIMS measurements. We developed an algorithm for reconstructing arrival time distribution in cases where wrap-around has resulted in peak splitting. Collectively, the new calibration strategy and the reconstruction procedure maintain reproducibility and precision in CCS measurements while largely eliminating the need for meticulous selection of separation times. We expect that our method will empower researchers to harness the high mobility resolution offered by multipass cIMS analyses without compromising the accuracy of CCS measurement, making it appropriate for straightforward use across a wide range of applications.

The Relationship Between Electron Precipitation and the Population of Trapped Electrons in LEO: New Evidence Supporting a Natural Limit to the Flux of Energetic Electrons

AbstractEnergetic particle precipitation into the atmosphere has been identified as a key loss process for electrons in the Earth's outer radiation belt region. However, direct measurements of the electron flux precipitating into the atmosphere are challenging from high altitude low inclination spacecraft, such as the Van Allen Probes, due to the small angular size of the loss cone along the orbital path of these high‐altitude spacecraft. Here we use data from the Polar Orbiting Environmental Satellites (POES)/Space Environment Monitor in low‐Earth orbit to assess the relationship between the trapped and precipitating electron flux in integral energy channels >30, >100, and >300 keV. Our results highlight that there is a strong non‐linear relationship between the flux of trapped and precipitating electrons, with the ratio of precipitating to trapped flux only becoming significantly enhanced once the trapped flux reaches a critical level. This transition from low to high levels of precipitation is consistent with the theory proposed by Kennel and Petschek (K‐P) (1966) https://doi.org/10.1029/JZ071i001p00001, whereby intense chorus waves are excited and trigger pitch angle diffusion, resulting in energetic particle precipitation and limiting the trapped flux. Using electron flux data from POES and chorus wave data from the Van Allen Probes, we further test the observations against predictions from the K‐P theory. A particle tracing model is also utilized to illustrate a direct link between the drift paths of injected electrons, the occurrence of chorus waves and the spatial distribution of strong electron precipitation into the atmosphere at different energies.

Proton and muon beam tests for ultra-fast MCP-PMT detectors

In collaboration with the North Night Vision Science and Technology (Nanjing) Research Institute Co. Ltd, researchers at the Institute of High Energy of Physics in China have successfully developed the 20-inch micro-channel-plate photomultiplier tube (MCP-PMT) that exhibits high detection efficiency (DE) for use in the Jiangmen Underground Neutrino Observatory (JUNO). Due to the long drift path of electrons from photocathode to MCP, the 20-inch MCP-PMT has a time resolution on the order of nanoseconds. Recently, the team has made advancements in ultra-fast MCP-PMTs (FPMTs), achieving picosecond-level time resolution with both 1-inch and 2-inch types. By now, prototypes featuring single-anode, 2 × 2 anodes, 4 × 4 anodes, and 8 × 8 anodes have been successfully manufactured and tested. The 8 × 8 anode FPMT, in particular, demonstrates a transit time spread (TTS) of 36 ps (Sigma) in single photon mode, thanks to its meticulously engineered structure. To assess the FPMT’s time performance under beam conditions, two beam tests were conducted at Fermi Lab and CERN. In these tests, the 8 × 8 pixel arrays of four distinct radiators, including LYSO, BGO, Pb glass and quartz glass, were paired with the 8 × 8 anodes FPMT. This setup involved the use of two radiator-coupled FPMT detectors for particle detection. The best coincidence time resolution recorded was 64 ps (Sigma) with a 120 GeV proton beam and 56 ps (Sigma) with a 108 GeV muon beam.

Tilted dust-acoustic waves in low-pressure DC complex plasma

This study utilized the ground-based Plasmakristall-4 experiment to investigate the characteristics of dust-acoustic waves in low-pressure neon plasma generated through a direct current discharge. The experimental observations revealed the presence of dust-acoustic waves exhibiting a distinctive screw-like wavefront structure. Interestingly, the phase speed of these waves was slightly higher than the theoretical predictions. This deviation can be attributed to the influence of external forces and boundary conditions, which introduce asymmetry to the system and result in the deformation of wave patterns. To gain further insight, a comprehensive three-dimensional particle drift path reconstruction was conducted, providing a clearer understanding of the observed phenomena and confirming the findings obtained through the experimental analysis.

Study on Optimizing the Communication Path of Hunan Sports Culture Based on the Information Diffusion Model

Abstract This paper takes the dissemination of Hunan sports culture as an example and analyzes its characteristics and development process in depth. By combining the continuous bag-of-words model and the Word2Vec model constructed by Skip-gram algorithm, this study determines the word vectors of the text data. It introduces the LDA theme model to reveal the implicit theme information in the document set. Based on this, a theme model of Hunan sports and cultural communication that mimics the spread of infectious diseases was constructed. By analyzing the information and comments collected from 2016 to 2020, this study identifies the theme keywords and explores the intensity change, sentiment tendency and drift path of different themes. The results showed that “spiritual and educational values” had the most remarkable combined intensity during the study period, with an average of 1.09, while “social values” increased over time, reaching a maximum intensity of 1.14 in 2020. A more pronounced negative sentiment characterized 2016-2018, 2018-2020 was marked by a more pronounced negative sentiment, and 2018-2020 by a more pronounced negative sentiment. Emotions were more significant, while positive and neutral emotions were more prominent in 2018-2020. Based on these findings, it is recommended to increase economic development and promote the spiritual connotation and educational value of Hunan sports culture through diversified communication to enhance the city’s soft power.

Differentiating Between Simultaneous Loss Drivers in Earth's Outer Radiation Belt: Multi‐Dimensional Phase Space Density Analysis

AbstractWe analyzed the contribution of electromagnetic ion cyclotron (EMIC) wave driven electron loss to a flux dropout event in September 2017. The evolution of electron phase space density (PSD) through the dropout showed the formation of a radially peaked PSD profile as electrons were lost at high L*, resembling distributions created by magnetopause shadowing. By comparing 2D Fokker Planck simulations of pitch angle diffusion to the observed change in PSD, we found that the μ and K of electron loss aligned with maximum scattering rates at dropout onset. We conclude that, during this dropout event, EMIC waves produced substantial electron loss. Because pitch angle diffusion occurred on closed drift paths near the last closed drift shell, no radial PSD minimum was observed. Therefore, the radial PSD gradients resembled solely magnetopause shadowing loss, even though the local pitch angle scattering produced electron losses of several orders of magnitude of the PSD.

Remote Sensing Monitoring of Green Tide Disaster Using MODIS and GF-1 Data: A Case Study in the Yellow Sea

Satellites with low-to-medium spatial resolution face challenges in monitoring the early and receding stages of green tides, while those with high spatial resolution tend to reduce the monitoring frequency of such phenomena. This study aimed to observe the emergence, evolution, and migratory patterns of green tides. We integrated GF-1 and MODIS imagery to collaboratively monitor the green tide disaster in the Yellow Sea during 2021. Initially, a linear regression model was employed to adjust the green tide coverage area as captured using MODIS imagery. We jointly observed the distribution range, drift path, and coverage area of the green tide and analyzed the drift path in coordination with offshore wind field and flow field data. Furthermore, we investigated the influence of SST, SSS, and rainfall on the 2021 green tide outbreak. The correlations calculated between SST, SSS, and precipitation with the changes in the area of the green tide were 0.43, 0.76, and 0.48, respectively. Our findings indicate that the large-scale green tide outbreak in 2021 may be associated with several factors. An increase in SST and SSS during the initial phase of the green tide established the essential conditions, while substantial rainfall during its developmental stage provided favorable conditions. Notably, the SSS exhibited a close association with the outbreak of the green tide.

Distribution and Evolution of Chorus Waves Modeled by a Neural Network: The Importance of Imbalanced Regression

AbstractWhistler‐mode chorus waves play an essential role in the acceleration and loss of energetic electrons in the Earth’s inner magnetosphere, with the more intense waves producing the most dramatic effects. However, it is challenging to predict the amplitude of strong chorus waves due to the imbalanced nature of the data set, that is, there are many more non‐chorus data points than strong chorus waves. Thus, traditional models usually underestimate chorus wave amplitudes significantly during active times. Using an imbalanced regressive (IR) method, we develop a neural network model of lower‐band (LB) chorus waves using 7‐year observations from the EMFISIS instrument onboard Van Allen Probes. The feature selection process suggests that the auroral electrojet index alone captures most of the variations of chorus waves. The large amplitude of strong chorus waves can be predicted for the first time. Furthermore, our model shows that the equatorial LB chorus’s spatiotemporal evolution is similar to the drift path of substorm‐injected electrons. We also show that the chorus waves have a peak amplitude at the equator in the source MLT near midnight, but toward noon, there is a local minimum in amplitude at the equator with two off‐equator amplitude peaks in both hemispheres, likely caused by the bifurcated drift paths of substorm injections on the dayside. The IR‐based chorus model will improve radiation belt prediction by providing chorus wave distributions, especially storm‐time strong chorus. Since data imbalance is ubiquitous and inherent in space physics and other physical systems, imbalanced regressive methods deserve more attention in space physics.

A Stable Isotope Sclerochronology‐Based Forensic Method for Reconstructing Debris Drift Paths With Application to the MH370 Crash

AbstractA flaperon belonging to Malaysian Airlines flight MH370 washed ashore on Réunion Island covered with the barnacle Lepas anatifera in July 2015, more than a year after the plane's disappearance. Here, we report the first high‐precision δ18Ocalcite versus temperature relationship for L. anatifera reared under laboratory conditions to unlock clues to the flaperon's drift path and origin. Using this experimental relationship and known growth rates for L. anatifera, we also demonstrate a new method for (a) converting δ18O data for one of the MH370 barnacles into a dated time series of sea surface temperatures (SSTs) experienced during the last part of the flaperon's drift and (b) identifying best fits between the observed flaperon SST time series and 50,000 SST histories generated from a particle‐tracking simulation. Our new method identifies a flaperon drift path far south of a previous isotope‐based reconstruction. We conclude with specific recommendations for using our method to continue the search for MH370 and other applications.

Simulation Analysis of the Dispersion of Typical Marine Pollutants by Fusion of Multiple Processes

The rapid development of coastal economies has aggravated the problem of pollution in the coastal water bodies of various countries. Numerous incidents of massive-scale marine life deaths have been reported because of the excessive discharge of industrial and agricultural wastewater. To investigate the diffusion of typical pollutants after discharge, in this study, a multi-process fusion simulation analysis model of pollutants under the action of ocean currents was established based on the concentration analysis method. Furthermore, key technologies involved, such as the parameter value, data selection, and visualization, were investigated. The iterative analysis and programming realization of three independent sub-processes, such as pollutant diffusion and transport, and the drift path and concentration distribution of pollutants after their discharge into the sea, were visualized. The case study revealed that the increase in the concentration of pollutants in the ocean was affected by the diffusion sub-process, and the transport sub-process plays a critical role in the long-distance transport of pollutants. The proposed method can provide technical support for marine environmental risk assessment and dynamic tracking of marine pollutants.

Quantitative estimates of oil-seepage rates from satellite imagery with implications for oil generation and migration rates

A new approach to quantifying oil fluxes from natural seafloor seepage sites based on the dynamic characteristics of floating oil slicks is presented. It enables rapid analysis of interpreted satellite imagery and permits large datasets to be analyzed. The method uses the drift path of the oil on water surface, termed the “centerline” of the slick, along with average current and wind speeds to estimate the age of seepage slicks. The results of the CL (centerline) method compare favorably with the hindcast modeling approach which requires time-resolved analysis of wind and current for each slick. The CL method yields an average flux estimate within the range of the flux documented by on-bottom capture for a seafloor oil pollution source. A survey of published flux estimates using a variety of techniques reveals a wide range with on-bottom estimates (0.08–12 ml/s) generally lower than estimates from slicks (1.6–125 ml/s). Determination of fluxes from three seepage sites in the Gulf of Mexico (GC600, Bush Hill, and TYK) reveals a wide range in seepage rates from 2.4 to 52.9 ml/s and flux distributions. Comparison of the observed fluxes from seeps with potential fluxes from a source region can be used to constrain source rock parameters (e.g., thickness, richness, area) and to understand the cumulative oil supply represented by seeps over geologic time scales.

Monitoring the Spatio-Temporal Distribution of Ulva prolifera in the Yellow Sea (2020–2022) Based on Satellite Remote Sensing

The green tide caused by Ulva prolifera (U. prolifera) is becoming more severe as climate change and human activity accelerate, endangering tourism, aquaculture, and urban landscapes in coastal cities. In order to understand the spatio-temporal distribution of U. prolifera in response to the green tide disaster, this study used the Haiyang-1C (HY-1C) satellite accompanied by the Sentinel-2 and GaoFen-1 (GF-1) satellites to systematically monitor U. prolifera between 2020 and 2022. The consistency of U. prolifera distribution between the HY-1C and Sentinel-2 satellites, as well as the HY-1C and GF-1 satellites, was first investigated and the determination coefficients (R2) were 0.966 and 0.991, respectively, which supports the feasibility of China’s first ocean water color operational satellite, HY-1C, for U. prolifera monitoring. Therefore, the spatio-temporal distribution of U. prolifera is studied herein, along with the influence range, influence area, and drift paths. From 2020 to 2022, U. prolifera appeared in late May and lasted for 61, 88, and 73 days. Additionally, the in influence area continuously decreased in 2020 and 2022, while it generally increased and then decreased in 2021. It is an interesting phenomenon that when the maximum influence area occurred at the early stage of U. prolifera in both 2020 and 2022, the drift paths tended to move southward after traveling northward. The overall trend of the drift path in 2021 was to head northward. Thus, the study of the dynamic evolution, influence range, influence area, and drift paths of U. prolifera is helpful to promote the systematic development of emergency response mechanisms for U. prolifera.

Extreme separations of bottle posts in the southern Baltic Sea – tentative interpretation of an experiment-of-opportunity

During an experiment-of-opportunity in July 2019, 27 drift bottles were released in the southern Baltic Sea. Ten of these bottles were found and reported at locations that were surprisingly widespread. In this study, we explore the chances to reproduce these findings with a numerical drift model. While trajectories may be considered as completely deterministic, in practice their prediction as well as reconstruction has a strong stochastic component, because of ubiquitous gradients on even the smallest scales. We illustrate different aspects of uncertainty including specification of leeway, random dispersion, and stretching along Lagrangian coherent structures. By and large, the results of numerical ensemble simulations seem to be in reasonable agreement with the observational evidence available. Some drift bottle findings suggest a bias in simulations, but without knowing the drift bottles’ full drift paths, a basis for more detailed model tuning is missing.

Energetic Electron and Proton Interactions with Pc5 Ultra Low Frequency (ULF) Waves during the Great Geomagnetic Storm of 15–16 July 2000

The dynamics of the outer zone radiation belt has received a lot of attention mainly due to the correlation between the occurrence of enhancing relativistic electron flux and spacecraft operation anomalies or even failures (e.g., Baker et al. 1994). Relativistic electron events are often observed during great storms associated with ultra low frequency (ULF) waves. For example, a large buildup of relativistic electrons was observed during the great storm of March 24, 1991 (e.g., Li et al. 1993; Hudson et al. 1995; Mann et al. 2013). However, the dominant processes which accelerate magnetospheric radiation belt electrons to MeV energies are not well understood. In this paper, we present observations of Pc5 ULF waves in the recovery phase of the Bastille day storm of July 16, 2000 and electron and proton flux simultaneously oscillating with the same frequencies as the waves. The mechanism for the observed electron and proton flux modulations is examined using groundbased and satellite observations. During this storm time, multiple packets of discrete frequency Pc5 ULF waves appeared associated with energetic particle flux oscillations. We model the drift paths of electrons and protons to determine if the particles drift through the ULF wave to understand why some particle fluxes are modulated by the ULF waves and others are not. We also analyze the flux oscillations of electrons and protons as a function of energy to determine if the particle modulations are caused by a ULF wave drift resonance or advection of a particle density gradient. We suggest that the energetic electron and proton modulations by Pc5 ULF waves provide further evidence in support of the important role that ULF waves play in outer radiation belt dyanamics during storm times.

Ocean kinetic energy and photosynthetic biomass are important drivers of planktonic foraminifera diversity in the Atlantic Ocean

To assess the anthropogenic effect on biodiversity, it is essential to understand the global diversity distribution of the major groups at the base of the food chain, ideally before global warming initiation (1850 Common Era CE). Since organisms in the plankton are highly interconnected and carbonate synthesizing species have a good preservation state in the Atlantic Ocean, the diversity distribution pattern of planktonic foraminifera from 1741 core-top surface sediment samples (expanded ForCenS database) provides a case study to comprehend centennial to decadal time-averaged diversity patterns at pre-1970 CE times, the tempo of the substantial increase in tropospheric warming. In this work, it is hypothesized and tested for the first time, that the large-scale diversity patterns of foraminifera communities are determined by sea surface temperature (SST, representing energy), Chl-a (a surrogate for photosynthetic biomass), and ocean kinetic energy (as EKE). Alpha diversity was estimated using species richness (S), Shannon Wiener index (H), and Simpson evenness (E), and mapped using geostatistical approaches. The three indices are significantly related to SST, Chl-a, and EKE (71-88% of the deviance in the generalized additive mixed model, including a spatial component). Beta diversity was studied through species turnover using gradient forest analysis (59% of the variation). The primary community thresholds of foraminifera species turnover were associated with 5-10 °C and 22-28 °C SST, 0.05-0.15 mg m-3 Chl-a, and 1.2-2.0 cm2 s-2 log10 EKE energy, respectively. Six of the most important foraminifera species identified for the environmental thresholds of beta diversity are also fundamental in transfer functions, further reinforcing the approaches used. The geographic location of the transition between the four main biogeographic zones was redefined based on the results of beta diversity analysis and incorporating the new datasets, identifying the major marine latitudinal gradients, the most important upwelling areas (Benguela Current, Canary Current), the Equatorial divergence, and the subtropical fronts (Gulf Stream-North Atlantic Drift path in the north, and the South Atlantic current in the south). In conclusion, we provide statistical proof that energy (SST), food supply (Chl-a), and currents (EKE) are the main environmental drivers shaping planktonic foraminifera diversity in the Atlantic ocean and define the associated thresholds for species change on those variables.

Typical and anomalous pathways of surface-floating material in the Northern North Atlantic and Arctic Ocean

Surface waters of the oceans carry large amounts of material, including sediment grains, plankton organisms, and ice crystals, as well as pollutants, e.g., oil and plastic. Transport and spatio-temporal distribution of this material depend on its properties and on the dynamical processes in the ocean mixed layer—currents, waves, turbulence, and convective mixing—acting at a wide range of scales. Due to its importance for marine physics, biogeochemistry and ecology, substantial research efforts have been invested in recent years in observations and modelling of ocean material transport, especially in the context of marine plastic pollution. Nevertheless, many important questions remain unanswered. In this work, numerically simulated trajectories of surface-floating particles in the period 1993–2020 are used to analyse typical and anomalous transport pathways in the northern North Atlantic and the Arctic Ocean. Model validation is performed based on additional simulations of 387 buoy tracks from the International Arctic Buoy Programme in the years 2014–2020. The trajectories are computed based on surface currents from a hydrodynamic model and Stokes drift from a spectral wave model. It is shown that due to high amplitudes of Stokes drift (comparable with wind-induced currents in ice-free parts of the domain of study), combined with high directional variability, the drifting paths are substantially modified in ice-free regions, underlying the important role of wave-induced currents in surface material transport. A statistical analysis of sim 1.6, 10^8 trajectories reveals patterns of connections between nearshore locations in the domain of study, the associated drift times and path sinuosity. Seasonal variability of transport, which differs between the Arctic Ocean and the North Atlantic, is found for typical transport routes following the larger-scale circulation patterns. Crucially, in both sub-domains episodic, but very strong transport events between otherwise isolated locations occur, associated with anomalous atmospheric circulation and, arguably, providing ‘windows of opportunity’ for dispersal of various organisms to new locations. It is shown for two examples in the North Atlantic region that an unusual combination of atmospheric circulation indices explains the anomalous transport, thus providing a predictive tool for future events. In the Arctic, analogous phenomena are modified by the state of the sea ice cover.

Liquid-phase purification for multi-tonne xenon detectors

As liquid xenon detectors grow in scale, novel techniques are required to maintain sufficient purity for charges to survive across longer drift paths. The Xeclipse facility at Columbia University was built to test the removal of electronegative impurities through cryogenic filtration powered by a liquid xenon pump, enabling a far higher mass flow rate than gas-phase purification through heated getters. In this paper, we present results from Xeclipse, including measured oxygen removal rates for two sorbent materials, which were used to guide the design and commissioning of the XENONnT liquid purification system. Thanks to this innovation, XENONnT has achieved an electron lifetime greater than {10},hbox {ms} in an sim {8.6}{text {tonne}} total mass, perhaps the highest purity ever measured liquid xenon detector.

The Effects of Different Anode Positions on the Electrical Properties of Square-Silicon Drift Detector.

The Silicon Drift Detector (SDD) with square structure is often used in pixel-type SDD arrays to reduce the dead region considerably and to improve the detector performance significantly. Usually, the anode is located in the center of the active region of the SDD with square structure (square-SDD), but the different anode positions in the square-SDD active area are also allowed. In order to explore the effect on device performance when the anode is located at different positions in the square-SDD active region, we designed two different types of square-SDD in this work, where the anode is located either in the center (SDD-1) or at the edge (SDD-2) of its active region. The simulation results of current density and potential distribution show that SDD-1 and SDD-2 have both formed a good electron drift path to make the anode collect electrons. The experimental results of device performance at the temperature range from −60 °C to 60 °C show that the anode current of the two fabricated SDDs both decreased with the decrease of temperature, but their voltage divider characteristics exhibited high stability resistance value and low temperature coefficient, thereby indicating that they could both provide corresponding continuous and uniform electric field at different temperatures. Finally, SDD-1 and SDD-2 have energy resolutions of 248 and 257 eV corresponding to the 5.9 keV photon peak of the Fe-55 radioactive source, respectively. Our experimental results demonstrate that there is no significant impact on the device performance irrespective of the anode positions in the square-SDD devices.