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A simulation study on spatial and time resolution for a cost-effective positron emission particle tracking system

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Particuology 2024年第5期88卷 312-322页

作者： Josephine Oppotsch Matthias Steinke Miriam fritsch fritz-Herbert Heinsius Thomas Held Nikoline Hilse Viktor Scherer Ulrich Wiedner ruhr-Universität Bochum Institut für Experimentalphysik I44801 BochumGermany ruhr-Universität Bochum Lehrstuhl für Energieanlagen und Energieprozesstechnik44801 BochumGermany

This work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPT).Since medical positron emission tomography (PET) scanners commonly used for PEPT are very expensive,a PET-like detector system based on cost-effective organic plastic scintillator bars is being developed and tested for its *** this context,the spatial resolution of a resting positron source,a source moving on a freely designed model path,and a particle motion given by a discrete element method (DEM) simulation is studied using Monte Carlo simulations and the software toolkit *** not only extended the simulation and reconstruction to a moving source but also significantly improved the spatial resolution compared to previous work by adding oversampling and iteration to the reconstruction ***,in the case of a source following a trajectory developed from DEM simulations,a very good resolution of about 1 mm in all three directions and an average 3D deviation between simulated and reconstructed events of 2.3 mm could be ***,the resolution for realistic particle motion within the generic grate system (which is the test rig for further experimental studies) is well below the smallest particle *** simulation of the dependence of the reconstruction accuracy on tracer particle location revealed a nearly constant efficiency within the entire detector system,which demonstrates that boundary effects can be neglected.

关键词： Positron emission particle tracking Monte Carlo method Time-of-flight Plastic scintillators Silicon photomultipliers(SiPMs)

A simulation study for a cost-effective PET-like detector system intended to track particles in granular assemblies

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Particuology 2024年第1期84卷 117-125页

作者： Josephine Oppotsch Antonios Athanassiadis Miriam fritsch fritz-Herbert Heinsius Thomas Held Nikoline Hilse Viktor Scherer Matthias Steinke Ulrich Wiedner ruhr-Universität Bochum Institut für Experimentalphysik I44801 BochumGermany ruhr-Universität Bochum Lehrstuhl für Energieanlagen und Energieprozesstechnik44801 BochumGermany

Since many industrial applications rely on the processing of densely packed and moving granular ma-terial,obtaining bulk internal information on the particle movement inside the reactors is of great *** information can be delivered by Positron Emission Particle Tracking(PEPT).By marking pellets with a positron-emitting radioisotope,the position of these tracer particles can be determined via the time-of-flight differences of the emitted gamma-ray *** current paper proposes a PET-like detector system based on cost-effective organic plastic scintillators instead of the more common but expensive inorganic *** system is currently under construction and was tested for its resolution and efficiency in this simulation *** Monte Carlo simulations and the software toolkit Geant4,three different geometries(an empty glass box,a generic grate system,and a cubic box of 1 m3 completely filled with pellets)were investigated,leading to a spatial resolution in the millimeter range and an efficiency,defined as the ratio of reconstructed decay locations to simulated decays,of 2.7%,1.4%,and 0.3%.

关键词： Positron emission particle tracking Geant4 Monte Carlo method Time-of-flight Plastic scintillators Silicon photomultipliers(SiPMs)

Impact of T_(i)/T_(e )ratio on ion transport based on EAST H-mode plasmas

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Plasma Science and Technology 2024年第4期26卷 68-78页

作者：刘建文臧庆梁云峰陈佳乐邬潇河 Alexander KNIEPS 扈嘉辉金仡飞张斌储宇奇刘海庆吕波段艳敏李妙辉陈颖杰龚先祖 the EAST Team institute of Plasma Physics Chinese Academy of SciencesHefei 230031People’s Republic of China University of Science and Technology of China Hefei 230026People’s Republic of China forschungszentrum Jülich GmbH Institut für Energie-und Klimaforschung-PlasmaphysikPartner of the Trilateral Euregio Cluster(TEC)Jülich 52425Germany

At the EAST tokamak, the ion temperature(T_(i)) is observed to be clamped around 1.25 keV in electron cyclotron resonance(ECr)-heated plasmas, even at core electron temperatures up to 10 keV(depending on the ECr heating power and the plasma density). This clamping results from the lack of direct ion heating and high levels of turbulence-driven transport. Turbulent transport analysis shows that trapped electron mode and electron temperature gradient-driven modes are the most unstable modes in the core of ECr-heated H-mode plasmas. Nevertheless, recently it was found that the T_(i)/T_(e)ratio can increase further with the fraction of the neutral beam injection(NBI) power, which leads to a higher core ion temperature(Ti0). In NBI heating-dominant H-mode plasmas, the ion temperature gradient-driven modes become the most unstable ***, a strong and broad internal transport barrier(ITB) can form at the plasma core in high-power NBI-heated H-mode plasmas when the T_(i)/T_(e)ratio approaches ~1, which results in steep core Teand Tiprofiles, as well as a peaked neprofile. Power balance analysis shows a weaker Teprofile stiffness after the formation of ITBs in the core plasma region, where Ticlamping is broken,and the core Tican increase further above 2 keV, which is 80% higher than the value of Ticlamping in ECr-heated plasmas. This finding proposes a possible solution to the problem of Ticlamping on EAST and demonstrates an advanced operational regime with the formation of a strong and broad ITB for future fusion plasmas dominated by electron heating.

关键词： ion temperature clamping transport neutral beam injection stiffness internal transport barrier

Improved training framework in a neural network model for disruption prediction and its application on EXL-50

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Plasma Science and Technology 2024年第5期26卷 29-39页

作者：蔡剑青梁云峰 Alexander KNIEPS 齐东凯王二辉向皓明廖亮黄杰阳杰黄佳刘建文 Philipp DrEWS 徐帅顾翔高轶琛罗宇李直 the EXL-50 Team institute of Plasma Physics Chinese Academy of SciencesHefei 230031People’s Republic of China forschungszentrum Jülich GmbH Institut für Energie-und Klimaforschung-PlasmaphysikPartner of the Trilateral Cluster(TEC)Jülich 52425Germany ENN Science and Technology Development Co. LtdLangfang 065001People’s Republic of China

A neural network model with a classical annotation method has been used on the EXL-50tokamak to predict impending ***,the results revealed issues of overfitting and overconfidence in predictions caused by inaccurate *** mitigate these issues,an improved training framework has been *** this approach,soft labels from previous training serve as teachers to supervise the further learning process;this has lead to a significant improvement in predictive model ***,this enhancement is primarily attributed to the coupling effect of the soft labels and correction *** improved training framework introduces an instance-specific label smoothing method,which reflects a more nuanced model assessment on the likelihood of a *** presents a possible solution to effectively address the challenges associated with accurate labeling across different machines.

关键词： neural network disruption soft label EXL-50 tokamak

Photoelectrochemical Iron-Catalyzed C(sp^(3))-H Borylation of Alkanes in a Position-Selective Manner

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CCS Chemistry 2024年第6期6卷 1430-1438页

作者： Wen Wei Bin Wang Simon L.Homölle Jinbin Zhu Yanjun Li Tristan von Münchow Isaac Maksso Lutz Ackermann institut für Organische und Biomolekulare Chemie Georg-August-Universität Göttingen37077 Göttingen

Catalytic C-H borylation is of prime topical importance,since easily available feedstock chemicals can thereby be transformed into valuable transient functional groups in the absence of directing ***,we disclose an iron-catalyzed C(sp^(3))-H borylation of simple,non-prefunctionalized alkanes,providing access to value-added products in a single step by means of *** power of merging photo-and electrochemistry was mirrored by ample scope and exceedingly mild reaction ***,an outstanding position-selectivity in favor of primary C(sp^(3))-H proved viable within the photoelectrochemical borylation through a chemo-selective anodic overoxidation *** ferro-photoelectrochemistry strategy avoids toxic precious transition metals,enabling C(sp^(3))-H borylations in a site-selective fashion.

关键词： photoelectrocatalysis C(sp^(3))-H borylation iron catalysis position-selectivity chlorine radical

Characteristics of the SOL ion-to-electron temperature ratio on the J-TEXT tokamak with different plasma configurations

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Plasma Science and Technology 2024年第2期26卷 13-21页

作者：李存凯梁云峰江中和周松华建坤阳杰杨庆虎 Alexander KNIEPS Philipp DrEWS 徐鑫毛飞越谢伟杨雨桐郭金龙李杨波任正康陈志鹏王能超 the J-TEXT Team International Joint research Laboratory of Magnetic Confinement fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and TechnologySchool of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074People's Republic of China forschungszentrum Jülich GmbH Institut für Energie-und Klimaforschung—PlasmaphysikPartner of the Trilateral Euregio Cluster(TEC)Julich 52425Germany 不详

Accurate measurement of the average plasma parameters in the edge region,including the temperature and density of electrons and ions,is critical for understanding the characteristics of the scrape-off layer(SOL) and divertor plasma transport in magnetically confined fusion *** the J-TEXT tokamak,a multi-channel retarding field analyzer(rfA) probe has been developed to study average plasma parameters in the edge region under various poloidal divertor and island divertor *** edge radial profile of the ion-to-electron temperature ratio,τ_(i/e),has been determined,which gradually decreases as the SOL ion self-collisionality,v_(SOL)*,*** is broadly consistent with what has been observed previously from various tokamak ***,the comparison of experimental results under different configurations shows that in the poloidal divertor configuration,even under the same v_(SOL)*,τ_(i/e) in the SOL region becomes smaller as the distance from the X-point to the target plate *** the island divertor configuration,τ_(i/e) near the O-point is higher than that near the X-point at the same v_(SOL)*,and both are higher than those in the limiter *** results suggest that the magnetic configuration plays a critical role in the energy distributions between electrons and ions at the plasma boundary.

关键词： ion temperature island divertor poloidal divertor retarding field analyzer(rfA)probe

Synchronized off-harmonic probe laser with highly variable pulse duration for laser-plasma interaction experiments

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High Power laser Science and Engineering 2024年第1期12卷 99-107页

作者： J.Hornung Y.Zobus H.Lorenté C.Brabetz B.Zielbauer V.Bagnoud GSI Helmholtzzentrum für Schwerionenforschung GmbH DarmstadtGermany institut d’Optique UniversitéParis-SaclayPalaiseauFrance institut für Angewandte Physik Technische Universität DarmstadtDarmstadtGermany

This paper presents the development and experimental utilization of a synchronized off-harmonic laser system designed as a probe for ultra-intense laser±plasma interaction experiments. The system exhibits a novel seed-generation design,allowing for a variable pulse duration spanning over more than three orders of magnitude, from 3.45 picoseconds to 10 nanoseconds. This makes it suitable for various plasma diagnostics and visualization techniques. In a side-view configuration, the laser was employed for interferometry and streaked shadowgraphy of a laser-induced plasma while successfully suppressing the self-emission background of the laser±plasma interaction, resulting in a signal-to-self-emission ratio of 110 for this setup. These properties enable the probe to yield valuable insights into the plasma dynamics and interactions at the PHELIX facility and to be deployed at various laser facilities due to its easy-to-implement design.

关键词： interferometry laser-plasma interaction off-harmonic probe laser streaked shadowgraphy

Clustering of voltage-gated ion channels as an evolutionary trigger of myelin formation

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Neural regeneration research 2024年第8期19卷 1631-1632页

作者： Henrike Ohm Simone rey Christian Klambt institut fur Neuro-und Verhaltensbiologie MunsterGermany

Neurons carry apical dendrites that perceive information and a basal axon that transmits the computed information towards its to *** axon originates at the axon hillock which is followed by the axon initial ***,action potentials are initiated that are based on millisecond long openings of specific voltagegated sodium and potassium channels that are conserved in all parahoxozoa(Placozoa,Cnidaria,Bilateria)(Li et al.,2015).

关键词： initiated carry potassium

Energy enhancement of laser-driven ions by radiation reaction and Breit-Wheeler pair production in the ultra-relativistic transparency regime

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High Power laser Science and Engineering 2024年第1期12卷 60-73页

作者： Shikha Bhadoria Mattias Marklund Christoph H.Keitel Max-Planck-institut für Kernphysik HeidelbergGermany Department of Physics University of GothenburgGöteborgSweden

The impact of radiation reaction and Breit±Wheeler pair production on the acceleration of fully ionized carbon ions driven by an intense linearly polarized laser pulse has been investigated in the ultra-relativistic transparency *** initial expectations, the radiation reaction and pair production at ultra-high laser intensities are found to enhance the energy gained by the ions. The electrons lose most of their transverse momentum, and the additionally produced pair plasma of Breit±Wheeler electrons and positrons co-streams in the forward direction as opposed to the existing electrons streaming at an angle above zero degree. We discuss how these observations could be explained by the changes in the phase velocity of the Buneman instability, which is known to aid ion acceleration in the breakout afterburner regime, by tapping the free energy in the relative electron and ion streams. We present evidence that these non-classical effects can further improve the highest carbon ion energies in this transparency regime.

关键词： ion acceleration quantum electrodynamic effects