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Manipulating Surface Termination of Perovskite Manganate for Oxygen Activation

ADVANCED FUNCTIONAL MATERIALS 2021年第14期31卷 2006439-2006439页

作者： Wang, Xiyang Li, Xinbo Chu, Xuefeng Cao, Rui Qian, Jingyu Cong, Yingge Huang, Keke Wang, Jiaao Redshaw, Carl Sarangi, Ritimukta Li, Guangshe Feng, Shouhua Jilin Univ Coll Chem State Key Lab Inorgan Synth & Preparat Chem Int Joint Res Lab Nanomicro Architecture Chem Changchun 130012 Peoples R China Jilin Jianzhu Univ Sch Elect & Elect Informat Engn Jilin Prov Key Lab Architectural Elect & Comprehe Changchun 130118 Peoples R China SLAC Natl Accelerator Lab Stanford Synchrotron Radiat Light Source Menlo Pk CA 94025 USA Univ Jinan Sch Mat Sci & Engn Jinan 250022 Peoples R China Univ Hull Dept Chem Plast Collaboratory Kingston Upon Hull HU6 7RX N Humberside England

For ABO(3) perovskite oxides, one of the key issues limiting their utilization in heterogeneous catalysis is the dominant presence of catalytically inactive A-site cations at the surface. The engineering of B-site terminated perovskites is considered as an effective method to address this issue, especially when dealing with Mn/Co-based perovskite catalysts. However, to date, such a strategy has not been fully successful and remains a major challenge in the field. Herein, a Mn-terminated La0.45Sr0.45MnO3 (B-LSM) is successfully synthesized via a one-pot hydrothermal method, in which low-valence Mn ions partially occupy the A site to form the active Mn-excess phase. Experimental results and theoretical calculations reveal that the presence of the surface Mn termination in B-LSM optimizes the hybrid orbitals of Mn 3d-O 2p and promotes the activation of surface lattice oxygen, where the pristine inert lattice O2- is evolved into active and stable lattice O-2-(x). Such structural optimization significantly reduces the activation energy barriers on going from O-2(-) species to important intermediate O- species during O-2 activation. Moreover, this results in good stability and Pt-like activity for the B-LSM during CO oxidation. This work offers a new chemical route for the design of advanced perovskite-type oxides possessing novel functions.

关键词： electron structure oxygen activation perovskite oxides surface active site surface segregation

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The CompactLight Design Study

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EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS 2024年第1期233卷 1-208页

作者： D'Auria, G. Adli, E. Aicheler, M. Aksoy, A. Alesini, D. Apsimon, R. Arnsberg, J. Auchettl, R. Bainbridge, A. Balazs, K. Bantekas, D. Bedolla, J. Behtouei, M. Bellaveglia, M. Vd Berg, M. Bernhard, A. Bignami, A. Breitenbach, M. Breukers, M. Burt, G. Cai, J. Calvi, M. Cardelli, F. Carpanese, M. Cortes, H. M. Castaneda Castilla, A. Cianchi, A. Clarke, J. Cowie, L. Croia, M. Cross, A. Danailov, M. Dattoli, G. Deleval, S. Mitri, S. Di Diomede, M. Dowd, R. Dunning, D. Easton, J. Fang, W. Fatehi, S. Faus-Golfe, A. Ferianis, M. Ferrario, M. Ficcadenti, L. Gallo, A. Gazis, E. Gazis, N. Geometrante, R. Gethmann, J. Gioppo, R. Giribono, A. Gonzalez-Iglesias, D. Goryashko, V. Grohmann, S. Gu, Q. Han, Y. Hinton, A. Hobi, A. Hoekstra, R. Huang, X. Jacewicz, M. Jones, J. Kaertner, F. Karagiannaki, A. Kokole, M. Kotitsa, R. Kotsopoulos, D. Krasch, B. Latina, A. Lepercq, P. Liu, X. Lucas, T. G. Luiten, O. J. Maheshwari, M. Mahnic, J. Mak, A. Marcos, J. Marin, E. Marinov, K. Martinez, B. G. Mercier, B. Migliorati, M. Milharcic, T. Mostacci, A. Mu Noz, R. Musat, V. Mutsaers, P. H. A. Nergiz, Z. Nguyen, F. Nix, L. Palumbo, L. Parodi, M. Pavlica, R. Pellegrino, L. Pereira, D. E. Perez, F. Petralia, A. Piersanti, L. Pockar, J. Pramatari, K. Priem, H. Primozic, U. Rassool, R. Reiche, S. Revilak, P. Richter, S. C. Rochow, R. Rossi, C. Salen, P. Schmidt, T. Schoerling, D. Schulte, D. Scifo, J. Sheehy, S. Shepherd, B. Spataro, B. Stapnes, S. Stragier, X. F. D. Syratchev, I. Tabacco, C. Tan, J. Tanke, E. Taylor, G. Telahi, I. Thompson, N. Trachanas, E. Tzanetou, K. S. Vaccarezza, C. Vainola, J. Vannozzi, A. Volpi, M. Wang, C. Williams, P. Wu, X. Wuensch, W. Yap, J. Zangrando, M. Zhang, K. Zhang, L. Zhao, Y. Zhao, Z. Zhu, D. Elettra Sincrotrone Trieste SCpA AREA Sci Pk I-34149 Trieste Italy CERN CH-1211 Geneva 23 Switzerland STFC Daresbury Lab ASTeC Keckwick Lane Warrington WA4 4AD England SciTech Daresbury Cockcroft Inst Warrington WA4 4AD England VDL ETG Precis NL-5652 Eindhoven North Brabant Netherlands ANSTO Australian Synchrotron Clayton Vic Australia ENEA CR Frascati Fus & Nucl Safety Dept Via E Fermi 45 I-00044 Rome Italy Univ Lancaster Dept Engn Lancaster LA1 4YR England Karlsruhe Inst Technol KIT Karlsruhe Germany Eindhoven Univ Technol TU E Eindhoven Netherlands INFN Lab Nazl Frascati Via E Fermi 54 I-00054 Rome Italy Univ Helsinki Helsinki Inst Phys Helsinki Finland Uppsala Univ Dept Phys & Astron FREIA Lab SE-75237 Uppsala Sweden Sapienza Univ Rome Rome Italy ALBA Synchrotron CELLS Barcelona Spain Univ Valencia Inst Fis Corpuscular IFIC CSIC Valencia Spain Shanghai Inst Appl Phys Shanghai Peoples R China Inst Accelerating Syst & Applicat IASA Dept Phys Athens Greece Univ Melbourne ARC Ctr Excellence Particle Phys Terascale Melbourne Vic Australia Ankara Univ Inst Accelerator Technol Ankara Turkiye Kyma SpA Area Sci Pk I-34149 Trieste Italy CNRS Lab Phys 2 infinis Irene Joliot Curie IJCLab F-91405 Orsay France Paul Scherrer Inst Forschungsstr 111 CH-5232 Villigen Switzerland Free Univ Amsterdam Boelelaan 1105 NL-1081 HV Amsterdam Netherlands Univ Strathclyde 16 Richmond St Glasgow G1 1XQ Scotland Tor Vergata Univ Rome Via Cracovia 50 I-00133 Rome Italy Bilfinger Noell GmbH Rotterdam Netherlands Kyma Tehnologija Doo Kraska ul 2 Sezana 6210 Slovenia Athens Univ Econ & Business 76 Patiss St Athens 10434 Greece Natl Tech Univ Athens Sch Architecture Patiss ComplexPatiss St 42 Athens Greece Univ Groningen NL-9747 AG Groningen Netherlands Adv Res Ctr Nanolithog ARCNL Sci Pk 106 NL-1098 XG Amsterdam Netherlands European Spallat Source ERIC ESS CampusPartikelgatan 2 S-22484 Lund Sweden Univ Oslo POB 1072 N-0316 Oslo Norway Ctr

CompactLight is a Design Study funded by the European Union under the Horizon 2020 research and innovation funding programme, with Grant Agreement No. 777431. CompactLight was conducted by an International Collaboration of 23 international laboratories and academic institutions, three private companies, and five third parties. The project, which started in January 2018 with a duration of 48 months, aimed to design an innovative, compact, and cost-effective hard X-ray FEL facility complemented by a soft X-ray source to pave the road for future compact accelerator-based facilities. The result is an accelerator that can be operated at up to 1 kHz pulse repetition rate, beyond today's state of the art, using the latest concepts for high brightness electron photoinjectors, very high gradient accelerating structures in X-band, and novel short-period undulators. In this report, we summarize the main deliverable of the project: the CompactLight Conceptual Design Report, which overviews the current status of the design and addresses the main technological challenges.

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Inductor Design Optimization Using FEA Supervised Machine Learning

Inductor Design Optimization Using FEA Supervised Machine Le...

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European Conference on Power Electronics and Applications

作者： D. Cajander I. Viarouge P. Viarouge D. Aguglia ENERGY Inst. Haute Ecole d'Ingénieurie et d’Architecture Fribourg HES-SO University of Applied Sciences and Arts Western Switzerland Boulevard de Pérolles 80 Fribourg Switzerland Electrical and Computer Eng. Dept. LEEPCI Lab. Laval University GIK 7P4 Quebec (QC) Canada ELECTROTECHNOLOGIES Selem Inc 2610 Rue Gérard-Lajoie GIP 3G1 Quebec (QC) Canada Accelerator Systems Dept. Electric Power Converter Group CERN - European Organization for Nuclear Research Geneva 23 Switzerland

ISBN: (数字)9789075815399

ISBN: (纸本)9781665487009

An optimal inductor design methodology using dimensioning models derived from Finite Element Analysis (FEA) supervised Artificial Neural Networks (ANN) is presented. The efficiency of such trained ANN dimensioning models in terms of compromise between precision and computing time is demonstrated for the cylindrical inductor topology with air and magnetic material core including saturation.

关键词： Training Analytical models Systematics Network topology Computational modeling Atmospheric modeling Artificial neural networks

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Wrpn & apprentice: Methods for training and inference using low-precision numerics

arXiv

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arXiv 2018年

作者： Mishra, Asit Marr, Debbie Accelerator Architecture Lab

Today's high-performance deep learning architectures involve large models with numerous parameters. Low-precision numerics has emerged as a popular technique to reduce both the compute and memory requirements of these large models. However, lowering precision often leads to accuracy degradation. We describe three software-based schemes whereby one can both train and do efficient inference using low-precision numerics without hurting accuracy. Finally, we describe an efficient hardware accelerator that can take advantage of the proposed low-precision numerics. Copyright © 2018, The Authors. All rights reserved.

关键词： Deep learning

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Determination of the ¹⁹³Ir(n, 2n) reaction cross section and correction methodology for the ¹⁹¹Ir(n, γ) contamination

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EUROPEAN PHYSICAL JOURNAL A 2019年第10期55卷 1-11页

作者： Kalamara, A. Patronis, N. Vlastou, R. Kokkoris, M. Chasapoglou, S. Stamatopoulos, A. Serris, M. Paneta, V. Axiotis, M. Lagoyannis, A. Harissopulos, S. Stamatelatos, I. E. Natl Tech Univ Athens Dept Phys Athens 15780 Greece Univ Ioannina Dept Phys GR-45110 Ioannina Greece Univ West Att Dept Naval Architecture Athens 12210 Greece Uppsala Univ Angstrom Lab Dept Phys & Astron Box 516 S-75120 Uppsala Sweden NCSR Demokritos Inst Nucl & Particle Phys Tandem Accelerator Lab Aghia Paraskevi 15310 Greece NCSR Demokritos Inst Nucl & Radiol Sci Energy Technol & Safety Aghia Paraskevi 15310 Greece

The cross section of the Ir-193(n, 2n)Ir-192 reaction has been determined by means of the activation technique, relative to the Al-27(n, alpha) and Au-197(n, 2n) reference reactions cross sections, at neutron beam energies ranging from 10 to 21 MeV. The quasi-monoenergetic neutron beams were produced at the 5.5 MV Tandem T11/25 accelerator laboratory of NCSR "Demokritos" via the H-2(d, n) and H-3(d, n) reactions. The induced gamma-ray activity of the irradiated target and reference foils was measured with high resolution HPGe detectors. In order to correct for the contribution of the Ir-191(n, gamma)Ir-192 reaction, which is open to low energy parasitic neutrons, a recently developed analysis method was implemented and it is presented in great detail. Furthermore, cross section theoretical calculations were carried out using the EMPIRE and TALYS codes over a wide energy range.

关键词： Germanium compounds

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Guest Editors' Introduction: Hardware accelerators for Data Centers

IEEE DESIGN & TEST

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IEEE DESIGN & TEST 2018年第1期35卷 5-6页

作者： Ozdal, Mustafa Nam, Gi-Joon Marr, Debbie Bilkent Univ Dept Comp Engn TR-06800 Ankara Turkey IBM Res Yorktown Hts NY USA Intel Corp Intel Labs Accelerator Architecture Lab Hillsboro OR 97124 USA

It is our pleasure to introduce this special issue on hardware accelerators for data centers. Data centers around the world have been expanding and multiplying rapidly in the last decade with increased internet use, online services, compute consolidation, and data analytics. Hardware accelerators are increasingly important architectural components in the context of data center customization to achieve high performance and lower energy. Prominent companies have introduced FPGA/GPU-based platforms for data centers. For example, IBM’s Coherent accelerator Processor Interface and Intel’s Quick-Assist accelerator Abstraction Layer enable the integration of CPUs and FPGAs/GPUs through coherent shared memory. Microsoft built the configurable cloud platform for data centers and demonstrated significant performance improvements for different workloads. In addition to FPGAs and GPUs, application-specific hardware accelerators are being integrated into platforms for widely used workloads such as compression, cryptography, and pattern matching. Google’s tensor processing unit is reported to be used to accelerate machine learning (ML) workloads at Google’s data centers.

关键词： Special issues and sections Hardware Data centers Data analysis Big Data Neural networks

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Tunable Van Hove Singularity without Structural Instability in Kagome Metal CsTi3Bi5

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Physical Review Letters 2023年第2期131卷 026701-026701页

作者： Bo Liu Min-Quan Kuang Yang Luo Yongkai Li Cheng Hu Jiarui Liu Qian Xiao Xiquan Zheng Linwei Huai Shuting Peng Zhiyuan Wei Jianchang Shen Bingqian Wang Yu Miao Xiupeng Sun Zhipeng Ou Shengtao Cui Zhe Sun Makoto Hashimoto Donghui Lu Chris Jozwiak Aaron Bostwick Eli Rotenberg Luca Moreschini Alessandra Lanzara Yao Wang Yingying Peng Yugui Yao Zhiwei Wang Junfeng He Department of Physics and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics University of Science and Technology of China Hefei Anhui 230026 China Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics and School of Physical Science and Technology Southwest University Chongqing 400715 China Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems Beijing Institute of Technology Beijing 100081 China Material Sciences Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Department of Physics and Astronomy Clemson University Clemson South Carolina 29631 USA International Center for Quantum Materials School of Physics Peking University Beijing 100871 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei Anhui 230026 China Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Menlo Park California 94025 USA Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA Department of Physics University of California Berkeley Berkeley California 94720 USA Material Science Center Yangtze Delta Region Academy of Beijing Institute of Technology Jiaxing 314011 China

In kagome metal CsV3Sb5, multiple intertwined orders are accompanied by both electronic and structural instabilities. These exotic orders have attracted much recent attention, but their origins remain elusive. The newly discovered CsTi3Bi5 is a Ti-based kagome metal to parallel CsV3Sb5. Here, we report angle-resolved photoemission experiments and first-principles calculations on pristine and Cs-doped CsTi3Bi5 samples. Our results reveal that the van Hove singularity (vHS) in CsTi3Bi5 can be tuned in a large energy range without structural instability, different from that in CsV3Sb5. As such, CsTi3Bi5 provides a complementary platform to disentangle and investigate the electronic instability with a tunable vHS in kagome metals.

关键词： van Hove singularity Kagome lattice Angle-resolved photoemission spectroscopy First-principles calculations

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Surface-termination-dependent electronic states in kagome superconductors AV3Sb5 (A=K, Rb, Cs) studied by micro-ARPES

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Physical Review B 2023年第24期107卷 245143-245143页

作者： Takemi Kato Yongkai Li Min Liu Kosuke Nakayama Zhiwei Wang Seigo Souma Miho Kitamura Koji Horiba Hiroshi Kumigashira Takashi Takahashi Yugui Yao Takafumi Sato Department of Physics Graduate School of Science Tohoku University Sendai 980-8578 Japan Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 People's Republic of China Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems Beijing Institute of Technology Beijing 100081 People's Republic of China Material Science Center Yangtze Delta Region Academy of Beijing Institute of Technology Jiaxing 314011 People's Republic of China College of Mathematics and Physics Beijing University of Chemical Technology Beijing 100029 People's Republic of China Precursory Research for Embryonic Science and Technology (PRESTO) Japan Science and Technology Agency (JST) Tokyo 102-0076 Japan Center for Science and Innovation in Spintronics (CSIS) Tohoku University Sendai 980-8577 Japan Advanced Institute for Materials Research (WPI-AIMR) Tohoku University Sendai 980-8577 Japan Institute of Materials Structure Science High Energy Accelerator Research Organization (KEK) Tsukuba Ibaraki 305-0801 Japan National Institutes for Quantum Science and Technology (QST) Sendai 980-8579 Japan Institute of Multidisciplinary Research for Advanced Materials (IMRAM) Tohoku University Sendai 980-8577 Japan International Center for Synchrotron Radiation Innovation Smart (SRIS) Tohoku University Sendai 980-8577 Japan Mathematical Science Center for Co-creative Society (MathCCS) Tohoku University Sendai 980-8578 Japan

Recently discovered kagome superconductors AV3Sb5 (A=K, Rb, Cs) exhibit exotic bulk and surface physical properties such as charge density wave (CDW) and chirality, whereas their origins remain unresolved. By using microfocused angle-resolved photoemission spectroscopy, we discovered that AV3Sb5 commonly exhibits two distinct polar surfaces depending on the termination: electron- and hole-doped ones for the A and Sb termination, respectively. We observed that the kagome-derived band shows a splitting in the A-terminated surface, while it is absent in the Sb-terminated counterpart, suggestive of a signature of the polarity-dependent CDW at the surface. Close comparison of the band-dependent splitting implies that the three-dimensional CDW structure of the K-terminated surface is different from that of the Rb- or Cs-terminated surface, suggesting the possible diversity of the CDW ground state. These results provide important insight into the origin of CDW in kagome superconductors AV3Sb5.

关键词： Charge density waves Electric polarization Electronic structure Surface & interfacial phenomena Kagome lattice Superconductors Angle-resolved photoemission spectroscopy

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Benchmarking the design of the cryogenics system for the underground argon in DarkSide-20k

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JOURNAL OF INSTRUMENTATION 2025年第2期20卷 P02016-P02016页

作者： Acerbi, F. Adhikari, P. Agnes, P. Ahmad, I. Albergo, S. Albuquerque, I. F. M. Alexander, T. Alton, A. K. Amaudruz, P. Angiolilli, M. Aprile, E. Ardito, R. Corona, M. Atzori Auty, D. J. Ave, M. Avetisov, I. C. Azzolini, O. Back, H. O. Balmforth, Z. Olmedo, A. Barrado Barrillon, P. Batignani, G. Bhowmick, P. Blua, S. Bocci, V. Bonivento, W. Bottino, B. Boulay, M. G. Buchowicz, A. Bussino, S. Busto, J. Cadeddu, M. Cadoni, M. Calabrese, R. Camillo, V. Caminata, A. Canci, N. Capra, A. Caravati, M. Cardenas-Montes, M. Cargioli, N. Carlini, M. Castellani, A. Castello, P. Cavalcante, P. Cebrian, S. Ruiz, J. Cela Chashin, S. Chepurnov, A. Cifarelli, L. Cintas, D. Citterio, M. Cleveland, B. Coadou, Y. Cocco, V. Colaiuda, D. Vilda, E. Conde Consiglio, L. Costa, B. S. Czubak, M. D'Aniello, M. D'Auria, S. Rolo, M. D. Da Rocha Darbo, G. Davini, S. De Cecco, S. De Guido, G. Dellacasa, G. Derbin, A. V. Devoto, A. Di Capua, F. Di Ludovico, A. Di Noto, L. Di Stefano, P. Dias, L. K. Mairena, D. Diaz Ding, X. Dionisi, C. Dolganov, G. Dordei, F. Dronik, V. Elersich, A. Ellingwood, E. Erjavec, T. Diaz, M. Fernandez Ficorella, A. Fiorillo, G. Franchini, P. Franco, D. Gatti, H. Frandini Frolov, E. Gabriele, F. Gahan, D. Galbiati, C. Galinski, G. Gallina, G. Gallus, G. Garbini, M. Abia, P. Garcia Gawdzik, A. Gendotti, A. Ghisi, A. Giovanetti, G. K. Casanueva, V. Goicoechea Gola, A. Grandi, L. Grauso, G. di Cortona, G. Grilli Grobov, A. Gromov, M. Guerzoni, M. Gulino, M. Guo, C. Hackett, B. R. Hallin, A. Hamer, A. Haranczyk, M. Harrop, B. Hessel, T. Hill, S. Horikawa, S. Hu, J. Hubaut, F. Hucker, J. Hugues, T. Hungerford, E. V. Ianni, A. Ippolito, V. Jamil, A. Jillings, C. Jois, S. Kachru, P. Keloth, R. Kemmerich, N. Kemp, A. Kendziora, C. L. Kimura, M. Kish, A. Kondo, K. Korga, G. Kotsiopoulou, L. Koulosousas, S. Kubankin, A. Kunze, P. Kuss, M. Kuzniak, M. Kuzwa, M. La Commara, M. Lai, M. Le Guirriec, E. Leason, E. Leoni, A. Lidey, L. Lissia, M. Luzzi, L. Lychagina, O. Macfadyen, O. Machulin, I. N. Manecki, S. Manthos, I. Mapelli, L. Mar Fdn Bruno Kessler I-38123 Povo Italy Carleton Univ Dept Phys Ottawa ON K1S 5B6 Canada Gran Sasso Sci Inst I-67100 Laquila Italy INFN Lab Nazl Gran Sasso I-67100 Assergi AQ Italy Polish Acad Sci AstroCeNT Nicolaus Copernicus Astron Ctr PL-00614 Warsaw Poland INFN Catania I-95121 Catania Italy Univ Catania I-95124 Catania Italy Univ Sao Paulo Inst Fis BR-05508090 Sao Paulo Brazil Pacific Northwest Natl Lab Richland WA 99352 USA Augustana Univ Dept Phys Sioux Falls SD 57197 USA TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada Columbia Univ Dept Phys New York NY 10027 USA Politecn Milan Civil & Environm Engn Dept I-20133 Milan Italy INFN Milano I-20133 Milan Italy INFN Cagliari I-09042 Cagliari Italy Univ Cagliari Dept Phys I-09042 Cagliari Italy Univ Alberta Dept Phys Edmonton AB T6G 2R3 Canada Mendeleev Univ Chem Technol Moscow 125047 Russia INFN Lab Nazl Legnaro I-35020 Padua Italy Savannah River Natl Lab Jackson SC 29831 USA Royal Holloway Univ London Dept Phys Egham TW20 0EX Surrey England CIEMAT Ctr Invest Energet Medioambient & Tecnol Madrid 28040 Spain Aix Marseille Univ Ctr Phys Particules Marseille CPPM CNRSIN2P3 Marseille France Univ Pisa Dept Phys I-56127 Pisa Italy INFN Pisa I-56127 Pisa Italy Univ Oxford Oxford OX1 2JD England INFN Torino I-10125 Turin Italy Politecn Torino Dept Elect & Commun I-10129 Turin Italy INFN Sez Roma I-00185 Rome Italy Univ Genoa Dept Phys I-16146 Genoa Italy INFN Genova I-16146 Genoa Italy Warsaw Univ Technol Inst Radioelect & Multimedia Technol PL-00661 Warsaw Poland INFN Roma Tre I-00146 Rome Italy Univ Roma Tre Dept Math & Phys I-00146 Rome Italy INFN Napoli I-80126 Naples Italy Virginia Tech Blacksburg VA 24061 USA Univ Cagliari Dept Elect & Elect Engn I-09123 Cagliari Italy Univ Zaragoza Ctr Astroparticulas & Fis Altas Energias Zaragoza 50009 Spain Lomonosov Moscow State Univ Skobeltsyn Inst Nucl Phys Moscow 119234 Russia Univ Bologna Dept Phys & Astron I-

DarkSide-20k (DS-20k) is a dark matter detection experiment under construction at the laboratori Nazionali del Gran Sasso (LNGS) in Italy. It utilises similar to 100 t of low radioactivity argon from an underground source (UAr) in its inner detector, with half serving as target in a dual-phase time projection chamber (TPC). The UAr cryogenics system must maintain stable thermodynamic conditions throughout the experiment's lifetime of over 10 years. Continuous removal of impurities and radon from the UAr is essential for maximising signal yield and mitigating background. We are developing an efficient and powerful cryogenics system with a gas purification loop with a target circulation rate of 1000 slpm. Central to its design is a condenser operated with liquid nitrogen which is paired with a gas heat exchanger cascade, delivering a combined cooling power of more than 8 kW. Here we present the design choices in view of the DS-20k requirements, in particular the condenser's working principle and the cooling control, and we show test results obtained with a dedicated benchmarking platform at CERN and LNGS. We find that the thermal efficiency of the recirculation loop, defined in terms of nitrogen consumption per argon flow rate, is 95% and the pressure in the test cryostat can be maintained within +/-(0.1-0.2) mbar. We further detail a 5-day cool-down procedure of the test cryostat, maintaining a cooling rate typically within -2K/h, as required for the DS-20k inner detector. Additionally, we assess the circuit's flow resistance, and the heat transfer capabilities of two heat exchanger geometries for argon phase change, used to provide gas for recirculation. We conclude by discussing how our findings influence the finalisation of the system design, including necessary modifications to meet requirements and ongoing testing activities.

关键词： Cryogenics Dark Matter detectors (WIMPs, axions, etc.) Noble liquid detectors (scintillation, ionization, double-phase) Time projection Chambers (TPC)

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Role of surface oxidation for thickness-driven insulator-to-metal transition in epitaxial MoO₂ films

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APPLIED SURFACE SCIENCE 2018年 459卷 92-97页

作者： Ahn, Eunyoung Min, Taewon Lee, Jaekwang Lee, Inwon Kim, Younghak Jeen, Hyoungjeen Pusan Natl Univ Dept Phys Busan 46241 South Korea Pusan Natl Univ Extreme Phys Inst Busan 46241 South Korea Pusan Natl Univ Dept Naval Architecture & Ocean Engn Busan 46241 South Korea Pohang Univ Sci & Technol Pohang Accelerator Lab Pohang 37673 South Korea

Interfaces in transition metal oxides play critical roles for tuning physical properties. In thin film form, multiple interfaces can be created in between a film and a substrate, in between a film and air, and within a thin film. The role of each interface has been rarely studied. In this research, we used MoO2 as a model system to study the role of the oxidized layer at film-air interface in thickness-driven metal-insulator transition. The oxidized layer at the surface is likely to be the main cause in positive temperature coefficient of resistivity in MoO2 thin films thinner than about 20 nm. To find the origin of this insulating behavior in electronic transport measurements, we used x-ray diffraction, density functional theory and various spectroscopic methods. We observed the formation of oxidized MoO2+x at the film-air interface and its thickness explain the peculiar insulating behavior in the thinner films and even nanoparticles from the literature.

关键词： Epitaxial thin films Metal-to-insulator transition Surface oxidation Density functional theory Spectroscopy

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