Pub Date : 2015-04-14DOI: 10.1007/978-1-4613-0373-2_36
H. Kobayashi, Y. Akedo, K. Kawakami
{"title":"The Aspect-Ratio Effect of He II Channels on the Heat Transport Characteristics","authors":"H. Kobayashi, Y. Akedo, K. Kawakami","doi":"10.1007/978-1-4613-0373-2_36","DOIUrl":"https://doi.org/10.1007/978-1-4613-0373-2_36","url":null,"abstract":"","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50961293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Modeling with REGEN3.3 has shown that the phase between flow and pressure at the cold end of 4 K regenerators has a large effect on their second-law efficiency. The use of inertance tubes in small 4 K pulse tube cryocoolers has limited phase-shifting ability, and their phase shift cannot be varied unless their dimensions are varied. We report here on the use of a miniature linear compressor, operating at the pulse tube warm end of about 30 K, as a controllable expander that can be used to vary the phase over 360°. We also use the back EMF of the linear motor to measure the acoustic power, flow rate amplitude, and phase between flow and pressure at the piston face. We discuss the measurements of the linear motor parameters that are required to determine the piston velocity from the back EMF as well as the measurement procedures to determine the back EMF when the expander is operating at a temperature around 30 K. Our experimental results on the performance of a regenerator/pulse tube stage operating below 30 K show an optimum performance when the flow at the phase shifter lags the pressure by about 65° to 80°, which is close to the model results of about 60°. Temperatures below 10 K were achieved at the cold end in these measurements. The efficiency of the compressor operating as an expander is also discussed.
{"title":"Effect of Flow-Pressure Phase on Performance of Regenerators in the Range of 4 K to 20 K","authors":"M. Lewis, R. P. Taylor, P. Bradley, R. Radebaugh","doi":"10.1063/1.4860751","DOIUrl":"https://doi.org/10.1063/1.4860751","url":null,"abstract":"Modeling with REGEN3.3 has shown that the phase between flow and pressure at the cold end of 4 K regenerators has a large effect on their second-law efficiency. The use of inertance tubes in small 4 K pulse tube cryocoolers has limited phase-shifting ability, and their phase shift cannot be varied unless their dimensions are varied. We report here on the use of a miniature linear compressor, operating at the pulse tube warm end of about 30 K, as a controllable expander that can be used to vary the phase over 360°. We also use the back EMF of the linear motor to measure the acoustic power, flow rate amplitude, and phase between flow and pressure at the piston face. We discuss the measurements of the linear motor parameters that are required to determine the piston velocity from the back EMF as well as the measurement procedures to determine the back EMF when the expander is operating at a temperature around 30 K. Our experimental results on the performance of a regenerator/pulse tube stage operating below 30 K show an optimum performance when the flow at the phase shifter lags the pressure by about 65° to 80°, which is close to the model results of about 60°. Temperatures below 10 K were achieved at the cold end in these measurements. The efficiency of the compressor operating as an expander is also discussed.","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.4860751","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58793604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Tatsumoto, Y. Shirai, M. Shiotsu, K. Hata, Y. Naruo, H. Kobayashi, Y. Inatani, Kensuke Kinoshita
Forced flow heat transfers of liquid hydrogen through horizontally-mounted tubes with the diameter of 3.0 mm and 6.0 mm were measured at the pressure of 0.7 MPa for various inlet temperatures and flow velocities. The measured non-boiling heat transfer coefficients agree with those by the Dittus-Boelter correlation. The heat fluxes at the onset of nucleate boiling and the departure from nucleate boiling (DNB) heat fluxes, where the heat transfer continuously changes to film boiling regime, are higher for higher flow velocity, larger subcooling and larger tube diameter. The DNB heat fluxes for the horizontally-mounted tube are slightly lower than those for the vertically-mounted tube, although the effect of the tube attitude direction disappears for a small tube diameter. The measured DNB heat fluxes agree with the correlation for vertically-mounted tubes.
{"title":"Forced convection heat transfer of subcooled liquid hydrogen in horizontal tubes","authors":"H. Tatsumoto, Y. Shirai, M. Shiotsu, K. Hata, Y. Naruo, H. Kobayashi, Y. Inatani, Kensuke Kinoshita","doi":"10.1063/1.4706987","DOIUrl":"https://doi.org/10.1063/1.4706987","url":null,"abstract":"Forced flow heat transfers of liquid hydrogen through horizontally-mounted tubes with the diameter of 3.0 mm and 6.0 mm were measured at the pressure of 0.7 MPa for various inlet temperatures and flow velocities. The measured non-boiling heat transfer coefficients agree with those by the Dittus-Boelter correlation. The heat fluxes at the onset of nucleate boiling and the departure from nucleate boiling (DNB) heat fluxes, where the heat transfer continuously changes to film boiling regime, are higher for higher flow velocity, larger subcooling and larger tube diameter. The DNB heat fluxes for the horizontally-mounted tube are slightly lower than those for the vertically-mounted tube, although the effect of the tube attitude direction disappears for a small tube diameter. The measured DNB heat fluxes agree with the correlation for vertically-mounted tubes.","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.4706987","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58644844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Granieri, B. Baudouy, A. Four, Fernando Lentijo, A. Mapelli, P. Petagna, D. Tommasini
The operation of the Large Hadron Collider superconducting magnets for current and high luminosity future applications relies on the cooling provided by helium-permeable cable insulations. These insulations take advantage of a He II micro-channels network constituting an extremely efficient path for heat extraction. In order to provide a fundamental understanding of the underlying thermal mechanisms, an experimental setup was built to investigate heat transport through single He II channels typical of the superconducting cable insulation network, where deviation from the macro-scale theory can appear. Micro-fabrication techniques were exploited to etch the channels down to a depth of ~ 16 im. The heat transport properties were measured in static pressurized He II and analyzed in terms of the laminar and turbulent He II laws, as well as in terms of the critical heat flux between the two regions.
{"title":"Steady-State heat transfer through micro-channels in pressurized He II","authors":"P. Granieri, B. Baudouy, A. Four, Fernando Lentijo, A. Mapelli, P. Petagna, D. Tommasini","doi":"10.1063/1.4706925","DOIUrl":"https://doi.org/10.1063/1.4706925","url":null,"abstract":"The operation of the Large Hadron Collider superconducting magnets for current and high luminosity future applications relies on the cooling provided by helium-permeable cable insulations. These insulations take advantage of a He II micro-channels network constituting an extremely efficient path for heat extraction. In order to provide a fundamental understanding of the underlying thermal mechanisms, an experimental setup was built to investigate heat transport through single He II channels typical of the superconducting cable insulation network, where deviation from the macro-scale theory can appear. Micro-fabrication techniques were exploited to etch the channels down to a depth of ~ 16 im. The heat transport properties were measured in static pressurized He II and analyzed in terms of the laminar and turbulent He II laws, as well as in terms of the critical heat flux between the two regions.","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.4706925","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58644589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The proposal by NASA to use high-temperature superconducting (HTS) generators and motors on future (~2035) aircraft for turboelectric propulsion imposes difficult requirements for cryocoolers. Net refrigeration powers of about 5 kW to 10 kW at 50 K to 65 K are needed for this application. A 2010 survey by Ladner of published work between 1999 and 2009 on existing Stirling and Stirling-type pulse tube cryocoolers showed efficiencies in the range of 10 to 20 % of Carnot at 50 K, much less than the 30 % of Carnot needed to make the concept feasible. A cryocooler specific mass less than about 3 kg/kW of input power is required to keep the cryocooler mass somewhat less than the mass of the superconducting machinery. Current cryocoolers have specific masses about 3 to 10 times this desired value, even for those designed for airborne or space use. We discuss loss and mass sources and make suggestions where improvements can be made. For Stirling and Stirling-type pulse tube cryocoolers, most of the mass is concen...
{"title":"Cryocoolers for aircraft superconducting generators and motors","authors":"R. Radebaugh","doi":"10.1063/1.4706918","DOIUrl":"https://doi.org/10.1063/1.4706918","url":null,"abstract":"The proposal by NASA to use high-temperature superconducting (HTS) generators and motors on future (~2035) aircraft for turboelectric propulsion imposes difficult requirements for cryocoolers. Net refrigeration powers of about 5 kW to 10 kW at 50 K to 65 K are needed for this application. A 2010 survey by Ladner of published work between 1999 and 2009 on existing Stirling and Stirling-type pulse tube cryocoolers showed efficiencies in the range of 10 to 20 % of Carnot at 50 K, much less than the 30 % of Carnot needed to make the concept feasible. A cryocooler specific mass less than about 3 kg/kW of input power is required to keep the cryocooler mass somewhat less than the mass of the superconducting machinery. Current cryocoolers have specific masses about 3 to 10 times this desired value, even for those designed for airborne or space use. We discuss loss and mass sources and make suggestions where improvements can be made. For Stirling and Stirling-type pulse tube cryocoolers, most of the mass is concen...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.4706918","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58644519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Flukiger, M. S. Hossain, M. Kulich, C. Senatore
The technical aspects correlated with the observed enhancement of mass density and critical current density in the filaments of in situ MgB2 wires by means of the recently developed Cold High Pressure Densification (CHPD) are reviewed. The present analysis first summarizes the results obtained by means of a short sample prototype device with anvil lengths of 39 mm. Pressures well above 1 GPa were applied to short wires, causing Jc enhancements between a factor 1.5 and 2.3 at 4.2 K and 8 T. At 20 K, the enhancement is much stronger and reaches a factor 3 for binary and 5 for alloyed MgB2 wires. Based on these results, an automatic machine has been developed allowing a sequential press/release/advance operation. With this machine, which has been very recently installed at GAP in Geneva, in situ MgB2 wires of lengths up to 10 meters have so far been successfully densified, confirming the Jc enhancements obtained with the short sample device. Using an improved anvil geometry, the wall friction was reduced with respect to the short sample prototype device, thus yielding the same Jc enhancements, but at considerably lower applied pressures: now, Jc max was obtained at 0.85 GPa, in contrast to values between 1.3 and 1.5 GPa for the short sample device. After densifying at this pressure, the value of Jc = 1 × 104 A/cm2 at 4.2 K was obtained at 13.2 T over 1 m length, thus corresponding to an enhancement by a factor 2.2 with respect to the non pressed wire. The present results are promising in view of the application of CHPD to industrial wire lengths.
{"title":"Technical aspects of cold high pressure densification (CHPD) on long lengths of In Situ MgB2 wires with enhanced Jc values","authors":"R. Flukiger, M. S. Hossain, M. Kulich, C. Senatore","doi":"10.1063/1.4712116","DOIUrl":"https://doi.org/10.1063/1.4712116","url":null,"abstract":"The technical aspects correlated with the observed enhancement of mass density and critical current density in the filaments of in situ MgB2 wires by means of the recently developed Cold High Pressure Densification (CHPD) are reviewed. The present analysis first summarizes the results obtained by means of a short sample prototype device with anvil lengths of 39 mm. Pressures well above 1 GPa were applied to short wires, causing Jc enhancements between a factor 1.5 and 2.3 at 4.2 K and 8 T. At 20 K, the enhancement is much stronger and reaches a factor 3 for binary and 5 for alloyed MgB2 wires. Based on these results, an automatic machine has been developed allowing a sequential press/release/advance operation. With this machine, which has been very recently installed at GAP in Geneva, in situ MgB2 wires of lengths up to 10 meters have so far been successfully densified, confirming the Jc enhancements obtained with the short sample device. Using an improved anvil geometry, the wall friction was reduced with respect to the short sample prototype device, thus yielding the same Jc enhancements, but at considerably lower applied pressures: now, Jc max was obtained at 0.85 GPa, in contrast to values between 1.3 and 1.5 GPa for the short sample device. After densifying at this pressure, the value of Jc = 1 × 104 A/cm2 at 4.2 K was obtained at 13.2 T over 1 m length, thus corresponding to an enhancement by a factor 2.2 with respect to the non pressed wire. The present results are promising in view of the application of CHPD to industrial wire lengths.","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.4712116","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58657839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Miniature Joule-Thomson coolers were developed at the University of Twente and are able to cool to 100 K with a typical cooling power of 10 to 20 mW. These coolers have a high potential for space applications in cooling small optical detectors for future earth observation and science missions. Under contract of the European Space Agency, we investigate on-chip detector cooling for the temperature range 70 K-250 K. To identify the detectors that can be cooled by a JT microcooler, a literature survey was performed. Following this survey, we selected a micro digital CMOS image sensor. A conceptual design of this cooler-sensor system is made. Among various techniques, indium soldering and silver paint are chosen for the bonding of the silicon sensor to the glass microcooler. Electrical connections from the sensor to the outside will be realized by structuring them in a thin layer of gold that is sputtered on the outside of the cooler to minimize the radiative heat load. For the electrical connections between the sensor and the structured leads, aluminum or gold bond wires will be used
{"title":"INTERFACING ISSUES IN MICROCOOLING OF OPTICAL DETECTORS IN SPACE APPLICATIONS","authors":"J. H. Derking, H. T. Brake, M. Linder, H. Rogalla","doi":"10.1063/1.3422411","DOIUrl":"https://doi.org/10.1063/1.3422411","url":null,"abstract":"Miniature Joule-Thomson coolers were developed at the University of Twente and are able to cool to 100 K with a typical cooling power of 10 to 20 mW. These coolers have a high potential for space applications in cooling small optical detectors for future earth observation and science missions. Under contract of the European Space Agency, we investigate on-chip detector cooling for the temperature range 70 K-250 K. To identify the detectors that can be cooled by a JT microcooler, a literature survey was performed. Following this survey, we selected a micro digital CMOS image sensor. A conceptual design of this cooler-sensor system is made. Among various techniques, indium soldering and silver paint are chosen for the bonding of the silicon sensor to the glass microcooler. Electrical connections from the sensor to the outside will be realized by structuring them in a thin layer of gold that is sputtered on the outside of the cooler to minimize the radiative heat load. For the electrical connections between the sensor and the structured leads, aluminum or gold bond wires will be used","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.3422411","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58870445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Sauers, E. Tuncer, G. Polizos, D. James, A. Ellis, M. Pace
For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0.1 Hz) has been used for conventional cables as a way of getting around the charging current limitation. For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G10 (fiberglass reinforced plastic or FRP), Cryoflex™ (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc. The dwell time at each step was chosen so that the aging factor wou...
{"title":"VERY LOW FREQUENCY BREAKDOWN PROPERTIES OF ELECTRICAL INSULATION MATERIALS AT CRYOGENIC TEMPERATURES","authors":"I. Sauers, E. Tuncer, G. Polizos, D. James, A. Ellis, M. Pace","doi":"10.1063/1.3402335","DOIUrl":"https://doi.org/10.1063/1.3402335","url":null,"abstract":"For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0.1 Hz) has been used for conventional cables as a way of getting around the charging current limitation. For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G10 (fiberglass reinforced plastic or FRP), Cryoflex™ (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc. The dwell time at each step was chosen so that the aging factor wou...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.3402335","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58730508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Duckworth, Y. Zhang, M. Gouge, C. Rey, D. V. D. Laan, C. Clickner
With recommendations from wire manufacturers as a starting point, a series of solder joints were fabricated and characterized to determine the best method for producing repeatable, low‐resistance and high‐mechanical‐strength splices in as‐manufactured, stabilized YBCO coated conductors. From the 2.54 cm long splice joints that were fabricated, parameters such as solder material, stabilization material, fabrication method, and conductor geometry were varied to determine the impact of each on the properties of splice joints. Results indicate that the splice joints of lowest resistance were influenced primarily by the tape orientation in the joint and the stabilization material. The lowest resistances were between 2×10−8 Ω and 1.0×10−7 Ω in 4‐mm wide tapes and were obtained from pure copper‐stabilized tapes oriented with the YBCO layers in closest proximity. The voltage drop along the splice length indicated that only a fraction of the splice length contributes to the splice joint resistance. Mechanical char...
{"title":"VOLTAGE DISTRIBUTION AND MECHANICAL STRENGTH IN SPLICE JOINTS MADE FROM AS‐MANUFACTURED YBCO COATED CONDUCTORS","authors":"R. Duckworth, Y. Zhang, M. Gouge, C. Rey, D. V. D. Laan, C. Clickner","doi":"10.1063/1.3402325","DOIUrl":"https://doi.org/10.1063/1.3402325","url":null,"abstract":"With recommendations from wire manufacturers as a starting point, a series of solder joints were fabricated and characterized to determine the best method for producing repeatable, low‐resistance and high‐mechanical‐strength splices in as‐manufactured, stabilized YBCO coated conductors. From the 2.54 cm long splice joints that were fabricated, parameters such as solder material, stabilization material, fabrication method, and conductor geometry were varied to determine the impact of each on the properties of splice joints. Results indicate that the splice joints of lowest resistance were influenced primarily by the tape orientation in the joint and the stabilization material. The lowest resistances were between 2×10−8 Ω and 1.0×10−7 Ω in 4‐mm wide tapes and were obtained from pure copper‐stabilized tapes oriented with the YBCO layers in closest proximity. The voltage drop along the splice length indicated that only a fraction of the splice length contributes to the splice joint resistance. Mechanical char...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.3402325","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58730814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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