The size of Stirling and Stirling‐type pulse tube cryocoolers is dominated by the size of the pressure oscillator. Such cryocoolers typically operate at frequencies up to about 60 Hz for cold‐end temperatures above about 60 K. Higher operating frequencies would allow the size and mass of the pressure oscillator to be reduced for a given power input. However, simply increasing the operating frequency leads to large losses in the regenerator. The simple analytical equations derived here show how the right combination of frequency and pressure, along with optimized regenerator geometry, can lead to successful regenerator operation at frequencies up to 1 kHz. Efficient regenerator operation at such high frequencies is possible only with pressures of about 5 to 8 MPa and with very small hydraulic diameters and lengths. Other geometrical parameters must also be optimized for such conditions. The analytical equations are used to provide guidance to the right combination of parameters. We give example numerical calculations with REGEN3.2 in the paper for 60 Hz, 400 Hz, and 1000 Hz operation of optimized screen regenerators and show that the coefficient of performance at 400 Hz and 1000 Hz is about 78 % and 68 %, respectively, of that for 60 Hz when an average pressure of 7 MPa is used with the higher frequency, compared with 2.5 MPa for 60 Hz operation. The 1000 Hz coefficient of performance for parallel tubes is about the same as that of the screen geometry at 60 Hz. The compressor and cold‐end swept volumes are reduced by a factor of 47 at 1000 Hz, compared with the 60 Hz case for the same input acoustic power, which can enable the development of microcryocoolers for MEMS applications.
{"title":"Regenerator Operation at Very High Frequencies for Microcryocoolers","authors":"R. Radebaugh, A. O'Gallagher","doi":"10.1063/1.2202623","DOIUrl":"https://doi.org/10.1063/1.2202623","url":null,"abstract":"The size of Stirling and Stirling‐type pulse tube cryocoolers is dominated by the size of the pressure oscillator. Such cryocoolers typically operate at frequencies up to about 60 Hz for cold‐end temperatures above about 60 K. Higher operating frequencies would allow the size and mass of the pressure oscillator to be reduced for a given power input. However, simply increasing the operating frequency leads to large losses in the regenerator. The simple analytical equations derived here show how the right combination of frequency and pressure, along with optimized regenerator geometry, can lead to successful regenerator operation at frequencies up to 1 kHz. Efficient regenerator operation at such high frequencies is possible only with pressures of about 5 to 8 MPa and with very small hydraulic diameters and lengths. Other geometrical parameters must also be optimized for such conditions. The analytical equations are used to provide guidance to the right combination of parameters. We give example numerical calculations with REGEN3.2 in the paper for 60 Hz, 400 Hz, and 1000 Hz operation of optimized screen regenerators and show that the coefficient of performance at 400 Hz and 1000 Hz is about 78 % and 68 %, respectively, of that for 60 Hz when an average pressure of 7 MPa is used with the higher frequency, compared with 2.5 MPa for 60 Hz operation. The 1000 Hz coefficient of performance for parallel tubes is about the same as that of the screen geometry at 60 Hz. The compressor and cold‐end swept volumes are reduced by a factor of 47 at 1000 Hz, compared with the 60 Hz case for the same input acoustic power, which can enable the development of microcryocoolers for MEMS applications.","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2202623","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58260917","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. Radebaugh, M. Lewis, E. Luo, J. Pfotenhauer, G. Nellis, L. Schunk
The efficiency of regenerative refrigerators is generally maximized when the pressure and flow are in phase near the midpoint of the regenerator. Such a phase relationship minimizes the amplitude of the mass flow for a given acoustic power flow through the regenerator. To achieve this phase relationship in a pulse tube refrigerator requires that the flow at the warm end of the pulse tube lag the pressure by about 60 degrees. The inertance tube allows for the flow to lag the pressure, but such a large phase shift is only possible with relatively large acoustic power flows. In small pulse tube cryocoolers the efficiency is improved by maximizing the phase shift in the inertance tube. This paper describes a simple transmission line model of the inertance tube, which is used to find the maximum phase shift and the corresponding diameter and length of the optimized inertance tube. Acoustic power flows between 1 and 100 W are considered in this study, though the model may be valid for larger systems as well. Fo...
{"title":"Inertance Tube Optimization for Pulse Tube Refrigerators","authors":"R. Radebaugh, M. Lewis, E. Luo, J. Pfotenhauer, G. Nellis, L. Schunk","doi":"10.1063/1.2202401","DOIUrl":"https://doi.org/10.1063/1.2202401","url":null,"abstract":"The efficiency of regenerative refrigerators is generally maximized when the pressure and flow are in phase near the midpoint of the regenerator. Such a phase relationship minimizes the amplitude of the mass flow for a given acoustic power flow through the regenerator. To achieve this phase relationship in a pulse tube refrigerator requires that the flow at the warm end of the pulse tube lag the pressure by about 60 degrees. The inertance tube allows for the flow to lag the pressure, but such a large phase shift is only possible with relatively large acoustic power flows. In small pulse tube cryocoolers the efficiency is improved by maximizing the phase shift in the inertance tube. This paper describes a simple transmission line model of the inertance tube, which is used to find the maximum phase shift and the corresponding diameter and length of the optimized inertance tube. Acoustic power flows between 1 and 100 W are considered in this study, though the model may be valid for larger systems as well. Fo...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2202401","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58260906","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 notch effects on the high‐cycle fatigue properties of Ti‐6Al‐4V ELI alloy have been investigated at cryogenic temperatures. Smooth and notched specimens with the Kt=1.5, Kt=2 and Kt=3 were prepared. High‐cycle fatigue tests were carried out at 4, 77 and 293 K. One million cycles fatigue strength (FS) of smooth specimen was increased with a decrease of the test temperature. Although the FS of each notched specimen at 4 K were lower than those of 77 K. Fatigue crack initiation sites of the smooth, the Kt=1.5 and the Kt=2 notched specimens at 4 K were facets in the specimen interior (internal type fracture) and those of the Kt=3 notched specimens were at the notch root (surface type fracture). The size of individual facets comprising the internal fatigue crack initiation sites correspond to almost the α‐grain size. Therefore, improvement of the fatigue strength of the notched specimens for Ti‐6Al‐4V ELI alloy which show internal type fracture at cryogenic temperatures requires attaining a smaller area si...
{"title":"High‐Cycle Fatigue Properties of Notched Specimens for Ti‐6Al‐4V ELI Alloy at Cryogenic Temperatures","authors":"T. Yuri, Y. Ono, T. Ogata","doi":"10.1063/1.2192347","DOIUrl":"https://doi.org/10.1063/1.2192347","url":null,"abstract":"The notch effects on the high‐cycle fatigue properties of Ti‐6Al‐4V ELI alloy have been investigated at cryogenic temperatures. Smooth and notched specimens with the Kt=1.5, Kt=2 and Kt=3 were prepared. High‐cycle fatigue tests were carried out at 4, 77 and 293 K. One million cycles fatigue strength (FS) of smooth specimen was increased with a decrease of the test temperature. Although the FS of each notched specimen at 4 K were lower than those of 77 K. Fatigue crack initiation sites of the smooth, the Kt=1.5 and the Kt=2 notched specimens at 4 K were facets in the specimen interior (internal type fracture) and those of the Kt=3 notched specimens were at the notch root (surface type fracture). The size of individual facets comprising the internal fatigue crack initiation sites correspond to almost the α‐grain size. Therefore, improvement of the fatigue strength of the notched specimens for Ti‐6Al‐4V ELI alloy which show internal type fracture at cryogenic temperatures requires attaining a smaller area si...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2192347","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59396486","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}
Y. Ono, T. Yuri, H. Sumiyoshi, Etsuo Takeuchi, S. Matsuoka, T. Ogata
High‐cycle fatigue properties at 4 K, 20 K, 77 K and 293 K were investigated in forged‐INCONEL 718 nickel‐based superalloy with a mean gamma (γ) grain size of 25 μm. In the present material, plate‐like delta phase precipitated at γ grain boundaries and niobium (Nb)‐enriched MC type carbides precipitated coarsely throughout the specimens. The 0.2% proof stress and the tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. High‐cycle fatigue strengths also increased with decreasing temperature although the fatigue limit at each temperature didn’t appear even around 107 cycles. Fatigue cracks initiated near the specimen surface and formed faceted structures around crack initiation sites. Fatigue cracks predominantly initiated from coarse Nb‐enriched carbides and faceted structures mainly corresponded to these carbides. In lower stress amplitude tests, however, facets were formed through transgranular crack initiation and growth. These kinds o...
{"title":"High‐Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718","authors":"Y. Ono, T. Yuri, H. Sumiyoshi, Etsuo Takeuchi, S. Matsuoka, T. Ogata","doi":"10.1063/1.2192350","DOIUrl":"https://doi.org/10.1063/1.2192350","url":null,"abstract":"High‐cycle fatigue properties at 4 K, 20 K, 77 K and 293 K were investigated in forged‐INCONEL 718 nickel‐based superalloy with a mean gamma (γ) grain size of 25 μm. In the present material, plate‐like delta phase precipitated at γ grain boundaries and niobium (Nb)‐enriched MC type carbides precipitated coarsely throughout the specimens. The 0.2% proof stress and the tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. High‐cycle fatigue strengths also increased with decreasing temperature although the fatigue limit at each temperature didn’t appear even around 107 cycles. Fatigue cracks initiated near the specimen surface and formed faceted structures around crack initiation sites. Fatigue cracks predominantly initiated from coarse Nb‐enriched carbides and faceted structures mainly corresponded to these carbides. In lower stress amplitude tests, however, facets were formed through transgranular crack initiation and growth. These kinds o...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2192350","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59396499","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. Taylor, G. Nellis, S. Klein, D. W. Hoch, J. Fellers, P. Roach, J. Park, Y. Gianchandani
Future NASA missions require cooling of large structures in space. One class of thermal management solutions for providing controlled, distributed cooling would utilize actively controlled micro‐scale valves that are integrated with heat exchangers and sensors in order to provide independent, local temperature control. The most attractive actuation method for these micro‐valves is a multilayer piezoelectric (PZT) stack because this technology is capable of providing large force using reasonable voltages (e.g., < 100 V) with minimal power draw. In order to design a micro‐valve configuration that takes advantage of this actuation technique, it is necessary to obtain information regarding the behavior of piezoelectric materials at cryogenic temperatures. This paper describes a test facility that was designed to achieve precise measurements of the coefficient of thermal expansion (CTE) and PZT stack actuator constant (d33) from 40 K to room temperature. The operation of the facility is validated by measuring ...
{"title":"Measurements of the Material Properties of a Laminated Piezoelectric Stack at Cryogenic Temperatures","authors":"R. Taylor, G. Nellis, S. Klein, D. W. Hoch, J. Fellers, P. Roach, J. Park, Y. Gianchandani","doi":"10.1063/1.2192352","DOIUrl":"https://doi.org/10.1063/1.2192352","url":null,"abstract":"Future NASA missions require cooling of large structures in space. One class of thermal management solutions for providing controlled, distributed cooling would utilize actively controlled micro‐scale valves that are integrated with heat exchangers and sensors in order to provide independent, local temperature control. The most attractive actuation method for these micro‐valves is a multilayer piezoelectric (PZT) stack because this technology is capable of providing large force using reasonable voltages (e.g., < 100 V) with minimal power draw. In order to design a micro‐valve configuration that takes advantage of this actuation technique, it is necessary to obtain information regarding the behavior of piezoelectric materials at cryogenic temperatures. This paper describes a test facility that was designed to achieve precise measurements of the coefficient of thermal expansion (CTE) and PZT stack actuator constant (d33) from 40 K to room temperature. The operation of the facility is validated by measuring ...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2192352","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59396557","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}
M. W. Stewart, M. Hooker, P. Fabian, D. Codell, S. Arzberger, S. Grandlienard, K. Kano
Future magnet designs for fusion devices and particle accelerators will require cost‐effective, radiation‐resistant materials. The use of hybrid inorganic/organic composite insulation systems will improve the lifetime, reliability, and performance of these systems. Previously, Composite Technology Development, Inc. (CTD) developed a highly‐radiation‐resistant, hybrid inorganic/organic insulation system, CTD‐1012PX, which can be co‐processed with the magnet’s Nb3Sn superconductor. This process allows the coil to be wound and insulated prior to heat treatment. However, the cost of the CTD‐1012PX insulation system is generally higher than organic insulations due to the higher prices of the ceramic fibers and ceramic‐matrix precursor materials. Recently, CTD demonstrated the potential for significantly reducing the cost of hybrid ceramic/organic insulation through the development of a lower‐cost inorganic‐matrix system and the use of lower‐cost reinforcement fibers. Without accounting for the cost of a yet‐to...
{"title":"Development of a Low‐Cost Ceramic Insulation Material for Magnet Applications","authors":"M. W. Stewart, M. Hooker, P. Fabian, D. Codell, S. Arzberger, S. Grandlienard, K. Kano","doi":"10.1063/1.2192367","DOIUrl":"https://doi.org/10.1063/1.2192367","url":null,"abstract":"Future magnet designs for fusion devices and particle accelerators will require cost‐effective, radiation‐resistant materials. The use of hybrid inorganic/organic composite insulation systems will improve the lifetime, reliability, and performance of these systems. Previously, Composite Technology Development, Inc. (CTD) developed a highly‐radiation‐resistant, hybrid inorganic/organic insulation system, CTD‐1012PX, which can be co‐processed with the magnet’s Nb3Sn superconductor. This process allows the coil to be wound and insulated prior to heat treatment. However, the cost of the CTD‐1012PX insulation system is generally higher than organic insulations due to the higher prices of the ceramic fibers and ceramic‐matrix precursor materials. Recently, CTD demonstrated the potential for significantly reducing the cost of hybrid ceramic/organic insulation through the development of a lower‐cost inorganic‐matrix system and the use of lower‐cost reinforcement fibers. Without accounting for the cost of a yet‐to...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2192367","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59396783","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}
M. Sumption, M. Bhatia, F. Buta, S. Bohnenstiehl, M. Tomsic, M. Rindfleisch, J. Yue, J. Phillips, S. Kawabata, E. Collings
Results from measurements on five racetrack coils and one solenoid coil are reported in this work. Three of the racetracks were wound with monofilamentary strand, and two from multifilamentary 19‐stack strands. The solenoid coil was wound from 7‐stack multifilamentary strand. Some strands had Fe barriers, others Nb, some had none. Outer sheaths of pure Cu, Cu‐30Ni, and monel were investigated. S‐glass insulation was used in all cases. Some coils were potted in CTD101, others in Stycast. Transport Jc measurements were performed initially in liquid helium, and then as a function of temperature up to 30 K. The highest result at self field was 400 A at 12 K for a racetrack coil. This coil had a Jc of 200 kA/cm2, a Je of 50 kA/cm2, and a winding pack Je of 26 kA/cm2, all as measured at 12 K. The 20 K results were Ic = 260 A, Jc = 130 A/cm2, Je = 32.6 kA/cm2, and Jw = 17.5 kA/cm2. The B field generated by the racetrack was 0.44 T at 12 K and 0.29 T at 20 K. The solenoid coil critical current was lower than this...
{"title":"Solenoid and Racetrack Coils Wound from MgB2 Strand","authors":"M. Sumption, M. Bhatia, F. Buta, S. Bohnenstiehl, M. Tomsic, M. Rindfleisch, J. Yue, J. Phillips, S. Kawabata, E. Collings","doi":"10.1063/1.2192382","DOIUrl":"https://doi.org/10.1063/1.2192382","url":null,"abstract":"Results from measurements on five racetrack coils and one solenoid coil are reported in this work. Three of the racetracks were wound with monofilamentary strand, and two from multifilamentary 19‐stack strands. The solenoid coil was wound from 7‐stack multifilamentary strand. Some strands had Fe barriers, others Nb, some had none. Outer sheaths of pure Cu, Cu‐30Ni, and monel were investigated. S‐glass insulation was used in all cases. Some coils were potted in CTD101, others in Stycast. Transport Jc measurements were performed initially in liquid helium, and then as a function of temperature up to 30 K. The highest result at self field was 400 A at 12 K for a racetrack coil. This coil had a Jc of 200 kA/cm2, a Je of 50 kA/cm2, and a winding pack Je of 26 kA/cm2, all as measured at 12 K. The 20 K results were Ic = 260 A, Jc = 130 A/cm2, Je = 32.6 kA/cm2, and Jw = 17.5 kA/cm2. The B field generated by the racetrack was 0.44 T at 12 K and 0.29 T at 20 K. The solenoid coil critical current was lower than this...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2192382","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59398453","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}
T. Holesinger, J. Kennison, H. Miao, M. Meinesz, K. Marken, S. Hong, S. Campbell
Bi2Sr2CaCu2Oy (Bi‐2212) conductors are of interest for magnet applications in high magnetic fields at 4 K. The partial melt approach affords an economical, single processing step for the conductor heat treatment. However, work remains to be done to optimize compositions and conductor performance. In this paper, the beneficial effects of alumina additions for the melt‐processing of Bi‐2212 conductors are reported. It is found that for conventional melt processing, the alumina additions broaden the processing window for the peak melting temperature and improve the critical current density of the conductors. With regards to the microstructure, the alumina additions appear to inhibit the growth of alkaline‐earth cuprates.
{"title":"The Effect of Alumina Additions on the Processing of Bi‐2212 Conductors","authors":"T. Holesinger, J. Kennison, H. Miao, M. Meinesz, K. Marken, S. Hong, S. Campbell","doi":"10.1063/1.2192410","DOIUrl":"https://doi.org/10.1063/1.2192410","url":null,"abstract":"Bi2Sr2CaCu2Oy (Bi‐2212) conductors are of interest for magnet applications in high magnetic fields at 4 K. The partial melt approach affords an economical, single processing step for the conductor heat treatment. However, work remains to be done to optimize compositions and conductor performance. In this paper, the beneficial effects of alumina additions for the melt‐processing of Bi‐2212 conductors are reported. It is found that for conventional melt processing, the alumina additions broaden the processing window for the peak melting temperature and improve the critical current density of the conductors. With regards to the microstructure, the alumina additions appear to inhibit the growth of alkaline‐earth cuprates.","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2192410","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59399324","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 influences of Gd or Eu substitution on the local electronic density, lattice structure and the superconductivity are systemically studied by means of positron annihilation technique (PAT) and x‐ray diffraction (XRD) for Y1−xRxBa2Cu3O7−δ (R=Gd, Eu; x=0.0, 0.2, 0.5, 1.0) systems. XRD results show that all of the Y1−xRxBa2Cu3O7−δ samples have an orthorhombic phase as same as YBa2Cu3O7−δ (YBCO) sample. The positron annihilation experiments show that the mean positron lifetime increases with increasing Eu or Gd substitution content. The local electron density ne is evaluated as a function of the substitution content. The results indicate that the substitution ions in Y sites not only influence the local electron density around Y ion, but also change the distribution of electron density around Cu‐O chains. These results prove that the changes of ne, the degree of orthorhombic distortion and the coupling between the Cu‐O chains and the CuO2 planes all have an effect on the superconductivity of Y1−xRxBa2Cu3O7...
{"title":"Influence of Gd/Eu Substitution on the Local Electron Density and the Superconductivity of Y1−xRxBa2Cu3O7−δ (R=Gd, Eu) Systems","authors":"Z. Chen, Y. Xue, Y. Su, J. Jin, Z. Tian","doi":"10.1063/1.2192430","DOIUrl":"https://doi.org/10.1063/1.2192430","url":null,"abstract":"The influences of Gd or Eu substitution on the local electronic density, lattice structure and the superconductivity are systemically studied by means of positron annihilation technique (PAT) and x‐ray diffraction (XRD) for Y1−xRxBa2Cu3O7−δ (R=Gd, Eu; x=0.0, 0.2, 0.5, 1.0) systems. XRD results show that all of the Y1−xRxBa2Cu3O7−δ samples have an orthorhombic phase as same as YBa2Cu3O7−δ (YBCO) sample. The positron annihilation experiments show that the mean positron lifetime increases with increasing Eu or Gd substitution content. The local electron density ne is evaluated as a function of the substitution content. The results indicate that the substitution ions in Y sites not only influence the local electron density around Y ion, but also change the distribution of electron density around Cu‐O chains. These results prove that the changes of ne, the degree of orthorhombic distortion and the coupling between the Cu‐O chains and the CuO2 planes all have an effect on the superconductivity of Y1−xRxBa2Cu3O7...","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2192430","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59399935","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}
We measured AC transport current losses in three YBCO tapes placed in parallel with the wide faces of the tapes on a flat plane using an electric method which was specially developed to properly measure the losses in tapes arranged in such a way. The measurement results showed that the transport current losses in an YBCO tape were significantly affected by the magnetic fields produced by the currents in the adjacent tapes. In the paper, the experimental results are explained by considering the magnetic field distribution around the tapes.
{"title":"AC Transport Current Losses in YBCO Tapes with Ajacent Tapes","authors":"S. Nakamura, J. Ogawa, O. Tsukamoto","doi":"10.1063/1.2192436","DOIUrl":"https://doi.org/10.1063/1.2192436","url":null,"abstract":"We measured AC transport current losses in three YBCO tapes placed in parallel with the wide faces of the tapes on a flat plane using an electric method which was specially developed to properly measure the losses in tapes arranged in such a way. The measurement results showed that the transport current losses in an YBCO tape were significantly affected by the magnetic fields produced by the currents in the adjacent tapes. In the paper, the experimental results are explained by considering the magnetic field distribution around the tapes.","PeriodicalId":80359,"journal":{"name":"Advances in cryogenic engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/1.2192436","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59400497","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：