Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.030
H. Park, Soohyeon Shin, Soon-Gil Jung, Do-Yeon Hwang, Hyoyoung Lee, T. Park
{"title":"Synthesis of the Ni-doped ternary compound Ba(Fe 1-x Ni x ) 2 Se 3","authors":"H. Park, Soohyeon Shin, Soon-Gil Jung, Do-Yeon Hwang, Hyoyoung Lee, T. Park","doi":"10.9714/PSAC.2015.17.4.030","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.030","url":null,"abstract":"","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"30-33"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376663","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}
Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.016
Seokbae Lee, D. Song, E. Jung, S. Roh, Changyoung Kim, Jenq-Neng Hwang
We investigated optical properties of an electron-doped copper oxide high temperature superconductor, Pr0.85LaCe0.15CuO4 (PLCCO) single crystal. We obtained the optical conductivity from measured reflectance at various temperatures. We found our data contained c-axis longitudinal optical (LO) phonon modes due to miscut and intrinsic lattice distortion. We applied an extended Drude model to study the correlations between charge carriers in the system. The LO phonons appear as strong sharp peaks in the optical scattering rate. We tried to remove the LO phonon modes by using the energy loss function, which also shows the LO phonons as peaks, and could not remove them completely. We extracted the electron-boson spectral density function using a generalized Allen's formula. We observed that the resulting electron-boson density show similar temperature dependence as hole-doped cuprates.
{"title":"Extended Drude model analysis of n-doped cuprate, Pr 0.85 LaCe 0.15 CuO 4","authors":"Seokbae Lee, D. Song, E. Jung, S. Roh, Changyoung Kim, Jenq-Neng Hwang","doi":"10.9714/PSAC.2015.17.4.016","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.016","url":null,"abstract":"We investigated optical properties of an electron-doped copper oxide high temperature superconductor, Pr0.85LaCe0.15CuO4 (PLCCO) single crystal. We obtained the optical conductivity from measured reflectance at various temperatures. We found our data contained c-axis longitudinal optical (LO) phonon modes due to miscut and intrinsic lattice distortion. We applied an extended Drude model to study the correlations between charge carriers in the system. The LO phonons appear as strong sharp peaks in the optical scattering rate. We tried to remove the LO phonon modes by using the energy loss function, which also shows the LO phonons as peaks, and could not remove them completely. We extracted the electron-boson spectral density function using a generalized Allen's formula. We observed that the resulting electron-boson density show similar temperature dependence as hole-doped cuprates.","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"16-20"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376649","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}
Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.043
Youngkwon Kim, M. K. Lee, Y. W. Jo, J. Choi, Hyobong Kim, W. Kim, Hyungjun Kim
The heavy ion accelerator that will be built in Daejeon utilizes four types of superconducting cavities. Cryomodules holding the superconducting cavities in them supply thermal insulation for cavities operating in 4.3 K or 2.1 K. A Prototype of cryomodule which holds two HWR (Half Wave Resonator) cavities was fabricated and tested. Since the operating temperature of the HWR is 2.1 K, the superfluid helium was generated with warm vacuum pumping system. The cyromodule was successfully cooled down below lambda point temperature of helium and any detectable leak was not observed during the test. The static thermal load at 4.2 K was measured. The result and the experience for the cool-down below lambda point of helium are reported in this paper.
{"title":"Cool-down test of HWR cryomodule for RAON","authors":"Youngkwon Kim, M. K. Lee, Y. W. Jo, J. Choi, Hyobong Kim, W. Kim, Hyungjun Kim","doi":"10.9714/PSAC.2015.17.4.043","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.043","url":null,"abstract":"The heavy ion accelerator that will be built in Daejeon utilizes four types of superconducting cavities. Cryomodules holding the superconducting cavities in them supply thermal insulation for cavities operating in 4.3 K or 2.1 K. A Prototype of cryomodule which holds two HWR (Half Wave Resonator) cavities was fabricated and tested. Since the operating temperature of the HWR is 2.1 K, the superfluid helium was generated with warm vacuum pumping system. The cyromodule was successfully cooled down below lambda point temperature of helium and any detectable leak was not observed during the test. The static thermal load at 4.2 K was measured. The result and the experience for the cool-down below lambda point of helium are reported in this paper.","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"43-46"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376519","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}
Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.025
H. Moon, H. Shin, H. Jin, W. Jo, Seokhyun Yoon
In 1987, M. K. Wu and Paul Chu discovered Y 1.2 Ba 0.8 CuO 4 (YBCO) with critical temperature (T c ) of 93 K. It has significantly lowered the cost of cooling of a material up to the point where superconductivity set in. Utilizing the cost reduction of attaining superconductivity and the vast amount of research to understand characteristics of high temperature oxide superconducting materials, there has been effort to use a high temperature superconductor as a coated conductor. It is important to characterize the materials precisely for stable performance before commercializing. We used polarized Raman scattering spectroscopy to study structural and stoichiometric information regarding YBa 2 Cu 3 O 7-x , GdYBa 2 Cu 3 O 7-x , and GdBa 2 Cu 3 O 7-x produced by three leading groups of producing commercial grade high temperature superconductor coated conductors American Superconductor Corporation, Superpower, and SuNAM.
1987年，M. K. Wu和Paul Chu发现临界温度为93 K的y1.2 Ba 0.8 CuO 4 (YBCO)。它大大降低了材料冷却到超导的成本。利用获得超导性的成本降低和对高温氧化物超导材料特性的大量研究，人们一直在努力使用高温超导体作为涂层导体。在商业化之前，对材料进行精确的表征以获得稳定的性能是非常重要的。我们利用偏振拉曼散射光谱研究了美国超导公司、超级大国和SuNAM三个生产商业级高温超导涂层导体的领先团队生产的YBa 2 Cu 3 O 7-x、GdYBa 2 Cu 3 O 7-x和GdBa 2 Cu 3 O 7-x的结构和化学计量信息。
{"title":"Local structural study of commercial grade MBa 2 Cu 3 O 7-x (M = Y and/or Gd) coated conductors by polarized Raman spectroscopy","authors":"H. Moon, H. Shin, H. Jin, W. Jo, Seokhyun Yoon","doi":"10.9714/PSAC.2015.17.4.025","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.025","url":null,"abstract":"In 1987, M. K. Wu and Paul Chu discovered Y 1.2 Ba 0.8 CuO 4 (YBCO) with critical temperature (T c ) of 93 K. It has significantly lowered the cost of cooling of a material up to the point where superconductivity set in. Utilizing the cost reduction of attaining superconductivity and the vast amount of research to understand characteristics of high temperature oxide superconducting materials, there has been effort to use a high temperature superconductor as a coated conductor. It is important to characterize the materials precisely for stable performance before commercializing. We used polarized Raman scattering spectroscopy to study structural and stoichiometric information regarding YBa 2 Cu 3 O 7-x , GdYBa 2 Cu 3 O 7-x , and GdBa 2 Cu 3 O 7-x produced by three leading groups of producing commercial grade high temperature superconductor coated conductors American Superconductor Corporation, Superpower, and SuNAM.","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"25-29"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376658","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}
Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.001
Sangkwon Jeong, Changgi Park
Abstract This paper addresses technical problems of thermal contact conductance or resistance which inevitably occurs in most cryogenic engineering systems. The main focus of this paper is to examine what kind of physical factors primarily influences the thermal contact resistance and to suggest how it can be minimized. It is a good practical rule that the contact surface must have sub-micron roughness level with no oxide layer and be thinly covered by indium, gold, or Apiezon-N grease for securing sufficient direct contact area. The higher contact pressure, the lower the thermal contact resistance. The general description of this technique has been widely perceived and reasonable engineering results have been achieved in most applications. However, the detailed view of employing these techniques and their relative efficacies to reduce thermal contact resistances need to be thoroughly reviewed. We should consider specific thermal contact conditions, examine the engineering requirements, and execute each method with precautions to fulfil their maximum potentials.
{"title":"Review : Thermal contact problems at cryogenic temperature","authors":"Sangkwon Jeong, Changgi Park","doi":"10.9714/PSAC.2015.17.4.001","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.001","url":null,"abstract":"Abstract This paper addresses technical problems of thermal contact conductance or resistance which inevitably occurs in most cryogenic engineering systems. The main focus of this paper is to examine what kind of physical factors primarily influences the thermal contact resistance and to suggest how it can be minimized. It is a good practical rule that the contact surface must have sub-micron roughness level with no oxide layer and be thinly covered by indium, gold, or Apiezon-N grease for securing sufficient direct contact area. The higher contact pressure, the lower the thermal contact resistance. The general description of this technique has been widely perceived and reasonable engineering results have been achieved in most applications. However, the detailed view of employing these techniques and their relative efficacies to reduce thermal contact resistances need to be thoroughly reviewed. We should consider specific thermal contact conditions, examine the engineering requirements, and execute each method with precautions to fulfil their maximum potentials.","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"1-7"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376635","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}
Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.034
Jieun Kim, Bakul Gohel, Kiwoong Kim, Hyukchan Kwon, Kyung-min An
Developing Magnetoencephalography (MEG) based on Superconducting Quantum Interference Device (SQUID) facilitates to observe the human brain functions in non-invasively and high temporal and high spatial resolution. By using this MEG, we studied alpha rhythm (8-13 Hz) that is one of the most predominant spontaneous rhythm in human brain. The 8–13 Hz rhythm is observed in several sensory region in the brain. In visual related region of occipital, we call to alpha rhythm, and auditory related region of temporal call to tau rhythm, sensorimotor related region of parietal call to mu rhythm. These rhythms are decreased in task related region and increased in task irrelevant regions. This means that these rhythms play a pivotal role of inhibition in task irrelevant region. It may be helpful to attention to the task. In several literature about the alpha-band inhibition in multi-sensory modality experiment, they observed this effect in the occipital and somatosensory region. In this study, we hypothesized that we can also observe the alpha-band inhibition in the auditory cortex, mediated by the tau rhythm. Before that, we first investigated the existence of the alpha and tau rhythm in occipital and temporal region, respectively. To see these rhythms, we applied the visual and auditory stimulation, in turns, suppressed in task relevant regions, respectively.
{"title":"Measurement of the occipital alpha rhythm and temporal tau rhythm by using magnetoencephalography","authors":"Jieun Kim, Bakul Gohel, Kiwoong Kim, Hyukchan Kwon, Kyung-min An","doi":"10.9714/PSAC.2015.17.4.034","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.034","url":null,"abstract":"Developing Magnetoencephalography (MEG) based on Superconducting Quantum Interference Device (SQUID) facilitates to observe the human brain functions in non-invasively and high temporal and high spatial resolution. By using this MEG, we studied alpha rhythm (8-13 Hz) that is one of the most predominant spontaneous rhythm in human brain. The 8–13 Hz rhythm is observed in several sensory region in the brain. In visual related region of occipital, we call to alpha rhythm, and auditory related region of temporal call to tau rhythm, sensorimotor related region of parietal call to mu rhythm. These rhythms are decreased in task related region and increased in task irrelevant regions. This means that these rhythms play a pivotal role of inhibition in task irrelevant region. It may be helpful to attention to the task. In several literature about the alpha-band inhibition in multi-sensory modality experiment, they observed this effect in the occipital and somatosensory region. In this study, we hypothesized that we can also observe the alpha-band inhibition in the auditory cortex, mediated by the tau rhythm. Before that, we first investigated the existence of the alpha and tau rhythm in occipital and temporal region, respectively. To see these rhythms, we applied the visual and auditory stimulation, in turns, suppressed in task relevant regions, respectively.","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"34-37"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376666","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}
Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.008
D. Lee, Y. Lee, H. Noh
{"title":"Study on visible emission of Cu-ion-doped perovskite hafnate in view of excitation energy dependence","authors":"D. Lee, Y. Lee, H. Noh","doi":"10.9714/PSAC.2015.17.4.008","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.008","url":null,"abstract":"","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"8-11"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376640","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}
Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.021
K. W. Kim, Thomas Wolf, C. Bernhard
We report optical spectra of underdoped BaFe1.89Co0.11As2 that hosts both of magnetic and superconducting orders. The temperature dependent evolution of optical conductivity shows finger prints of the magnetic order and the s-wave nature of the superconducting gaps. Careful inspection on the superconducting state reveals that the two orders compete but coexist in the ground state.
{"title":"Superconducting transition in the Presence of Magnetic order in BaFe1.89Co0.11As2","authors":"K. W. Kim, Thomas Wolf, C. Bernhard","doi":"10.9714/PSAC.2015.17.4.021","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.021","url":null,"abstract":"We report optical spectra of underdoped BaFe1.89Co0.11As2 that hosts both of magnetic and superconducting orders. The temperature dependent evolution of optical conductivity shows finger prints of the magnetic order and the s-wave nature of the superconducting gaps. Careful inspection on the superconducting state reveals that the two orders compete but coexist in the ground state.","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"21-24"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376653","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}
Pub Date : 2015-12-31DOI: 10.9714/PSAC.2015.17.4.012
S. J. Song, N. Sung, B. Cho, S. Moon
We report on the infrared spectroscopic studies of the normal-state electronic response of rare-earth ternary platinum germanide superconductor La2Pt3Ge5. We analyzed the temperature-dependent optical conductivity spectra using the Drude-Lorentz oscillator model. We found that the two Drude responses with distinct scattering rates are required to explain the charge dynamics at 10 K while a single Drude mode could reproduce the far-infrared conductivity at higher temperatures. Our results indicated the two-band character of the electronic structure and highlighted the disparate temperature evolution of the electrodynamics of the two electronic states.
{"title":"Normal-state charge dynamics of ternary platinum germanide superconductor La2Pt3Ge5","authors":"S. J. Song, N. Sung, B. Cho, S. Moon","doi":"10.9714/PSAC.2015.17.4.012","DOIUrl":"https://doi.org/10.9714/PSAC.2015.17.4.012","url":null,"abstract":"We report on the infrared spectroscopic studies of the normal-state electronic response of rare-earth ternary platinum germanide superconductor La2Pt3Ge5. We analyzed the temperature-dependent optical conductivity spectra using the Drude-Lorentz oscillator model. We found that the two Drude responses with distinct scattering rates are required to explain the charge dynamics at 10 K while a single Drude mode could reproduce the far-infrared conductivity at higher temperatures. Our results indicated the two-band character of the electronic structure and highlighted the disparate temperature evolution of the electrodynamics of the two electronic states.","PeriodicalId":20758,"journal":{"name":"Progress in Superconductivity and Cryogenics","volume":"17 1","pages":"12-15"},"PeriodicalIF":0.3,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71376644","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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