Pub Date : 2025-04-19DOI: 10.1016/j.cryogenics.2025.104078
Gianluca De Marzi , Valentina Corato , Monika Lewandowska
High-temperature superconductors (HTS) are being explored for integration into coil systems for magnetic confinement fusion, due to their ability to extend operational margins in terms of temperature, current, and magnetic field. Recently, a conductor design based on a sector-assembled (SECAS) cable-in-conduit-conductor (CICC) concept was proposed for the innermost layer of the central solenoid (CS) module in the EU-DEMO tokamak. The dynamic nature of plasma scenarios, characterized by rapid variations in current and magnetic fields, induces significant AC losses in the superconducting magnets. These losses can be particularly pronounced during phases like plasma start-up and control operation, where field variations can be significant. In this study, we evaluate the instantaneous power losses — both hysteretic and coupling losses — during a baseline plasma scenario using an analytical model that accurately accounts for the temporal evolution of the magnetic field profile within the innermost layers of the CS1 HTS insert.
{"title":"An analytical framework for computing AC losses in the HTS insert of the EU-DEMO central solenoid","authors":"Gianluca De Marzi , Valentina Corato , Monika Lewandowska","doi":"10.1016/j.cryogenics.2025.104078","DOIUrl":"10.1016/j.cryogenics.2025.104078","url":null,"abstract":"<div><div>High-temperature superconductors (HTS) are being explored for integration into coil systems for magnetic confinement fusion, due to their ability to extend operational margins in terms of temperature, current, and magnetic field. Recently, a conductor design based on a sector-assembled (SECAS) cable-in-conduit-conductor (CICC) concept was proposed for the innermost layer of the central solenoid (CS) module in the EU-DEMO tokamak. The dynamic nature of plasma scenarios, characterized by rapid variations in current and magnetic fields, induces significant AC losses in the superconducting magnets. These losses can be particularly pronounced during phases like plasma start-up and control operation, where field variations can be significant. In this study, we evaluate the instantaneous power losses — both hysteretic and coupling losses — during a baseline plasma scenario using an analytical model that accurately accounts for the temporal evolution of the magnetic field profile within the innermost layers of the CS1 HTS insert.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104078"},"PeriodicalIF":1.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143870661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-17DOI: 10.1016/j.cryogenics.2025.104085
Qiaoyi Du , Gesheng Xiao , Songbo Zhang , Lin Yang , Li Qiao
Superconducting Nb3Sn is pivotal for high-field (>10 T) magnets, where extreme operating currents enable substantial energy storage. Thermal energy rapidly accumulates in localized magnet coil regions during resistive transition (quench) initiation. This localized overheating creates intense thermal gradients where heat concentration in such a confined area leads to accelerated temperature rise, ultimately posing catastrophic risks to the integrity of the high-field superconducting magnet system. This study employs multiscale modeling to analyze temperature-dependent nonlinearities in thermodynamic parameters and transient local thermal stresses induced by quench-driven thermal shock. The study reveals a non-monotonic temperature dependence of thermal conductivity in Nb3Sn, governed by synergistic effects of phonon boundary scattering, Umklapp processes, and multi-mechanism electron scattering. The Debye model accurately predicts the nonlinear temperature dependence of Nb3Sn’s specific heat capacity, following law at cryogenic temperatures, due to phonon energy variations driven by temperature. The thermal expansion coefficient demonstrates nonlinear temperature dependence, with lattice anharmonicity as the dominant mechanism. Furthermore, the temperature sensitivity of d-electron states governs the abnormal elastic behavior of Nb3Sn during its superconducting transition. Employing an equiaxed-grain polycrystalline Nb3Sn model demonstrates that thermal stress intensifies with rising temperature fields during quench, exhibiting irregular distributions arising from variations in grain orientation, morphology, and local temperature. These multiscale simulations provide critical insights for superconducting magnet safety assessments under thermal shock conditions.
{"title":"A trans-scale analysis and computation model for transient local stress in Nb3Sn superconductor under quench-induced thermal shock","authors":"Qiaoyi Du , Gesheng Xiao , Songbo Zhang , Lin Yang , Li Qiao","doi":"10.1016/j.cryogenics.2025.104085","DOIUrl":"10.1016/j.cryogenics.2025.104085","url":null,"abstract":"<div><div>Superconducting Nb<sub>3</sub>Sn is pivotal for high-field (>10 T) magnets, where extreme operating currents enable substantial energy storage. Thermal energy rapidly accumulates in localized magnet coil regions during resistive transition (quench) initiation. This localized overheating creates intense thermal gradients where heat concentration in such a confined area leads to accelerated temperature rise, ultimately posing catastrophic risks to the integrity of the high-field superconducting magnet system. This study employs multiscale modeling to analyze temperature-dependent nonlinearities in thermodynamic parameters and transient local thermal stresses induced by quench-driven thermal shock. The study reveals a non-monotonic temperature dependence of thermal conductivity in Nb<sub>3</sub>Sn, governed by synergistic effects of phonon boundary scattering, Umklapp processes, and multi-mechanism electron scattering. The Debye model accurately predicts the nonlinear temperature dependence of Nb<sub>3</sub>Sn’s specific heat capacity, following <span><math><mrow><msup><mrow><mi>T</mi></mrow><mn>3</mn></msup></mrow></math></span> law at cryogenic temperatures, due to phonon energy variations driven by temperature. The thermal expansion coefficient demonstrates nonlinear temperature dependence, with lattice anharmonicity as the dominant mechanism. Furthermore, the temperature sensitivity of d-electron states governs the abnormal elastic behavior of Nb<sub>3</sub>Sn during its superconducting transition. Employing an equiaxed-grain polycrystalline Nb<sub>3</sub>Sn model demonstrates that thermal stress intensifies with rising temperature fields during quench, exhibiting irregular distributions arising from variations in grain orientation, morphology, and local temperature. These multiscale simulations provide critical insights for superconducting magnet safety assessments under thermal shock conditions.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104085"},"PeriodicalIF":1.8,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143851856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-17DOI: 10.1016/j.cryogenics.2025.104082
Yinghe Qi , Wei Guo
Understanding air propagation and condensation following a catastrophic vacuum break in particle accelerator beamlines cooled by liquid helium is essential for ensuring operational safety. This review summarizes experimental and theoretical work conducted in our cryogenics lab to address this issue. Systematic measurements were performed to study nitrogen gas propagation in uniform copper tubes cooled by both normal liquid helium (He I) and superfluid helium (He II). These experiments revealed a nearly exponential deceleration of the gas front, with stronger deceleration observed in He II-cooled tubes. To interpret these results, a one-dimensional (1D) theoretical model was developed, incorporating gas dynamics, heat transfer, and condensation mechanisms. The model successfully reproduced key experimental observations in the uniform tube system. However, recent experiments involving a bulky copper cavity designed to mimic the geometry of a superconducting radio-frequency (SRF) cavity revealed strong anisotropic flow patterns of nitrogen gas within the cavity, highlighting limitations in extrapolating results from simplified tube geometries to real accelerator beamlines. To address these complexities, we outline plans for systematic studies using tubes with multiple bulky cavities and the development of a two-dimensional (2D) model to simulate gas dynamics in these more intricate configurations. These efforts aim to provide a comprehensive understanding of vacuum breaks in particle accelerators and improve predictive capabilities for their operational safety.
{"title":"Advances in understanding vacuum break dynamics in liquid helium-cooled tubes for accelerator beamline applications","authors":"Yinghe Qi , Wei Guo","doi":"10.1016/j.cryogenics.2025.104082","DOIUrl":"10.1016/j.cryogenics.2025.104082","url":null,"abstract":"<div><div>Understanding air propagation and condensation following a catastrophic vacuum break in particle accelerator beamlines cooled by liquid helium is essential for ensuring operational safety. This review summarizes experimental and theoretical work conducted in our cryogenics lab to address this issue. Systematic measurements were performed to study nitrogen gas propagation in uniform copper tubes cooled by both normal liquid helium (He I) and superfluid helium (He II). These experiments revealed a nearly exponential deceleration of the gas front, with stronger deceleration observed in He II-cooled tubes. To interpret these results, a one-dimensional (1D) theoretical model was developed, incorporating gas dynamics, heat transfer, and condensation mechanisms. The model successfully reproduced key experimental observations in the uniform tube system. However, recent experiments involving a bulky copper cavity designed to mimic the geometry of a superconducting radio-frequency (SRF) cavity revealed strong anisotropic flow patterns of nitrogen gas within the cavity, highlighting limitations in extrapolating results from simplified tube geometries to real accelerator beamlines. To address these complexities, we outline plans for systematic studies using tubes with multiple bulky cavities and the development of a two-dimensional (2D) model to simulate gas dynamics in these more intricate configurations. These efforts aim to provide a comprehensive understanding of vacuum breaks in particle accelerators and improve predictive capabilities for their operational safety.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104082"},"PeriodicalIF":1.8,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143859885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-17DOI: 10.1016/j.cryogenics.2025.104083
A. Schillaci , R. Agustsson , R. Berry , Y.C. Chen , C. Edwards , M. Henry , S.V. Kutsaev , T. Nicol , J. Pena , J.C. Thangaraj
Superconducting RF (SRF) accelerators have the potential to be more profitable in comparison with normally conducting accelerators, as long they can be made compact, achieve operational simplicity, autonomy, transportability, satisfactory energy efficiency, as well as have reasonable costs. The development of SRF technologies such as Nb3Sn coating, conductively-cooled resonators, and high-capacity liquid-helium-free cryocoolers made SRF accelerators mobile and energetically and economically efficient at a beam power of tens of kW. One of the key elements of such an accelerator is the cryomodule, which must have minimal thermal losses to enable operation from low power cryoheads and enable conductive cooling of SRF resonator. In this paper we present the design and test results of a compact cryomodule for an industrial stand-alone SRF linear accelerator prototype, based on 650 MHz elliptical resonators, being developed at Fermi National Accelerator Laboratory.
{"title":"Compact cryomodule for mobile stand-alone superconducting industrial accelerators","authors":"A. Schillaci , R. Agustsson , R. Berry , Y.C. Chen , C. Edwards , M. Henry , S.V. Kutsaev , T. Nicol , J. Pena , J.C. Thangaraj","doi":"10.1016/j.cryogenics.2025.104083","DOIUrl":"10.1016/j.cryogenics.2025.104083","url":null,"abstract":"<div><div>Superconducting RF (SRF) accelerators have the potential to be more profitable in comparison with normally conducting accelerators, as long they can be made compact, achieve operational simplicity, autonomy, transportability, satisfactory energy efficiency, as well as have reasonable costs. The development of SRF technologies such as Nb<sub>3</sub>Sn coating, conductively-cooled resonators, and high-capacity liquid-helium-free cryocoolers made SRF accelerators mobile and energetically and economically efficient at a beam power of tens of kW. One of the key elements of such an accelerator is the cryomodule, which must have minimal thermal losses to enable operation from low power cryoheads and enable conductive cooling of SRF resonator. In this paper we present the design and test results of a compact cryomodule for an industrial stand-alone SRF linear accelerator prototype, based on 650 MHz elliptical resonators, being developed at Fermi National Accelerator Laboratory.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104083"},"PeriodicalIF":1.8,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143870660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-17DOI: 10.1016/j.cryogenics.2025.104081
Erik Walcz , Csaba Budai
Atomic Diffusion Additive Manufacturing (ADAM) represents cutting-edge technology in the field of cost-effective additive manufacturing, while the vacuum tightness and thermal properties of these materials are not fully measured, especially at low, cryogenic temperatures. This study investigates the viability of utilizing ADAM for producing components intended for cryogenic heat transfer in vacuum. In this paper I will present the CryPT-ON (Cryogenic Performance Test) cryostat at the Fusion Plasma Physics Department of HUN-REN Centre for Energy Research, the specific experimental setup for thermal conductivity, diffusivity measurement and the 3D printed samples with X-ray fluorescence (XRF) and Scanning Electron Microscope (SEM) measurement to determine the material composition and have a better understanding of this special material and printing technology.
{"title":"Cryogenic properties of copper produced by Atomic Diffusion Additive Manufacturing (ADAM)","authors":"Erik Walcz , Csaba Budai","doi":"10.1016/j.cryogenics.2025.104081","DOIUrl":"10.1016/j.cryogenics.2025.104081","url":null,"abstract":"<div><div>Atomic Diffusion Additive Manufacturing (ADAM) represents cutting-edge technology in the field of cost-effective additive manufacturing, while the vacuum tightness and thermal properties of these materials are not fully measured, especially at low, cryogenic temperatures. This study investigates the viability of utilizing ADAM for producing components intended for cryogenic heat transfer in vacuum. In this paper I will present the CryPT-ON (Cryogenic Performance Test) cryostat at the Fusion Plasma Physics Department of HUN-REN Centre for Energy Research, the specific experimental setup for thermal conductivity, diffusivity measurement and the 3D printed samples with X-ray fluorescence (XRF) and Scanning Electron Microscope (SEM) measurement to determine the material composition and have a better understanding of this special material and printing technology.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104081"},"PeriodicalIF":1.8,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143855861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1016/j.cryogenics.2025.104086
Zhen Geng , Yemao Han , Zhicong Miao , Liancheng Xie , Di Jiang , Mingyue Jiang , Yuqiang Zhao , Haojian Su , Rongjin Huang , Laifeng Li
Accurate low-temperature measurements are crucial in fields such as high energy physics, nuclear engineering, and aerospace. ZrNxOy thin films exhibit resistance highly sensitive to temperature variations due to meticulously controlled growth parameters. The grain size of these films, significantly influences their low-temperature electrical transport properties, a relationship that remains insufficiently explored. In this study, the effects of grain size evolution by controlling deposition temperature are investigated, focusing on the temperature dependence of resistivity and magnetoresistance behavior in a low-temperature strong magnetic field. As grain size decreases, room temperature resistivity, the intensity of transverse phonon modes, and disorder all increased. The electron − phonon interactions strength weakens as the grain size decreases. The w(T) function, which is the logarithmic derivative of electrical conductance with respect to temperature, exhibits anomalous behavior in the temperature range of 300 K−100 K (i.e., dw/dT > 0), contrasting with the negative slope observed from 100 K to 2 K. By analyzing w(T), it is determined that multiple conduction mechanisms overlap in this series of samples. At 2 K, 0.2 % positive saturated magnetoresistance shows in weak magnetic fields, transitioning to unsaturated negative magnetoresistance as the magnetic field increases until 9 T, is consistent with the correlation effects and spin-flip hopping theory. Meanwhile, positive magnetoresistance is unaffected by grain size, whereas negative magnetoresistance weakens as grain size increases. Grain size evolution effect offers an approach for evaluating and developing high-sensitivity thermometers for a wide temperature range.
精确的低温测量在高能物理、核工程和航空航天等领域至关重要。ZrNxOy 薄膜由于生长参数受到严格控制，其电阻对温度变化非常敏感。这些薄膜的晶粒大小对其低温电传输特性有显著影响，但这一关系仍未得到充分探索。本研究通过控制沉积温度，研究了晶粒尺寸演变的影响，重点是低温强磁场下电阻率和磁阻行为的温度依赖性。随着晶粒尺寸的减小，室温电阻率、横向声子模式强度和无序度都有所增加。电子-声子相互作用强度随着晶粒尺寸的减小而减弱。w(T) 函数是电导率随温度变化的对数导数，在 300 K-100 K 的温度范围内表现出异常行为（即 dw/dT >0），与 100 K 至 2 K 期间观察到的负斜率形成鲜明对比。在 2 K 时，0.2% 的正饱和磁阻出现在弱磁场中，随着磁场的增大直至 9 T，过渡到不饱和负磁阻，这与相关效应和自旋翻转跳跃理论是一致的。同时，正磁阻不受晶粒尺寸的影响，而负磁阻则随着晶粒尺寸的增大而减弱。晶粒尺寸演化效应为评估和开发宽温度范围的高灵敏度温度计提供了一种方法。
{"title":"Grain size effects on low temperature electrical transport in sputtered ZrNxOy thin films","authors":"Zhen Geng , Yemao Han , Zhicong Miao , Liancheng Xie , Di Jiang , Mingyue Jiang , Yuqiang Zhao , Haojian Su , Rongjin Huang , Laifeng Li","doi":"10.1016/j.cryogenics.2025.104086","DOIUrl":"10.1016/j.cryogenics.2025.104086","url":null,"abstract":"<div><div>Accurate low-temperature measurements are crucial in fields such as high energy physics, nuclear engineering, and aerospace. ZrN<em><sub>x</sub></em>O<em><sub>y</sub></em> thin films exhibit resistance highly sensitive to temperature variations due to meticulously controlled growth parameters. The grain size of these films, significantly influences their low-temperature electrical transport properties, a relationship that remains insufficiently explored. In this study, the effects of grain size evolution by controlling deposition temperature are investigated, focusing on the temperature dependence of resistivity and magnetoresistance behavior in a low-temperature strong magnetic field. As grain size decreases, room temperature resistivity, the intensity of transverse phonon modes, and disorder all increased. The electron − phonon interactions strength weakens as the grain size decreases. The <em>w</em>(<em>T</em>) function, which is the logarithmic derivative of electrical conductance with respect to temperature, exhibits anomalous behavior in the temperature range of 300 K−100 K (i.e., d<em>w</em>/d<em>T</em> > 0), contrasting with the negative slope observed from 100 K to 2 K. By analyzing <em>w</em>(<em>T</em>), it is determined that multiple conduction mechanisms overlap in this series of samples. At 2 K, 0.2 % positive saturated magnetoresistance shows in weak magnetic fields, transitioning to unsaturated negative magnetoresistance as the magnetic field increases until 9 T, is consistent with the correlation effects and spin-flip hopping theory. Meanwhile, positive magnetoresistance is unaffected by grain size, whereas negative magnetoresistance weakens as grain size increases. Grain size evolution effect offers an approach for evaluating and developing high-sensitivity thermometers for a wide temperature range.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104086"},"PeriodicalIF":1.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1016/j.cryogenics.2025.104079
Roman Kolevatov, Joe Wiedemann, Dmitrii Trunin, Joelle-Marie Begin, Nate Otto, Lyman Page, Saptarshi Chaudhuri
We describe a passive heat switch based on a commercial pyrolytic graphite sheet. Measurements of the thermal conductivity of the graphite are presented, confirming a large difference between room temperature and ≈4 K. The implementation of a graphite heat switch in a cryostat operating a 3He/4He sorption refrigerator is demonstrated.
{"title":"Passive pyrolytic graphite heat switch for sub-Kelvin coolers","authors":"Roman Kolevatov, Joe Wiedemann, Dmitrii Trunin, Joelle-Marie Begin, Nate Otto, Lyman Page, Saptarshi Chaudhuri","doi":"10.1016/j.cryogenics.2025.104079","DOIUrl":"10.1016/j.cryogenics.2025.104079","url":null,"abstract":"<div><div>We describe a passive heat switch based on a commercial pyrolytic graphite sheet. Measurements of the thermal conductivity of the graphite are presented, confirming a large difference between room temperature and ≈4 K. The implementation of a graphite heat switch in a cryostat operating a <sup>3</sup>He/<sup>4</sup>He sorption refrigerator is demonstrated.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104079"},"PeriodicalIF":1.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143842468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1016/j.cryogenics.2025.104084
G.Q. Qiao , H. Zhang , J. Jiang , F.G. Cai , D. Li , X.S. Yang , Y. Zhao
CORC (Conductor on Round Core) is considered one of the most promising superconducting cable/conductor structures for large-scale applications particularly in fusion magnets, owing to its stable mechanical structure, high current-carrying density, and low AC losses. The utilization of an equivalent circuit model has been instrumental in studying the current distribution within HTS conductors. In the traditional CORC equivalent circuit model, the equivalent inductances are typically set at fixed values. However, given that monitoring current distribution within the tape and between layers is crucial, assessing whether changes in contact resistance could lead to alterations in overall inductance and whether radial currents might cause irreversible damage to the conductor during operation becomes imperative. This study has developed an equivalent circuit model based on a CORC-like structure, starting from a simple straight CORC conductor, and its accuracy has been validated. Through this model, the inductance value of a complex multi-layer CORC configuration has been calculated. When the charging current exceeds 0.7Ic, the inductance of the non-insulating CORC experiences a sudden change. By examining variations in inductance values, it is possible to infer the presence of interlayer currents within the CORC during transient responses. Furthermore, discussions encompass the current flow direction and trends of different CORC specifications during on–off current scenarios, exploring whether current transmission occurs in non-superconducting layers when the CORC is subjected to high currents, determining potential abrupt changes in overall inductance, and assessing the risk of conductor damage during discharge.
由于其稳定的机械结构、高载流密度和低交流损耗，CORC（圆芯导体）被认为是最有希望大规模应用于聚变磁体的超导电缆/导体结构之一。等效电路模型的使用有助于研究 HTS 导体内部的电流分布。在传统的 CORC 等效电路模型中，等效电感通常设置为固定值。然而，由于监测带内和层间的电流分布至关重要，因此评估接触电阻的变化是否会导致整体电感的改变，以及径向电流是否会在运行过程中对导体造成不可逆转的损坏就变得十分必要。本研究从简单的直型 CORC 导体出发，建立了基于 CORC 类结构的等效电路模型，并验证了其准确性。通过该模型，计算出了复杂多层 CORC 结构的电感值。当充电电流超过 0.7Ic 时，非绝缘 CORC 的电感值会发生突变。通过研究电感值的变化，可以推断出在瞬态响应期间 CORC 内是否存在层间电流。此外，讨论还包括不同规格 CORC 在通断电流情况下的电流流向和趋势，探索 CORC 在承受大电流时电流是否会在非超导层中传输，确定整体电感的潜在突变，以及评估放电过程中导体损坏的风险。
{"title":"Research on discharged unsteady response of straight CORC based on the equivalent circuit model","authors":"G.Q. Qiao , H. Zhang , J. Jiang , F.G. Cai , D. Li , X.S. Yang , Y. Zhao","doi":"10.1016/j.cryogenics.2025.104084","DOIUrl":"10.1016/j.cryogenics.2025.104084","url":null,"abstract":"<div><div>CORC (Conductor on Round Core) is considered one of the most promising superconducting cable/conductor structures for large-scale applications particularly in fusion magnets, owing to its stable mechanical structure, high current-carrying density, and low AC losses. The utilization of an equivalent circuit model has been instrumental in studying the current distribution within HTS conductors. In the traditional CORC equivalent circuit model, the equivalent inductances are typically set at fixed values. However, given that monitoring current distribution within the tape and between layers is crucial, assessing whether changes in contact resistance could lead to alterations in overall inductance and whether radial currents might cause irreversible damage to the conductor during operation becomes imperative. This study has developed an equivalent circuit model<!--> <!-->based on a CORC-like structure, starting from a simple straight CORC conductor, and its accuracy has been validated. Through this model, the inductance value of a complex multi-layer CORC configuration has been calculated. When the charging current exceeds 0.7<em>I</em><sub>c</sub>, the inductance of the non-insulating CORC experiences a sudden change. By examining variations in inductance values, it is possible to infer the presence of interlayer currents within the CORC during transient responses. Furthermore, discussions encompass the current flow direction and trends of different CORC specifications during on–off current scenarios, exploring whether current transmission occurs in non-superconducting layers when the CORC is subjected to high currents, determining potential abrupt changes in overall inductance, and assessing the risk of conductor damage during discharge.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104084"},"PeriodicalIF":1.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143851695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, a suitable numerical methodology to predict the thermo-fluid-dynamics within self-pressurized cryogenic tanks is proposed. A comparison towards experimental results of a self-pressurization test case in a ground-based, liquid nitrogen (N2) tank, subject to an entering heat transfer rate, is carried out in order to select the most promising numerical methodology. The effect of different numerical models and parameters is studied, always adopting the Volume-of-Fluid (VOF) method for tracing the two-phase fluid interface and the Lee model for calculating the phase transition. In particular, the numerical results show that, for the studied test case: (1) the prediction of the pressure rise is not strongly affected by the Lee model parameters, even if they may affect the numerical stability of the computation; (2) the use of a conjugate heat transfer model is necessary in order to represent the liquid temperature stratification close to the free-surface, as the wall heat flux paths play a fundamental role in the heat distribution between the liquid phase and the ullage; (3) a laminar model is more adequate as the turbulent model overestimates convective recirculations in the liquid phase, leading to excessive mixing and resulting in failure to describe temperature stratification close to the free-surface, confirming the results of other papers in the literature; (4) the experimental uncertainty on the entering heat transfer rate may substantially affect the numerical predictions.
{"title":"Setup of a numerical methodology for the study of self-pressurization of cryogenic tanks","authors":"Francesca Rossetti , Marco Pizzarelli , Rocco Carmine Pellegrini , Enrico Cavallini , Matteo Bernardini","doi":"10.1016/j.cryogenics.2025.104059","DOIUrl":"10.1016/j.cryogenics.2025.104059","url":null,"abstract":"<div><div>In this paper, a suitable numerical methodology to predict the thermo-fluid-dynamics within self-pressurized cryogenic tanks is proposed. A comparison towards experimental results of a self-pressurization test case in a ground-based, liquid nitrogen (N<sub>2</sub>) tank, subject to an entering heat transfer rate, is carried out in order to select the most promising numerical methodology. The effect of different numerical models and parameters is studied, always adopting the Volume-of-Fluid (VOF) method for tracing the two-phase fluid interface and the Lee model for calculating the phase transition. In particular, the numerical results show that, for the studied test case: (1) the prediction of the pressure rise is not strongly affected by the Lee model parameters, even if they may affect the numerical stability of the computation; (2) the use of a conjugate heat transfer model is necessary in order to represent the liquid temperature stratification close to the free-surface, as the wall heat flux paths play a fundamental role in the heat distribution between the liquid phase and the ullage; (3) a laminar model is more adequate as the turbulent model overestimates convective recirculations in the liquid phase, leading to excessive mixing and resulting in failure to describe temperature stratification close to the free-surface, confirming the results of other papers in the literature; (4) the experimental uncertainty on the entering heat transfer rate may substantially affect the numerical predictions.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"147 ","pages":"Article 104059"},"PeriodicalIF":1.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143870689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since the heat leak through the cryogenic vacuum chamber is a critical issue for superconducting devices, especially those with a large surface-to-volume ratio, such as a long cable, we measured the heat leak of the cryogenic co-axial double pipes for the superconducting cable in the past 20 years. We also estimate the heat leak using the radiative heat transfer equation for the cryogenic pipe. We can fix the surface area of the pipes from the design, but we have assumed the emissivity value of those surfaces. Therefore, we used the Fourier transform infrared spectroscopy (FTIR) and the optical integrating sphere to measure the reflectivity of various metal surfaces in the infrared wavelength range and estimate the effective emissivity using the Plank equation for the weighted average of the emissivity, a function of the wavelength. Finally, we estimate the heat leak utilizing the heat transfer equation and compare the experimental data. Since these two heat leaks are consistent, the optical measurement can potentially evaluate the surface performance of the cryogenic pipes. We also discuss the error of the optical measurements.
{"title":"Heat-transfer dependence of pipe surface materials in cryogenic double pipes","authors":"Sataro Yamaguchi , Masae Kanda , Yury Ivanov , Hirofumi Watanabe , Shuichiro Tsubota , Kazuaki Matsumoto , Yasuhiro Harada","doi":"10.1016/j.cryogenics.2025.104064","DOIUrl":"10.1016/j.cryogenics.2025.104064","url":null,"abstract":"<div><div>Since the heat leak through the cryogenic vacuum chamber is a critical issue for superconducting devices, especially those with a large surface-to-volume ratio, such as a long cable, we measured the heat leak of the cryogenic co-axial double pipes for the superconducting cable in the past 20 years. We also estimate the heat leak using the radiative heat transfer equation for the cryogenic pipe. We can fix the surface area of the pipes from the design, but we have assumed the emissivity value of those surfaces. Therefore, we used the Fourier transform infrared spectroscopy (FTIR) and the optical integrating sphere to measure the reflectivity of various metal surfaces in the infrared wavelength range and estimate the effective emissivity using the Plank equation for the weighted average of the emissivity, a function of the wavelength. Finally, we estimate the heat leak utilizing the heat transfer equation and compare the experimental data. Since these two heat leaks are consistent, the optical measurement can potentially evaluate the surface performance of the cryogenic pipes. We also discuss the error of the optical measurements.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"149 ","pages":"Article 104064"},"PeriodicalIF":1.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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