Slow Propagation Velocity Research Articles

Quench Protection of DI-BSCCO Coil

Quench protection is one of the most important requirements for the practical application of high-temperature-superconducting (HTS) coils. Quench protection requires that early detection of a developing quench event is followed by rapid reduction of the operating current. However, such quench detection is very difficult because HTS wire produces heat only locally due to the very slow propagation velocity of a normal zone. Excellent high voltage insulation performance is required if the current is to be reduced rapidly in a large-scale superconducting application with very large inductance. Thus it is important to investigate the behavior of coils with various decay time constants, and to detect voltages on very short time scales. This goal remains to be achieved. In the present study we built test coil and a full-scale pole coil for a 20 MW motor for use in experiments on quench protection, and parameterized the relation between the decay time constant and the detecting voltage, using a conventional balance circuit to detect the quench, which was generated by gradually raising the temperature of the coils. The results verify that a balance circuit can be used for quench detection. For example, when the current decay time constant is 4seconds, the test coil can be protected even with a detecting voltage of 0.15 volts, despite a significant heat production rate of 126W. We also confirmed that the full-scale pole coil, with a decay time constant of 20seconds, can be protected with a detecting voltage of 0.06V.

Thermal conductivity and dielectric properties of a TiO2-based electrical insulator for use with high temperature superconductor-based magnets

Quench protection is a remaining challenge impeding the implementation of high temperature superconductor (HTS)-based magnet applications. This is due primarily to the slow normal zone propagation velocity (NZPV) observed in Bi2Sr2CaCu2OX (Bi2212) and (RE)Ba2Cu3O7 − x (REBCO) systems. Recent computational and experimental findings reveal significant improvements in turn-to-turn NZPV, resulting in a magnet that is more stable and easier to protect through three-dimensional normal zone growth (Phillips M 2009; Ishmael S et al 2013 IEEE Trans. Appl. Supercond. 23 7201311). These improvements are achieved by replacing conventional insulation materials, such as Kapton and mullite braid, with a thin, thermally conducting, electrically-insulating ceramic oxide coating. This paper reports on the temperature-dependent thermal properties, electrical breakdown limits and microstructural characteristics of a titanium oxide (TiO2) insulation and a doped-TiO2-based proprietary insulation (doped-TiO2) shown previously to enhance quench behavior (Ishmael S et al 2013 IEEE Trans. Appl. Supercond. 23 7201311). Breakdown voltages at 77 K ranging from ∼1.5 kV to over 5 kV are reported. At 4.2 K, the TiO2 increases the thermal conductivity of polyimide by about a factor of 10. With the addition of a dopant, thermal conductivity is increased by an additional 13%, and a high temperature heat treatment increases it by nearly an additional 100%. Similar increases are observed at 77 K and room temperature. These results are understood in the context of the various microstructures observed.

Novel electrocardiographic pre-hospital salvage score outperforms reperfusion delay for prediction of left ventricular function in patients with ST-elevation myocardial infarction

ventricle not only on the QRS complex, but also on the ST segment. In myocardial infarction a localized slowing of impulse propagation—the periinfarction block refers to an electrocardiographic abnormality caused by delayed activation of the myocardium in the affected region. In this study we simulated the effects of localized changes in impulse propagation on the QRS and ST-segment patterns, using computer modeling. Material and methods: The model defines the geometry of cardiac ventricles analytically as parts of ellipsoids and allows to change the velocity of impulse propagation in the myocardium. The following changes were introduced in anteroseptal and posterolateral locations: intramural electrically inactive area (infarct), encircled by a transmural area with slowed impulse propagation velocity (peri-infarction block). The effects of sole infarct and peri-infarction blocks, as well the effects of their combinations on the QRS complex and the ST segment are presented. Results: A sole intramural infarct caused QRS changes typical for corresponding locations which were further considerably modified by slowed impulse propagation velocity in the surrounding area. Additionally, the areas of slowed impulse propagation velocity in both locations caused ST-segment deviations, shifting the ST segment toward the affected areas. Conclusion: Using computer modeling we showed that the localized slowing in impulse propagation (peri-infarction block) not only modified the QRS complex, but produced also changes in the ST segment that are consistent with changes that are usually interpreted as effect of the “injury current.”

Transient myocardial ischemia among non-STEMI and unstable angina patients treated with invasive versus conservative treatment

ventricle not only on the QRS complex, but also on the ST segment. In myocardial infarction a localized slowing of impulse propagation—the periinfarction block refers to an electrocardiographic abnormality caused by delayed activation of the myocardium in the affected region. In this study we simulated the effects of localized changes in impulse propagation on the QRS and ST-segment patterns, using computer modeling. Material and methods: The model defines the geometry of cardiac ventricles analytically as parts of ellipsoids and allows to change the velocity of impulse propagation in the myocardium. The following changes were introduced in anteroseptal and posterolateral locations: intramural electrically inactive area (infarct), encircled by a transmural area with slowed impulse propagation velocity (peri-infarction block). The effects of sole infarct and peri-infarction blocks, as well the effects of their combinations on the QRS complex and the ST segment are presented. Results: A sole intramural infarct caused QRS changes typical for corresponding locations which were further considerably modified by slowed impulse propagation velocity in the surrounding area. Additionally, the areas of slowed impulse propagation velocity in both locations caused ST-segment deviations, shifting the ST segment toward the affected areas. Conclusion: Using computer modeling we showed that the localized slowing in impulse propagation (peri-infarction block) not only modified the QRS complex, but produced also changes in the ST segment that are consistent with changes that are usually interpreted as effect of the “injury current.”

QRS complex and ST segment manifestations of ventricular ischemia: The effect of regional slowing of ventricular activation

ObjectiveReduction or interruption of the blood supply to myocardium due to occlusion of coronary artery and consequent ischemia leads to changes of electrogenesis: changes in morphology and duration of action potentials and slowing of conduction velocity in the affected area. In this study we simulated the effects of localized changes in depolarization sequence on the QRS and ST segment patterns, using computer modeling. MethodsThe model defines the geometry of cardiac ventricles analytically as parts of ellipsoids and allows changing the velocity of impulse propagation in the myocardium. An intramural electrically inactive area encircled by a transmural area with slowed impulse propagation velocity was introduced in anteroseptal and inferior locations. The effects on the QRS complex and the ST segment of the 12-lead electrocardiogram are presented. ResultsThe intramural electrically inactive area caused QRS changes typical for corresponding locations of a myocardial infarction observed in patients, which were further considerably modified by slowed impulse propagation velocity in the surrounding area. Additionally, areas of slowed impulse propagation velocity led to ST segment deviations in the “reciprocal” leads, shifting the ST segment towards the affected areas. ConclusionUsing computer modeling we showed that the localized alteration of impulse propagation not only modified the QRS complex, but produced also changes in the ST segment consistent with changes which are usually interpreted as the effect of “injury current”.

Feature extraction of ECG signal using a support vector machine

Additionally, areas of slowed impulse propagation velocity led to ST segment deviations in the “reciprocal” leads, shifting the ST segment change towards the affected areas. Conclusion: Using computer modeling we showed that the localized alteration of impulse propagation modified not only the QRS complex, but produced also changes in the ST segment consistent with changes which are usually interpreted as the effect of “injury current”. Supported by the grant VEGA 2/0131/13.

Hybrid Model of Quench Propagation in Coated Conductors Applied to Fault Current Limiter Design

In order to help in designing more compact fault current limiters based on coated conductors, we recently developed a hybrid model of the quench propagation in such conductors. This model combines the finite element method to study the thermal propagation and analytical calculation of heat generation. The results obtained with this model are in very good agreement with the experiments, without the need for using free parameters for adjustment. Simulations demonstrate that even slight variations of the conductor characteristics have great influence on the temperature profile along the tape during the limitation phase, due to the slow normal zone propagation velocity. 2-D parametric studies are conducted with the aim of improving the temperature uniformity by varying some characteristics of the layers of the coated conductors. 3-D simulations on a wider scale are conducted to demonstrate how the temperature uniformity could be improved further in fault current limiters by using adapted meander geometries.

Tu2068 Spatial Aliasing of Colonic Manometry Data: What Have We Been Missing or Mislabeling?

While colonic manometry has helped to defined dysmotility in patients with functional colonic or anorectal disorders, identification of specific manometric markers that assist in subtyping these disorders remains elusive. Typically colonic manometry is recorded with sensor spacing ≥10cm, however we have shown that colonic propagated sequences (PS) can extend over segments as short as 3-5cm(1). It is likely, therefore that traditional manometry is overlooking potentially relevant motor patterns. Aim: To determine the influence of pressure sensor spacing on our ability to accurately identify colonic motility patterns. Method: A fibre-optic catheter containing 72-90 sensors spaced at 1cm intervals was placed colonoscopically to the caecum in 11 patients with scintigraphically confirmed slow transit constipation. Controls comprised 11 patients with neurogenic fecal incontinence and 9 healthy subjects. From each of these recordings a 2hr section of trace was selected to assess motor response to either the response to a 1000kCal meal (healthy controls) or the colonic response to sacral nerve stimulation (patient population). Each data set was analysed in 6 different ways by sub-sampling different sets of the full array to simulate inter-recording site distances of 10, 7, 5, 3, 2 and 1cm. In blinded fashion, in each manometric trace antegrade and retrograde propagating sequences (PS) were identified. Against the 1cm spaced data (gold standard), we compared all the PSs identified at each test sensor spacing (2-10cm). Results: In all three groups as sensor spacing increased; i) the frequency of identified antegrade and retrograde PSs decreased; , 5% of the propagating activity observed at 1cm spacing could be seen at 10cm (P , 0.0001); ii) the ratio of antegrade to retrograde PSs increased (P , 0.0001), from pre-dominantly retrograde activity at 1cm spacing to predominantly antegrade at 10cm spacing; & iii) the number of falsely labeled PSs (when compared to 1cm data) increased (P , 0.003). At a sensor spacing .5cm the only PSs that can be reliably detected are those of high amplitude and slow propagation velocity; (real vs false amplitude: 138 vs 29 (+/12 SEM) mmHg; real vs false velocity: 5 vs 20 (+/3 SEM) mm/s). Conclusions: 1) Inadequate proximity between recording sites (resolution) results in both missed and mis-labeling of colonic propagating sequences. 2) An inter-recording site distance . 5cm grossly misrepresents colonic manometric patterns. 3) High resolution colonic manometry is likely to assist in the identification of diagnostically relevant manometric markers of colonic motor disorders. Supported by NHMRC and CSIRO Australia (1) Dinning PG et al. Br J Surg. 99: 1002-1010.

Tu2069 Characterization of the Colonic Meal Response in Healthy Controls and Patients With Slow Transit Constipation: Initial Results From Fibre-Optic High-Resolution Manometry

While colonic manometry has helped to defined dysmotility in patients with functional colonic or anorectal disorders, identification of specific manometric markers that assist in subtyping these disorders remains elusive. Typically colonic manometry is recorded with sensor spacing ≥10cm, however we have shown that colonic propagated sequences (PS) can extend over segments as short as 3-5cm(1). It is likely, therefore that traditional manometry is overlooking potentially relevant motor patterns. Aim: To determine the influence of pressure sensor spacing on our ability to accurately identify colonic motility patterns. Method: A fibre-optic catheter containing 72-90 sensors spaced at 1cm intervals was placed colonoscopically to the caecum in 11 patients with scintigraphically confirmed slow transit constipation. Controls comprised 11 patients with neurogenic fecal incontinence and 9 healthy subjects. From each of these recordings a 2hr section of trace was selected to assess motor response to either the response to a 1000kCal meal (healthy controls) or the colonic response to sacral nerve stimulation (patient population). Each data set was analysed in 6 different ways by sub-sampling different sets of the full array to simulate inter-recording site distances of 10, 7, 5, 3, 2 and 1cm. In blinded fashion, in each manometric trace antegrade and retrograde propagating sequences (PS) were identified. Against the 1cm spaced data (gold standard), we compared all the PSs identified at each test sensor spacing (2-10cm). Results: In all three groups as sensor spacing increased; i) the frequency of identified antegrade and retrograde PSs decreased; , 5% of the propagating activity observed at 1cm spacing could be seen at 10cm (P , 0.0001); ii) the ratio of antegrade to retrograde PSs increased (P , 0.0001), from pre-dominantly retrograde activity at 1cm spacing to predominantly antegrade at 10cm spacing; & iii) the number of falsely labeled PSs (when compared to 1cm data) increased (P , 0.003). At a sensor spacing .5cm the only PSs that can be reliably detected are those of high amplitude and slow propagation velocity; (real vs false amplitude: 138 vs 29 (+/12 SEM) mmHg; real vs false velocity: 5 vs 20 (+/3 SEM) mm/s). Conclusions: 1) Inadequate proximity between recording sites (resolution) results in both missed and mis-labeling of colonic propagating sequences. 2) An inter-recording site distance . 5cm grossly misrepresents colonic manometric patterns. 3) High resolution colonic manometry is likely to assist in the identification of diagnostically relevant manometric markers of colonic motor disorders. Supported by NHMRC and CSIRO Australia (1) Dinning PG et al. Br J Surg. 99: 1002-1010.

Experimental and Automated Analysis Techniques for High-resolution Electrical Mapping of Small Intestine Slow Wave Activity

Background/AimsSmall intestine motility is governed by an electrical slow wave activity, and abnormal slow wave events have been associated with intestinal dysmotility. High-resolution (HR) techniques are necessary to analyze slow wave propagation, but progress has been limited by few available electrode options and laborious manual analysis. This study presents novel methods for in vivo HR mapping of small intestine slow wave activity.MethodsRecordings were obtained from along the porcine small intestine using flexible printed circuit board arrays (256 electrodes; 4 mm spacing). Filtering options were compared, and analysis was automated through adaptations of the falling-edge variable-threshold (FEVT) algorithm and graphical visualization tools.ResultsA Savitzky-Golay filter was chosen with polynomial-order 9 and window size 1.7 seconds, which maintained 94% of slow wave amplitude, 57% of gradient and achieved a noise correction ratio of 0.083. Optimized FEVT parameters achieved 87% sensitivity and 90% positive-predictive value. Automated activation mapping and animation successfully revealed slow wave propagation patterns, and frequency, velocity, and amplitude were calculated and compared at 5 locations along the intestine (16.4 ± 0.3 cpm, 13.4 ± 1.7 mm/sec, and 43 ± 6 µV, respectively, in the proximal jejunum).ConclusionsThe methods developed and validated here will greatly assist small intestine HR mapping, and will enable experimental and translational work to evaluate small intestine motility in health and disease.

Effects of high magnetic field on the quench behavior of Bi2Sr2CaCu2Ox coils at 4.2 K

The development of high field superconducting magnets using high temperature superconductors (HTSs) is progressing for high energy physics, nuclear magnetic resonance and energy storage applications. Yet the key issue of quench protection remains unresolved, primarily due to the slow normal zone propagation velocity (NZPV) in HTS magnets. High magnetic field may affect the quench behavior through two opposing effects: increased NZPV may result due to reduced critical temperature and current sharing temperature, but decreased NZPV may result due to reduced critical current density and thus operating current. At present it is unclear which effect dominates. Here, a series of quench experiments at high magnetic field on multilayer wind-and-react Bi2Sr2CaCu2Ox (Bi2212) coils addresses this question. The two- and three-dimensional quench behavior is investigated in a magnetic field up to 20 T at 4.2 K. With increasing magnetic field, the minimum quench energy decreases significantly. The NZPV also decreases with magnetic field, but only up to about 8 T. For magnetic fields above 8 T, the NZPV is independent of magnetic field up to at least 20 T. Thus, at low field the NZPV is dominated by the decreasing critical current density, whereas at higher magnetic field the competing effects of decreasing critical current density and decreasing temperature margin offset each other.

Slow esophageal propagation velocity: association with dysphagia for solids

Spastic disorders of the esophagus, associated with rapid esophageal propagation velocity, are classically associated with dysphagia and/or chest pain. The aim of this study was to characterize patients with slow esophageal propagation velocity (SPV) on high-resolution esophageal manometry (HRM). A review of patients undergoing HRM was conducted during 1-year study period. Patients with achalasia, aperistalsis, and diffuse esophageal spasm were excluded. Patients with contractile front velocity (CFV) ≤ 2.3 cm s(-1) were defined as having SPV, whereas normal propagation velocity (NPV) was defined as ≥ 2.6 cm s(-1). A composite isobaric contour of all swallows for each patient was generated to determine composite distal contraction latency (cDL). A total of 650 HRMs were reviewed and 552 met inclusion criteria. 173 patients had SPV and 339 had NPV. There was a greater female predominance in the SPV group compared with NPV (75.7%vs 66.4%, P = 0.03). Patients in the SPV group reported more dysphagia for solids (66.3%vs 53.3%; P = 0.004) and nausea (68.6%vs 59.0%; P = 0.04) than NPV group. Dysphagia for solids was the only symptom significantly associated with SPV group (OR = 2.21, CI = 1.21-4.02; P = .01). There was a negative correlation between CFV and cDL, r = -0.494, P < 0.001. Patients with SPV have a higher prevalence of dysphagia for solids and nausea when compared with NPV. Dysphagia for solids was the only symptom significantly associated with SPV group. Thus, abnormal esophageal propagation velocity (both slow and rapid) is associated with dysphagia.

A Hierarchical Three-Dimensional Multiscale Electro–Magneto–Thermal Model of Quenching in $\hbox{REBa}_{2}\hbox{Cu}_{3}\hbox{O}_{7 - \delta}$ Coated-Conductor-Based Coils

Quench detection and protection in REBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-δ</sub> (REBCO) coated conductor (CC)-based superconducting magnets is difficult due to slow normal zone propagation velocity and the multilayer composite architecture of the conductor. To design effective quench detection and protection methods, it is essential to know the electrical, thermal, and structural behavior during the quench at multiple length scales ranging from the micrometer scale within the layers of the conductor to the macroscopic behavior of the coil. Here, a hierarchical multiscale approach is used to develop a modular 3-D electro-magneto-thermal coil quench model. The model uses an accurate experimentally validated micrometer-scale REBCO CC model as the basic building block. The CC model is embedded within a homogenized coil framework at one or more locations in the form of multilayer tape modules. This multiscale approach makes possible the studies of quench behavior at the micrometer scale within a tape at any location of interest within a coil without requiring a computationally extensive model of the entire coil. This approach also enables the building of more complicated models by hierarchically integrating smaller modular blocks with the same repeatable modeling techniques. Here, the development of the electro-magneto-thermal coil quench model is first presented, followed by its experimental validation. Simulation results and their implications for coil reliability and quench detection and protection are then discussed.

Comparison of small‐bowel motility of the human jejunum and ileum

Knowledge about human cyclic fasting motility (MMC) and the postprandial response is mostly based on manometric findings in the upper small intestine. Hardly any data exist on human ileal motility, as the acquisition of data has been limited by methodological concerns. The aim was to study human jejunal and ileal motility in an optimized manometric setting. Solid-state 24-h-manometry was performed in the jejunum and ileum of healthy individuals, applying a strict protocol for fasting, resting, and the consumption of a standardized meal. Both visual qualitative and validated computerized quantitative contraction and propagation analysis were performed. MMC occurs in similar frequency in the jejunum and ileum, but it was significantly shorter in the jejunum at night. By many characteristics, ileal motility was less intense and propagative than jejunal: less migrating clustered contractions, and slower propagation velocity and shorter distance in phases II and III, and postprandially - possibly slowing and enhancing nutrient absorption. Prolonged propagated contractions in some individuals were identified as a unique ileal propulsive pattern. Postprandially, an abrupt conversion to a digestive motility pattern occurs simultaneously independent of the region. We found similar basic phenomena of fasting and postprandial motility in the jejunum and ileum of healthy humans. However, different calibration of propagative and contractile activity and special motor events in the ileum may account for a different physiological role in digestion. Future studies of small-bowel motility in healthy and diseased subjects focusing on segmental differences of proximal and distal intestine may be rewarded.

Design of a Quench Protection System for a Coated Conductor Insert Coil

Coated conductors are promising material for the construction of high field magnets, but the slow propagation velocity of the normal zone makes the protection against quenches a critical issue. The quench protection system for a small insert coil under development at CRPP has been studied. The voltage drop and the hot spot temperature during the quench have been estimated using analytical expressions; the cross section of the copper stabilizer, the voltage threshold and the time constant were set as parameters. Detailed calculations have been carried out using the Cryosoft code THEA. The copper cross section available from the tape manufacturer is enough to ensure that the hot spot temperature remains below 200 K, but only in conjunction with a sensitive quench detection system (voltage threshold lower than 100 mV) and a fast dumping time (time constant shorter than 100 ms). These requirements can be fulfilled in the small insert coil under construction, because the inductance is about 50 mH and because the coil can be quickly discharged independently from the main magnet. The passive protection circuit consists of dump resistor and diodes. In case of longer time constants (few seconds), a larger copper cross section (comparable to the one used in low temperature superconducting magnets) is required in order to maintain the temperature within safe values.

Sa1196 Slow Esophageal Propagation Velocity: A Finding in Patients With Dysphagia for Solids

Sa1196 Slow Esophageal Propagation Velocity: A Finding in Patients With Dysphagia for Solids

Towards a virtual C. elegans: A framework for simulation and visualization of the neuromuscular system in a 3D physical environment

The nematode C. elegans is the only animal with a known neuronal wiring diagram, or "connectome". During the last three decades, extensive studies of the C. elegans have provided wide-ranging data about it, but few systematic ways of integrating these data into a dynamic model have been put forward. Here we present a detailed demonstration of a virtual C. elegans aimed at integrating these data in the form of a 3D dynamic model operating in a simulated physical environment. Our current demonstration includes a realistic flexible worm body model, muscular system and a partially implemented ventral neural cord. Our virtual C. elegans demonstrates successful forward and backward locomotion when sending sinusoidal patterns of neuronal activity to groups of motor neurons. To account for the relatively slow propagation velocity and the attenuation of neuronal signals, we introduced "pseudo neurons" into our model to simulate simplified neuronal dynamics. The pseudo neurons also provide a good way of visualizing the nervous system's structure and activity dynamics.

Three-Dimensional Micrometer-Scale Modeling of Quenching in High-Aspect-Ratio $\hbox{YBa}_{2}\hbox{Cu}_{3}\hbox{O}_{7-\delta}$ Coated Conductor Tapes—Part II: Influence of Geometric and Material Properties and Implications for Conductor Engineering and Magnet Design

YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-δ</sub> (YBCO) coated conductors (CCs) show great promise for applications, but due to a very slow normal-zone propagation velocity (NZPV), quench detection and protection in YBCO magnets may be difficult. Present YBCO CCs have been developed with a primary focus on maximizing the critical current density for elevated-temperature low-field or low-temperature high-field applications. As the market for magnet applications progresses, it becomes important to consider design parameters such as the thicknesses and properties of all YBCO CC components, with the intent of considering quench-related behaviors as an integral part of the conductor and magnet design processes. Thus, it is important to know the impacts of conductor parameters on quench behavior. Considering that the YBCO layer itself is on the order of a micrometer in thickness, quench behavior must also be considered at this scale length. Here, the highly accurate experimentally validated micrometer-scale 3-D tape model reported in Part I is used to study how variations in CC geometry and material properties affect quench behavior, including the NZPV, hot-spot temperature, and minimum quench energy. The parametric variations focus on quantities that can be most readily modified by CC manufacturers. Based on simulation results, the relative sensitivities of the quench quantities to the parametric variations are calculated to identify which CC design parameters are most impactful on quench behavior. The implications of these results for quench detection and protection are discussed.

Experimental Test and Numerical Analysis to Estimate Permissible Transport Current Considering Protection of High-Tc Superconducting Tapes in Adiabatic Condition

High-Tc superconducting (HTS) wires have showed good capabilities as an alternative conductor for superconducting magnet. The HTS wires have more current carrying capability within high external magnetic field and its stability against external disturbance is much higher than the low temperature superconducting (LTS) wires. But the HTS wire has slower normal zone propagation (NZP) velocity which makes HTS magnets hard to be protected from unexpected hot spot. This paper presents experimental test and numerical analysis about the relation between transport current and rate of temperature rise in a hot spot. A sample which contained a HTS wire, a heater, and temperature sensor was fabricated and an experimental test on measuring normal zone propagation and temperature of the HTS wire was conducted. A numerical model was also built to estimate transient temperature rise of a winding pack model which was representing practical winding of HTS magnets. The numerical model and its numerical estimation results are expected to be a guideline about designing proper protection technique and operating current for HTS magnets.

Benchmark of Two Quench Codes for the Protection Study of an High Field HTS Insert Dipole

Research on possibilities in long-term LHC (Large Hadron Collider) upgrade include considerations on replacing the Nb-Ti dipoles with Nb3Sn outserts and inserts made of some high temperature superconductor (HTS) which outperforms conventional superconductors above 20 T. Regarding to this target, the WP7.4 (Very high field insert) in project EuCARD is to construct about 1 m long HTS dipole producing 6 T in background field of 13 T. Since the quench analysis of HTS coils is challenging, e.g., due to slow propagation velocities and possibly ambiguous limit between the normal and superconducting state, two different strategies are developed in parallel to analyse the quench of the small prototype insert. The one is based on propagation velocities and the other on solving heat diffusion equation with finite element method. The very first steps of the development include benchmark calculations with the already existing programs for small Nb-Ti solenoid to guarantee similar starting points for the partners. After this, a quench analysis was performed for an HTS solenoid. In this paper we consider the results of these calculations.