Development of Remountable High Temperature Superconducting Magnet
Painter, Jim, Managing Editor has reference to this Academic Journal, PHwiki organized this Journal Development of Remountable High Temperature Superconducting Magnet Prof. Hidetoshi Hashizume Tohoku University 1. Concept of remountable HTS magnet 2. Mechanical joint of HTS tape Mechanical joint of HTS cable must be developed. Development of remountable HTS magnet The but joint method is suitable as long as remountable HTS magnet.
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3. Fundamental study on butt joint of HTS tape 3-1. Experiment of butt joint of HTS tape Current-Resistance Characteristic There exists dependence of joint resistance on current. Joint Resistance: 3.6 (at 60A) Result Experimental Apparatus Voltage Tap BSCCO 2223 Tape Vinyl Chloride Board (IC: 67A, w: 4.0mm, t: 0.26mm) Joint Region Vinyl Chloride Board Contact as long as ce : Thermal contraction 30mm Jointing Resistance is almost inversely proportional to the contact area. 3. Fundamental study on butt joint of HTS tape 3-2. Per as long as mance analysis in different filament location 3-2-1. Composition of HTS tape Superconducting Filament Ag (Stabilizer) Ag Alloy Several tens of superconducting filament Ag (Stabilizer) + Filament Location in Butt Jointing Electromagnetic field analysis is per as long as med to evaluate the influence of filament location BSCCO 2223 Tape 3. Fundamental study on butt joint of HTS tape 3-2. Per as long as mance analysis in different filament location 3-2-2. Analytical model in addition to numerical scheme 2-D FEM Current Vector Potential Method Critical State Model : Bean Model Governing Equation : Faradays Low Current Distribution Joule heating loss J = 44.8% of JC to avoid quenching Gap Region : Assumed Material to Treat Contact Resistance Gap Resistance2.39 10-6 Wm (230mW in butt jointing of one-layer HTS tape)
3. Fundamental study on butt joint of HTS tape 3-2. Per as long as mance analysis in different filament location 3-2-3. Analytical result Model 2 Model 1 SC filament location does not affect the butt jointing per as long as mance Joule heating loss Contact condition is dominant Increase of contact point is effective to reduce joint resistance as long as example with metal-plating. 3. Fundamental study on butt joint of HTS tape 3-3. Dependence of joint resistance on current 3-3-1. Assumption of flat contact surface Electromagnetic Field Analysis Thermal Analysis Model 3 Gap Resistance: 2.8 10-8 Wm (Jointing Resistance at 5A) 3. Fundamental study on butt joint of HTS tape 3-3. Dependence of joint resistance on current 3-3-2. Assumption of notch in addition to /or degradation Decrease of JC High J Expression of decrease of JC Current density becomes larger than critical current density Decrease of current flowing area Decrease of critical current density = Degradation of superconducting filament Notched contact surface
3. Fundamental study on butt joint of HTS tape 3-3. Dependence of joint resistance on current 3-3-3. Analytical result Dependence of jointing resistance on the transport current Protection of joint surface is important as long as example with metal-plating. 4. Study on butt joint of laminated HTS cable 4-1. Test cable in addition to experimental set-up Coolant: Liquid Nitrogen 10-Layered BSCCO 2223 Cable Low Temperature Solder Contact Surface 30, 40, 45, 50, 60 4.2mm 2mm 4. Study on butt joint of laminated HTS cable 4-2. Stress-resistance characteristic Joint resistance becomes almost constant (160 ~ 200MPa) begins to increase slightly (200MPa~ ) There exists optimum stress
4. Study on butt joint of laminated HTS cable 4-3. Current-resistance characteristic Current-resistance characteristic in Dry Joint Thermal Quench IC Current-DR characteristic 4. Study on butt joint of laminated HTS cable 4-4. Angle dependence in addition to plating effect Protective effect with silver-plating Reducing resistance Preventing degradation Angle Dependence Normalized resistance increases when joint surface angle is larger than 45. Slippage occurs because shear stress becomes larger than normal stress. 4. Study on butt joint of laminated HTS cable 4-5. Analytical evaluation with structural analysis 4-5-1. Analytical model (1) 6 loading system are compared Normal stress distribution on joint surface Intensity of stress concentration Buckling with outward as long as ce Structural analysis 3D elastic-plastic de as long as mation analysis Evaluating Bottom loading O
4. Study on butt joint of laminated HTS cable 4-5. Analytical evaluation with structural analysis 4-5-2. Analytical model (2) Analytical object 10-layered laminated HTS cable Length20mm, Width4.2mm, Thickness2.0mm Symmetric restraint condition yz-plane ux=0 zx-plane uy=0 1/4 of real object is calculation area Calculation area Element Bottom plane condition Joint surface Loading by rod Displacement is given to nodal point of cable. Regarding Assumed cross-section replicated at yz-plane as joint surface. Curvature at rod edge curve-like displacement is given. Assuming that the surface is jointed ideally. Slippage between layers is considered on yz-plane. 20-node rectangular element Model B, D Load is given as in case of Upper plane. Except Model B, D z-directional displacement is constrained. t 4. Study on butt joint of laminated HTS cable 4-5. Analytical evaluation with structural analysis 4-5-3. Evaluation of normal stress distribution on joint surface Stress concentration at rod edge affects normal stress distribution on joint surface. Loading from bottom side is effective to obtain uni as long as m stress distribution. Stress distribution in Model B is more uni as long as m than that in Model A The same tendency is obtained in Model C in addition to Model D Stress distribution is concentrated at upper side in Model F 4. Study on butt joint of laminated HTS cable 4-5. Analytical evaluation with structural analysis 4-5-4. Evaluation of intensity of stress concentration Equivalent stress distribution on zx-plane
4. Study on butt joint of laminated HTS cable 4-5. Analytical evaluation with structural analysis 4-5-5. Evaluation of buckling with outward as long as ce z-component of stress on zx-plane HTS cable has layered structure buckling with layer peeling Model A Model B Outward as long as ce occurs locally. Outward as long as ce can peel layer especially in Model B. Cable supporting area in Model B is smaller than that in Model A There exists possibility of buckling in dual loading Cable is unstable Model Ar=0, Top loading Model Br=0, Dual loading 5. Prototype of remountable HTS magnet Layer number Winding number Outer radius Operating temperature Joint number 5 2 85 mm 77 K 4 Specification Solenoid type Photograph of prototype Current-resistance characteristic 6. Summary 1. Fundamental study on butt joint of HTS tape – Joint resistance of 3.6mW was achieved at 60A. 2. Study on butt joint of laminated HTS cable – Joint resistance was reduced small value enough to prevent thermal quench in addition to decrease of critical current at 77K below 500A. – Silver-plating is effective to improve in addition to protect joint surface condition. 3. Fabrication of prototype of remountable HTS magnet – Per as long as mance of prototype of remountable HTS magnet was evaluated in liquid nitrogen environment. – Dependence of joint resistance on current was confirmed. According to numerical analysis, that is caused by degradation of superconducting material near joint surface. Protecting joint surface with metal-plating is important. Feasibility of remountable HTS magnet was demonstrated. – Joint resistance is decided by reduction of contact resistance in addition to degradation of superconducting material with increase of joint stress. – Joint resistance became stable when angle of joint surface was 30 to 45. – How to obtain uni as long as m stress distribution in addition to to avoid stress concentration in addition to buckling are indicated by structural analysis.
7. Future works 8-1. Development of independent heat removal system (a) Porosity: 70% Fiber diameter: 90m (b) Enlarged view Characteristic of metal porous media High thermal conductivity Enlargement of heat transfer area Transport of latent heat with capillary as long as ce Heat removal system with metal porous media 8. Future works 8-2. Design of cooling channel with metal porous media Preventing thermal quench with heat transfer enhancement Introducing cooling technique with metal porous media to remountable HTS magnet Evaluation of rheological characterization in addition to heat transfer characteristic when liquid nitrogen flows thorough metal porous media. Issues Design in addition to fabrication of jointing region with metal porous media
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