YBCO次世代超電導線材のMO磁束観察法による特性評価 超電導工学研究所 町　敬人 MOI : magneto-optical imaging Outline MO（磁気光学）磁束観察の原理と特徴 reel to reel MOI (RTR-MOI)装置の開発 YBCO線材の素線評価 機器応用のためのYBCO線材の評価 本研究は，超電導応用基盤技術研究体の研究として，新エネルギー産業技術総合開発機構の委託により実施したものである。

World map of magneto-optical imaging (MOI-map) ISSP (Russia) SRL (Japan)

MO効果の種類 Various MO effects These effects are close to our life.... Kerr effect Faraday effect Magnetic Kerr effect Cotton-Mouton effect Magnetic circular dichroism Cotton-Mouton effect Faraday effect Faraday rotation angle for diamagnetism samples (ex. glass) These effects are close to our life.... Magneto-optical recording Optical fiber networks V : Verde constant ℓ : thickness of specimen H : magnetic field High voltage electric power lines

Brightness is proportional to the magnetic flux density. MOについて Principle of MOI Faraday effect is used for magneto-optical imaging. Faraday angle two times of θF MO indicator film Magnetic flux Superconductor External field Irreciprocity (←Faraday effect) Brightness is proportional to the magnetic flux density. Detecting the canted component of the in-plane magnetization

[ MO観察の長所 MOI can visualize the distribution of magnetic flux ! Real-time a wide area at a time even if existence of stabilization Ag layer relatively easily Non-destructive two dimensional image General properties of MO imaging (using MO films with in-plane anisotropy) 　 Response time 　 〜 psec 　 Spatial resolution 〜 0.5µm 　 Flux sensitivity　 〜 0.2 Gauss (Bi-YIG film) [ Real time mapping of weak region (=defects) Distribution of current density （J = rot H）

Classification of HTS studies MOについて Fundamental study Application study Origin of HTS Devices applications Searching for new materials Bulk applications Symmetry of Cooper pair Tape and wire applications Co-existence of AF fluctuation Vortex physics High speed response Levitation High speed communication Pinning properties Power applications Low heat conduction Magnet applications etc.... MOI can contribute to both studies !

YBCO(LPE) bicrystals Intragrain JcIG Intergrain JcGB MOについて YBCO(LPE) bicrystals Intragrain JcIG artificial grain boundary ( Conduction via grain ) Intergrain JcGB Brandt et al. JcIG=1.37 x 107 [A/cm2] Machi et al., Advances in Superconductivity Vol.12 (2000).

Various targets of MOI Coated conductors MOI study in SRL MOについて Various targets of MOI Single crystals Thin films Wires and tapes Bulk materials Devices Coated conductors

MO評価が次世代線材研究に果たす役割 線材作製技術 機器要素技術 フィードバック 機器共通基盤要素技術 超電導ケーブル 線材評価 素線評価 機器共通基盤要素技術 機器応用のための評価 超電導ケーブル 線材評価 応力印加前後のMO観察 超電導変圧器 →導体化要素技術 超電導モーター 過電流印加前後のMO観察 →耐過電流要素技術 超電導限流器 スクライビングの評価 →低交流損失化要素技術 接続試料の評価 →接続要素技術

What is the coated conductors ? The shape of coated conductors is suitable to observe MO images. Structure of coated conductors HTS(123) layer Metallic substrate Stabillizing layer (Ag) Aligned metals (Ni, Ni-W, etc) Non-aligned metals (Hastelloy) RABiTS : rolling assisted biaxially textured substrate Buffer layers Buffer layers Metallic substrate Gd2Zr2O7, MgO, Y2O3, CeO2, etc... HTS layers Pulsed laser deposition (PLD) method Metal organic deposition (MOD) method Molecular chemical vapor deposition (MOCVD) method Electron beam (EB) deposition method There are many choise to obtain the coated conductors. The property is not same within each coated conductors.

SRL fabricates two types of coated conductors Experimental Sample for MOI SRL fabricates two types of coated conductors IBAD/PLD : Hastelloy/IBAD(GZO)/PLD(CeO2)/PLD(YBCO) TFA-MOD : Hastelloy/IBAD(GZO) /PLD(CeO2)/TFA-MOD(YBCO) TFA-MOD=metal organic deposition using trifluoroacetates GZO=Gd2Zr2O7, YBCO=YBa2Cu3O7-d MOI experiments MO indicator film Short specimens ~ 50 mm Ordinary flow type MOI equipment Long tape samples (> 5cm) Reel to reel MOI equipment

RTR(reel to reel)-MOI for long tapes Procedure of RTR-MOI (1) MO film removes from tape (2) Displacement of tape (3) Contacting MO film (4) Wait a stable of temperature (5) Applying field (6) MO Observation (7) Repeat to (1) Controller Macro microscope Whole view Reel and cryocooler