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Fujikura Ltd., Chiba, Japan, has developed stable and high-throughput production techniques for REBCO coated conductors (CC) by using large-area ion-beam-assisted-deposition (IBAD), and hot-wall type pulsed-laser-deposition (PLD). Recently, we have been attempting to dope BaMO 3 (BMO, M: Zr or Hf) to REBCO layer in order to enhance in-field critical current density (J c ). In the course of optimizing deposition conditions of PLD for BaHfO 3 doped EuBCO films on IBAD templates, “high J c condition” and “high growth rate condition” were found. For samples prepared under these conditions, the magnetic field angle dependence of I c and REBCO thickness dependence were investigated. Finally, we succeeded in fabricating a 300-m-long CC with uniform I c distribution at the high-growth-rate condition. The longitudinal I c homogeneity (defined as standard deviation divided by average) at 77 K evaluated by magnetization method was 2.6%, which is comparable to nondoped conductors. Transport in-field I c for the both end points were 1756 and 1786 A/cm at 30 K, 2 T, respectively.

Fujikura has developed production techniques of REBa 2 Cu 3 O y (REBCO, RE = rare earth) coated conductors (CCs) and provided high-performance REBCO CCs with long-length and high homogeneity of the critical current. REBCO CCs have a low c-axis strength (delamination strength) which originates from the layered structure. When an epoxy-impregnated REBCO coil is cooled, the radial thermal stress is generated. The stress could cause the delamination of REBCO CCs and lead to degradation of the coil. Therefore, it is important to evaluate the exact delamination strength of the CCs. In this paper, we evaluated the failure probability of the epoxy-impregnated coils at 77 K. We introduced Weibull analysis considering the stress distribution and the sample size effect, and estimated the actual delamination strength of the REBCO CCs. By using the evaluation method, we confirmed the strength enhancement by process improvement.

BaMO 3 (BMO, M: Zr or Hf)-doped REBCO-coated conductors were prepared by Hot-Wall PLD method on IBAD template. The highest J c was obtained for BaHfO 3 -doped EuBCO. Quite strong pinning force density (F p ) of 1.6 TN/m 3 was observed at 4.2 K, 15 T, for a sample deposited with growth rate of ~5 nm/s. It had strong c-axis correlated pinning at the temperature above 20 K with the matching field of ~5 T. A 45-m-long sample was formed by productive high growth rate over 20 nm/s, being consistent with commercial nondoped conductors. It had also large I c of 1687 A/cm and F p of 0.96 7 TN/m 3 was obtained at 4.2 K, 15 T. The end-to-end longitudinal Ic homogeneity (σ) at 77 K in low field was evaluated to be 2.2% by magnetization. Transport in-fields I c were also measured for the both end points at 30 K, 2 T, resulting in 1863 and 1883A/cm, respectively.

We fabricated short samples and a 93 m long coated conductor (C. C.) of EuBa 2 Cu 3 O 7-δ (EuBCO) with BaHfO 3 (BHO) by the IBAD and the PLD methods, which exhibited the high in-field minimum I c value, ( I c (min)), performance of 141.2 (77 K in 3 T) and 411.3 (65 K in 3 T) A/cm-w for a short sample, and 133.9 (77 K in 3 T) A/cm-w for 93 m long C. C. with 3.6 μm in thickness, respectively. Moreover, this long EuBCO with BHO coated conductor also showed high uniform longitudinal I c distributions and n -value in magnetic fields. However, the deposition rate for obtaining the high in-field I c performance was comparatively slow down to 10 μm/h. To realize the low production cost for EuBCO with BHO coated conductors, improvement of the deposition rate of the EuBCO with BHO layer with high I c is required. To solve this problem, we optimized growth conditions including deposition conditions. One of the objectives of this work was changing the layer growth mode from the vapor-solid (VS) mode to the vapor-liquid-solid (VLS) one to fabricate EuBCO with BHO layers for achievement of high production rate and maintaining the high in-field I c and J c performance of the films deposited at slow deposition rates. As a result, we fabricated EuBCO with BHO coated conductors at a high deposition rate of about 40 μm/h and production rate of about 10 m/h, which revealed the I c (min) value of 48.7 A/cm-w at 77 K in 3 T for 1.35 μm in thickness.

We have been developing long REBa 2 Cu 3 O 7-δ (RE: Y, Gd and Eu etc.) with BaMO 3 (M: Zr, Sn and Hf etc.) coated conductors by the combination of the ion-beam assisted deposition (IBAD) and the pulsed laser deposition (PLD) methods. REBa 2 Cu 3 O 7-δ with BaMO 3 coated conductors showed high in-field performance, therefore, these coated conductors could be expected for the industrial and commercial applications at high temperatures in magnetic fields. However, to realize the low production cost for long REBa 2 Cu 3 O 7-δ with BaMO 3 coated conductors, improvement of the production rate of the REBa 2 Cu 3 O 7-δ layers containing BaMO 3 rods with maintaining high superconducting properties is required. To solve these problems, we have tried deposition of the REBa 2 Cu 3 O 7-δ layers with high superconducting properties by the PLD method with high production rate. As a result, we have successfully fabricated EuBa 2 Cu 3 O 7-δ layers containing BaHfO 3 rods with high in-field J c and I c by the PLD method with high production rate. This EuBa 2 Cu 3 O 7-δ with BaHfO 3 coated conductor exhibit a high I c value of 412 and 48.7 A/cm-width at 77 K in self-field and 3 T, respectively at the deposition rate of about 40 μm/h and the production rate of 10 m/h for a 1.35 μm EuBCO layer thick.

The phytohormone abscisic acid (ABA) regulates physiologically important stress and developmental responses in plants. To reveal the mechanism of response to ABA, we isolated several novel ABA-hypersensitive Arabidopsis thaliana mutants, named ahg (ABA-hypersensitive germination). ahg1-1 mutants showed hypersensitivity to ABA, NaCl, KCl, mannitol, glucose and sucrose during germination and post-germination growth, but did not display any significant phenotypes in adult plants. ahg1-1 seeds accumulated slightly more ABA before stratification and showed increased seed dormancy. Map-based cloning of AHG1 revealed that ahg1-1 has a nonsense mutation in a gene encoding a novel protein phosphatase 2C (PP2C). We previously showed that the ahg3-1 mutant has a point mutation in the AtPP2CA gene, which encodes another PP2C that has a major role in the ABA response in seeds (Yoshida et al., 2006b). The levels of AHG1 mRNA were higher in dry seeds and increased during late seed maturation--an expression pattern similar to that of ABI5. Transcriptome analysis revealed that, in ABA-treated germinating seeds, many seed-specific genes and ABA-inducible genes were highly expressed in ahg1-1 and ahg3-1 mutants compared with the wild-type. Detailed analysis suggested differences between the functions of AHG1 and AHG3. Dozens of genes were expressed more strongly in the ahg1-1 mutant than in ahg3-1. Promoter-GUS analyses demonstrated both overlapping and distinct expression patterns in seed. In addition, the ahg1-1 ahg3-1 double mutant was more hypersensitive than either monogenic mutant. These results suggest that AHG1 has specific functions in seed development and germination, shared partly with AHG3.

The phytohormone abscisic acid (ABA) regulates physiologically important developmental processes and stress responses. Previously, we reported on Arabidopsis (Arabidopsis thaliana) L. Heynh. ahg mutants, which are hypersensitive to ABA during germination and early growth. Among them, ABA-hypersensitive germination3 (ahg3) showed the strongest ABA hypersensitivity. In this study, we found that the AHG3 gene is identical to AtPP2CA, which encodes a protein phosphatase 2C (PP2C). Although AtPP2CA has been reported to be involved in the ABA response on the basis of results obtained by reverse-genetics approaches, its physiological relevance in the ABA response has not been clarified yet. We demonstrate in vitro and in vivo that the ahg3-1 missense mutation causes the loss of PP2C activity, providing concrete confirmation that this PP2C functions as a negative regulator in ABA signaling. Furthermore, we compared the effects of disruption mutations of eight structurally related PP2C genes of Arabidopsis, including ABI1, ABI2, HAB1, and HAB2, and found that the disruptant mutant of AHG3/AtPP2CA had the strongest ABA hypersensitivity during germination, but it did not display any significant phenotypes in adult plants. Northern-blot analysis clearly showed that AHG3/AtPP2CA is the most active among those PP2C genes in seeds. These results suggest that AHG3/AtPP2CA plays a major role among PP2Cs in the ABA response in seeds and that the functions of those PP2Cs overlap, but their unique tissue- or development-specific expression confers distinct and indispensable physiological functions in the ABA response.

The phytohormone abscisic acid (ABA) regulates physiologically important stress and developmental responses in plants. To reveal the mechanism of response to ABA, we isolated several novel ABA-hypersensitive Arabidopsis thaliana mutants, named ahg (ABA-hypersensitive germination). ahg1-1 mutants showed hypersensitivity to ABA, NaCl, KCl, mannitol, glucose and sucrose during germination and post-germination growth, but did not display any significant phenotypes in adult plants. ahg1-1 seeds accumulated slightly more ABA before stratification and showed increased seed dormancy. Map-based cloning of AHG1 revealed that ahg1-1 has a nonsense mutation in a gene encoding a novel protein phosphatase 2C (PP2C). We previously showed that the ahg3-1 mutant has a point mutation in the AtPP2CA gene, which encodes another PP2C that has a major role in the ABA response in seeds (Yoshida et al., 2006b). The levels of AHG1 mRNA were higher in dry seeds and increased during late seed maturation--an expression pattern similar to that of ABI5. Transcriptome analysis revealed that, in ABA-treated germinating seeds, many seed-specific genes and ABA-inducible genes were highly expressed in ahg1-1 and ahg3-1 mutants compared with the wild-type. Detailed analysis suggested differences between the functions of AHG1 and AHG3. Dozens of genes were expressed more strongly in the ahg1-1 mutant than in ahg3-1. Promoter-GUS analyses demonstrated both overlapping and distinct expression patterns in seed. In addition, the ahg1-1 ahg3-1 double mutant was more hypersensitive than either monogenic mutant. These results suggest that AHG1 has specific functions in seed development and germination, shared partly with AHG3.

To gain more insight into ABA signaling mechanisms, we conducted genetic screens searching for mutants with altered ABA response in germination and post-germination growth. We isolated seven putative ABA-hypersensitive Arabidopsis mutants and named them ABA-hypersensitive germination (ahg). These mutants exhibited diminished germination or growth ability on medium supplemented with ABA. We further studied four of them: ahg1, ahg2, ahg3 and ahg4. Mapping suggested that they were new ABA-hypersensitive loci. Characterization showed that all of them had enhanced sensitivity to salinity and high osmotic stress in germinating seeds, whereas they each had distinct sugar responses. RT-PCR experiments showed that the expression patterns of the ABA-inducible genes RAB18, AtEm1, AtEm6 and ABI5 in germinating seeds were affected by these four ahg mutations, whereas those of ABI3 and ABI4 were not. ahg4 displayed slightly increased mRNA levels of several ABA-inducible genes upon ABA treatment. By contrast, ahg1 had no clear ABA-hypersensitive phenotypes in adult plants despite its strong phenotype in germination. These results suggest that ahg1, ahg2, ahg3 and ahg4 are novel ABA-hypersensitive mutants representing distinct components in the ABA response.