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This paper describes the established correlations between the characteristics of MgB2-based superconducting materials and their structural features, in particular the oxygen distribution and content. As indicated by SEM and Auger analysis, a sizeable amount of oxygen is usually present in superconducting MgB2 -based materials (bulks, thin films, and wires). The matrix phase of bulk MgB2 contains rather small amounts of oxygen, but contains a high amount of dispersed inclusions or areas with compositions close to MgBO. X-ray phase analysis with Rietveld refinement (using the FullProf Suite program package) of several highly dense MgB2 -based bulk samples (with high critical current densities) showed that the superconducting phase had a composition within the range MgB1.68O0.26 and MgB1.74O0.32 instead of pure MgB2 . Besides, a small amount of a phase with MgO structure was observed in the materials by X-rays as well. The calculation of the enthalpy of formation confirms the possibility of oxygen solubility in MgB2 and shows that the formation of MgB1.75B0.25 is most favorable. The results of ab initio calculations of the electronic structure and stability of the MgB2 compounds with partial oxygen substitution for boron show that it is energetically preferable for oxygen atoms to replace boron pairwise.

A powder sample and single-crystal plates of the topological insulator Bi2Te3 have been investigated using the 125Te NMR method at room temperature and at low temperatures in the range from 12.5 to 16.5 K. The NMR spectra of the single-crystal plates have been studied in the orientation where the crystallographic axis c is directed parallel or perpendicular to the magnetic field. The spectra have been obtained by means of recording spin-echo signals and plotting their envelopes. It has been shown that the NMR spectra for the bismuth telluride powder and plates with the orientation c ⊥ B consist of two lines, which are presumably attributed to tellurium nuclei in two crystallographic positions in the bulk of the sample. The position and shape of the lines are determined by the chemical shift and the Knight shift. For the orientation of the plates c || B, the spectrum contains an additional component in the high-frequency region, which cannot appear due to the angular dependence of the line shifts caused by tellurium nuclei in the bulk of the topological insulator. At a low temperature, the additional line dominates in the spectrum.

More than 100 tons of Nb-Ti superconducting strands were produced by JSC “ChMP” (RF) for the ITER poloidal field coils (PF1&6) in the period from 2010 to 2014. The strands were manufactured based on the NT-47 alloy with a titanium content within 46.0-48.5 wt%, using the technology developed at Bochvar Institute. Measurements of the temperature and field dependence of the critical currents were carried out at the Low Temperature Physics Department of Atominstitut, Technische Universitat Wien, on strands stemming from the 30%, 60%, and 90% stages of industrial production. The facility for variable temperature critical current measurements was upgraded in order to provide direct measurements of the critical current up to 300 A at relatively high temperatures (T > 5 K) in a gas-cooled mode and up to 900 A in liquid helium. Unique results regarding the field and temperature dependence of the critical current in the range from 2 to 12 T and from 3.5 to 7 K, respectively, are presented and discussed based on singleand two-component pinning models. On the basis of mathematical models, the critical temperature at which the transition to the resistive state occurs (T cs ) was evaluated for the operating conditions (6.4 T and 33 A) of the poloidal field coils. Statistical analysis revealed that both models adequately describe the experimental Ic(T, B) data; however, a comparison of the models based on the Fisher test shows a statistical difference.

Fault current limiters (FCL) require superconducting (SC) materials which can provide a definite rate of response to a fault event resulting in the SC – normal state reversible transition. The main characteristics determined the material suitability are the critical current density, jc, thermal conductivity and capacity which are strongly determined by manufacturing technology, in particular, of MgB2. In the paper we estimate the jc of bulk MgB2 samples by the vibrating magnetometer and inductive, contactless transformer, method using ring samples. The bulk MgB2 samples were produced under 30 MPa (hot pressing) and 2 GPa (quasihydrostatic pressing) at 800-1050 оС from different initial ingredients (Mg and B or MgB2 with and without additions). It is shown that the technology process and initial ingredients strongly influence the distribution of boron-and oxygen-enriched nanosized inhomogenities in MgB2 matrix, connectivity between SC grains, material porosity and, as result, the SC properties. The transformer method gives the jc in the range from 1.6·104 up to 6.3·104 A/cm2 at about 4 K while using magnetometer measurements the jc is estimated from 2.24·105 up to 5.1·105 A/cm2 at 10 K in self-magnetic fields. The contradictions in the jc estimated by different methods can be explained by instability of the SC state of MgB2, caused by variation of the applied magnetic field. Using the transformer method AC losses per a cycle before quenching for the best materials were estimated around 0.75-1 J/cm3, while the power of losses was about 200 W. The FCL model with rings cut out from SC MgB2 materials prepared using various technologies demonstrated that MgB2 is a promising material for application in inductive FCLs.

The polycrystalline solid solutions Cd1 – xFexO (0 ⩽ x ⩽ 0.07) possessing ferromagnetic properties at 5 K and room temperature have been synthesized by a precursor method using the formate Cd1 – xFex(HCOO)2 ·2H2O.

Insulation systems for fusion magnets have to operate under intense radiation, mainly fast neutrons and γ-radiation. At the ITER design fluence of 1x10 22 m -2 (E>0.1 MeV), conventional epoxy resins, which were used, e.g., for the ITER TF model coil, start to disintegrate. As a consequence, research programs were launched under EFDA, F4E and ITER contracts in order to find radiation harder resins as well as to investigate the properties of cyanate esters (CE) and CE/epoxy blends. The CE content was varied in the range between 100 % and 20 %. Test materials, consisting of wrapped R-glass fiber / polyimide tapes and VPI impregnated with various resins, were produced by European industry and tested at 77 K. Tensile and short beam shear tests were carried out to characterize the mechanical properties prior to and after irradiation to fast neutron fluences of up to 5x10 22 m -2 (E>0.1 MeV) in the TRIGA reactor (Vienna). In addition, tension-tension fatigue measurements were performed in the load-controlled mode to simulate the pulsed operation conditions of ITER. It turned out that these CE based insulation systems offer excellent properties at the ITER design fluence including an adequate safety margin, especially when a mixing ratio of 40% CE and 60 % epoxy resin is employed. Slight modifications of the resin, mainly regarding an extension of the pot-life to more than 100 hours, were made in view of the dimensions and the complexity of the ITER TF coils. The corresponding results confirm their excellent performance and will be reported. Radiation resistant materials have also been developed by US and Japanese Industry. The qualification of these insulation systems is currently under way and comprises 40:60 CE / epoxy blends from different suppliers (Huntsman, CTD). Test materials were fabricated under the same conditions in order to provide a comparable data base. The results will be presented and discussed.

Polycrystalline Zn1–xFexO (0 ≤ x ≤ 0.075) solid solutions with the wurtzite structure belonging to the class of diluted magnetic semiconductors were synthesized by the precursor method using mixed Zn1–xFex(HCOO)2·2H2O formate as a precursor. As an example we show for samples with x = 0.025 and 0.05 that the room-temperature magnetic moment of Zn1–xFexO solid solutions increases regularly with the iron concentration.

Magnetic, magnetocaloric and transport properties of alloys of system Ni-Mn-In has been investigated. Large magnetocaloric effect have been observed at temperatures below room, making it a potential material system for various applications.

MgB 2 -based bulk materials synthesized under 30 MPa-2 GPa pressure demonstrated an enhanced connectivity A F ~50%-98%,as compared tomostother reports (below50%), and a shielding fraction of 75%-100%. The materials inhibit high critical current densities j c , but no strict correlation was found between A F and j c . On the other side, we found correlations between jc and the distribution of nanostructural inhomogeneities such as impurity oxygen in the form of oxygen-enriched Mg-B-O nanolayers or nanoinclusions and its solution in the MgB 2 matrix and as well with the amount and size of higher magnesium borides MgB x , x ≥ 4 inclusions. The distribution of boron- and oxygen-enriched (as compared to stoichiometric MgB 2 ) inhomogeneities affects the type of pinning and, thus, jc, and to some extent, it can be regulated by synthesis temperatures and pressures and by Ti addition. Auger spectroscopy, scanning electron microscopy, and X-ray with Rietveld refinement were used for structural study.

HannaH revealed consistent overall safety profiles between fixed-dose subcutaneous (s.c.) and weight-based intravenous (i.v.) trastuzumab (median follow-up 20 months). Event-free survival rates were balanced between i.v. and s.c. There was no association between toxicity and exposure or body weight. Similar pathologic complete response rates were observed in higher weight patients in i.v. and s.c. Background HannaH (NCT00950300) was a phase III, randomized, international, open-label study that compared pharmacokinetics (PK), efficacy, and safety of two different trastuzumab formulations [subcutaneous (s.c.) and intravenous (i.v.)] in HER2-positive, operable, locally advanced, or inflammatory breast cancer in the neoadjuvant/adjuvant setting. The co-primary end points, to show noninferiority of s.c. versus i.v. trastuzumab in terms of serum concentration (Ctrough) and pathologic complete response (pCR) were met; safety profiles were comparable at 12 months' median follow-up. Secondary end points included safety and tolerability, PK profile, immunogenicity, and event-free survival (EFS). We now report updated safety and efficacy data after a median follow-up of 20 months. Patients and methods Patients (N = 596) were treated with eight cycles of neoadjuvant chemotherapy, administered concurrently with 3-weekly s.c. trastuzumab (fixed dose of 600 mg) or the standard weight-based i.v. method. Following surgery, patients continued trastuzumab treatment to complete 1 year of therapy. Updated analyses of PK, efficacy, safety, and immunogenicity data were carried out. Results s.c. trastuzumab was generally well tolerated and the incidence of adverse events (AEs), including grade 3 or 4 AEs, between treatment groups was comparable. A slightly higher incidence of serious AEs (SAEs), mainly due to infections, was reported with s.c. treatment {64 [21.5%; 95% confidence interval (CI) 17.0%–26.7%] versus 42 (14.1%; 95% CI 10.4%–18.6%) in the i.v. group}; however, the differences were small and often based on rare events, with no observable pattern across reported events. An early analysis of EFS showed rates of 95% in both groups 1 year postrandomization. Exploratory analyses did not reveal an association between toxicity and body weight or exposure. Conclusions Overall, the safety profile of s.c. trastuzumab was consistent with the previously published data from HannaH and the known safety profile of i.v. trastuzumab. EFS rates were comparable between the i.v. and s.c. groups. Clinical trial number NCT00950300.

The high pressure (50 MPa - 2 GPa) – high temperature synthesized MgB2 bulk materials are characterized by nearly theoretical density (1-2% porosity), 80-98% connectivity, extremely high critical current densities (e.g. at 20 K, in 0–1 T jc=1.3–1.0 MA·cm-2 (with 10% SiC) and jc= 0.92 – 0.73 MA·cm-2 (without doping)), large irreversibility fields (Birr(18.4 K) =15 T and Birr (0 K) = 32.5 T) and high upper critical fields (Bc2 (22 K) =15 T and Bc2(0 K) ~ 42.1 T). The transformation of grain boundary pinning to point pinning in MgB2-based materials with increasing manufacturing temperature (from 800 to 1050 oC) under pressures from 0.1 to 2 GPa correlates well with an increase in critical current density in low external magnetic fields caused by the redistribution of boron and the oxygen impurities in the material structure. As the manufacturing temperature increases, the discontinuous oxygen enriched layers transform into distinct Mg-B-O inclusions and the size and amount of inclusions of higher magnesium borides MgBX (X>4) are reduced. The effect of oxygen and boron redistribution can be enhanced by Ti or SiC additions.

Background.The Trastuzumab for Gastric Cancer phase III trial demonstrated that combining trastuzumab with chemotherapy significantly improved overall survival compared with chemotherapy alone in HER2-positive advanced gastric or gastroesophageal junction cancer. We report health-related quality of life (HRQoL) and quality-adjusted timewithoutsymptomsofdiseaseortoxicity(Q-TWiST)results from this trial. Patients and Methods. Patients were randomized to receive sixcycles ofchemotherapy given every 3 weeks (capecitabine or fluorouracil, plus cisplatin) either alone or combined with administration of trastuzumab every 3 weeks until disease progression. At each clinical visit, HRQoL was assessed using two European Organization for Research and Treatment of Cancer quality of life questionnaires, QLQ-C30 and QLQSTO22. Q-TWiST methodology was applied retrospectively using the clinical data and utility coefficients. Results.Trastuzumab plus chemotherapy prolonged time to 10% definitive deterioration in all QLQ-C30 and QLQ-STO22 scores, including QLQ-C30 global health status versus chemotherapy alone, from 6.4 months to 10.2 months. In addition, trastuzumab plus chemotherapy extended Q-TWiST by 2.42 months compared with chemotherapy alone. Conclusion. Compared with chemotherapy alone, trastuzumab plus chemotherapy prolongs time to deterioration of HRQoLandincreasesquality-adjustedsurvivalinpatientswith HER2-positive gastric or gastroesophageal junction cancer. The Oncologist 2014;19:1–8 Implications for Practice: In the randomized phase III ToGA (Trastuzumab for Gastric Cancer) trial, adding trastuzumab to chemotherapy increased overall survival in patients with first-line HER2-positive advanced gastric cancer without increasing the overall incidence of adverse events.The results from the trial led to the approval of trastuzumab for this indication. Advanced gastriccancerisincurable,andmostpatientsaresymptomatic.Consequently,itisimportantthatnewtreatmentsimprovesurvival withoutcompromisinghealth-relatedqualityoflife(HRQoL).Weshowthataddingtrastuzumabtochemotherapyprolongedthe

Commercial multifilamentary Nb-Ti strands produced by the Russian Federation DA for the ITER poloidal field coils PF1 and PF6 were characterized regarding the critical current versus magnetic field dependence from 2 to 10 T over a wide range of temperatures from 2.5 to 7 K. The data were collected on several Nb-Ti strands at the stage before production and after 30% of the production for the ITER program. Jc(B, T) fits were determined using parameterization models with single pinning and two-pinning components. The validity and limitation of these estimations will be discussed. The pinning force curves are presented in the temperature range from 2.5 to 4.2 K and indicate a shift of the pinning force peak to lower fields with increasing temperature. The current sharing temperature Tcs at the operating current (33 A) and field (6.4 T) was determined from both parameterization models. The results of Tcs show good reproducibility for each set of Nb-Ti strands. The good agreement between experimental and fit results over very wide temperature ranges can be used for the analysis of experimental data on the PF conductor performance and for the design of future superconducting magnets.

Intensive research over the past decades demonstrated that the mechanical material performance of epoxy based glass fiber reinforced plastics, which are normally used by industry as insulating materials in magnet technology, degrades dramatically upon irradiation to fast neutron fluences above 1 × 1022 m−2 (E > 0.1 MeV). which have to be expected in large fusion devices like ITER. This triggered an insulation development program based on cyanate ester (CE) and blends of CE and epoxies, which are not affected up to twice this fluence level, and therefore appropriate for large fusion magnets like the ITER TF coils. Together with several suppliers resin mixtures with very low viscosity over many hours were developed, which renders them suitable for the impregnation of very large volumes. This paper reports on a qualification program carried out during the past few years to characterize suitable materials, i.e. various boron-free R-glass fiber reinforcements interleaved with polyimide foils embedded in CE/epoxy blends containing 40% of CE, a repair resin, a conductor insulation, and various polyimide/glass fiber bonded tapes. The mechanical properties were assessed at 77 K in tension and in the interlaminar shear mode under static and dynamic load conditions prior to and after reactor irradiation at ~340 K to neutron fluences of up to 2 × 1022 m−2 (E > 0.1 MeV). i.e. twice the ITER design fluence. The results confirmed that a sustainable solution has become available for this critical magnet component of ITER.

International audience; Increasing the pressure during manufacturing MgB2 enhances the volume pinning force and moves the position of the maximum to higher magnetic fields. A similar shift was observed when Ti or SiC was added and the maximum of the volume pinning force was found at higher fields in in situ synthesized materials than in ex situ sintered samples. We attribute the observed changes to Mg–B–O oxygen-enriched regions and grains of higher magnesium borides in the MgB2 matrix. High-temperature processed materials demonstrated mainly point or mixed pinning while grain boundary pinning dominated after low-temperature synthesis.

Superconducting (SC) and mechanical properties of spark plasma (or SPS) produced MgB2 –based materials allow their efficient applications in fault current limiters, superconducting electromotors, pumps, generators, magnetic bearings, etc. The synthesized from Mg and B at 50 MPa, 1050 °C for 30 min material has a density of 2.52 g/cm3, critical current density, jc = 7.1•105 A/cm2 at 10 K , 5.4 •105 A/cm2 at 20 K, and 9•104 A/cm2 at 35 K in zero magnetic field; at 20 K its field of irreversibility Birr(20)=7 T and upper critical field Bc2(20)=11 T; microhardness HV=10.5 GPa and fracture toughness K1C =1.7 MPa•m1/2 at 4.9 N-load. SPS-manufactured in- situ MgB2-based materials usually have somewhat higher jc than sintered ex-situ. The pressure variations from 16 to 96 MPa during the SPS-process did not affect material SC characteristics significantly; the jc at 10-20 K was slightly higher and the material density was higher by 11%, when pressures of 50-96 MPa were used. The structure of SPS-produced MgB2 material contains Mg-B-O inclusions and inclusions of higher borides (of compositions near MgB4, MgB7, MgB12, MgB17, MgB20), which can be pinning centers. The presence of higher borides in the MgB2 structure can be revealed by the SEM and Raman spectroscopy.

Structures of MgB2-based materials manufactured under pressure (up to 2 GPa) by different methods having high superconducting performance and connectivity are multiphase and contain different Mg-B-O compounds. Some oxygen can be incorporated into MgB2 and boron into MgO structures, MgBx (X=4-20) inclusions contain practically no oxygen. Regulating manufacturing temperature, pressure, introducing additions one can influence oxygen and boron distribution in the materials and thus, affect the formation, amount and sizes of Mg-B-O and MgBx inclusions and changing type of pinning, pinning force and so affect critical current density j c. The boron concentration increase in initial Mg and B mixture allows obtaining sample containing 88.5 wt% of MgB12 with TC of 37.4 K (estimated magnetically).

Fiber reinforced composites impregnated with mixtures of cyanate ester and epoxy resin demonstrated their excellent performance at the ITER design fluence and beyond. Slight modifications of the resin were necessary to extend the pot-life to more than 100 h due to the complexity of the coil structure. Two CE blends were supplied by Huntsman, Switzerland, and CTD, USA, according to the ITER TF coil specification, in order to be qualified for ITER. Sets of test samples were produced under exactly the same conditions. The insulation systems consist of a wrapped R-glass/polyimide reinforcement, vacuum impregnated with the cyanate ester/epoxy blends. The mechanical properties were characterized prior to and after irradiation to a fast neutron fluence of 2 × 1022 m−2 (E > 0.1 MeV), i.e. twice the ITER design fluence, in tension and interlaminar shear at 77 K. In addition, tension–tension fatigue measurements were carried out in order to simulate the pulsed operation of ITER. The results show that the mechanical properties of both materials are hardly affected by neutron irradiation.

In view of the significant progress in coated conductor processing technologies, a wide variety of applications have become feasible. One of them is the design of superconducting magnets for fusion devices operating in the liquid nitrogen temperature range. In this case, the material has to withstand a significant fluence of fast neutrons. Samples of the latest generation of coated conductors provided by commercial suppliers were sequentially irradiated in a fission reactor and characterized by magnetic and direct transport measurements. Angular resolved transport measurements were performed and interesting changes in Jc(φ) were observed. In addition, the effects of thermal neutron irradiation on coated conductors are presented. The most important outcome for applications, the dependence of Jc on the neutron fluence, is discussed in the last part.

Nuclear fusion devices based on the magnetic confinement principle heavily rely on the existence and performance of superconducting magnets and have always significantly contributed to advancing superconductor and magnet technology to their limits. In view of the presently ongoing construction of the tokamak device ITER and the stellerator device Wendelstein 7X and their record breaking parameters concerning size, complexity of design, stored energy, amperage, mechanical and magnetic forces, critical current densities and stability requirements, it is deemed timely to review another critical parameter that is practically unique to these devices, namely the radiation response of all magnet components to the lifetime fluence of fast neutrons and gamma rays produced by the fusion reactions of deuterium and tritium. I will review these radiation effects in turn for the currently employed standard "technical" low temperature superconductors NbTi and Nb3Sn , the stabilizing material ( Cu ) as well as the magnet insulation materials and conclude by discussing the potential of high temperature superconducting materials for future generations of fusion devices, such as DEMO.

We studied the electrical and optical properties of X2YZ (X = Co, Fe; Y = Cr, Mn, Ti; Z = Ga, Al, Si) Heusler alloys. We showed that the electrical and optical properties of Co2TiAl and Fe2TiAl are typical of metals. An abnormal behavior of the resistivity and the optical properties in the IR range of the other alloys was observed, i.e., the resistivity exhibits a semiconductor-like behavior and the optical conductivity has no contribution from the intraband absorption of the conduction electrons. The experimental data analysis, based on existing band calculations, allowed us to conclude that the anomalous behavior of their properties is determined by electronic states near to and at the Fermi level. The electronic states in the subband with spin up give the main contribution to the interband transitions in the IR range, but they practically do not contribute to the static conductivity (resistivity). There are almost no charge carries in the other electronic subband (with spin down), and hence, the interband transitions occur only at the energies above the semiconductor gap values.

Angular dependent measurements of Jc were performed on a commercial coated conductor (SuperPower) consisting of a 1 μm thick YBCO layer grown on a MgO IBAD buffer layer. An asymmetric behavior of the angular dependence of Jc (Jc(Ф)) was found with a changing distance between the two peaks at different temperatures and applied magnetic fields. One peak always occurs when the field is oriented parallel to the tape surface, the other smaller peak is located in the perpendicular orientation at high fields, but slightly shifted (by up to 10°) at 77 K and low magnetic fields. This peak shift, the overall Jc(Ф) asymmetry and the influence of fast neutron irradiation on Jc(Ф) are discussed. The spherical defects, introduced by collisions of fast neutrons with the lattice atoms, are randomly distributed, add to the as-grown defect structure and change the critical current anisotropy by altering both peaks.

Insulation systems for fusion magnets have to operate in a harsh environment, especially also under intense radiation. Over the past years, cyanate ester (CE) resins have been playing an increasingly important role because of their enhanced temperature and radiation resistance compared to conventional epoxy resins. Blending CE with epoxy resins offers the possibility to manufacture radiation resistant insulations at a low price compared to pure CE materials. Therefore, it is of special interest to study the influence of the CE content and of the epoxy resin on the mechanical properties to find materials, which are suitable and economically reasonable for the specific demands of such magnets. In this study R-glass fiber/Kapton reinforced cyanate ester/epoxy blends with different CE content were investigated. Each material was exposed to conditions matching those expected for the ITER TF coil insulation as closely as possible. In order to characterize the mechanical properties, short-beam shear and static tensile tests were carried out at 77 K prior to and after irradiation to fast neutron fluences of up to 5 × 1022 m−2 (E > 0.1 MeV), in the TRIGA reactor (Vienna) at ambient temperature (340 K). In addition, tension–tension fatigue measurements were performed in the load-controlled mode to simulate the pulsed operation conditions of ITER.

Ni-Mn-Ga based compounds are of great interest due to their magneto- and temperature operated shape memory. To obtain new results on their electronic structure, we studied the low-temperature kinetic properties and the structure of Ni-Mn-Ga alloys at temperatures T≪TM, TC (TM is the temperature of the martensitic transition and TC the temperature of the magnetic (Curie) transition, which are both close to room temperature). Ordered (cast) and disordered samples, having a nanocrystalline substructure, were investigated. The galvanomagnetic and electrical properties were measured in the temperature interval from 2 to 80 K and in magnetic fields of up to 15 T. We find that the electrical and the high-field properties of these alloys strongly change due to the transition into the nanocrystalline state.

Critical current density (jc) of high-pressure (2 GPa) manufactured MgB2-based superconductors depends on the amount and distribution of higher borides (MgB12) in MgB2 matrix, which in turn are determined by the nature of the initial components first of all B or MgB2 and the temperature of sintering or synthesis. Ti and Ta additions can improve jc by promoting the higher boride formation via impurity hydrogen absorption, thus preventing MgH2 detrimental for jc being formed, which possibly increases the MgB12 nucleation barrier. SiC (0.2-0.8 mum) addition increases jc of MgB2, allowing us to get jc = 106 A/cm2 at 20 K in the 1 T field: pinning is increased by SiC and higher boride grains and there is no notable interaction between SiC and MgB2 . As the synthesis temperature increases from 800 to 1050degC, Ti and SiC additions may affect the oxygen segregation and formation of Mg-B-O inclusions enriched with oxygen as compared to the amount of oxygen in the MgB2 matrix, which can also promote an increase in pinning. Materials high-pressure synthesized from Mg and B taken in 1:4, 1:6, 1:7, 1:8, 1:10, 1:12, 1:20 ratios were superconductive with Tc of about 37 K. High jc (7middot104 - 2middot104 A/cm2 in zero field at 10-30 K, respectively) showed materials with the matrix composition near MgB12 stoichiometry, they have doubled microhardness of MgB2.

Fiber reinforced composites impregnated with mixtures of various cyanate ester and epoxy resins demonstrated their excellent performance at the ITER design fluence and beyond. The insulation systems consist of a wrapped R-glass/Kapton reinforcement, vacuum impregnated with a cyanate ester/epoxy blend. For the fabrication of the insulation a long pot-life of the resin is of great importance, which is mainly determined by the amount and the composition of the catalyst needed for curing the resin. However, the catalyst, which amounts to 1–2% of the resin, may also affect the mechanical properties as well as the radiation hardness of the material. In order to investigate these effects, two different composites were fabricated using a Mn- and a Co-catalyst, respectively. The mechanical properties are characterized prior to and after irradiation to a fast neutron fluence of 1 × 1022 m−2 (E > 0.1 MeV) in tension and interlaminar shear at 77 K.

The achievable transport critical current densities in coated conductors are limited in part by low angle grain boundaries. Effects like vortex channeling found in these low angle boundaries at low fields can also be studied in vicinal thin films. The influence of neutron irradiation, a proven method for increasing magnetic and current carrying properties, on these effects was investigated in this work. An YBCO vicinal sample, grown on a SrTiO3 substrate with the ab plane oriented at 6 degrees off parallel, was fabricated through pulsed layer deposition (PLD) and both transition temperature and transport current measurements were performed using a 2-axis probe. The sample was rotated at varying temperature in an applied magnetic field of up to 6 T. The angular dependence of the critical density was determined before and after an irradiation to a neutron fluence of 1 times 1021 m-2 in the TRIGA Mark II reactor in Vienna.

Advanced epoxy-based glass fiber reinforced plastics are commercially used as insulating materials in fusion magnet technology. However, their mechanical strength drops dramatically upon irradiation to a fast neutron fluence of 1 × 1022 m−2 (E > 0.1 MeV), i.e. the ITER design fluence. The recent results demonstrated that cyanate ester (CE)/epoxy blends were not affected at this fluence level. In this work, various magnet insulation systems containing boron-free R-glass fiber reinforcements embedded in CE/epoxy blends are investigated. The mechanical properties were assessed at 77 K in tension as well as in the interlaminar shear mode prior to and after reactor irradiation at ambient temperature (∼340 K) to neutron fluences of up to 4 × 1022 m−2 (E > 0.1 MeV) under static and dynamic load conditions. The results show only a small reduction of the mechanical properties at twice the ITER design fluence. At the highest irradiation level the interlaminar shear strength of blends with at least 40% CE is only reduced by 20–30%.

Coated conductors (CCs) are considered as an alternative to low temperature superconductors in fusion magnets. High magnetic fields are needed to confine the plasma, which can be generated by YBCO coated conductors at relatively high temperatures (50-77 K). The critical current densities of CCs improved continuously during the last few years and the production was scaled up. The conductors will be exposed to neutron radiation in a fusion magnet, which could potentially improve or degrade their properties. Industrial YBCO coated conductors were characterized by magnetization and direct transport measurements in magnetic fields of up to 15 Tesla and at temperatures between 50 and 85 K. The critical current, its anisotropy and the irreversibility line were determined. The measurements were performed on different samples, which were sequentially irradiated up to a fluence of 2 times 1022 m-2 (two times the ITER specification). The measurements were repeated after each irradiation step to investigate the change in the superconducting parameters. Depending on the production process of the CC and on the actual operation conditions, an increase or a decrease of the critical current density is observed. The measurements show that the performance of the CC nearly reaches the required specification for ITER conductors at present. Neutron irradiation generally does not degrade their properties in the operating range of fusion magnets.

High temperature superconductors (HTS) might be applied for the magnets in a next step fusion device. The magnets could operate in the temperature range of liquid nitrogen or slightly below. Apart from the special requirements on the mechanical properties, the conductors will be exposed to radiation. We examine the influence of neutron irradiation on coated conductors. These conductors were irradiated sequentially to the ITER specification of 10 22 m −2 . The samples were examined by magnetisation measurements and by direct transport measurements with regard to changes in their superconducting parameters. The critical current, its anisotropy and the irreversibility line were determined under different conditions. The magnetisation measurements were carried out in a vector vibrating-sample magnetometer (VSM) in a wide temperature range with a maximum field of 5 T. The transport measurements were carried out in fields up to 15 T. An increase of the critical current for fields parallel to the c -axis is observed in the high field region. A crossover of the critical current between the unirradiated and the irradiated state is found at lower fields. Also a peak in I C (shoulder effects) can be observed in anisotropy measurements at small angles (close to the ab -plane) in highly irradiated samples.

To ensure secure operation of the magnet coils, the insulation system must keep its mechanical strength over the whole plant lifetime in a gamma and fast neutron radiation environment. Recent results on cyanate ester (CE)/epoxy blends demonstrated their mechanical integrity after irradiation to the ITER design fluence of 1 × 1022 m−2 (E > 0.1 MeV). For economic reasons, the cyanate ester content should be kept as low as possible due to the higher price compared to traditional epoxy resins. Therefore, the optimal composition of cyanate ester and epoxy is of great importance. In this study R-glass fiber/Kapton reinforced cyanate ester/epoxy blends with different epoxy resins and epoxy content were investigated. Short-beam shear and static tensile tests were carried out at 77 K prior to and after irradiation to a fast neutron fluence of 1 × 1022 and 2 × 1022 m−2 (E > 0.1 MeV), which was done in the TRIGA reactor (Vienna) at ambient temperature (340 K). In addition, tension–tension fatigue measurements were performed in the load- and strain- controlled mode to simulate the pulsed operation conditions of ITER.

The application of glass-fiber reinforced plastics as insulation materials for fusion magnet coils (e.g. of ITER) requires a full mechanical material characterization under ITER relevant conditions. The tension–tension fatigue test is useful to simulate the pulsed tokamak operation of the ITER coils in the relevant range of 104–105 cycles. The fatigue process can be run under load or strain control, which may influence the material behavior under cyclic load conditions. Therefore, investigations were performed at 77 K using an industrial glass-fiber reinforced composite impregnated with epoxy resin. For both the load and the strain controlled mode, R-values of 0.3 and 0.5 and a frequency of 10 Hz were chosen. The results are discussed with respect to the lifetime performance of ITER.

The magnetoscan technique was recently introduced to investigate local inhomogeneities of large high T c superconductors without destroying them. Local currents are induced by a small permanent magnet moving slightly above the sample surface. The magnetic field of these currents, which depend on the local material properties, is measured by a Hall probe. We show that the technique can be successfully applied to coated conductors. Inhomogeneities and defects are easily detected by significant changes in the magnetoscan signal. To confirm our interpretation of the experiment, numerical simulations, based on Maxwell’s equations, were carried out. We calculate the current flow and the magnetoscan signal for different experimental setups and critical current densities. Inhomogeneities were introduced by assuming a position dependent critical current density. Good agreement between experiment and theory is obtained.

The temperature dependences of the resistivity, Hall coefficient, and magnetic susceptibility of iron-vanadium-aluminum alloys have been investigated. It has been established that the alloy Fe1.9V1.1Al exhibits semiconductor behavior for the method used to obtain uniform alloys. It is shown that at temperatures below 30K the semiconductor alloy possesses the characteristic low-temperature scale of the dependences observed, which could be responsible for the appearance of a narrow pseudogap in the electron density of states. A simple theoretical description of the effects of a pseudogap is proposed. A consistent fit of the theoretical to the experimental relations made it possible to determine the effective width of the pseudogap (∼1MeV) and its relative depth (∼102).

Hybrid liquid phase epitaxy (HLPE) is among the most promising high rate techniques for fabricating coated conductors. In this paper we report on the irreversible magnetic properties of HLPE thick films grown on single crystalline SrTiO3 at temperatures of 860degC and 890degC. Magnetic measurements in the temperature range from 5 to 90 K were carried out on these samples to determine the critical current density. Furthermore, neutron irradiation which introduces effective pinning centers of known density provides us with additional information on the field dependence of pinning in HLPE coated conductors.

Monofilamentary SiC doped wires and multifilamentary wires made from magnesium-rich powders were exposed to thermal neutrons. The induced defects enhance the field, up to which the resistivity is zero ("irreversibility field") at 4.2 K (by about 1-2 T), and, therefore, reduce the field dependence of the critical current density. On the other hand, the transition temperature decreases from about 35 K to 32.5 K, thus restricting the beneficial effect of neutron irradiation to low temperatures. Changes of the critical current density are discussed in terms of changes of the fundamental superconducting parameters (condensation energy, upper critical field, anisotropy) and changes of the flux pinning properties.

We report on Hall scan and magnetoscan measurements on coated conductors. The magnetoscan technique was optimized for scanning tapes of high temperature superconductors, in order to analyze their homogeneity and current carrying capability. The principle of the magnetoscan technique consists of magnetizing the sample locally by moving a magnet over the sample surface and measuring the magnetic field of the induced supercurrents with a Hall probe. The position of the Hall probe, the permanent magnet as well as the gap between permanent magnet and sample can be changed in our setup. The measurements were done on different conductors with different architecture. The map of the magnetic field above the surface of the sample reflects dasiastrongpsila and dasiaweakpsila superconducting areas in the tape allowing to analyze the defect structure and the critical currents. The results show good agreement with conventional measurements.

We report non-Cu critical current densities of 4.09 * 10^9 A/m^2 at 12 T and 2.27 * 10^9 A/m^2 at 15 T obtained from transport measurements on a Ti-alloyed RRP Nb3Sn wire after irradiation to a fast neutron fluence of 8.9 * 10^21 m^-2. These values are to our knowledge unprecedented in multifilamentary Nb3Sn, and they correspond to a Jc enhancement of approximately 60% relative to the unirradiated state. Our magnetometry data obtained on short wire samples irradiated to fast neutron fluences of up to 2.5 * 10^22 m^-2 indicate the possibility of an even better performance, whereas earlier irradiation studies on bronze-processed Nb3Sn wires with a Sn content further from stoichiometry attested a decline of the critical current density at such high fluences. We show that radiation induced point-pinning centers rather than an increase of the upper critical field are responsible for this Jc enhancement, and argue that these results call for further research on pinning landscape engineering., 6 pages, 4 figures; to be published in Scientific Reports

Glass fiber reinforced plastics (GFRPs) are usually employed as insulating materials for the superconducting coils of large fusion magnets, e.g. of the International Thermo-nuclear Experimental Reactor (ITER). Both the radiation spectrum and the stresses at the magnet location significantly influence the mechanical behavior of the magnet insulation and, therefore, impose high demands on the material performance. During the last decades, advanced epoxy based GFRPs with improved mechanical properties and radiation hardness were introduced into fusion technology. More recently, cyanate ester (CE) matrix systems have become of special interest. In this paper, various magnet insulation systems containing boron-free glass fiber reinforcements in commercial and new epoxies as well as in pure CE and CE/epoxy/polyimide/bismaleimide blended matrix systems, are presented. All systems were irradiated in a fission reactor at ambient temperature (∼340 K) to a fast neutron fluence of 1 × 1022 m−2 (E > 0.1 MeV) and beyond. The mechanical properties were assessed at 77 K in tension as well as in interlaminar shear prior to and after irradiation under static and dynamic conditions.

Large single grains of Y–Ba–Cu–O (YBCO) bulk superconductor of up to 32 mm in diameter have been fabricated by a seeded infiltration and growth (IG) technique. Small Y 2 BaCuO 5 (Y-211) particles are observed in the seeded IG sample microstructure, albeit with a rather inhomogeneous distribution in the superconducting YBa 2 Cu 3 O y (Y-123) phase matrix. Values of magnetic critical current density, J c , measured in self-field along the a and c growth sectors of the bulk samples prepared by seeded IG appear higher than the corresponding values for samples fabricated by conventional top seeded melt growth (TSMG), despite the inhomogeneous distribution of Y-211 particles in the former. A maximum trapped field of 0.42 T at 0.2 mm above the sample surface was observed at liquid nitrogen temperature (the actual mean temperature during measurement was around 78 K) in samples fabricated by seeded IG due to the increased J c , despite the relatively small YBCO grain size (25 mm diameter × 7.4 mm thickness). This value of trapped field is almost two times greater than that of samples fabricated by TSMG and of a similar size.

Epoxy based glass fiber reinforced composites are candidate insulation systems for the superconducting magnet coils of fusion devices, e. g. of ITER. Because of their relatively low radiation hardness, the radiation-harder cyanate ester based systems have become of special interest for application in ITER and future fusion devices. This paper presents recent results obtained on pure cyanate ester and cyanate ester/epoxy blends reinforced with R-glass fibers/Kapton H foil. The systems were investigated at 77 K prior to and after irradiation at ambient temperature (340 K) to a fast neutron fluence of 1 × 1022 m−2 (E > 0.1 MeV) in the TRIGA reactor (Vienna). The mechanical material performance was characterized under static load conditions in tension and interlaminar shear. In addition, tension-tension fatigue measurements were carried out to simulate the pulsed operation of ITER and to assess the lifetime performance of these materials. The results show only slight mechanical degradations (by about 5 to 10%) after irradiation.

An important phenomenon in bulk superconductors fabricated by top-seeded-melt growth (TSMG) is the formation of cracks due to the inherent brittleness of the YBa2Cu3O7-δ (Y-123) phase matrix. These form during the fabrication of the superconducting monolith and play an important role in the limitation of current flow. However, cracks may also form during cooling cycles of the sample to liquid nitrogen temperatures. In this investigation, macrocracks along the c-direction, in particular were analyzed microscopically before and after cooling. In addition we attempt to resolve the c-axis macrocrack formation pattern using the magnetoscan technique.

In the present work we visualized the cracks in the {100} type planes which are formed during the oxygenation of top-seeded melt-grown (TSMG) YBCO bulk superconductors and counted their spacing end length. Both parameters of the oxygenation a/c-cracks depend on the distance from the seed. Changes of fracture toughness with 211 concentration and induced thermal dilatation stresses have the most significant effect on the spacing and length of the oxygenation a/c-cracks in the sample with optimized trapped field properties.

The actual limitations for the trapped field in YBa2Cu3O7?? (YBCO) monoliths are discussed. The influence of the sample geometry and of the critical current density on the trapped field is investigated by numerical calculations. The field dependence of the critical current density strongly influences the trapped field. A nonlinear relationship between the sample size, the critical current density and the resulting trapped field is derived. The maximum achievable trapped field in YBCO at 77?K is found to be around 2.5?T. This limit is obtained for reasonable geometries and high but realistic critical current densities. Such high fields have not been reached experimentally so far, due to non-optimized flux pinning and material inhomogeneities. These inhomogeneities can be directly assessed by the magnetoscan technique, and their influence is discussed. Significant differences between the a-?and the c-growth sectors were found. Limitations due to cracks and non-superconducting inclusions (e.g.?211 particles) are estimated and found to be candidates for variations of Jc on a millimetre length scale, as observed in experiments.

Glass fibre reinforced plastics (GFRPs) are usually employed as insulating materials for the superconducting coils of large fusion magnets, e.g. of the International Thermonuclear Experimental Reactor (ITER). Both the radiation spectrum and the stresse sa t the magnet location significantly influence the mechanical behaviour of the magnet insulation and, therefore, impose high demands on the materia lp erformance. During the last few decades, advanced epoxy based GFRPs with improved mechanical properties and radiation hardness were introduced into fusion technology. More recently, cyanate ester (CE) matrix systems have become of special interest. In this paper, various magnet insulation systems containing boron-free R-glass fibre reinforcements in commercial and new epoxies as well as in pure CE and CE/epoxy blended matrix systems are presented. All systems were irradiated in a fission reactor at ambient temperature (∼340 K) to a fast neutron fluence of 1 × 10 22 m −2 (E > 0. 1M eV). The mechanical properties were assessed at 77 K in tension as well as in interlaminar shear prior to and after irradiation under static and dynamic conditions.

The suitability of Hall probe mapping for non-destructive experimental characterizations of YBa2Cu3O7−δ bulk superconductors is discussed. Firstly, the flux penetration pattern, observed by Hall scans of the trapped field after activation in magnetic fields below the complete penetration field in the zero-field cooled (zfc) mode, provides valuable information on the homogeneity of the material. Secondly, the magnetoscan technique is presented, which was also applied to irradiated samples. Investigations of samples from the same batch (prior to neutron irradiation) allow us to draw conclusions about the quality of the batch process.

The application of glass-fiber-reinforced plastics (GFRP's) as insulation materials for fusion magnet coils (e.g. of ITER) requires the full characterization of their mechanical performance under ITER relevant conditions. Tension–tension fatigue is a useful procedure to simulate the pulsed tokamak operation of the ITER coils in the relevant range of 104–105 cycles. The fatigue parameters, such as the R-ratio and the load frequency, may influence the material behavior under cyclic load. Therefore, investigations were made under load control and at 77 K on an industrial glass-fiber-reinforced/epoxy compound. Stress–lifetime diagrams were generated with R-values between 0.1 and 0.5 and frequencies between 5 and 20 Hz. The results are discussed with respect to the lifetime performance of ITER.