There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The major increase in discharge duration and plasma energy in a next step DT fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety and performance. Erosion will increase to a scale of several centimetres from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma facing components. Controlling plasma-wall interactions is critical to achieving high performance in present day tokamaks, and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena stimulated an internationally co-ordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor project (ITER), and significant progress has been made in better understanding these issues. The paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next step fusion reactors. Two main topical groups of interaction are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation and (ii) tritium retention and removal. The use of modelling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R&D avenues for their resolution are presented.

/pdf/plasma-material-interactions-in-current-tokamaks-and-their-1a6iwv89x6.pdf

Plasma{material interactions in current tokamaks and their implications for next step fusion reactors

This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

http://liu.diva-portal.org/smash/get/diva2:303552/FULLTEXT01

The Mn+1AXn phases: Materials science and thin-film processing

The MAX phases are a group of layered ternary compounds with the general formula Mn+1AXn (M: early transition metal; A: group A element; X: C and/or N; n = 1–3), which combine some properties of metals, such as good electrical and thermal conductivity, machinability, low hardness, thermal shock resistance and damage tolerance, with those of ceramics, such as high elastic moduli, high temperature strength, and oxidation and corrosion resistance. The publication of papers on the MAX phases has shown an almost exponential increase in the past decade. The existence of further MAX phases has been reported or proposed. In addition to surveying this activity, the synthesis of MAX phases in the forms of bulk, films and powders is reviewed, together with their physical, mechanical and corrosion/oxidation properties. Recent research and development has revealed potential for the practical application of the MAX phases (particularly using the pressureless sintering and physical vapour deposition coating rout...

Progress in research and development on MAX phases: a family of layered ternary compounds

Carburization depth evaluation from magnetic nondestructive testing

Electromagnetic pulse-induced acoustic testing enables reliable evaluation of debonding between rebar and concret

Mechanical properties of cast irons strongly depend on the graphite morphology and the matrix structure, thus both of them should be evaluated for their characterization. The former can be evaluated by ultrasonic testing (UT), and the latter can be evaluated by eddy current testing (ECT). Considering the background above, this study proposes a novel method for the material characterization of cast irons with an EMAT/EC dual probe. For this purpose, we conducted UT and ECT for cast irons with different graphite morphology and matrix structures with the present probe. As a result, correlations betwe en the nodularity of graphite and ultrasonic velocity, and between one the pearlite ratio and EC signals were obtained. These results imply that the EMAT/EC dual probe is effective for the material characterization of cast irons. Cast iron is an Fe-C base alloy that contains iron as the princ ipal ingredient and carbon more than 2%. It is useful engineering material due to its excellent mecha nical properties, such as strength, ductility, free cutting, and productivity. Accordingly, it is widely used f or the parts of automobiles, industrial machinery and so forth. However, the manufacturing process of casting is complex, and the microstructure control is difficult. Therefore, nondestructive characterization of mechanical properties of cast irons is necessary and one of key issues in the foundry industry. The structure of cast irons consists of graphite and a steel matrix. Mechanical properties of cast irons depend on the graphite morphology and the matrix structure, thus both of them should be evaluated for their characterization. The nodularity of cast irons is estimated by measuring the ultrasonic velocity, and the method is established (1). The matrix structure and hardness of cast iron are estimated by measuring the EC signals of ductile cast irons (2). Therefore, the graphite morphology and matrix structure can be evaluated by ultrasonic testing (UT) and eddy current testing (ECT), respectively. We have proposed an EMAT/EC dual probe (3) that can obtain ultrasonic and EC signals with a single probe structure. This probe was applied to the evaluation of wall thinning of pipes, and the feasibility of the nondestructive evaluation based on the complementarity between ECT and UT was verified. This paper proposes a new method for the material characterization of cast irons with an EMAT/EC dual probe. The material properties of cast irons are not uniform and should be characterized with respect to each point. The dual probe with a single and compact structure can acquire UT and EC signals

Material characterization of cast irons with an EMAT/EC dual probe

Electromagnetic acoustic resonance method (EMAR) is promising for online monitoring of pipes wall thinning with corrosion during operation. However, the improvement of measurement accuracy is one of issues to be solved, although some signal processing methods such as superposition of nth compression method (SNC) have been proposed in order to improve the accuracy of wall thickness estimation. In this study, for the purpose of highly accurate evaluation of the wall thickness, the thickness of 51 corrosion specimens was measured and compared with the true thickness obtained by 3D laser scanner. The fundamental resonance frequency of EMAR signal spectrum was evaluated by discrete Fourier transform method (DFT) and SNC method, and the wall thickness was calculated. As a result, evaluated thickness by EMAR almost corresponded to the average of true thickness. The accuracy of the evaluated thickness by the SNC method depends on the method to set the postulated thickness for determining the number of compressions. It was found that using the evaluated thickness by the DFT method for determining the number of compressions improved the estimation accuracy of the evaluated thickness by the SNC method. In addition, it was confirmed the estimation accuracy of this evaluated thickness was higher than that of the evaluated thickness by the DFT method. 

Development of signal processing method to measure wall thickness of corrosion specimens by electromagnetic acoustic resonance method

This paper presents study on application of high Tc superconductors as a ripple reducer for reduction of the toroidal field (TF) ripple without changing the design of TF coils. The feasibility of the ripple reducer is first demonstrated on the basis of experiments. Next, parameter survey of the ripple reducer is performed for the configuration of the outline design of ITER, and a guideline for the design of the ripple reducer is presented with the consideration of constraints from the technological viewpoint of the fusion reactor.

Tetsuya Uchimoto

Papers

Carburization depth evaluation from magnetic nondestructive testing

Electromagnetic pulse-induced acoustic testing enables reliable evaluation of debonding between rebar and concret

Material characterization of cast irons with an EMAT/EC dual probe

Development of signal processing method to measure wall thickness of corrosion specimens by electromagnetic acoustic resonance method

Study on High Tc Superconducting Ripple Reducer