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

Speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a single speckle pattern; however, the phase of the difference between two correlated speckle patterns can be determined. This is done by applying phase-shifting techniques to speckle interferometry, which will quantitatively determine the phase of double-exposure speckle measurements. The technique uses computer control to take data and calculate phase without an intermediate recording step. The randomness of the speckle causes noisy data points which are removed by data processing routines. One application of this technique is finding the phase of deformations, where up to ten waves of wavefront deformation can easily be measured. Results of deformations caused by tilt of a metal plate and a disbond in a honeycomb structure brazed to an aluminum plate are shown.

http://www.u.arizona.edu/~kcreath/pdf/pubs/1985_KC_ApplOpt_v24p3053_PSSI.pdf

Phase-shifting speckle interferometry

Automotive disc brake squeal

Microstructure, mechanical properties and residual stresses as a function of welding speed in aluminium AA5083 friction stir welds

Highly sensitive sensor arrays are in high demand for prospective applications in remote sensing and imaging. Measuring microscopic deflections of compliant micromembranes and cantilevers is developing into one of the most versatile approaches for thermal, acoustic and chemical sensing. Here, we report on an innovative fabrication of compliant nanocomposite membranes with nanoscale thickness showing extraordinary sensitivity and dynamic range, which makes them candidates for a new generation of membrane-based sensor arrays. These nanomembranes with a thickness of 25–70 nm, which can be freely suspended over large (hundred micrometres) openings are fabricated with molecular precision by time-efficient, spin-assisted layer-by-layer assembly. They are designed as multilayered molecular composites made of a combination of polymeric monolayers and a metal nanoparticle intralayer. We demonstrate that these nanocomposite membranes possess unparalleled sensitivity and a unique autorecovering ability. The membrane nanostructure that is responsible for these outstanding properties combines multilayered polymer/nanoparticle organization, high polymer-chain orientation, and a pre-stretched state.

/pdf/freely-suspended-nanocomposite-membranes-as-highly-sensitive-2xrgx5egg3.pdf

Freely suspended nanocomposite membranes as highly sensitive sensors

Preface to the first edition Preface to the second edition 1. Basic optical principles 2. Holographic interferometry 3. Speckle pattern interferometry 4. Electronic speckle pattern correlation interferometry 5. Holographic and speckle pattern interferometry techniques for shape measurements 6. Experimental design and technique 7. Applications Appendices References Index.

Holographic and Speckle Interferometry: A Discussion of the Theory, Practice and Application of the Techniques

Electronic speckle pattern interferometry (ESPI) enables static and dynamic surface displacements to be measured in real time to an accuracy of the order of a wavelength of light. The principles of the technique are outlined and the different configurations of interferometers described. Some applications of the technique are discussed.

Catherine Wykes

Papers

Holographic and Speckle Interferometry: A Discussion of the Theory, Practice and Application of the Techniques

Use Of Electronic Speckle Pattern Interferometry (ESPI) In The Measurement Of Static And Dynamic Surface Displacements

Chapter 6 – electronic speckle pattern interferometry

Holographic and speckle interferometry: Electronic Speckle Pattern Correlation Interferometry

Holographic and speckle interferometry: Holographic interferometry