The motional stark effect diagnostic at TEXTOR-94

Knowledge of the current distribution in a tokamak is indispensable for an understanding of the energy transport in the plasma and controlling instabilities. A diagnostic exploiting the Motional Stark Effect (MSE) has the potential to obtain this quantity. This is based on a measurement of the polarisation of the Balmer-a light emitted by neutral particles injected into tokamaks. On the tokamak TEXTOR-94 a new MSE system is under development which exploits the full spectral information, along with its polarisation. This system consists of 30 radial channels, measuring the spectrum at two orthogonal angles. This is accomplished by inserting a Glan-Laser prism in the optical path. All the optics is housed in five camera modules and located inside the vessel to improve the radial resolution and minimise changes in polarisation due to optical elements. Fibres transfer the light by a vacuum feedthrough towards a spectrometer. The simple construction of the fibre feedthrough and its reliable operation opens the possibility to observe plasma light at all conceivable angles and positions, irrespective of suitable locations of windows. (C) 2001 Elsevier Science B.V. All rights reserved

Spectra polarimetry of the motional stark effect at TEXTOR-94

The Balmer-alpha light emitted by neutral particles injected into tokamaks is polarized with respect to the Lorentz electric field experienced by these atoms: E-l = nu xB, known as the motional Stark effect (MSE). On TEXTOR-94 a new MSE system is under development which exploits the full spectral information, along with its polarization. The advantages of exploiting the full spectral information are obvious: beam velocity, observation volume, absolute value of B, the plasma radial electric field and the beam density can in principle all be extracted from the measurement, whereas the polarization can be detected as several lines simultaneously. The TEXTOR-94 MSE system consists of 30 radial channel, of which the full Balmer-alpha spectrum is measured at two orthogonal angles. This is accomplished by inserting a Glan-Laser prism in the optical path. All the optics is located inside the vessel to improve the radial resolution and minimize changes in polarization due to optical elements. Fibers transfer the light by a vacuum feedthrough towards a spectrometer. It is shown that the measured spectra can be adequately fitted. The accuracy for determining the safety factor q is estimated to be 10%-15% and for the radial electric field to be 30 kV/m. (C) 2001 American Institute of Physics

A Fast Shutter Valve for Use in Plasma Diagnostics

A fast shutter valve, designed for operation in high-vacuum plasma physics experiments, is described. By electromagnetically induced movement of the shutter blade, opening and shutting times of the order of 10 ms have been achieved. The results of test measurements of the shutter velocity and of the gas resistance in the closed position are presented. Furthermore, the specific use of the shutter valve in a time-of-flight experiment is discussed

Applying principles of Design For Assembly to ITER maintenance operations

In ITER, maintenance operations in the vessel and in the Hot Cell will be largely done by Remote Handling (RH). Remotely performed maintenance actions tend to be more time-costly than actions performed by direct human access. With a human operator in the control loop and adequate situational feedback, a two-armed master slave manipulator system can mimic direct access with dexterous manipulation, tactile feedback and vision. But even then, turnaround times are still very high. Adapting the design for simplified maintenance operations can yield significant time savings. One of the methods known to produce a simpler, more robust design, which is also better suited for handling with robots, is Design For Assembly (DFA). This paper discusses whether and how the principles of DFA can be applied to simplify maintenance operations for ITER. While DFA is normally used with series-production and ITER is a unique product. it is possible to apply the principles of DFA to ITER maintenance operations. Furthermore, DFA\u27s principles can be applied at different abstraction levels. Combining principles of DFA with Virtual Reality leads to new insights and provides additional value. (C) 2008 Elsevier B.V. All rights reserved

Risk mitigation strategy for the ITER electron cyclotron upper port launcher

A basic requirement for ITER equipment to meet is a high level of reliability, because ITER operation time is precious and radioactive operation leaves limited scope for repair. In order to reduce the risk of failure during ITER operation an effective risk mitigation strategy is necessary. This paper presents such strategy for the ITER electron cyclotron upper port launcher (ECUPL). A preliminary ECUPL risk analysis identifies possible failure modes. A probabilistic risk assessment quantifies the risk of failure using a 4 x 4 impact-likelihood matrix. Impact is quantified through technical, cost and schedule elements. Likelihood depends on the risk mitigation strategy adopted. A cost benefit analysis determines the most cost effective risk mitigation strategy. An essential element in risk mitigation is the testing of equipment prior to installation on the ITER machine. This paper argues the need for low- and highpower millimetre wave tests carried out on the fully assembled ECUPL It presents a conceptual design for a dedicated on-site test bed that can handle 2 of 8 microwave beams at 2 MW long pulse operation. (C) 2010 Elsevier B.V. All rights reserved