A line-of-sight electron cyclotron emission receiver for electron cyclotron resonance heating feedback control of tearing modes

An electron cyclotron emission (ECE) receiver inside the electron cyclotron resonance heating (ECRH) transmission line has been brought into operation. The ECE is extracted by placing a quartz plate acting as a Fabry¿Perot interferometer under an angle inside the electron cyclotron wave (ECW) beam. ECE measurements are obtained during high power ECRH operation. Thisdemonstrates the successful operation of the diagnostic and, in particular, a sufficient suppression of the gyrotron component preventing it from interfering with ECE measurements. When integratedinto a feedback system for the control of plasma instabilities this line-of-sight ECE diagnosticremoves the need to localize the instabilities in absolute coordinates

The target for the new plasma/wall experiment Magnum-PSI

The construction of Magnum-PSI is in its final stage. The aim is to provide a controlled and highly accessible linear plasma device to perform the basic plasma-surface interaction research needed for the design of the plasma facing components of future fusion devices. This contribution will focus on the thermal challenges imposed by those extreme conditions on the design of the target holder of Magnum-PSI.The target holder is designed to allow the exposure of large size targets with variable inclination angles with respect to the magnetic field. A test set up was made to test different interlayers (grafoil (R), soft metal sheets) and improve the thermal contact between the target and the heat sink. In addition, a modular target holder for sequential exposure of smaller size targets has been designed. Finite element modeling using the ANSYS code was used to optimize the cooling geometry and to predict the temperature profiles due to the heat load of the plasma. Experiments were done on the Pilot-PSI linear device to validate the thermal calculations. Calorimetry and infrared thermography were used to experimentally measure the temperature profile on the target and the heat deposition. (C) 2011 Elsevier B.V. All rights reserved

The target for the new plasma/wall experiment Magnum-PSI

The construction of Magnum-PSI is in its final stage. The aim is to provide a controlled and highly accessible linear plasma device to perform the basic plasma-surface interaction research needed for the design of the plasma facing components of future fusion devices. This contribution will focus on the thermal challenges imposed by those extreme conditions on the design of the target holder of Magnum-PSI. The target holder is designed to allow the exposure of large size targets with variable inclination angles with respect to the magnetic field. A test set up was made to test different interlayers (grafoil (R), soft metal sheets) and improve the thermal contact between the target and the heat sink. In addition, a modular target holder for sequential exposure of smaller size targets has been designed. Finite element modeling using the ANSYS code was used to optimize the cooling geometry and to predict the temperature profiles due to the heat load of the plasma. Experiments were done on the Pilot-PSI linear device to validate the thermal calculations. Calorimetry and infrared thermography were used to experimentally measure the temperature profile on the target and the heat deposition. (C) 2011 Elsevier B.V. All rights reserved

The ECW installation at the TEXTOR tokamak

Previous electron cyclotron wave experiments on TEXTOR were performed using a 110 GHz, 350 kW, 200 ms gyrotron. The installation is presently extended with a new gyrotron at 140 GHz, which produces more than 800 kW of RF power in a Gaussian beam for more than 3 s at 1% duty cycle. Auxiliary systems have been overhauled and upgraded. The installation can be conveniently switched between gyrotrons while the control system is kept extremely versatile allowing to switch between manual expert operation and fully automated operation from the TEXTOR control room. A scheme is being developed to allow control of the steerable launcher depending on real-time plasma parameters. (C) 2003 Elsevier Science B.V. All rights reserved

Development of the 140 GHz gyrotron and its subsystems for ECH and ECCD in TEXTOR

A 800 kW, 140 GHz gyrotron has been mounted on TEXTOR. Initial operation was limited by arcs in the transmission line, and by pulse length restrictions due to the expected limited power handling of the window and the launching mirror. Measurements of power absorption in the window and launching mirror, however, showed them to be capable of handling full power, 3 s pulses, while arcing could be prevented by absorption of stray radiation at strategic position in the transmission line. This resulted in the realisation of full power, 3 s pulses on the plasma. Further measures were taken to prevent gyrotron operation in wrong modes or under conditions of low absorption in the plasma. Future improvements, expected to allow further extension of the pulse length to 10 s include: a CVD diamond window to replace the current quartz torus vacuum window, and a fast and accurate launcher. (c) 2005 Elsevier B.V. All rights reserved

Design of a feedback system to stabilise instabilities by ECRH using a combined ECW launcher and ECE receiver

At the TEXTOR tokamak a 140 GHz, 800 kW, 10 s gyrotron is employed for studies on ECW heating and ECCD. A key program is the suppression of tearing modes, which is aided by the unique facility at TEXTOR to program magnetic structures during a discharge (DED). A scheme is under development which aims to detect the perturbations on the electron cyclotron emission caused by these instabilities via the same line of sight as is used by the ECRH beam, and to use this information for feedback control of the instability. A brief overview of TEXTOR and relevant island parameters is given as well as a description of the upgraded ECRH system. This is followed by a description of the design of the transmission line coupler and receiver for island detection which constitutes the main topic of the paper. The final section sketches the feedback controller that processes the receiver signals, and controls the moveable launcher and the gyrotron power

Thermal effects and component cooling in Magnum-PSI

Magnum-PSI is a linear plasma generator, built at the FOM-Institute for Plasma Physics Rijnhuizen. Subject of study will be the interaction of plasma with a diversity of surface materials. The machine is designed to provide an environment with a steady state high-flux plasma (up to 10(24) H(+) ions/m(2) s) in a 3T magnetic field with an exposed surface of 80 cm(2) up to 10 MW/m(2). Magnum-PSI will provide new insights in the complex physics and chemistry that will occur in the divertor region of the future experimental fusion reactor ITER and reactors beyond ITER. The conditions at the surface of the sample can be varied over a wide range, such as plasma temperature, beam diameter, particle flux, inclination angle of the target, background pressure and magnetic field. An important subject of attention in the design of the machine was thermal effects originating in the excess heat and gas flow from the plasma source and radiation from the target. (C) 2011 Elsevier B.V. All rights reserved