Electron Cyclotron Resonance Heating (ECRH) is the main heating method for the Wendelstein 7-X Stellarator (W7-X), which is under construction at IPP-Greifswald.A 10 MW ECRH plant with CW-capability at 140 GHz is under construction to meet the scientific objectives. The microwave power is generated by 10 gyrotrons with 1 MW each, two gyrotrons are operational at IPP in Greifswald. The tubes are equipped with a single-stage depressed collector for energy recovery and operate with an output power modulation between 0.3 and 1 MW with a sinusoidal frequency of up to 10 kHz, which is achieved by modulating the depression voltage and is an interesting feature for NTM control at ITER. The general features of the ECRH-plant such as frequency, power, cw-capability, flexibility and the experimental experience are of high relevance for the ITER system.Each gyrotron is fed by two high-voltage sources. A high-power supply for driving the electron beam and a precision low-power supply for beam acceleration. The high-power facility consists of modular solid state HV-supplies (-65 kV, 50/100 A) providing fast power control and high flexibility. The low-power high-voltage source for beam acceleration is realized by a feed back controlled high-voltage servo-amplifier driving the depression voltage. A protection system with a thyratron crowbar for fast power removal in case of gyrotron failure by arcing is installed. Both the high power and low-power high-voltage sources have the capability to supply a 2 MW ITER gyrotron without any modification. Analogue electronic devices control the fast functions of the high-voltage system for each gyrotron and a hierarchy of industrial standard PLCs and computers supervise the whole ECRH-plant.

Electron Cyclotron Resonance Heating (ECRH) is the main heating method for the Wendelstein 7-X Stellarator (W7-X), which is the next step device in the stellarator line of IPP and is presently under construction in the Greifswald branch of IPP. The experiment aims at demonstrating the inherent steady state capability of stellarators at reactor relevant plasma parameters. W7-X (major radius 5.5 m, minor radius 0.55 m) is equipped with a superconducting coil system operating at 3 T for steady state operation and a divertor for 10 MW steady state heat removal. A 10 MW ECRH plant with CWcapability at 140 GHz is under construction to meet the scientific objectives. The microwave power is generated by 10 gyrotrons with 1 MW each. A European R&D program aiming at the development of a prototype gyrotron for W7-X has been successfully terminated by fall of 2002. A prototype gyrotron with the same specifications was developed for W7-X at CPI (USA). Test results and limitations are reported. The distinct microwave beams from each gyrotron are combined and transmitted to the W7-X Stellarator ports by an open quasi-optical transmission system with high transmission efficiency, which runs at normal pressure and consists of water cooled imaging mirrors. Cold tests of a full size, uncooled prototype line and the related RF-diagnostics are presented. The microwave power is launched to the plasma through 10 synthetic diamond barrier windows and in-vessel quasi-optical plug-in launchers, which allow an independent steering of each beam. The commissioning of the ECRH plant is well under way and the status is presented.

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In the project Wendelstein 7-X (W7-X), the popular fieldbus Profibus has been determined as a uniform connection between the central control system and all the subordinate systems. A universal embedded control system has been developed for W7-X power supply controlling. Siemens 80C167CR microcontroller is used as the central control unit of the system.With a user-defined printed circuit board (PCB) several control buses, i.e., Profibus, CAN, IEEE 488, RS485 and RS 232 have been connected to the microcontroller. The corresponding hardware interfaces for the control buses have been designed. A graphic liquid crystal display(LCD) and a user-defined keyboard are used as user interface. The control software will be developed with a C-like language, i.e., C166 for the controller.

Abstruct-High-quality c-axis oriented YNi,B,C (transition temperature T,=15K) and ErNi,B,C (TC=9.5K) borocarbide superconducting thin films were grown "in-situ" on MgO and sapphire substrates by planar magnetron sputtering. Here we report data on the temperature, DC and RF magnetic field dependent surface impedance of the films and discuss them in view of possible applications. The YNi,B,C films displayed the behavior expected for BCS-like superconductors, while the microwave response of the antiferromagnetically ordering compound ErNi,B,C was distinctly different. The field dependent surface resistance of both types of films displayed granular effects.