[en] The instrumentation and control of 1450 MW EDF nuclear reactor cores makes widespread use of network techniques as a means of distributing intelligence. This type of application requires a high processing capacity, low response times and, above all, maximum operating safety. By distributing intelligence into several operationally independent units connected to each other by high capacity networks. The first two conditions were fully satisfied. The correct operation of the whole system is, however, fully dependent on the correct operation of the network. The NERVIA network has therefore been developed to respond to both performance and operational safety requirements. This latter requirement is ensured by three basic properties: determinism, self-tests and fault tolerance. It should be pointed out that it is the only network currently on the market which can offer these three properties simultaneously. (author)

[en] This study investigates the chemical stability of pyrolytic boron nitride obtained from BCl₃--NH₃ reaction. BN in contact with refractory metals is unstable at high temperature, but should be stable with ceramics (Al₂O₃, etc.) above 800⁰C

No abstract available

[en] The present developments in plasma fusion research show a trend towards an almost continuous plasma heating requirement. The pulse length foreseen on TORE SUPRA project is between 30 and 210 seconds. Power tetrodes used for cyclotronic heating must be built in order to sustain stresses during normal operation which depend on four parameters: - output power -VSWR - upper operating frequency - pulse length. The outcoming tetrode is a trade off between contradictory constraints depending on these four parameters. The calculation of the power dissipated on each electrode resulting from a theoretical approach to the problem allows to determine the thermal stress on each part of the tube. Tube design and materials can be selected in order to reduce and to withstand these stresses. (author)

[en] The diacrode concept has been already successfully developed and tested by Thomson Tubes Electroniques. Demonstration is done that ITER project requirements cannot be met with a single tetrode power amplifier but with one new diacrode, the design of the RF circuit around which is hereafter proposed. (author)

[en] Recent advances in accelerator technology are now making possible the operation of high duty factor or CW facilities. Emphasis is therefore frequently put on accelerators designed not only on purely technical factors, but also on cost criteria. From this point of view, the efficiency of high power RF sources feeding the electromagnetic power to the accelerating structures becomes an important issue in the design of a modern accelerator. It is thus important to consider the efficiency of high power RF sources in a very objective manner and to examine advantages and drawbacks for each possible RF generator. The objective of this paper is to give a broad survey of this issue and to clarify this performance and its consequences

[en] The present developments in plasma fusion research show a trend towards an almost continuous plasma heating requirement. The pulse length foreseen on TORE SUPRA project is between 30 and 210 seconds. Power tetrodes used for cyclotronic heating must be built in order to sustain stresses during normal operation which depend on four parameters: - output power; - VSWR; - upper operating frequency; - pulse length. The outcoming tetrode is a trade off between contradictory constraints depending on these four parameters. The calculation of the power dissipated on each electrode resulting from a theoretical approach to the problem allows to determine the thermal stress on each part of the tube. Tube design and materials can be selected in order to reduce and to withstand these stresses

[en] The trend towards longer pulses at higher power levels and frequencies shown in the recent years in the ICRH field has imposed new challenges to electron tube manufacturers. This paper presents answers to meet the requirements of machines such as JET and TORE SUPPRA. The design of the new tubes has been completely reworked. The new tubes have been tested both in the Thomson-CSF special test amplifier and in the JET amplifiers. The latest results obtained from these tests and during operation of the JET machine are detailed. The associated circuits are also essential for the good operation of the tubes. The power x frequency product encountered often leads to the use of coaxial cavities. The main parameters of these cavities are presented