[en] In this paper the design of a poloidal air core field system to produce plasma current in a large RFP experiment is presented. The electromagnetic system consists of two independent windings; the field shaping winding and the magnetizing winding. The first one is designed to provide a magnetic field distribution around the outer surface of the metal shell equal to the field distribution produced by the plasma current on the inner surface; if this condition is fulfilled any field mismatch on the shell surface at the minor gap is avoided. The magnetizing winding consists of a number of coils arranged out-side the shell in order to obtain a flux swing of 12.5 Wb, in unipolar operation, with stray fields in the plasma region not exceeding 10^-₂ T to give a maximum flux line deviation at the edge of the plasma not exceeding 10 mm. For a proper operation of the two windings; further bonds must be verified by their parameters and by their connections to the power supplies. The results obtained by numerical computations show that the above conditions can be achieved. In the paper the main concepts followed in the design and the main features and parameters of the electromagnetic system are presented and discussed. (author)

[en] Some modifications have been introduced in Eta-Beta II in order to achieve information about the expected behavior of the next generation of RFP machines. The inductor have been changed, thus increasing the rise time of the plasma current up to 0.5 ms; and active crowbar has been added, in order to extend the duration of the discharge. Moreover a detailed analysis of the inductor system has been carried out and a new equivalent network is proposed to simulate more accurately the machine behavior at the longer cooperating times

[en] A new power crowbar system has been recently assembled in Eta-Beta II, both in the poloidal and in the toroidal circuits, in order to sustain and extend as long as possible the plasma pulse and to achieve an effective flat-top phase. Starting from plasma physical specifications, a crowbar system made with capacitor banks in a direct parallel connection for both circuits has been chosen since they were considered the most suitable in the concerned range of power and energy. Both systems include an original protection system of the main capacitor bank against casual or systematic dangerous currents and voltages. This protection system required a careful optimization of many involved component as capacitors, inductances and diodes. The main steps in the design of the systems is described and emphasis is given to the analysis of original problems which were solved, such as direct parallel connection of more ignitron series. Finally the tests performed on the circuits and components are presented and the performances of the systems are shown and discussed

[en] The CREATE-L linearized plasma response model can simulate the plasma current, position and shape responses to external coil currents and internal physical variations, also in the presence of 3D conducting structures whose eddy currents cannot be neglected. It has already been validated on existing tokamaks (TCV, FTU) and applied to tokamak under design (ITER) in order to investigate their control system capabilities. On these devices it has also allowed the design of high-order controllers. This paper presents the extension of the CREATE-L model to reversed field pinch (RFP) plasmas. The validation of this new model has been carried out against experimental data from RFX, the largest RFP machine

[en] RFX, the largest machine for magnetic confinement of plasmas in the RFP line, is provided with a system named SGPR specifically designed for the machine global protection against fast faults which can develop in the plasma, in the windings, in the power supply circuits and in the control system. SGPR is a cabled logic HLL machine, able to organise in few tens of microseconds coordinated machine protection, dealing with more than forty fault signals and activating almost thirty protection commands. SGPR design, manufacture and test program conform the quality control criteria necessary to assure the required high reliability. After a careful and cumbersome commissioning work the system has assumed its protection role. Up to now it has been called to a number of interventions which, even if never due to major faults, have shown its capability of proper operation

[en] The paper presents the main concepts which are at the basis of the active control design for the RFX poloidal field system. A computer model is then described, including plasma and electrical network dynamics, axisymmetric field calculation, and discontinuous shell effects. The shell is modelled by a simple lumped-parameter circuit whose currents coincide with the Fourier components of the toroidal current densities on the wall: the associated field distortions inside the vessel are then computed. The results of an open-loop analysis are presented for different programmed sets of control voltages. The power capabilities of the thyristor amplifiers in controlling the plasma position are finally discussed

[en] This paper presents the RFX Magnetizing Winding design and describes its most significant features. Two numerical codes have been used for the magnetic design and a number of solutions, complying with the design specifications, have been obtained. The most attractive of them have been studied in detail from the electromagnetic point of view and a comparison is given here together with an analysis of the stress states. The finite element procedure used is discussed in the paper and the results of the comparison indicated above are presented together with the main electromagnetic parameters and winding features

[en] The main aspects of the electromagnetic system design in large Reverse Field Pinch devices are analysed with the aim of deriving some preliminary design criteria and of optimizing the overall dimensions of the machine with respect to suitable ''quality indexes''. The peak plasma current is assumed to be the basic free parameter. Simple scaling laws for the main physical quantities are firstly reported. The toroidal and poloidal field systems are then analyzed in detail: the fundamental procedures in designing the windings and their power supplies are described with reference both to the electrical and to the mechanical aspects of the problem. Finally, for machines producing 2 to 6 MA of plasma current, the impact of the basic dimensional choices on the electromagnetic system cost and on the d-c installed power is discussed. (author)

[en] The protection of the Windings of RFX against fast electric faults relies on an original dedicated Fast Protection System able to operate within 1 ms. The first ring of the protection chain is the fault protection system of the winding, named RGM, that consists of: about a hundred highly reliable voltage and current probes, all electric signal lines and an analog-digital device where signals are processed and logic alarms are generated. RGM is an original machine that required a careful design and manufacturing work. After a long test and adjustment phase it now operates properly. It has already operated against some earth faults which, due to low level of earth current, were not dangerous for the machine but very hard to detect

[en] Modelling ionic conduction polymeric proton-exchange membranes at the heart of fuel cells requires the solution of highly nonlinear partial differential equations in very thin domains. Recently, proper generalized decomposition methods have emerged as particularly promising methods for this type of problems. This paper introduces the basics of this novel class of approaches and highlights their potential benefits.