[en] Confinement properties of a reversed field pinch (RFP), TPE-1RM20, are intensively presented. Plasma current, I_p, dependencies of confinement properties are particularly shown in comparison with the forerunner machine, TPE-1RM15. The results without any active density controls are presented in this paper. It is shown that both machines have almost the same, relatively high, I/N values (<= 12 x 10^-14 Am) and the poloidal beta, Β_p (= 0.1) and they do not change very much with I_p, where N is the column density. The energy confinement time, τ_E, linearly increases with I_p and the behavior of the resistive part of the loop voltage has an important role to the I_p dependence of τ_E. 8 refs., 3 figs

[en] A one-dimensional position sensing device is described which produces an electrical signal proportional to the position of maximum light intensity imaged upon its light detecting element. The device uses a segmented photodiode but the position resolution is significantly better than the segment width, which is the resolution that would be obtained using a purely digital circuit. The device is also quite fast with a delay plus rise time of about 50 nsec

[en] The Scylla IV-P is a flexible, linear experiment to support the toroidal Scyllac experiments and to investigate high-density, linear theta-pinch concepts. The experimental arrangement and construction status are described

[en] Scylla I-C is a small scale (1-meter) research theta pinch developed for the experimental investigation of basic plasma physics processes and advanced concepts. The properties and stability characteristics of the Scylla I-C plasma, over a range of initial fill pressure from 100-500 mTorr D₂, are discussed

No abstract available

[en] In this paper, the effect of the conduction wall on reversed field pinch (RFP) plasma is modeled by a mean radial magnetic field B_r < 0 or B_r > 0, respectively, relevant to the experiments with insertion of limiters or removal of limiters. It is shown that when B_r < 0, the mean magnetic field energy is converted into the mean velocity field energy, which is dissipated by the viscosity of ions and when B_r > 0, the contrary is the case. In the former case, if the ion and electron thermal loss rates are unchanged, the electron temperature will decrease and the ion temperature, plasma resistance and loop voltage will increase. In the latter case, the magnetic energy is dissipated by the resistivity of electrons. As a result, the electron temperature increases and the ion temperature, plasma resistance and loop voltage decrease. Especially, when B_r ≅ 0, the oscillations in the ion and electron temperatures, the plasma resistance and the loop voltage take place. (author)

[en] Scylla IV-P is a 5-m linear theta pinch at the Los Alamos Scientific Laboratory primarily used to study end effects of linear theta-pinch plasmas. One method that may be used to reduce plasma end loss from linear theta pinches is to insert material end plugs. Two different assemblies that insert end plugs have been fabricated and installed on Scylla IV-P. The presence of the material end plugs have been found to increase the plasma confinement time by 20 to 30 percent; the plasma stability is increased (the m = 1 wobble is suppressed), and the neutron production is not degraded. The design of the end plug insertion mechanisms is described in some detail and information is presented on end plug erosion. Material eroded from the end plug must be either removed by the vacuum system or it plates out on the vacuum system surfaces. A condensed gas end plug has been proposed to eliminate problems associated with ablated solid material; a third end plug assembly for this is being designed which inserts a cryostat coated with a condensed gas. A prototype of this cryogenically cooled end plug (cryo-plug) has been fabricated and tested. These data are presented and the insertion mechanism described

[en] New data from the Reversed Field eXperiment (RFX) are presented and analysed, which provide a deeper understanding of pellet experiments in a reversed field pinch. In particular, evidence on the ablation cloud density, ablation rate and homogenization process are given by the measurements of two mid-infra-red interferometers located at different toroidal locations, one of which is at the same poloidal plane as the pellet injector. For each pellet, the measurement of the latter interferometer displays a huge peak, which is due to the crossing of the interferometer chord by the ablation cloud. Its analysis yields information on the cloud dimension and radial density distribution. The typical cloud density is much lower than that measured in tokamaks. Due to such a low density, the stopping power of the ionized part of the ablation cloud is weak. As a result the ablation rate is higher than in tokamaks. Another characteristic of the density increase measured by both of the interferometers is the absence of dense plasma structures propagating for long distances along field lines. This proves that the distance necessary for the ablated material to become incorporated into the plasma is less than about 4 m in the core of the discharge, due to a rapid mixing of the ablated material. Despite the different features displayed by pellet injection experiments in reversed-field pinches and tokamaks, the ablation and homogenization of the deposited material can be described within the same general frame for both magnetic configurations. The differences arise mainly because of the different magnetic field topologies and values of the transport coefficients in the two machines. (author)

[en] A cross-check analysis of the plasma wall interaction in RFX-mod is presented. Different methods to determine the footprint of the interaction are compared. The issue is particularly important for the plasma performances, due to the presence of a quasi-stationary distortion of the plasma surface related to the phase locking of the dynamo modes. We show a good agreement between the different analysis and an important reduction of the phenomenon in the discharges with active feedback control of the magnetic boundary

[en] The results leading to the identification of coherent structures emerging from the background turbulence in the edge region of the reversed field pinch experiments EXTRAP-T2R and RFX are reviewed. These structures have traits of vortices in velocity field and blobs in density, and the reconstruction of their spatial structure and of their time evolution is discussed focusing on the analysis tools applied. The role of these structures in the particle anomalous transport is addressed, showing that their collisions can contribute up to 50% the total particle losses. This process is shown to be responsible for bursts in particle flux and it is found to set a characteristic collision time, which is in agreement with the statistical properties of laminar times for particle flux bursts