The development of a large-area RF source for negative hydrogen ions, an official EFDA task agreement, is aiming at demonstrating ITER-relevant ion source parameters. This implies a current density of 20 mA/cm 2 accelerated Dions at a source filling pressure of ≤ 0.3 Pa and an electron to ion ratio of ≤ 1 from a PINI-size extraction area for pulse lengths of up to 1 hour. The work is progressing along three lines in parallel: (i) optimisation of current densities at low pressure and electron/ion ratio, utilising small extraction areas (< 100 cm 2) and short pulses (< 10 s); (ii); investigation of extended extraction areas (< 300 cm 2) and pulse lengths of up to 3600 s; (iii) investigation of a size-scaling on a half-size ITER plasma source. Three different testbeds are being used to carry out those investigations in parallel. An extensive diagnostic and modelling programme accompanies the activities. The paper contains the recent achievements and the status of preparations in those four areas of development

After herbivore attack, plants launch a suite of direct and indirect defense responses that must be coordinated if plants are to realize a fitness benefit from these responses. Here we characterize the volatile emissions in the native tobacco plant, Nicotiana attenuata Torr. ex Wats., that are elicited by tobacco hornworm (Manduca sexta L.) attack and are known to function as attractants for parasitoids. To provide the first ecophysiological comparison of examples of both types of defense in the same species, we characterize the elicitation and signaling mechanisms, the resources required, and the potential costs and benefits of the volatile release and compare these traits with those of the well-described induced direct defense in this species, nicotine production. The release of (E)-β-ocimene, cis-α-bergamotene and linalool is dramatically induced within 24 h by application of methyl jasmonate (MeJA), caterpillar feeding, and the treatment of mechanical wounds with larval oral secretions (OS), but not by mechanical damage alone. Plants from different geographic locations produce volatile blends that differ in composition. The most consistently released component from all genotypes, cis-α-berga-motene, is positively related to the amount of MeJA and the level of wounding if OS are applied to the wounds. The volatile release is strongly light dependent, dropping to undetectable quantities during dark periods, even when temperatures are elevated to match those of the light period. Inhibitors of wound-induced jasmonate accumulation (salicylates and auxins), which are known to inhibit wound-induced nicotine production, do not inhibit the release of volatiles. By individually inducing different leaf positions with OS and, on other plants, excising them after induction, we demonstrate that the emission is largely a systemic, whole-plant response, which is maximally triggered when the second fully expanded leaf is induced. We conclude that while both are whole-plant, systemic responses that utilize recently acquired resources for their production and are activated by the jasmonate cascade, the elicitation of the volatile release exhibits greater tissue sensitivity and utilizes additional signaling components than does nicotine production. In contrast to the large investment of fitness-limiting resources required for induced nicotine production or the resources used in benzyl acetone release from flowers for pollinator attraction, the resource requirements for the volatile release are minor. Hence the argument that the volatile release incurs comparatively large physiological costs cannot be supported in this system.

Development of negative hydrogen ion sources for neutral beam systems is closely linked with an optimisation of negative ion formation in hydrogen plasmas which requires knowledge of the plasma parameters. Emission spectroscopy is introduced as a non-invasive and in-situ diagnostic tool for line of sight averaged plasma parameters. Diagnostic lines and simplified analysis methods for a variety of plasma parameters, such as electron density and electron temperature, gas temperature, atomic and molecular hydrogen density as well as cesium densities (atoms and ions) and negative ion densities are identified and prepared for direct application. Emphasis is laid on results obtained in RF generated negative ion sources. Correlations of plasma parameters with extracted negative ion current densities are discussed. Stripping losses in the extraction system are quantified by using beam emission spectroscopy.

In ASDEX Upgrade, experimental efforts aim to establish pace making and mitigation of type-I edge localized modes (ELMs) in high confinement mode (H-mode) discharges. Injection of small size cryogenic deuterium pellets (∼(1.4 mm)2 × 0.2 mm ≈ 2.5 × 1019 D) at rates up to 83 Hz imposed persisting ELM control without significant fuelling, enabling for investigations well inside the type-I ELM regime. The approach turned out to meet all required operational features. ELM pace making was realized with the driving frequency ranging from 1 to 2.8 times the intrinsic ELM frequency, the upper boundary set by hardware limits. ELM frequency enhancement by pellet pace making causes much less confinement reduction than by engineering means like heating, gas bleeding or plasma shaping. Confinement reduction is observed in contrast to the typical for engineering parameters. Matched discharges showed triggered ELMs ameliorated with respect to intrinsic counterparts while their frequency was increased. No significant differences were found in the ELM dynamics with the available spatial and temporal resolution. By breaking the close correlation of ELM frequency and plasma parameters, pace making allows the establishment of fELM as a free parameter giving enhanced operational headroom for tailoring H-mode scenarios with acceptable ELMs. Use was made of the pellet pace making tool in several successful applications in different scenarios. It seems that further reduction of the pellet mass could be possible, eventually resulting in less confinement reduction as well.