CONDITIONING AND PROTECTION CIRCUITRY FOR EXTERNAL MODULATION OF A PREPROGRAMMED GYROTRON CATHODE VOLTAGE COMMAND WAVEFORM

OAK-B135 The modulating voltages applied to the DIII-D gyrotrons are controlled by reference signals which are synthesized by arbitrary waveform generators.These generators allow ECH operators to pre-program reference waveforms consisting of ramps, flat tops, and various modulation shapes. This capability is independent of the DIII-D central timing and waveform facilities, which provides the ECH operators operational flexibility. The waveform generators include an amplitude modulation input, providing a means to control the pre-programmed waveform externally. This input is being used to allow the DIII-D plasma control system (PCS) to control gyrotron power in response top selected feedback signals. As the PCS control signal could potentially modulate the gyrotrons beyond operational limits or otherwise in a manner leading to recalcitrant rf generation, the control signal is conditioned so that its effect upon the ECH pre-programmed reference waveform is limited by conditions set by the ECH operators. The design of the circuitry which restricts the range over which the PCS control signal may modulate the reference waveform will be discussed. Test and DIII-D experimental results demonstrating the utility and effectiveness of gyrotron power modulated by the PCS will be presented

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Suitability of NIRS analysis for estimating diet quality of pyrenean chamois (Rupicapra pyrenaica)

Ponencia presentada a la 51 Reunión Científica de la SEEP celebrada en la Escuela Superior de Ingenieros Agrónomos de la Universidad Pública de Navarra entre el 14 y el 18 de mayo de 2012.Durante más de seis décadas, el nitrógeno fecal (Nf) ha sido un indicador frecuentemente utilizado para estimar la calidad de la dieta de herbívoros salvajes. La gran estabilidad del Nf posibilita el estudio de las variaciones estacionales y espaciales en la calidad de la dieta de ungulados que habitan en ambientes extremos, como el rebeco. Además, el Nf puede predecirse fácilmente mediante ecuaciones NIRS, aunque no existen referencias en las que se aplique dicha técnica. El objetivo del estudio fue desarrollar y evaluar un modelo de regresión NIRS que permita predecir de forma rápida y eficaz la calidad de la dieta del rebeco. Para ello se recolectaron 192 muestras de heces, desde mayo 2009 hasta septiembre 2010, en dos zonas alpinas de la reserva nacional de caza de Freser-Setcases (Pirineo catalán): Costabona y Fontalba. Se analizaron por el método tradicional DUMAS/LECO como método de referencia y se recogió su información espectral en un equipo NIRSystems 5000 (FOSS). Se evaluaron diferentes tratamientos matemáticos para el desarrollo de los modelos de predicción. Puesto que los patrones estacionales de Nf difirieron entre las dos localidades, se comparó la calibración obtenida usando el global de muestras con las calibraciones individuales de cada zona muestreada. Aunque las calibraciones parciales obtenidas mejoran algunos estadísticos, la calibración global obtenida (R2=0,97; SEC=0,076; r2=0,97; SEP=0,109) es suficientemente robusta, garantizando la predicción adecuada del Nf. Los resultados obtenidos indican que la tecnología NIRS evalúa con exactitud y precisión el contenido en Nf en heces de rebecos.For more than six decades, Faecal Nitrogen (FN) has been one of the most used proxy for diet quality in wild ungulates. The FN is very stable under environmental conditions, allowing the study of both seasonal and spatial variations of diet quality in extreme seasonal ecosystems. Moreover, FN would be easily predicted by NIRS, but to our current knowledge, no work reports the use of NIRS in the Pyrenean Chamois (Rupicapra pyrenaica). The objective of this study was to estimate NF by NIRS by means of 192 faecal samples, collected from May 2009 to September 2010 in two localities (Costabona and Fontalba, both Alpine ecosystems) in the National Hunting Reserve of Freser-Setcases, Catalan Pyrenees (Northwest Spain). NF was first estimated by DUMAS /LECO as reference method and later by NIRSystems 5000 (FOSS). Different mathematical treatments were evaluated for the development of prediction models. Subsequently individual fits were compared to the obtained for the whole sample. Although some statistical parameters were better for the local calibration, the whole fit (i.e., considering both localities at the same time) was accurate enough (R2 = 0.97, SEC= 0.076, r2 = 0.95, SEP = 0.109) for estimating FN. We can conclude that NIRS is a suitable and accurate tool for predicting FN in Pyrenean Chamois

Exploration of the equilibrium operating space for NSTX-Upgrade

This paper explores a range of high-performance equilibrium scenarios available in the NSTX-Upgrade device [J.E. Menard, submitted for publication to Nuclear Fusion]. NSTX-Upgrade is a substantial upgrade to the existing NSTX device [M. Ono, et al., Nuclear Fusion 40, 557 (2000)], with significantly higher toroidal field and solenoid capabilities, and three additional neutral beam sources with significantly larger current drive efficiency. Equilibria are computed with freeboundary TRANSP, allowing a self consistent calculation of the non-inductive current drive sources, the plasma equilibrium, and poloidal field coil current, using the realistic device geometry. The thermal profiles are taken from a variety of existing NSTX discharges, and different assumptions for the thermal confinement scalings are utilized. The no-wall and idealwall n=1 stability limits are computed with the DCON code. The central and minimum safety factors are quite sensitive to many parameters: they generally increases with large outer plasmawall gaps and higher density, but can have either trend with the confinement enhancement factor. In scenarios with strong central beam current drive, the inclusion of non-classical fast ion diffusion raises qmin, decreases the pressure peaking, and generally improves the global stability, at the expense of a reduction in the non-inductive current drive fraction; cases with less beam current drive are largely insensitive to additional fast ion diffusion. The non-inductive current level is quite sensitive to the underlying confinement and profile assumptions. For instance, for BT=1.0 T and Pinj=12.6 MW, the non-inductive current level varies from 875 kA with ITER-98y,2 thermal confinement scaling and narrow thermal profiles to 1325 kA for an ST specific scaling expression and broad profiles. This sensitivity should facilitate the determination of the correct scaling of transport with current and field to use for future fully non-inductive ST devices. Scenarios are presented which can be sustained for 8-10 seconds, or (20-30)τCR, at βN=3.8-4.5, facilitating, for instance, the study of disruption avoidance for very long pulse. Scenarios have been documented which can operate with βT~25% and equilibrated qmin>1. The value of qmin can be controlled at either fixed non-inductive fraction of 100% or fixed plasma current, by varying which beam sources are used, opening the possibility for feedback qmin control. In terms of quantities like collisionality, neutron emission, non-inductive fraction, or stored energy, these scenarios represent a significant performance extension compared to NSTX and other present spherical torii

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

23rd IAEA Fusion Energy Conference: summary of sessions EX/C and ICC

An overview is given of recent experimental results in the areas of innovative confinement concepts, operational scenarios and confinement experiments as presented at the 2010 IAEA Fusion Energy Conference. Important new findings are presented from fusion devices worldwide, with a strong focus towards the scientific and technical issues associated with ITER and W7-X devices, presently under construction