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

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

Reduction of the Attenuation Constant of Microstrip

Modifications to a normal microstrip transmission line are proposed, with the aim of reducing the attenuation constant of the line. The results of a computer analysis of a structure containing multilayers of dielectric show that significant reductions in attenuation appear possible. Copyrigh

The calculation of the characteristic impedance of microstrip

Results from calculations of Zc of microstrip from a formula proposed by Kumar etal.are discussed and compared with other theoretical and practical results

Four point probe Hall effect and resistivity measurements upon semiconductors

A solution is presented for the problem of calculating correction factors for four point probe Hall effect and resistivity measurements on rectangular semiconductor specimens based on the Corbino current image technique. In addition, a flexible numerical approach is used to verify the results obtained. This numerical approach allows four point probe measurements to be made upon specimens of both regular and arbitrary geometries

The Terminal Voltage of a Receiving Dipole Antenna

The terminal voltage of a receiving dipole antenna is dependent on the antenna current distribution which in turn is dependent on its feed-point load impedance. Computed results of the terminal voltage are presented for dipole antenna half-lengths up to 1.0λ. Copyrigh

The evaluation of geometrical effects in four point probe measurements

An accurate numerical approach is presented for the evaluation of geometrical effects in four point probe resistivity measurements upon semiconductors. The accuracy of the approach is illustrated by comparing results obtained with correction factors tabulated for probe measurements upon circular and rectangular geometries. Correction factors are presented for measurements with a square probe array upon rectangular specimens. The effect of increasing thickness for specimens of bounded geometry is also investigated. The method allows four point probe measurements to be made not only with an arbitrary probe configuration but also upon thin specimens of an arbitrary geometry