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

Entwicklung eines Systems zur multimedial-unterstuetzten Qualifizierung betrieblicher Mitarbeiter mit integrierter Erfolgskontrolle und Teamarbeitsformen - Umsetzung am Beispiel des Lehrgangs 'Fachkraft fuer Roboterprogrammierung' (LERNROB) Abschlussbericht

SIGLEAvailable from TIB Hannover: F03B474+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Design of the JET Upgraded Gamma-Ray Cameras

ABSTRACT The main aim of the JET KN3 gamma-ray cameras upgrade is the design of appropriate neutron/ gamma-ray filters ("neutron attenuators"). Using the attenuation factor as the main design parameter a set of three neutron attenuators of different shape and attenuation length have been designed for the horizontal and vertical cameras. Pure light water was chosen as the attenuating material for the JET gamma-ray cameras. The operation of the KN3 neutron attenuators is controlled by an electropneumatic system. A full-scale prototype of the vertical camera neutron attenuator was constructed and tested. The mechanical behaviour of the attenuator structure subject to the forces and torques produced by the JET disruptions was analysed by means of the finite element analysis method. The radiation performance of the KN3 neutron attenuators as well as the response of the gamma-ray detectors have been addressed by means of neutron and gamma-ray transport calculations. INTRODUCTION The control of the confinement of fast particles (in particular, the fusion reaction produced alpha particles) in the tokamak plasma is essential for the development of tokamak fusion reactors. One class of diagnostic techniques for the study of the fast particles in tokamak plasmas is based on the detection and analysis of the gamma radiation emitted as the result of the nuclear interactions of fast particles with plasma impurities such as carbon and beryllium In the JET tokamak the plasma gamma-ray emission is the result of the interaction of fast ions (fusion reaction products, including alpha particles, NBI ions, ICRH-accelerated ions) with the plasma impurities mentioned above. The JET gamma-ray plasma diagnostics has already provided valuable information on the characteristics of the fast ion population in plasma

Spectral Broadening of Characteristic gamma-Ray Emission Peaks from C-12(He-3, p gamma)N-14 Reactions in Fusion Plasmas

The spectral broadening of characteristic gamma-ray emission peaks from the reaction C-12(He-3, p gamma)N-14 was measured in D(He-3) plasmas of the JET tokamak with ion cyclotron resonance heating tuned to the fundamental harmonic of He-3. Intensities and detailed spectral shapes of gamma-ray emission peaks were successfully reproduced using a physics model combining the kinetics of the reacting ions with a detailed description of the nuclear reaction differential cross sections for populating the L1-L8 N-14 excitation levels yielding the observed gamma-ray emission. The results provide a paradigm, which leverages knowledge from areas of physics outside traditional plasma physics, for the development of nuclear radiation based methods for understanding and controlling fusion burning plasmas

Impact of nitrogen seeding on confinement and power load control of a high-triangularity JET ELMy H-mode plasma with a metal wall

This paper reports the impact on confinement and power load of the high-shape 2.5MA ELMy H-mode scenario at JET of a change from an all carbon plasma facing components to an all metal wall. In preparation to this change, systematic studies of power load reduction and impact on confinement as a result of fuelling in combination with nitrogen seeding were carried out in JET-C and are compared to their counterpart in JET with a metallic wall. An unexpected and significant change is reported on the decrease of the pedestal confinement but is partially recovered with the injection of nitrogen.Comment: 30 pages, 16 figure