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Plasma physics and nuclear fusion.

01 Jan 1971-
About: The article was published on 1971-01-01 and is currently open access. It has received 6 citations till now. The article focuses on the topics: Nuclear fusion & Plasma diagnostics.
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Dissertation
01 Sep 2008
TL;DR: Minervini et al. as discussed by the authors measured spontaneous Brillouin scattering in an optical fiber to measure the temperature and strain of a superconducting magnet in real-time with a spatial resolution on the order of several meters.
Abstract: Large superconducting magnets used in fusion reactors, as well as other applications, need a diagnostic that can non-invasively measure the temperature and strain throughout the magnet in real-time. A new fiber optic sensor has been developed for these long-length superconducting magnets that simultaneously measures the temperature and strain based on spontaneous Brillouin scattering in an optical fiber. Using an extremely narrow (200 Hz) linewidth Brillouin laser with very low noise as a frequency shifted local oscillator, the frequency shift of spontaneous Brillouin scattered light was measured using heterodyne detection. A pulsed laser was used to probe the fiber using Optical Time Domain Reflectometry (OTDR) to define the spatial resolution. The spontaneous Brillouin frequency shift and linewidth as a function of temperature agree well with previous literature of stimulated Brillouin data from room temperature down to 4 K. Analyzing the frequency spectrum of the scattered light after an FFT gives the Brillouin frequency shift, linewidth, and intensity. For the first time, these parameters as a function of strain have been calibrated down to 4 K. Measuring these three parameters allow for simultaneously determining the temperature and strain in real-time throughout a fiber with a spatial resolution on the order of several meters. The accuracy of the temperature and strain measurements vary over temperature-strain space, but an accuracy of better than ± 2 K and ± 100 με are possible throughout most of the calibrated temperature-strain space (4-298 K and 0-3500 με). In the area of interest for low-temperature superconducting magnets (4-25 K), the temperature accuracy is better than ± 1 degree. This temperature accuracy, along with the sub-second measurement time, allows this system to be used not only as a quench detection system, but also as a quench propagation diagnostic. The sensing fiber can also simultaneously provide the first ever spatially resolved strain measurement in an operating magnet. Thesis Supervisor: Joseph V. Minervini Title: Division Head and Senior Research Engineer

16 citations

Proceedings ArticleDOI
02 Oct 2007
TL;DR: In this paper, the rotation profiles were measured by charge exchange recombination spectroscopy, using short diagnostic Neutral Beam Injection (NBI) pulses, and the temporal evolution of the central rotation could in some cases be deduced from MHD activity.
Abstract: Experiments have been carried out on JET aimed at studying rotation in RF heated plasmas with low external momentum input Both plasmas with Ion Cyclotron Resonance Frequency (ICRF) heating and Lower Hybrid Current Drive (LHCD) have been investigated The rotation profiles are measured by Charge Exchange recombination spectroscopy, using short diagnostic Neutral Beam Injection (NBI) pulses Moreover, the temporal evolution of the central rotation could in some cases be deduced from MHD activity While most of the measurements were focussed on ICRF heating, the profiles measured in plasmas with LHCD are interesting since they are the first reported from JET in such plasmas In particular, they allowed for studies of rotation in RF heated plasmas with q>1 The experimental results are presented together with an analysis of the torque from ICRF heated fast ions

8 citations

Journal ArticleDOI
TL;DR: In this paper, a dispersion relation is derived from a model in which there is a difference of rotation velocity between ions and electrons, and the electron-ion collision in the electron motion parallel to the magnetic field is included.
Abstract: Fluctuations and anomalous particle loss of a xenon afterglow plasma, which appear immediately after the decay of convective cells in an l = 3 stellarator, are investigated experimentally. This instability is caused by a static electric field directed into plasma. The fluctuation propagates in the direction of the 0×0 rotation, which is parallel to the electron diamagnetic current, and is expressed as exp[i(mθ + n − ωt)], m = 2 and n = − l , where θ is measured in the poloidal and o in the toroidal direction.A dispersion relation is derived from a model in which there is a difference of rotation velocity between ions and electrons, and the electron-ion collision in the electron motion parallel to the magnetic field is included. The difference in rotation velocities comes from the effect of finite ion Larmor radius and the centrifugal force. The dispersion relation derived here also includes the resistive drift instability. The growth rate takes maximum values on the rational magnetic surfaces. Predictions on the basis of the dispersion relations are in good agreement with observed wave propagation, frequency, growth rate, and plasma loss.

1 citations

Journal ArticleDOI
01 Dec 2017

1 citations

Dissertation
01 Jan 2007
TL;DR: Hagelstein et al. as mentioned in this paper reported that the Yang-Koldamasov device produces excess heat by iESi by pumping oil through a thin nozzle; however, the theoretical mechanism for this effect is at the present unknown.
Abstract: Due to the finite supply of oil, energy availability and price are issues facing the world. Among the possible approaches to this problem is research of new physical effects which may produce energy in novel ways. The Yang-Koldamasov device was reported to produce excess heat by iESi by pumping oil through a thin nozzle; however, the theoretical mechanism for this effect is at the present unknown. The subject of this thesis is an attempt at independent confirmation of the effect at MIT and FRC. To perform calorimetry on this device, there are several issues involved, such as thermocouple offset errors, RF noise, and erroneous readings due to fluid flow conditions. Methods for handling these issues are discussed in application to two independent measurements of energy gain in the system, differential calorimetry over the cell, and flow calorimetry via a heat exchanger. The differential calorimetry has been improved compared to what was earlier available on Yang-Koldamasov devices, and the flow calorimetry is new to the device. Data was collected on several tests After analysis, the data was found consistent with a null result. However, over the course of the runs the behavior of the device was very different than the behavior at earlier demonstrations where excess heat was observed. For example, earlier demonstrations exibited electrical arcing perpendicular to the flow of oil, while the current device shows only arcing in the direction of oil flow. Future work is being conducted by FRC to identify the reasons that the current apparatus behaves differently. Thesis Supervisor: Peter Hagelstein Title: Associate Professor