Ultra-fast charge exchange spectroscopy for turbulent ion temperature fluctuation measurements on the DIII-D tokamak (invited)

Date

2012-10-01

Author

Uzun Kaymak, İlker Ümit
McKee, G. R.

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

240
views

0
downloads

A novel two-channel, high throughput, high efficiency spectrometer system has been developed to measure impurity ion temperature and toroidal velocity fluctuations associated with long-wavelength turbulence and other plasma instabilities. The spectrometer observes the emission of the n = 8-7 hydrogenic transition of C+5 ions (lambda(air) = 529.06 nm) resulting from charge exchange reactions between deuterium heating beams and intrinsic carbon. Novel features include a large, prism-coupled high-dispersion, volume-phase-holographic transmission grating and high-quantum efficiency, high-gain, low-noise avalanche photodiode detectors that sample emission at 1 MHz. This new diagnostic offers an order-of-magnitude increase in sensitivity compared to earlier ion thermal turbulence measurements. Increased sensitivity is crucial for obtaining enough photon statistics from plasmas with much less impurity content. The irreducible noise floor set by photon statistics sets the ultimate sensitivity to plasma fluctuations. Based on themeasured photon flux levels for the entire spectral line, photon noise levels for (T) over tilde (i)/T-i and (V) over tilde (i)/V-i of similar to 1% are expected, while statistical averaging over long data records enables reduction in the detectable plasma fluctuation levels to values less than that. Broadband ion temperature fluctuations are observed to near 200 kHz in an L-mode discharge. Cross-correlation with the local beam emission spectroscopy measurements demonstrates a strong coupling of the density and temperature fields, and enables the cross-phase measurements between density and ion temperature fluctuations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733548]

Subject Keywords

Detector

URI

https://hdl.handle.net/11511/44882

Journal

REVIEW OF SCIENTIFIC INSTRUMENTS

DOI

https://doi.org/10.1063/1.4733548

Collections

Department of Physics, Article

Suggestions

OpenMETU
Core

External Search Coil as a Means of Measuring Rotor Speed of an Induction Motor Özlü Ertan, Hatice Gülçin; Keysan, Ozan (2009-07-03) The study in this paper investigates whether the air gap harmonics can be identified by using an external search coil placed on the frame of an induction motor. For this purpose the study focuses on the prediction of rotor speed of an induction motor from external search coil emf, using spectral analysis techniques. In the first stage of the study the type of search coil which maximizes the induced emf is sought, also the position of the coil on the induced emf is investigated. Several motors are tested wit...
Development of high performance uncooled infrared detector materials Kebapçı, Başak; Akın, Tayfun; Turan, Raşit; Department of Micro and Nanotechnology (2011) This thesis reports both the optimizations of the vanadium oxide (VOx) thin film as an active infrared detector material by the magnetron sputtering deposition method and its use during fabrication of proper resistors for the microbolometers. Vanadium oxide is a preferred material for microbolometers, as it provides high TCR value, low noise, and reasonable resistance, and a number of high-tech companies have used this material to obtain state-of-the-art microbolometer arrays. This material is first used in...
Transient response of an infinite elastic medium containing a spherical cavity subjected to torsion Zakout, U; Akkas, Z; Tupholme, GE (2000-06-01) An exact closed-form solution is obtained for the transient response of an infinite isotropic elastic medium containing a spherical cavity subjected to torsional surface loading using the residual variable method. The main advantage of the present approach is that it eliminates the computational problems arising in the existing methods which are primarily based on Fourier or Laplace transformation techniques. Extensive numerical results for the circumferential displacements and shear stresses at various loc...
Numerical modeling and optimization of HgCdTe infrared photodetectors for thermal imaging Koçer, Hasan; Beşikci, Cengiz; Department of Electrical and Electronics Engineering (2011) This thesis presents a detailed investigation of the performance limiting factors of long wavelength infrared (LWIR) and very long wavelength infrared (VLWIR) p on n HgCdTe detectors through numerical simulations at 77 K incorporating all considerable generation-recombination mechanisms including trap assisted tunneling (TAT), Shockley-Read-Hall (SRH), Auger and radiative processes. Numerical simulations under dark and illuminated conditions were performed with different absorber layer thicknesses, material...
Prediction of ducted diaphragm noise using a stochastic approach with adapted temporal filters Karban, Ugur; Schram, Christophe; Sovardi, Carlo; Polifke, Wolfgang (SAGE Publications, 2019-01-01) The noise production by ducted single- and double-diaphragm configurations is simulated using a stochastic noise generation and radiation numerical method. The importance of modeling correctly the anisotropy and temporal de-correlation is discussed, based on numerical results obtained by large eddy simulation. A new temporal filter is proposed, designed to provide the targeted spectral decay of energy in an Eulerian reference frame. An anisotropy correction is implemented using a non-linear model. The acous...

Citation Formats

İ. Ü. Uzun Kaymak and G. R. McKee, “Ultra-fast charge exchange spectroscopy for turbulent ion temperature fluctuation measurements on the DIII-D tokamak (invited),” REVIEW OF SCIENTIFIC INSTRUMENTS, pp. 0–0, 2012, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/44882.