1 / 18

Correlation Analysis of Electrostatic Fluctuation between Central and End Cells in GAMMA 10

Correlation Analysis of Electrostatic Fluctuation between Central and End Cells in GAMMA 10 Y. Miyata, M. Yoshikawa, F. Yaguchi, M. Ichimura, T. Murakami and T. Imai Plasma Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8577, JAPAN CONTENTS

badu
Download Presentation

Correlation Analysis of Electrostatic Fluctuation between Central and End Cells in GAMMA 10

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Correlation Analysis of Electrostatic Fluctuation between Central and End Cells in GAMMA 10 • Y. Miyata, M. Yoshikawa, F. Yaguchi, M. Ichimura, • T. Murakami and T. Imai • Plasma Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8577, JAPAN • CONTENTS • Abstract (Background and Research Purpose) • Experimental Setup in GAMMA 10 • Gold Neutral Beam Probe (GNBP) and End Plate (EP) measurement • Experimental Results (GNBP,EPs and their Correlation) • Summary

  2. Abstract [Background] The fluctuations are observed in some magnetic confinement devices. The fluctuations due to the instabilities cause the anomalous transports. In the GAMMA 10 tandem mirror, the electrostatic and magneto hydrodynamic fluctuations are observed by some measurement systems and they are related to the radial transport. The decreasing of the plasma stored energy due to the radial transport was also observed. [Research Purpose] We show the effect of radial particle transport related value induced by the fluctuations measured by a Heavy Ion Beam Probe (HIBP). We show the result of the potential fluctuation of the end plates measurement. The correlation between the potential fluctuation measured by HIBP and that of end plates was assessed.

  3. Study of Potential Formation in GAMMA 10 End Plate(EP) Heavy Ion Beam Probe(HIBP) End Plate(EP)

  4. Gold Neutral Beam Probe System at Central Cell Beam Intensity　⇒　Density Beam Energy　⇒　Potential Deflection Electric Field 45 degree Ground Plate 32ch 1ch A beam probe is a useful tool on the basis of the energy conservation of a heavy ion beam for the potential and fluctuation measurements. The beam probe system consists of two parts. One is a beam source which produces a high energy ion beam. The other is a beam detector by using an electrostatic energy analyzer. The incident beam and the ionized ion beam in plasma are called the primary and secondary beams, respectively.

  5. Plate No. ~#1 ~#2 ~#3 ~#4 Rcc(cm) 5.5 7.8 11 16 End Plate measurement at West End Cell ●End Plate Measurement The end plates (EP) made of stainless steel is settled at both end sides of GAMMA 10 for receiving the end loss plasma. The EPs consist of some divided plates made of stainless steel. The EPs are divided into five sections in radial direction and connected to ground though the 1 MW of cement resistor. The EP #1, #2, #3 and #4 cover the region of radius compared at central cell ~5.5, 5.5~7.8, 7.8~11 and 11~16 cm, respectively. The #1, #2 and #3 EPs are divided into four. The #4 EPs are divided into eight sections in circumferential direction and normally connected. X Axis Z Axis Location of EPs (Compared at central cell ) Plug/Barrier Region

  6. Experimental Result: Diamagnetism and Electron Density Radial Profile of Electron Density Time Evolution of Diamagnetism 3% Down In order to study the feature of electrostatic fluctuation, it is necessary to produce the plasma in which the electrostatic fluctuation occurs with adjusting the heating and gas puffing sequences. After starting up the plasma with the both sides of plasma gun, ICRF heating systems are used in the central cell. We focused attention on ICRF heating time at 120 - 130 and 145 - 155 ms because we assess the effect of the radial particle transport. The plasma stored energy decreased with time in spite of ICRF heating at a constant power.

  7. Experimental Result: GNBP measurement at Central Cell [1] Spectrum of Potential Fluctuation Level near Center Time Evolution of Potential Fluctuation near Center Drift-type fluctuation Radial Profile of Potential Fluctuation Level 10 ms averaged The fluctuation near 9 kHz was identified by electrostatic probe established in circumferential direction. The observed fluctuation was estimated as the drift-type fluctuation with the azimuthally mode number of 2.

  8. Experimental Result: GNBP measurement at Central Cell [2] Radial Profile of Particle Flux Related Value Radial Profile of Density Fluctuation Level 10 ms averaged two or three times more Radial Profile of Coherence between Potential and Density Fluctuations Small fluctuations give rise to the local transport. If the average value of the local transport is not zero, the net transport so-called the radial particle flux. In the case of GAMMA 10, the radial particle flux due to the electrostatic fluctuations is defined: almost 0.8

  9. Experimental Result: EP measurement at West End Cell [1] Radial Profile of Potential fluctuation Level by using #1, #2 and #3 EPs Spectrum of #1 EP potential Fluctuation Level ~#1 #2 #3 #4~ The EP potential fluctuation also had the peak near 9 kHz same as the potential fluctuation measured by GNBP. However, the drift-type fluctuation may not occur in a low plasma pressure case such as end cell plasma. The correlation between central and end cells was assessed for identifying the fluctuation measured by EPs.

  10. Experimental Result: EP measurement at West End Cell [2] Radial Profile of Coherence between Central and End Cells Coherence almost 0.95 ~#1 #2 #3 #4~ DL=12.22[m] GNBP Z=1.18[m] #1 EndPlate Z=13.4[m] We assessed the correlation between the potential fluctuations measured by GNBP and EP in same magnetic field line. The drift-type fluctuation measured at central cell correlated strongly with the fluctuation measured at end cell. This fluctuation at end cell appears identical to the drift-type fluctuation at central cell.

  11. Summary The density and potential fluctuations were observed at central cell by using GNBP. The potential fluctuation of the end plates settled at both side of GAMMA 10 was observed. The drift-type fluctuation with azimuthally mode number of 2 near 9 kHz increased, and the plasma stored energy decreased with time. The diamagnetism decreased at rate of 3 % and the radial profile of the particle flux induced by fluctuations was two or three times more. The EP potential fluctuation also had the peak near 9 kHz and increased with time. The correlation between central and end cells was assessed for identifying the fluctuation measured by EPs. The drift-type fluctuation measured at central cell correlated strongly with the fluctuation measured at end cell. The drift-type fluctuation which produces the radial particle transport was observed at central cell. And, the drift-type fluctuation propagated from the central cell to the end cell.

  12. Gold Neutral Beam Probe System at Central Cell [3] ●Principle of Potential Fluctuation Measurement The potential calculating formula that the arguments of the function are the ionization point and the peak channel of the beam intensity is obtained. The potential fluctuation is obtained from the small perturbation of the plasma potential. E Fc Potential Energy Acceleration Energy R: Radial position (cm) Pch: Flying distance of secondary beam in the analyzer Analyzer PlasmaIon Source ●Principle of Density Fluctuation Measurement A gold neutral particle is ionized due to the reactivity with electrons, and ionized particle deflected by the magnetic field. The ionization efficiency is obtained by the experimental rule of Lotz as indicated in the expression below.We obtain the density fluctuation because the detected signal is dependent on the densitynear electron temperature 100 eV. Z: Equivalent electron number U:Ionization potential N: Atomic shell number

  13. Feature of GNBP <The feature of GNBP> ・Using the neutral primary beam and the negative gold ion by Cs sputtering ・High neutralization efficiency using the negative ion ・Reduce the effect of the leakage magnetic fields using the neutral beam ・High detection efficiency using Micro Channel Plate (MCP) Triangle Wave High Voltage Amp Function Generator

  14. Novel Slit Current Slit Multipoint Measurement using Novel Analyzer II Figure shows the component of the energy analyzer and the trajectories of the secondary beam which pass the current and novel entrance slits in y-z plane. The secondary beams pass the current and novel slits within the slit width of 12 mm in y-z plane. Summary There is radial particle transport as the loss induced by the fluctuations. It is possible to measure the potential and density fluctuations at the arbitrary point simultaneously in GNBP, the phase difference can be observed. The radial particle transport induces the decreasing of the plasma stored energy. This phenomenon is estimated the theoretically-predicted loss process induced by the radial transport due to the phase difference between the potential and density fluctuations.

  15. Gold Neutral Beam Probe (GNBP) ●Spec of GNBP The energy and the incident angle of the primary beam passing the plasma center are about 12 keV and 40 degrees, respectively. Typical primary beam current is obtained 2 mA using the Faraday Cup. The GNBP system has two incident angle electrostatic deflectors of the vertical and the horizontal directions. A parallel plate type electrostatic energy analyzer with the incident angle of 45 degrees is installed on the x-y plane. In the analyzer, the micro-channel plate (MCP) detector of 32 anodes which is mounted along y direction is utilized for the beam detector. The width of an each anode is 2.4 mm. The current entrance slit is established on the ground plate in the energy analyzer. The current entrance slit size is 12 x 0.5 mm. ●Fluctuation Measurements The detected positive secondary beam is derived from the neutral primary beam ionized at the ionization point. The electron-impact ionization process is dominant in a case of the ionization of the primary beam. The secondary beam current depends on the electron distribution function at the ionization point. The density fluctuation is obtained from the perturbation of the detected beam intensity, and the potential fluctuation is obtained from the perturbation of the plasma potential.

  16. Radial Particle Flux induced by Potential and Density Fluctuations If the average value of drifts induced by azimuthally propagation density and electric field fluctuations is not zero, the radial particle flux Grexists. If the density, potential and azimuthal electric field fluctuations components are expressed as The radial flux can be written as where anf=an-afis the phase difference, g is the coherence between and . Then we can estimate the radial particle flux using this expression. The phase difference decides the direction of the flux and the growth of the fluctuation.

  17. Plate No. ~#1 ~#2 ~#3 ~#4 Rcc(cm) 5.5 7.8 11 16 End Plate measurement at West End Cell [2] Location of EPs (Compared at central cell ) The EP #1, #2, #3 and #4 cover the region of radius compared at central cell ~5.5, 5.5~7.8, 7.8~11 and 11~16 cm, respectively. The #1, #2 and #3 EPs are divided into four. The #4 EPs are divided into eight sections in circumferential direction and normally connected.

  18. E E Fc Virtual Potential Potential Energy Acceleration Energy Acceleration Energy AnalyzerPlasmaIon Source AnalyzerPlasmaIon Source Gold Neutral Beam Probe System at Central Cell [2] ●Calibration of the flying distance due to the virtual potential in the energy analyzer Deflection Electric Field Virtual 400(V) Virtual 0(V) High Energy Low Energy 32ch 1ch

More Related