K." Ogura

M. Ichimura

R. Minami

T. "Saito

T. Imai

T. Kariya

Y. Kiwamoto

Y. Soga

Y. Tatematsu

National Institute for Fusion Science (NIFS-Repository)

   Thomson scattering (TS) is the most reliable diagnostic to measure the electron temperature.1-4)  In GAMMA 10, the electron temperature is measured by a soft X-ray measurement.  In these days, direct electron heating by electron cyclotron heating (ECH) experiments in the central cell have been carried out.  Then we planned to install the neodymium-doped yttrium aluminium garnet laser (Nd:YAG) TS in order to measure electron temperature directly in the central cell of GAMMA 10.  GAMMA 10 is the largest tandem mirror machine with plasma confinement achieved by not only a magnetic mirror configuration but also high potentials at both end regions.  The main plasma is produced and heated by ion cyclotron range of frequency waves.  The confinement potentials are produced by the plug- and barrier-ECH (P/B-ECH) at the plug/barrier region.  The typical electron density, electron and ion temperatures are about 2  1012 cm-3, 0.1 keV and 5 keV, respectively, during confinement potential formation.  The newly installed TS was the same concept system as those installed in CHS and LHD in NIFS.  We used the high power YAG laser (1064 nm, 2 J/pulse), a focusing lens (f = 2 m, φ50 mm), collection mirror (φ600 mm, R = 1200 mm), bundled optical fiber (input 2 × 7 mm, output φ4.6 mm, length of 6.67 m) and the NIFS 5 channel polychromator with avalanche photodiode.  We used the 90 degree TS.  This system will be able to measure the electron temperature range from 0.02 to 10 keV with 0.01 keV resolution, and its measureable radial range is about ±200 mm with space resolution of about Δd ~ 20 mm.  The sampling rate of the system is 10 Hz.  We show the schematic view of the GAMMA 10 TS in Fig. 1.  In this fund year, we measured the electron temperature by using this newly installed TS for the first time in the tandem mirror GAMMA 10.  The Raman and Rayleigh calibration experiments were carried out for setting of optical system and stray light in the evaluation of GAMMA 10 YAG-TS.  The nitrogen gas was used, and the pressure in GAMMA 10 device was raised up to 200 Torr.  In Fig. 2, signal intensities of Raman scattering measurement as a function of target pressure is shown.  The measured scattering signal is proportional to the gas pressure.  The linear component indicates the scattering light and the offset indicates the stray light.  The stray light in this system is very small.  We applied the YAG-TS to measure the electron temperature of GAMMA 10 plasma.  The signal to noise ratio is about 3.  We can obtain the electron temperature of about 0.04 keV before applying P/B-ECH.  With application of P/B-ECH, the electron temperature increased to about 0.08 keV.  The error of the electron temperature measurement by the system is about 13 % by considering minimize chi-squared value analysis.  In summary, YAG-TS was installed to the tandem mirror GAMMA 10.  This system can be operated to measure electron temperature in the very low plasma density region less than 2×1018 m-3.  We can successfully measure the electron temperature in the tandem mirror GAMMA 10 by using YAG-TS for the first time.  The electron temperature is obtained at one position and one period.   1) Narihara, K. et al.: Fusion Eng. Design 34-35, 67 (1997). 2) Narihara, K. et al.: Rev.Sci. Instrum. 72, 1122 (2001). 3) Kainaga, S. et al.: Plasma Fusion Res. 3, 027 (2008). 4) Lee, H. G. et al.: Rev. Sci. Instrum. 72, 1118 (2001).   Fig. 1.  The YAG-TS in GAMMA 10. 0204060801000 50 100 150 200Intensity [ Rel.units ]Nitrogen Pressure [ Torr ]  Fig.  Signal intensities of Raman scattering measurement as a function of target pressure. 2.   It is now well recognized that spatial transport and  energy  transfer  in  plasmas  are  strongly connected  to  global  structures  of  plasma parameters. This is essentially true for fusion, non-neutral  and  gyrotron  plasmas  magnetized  and confined  in  conductor  walls. With  wide  and integrated scope of various plasmas, we take a first step of linear analysis of global structure of drift waves. Many  works  have  been  reported  for decades on drift waves, and formations of global structures in nonlinear stages have been examined numerically. However, only a few works have been reported in connection to linear analyses of global structures. [1,2,3] Actually most of extensive linear analyses have been limited to slab models or fluid dynamics in cylindrical configurations.  In  this  paper  we  construct  a  Vlasov–based equation  with  the  guiding-centre  approximation including arbitrary radial distributions of density and  anisotropic  temperature  for  multi-species. Various  distributions  can  be  described  by  the superposition  of  multiple  Maxwellians. The potential perturbation  !! r( ) " ! r,!, kz ,#( )  with zimuthal and axial modes  !,kz( )  satisfies  d2!! r( )dr2+1r" kDs2 vszkz#cs##cshs! r( )s$%&''()**d!! r( )dr+" !2r2 +!rkDs2 vszkz#cshs! r( ) " kz2 +12kDs2 +Z ,s!( )s$s$%&''()**!! r( ) = 0 where    !s! = " # !"E( ) 2kzvsz , vsz = Tsz ms , and hs! r( ) !12d lnns0 r( )drZ "s!( ) #12d lnTsz r( )dr"s! $Z "s!( ) + Z "s!( )%& '()*+,-.Though  transverse-temperature-driven  drift  is taken  into  account, only  !E r( ) = "Er0 r( ) rB  remains in  !s!  after velocity integration. In the limit of slab geometry,  this equation agrees with already established dispersion relations including density  and  axial-temperature  gradients.　Eigen modes  of  the  D.E. satisfying  the  boundary condition   !! 0( ) = !! w( ) = 0  are  examined  by employing shooting method under various radial profiles of plasma parameters typically observed in the central cell of GAMMA10 such as:0.00 0.05 0.10 0.1550100150200r m[ ]Te eV[ ]Tiz eV[ ]0.05 0.10 0.155.010171.010181.510182.010182.510183.01018r m[ ]Density [ !1018m-3]1230.05 0.10 0.1530 00020 00010 000r m[ ]!E"B "104rad s#$ %&!e" #104rad s$% &'!1!2! 3High transverse temperature does not contribute in this  guiding-center  approximation. Numerical analyses  have  revealed  that  unstable   eigen function  !! r( )  that satisfies the above D.E.  is non-zero only in a radially limited region, and that the growth rate increases  with radial wave number reflecting  destabilizing  contribution  of  90  deg. shifted polarization drift.    Examples for the mode of   !, kz( ) = !1, 0.25m!1( )  are plotted below. 0.01 0.02 0.03 0.04 0.05 0.06 0.071.5102451.0102455.0102445.0102440.01 0.02 0.03 0.04 0.05 0.06 0.07110245510244r m[ ]r m[ ]0 0.050 0.05 !! r( ) !! r( )0.059! = 16000 +100 i rad s[ ]! = 16000 "100 i rad s[ ]0.01 0.02 0.03 0.04 0.05 0.06 0.074102172102172102174102170.01 0.02 0.03 0.04 0.05 0.06 0.072.5102262.0102261.5102261.0102265.0102255.010225r m[ ]r m[ ]0 0.03 0.060 0.03 0.06 !! r( ) !! r( )0.046! = 18000 +1000 i rad s[ ]! = 18000 +100 i rad s[ ]So far global-scale monochromatic eigen functions have not been obtained as derived in collision-dominated  fluid  models  or  as  observed   in GAMMA10.  Contribution of finite Larmor-radius will be taken into account in the next step. This may also be useful  for generalized analysis  of gyrotron power generation placed in our scope.References[1] R.F.Ellis et al. Plasma Physics 22, 113 (1980).[2] C. Schroder et al. Phys. Plasmas 11, 4249 (2004).[3] V. Naulin et al. Phys. Plasmas 15, 012307 (2008).489§11. Study of Interaction between Plasma and EM Wave in Prospect of Application of Millimeter & Sub-millimeter Waves  – Linear Analysis of Global Structure of Drift Wave –Saito, T., Tatematsu, Y., Kiwamoto, Y. (Univ. Fukui, FIR FU), Ichimura, M., Imai, T., Kariya, T.,  Minami, R. (Univ. Tsukuba, PRC), Soga, Y. (Kanazawa Univ.), Ogura, K. (Niigata Univ.)

Study of Interaction between Plasma and EM Wave in Prospect of Application of Millimeter & Sub-millimeter Waves ? Linear Analysis of Global Structure of Drift Wave ?

https://nifs-repository.repo.nii.ac.jp/?action=repository_action_common_download&item_id=3219&item_no=1&attribute_id=25&file_no=1

Study of Interaction between Plasma and EM Wave in Prospect of Application of Millimeter & Sub-millimeter Waves ? Linear Analysis of Global Structure of Drift Wave ?

Abstract

Similar works

Full text

Available Versions

National Institute for Fusion Science (NIFS-Repository)