Aerospace and Energetics Research Program University of Washington Seattle, WA 44th Annual Meeting of the Division of Plasma Physics of the American Physical Society November 11 - November 15, 2002 Orlando, FL
Ion Doppler Measurements in the HIT-II Spherical Torus P. Gu, T. R. Jarboe, B. A. Nelson A. J. Redd, R. J. Smith University of Washington M. Nagata, T. Uyama Himeji Institute of Technology
Abstract (Revised) Plasmas using coaxial helicity injection (CHI) current drive and ohmic ramping with peak current 248 ka were successfully produced on HIT-II. This demonstrates that a plasma can be produced using CHI and successfully transferred to another current drive method. A study of the ion toroidal velocity and temperature for various ion species (OV, NIV) using Ion Doppler Spectroscopy (IDS) has been investigated. IDS data from repeatable discharges, taken using chords with various impact parameters will be presented.
Doppler Broadening Measurement Doppler shift caused by thermal particle motion: λ = λυ/c whereλ : wavelength of the line [Å], υ : particle velocity [m/s], c : speed of light [m s -1 ] A Maxwellian velocity distribution gives rise to a Gaussian line profile: I( λ) = I0 exp[ Mc ( λ) /2κTiλ where M : mass of the emitting atom [kg], κ : Boltzmann's Constant [ev k -1 ] 2 2 2 ] λ The Full Width at Half Maximum (FWHM) D λ D 5 = 7.70 10 λ( κti / µ ) 1/ 2 where µ : atomic weight [g/mol -1 ] Ti : ion temperature :
CHI Discharges Show Larger Rotation Velocity Than CHI-Ohmic Mixed Discharges OV Line, Chord #9: SN 19213 (UPPER) Ip (A) n e_avg (m -3 ) IDS #7 IDS #10 IDS #8 IDS #11 IDS #9 IDS #12 Time (ms)
(cont.) OV Line, Chord #9: SN 19212 (LOWER) Ip (A) n e_avg (m -3 ) IDS #7 IDS #10 IDS #8 IDS #11 IDS #9 IDS #12 Time (ms)
Highest Toroidal Velocity at the Edge in CHI Discharges (OV Line) Chord #9: SN 19213 (upper) Chord #6: SN 19215 (upper) Chord #3: SN 19208 (upper) Chord #2: SN 19204 (upper)
CHI Flow Data Show OV Rotation Linear with R impact (ω=64000s -1 ) Chord #9: Impact Radius 41.4 cm----sn 19213, SN 19212 D Chord #6: Impact Radius 32.1 cm----sn 19215 Chord #3: Impact Radius 21.4 cm----sn 19208, SN 19210 Chord #2: Impact Radius 17.6 cm----sn 19204, SN 19202 Averaged over 3 ms < t < 6 ms. Note: To determine if thin shell or rigid rotor rotation, an intensity inversion is necessary.
Central Line Determined Using the Radial Port (Ip=248 ka) OV Line: SN 24552 Ip (A) IDS #9 IDS #6 IDS #10 IDS #7 IDS #11 IDS #8 IDS #12 Time (ms)
Raw Data Show Rotation Changes Direction after the Peak Current OV Line, Chord #1: SN 24552 Ip (A) IDS #9 IDS #6 IDS #10 IDS #7 IDS #11 IDS #8 IDS #12 Time (ms)
OV Line Burned through during High Current (248 ka) Ohmic Discharges (Velocities chords 10-6) Chord #10: SN 24554 Chord #9: SN 24555 Chord #8: SN 24558 Chord #7: SN 24553 Chord #6: SN 24557
OV Rotation Velocity Changes Direction Before and After the Peak Current during Ohmic Discharges(chords 4-1) Chord #4: SN 24560 Chord #3: SN 24561 Chord #2: SN 24562 Chord #1: SN 24563
NIV Rotation Velocity Does Not Show Rigid Rotor during Ohmic Discharges (chords 10-7) Chord #10: SN 24459 Chord #9: SN 24460 Chord #8: SN 24461 Chord #7: SN 24462
(cont.) (chords 6-3) Chord #6: SN 24463 Chord #4: SN 24464 Chord #3: SN 24465
OV Line Burned through during Ohmic Discharges in High Plasma Current (248 ka) (Temperatures chords 9-6) Chord #9: SN 24555 Chord #8: SN 24558 Chord #7: SN 24553 Chord #6: SN 24557 Instrument Temperature
Highest OV Temperature Seen at the Peak Current (248 ka) Chord #2: SN 24562 Chord #1: SN 24563 Instrument Temperature
NIV Temperature Is also Highest at the Peak Plasma Current (130 ka) (chords 7-3) Chord #7: SN 24462 Chord #6: SN 24463 Chord #4: SN 24464 Chord #3: SN 24465 Instrument Temperature
Both OV and NIV Have the Same Temperature OV, Radial Port: SN 24526 NIV, Radial Port: SN 24519 Instrument Temperature Instrument Temperature
Summary OV line was burned through during ohmic discharges in high current plasmas (Ip=248 ka). OV rotation velocity changes direction before and after the peak current during ohmic discharges. OV flow data show rigid rotor rotation with ω=64000s -1 in pure CHI discharges while NIV flow data do not show rigid rotor in ohmic discharges. OV temperatures are ~ 80 ev near the edge for high plasma currents (248 ka), and NIV central temperatures can be as high as ~ 100 ev with different plasma conditions (130 ka). Both OV and NIV temperature profiles show the same temperature (~ 40 ev) from the same radial port, for the same plasma conditions.