APS_2019_poster_KZ_5th

Time resolution
Spatial resolution
Te
N e
Center system: Alignment camera Brewster window Beam dump
• For 1.06um light at 25°C, dH
• Vulnerable to stray light contamination for some spatial channels
Rotational Raman Scattering: Uses wavelength shifted Raman lines to avoid stray light contamination.
2 + Z [ ]⃗ = ^_`,`<28 + ^<: − ^cde SX
S0/,ef/g92h
SX + i ]⃗ [ G! = j_`,`<28 + j<: − jcde
Electron Temperature and Density Profiles in the New High-Performance Regime of C-2W Plasmas
C-2W Thomson scattering experiments
K. Zhai, E. Parke, J. Sweeney, M. Beall, J. Kinley, M. Kaur, and the TAE Team
TAE Technologies, Inc., 19631 Pauling, Foothill Ranch, CA 92610
C-2W Thomson scattering system absolute calibration (continued)
Studies of electrons heating effects by switching off neutral beams or electrodes bias
Experimental setup
• Energy continuation
• Integrated over plasma volume
• Assuming ellipsoid shape with shaping factor 1qP,
total electron thermal energy is calculated as
• Immediate effects of switching off neutral beams or electrode bias to the electron thermal energy can be obtained through the difference of Ee,thermal change rate between just before terminating neutral beams (or electrode bias) and immediately after
Central system at mid-plane
Up to 20kHz
16 radial locations from r = -10 to r = 64cm
Jet system in open field line region 100Hz
5 radial locations from r = -10cm to r = 10cm
Rayleigh Scattering: An elastic process from the electric polarizability of the particles.
3
S( ./V/)
Center system Scattering region
Jet system: Alignment camera Beam dump
Rayleigh Scattering
Raman Scattering
In-house polychromator spectral calibration
a. DC channel spectral calibration
b. AC/DC channel ratio calibration
C-2W Thomson scattering system absolute calibration
C-2W high performance plasmas
Plasma is sustained steady state for 30 ms, limitation is due to hardware.
Shot 114534: 8 15kV-NBs from 0 to 30ms, electrode bias from 0 to 30ms
Shot 114534
Electron temperature at ~400eV achieved in the long sustained shot.
Shot 116474: 5 15kV-NBs and 3 15kV-to-23kV-NBs from 0 to 30ms,
electrode bias from 0 to 30ms with bias voltage increase at 15ms
Electrodes bias increased from 1.8kV to 2.4kV at 15ms.
TS signal STS
%&
!"# = '( ∗+∗∆Ω∗./∗0*F
Rayleigh/Raman scattering signal SRay (SRaman)
%&456
!123 = %) ∗+∗∆Ω∗.728∗0*F
Plasma/Gas
%)
SABCDEF
Fibers
./ = !"# ∗ GΩ GH"#
in which (:O5P #456
:O5P ) is Rayleigh/ Raman calibration coefficient #45=5>
GH123
GΩ
.
∗ 728
!1292: = ∑<
or
%&?
45=5> ∗ + ∗ ∆Ω ∗ .728∗ 0*F
•
•
•
30 ms steady state C-2W plasma sustainment has been achieved. 400 eV record electron temperature has been demonstrated.
Termination experiment results indicate that fast ions are well confined after the neutral beams being turned off and the electrodes bias contributes significant electrons heating.
Thomson scattering system absolute calibration has been improved using Raman scattering of nitrogen gas to avoid the stray light contamination.
!123
When scattering view is perpendicular to laser polarization, dHTS/dQ = 7.95×10-30m2/sr
SAB
%)
Lens
10-2000 eV
from ~5×1012 to ~5×1014cm-3
~P 1
0/,ef/g92h = 6x ∗ +8 z t./ | V/(|)|}G|
Jet system: Beampath
24 Raman lines considered GH→C}
64xÇ 3Ñ(Ñ − 1)
R}
lmn,opnq=5r le
Center system: Brewster window 3m focusing lens
Jet system: Alignment camera Brewster window 2m focusing lens
Electron pressure profile evolution
Electron thermal energy change rate
c. Polychromator AC channel response and relative signal level in each spectral channel at different Te
Experiment results
Center system: Beam path
J®J-2
In which rotational constant B0=1.989cm-1, polarizability anisotropy R=0.66×10-30 Cm2V-1
Polychromator Detection System
Laser Beam
•
•
Scan argon gas pressure from 0 torr (high vacuum) to 5 torr, in steps of 0.5 torr
Stray light contamination on channels at r = 56cm and
r = 64c.m .For Jet system all channels are contaminated.
•
•
Nitrogen gas, from 0 torr to 100 torr, in steps of 10 torr No stray light contamination
150 120 90 60 30 0
150 120 90 60 30 0
150 120 90 60 30 0
Shot 116066
All eight beams terminated at 10ms. P = 34.1 kW
Shot 116065
Four beams terminated at 10ms. P = 20.6 kW
Shot 116073
Electrode bias terminated at 5ms. P = 188.6kW
•
•
Anti-Stokes rotational transition J®J-2, where J is rotation state
yg8
lmn,opnq=5r le
{
k - esetu
Dw
= (4J - 2)B
0 GΩ
= Ç
j_`,`<28 =
k esetv
/dQ = 3.55×10-33cm2/sr Ray
45 2(2Ñ+1)(2Ñ−1)Ü 
250 2.5 200 2.0
150
100 1.0
50 0.5 0 0.0
• Power balance of C-2W experiments indicates the electrons heating from neutral beams is at ~300-600kW. The heating power change of 34KW at the time of switching off neutral beams implies that the fast ions are well confined after the beams being switched off, which is consistent with the experimental result of fast ions ~4ms slowdown time and ~1.6ms charge exchange time.
• Electrode bias contributes significantly to electrons heating.
Summary
1.5
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