ECEI, MIR, RF Spectrometer in KSTARfusion.postech.ac.kr/itpa26/PPT/May19/Morning/105.pdf ·...
Transcript of ECEI, MIR, RF Spectrometer in KSTARfusion.postech.ac.kr/itpa26/PPT/May19/Morning/105.pdf ·...
ECEI, MIR, RF Spectrometer in KSTAR – Advanced mm-wave and RF diagnostics
Gunsu S. Yun*, W. Lee, J. Lee, M.J. Choi, J. Lee, M. Kim, J. Leem, Y.B. Nam, G.H. Choe (POSTECH)Hyeon K. Park (UNIST)
H. Park, D.S. Kim, K.W. Kim (KNU)C.W. Domier, N.C. Luhmann, Jr. (UC Davis), N. Ito, A. Mase (Kyushu Univ.)S.G. Lee, S.W. Yoon, Y.S. Bae , KSTAR Team (NFRI)
Collaborators:
ITPA Diagnostics TG meetingMay 19 - 22, 2014, POSTECH, Pohang, Korea
* Work supported by NRF Korea
(2) MIRFast imaging system for nefluctuations
(1) Two ECEI systemsFast & high-resolution imaging system
for Te fluctuations
(3) Fast RF Spectrometerfor plasma waves (ion cyclotron,
Alfven, whistler, etc)
Outline
2
ECEI-1(year 2010)Dual arrays
I. KSTAR 2D ECE Imaging (ECEI)
• Space resolution ~ 1x1—2x3 cm2
• Te resolution (real-time), 𝛿𝛿𝑇𝑇𝑒𝑒/ 𝑇𝑇𝑒𝑒 ≈ 2%• Time resolution ~ 2 µs
~6 m
Lens
Detector
Simultaneous Imaging of Core and Edge Study of interaction
btw instabilities* Internal Kink
(CORE)
ELM(Edge)
3
Appendix0. Array of heterodyne detectorsSeparate Compartments for amplifiers and diode arrays for better noise shielding‡
(Side view)
Schottky diode on a patch antenna†
Isoview
Top view
†P. Zhang, RSI 2008 ‡ Yun, LAPD (2013) 4
Heterodyne Detector Arrays
Triplet for vertical zoom
1. Lens System for Imaging • Lens material: HDPE• Lens configuration: Cooke
triplet or doublet for flexible zooming (vertical zoom factor ~ 1—3)
Focus lenses
LFS
HFS
Focus Lenses
~4m
Cooke Tripletfor Vertical Zoom
(top view)
Measured beam profile at the image plane
Image Position (mm)
Source Position (mm)
Zoom factor measurement
5
2. Wide-Band Beamsplitter
Beamsplitter
• Thin Tempered Glass(borofloat33, t=1.1mm, Dk = 4.6)
170 GHz notch filter
Detector ARRAY box
3. Notch-filter
• Array of copper squares- Copper Thickness : 9 um- Pattern dimension = 476~512 um
• Dielectric Thickness : 254 um• Dielectric Constant : 2.20• Dissipation Factor : 0.0007
Deep and symmetric notching
6
4. High-pass filters for single-sided mixing
Tran
smitt
ance
(dB)
Input frequency (GHz)
Full transmission ~ 17 GHz wide
– measured – calculation
Dichroic high-pass filters
ARRAY BOX
5. Half-wave plate for O1 mode operation at high B
X2 freq, too high
O1 freq
X2 cutoff
O1 cutoff
Bt = 3 TGrooved HDPE plate ~ meta-
material
-50 0 50
50
100
150
200
250
300
350
400
Beam
Pow
er[m
V]
without half wave platewith half wave plate
Rotation Angle (deg)
7
𝛿𝛿𝑇𝑇𝑒𝑒/�𝑇𝑇𝑒𝑒
Dual flux tubes (DFTs) †(#6022)
𝑞𝑞 ≈ 1
Crescent tube (#4004)
Triple flux tubes(#5422)
* Choe, KSTAR Conf. (2013)Yun, PRL 109 (2012)Bierwage, to be submitted
Sawtooth structures modified by ECRH*
8
Tearing modes*
m/n=2/1 mode
*M. Choi, NF (2014), accepted.
m/n=3/2 mode
𝛿𝛿𝑇𝑇e𝑇𝑇e
𝛿𝛿𝑇𝑇e𝑇𝑇e
Shot 6304t = 4.322s
Shot 6123t = 6.788s
9
Alteration of ELM structure by n=1 magnetic perturbations (MP)*
* Yun, PoP (2012)Jeon, PRL (2012)J. Lee, KSTAR Conf. 2013
𝛿𝛿𝑇𝑇ECE𝑇𝑇ECE
0.10.05
0-0.05
(shot#6123)
15
10
5
0
-5
-10
-15
205 210 215 220 225 230
No MP
~𝟏𝟏𝒌𝒌𝒌𝒌
/𝒔𝒔
z(c𝑚𝑚
)
R(c𝑚𝑚)
n~10
Non-resonant MP
~𝟏𝟏𝟏𝟏
𝒌𝒌𝒌𝒌/𝒔𝒔
n=5
First simultaneous observation of outboard and inboard ELM filaments†
Edge localized modes (ELMs)
Outboard
R [cm]
z [c
m]
140 160 180 200 220 240
-100
-50
0
50
100Inboard
KSTAR #9380 (t = 5.569 s)
Δ𝑇𝑇𝐸𝐸𝐸𝐸𝐸𝐸𝑇𝑇𝐸𝐸𝐸𝐸𝐸𝐸
TV image with EFIT
ECEIECEI
† J. Lee, KSTAR Conf. 2013; Yun, ITPA MHD 2014
10
~6 m
Lens
Detector
KSTAR 3D ECEI
ECEI-1(year 2010)Dual arrays
ECEI-2(year 2012)Combined with MIR
22.5°
Quasi 3D (year 2012)
(shot#7328, t=7.917s)
o Exact determination of Toroidal mode number *
o Toroidal asymmetry of ELM dynamics
*J. Lee, submitted to RSI. 11
R(cm)
Dual flux tubes† in 3D(Modified Sawtooth by ECH)
NOT A SIMULATION
z(cm)
𝑞𝑞 = 1surface
o The observed flux tubes are approximately aligned with the model flux tubes of m/n=1/1.
o Naturally explains the changes of the sawtooth period.
12
II. Microwave Imaging Reflectometry†
Imaging of 2D density fluctuationsDispersion of turbulent fluctuations
Specifications• Tunable probing frequencies from 78 to 92 GHz • Frequency spacing = 2 or 4 GHz• Channels: poloidal 16 and radial 2 • Spatial resolution: 1.6 cm (1/e2 width poloidal)• Channel spacing: 0.6 cm (poloidal), 1 ~ 17 cm (radial)• Detection limit of wave number: kθ = up to 3 cm-1
• Time resolution: 1 or 2 μs normal (0.5 μs min)
1~17 cm
0.6 cm
†W. Lee, NF (2014)
13
Source, array, and electronicsUpgraded to 4 frequencies in 2014
14
Imaging optics
Normalized response of each detector ∼1.6 cm 1/e2 width.
15
Spectral change of turbulent density fluctuations
r/a ~ 0.6 r/a ~ 0.7
* ECH r/a ~ 0.3
16
Lab-frame poloidal flow (𝑽𝑽𝜽𝜽∗ ) of density fluctuations
r/a ~ 0.6 (NBI-only)
Cross-coherence, 𝛾𝛾𝑥𝑥𝑥𝑥2 𝑓𝑓 = �𝐺𝐺𝑥𝑥𝑥𝑥 𝑓𝑓 2 𝐺𝐺𝑥𝑥𝑥𝑥 𝑓𝑓 𝐺𝐺𝑥𝑥𝑥𝑥(𝑓𝑓)
Cross-power, 𝐺𝐺𝑥𝑥𝑥𝑥 𝑓𝑓 = 𝑥𝑥∗ 𝑓𝑓 ⋅ 𝑦𝑦 𝑓𝑓 time
r/a ~ 0.7 (NBI-only)
17
Time evolution of 𝑽𝑽𝜽𝜽∗ during L-H transition†
†W. Lee, LAPD16, Madison, WI, 2013 18
Pow
er [M
W]
Te[k
eV]
ne [1
019m
-2]
Wto
t[kJ
]Hα
arb]
Splitter(8 way)
BandpassFilter
Detector
III. Fast RF spectroscopic system†
A prototype 8-channel RF spectrometer† has been developed in 2011 to detect RF emissionsduring MHD events such as sawtooth crashes and edge-localized mode (ELM) crashes.
A wide-band antenna was installed outside the vessel near the ECEI system (next slide).
1st ECEI2nd ECEI
Antenna
Wide-band bow-tie antenna0.2 ~ 2GHzVSWR < 2
Amp(~30dB)
†J. Leem, JINST 2012 19
Fast digitizer Wide-band
antenna
Three-axis loop antenna
Upgrade planned for fine-resolution full-band measurement and polarization measurement for the 2014 KSTAR campaign.
Similar filter-bank RF spectrometer is installed at LHD for comparative study (collaboration w/ T. Akiyama)
20
Example of RF burst at the ELM crashes
Dα
�̇�𝐵 [T/s]
RF@200 MHz@300 MHz
�̇�𝐵 [T/s]
Time [s]
(1) The RF captures the exact timing of ELM crash.
𝛿𝛿𝛿𝛿𝑒𝑒𝑒𝑒𝑒𝑒𝛿𝛿𝑒𝑒𝑒𝑒𝑒𝑒
10𝜇𝜇𝜇𝜇
LCFS
1
2
1
Dα
H-mode discharge𝐵𝐵0 = 2.3 T, 𝐼𝐼𝑃𝑃 = 550 kA,𝑛𝑛e0~2e19 m−3,Wtot = 220 kJ, NBI = 2.7 MW
RF@200 MHz@300 MHz
21
RF level change during the inter-crash period
�̇�𝐵 [T/s]
(2) Rapid enhancement and saturation of the RF emission level (around 200 MHz) is commonly observed during the inter-crash period. Modulation in the RF emission level is also often observed.
2
Dα
Dα
�̇�𝐵 [T/s]
RF@200 MHz@300 MHz
1
2RF @200 MHz @300 MHz
Possible mechanism: Mode conversion of ion cyclotron harmonic waves to compressional (fast) waves through the lower hybrid resonance
A useful diagnostic for pedestal evolution
22
Summary
Visualization is an essential tool for complex MHD and turbulence physics.
Achieved quasi-3D ECE imaging at the KSTAR tokamak through technological innovations
Realized MIR; measured the wave dispersion of density fluctuations
Fast RF diagnostic proved to be very useful for studying MHD crash dynamics, plasma waves, etc.
Work supported by NRF Korea, Japan-Korea Collaboration program and US DoE.
24
𝑛𝑛𝑒𝑒0 = 5 × 1013 cm−3
𝑇𝑇𝑒𝑒0 = 3 keV2fce
fce
fpe
fcutoff(x2)
ECEI window of operation
25
ECE downshift
Near the pedestal foot and outside, ECE signals come mostly from inside, a well-known phenomenon called downshift.
ECE downshift(not localized) Localized ECE
E. de la Luna et al., 34th EPS (2007)
JET H-mode pedestal
neTe
R (cm)
τ(µW/cm3/GHz)
26