status and plan for vest - enea and plan for vest vest device and machine status start-up...
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Status and plan for VEST
Y.S. Hwang and VEST team
Nov. 6, 2015Dept. of Nuclear Engineering
Seoul National University
Status and Plan for VEST
18th International Spherical Torus Workshop,Nov. 2-6, 2015, Princeton, NJ, USA
1/36 Status and plan for VEST
VEST device and Machine status Start-up experiments ECH/EBW heating as pre-ionization Low loop voltage start-up using trapped particle configuration DC helicity injection
Studies for Advanced Tokamak Research directions for high-beta and high-bootstrap STs Preparation of profile diagnostics Preparation for heating and current drive systems Discharge performance upgrade
Summary
Outline
2/36 Status and plan for VEST
VEST device and Machine status
VEST device andMachine status
3/36 Status and plan for VEST
Present Future
Chamber Radius [m] 0.8 : Main Chamber0.6 : Upper & Lower Chambers
Chamber Height [m] 2.4
Toroidal B Field [T] 0.1 0.3
Major Radius [m] 0.43 0.4
Minor Radius [m] 0.33 0.3
Aspect Ratio >1.3 >1.3
Plasma Current [kA] ~70 kA 200
Elongation ~1.6 >2
Safety factor, qa ~3.5 ~4
Specifications
VEST device and Machine StatusVEST (Versatile Experiment Spherical Torus)
Objectives Basic research on a compact, high-β ST (Spherical Torus)
with elongated chamber in partial solenoid configuration
Study on innovative start-up, non-inductive H&CD, high β
and innovative divertor concept, etc
4/36 Status and plan for VEST
VEST device and Machine StatusHistory of VEST discharges
• First plasma: 13.1.21 [#2946]• CS upgraded: 13.8.16 [#4763]• Inboard W limiter: 13.10.17 [#8274]• H2 GDC: 14.11.14 [#10508]: Maximum Ip of ~70 kA with pulse duration of ~10 ms• Inboard W limiter is covered with Graphite plate
5/36 Status and plan for VEST
Plasma elongation κ ~1.6 with edge safety factor qa ~ 3.7
VEST device and Machine StatusVEST discharge status
6/36 Status and plan for VEST
Start-up Experiments
Start-up Experiments
7/36 Status and plan for VEST
Start-up experimentsDouble null merging start-up?
Double null merging start-up? Not successful !
Field null formation under severe eddy currents !
8/36 Status and plan for VEST
EC / EBW heatingOver-dense plasmas with LFS XB mode conversion
300 400 500 600 700 800 9000.0
1.5
3.0
4.5
6.0
7.5
n e [1
017m
-3]
Microwave Power [W]
High Field Side X-mode Low Field Side X-mode
L-cutoff density1.45 x 1017m-3
1
1
Resonance
O cu
t off
HFS
LFS
: Cutoff(reflection)
: XB conversion
H.Y. Lee Low field side (LFS) X mode launching is preferable !
9/36 Status and plan for VEST
EC / EBW pre-ionizationVEST pre-ionization with LFS XB mode conversion
0 0.2 0.4 0.6 0.8 1-1.5
-1
-0.5
0
0.5
1
1.5Coil Geometry
R (m)
Z (m
)
2.45GHz6kW CW
ECH
15 20 25 30 35 40 45 50 55 60 65 70 75 80 850.0
0.2
0.4
0.6
0.8
1.0
1.2
n e [10
17m
-3]
R [cm]
TF Current: 8.2kAECR UHR
B0 ~ 0.1 T
15 20 25 30 35 40 45 50 55 60 65 70 75 80 850.0
0.2
0.4
0.6
0.8
1.0
1.2
n e [10
17m
-3]
R [cm]
TF current: 3.8kAECR UHR
B0 ~ 0.05 T
J.G. Jo Slightly less than L cut-off density !
10/36 Status and plan for VEST
Field NullConfiguration
Trapped ParticleConfiguration
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0.0
0.3
0.6
0.9
1.2
1.5 Trapped Particle Configuration Field Null Configuration TF only
BT~0.05 T at R=0.4 m
n e [10
17m
-3]
R [m]
Inner Wall Outer Wall
Significant enhancement of pre-ionization under TPC (Trapped Particle Configuration)
Severe degradation of pre-ionization under field null
Ohmic Start-up with ECH Pre-ionizationEnhanced pre-ionization in TPC
Y.H. An
11/36 Status and plan for VEST
Ohmic Start-up with ECH Pre-ionizationHigher dIp/dt and Wider Operation Regimes with TPC
1 2 3 4 5 6
0
1
2
3
4
5
6
7
dIp/d
t [kA
/ms]
ECH Power [kW]
with TPC without TPC
No current initiation10-5 10-4
-1012345678
dIp/d
t [kA
/ms]
Filling Pressure [Torr]
With TPC Without TPC
No current initiation
20 40 60 80 100 120 140 160 180123456789
10 with TPC without TPC
dIp/d
t [kA
/ms]
Et*Bt/Bp [V/m] at R=0.4m
Higher dIp/dt under TPC with identical Vloop and EtBt/BpWider operating windows for gas pressure and ECH power
Y.H. An
12/36 Status and plan for VEST
TPC intrinsically forms equilibrium field that can provide stable Bv even at the low Ip and stable decay index in all times enabling prompt Ip initiation.
Volt-sec saving of about 40% with TPC compared to the case without TPC
Ohmic Start-up with ECH Pre-ionization Prompt Ip initiation in TPC with volt-sec saving
TPC
Y.H. An
13/36 Status and plan for VEST
Ohmic Start-up with ECH Pre-ionizationTPC as an Efficient Start-up Method
Enhanced pre-ionization by increase of particle confinement
Prompt Ip initiation due to the intrinsic stable Bp configuration
Start-up with low loop voltage, low volt-second consumption,
low ECH power and wider pressure window.
Start-up without waste of volt-second
by enabling prompt Ip initiation
•Low loop voltage start-up of super-conducting tokamaks such as ITER
•The efficient start-up of spherical tori withlimited volt-second by reduced V∙sconsumption
• Reduced V∙s consumption and extendeddischarge duration by prompt Ip initiationparticularly for super-conductingtokamaks with the limited current slew-rate of super-conducting PF coil*
• TPC can be an alternative to the widely used field null configuration for more efficientECH-assisted start-up.
* In super-conducting tokamaks, the use of field null requires transition of the Bp structure to the equilibrium field which takes considerable time limiting Ip ramp-up rate
Trapped Particle Configuration
14/36 Status and plan for VEST
EC / EBW pre-ionizationOver-dense Plasma Formation with EBW heating in TPC
• Mode conversion efficiency is calculated with 1-d full wave simulation• EC/EBW heating with 6kW CW ECH
- Bo~0.05T : Broad density profile makes low MC conversion efficiency (0.0105)- Bo~0.1T : Steep density gradient near UHR and relatively high MC efficiency (0.2625)
• EC/EBW heating with additional 10 kW pulsed ECH power- Clear over-dense plasma formation with EBW mode conversion near UHR- Bo~0.05T: low MC efficiency (0.0105→0.4819), Bo~0.1T: high MC efficiency (0.2526→0.756)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80.00E+000
5.00E+016
1.00E+017
1.50E+017
2.00E+017
2.50E+017
3.00E+017
3.50E+017
4.00E+017
Radius (m)
R cutoffUHRL cutoff
Dens
ity (#
/m3 )
TPC PF 3&4 with ECH 6 kW TPC PF 3&4 with ECH 6&10 kW
ECR
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80.00E+000
5.00E+016
1.00E+017
1.50E+017
2.00E+017
2.50E+017
3.00E+017
3.50E+017
4.00E+017
Radius (m)
Dens
ity (#
/m3 )
R cutoff
L cutoff
UHR
TPC PF 3&4 with ECH 6 kW TPC PF 3&4 with ECH 6&10 kWECR
B0 ~ 0.1 TB0 ~ 0.05 T
H.Y. Lee More than L cut-off density !
15/36 Status and plan for VEST
DC Helicity Injection
The Electron Gun and Power systemPlasma washer gun
• High electron current based on arc discharge • Low impurity• Washer stacks
Power system configuration• Single and Double power system• PFN - Composed of circuits consist of C & L
2. Double power system-PFN for Arc discharge-PFN for Injection voltage
1. Single power system- PFN for Arc discharge & injection
Lower GunZ = - 0.98 mR = 0.25 m
The location of injector• Assembled into a stainless steel pipe
• Designed to adjust the radial location
J.Y. Park
16/36 Status and plan for VEST
DC Helicity InjectionVisual evidence of reconnection from current stream
No reconnection (Shot # 12077)
402 ms 404 ms 406 ms 408 ms
402 ms 404 ms 406 ms 408 ms
𝑉𝑉𝑖𝑖𝑖𝑖𝑖𝑖 ~ 200V / 𝐼𝐼𝑖𝑖𝑖𝑖𝑖𝑖 1.2kA / PFN Charging of 1.2 kV Current steam stacking defined by helical vacuum field
Reconnection (Shot # 12086)
𝑉𝑉𝑖𝑖𝑖𝑖𝑖𝑖 ~ 500V / 𝐼𝐼𝑖𝑖𝑖𝑖𝑖𝑖 1.5kA / PFN Charging of 1.6 kV Multiplication factor more than stacking ratio
J.Y. Park
17/36 Status and plan for VEST
DC Helicity Injection – Single power system
Current Sheet Formation
Lower Gun LocationR = 0.25 m
Z = - 0.804 m
401 ms 402 ms 403 ms400.4 ms
Magnetic Field Structure Stacking ratio, G = 7 ~ 8Multiplication, M = ~ 16
400 402 404 406 408 410 412 414 416-10-9-8-7-602468
0.00.51.01.52.00.0
-0.2-0.4-0.6-0.8-1.0
05
101520
Vacuum field @ Z = 0, R= 0.089
B z [m
T]
Time [ms]
Plasma field @ Z = 0, R= 0.089
B z [m
T]
I inj [k
A]
Vin
j [kV]
I toro
idal [k
A]
A toroidal current of up to ~20 kA has been generated by the electron gun.• Increased multiplication factor confirmed as current streams reconnected, but • Neither radial force balanced nor relaxed to tokamak like plasma.
Very dynamic states of current sheet are observed.• Toroidal current is more sensitive to injection voltage than injection current.• 𝑽𝑽𝒊𝒊𝒊𝒊𝒊𝒊 and 𝑰𝑰𝒊𝒊𝒊𝒊𝒊𝒊 change with plasma states due to the PFN characteristics.
J.Y. Park
18/36 Status and plan for VEST
400 402 404 406 408 410 412 4140.00.20.40.60.81.00.00.51.01.52.0
0
10
20
30
40
I inj [k
A]
Time [ms]
V inj [k
V]
I p [kA
]DC Helicity Injection – Double power system
Tokamak-like Plasma Formation
A plasma current of up to ~30 kA has been generated with high 𝑉𝑉𝑖𝑖𝑖𝑖𝑖𝑖• Tokamak-like plasma formation confirmed !
Gradual decrease in injection currents keeps from further plasma current increases. Injection power supply with current regulation under preparation
R (m)
Z (m
)
Psi contour at t = 400 ms
0.2 0.4 0.6 0.8 1-1.5
-1
-0.5
0
0.5
1
1.5
-10
-8
-6
-4
-2
0
2
x 10-3
400.4 ms Peak @ 409.2 ms
J.Y. Park
19/36 Status and plan for VEST
Research Plan for Advanced Tokamak
Studies for Advanced Tokamak
20/36 Status and plan for VEST
Research PlansExperimental research direction for VEST
Fusion reactor requireshigh beta (or Q) and high bootstrap current
Alpha heating (high Q) Centrally peaked pressure profile
Stability and Confinement ?
High power neutral beam heating
Hollow current density profile (low li) Centrally peaked pressure profile
Current density profile controlBootstrap/EBW/LHFW
Profile diagnostics
21/36 Status and plan for VEST
Research PlansExperimental research direction for VEST
Advanced Tokamak Scenario
Simultaneous achievement of high beta and high bootstrap current is required for advanced tokamak scenario.
High bootstrap current fraction in reversed shear mode+
High beta in spherical torus with low aspect ratio
Spherical Torus with Reversed Shear• Sufficient confinement from ITB formation by RS• Possible high beta even with low li in RS due to low aspect ratio
Advanced Tokamak Regime in VEST*
Low toroidal field(0.1T) with high βN(~7)< βN,Menard(8.7) and Ip(0.08 MA).
Fully non-inductive CD with 80% bootstrap fraction may be possible with ~500kW.
High H factor(~1.2) needs to be attempted by forming ITB with MHD stability.
* Estimated by 0-D system code
High power NBI to center, forming RS in VEST!
22/36 Status and plan for VEST
Profile diagnosticsDiagnostic systems in VESTDiagnostic Method Purpose Remarks
MagneticDiagnostics
Rogowski Coil Plasma current & eddy current
3 out-vessel &in-vessel coils
Pick-up Coil & Flux Loop
Bz, Br &Loop voltage, flux
56 pick-up coils9 loops
Magnetic Probe Array Bz, Br measurement inside plasma Movable single array
Probe Electrostatic Probe Radial profile of Te, ne2 Triple Probes
Mach probe
OpticalDiagnostics
Fast CCD camera Visible Image 20kHz
Hα monitoring Hα Hα filter+ Photodiode
Impurity monitoring O & C lines Spectrometer
Interferometry Line averaged ne 94GHz, single channel
Reflectometry Radial profile of ne Edge density profile
EBE radiometer Core, edge Te BX mode conversionCharge Exchange
Spectroscopy Rotation and Ti DNB
Thomson Scattering Te, ne profile NdYAG laser
23/36 Status and plan for VEST
Profile diagnosticsDiagnostic systems in VEST
BZ
BT
BR
J.H. Yang
Direct Measurement of mid-plane Toroidal Current Density Profile
Hall sensor array
Full equilibrium reconstruction is under development
24/36 Status and plan for VEST
High power NBIHigh power low energy NBI preparation
S.H. Chung (KAERI)Two beams with 300kW eachFirst beam by FY2016-2017
width
length
Ion source under test
25/36 Status and plan for VEST
High power NBIReduced beam loss with magnetic well formation
well shape 1 well shape 1 well shape 2 well shape 2
Beam energy (𝑬𝑬𝒃𝒃) 20 keV 25 keV 20 keV 25 keV
𝑰𝑰𝒑𝒑 (𝐤𝐤𝐤𝐤) 𝟖𝟖𝟖𝟖 𝟖𝟖𝟖𝟖 𝟖𝟖𝟖𝟖 𝟖𝟖𝟖𝟖
𝒊𝒊𝟖𝟖 (𝟏𝟏𝟖𝟖𝟏𝟏𝟏𝟏/𝐜𝐜𝒎𝒎𝟏𝟏) 𝟏𝟏 𝟏𝟏 𝟏𝟏 𝟏𝟏
Injection angle (𝛗𝛗) 𝟒𝟒𝟖𝟖° 𝟒𝟒𝟓𝟓° 𝟏𝟏𝟖𝟖° 𝟏𝟏𝟓𝟓°
Shine through (𝑹𝑹𝒔𝒔) 𝟏𝟏𝟖𝟖 → 𝟐𝟐𝟐𝟐𝟐 𝟏𝟏𝟓𝟓 → 𝟏𝟏𝟐𝟐𝟐 𝟏𝟏𝟖𝟖𝟐 𝟏𝟏𝟖𝟖𝟐
Orbit loss 𝟏𝟏𝟖𝟖 → 𝟏𝟏𝟔𝟔𝟐 𝟔𝟔𝟖𝟖 → 𝟏𝟏𝟐𝟐𝟐 𝟐𝟐𝟐 𝟔𝟔𝟐
Total beam loss 𝟔𝟔𝟔𝟔 → 𝟒𝟒𝟏𝟏𝟐 𝟗𝟗𝟓𝟓 → 𝟒𝟒𝟗𝟗𝟐 𝟏𝟏𝟐𝟐𝟐 𝟒𝟒𝟒𝟒𝟐
(NUBEAM, Optimized injection condition for VEST)
(Optimized injection condition for VEST with well) shape 1)
S.K. Kim
26/36 Status and plan for VEST
< CMA diagram of Helicon Wave>
High Power NBI and fast Lower Hybrid systems from KAERI
Plasma density
SW
FWabsorption
absorption
< Helicon Wave Dispersion Relation >
nsw ~n||2 ω2 nfw ~n||
2 ω ωce n0 ~n||2 ωce
2
For high density plasma in fusion reactor• Slow wave branch of LHW
→ Absorbed at the edge region• Fast wave branch of LHW
→ Possible absorption at the core region
Proof of principle of current drive scheme by fast wave branch of LHW in VEST
Current density profile controlCore heating by LHFW
S.H. Kim (KAERI)
27/36 Status and plan for VEST
Possible propagation regime in CMA diagram- FW launching density ~ f(n||, w, wce)- FW-SW confluence density ~ f(n||, wce)
FW path
# Accessibility condition is satisfied.<f=500[MHz], n0= 3x1018[#/m3] B0=0.2[T], n∥=4.0>
Accessibility for Lower Hybrid Fast Wave(LHFW)
Current density profile controlLHFW accessibility
S.H. Kim (KAERI)
28/36 Status and plan for VEST
Current density profile controlRay Tracing Simulation with GENRAY
Parameters ValuesB0 0.2 TFrequency 500 MHzN∥ 4.0Core density 3x1018 #/m3
Edge density 4x1017 #/m3
Core temperature 3 keVEdge temperature 0.2 keV
The parallel refractive is 4.0 which
satisfies the accessibility condition for the
given magnetic field and RF frequency.
The propagations and driven currents are
calculated with GENRAY code for LHFW
and LHSW launching cases on VEST.
The LHFW can propagate into more
central region and the driven current is
comparable to that of LHSW.
Parameters for ray tracing calculation on VEST
Ray tracing : (a) ray, (b) driven current profile
Ray tracing simulation
S.H. Kim (KAERI)
29/36 Status and plan for VEST
Current density profile controlLHFW Components
Klystron
Parameters ValuesFrequency 470~700 MHzOutput power 37.5 kWGain 48 dBBeam voltage 19.5 kVBeam current 5.4 AElectrode voltage 19.5 kVHeater voltage 7 VHeater current 17 ABody current 50 mAMagnet voltage 145 VMagnet current 32 ACollector cooling Water 2.0 gal/minBody cooling Water 1.5 gal/minMagnet cooling Water 2.0 gal/minGun cooling Forced air 50 ft3/min
Specification of klystron
Curved antenna for LHFW RF system on VEST
Parallel refractive index spectrum (a) and S-parameters (b) of curved inter-digital antenna designed.
The klystron is prepared by refurbishing anold UHF broadcasting system of Korea whichhas been hold by SNU..
In 480~496 MHz frequency range, theparallel refractive index is between 3.5 and4.5 and the S-parameters S11 and S12 areless than -10 dB.
Antenna
S.H. Kim (KAERI) and B.J. Lee (Kwangwoon Univ.)
30/36 Status and plan for VEST
GENRAY, CQL3D, mode conversion codes are used Perpendicular, LFS, X-mode injection
• Short distance between R(X) cut-off and UHR• High XB mode conversion efficiency with low n||
• Good central heating and current drive expected
► Core heating and current drive with XB mode conversion
<Absorbed power>
<Driven current>
Absorption near EC fundamental resonance
EBWpropagation
ECR
Absorption near EC fundamental resonance
EBWPropagation
Current density profile controlEBW heating with XB mode conversion
S.H. Kim (KAERI)
31/36 Status and plan for VEST
► EBW heating (6kW cw+10kW pulse) on Ohmic plasmas with TPC
Current density profile controlEBW heating with XB mode conversion in VEST
395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 4100
5000
10000
15000
20000
25000
Plas
ma
Curre
nt (A
)
Time (ms)
TF 8.2 kA TPC Startup with 6 kW (R = 0.5 m) TF 8.2 kA TPC Startup with 6&10 kW (R = 0.5 m)
404 ms
0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.800.00E+000
1.00E+017
2.00E+017
3.00E+017
4.00E+017
5.00E+017
6.00E+017
7.00E+017
8.00E+017
Radius (m)
Dens
tiy (#
/m3 )
0
5
10
15
20
25
30
35
40
Temperature (eV)
L CutoffUHRR Cutoff
395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 4100.00E+0001.00E+0172.00E+0173.00E+0174.00E+0175.00E+0176.00E+0177.00E+0178.00E+0179.00E+0171.00E+0181.10E+0181.20E+0181.30E+0181.40E+0181.50E+018
Dens
ity (#
/m3)
time (ms)
TF 8.2 kA TPC Startup with 6&10 kW (R = 0.5 m) TF 8.2 kA TPC Startup with 6 kW (R = 0.5 m)
H.Y. Lee
B0 ~ 0.1 T
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80.00E+000
2.00E+017
4.00E+017
6.00E+017
8.00E+017
1.00E+018
1.20E+018
1.40E+018
R CutoffUHRL Cutoff
TPC Pre-ionization with ECH 6 kW TPC Startup with ECH 6 kW TPC Startup with ECH 6&10 kW
ECR
32/36 Status and plan for VEST
Research PlansPreparation for High Density Target Plasmas
High density Ohmic plasmas with >80kA for >20ms
Preparation for high density plasmas as NBI target• Low shine through and good coupling
Target plasmas for VEST NBI• R0=0.4 m, a=0.3 m → R0=0.35 m, a=0.25 m• Ip<70 kA for 10 ms with elongation < 1.6
→ Ip>80 kA for >20 ms with elongation > 2
Implementation• Wall conditioning : GDC, baking• TF & PF power system upgrade• Feed-forward/back control system
H-bridge circuit
33/36 Status and plan for VEST
Discharge performance upgradeWall conditioning with hydrogen GDC
Wall conditioning using H2 GDC• Oxygen impurities are reduced
significantly with GDC• Plasma pulse duration extended
accordingly with reduced OⅠ radiation• Inboard limiter considered as major
oxygen impurity source• Increased H alpha radiation in the
initial phase with increased treatmenttime
• Strong hydrogen retention inboardlimiter confirmed with hydrogen GDC
H2 GDC more than 4 hours is need toremove water for long pulse plasmadischarge.
Active cooling of inboard limiter is underpreparation for baking400 404 408 412 416 420
-20
0
20
40
60-3
-2
-1
0
-0.8
-0.4
0.0
13119: Before H2 GDC 13122: After H2 GDC (1hour) 13127: After H2 GDC (3hour) 13087: After H2 GDC (4hour) 13132: After H2 GDC (6hour)
Plas
ma
Curre
nt [k
A]
Time [ms]
H α 6
56 n
m [A
.U.]
O I l
ine
777
nm [A
.U.]
H.Y. Lee
34/36 Status and plan for VEST
Discharge performance upgradeUpgrade of TF and PF power supplies
TF field will be increased by adding capacitors (0.1T 0.2~0.3T) PF curret waveform will be modified for better loop voltage utilization
J.H. Yang
35/36 Status and plan for VEST
Summary VEST has achieved successful ohmic operation with plasma currents of up to ~70 kA,
elongation of ~ 1.6 and safety factor of ~3.5 with ECH pre-ionization.
EBW heating with direct XB mode conversion from LFS launching by generating over-dense plasma in the pre-ionization phase with TPC structure as well as ohmic plasmas.
TPC(Trapped particle configuration) is developed as an efficient ECH-assisted start-upmethod. Enhanced pre-ionization improves start-up with low loop voltage, low ECH power and wider
pressure window. Intrinsic stable magnetic structure leads volt-sec saving with prompt Ip initiation and smooth
coil current change.
DC helicity injection startup experiments generate plasma current of ~20 kA with singlepower and ~30 kA with two power system, confirming tokamak-like plasmas.
Experimental preparation for the study of advanced tokamak is progressing. Profile diagnostics are under preparation High power NBI of ~ 500 kW and prototype NBI are under development. EBW/LHFW heating and current drive experiments are under preparation by performing
simulations and preparing hardware systems.
36/36 Status and plan for VEST
Thank you for your attention !
37/36 Status and plan for VEST
EC / EBW pre-ionizationLow loop voltage start-up with ECH pre-ionization
Fast camera image at 336ms
Fast camera image at 400ms
38/36 Status and plan for VEST
ECH/EBW pre-ionizationSignificant enhancement of ne & Te under TPC
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4 Trapped Particle Configuration Field Null Configuration TF only
n e [10
17m
-3]
R [m]
Inner Wall Outer WallTF current: 8.2kA
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0.0
0.3
0.6
0.9
1.2
1.5 Trapped Particle Configuration Field Null Configuration TF only
TF current: 5.6kA
n e [10
17m
-3]
R [m]
Inner Wall Outer Wall
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0.0
0.3
0.6
0.9
1.2
1.5 Trapped Particle Configuration Field Null Configuration TF only
TF current: 3.9kA
n e [10
17m
-3]
R [m]
Inner Wall Outer Wall
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
5
10
15
20
25
30
35 Trapped Particle Configuration Field Null Configuration TF only
TF current: 5.6kAT e [
eV]
R [m]
Inner Wall Outer Wall
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
5
10
15
20
25
30
35 Trapped Particle Configuration Field Null Configuration TF only
TF current: 3.9kA
T e [eV
]
R [m]
Inner Wall Outer Wall
Significant enhancement of pre-ionization plasma with trapped particle configuration Significant degradation of pre-ionization plasma with field null configuration
Temperature peaks near ECR resonance
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
5
10
15
20
25
30
35 Trapped Particle Configuration Field Null Configuration TF only
TF current: 8.2kA
T e [eV
]
R [m]
Inner Wall Outer Wall
39/36 Status and plan for VEST
Field NullConfiguration
Trapped ParticleConfiguration
Ohmic Start-up with ECH Pre-ionizationEnhanced pre-ionization with mirror trapping
Rm ~ 3 Rm ~ 1
ECR layer
J.W. Lee
40/36 Status and plan for VEST
Research PlansAdvanced Tokamak Study with VEST
R0(m) 0.4 0.4 0.35 0.35
a(m) 0.3 0.22 0.25 0.19
A 1.33 1.8 1.4 1.8
Kappa 2.227 1.922 2.167 1.922
βN from βT 7.351 12.317 6.951 9.238
fboot 0.8 0.8 0.8 0.8
βT 0.314 0.191 0.220 0.143
BT(T) 0.09 0.21 0.10 0.20
Ip(MA) 0.11 0.07 0.08 0.06
nave(1020m-3) 0.20 0.23 0.21 0.25
Te_ave(keV) 0.10 0.29 0.09 0.19
PCD(MW) 0.72 0.18 0.51 0.23
τE_H98y2(sec) 0.00206 0.00302 0.00141 0.00170
τE(sec) 0.00218 0.01368 0.00171 0.00494
HH 1.06 4.52 1.21 2.91
VEST Advanced Tokamak Regime with system code Low toroidal field(0.1T) with high βN(~7)< βN,Menard(8.7) and Ip(0.08 MA).
Fully non-inductive CD with 80% bootstrap fraction may be possible with ~500kW.
High H factor(~1.2) needs to be attempted by forming ITB with MHD stability.
Reversed shear mode in ST
RS may have sufficient confinement with ITB formation
ST may have high βN even with low li in RS
High power NBI to center, forming RS! Stable?