HGota_APS-DPP2018_Poster_v1

Abstract
The C
-
2W Device (a.k.a. Norman)
Progress / Improvement in FRC Performance
• Ti-gettering systems in confinement vessel / divertors have reduced impurity content and wall recycling (i.e. improved pumping capability)
• FRC performance – commensurate increase with vacuum/wall conditioning as well as effective optimization processes
• Total temperature (ion + electron; from pressure balance) consistently increased; earlyTtot upto2keV
Contact / Email: hgota@tae.com Company website: https://tae.com
H. Gota,1 M.W. Binderbauer,1 T. Tajima,1 S. Putvinski,1 M. Tuszewski,1 S. Dettrick,1 A. Smirnov,1 M.C. Thompson,1 X. Yang,1 A.A. Ivanov,2 and the TAE Team1
1TAE Technologies, Inc., 19631 Pauling, Foothill Ranch, CA 92610 2Budker Institute of Nuclear Physics, Novosibirsk, 630090, Russia
60th APS-DPP Meeting, Portland, OR, November 5–9, 2018
[1] M.W. Binderbauer et al., AIP Conf. Proc. 1721, 030003 (2016).
Field
• A field-reversed configuration (FRC) plasma is a highly elongated compact toroid (CT) which has a closed poloidal field with zero or small self-generated toroidal field, an axisymmetric structure with a natural divertor, and a high beta value (β~1).
• FRC offers an ideal configuration for an economic reactor and may allow use of aneutronic fuels, such as D-3He and p-11B.
• Tangential neutral beam injection (NBI): large orbit ion population, increased stability, and improved transport property
• Fast ions: decoupled from micro turbulence, slow down at near classical rates
TAE’s Research Progress (until 2016)
Plasma guns and biasing electrodes: high voltage & long pulse capability
1.2 Tigetterin 1
-
Reversed Configurations and TAE’s Approach
1 00
Overview of C-2W Field-Reversed Configuration Experimental Program
TAE Technologies’ research is devoted to producing high temperature, stable, long-lived field-reversed configuration (FRC) plasmas by neutral-beam injection (NBI) and edge biasing/control. The newly constructed C-2W experimental device (also called “Norman”) is the world’s largest compact-toroid device and has the following key upgrades from the preceding C-2U device [1]: (i) higher injected power, optimum energies, and extended pulse duration of the NBI system; (ii) installation of inner divertors with upgraded edge-biasing systems; (iii) fast external equilibrium/mirror-coil current ramp-up capability; (iv) installation of trim/saddle coils for active feedback control of the FRC plasma; and (v) extensive upgrade/expansion of plasma diagnostic capability. C-2W experiments have already produced dramatically improved initial FRC parameters with much higher plasma temperatures (Te >250 eV; total electron and ion temperature >1.5 keV) and more trapped flux inside the FRC immediately after the merger. Plasma duration/lifetime has reached up to ~9 ms via outer-divertor edge biasing. This paper will review highlights of the C-2W program, including recently obtained experimental results.
Inner divertor:
high vacuum pumping
Designed C-2W Parameters
Hollow density profile
Much higher initial temperature
C-2W
C-2/2U
0 10 20 30 40 50 60 Radius (cm)
Temperature profiles right after FRC collision/merging (t~0.05 ms)
• C-2U like FRC performance has been successfully obtained via dedicated optimization processes as well as effective edge control & NBI
• Transferring edge control areas from outer to inner divertors is the “key” to further improve FRC performance with hotter temperature
C
-
2W
New / Upgraded Key Subsystems on C
-
2W
102900 103100 103300 103500 103700 103900 104100 104300
Shot Number
Improvement in FRC lifetime with wall conditioning
103400 103500 103600 103700 103800 103900 104000 104100 104200
Shot Number
Improvement in Ttot (estimated from Thomson ne)
New confinement vessel:
skin time <3 ms
Goals
New magnet system:
field ramp & active control
Ti getter in CV
0.8 0.6 0.4 0.2
Upgraded NB’s: ~13 MW, ~30 ms (~21 MW in Phase 2)
Parameter
Bext, T rs, cm
Upgraded formation sections: ~15 mWb trapped flux
Outer divertor:
high vacuum pumping
~0.1–0.3 ~40 ~3
Value
T , keV ~0.2–1 7 e 6
I , MA ~1 5 p 4
Pulse length, ms up to 30 3 2
Ls,m
ne, m-3 ~3–5􏰀1019
Ti, keV ~1–2 8
Plasma Lifetime_T5 History
Total Temperature History/Trend
9
Ti getter in 2
(2) Inner divertor operating mode
(1) Outer divertor operating mode
hg20180120.tae.1b
Plasma Lifetime, T5 (ms)
Ti gettering started
Total Temperature (keV)
Te (eV)
w/o Ti getter
Out-DIVs
In-DIVs
1.8
1.6
1.4
Ttot_TS@50us Ttot_TS@100us Ttot_TS@200us
hg20150827.tae.2b
A & B – Basic FRC core
n 100-800G,5-10eV
n ion beams, Wb ~0.1 kJ
C-1 – Enhanced lifetime
n 400G,10eV
n ion beams, Wb ~1 kJ
C-2 – HPF* w/ 2 guns, Ti getter
n 1kG,1keV
n neutral beams, Wb ~12 kJ
C-2 – HPF* w/ 2 guns, Li getter
n 1kG,1keV
n neutral beams, Wb ~20 kJ
C-2U – Sustainment 5+ ms
n 1kG,1keV
n neutral beams, Wb ~100 kJ
* HPF – High Performance FRC regime
Features of Divertors:
• High pumping speed (~2x106 L/s in hydrogen) to reduce gas recycling
• Field expanders to minimize electron cooling from ionization and secondary emission
• Concentric electrode biasing to stabilize plasma as well as for auxiliary heating
• Independently controllable edge biasing (polarity, potential, timing)
• Ti-gettering system can be operated between shots
(using deuterium)
Divertor pumping test (with Ti-arc and LN2 systems)
#107322:
Flaring field with biasing
Particle confinement time in C-2 (vs others)
Global energy confinement time in C-2/2U
NBI
• Over 50,000 shots in C-2/2U
• Summary papers on C-2/2U: M.W. Binderbauer et al., Phys. Plasmas 22, 056110 (2015); H. Gota et al., Nucl. Fusion 57, 116021 (2017)
• Established high-performance FRC / beam-driven FRC plasma states
• 10x improved particle confinement; global energy confinement time improved via various key subsystem operations and optimizations
• Strong positive correlation between energy confinement time and electron temperature
è Emerged new scaling law
Electron energy confinement time vs. electron temperature in C-2/2U
Edge Control / Biasing using Outer & Inner Divertors
#107226: Flaring field w/o biasing
#107322: Flaring field with biasing
Te increased (up to 180 eV)
#104989:
Edge biasing from outer divertors (C-2U like)
• •
• •
Demonstrate plasma parameter ramp up by NB heating and current drive
Improve performance of the plasma edge/divertor to achieve high electron temperature at the plasma edge
Develop plasma control on the time scale significantly longer than L/R vessel time and plasma confinement times
Explore a wide range of plasma parameters such as plasma temperature, magnetic field and plasma size to confirm TAE energy confinement scaling
• NB injectors – 8 injectors, 4 out of 8 NBs w/ tunable beam energy at 15–40 keV during a shot, up to ~21 MW for ~30 ms
• Enhancement of edge biasing – plasma guns and biasing electrodes in inner/outer divertors, higher voltage and longer pulse operation (>30 ms)
• New confinement vessel – short skin time for field ramp-up / plasma control • New/upgraded magnets – field ramp-up, active plasma control, fast-
switching coils inside inner divertors, independently controlled power supplies
• New/upgraded divertors – additional divertors in between confinement and formation sections, higher vacuum pumping capability
• Formation pulsed powers – a lot higher stored energy, improved gas pre- ionization, improved system reliability
• Extensive diagnostics upgrade
Edge Biasing/Control Effect on FRC Performance
Confinement Vessel Camera (quiescent FRC)
Inner Divertor Camera: Flared magnetic field
Outer Divertor
Cryopanels
(Ti-arc w/ LN2)
GDT-type plasma gun
Coaxial Electrodes
early
experiments and commissioning
were
C
-
- translated through inner divertor
conducted with single
C
C
-
-
ms
#104989: Edge biasing from outer divertors (C-2U like operation)
Plasma Radius
Electron Density
Electron Temperature
Total Temperature
#107226: Flaring field w/o biasing
Te profile evolution under 3 different operating conditions
Summary and Future Plan
•
• •
• • •
2U dismantlement
• Merged initial FRC state exhibited much higher plasma temperatures (Te>250 eV; Ttot >1.5 keV)
);
lived, stable FRC plasmas using outer divertor edge biasing (lifetimes up to ~9 area where new electrode biasing is applied
Further improve FRC performance with tunable NB injection as well as inner divertor edge biasing/control Field ramp in the confinement section with active feedback control
Demonstrate sufficient particle refueling
2W was constructed in ~1 year (including C
-
sided setup to study initial FRC formation and translation in which FRC was successfully
-
Demonstrated adequate magnetic field flaring at inner divertor
)
2W has
produced
2U like long