Demo

D- He and p- B
Collision & Thermalization
Vz ~ ±300km/s
Translation through Mirror
Ti ~ 100eV
Ti ~ 1keV Stabilizing the FRC Target
! Employ EM NPA with 39 channels per species
! Average over 7 shots
! Thermal deuterium and beam proton spectrum
! t<1 ms deuterium spectrum is post-collision
! Beam energy 15 kev
! Beam energy > injected energy
! Energetic tail formation in deuterium for t>1 ms
! Neutron rate much greater than thermonuclear
! Using deuterium energy spectrum from NPA recovers the neutron rate
Simulation
! 1D3V PIC initial value problem
! Proton is beam ring in velocity space
! Presence of the proton beam is a source of “free energy”
! Transfer energy from proton beam to deuteron background
! Energetic super-thermal tail forms in the deuteron plasma
! Accelerated deuterons collide with thermal (or super-thermal) deuterons
3 11
! Tangential beam injection: large orbit ion population, increased stability, and improved transport property
! Fast ions: decoupled from micro turbulence, slow down at near classical rates
The C-2U Device
C-2U Physics Overview
A. Necas1,D.C. Barnes1, E. Belova2, F. Ceccherini1, R. Clary1, S. Dettrick1,H. Gota1, L. Galeotti1, E. Granstedt1, R. Magee1, Y. Mok1, S. Nicks1, M. Onofri1, J. Romero1, T. Tajima1, E. Trask1, and the TAE Team1 1TRI ALPHA ENERGY, INC., P.O. Box 7010, Rancho Santa Margarita, CA 92688-7010
Abstract
C-2U is a unique hybrid field-reversed configuration (FRC) where we successfully combine a high-beta (~1) FRC plasma with neutral beam injection (NBI), field line biasing, and mirror physics. The C-2U experiment at Tri Alpha Energy tested this hybrid concept by studying the evolution of advanced beam-driven FRC plasmas sustained by NBI for 5+ ms [1]. C-2U is an upgrade to the earlier C-2 [2] experiment with an improved NBI system which can deliver a total injected power of 10+ MW hydrogen beam, by far the largest ever used in a compact toroid plasma experiment. This increase in the beam power, combined with our earlier innovations in FRC stabilization, successfully produced high-performance, advanced beam-driven FRCs sustained for times significantly longer than the characteristic plasma decay times. This accomplishment represents a significant advance towards the scientific validation of the FRC- based approach to fusion. This presentation will provide an overview of the C-2U device and recent experimental advances as well as particle in cell 1D3V simulation of non-destructive beam-driven instabilities in high-beta using EPOCH [3].
2 PPPL, Princeton University, P.O. Box 451 Princeton, NJ 08543-0451
Simulation of Forming, Translating and Evolving the FRC Target
2017 Sherwood Fusion Conference, May 1-3, Annapolis, MD
Robust BUT non-destructive (vf>vthi) instability during beam injection**,++
Field-Reversed Configurations
! A field-reversed configuration (FRC) plasma is a highly
elongated compact toroid (CT) which has a closed poloidal
field, an axisymmetric structure with a natural divertor, and a
high beta value (β~1). Ideal to burn aneutronic fuels, such as
" Integratedmodelingwith2D(r,z)LamyRidgeMHD code(Mok)
! MHD plasma model, coupled to neutral fluid model
! All coils, shaped walls, pulsed power circuits
! Ongoing efforts to study optimization of FRC pulsed power arrangements
"
"
"
"
Q2D (Onofri, Dettrick, Barnes)
" Based on 2D (r,z) LamyRidge XMHD code
" Fluid plasma and fluid neutral species
" Kinetic fast ions from NB injection
" Beam pressure > total pressure
" Classical ions
" Anomalous electrons
Interaction with neutrals important
" Self-consistent warm neutral cloud from NBI
" Wall recycling coefficient R~1
" CX loss of fast ions; plasma fueling
" Brings total pressure and density in line with experiment
Q2D run on C-2U using transport coefficients calibrated on C-2
" Gives decent agreement on profile evolution
" NBI extends plasma lifetime by factor ~ 5 Performed confinement comparison of
FRC vs. mirror
Increased neutron yield
• Deuteron Tail
• Beam energiza6on
Magne6c fluctua6on
Consistent df/dv
C-2U Neutral Beam System Specification
Stability to rotation—HYM Code
FRC spin-up due to particle loss and resistive decay (S*=9) ! Hybrid PIC simulations with HYM code ( E. Belova, PPPL)
Stability of Tilt Mode – FPIC Code
! ComparisonofendBCs Parameter Value End-shorting
End-shorting
t / t
Biasing
high
•
•
• 104.1 127.2
Fully kinetic ions, fluid electrons
Ohm’s law, no displacement current
Growth rate agrees with analytic theory [4]
Nonlinear saturation of tilt leading to new FRC equilibrium [5]
Elongated FRCs and beam presence (Belova) stabilizes n=1 tilt mode
Beam energy 15 keV
" Centered, angled and tangential NB injection
! BeamTostalipmoewderaint mneiudt-rpalsa ne to reduce10p+laMsWm a shape
V |Vn|2 φ
Biasing
! growth of the n=2 rotational !
mode.
65.5
87.8
91.4
Gas fill
Bias, RMF, PI
MR caps
time (μs)
0.8 •
0.06
Experimental observations
NBI
Experimental Observation
hg20150827.tae.2b
Radius (m)
hg20150803.tae.1b
γ/γMHD
1.0 0.8 0.6 0.4 0.2
range of 15o–25o
! Injection in ion-diamagnetic direction to drive current
!
faster spin-up; instability of n=1 tilt and subsequent
1-4
mode
stable
S. Divertor
Electrodes
0 -10
Plasma gun
S. Formation
DC-magnets
Con nement
NB injection
N. Formation
N. Divertor
Electrodes
10
Plasma gun
# of injectors 6
All n =
resistivity, S ~ 1500
Similar to Er < 0 end biasing
for
0.6 0.4 0.2
•
-5
Mirror plug
0
Axial distance (m)
5
Mirror plug
! Increases core heating
! Beam pressure of ~ 50% of total pressure
E/S*
! 0-D global power-balance analysis indicates substantial improvements in equilibrium and transport parameters
! Regression gives electron energy confinement time, τE,e ~Te1.8; more heating power, better confinement
cloud Formation
Scrape-o layer
FRC
Separatrix
Improvements in Confinement / Transport
Beam divergence < 28 mrad
FRC Correlates with NB Duration
! Key plasmIoan cpuarrreantmpertseorusrcme aintained un14t5ilAe nd of NB duration
! Diamagnetism persists ~1.5–2.5 ms after NB termination due to accumulated fast ions
Source: Thermal Ion CX from NBI Neutrals
• DEGAS2 Monte Carlo simulating the neutral beam injection
• 15keV beams are trapped primarily by charge exchange => Leaves behind warm ~ Ti neutral
Institutions
UCI
PPPL
GDT
UCLA
U. Texas
U. Wisconsin
U. New Hampshire Far-Tech
CompX
Trinum Research LBL
Kyoto U
RIKEN
Nihon U Swarthmore
Global energy confinement time in C-2/C-2U
Bayes Theorem: Finds a probability distribution (posterior) assembling
all solutions “I”
Gaussian processes:
Derive posterior P(I|D) assuming that likelihood P(D|I) and prior P(I) can be described by multivariate Gaussian distributions
J. Romero
Stability FPIC
FTC HYPERS
Electron energy confinement time vs. temperature
[2] M.W. Binderbauer et. al, Phys. Rev. Lett 105, 045003 (2010)
[3] T. D. Arber et al., Plasma Physics and Controlled Fusion 57,11(2015)
[5] E. Belova et al, Physics of Plasmas 11, 2523 (2004)
impact
! Simulations suggest optimized injection angle in
t / tA End-shorting:
Biasing:
A
E = 3.27
E = 4.52 exp(-3 E/S*)
Pulse duration 8 ms flat-top " High current at low beam energy
! CHERS measurements (Osin) show V ~60km/s after about 300μs
S. Dettrick , F. Ceccherini and L. Galeotti
! Reduces peripheral fast-ion losses Beam radial e-fold. size
< 10 cm
φ
0
0.1
0.2
0.3
0.4
0.5
0.6
! Enhanced neutron production Whole Device Modeling
H(fast,warm,andcoldcomponents),H2,andH2 Density(Rconf:1.0,t:3.0ms)
Presenter: Erik Granstedt
Priviledged and Confidential
13/29 compatible with both measurements “D” and prior assumptions
+
Neutral Beam Injection Neutrals
=> Fast ions charge exchange on warm neutral cloud
Funding Source
• • •
DEGAS2 study of Neutral H, H2, and H2+ densities due to beams Fast neutrals, warm neutrals, recycling, gas bleed
Wall recycling and PMI is included
Tri Alpha SciDAC Older DOE
Equilibrium
LReq FTC HyEq
Lamy Ridge Cygnus HYPERS
Heating
GENRAY RF Pisa
MC
Mag. Pump.
Fueling DEGAS2
Baldur HYPERS
If it “Quacks” Like an FRC, it Probability is an FRC
Global Transport Q1D / Q2D
*Other
Transport GTC ANC
KSOL STELLA CQL3D-CT Chicago DEGAS2 Neural Net
**This research used resources of the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC05-00OR22725. ++This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
[1] M.W. Binderbauer et al, Phys. Plasmas, 22(5), 56110 (2015). [4] C. Steinhauer, Physics of Plasmas 19, 070501 (2011)