Centrifugal Confinement for Fusion and the Maryland Experiment (MCX) R. F. Ellis, A. B. Hassam A. Case, D. Gupta, Y. Huang, J. Rodgers, C. Romero-Talamas, C. Teodorescu, A. DeSilva, R. Elton, H. Griem, P. Guzdar, R. Clary, S. Choi, R. Lunsford, A. S. Messer, R. Reid, G. Swan, I. Uzun-Kaymak, W. C. Young University of Maryland, College Park PPPL 2017
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Centrifugal Confinement for Fusion
and the Maryland Experiment (MCX)
R. F. Ellis, A. B. Hassam
A. Case, D. Gupta, Y. Huang, J. Rodgers, C. Romero-Talamas, C. Teodorescu,
A. DeSilva, R. Elton, H. Griem, P. Guzdar, R. Clary, S. Choi, R. Lunsford,
A. S. Messer, R. Reid, G. Swan, I. Uzun-Kaymak, W. C. Young
• Centrifugal axial confinement, loss-cone capped, midplane to mirror density
drops
• Neutral dominated
UNANSWERED QUESTIONS
• How large, compared to classical, is the residual transport?
Is it interchange modes, or other?
• Is there a speed barrier (CIV)? Can it be exceeded?
• Insulators at fusion conditions. > 10 MV/m?
• Run without core?
• Opportunity: High-Tc High-B magnets
References (partial list)
1) Sub-Alfvenic velocity limits in magnetohydrodynamic rotating plasmas. Physics of Plasmas 17 052503 (2010)
C. Teodorescu, R. Clary, R. F. Ellis, A.B. Hassam, C. A. Romero-Talamas and W.C. Young.
2) Low Dimensional Model for the Fluctuations observed in the Maryland Centrifugal Excperiment. International Symposium of
Waves, Coherent Structures and Turbulence in Plasmas, 2010 American Institute of Physics 978-0-7354-0865-4/10
P.N.Guzdar, I. Uzun-Kaymak, A.B.Hassam, C. Teodorescu, R.F. Ellis, R.Clary, C.Romero-Talamas, and W. Young
3) Isorotation and differential rotation in a magnetic mirror with imposed ExB rotation. Physics of Plasmas 19, 072501 (2012).
C.A. Romero-Talamas, R.C. Elton, W.C. Young, R. Reid and R.F. Ellis.
4) Experimental study on the velocity limits of magnetized rotating plasmas. Physics of Plasmas 15 042504 (2008). C.
Teodorescu, R. Clary, R.F. Ellis, A.B. Hassam, R. Lunsford
5) Diamagnetism of rotating plasma. W.C. Young, A.B. Hassam, C.A. Romero-Talamas, R.F.Ellis and C. Teodorescu.
Physics of Plasmas 18, 112505 (2011)
6) Analysis and modeling of edge fluctuations and transport mechanism in the Maryland Centrifugal Experiment. I.U.Uzun-
Kaymak, P.N. Guzdar, R. Clary, R.F.Ellis, A.B. Hassam and C. Teodorescu. Physics of Plasmas 15, 112308 (2008)
7) 100 eV electron temperatures in the Maryland centrifugal experiment observed using electron Bernstein emission. R.R. Reid,
C.A. Romero-Talamas, W.C.Young, R.F.Ellis, and A.B.Hassam. Physics of Plasmas 21, 063305 (2014)
8) Confinement of Plasma along Shaped Open Magnetic Fields from the Centrifugal Force of Supersonic Plasma Rotation. C.
Teodorescu, W.C.Young, G.W. Swan, R.F.Ellis, A.B.Hassam, and C.A.ROmero-Talamas. Phys. Rev. Lett. 105, 085003 (2010)
9) Charge and mass considerations for plasma velocity measurements in rotating plasmas. C.A. Romero-Talamas, R.C.Elton, W.C.
Young, R. Reid, R.F.Ellis, A.B. Hassam. Journal of Fusion Energy, 29, 6, 543-547 (2010)
Extras
Magnetic probes could yield info
on wobbles at the edge
p + BB/0 0 p ~ p’ r r/a ~ BB/0p => r < 1 cm
There is a speed barrier at VA as expected,
but also another non-MHD barrier
40
60
80
100
120
140
160
40 80 120 160 200 240 280 320
Alfven velocity (km/s)
rota
tion
ve
locity (
km
/s)
• Consistent with “Critical Ionization Velocity” observed earlier
MA 1 in all 142 distinct data points
Rotation velocity measured
at maximum Vp.
Average values:
1/ 2( )
150 μs
p
A
i i
Vu
aB
BV
m n
Insulator long path length, clean after ~10 years
Lithium
Larger cross section
Flare out the fields at the ends
Stellarator – Mirror
Ellis, Gupta, Hassam, J. Rodgers, Teodorescu
CIV spectroscopy shows supersonic
rotation in red and blue shifts
Bottom
mcx030519-24
mcx030519-23
mcx030519-26
Top
mcx030519-16
mcx030519-17
mcx030519-18
Confirmation of
crossfield MHD dielectric constant
0
0.5
1
1.5
2
2.5
3
0 20 40 60 80 100
ne (1019
m-3
)
Cp (
10
-4 F
)
0
20
40
60
80
100
nm
ode
l (1
019 m
-3)
Teodorescu et al (PoP)
= nMc2/B2
interferometer
Q/V
momentum ~ 200-600 s
=> N 1017 m-3
Calculated timescales for comparison to MCX
discharge duration (> 5 ms) and momentum
confinement time( 200 s)
Axial Alfven time ~ LP/vA
5s
Period of rotation ~ (2pR/u)
10s
Interchange growth time ~ [(aPLP)/(T/Mp)]1/2
10s
Axial electron heat conduction time ~ (LP/)2 e
30s
Axial sonic time ~ LP/(T/Mp)1/2
30s
Electron-ion heat exchange time ~ (Mp/me)e
40s
Classical viscous damping time ~ (aP/)2 ii
8000s
( n = 2x1020 m-3, T = 30 eV, B = 0.2 T)
Charge exchange time ~ 500 s
OPERATION AT FUSION
PARAMETERS
This is an old slide; I would have to check the assumptions that went into it. Definitely includes parallel Pastukov electron losses (enhanced by Ms). Probably a mirror ratio of 10-12 is assumed. “Q” is the factor by which n*tau at T=10kV is greater than the Lawson Criterion.
0-D Transport Model
nMu2/mom = Pin
3nT/heat = Pin - Prad
1/ mom = 1/ perp,i
1/ heat = 1/ perp,i + 1/ e
• Scales to reactor (u < VA, classical, Rm=4):
n=.6 1020, B=2.6T, a=1.1m, Pin=3MW
=> T=13keV, Ms=6, Pfusion=240MW
BPX and Reactor Scenarios:
Magnetic field is the key parameter
BPX Reactor
a (m) 1.2 1.1
B (T) 0.9 2.5
n (1020 /m3) 0.1 0.6
L/a 20 10
R/a 4 4
T (kV) 10 13
Ms 6 6
Q 8 70
PDT 4 250
1/MA 1.1 1.1
E 3 10
Measured plasma capacitance dependence on
plasma density agrees very well with MHD theory
0.00E+00
5.00E-05
1.00E-04
1.50E-04
2.00E-04
2.50E-04
3.00E-04
0 20 40 60 80 100
ne (1019
m-3
)
Cp (
F)
Circuit model yields an accurate measure of plasma
density
Theory
CP
Interferometer Density (1019 cm-3)
0-D Plasma Model
(1/2)CPVP2 = (1/2)u
2*VOL [energy stored in capacitor
= rotational kinetic energy]
CP = QP/VP [defines Cp]
u = VP/(aPB) [Vp and ap(plasma radial extent)
=> average ExB velocity, u]
Yields azimuthal speed, average density, momentum
confinement time.
Confirmed by Doppler spectroscopy, HeNe interferometer
To lowest order, MCX is a collisional, ideal MHD plasma
=> centrifugal confinement is the best explanation for x10 drops
• ~ 10cm << L => isotropic pressure, no loss cone physics
=> Braginskii equations
• ~ 0.2cm << a => Ideal MHD equations follow from Braginskii
=> B. p = - B.[nm u. u] to lowest order
• RHS = 0 => p( ) no pressure drop
• RHS from u|| (nozzle mirror losses) => Bernoulli => pressure drop ~ x2
• RHS from uExB => centrifugal stratification => pressure drop ~ exp[Ms2]
• RHS from CX friction (only non-Braginskii possibility)
=> plasma pressure drop only in neutral penetration layer <
10cm
Magnetic Flux Surfaces
Mirror Coil Low Field Coils
Z-pinch density profile approaches
laminarity with increasing Mach #
C1 is the laminar profile
(green).
C2-C6 are turbulent states
(blue) with respective
(turbulent) Mach numbers
0.3, 1.4, 2.2, 3.7, 4.8.
τCB vs. τFW
Edge dB/dt probes: fluctuations are consistent with