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Ion acceleration by beating electrostatic waves
Edgar Choueiri
Electric Propulsion and Plasma Dynamics LabPrinceton University
Seminar at the Michigan Institute for Plasma Science and EngineeringThe University of Michigan
November 17, 2010
Acknowledgements
Ben Jorns (GS)Slava Spektor (GS)
Avi Ziskind (UG, Physics)Julia Ling (UG, Physics)
Buddy Gardineer (UG, MAE)
Bob Sorenson (Tech Staff)
Supported by AFOSR, DOE, NSF and NASA
Can nature inspire us a new plasma propulsion concept?
Why is it promising?
Under what conditions can it occur?
How does it work?
Can it be replicated in the lab?
Can nature inspire us a new plasma propulsion concept?
B
0.3 eVOxygen ions
10 eVOxygen ions
ES Waves
Bz = const
y
z
x
E,v
€
˙ ̇ x +ωci2 x =
qm
Ei cos(kix −ω it)i∑
θ
Bz = const
y
z
x
q, m
rL
Ion Acceleration by ES Waves
Bz = const
y
z
x
E,v
Ion Acceleration by ES Waves
Bz = const
y
z
x
E,v
Ion Acceleration by ES Waves
Bz = const
y
z
x
E,v
Ion Acceleration by ES Waves
Bz = const
y
z
x
E,v
Ion Acceleration by ES Waves
Two Beating waves: ω1-ω2=nωc
y
z
x
Why is it promising?
y
z
x
Two Beating waves: ω1-ω2=nωc
vv
f(v)
ω/k
Δv
vv
f(v)
ω/kv
Δv
BEW
SEW
Under what conditions can it occur?
200
150
100
50
0
Ion
Vel
ocity
500040003000200010000Time
ε = 49
ε = 50
No
Does it always occur?
Are there Necessary and Sufficient Criteria for Acceleration?
yesSpektor & Choueiri, Physical Review E, March 2004
aaa
PPDyL
Approach
Hamiltonian
Numerical Solution:Symplectic IntegrationAlgorithm
J. Comp. Phys. 92 230 (1991) Analytical Solution:
2nd order perturbation theory + Lie transformations
Phys. Plasmas 3(5), May 1996, 1545
Poincare surface of section (Reduced phase space diagram)
∑ −+=i
iii
iH )sincos(2
2
τνθρκκερ
time
ρ,θ
ρ0,θ0
200
150
100
50
0
Ion V
elocit
y
500040003000200010000Time
ε = 49
ε = 50
60
50
40
30
20
10
0
ρ
6543210θ
ε = 50
Poincare Cross Section
Numerical Simulation 2nd-order Perturbation Theory
Spektor & Choueiri, Physical Review, E, 69(4):Article No. 046402, 2004.
Can it be replicated/verified in the lab?
Transverse Helmholtz Antenna
Transverse Helmholtz antennaAntenna carriage
Configuration Transverse Helmholtz*
Power Supply 100W ENI
Matching circuit None
Frequency 1.92fci
Max RMS Field 15 G
€
ω 2 =ω ci2 + k 2 Te
m
ParametersParameters
RF Power 250 W (13.56 MHz)
Mag. Field (B) 500 G
fci 19 kHz
PB ~1 mT Argon
Ti 0.09 eV
PA 30 W
ne 1011 cm-3
Plasma Characterization
Dispersion Relation
!
"zTeTe
ri <<1
!
"zTeTe
# <<1!
"rTeTe
ri <<1
!
"rTeTe
# <<1
Plasma is uniform
Laser Induced Fluorescence System
Ar II transition
668.6130nm
4p4D05/2
4s4P3/23d4F7/2
442.72nm
Ion Heating in BWX II
MAXIMUM HEATINGMAXIMUM HEATING
SEW 55 ± 12%
BEW 90 ± 17%
BEW is unambiguously superior
Possibility of improving result
9/2010
Karney
1976
S3-3
1978 1998
Benisti et. al
2004
2006 2009 2010
BEW Heating
2010
Directed ion acceleration
Spektor and Choueiri.
Geometry: magnetic slope
Field magnitude
Geometry of system 2δ
BEW in a magnetic slope
BEW in a magnetic slope
1. Guiding centers move toward magnetic null
BEW in a magnetic slope
1. Guiding centers move toward magnetic null
2. Larmor radius increases
BEW in a magnetic slope
1. Guiding centers move toward magnetic null
2. Larmor radius increases
3. Trajectories pushed into magnetic slope
Thruster Proof of Concept
*Kline, Scime. Physics of Plasma, Dec. 1999
Antenna
Electrodes
Exhaust
BEW
€
j
Front View
Karney
1976
S3-3
1978 1998
Benisti et. al
2004
2006 2009 2010
BEW Heating
2010
Directed ion acceleration
Spektor and Choueiri.
Conclusions