George H. Miley and colleagues in IEC group
Dept. of Nuclear, Plasma, and Radiological
Engineering
University of Illinois, Urbana, IL. 61801
Other presentations from UIUC
Hugo Leon et al on UIUC experimental facilities
Guilherme Amadio, Ben Ulmen, et al. on plasma jet
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Hope for help with proposed IEC monograph
– Springer Verlag Scientific Press.
Scheduled next summer
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Send any suggested inputs to me. Please cc
Autumn West [ajwest85@gmail.com]
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Coverage
◦ Theory
◦ Experiments
◦ applications
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Continued work on neutron sources
IEC bombardment studies
◦ X-ray emission during high current ion bombardment
◦ Measurement of low energy cross sections and facing wall effects
◦ Controlled filament discharge concept
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Theoretical studies of scale-up to power reactor
◦ Potential well theory – cont’d of H-j Kim and H. Momota’s studies
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Space thruster
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Proton thrust technology
Jet thruster
dipole assisted IEC
Space ship I and II design studies
Plasma jet
◦ waste processor
◦ IEC driven fission research reactor (fusion-fission hybrid)
George H. Miley1*, Guilherme Amadio1, Ben
Ulman1, Hiromu Momota1, Linchun Wu1,
Michael Reilly1, Rodney Burton2, Vince
Teofilo3, Dick Dell4, Richard Dell4 and
William A. Hargus5
1Dept.
of Nuclear, Plasma and Radiological Engineering, U of
Illinois, Urbana, IL 61801;2Dept. of Aerospace Engineering, U
of Illinois, Urbana, IL 61801; 3Lockheed Martin Space Systems
Co., Advanced Technology Center, Palo Alto, CA 94304;
4Advanced Aerospace Resource Center (AARC), P.O. Box
97636, Raleigh, N.C. 27624, 5Air Force Research Laboratory,
Edwards AFB, CA 93524
f
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Novel plasma jet thruster, based on Inertial Electrostatic
Confinement (IEC) technology, -for ultra maneuverable - space
thruster for satellite and small probe thrust operations.
Electrical efficiency matches conventional plasma thrusters;
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design simplicity
reduced erosion giving long life timer
reduced propellant leakage losses
high power-to-weight ratio
Multiple jets ok for added control
Low gas leakage + good heat removal make it possible to scale
the design to low powers or high powers.
R. Thomas and Y. Takeyama
University of Illinois at Urbana-Champaign, Urbana, IL, 61801
G.H. Miley and P.J. Shrestha
NPL Associates Inc. 912 W. Armory, Champaign, IL, 61821
Coil Specs:
•12 gage of Sq. magnet wire (Copper)
•17 x 26 turns of coil
•Current Varies in the range of 0-20 A
•Max. field strength of 0.1 T
Coil
Inner radius = 2 cm
Outer radius = 8 cm
Height = 4 cm
Grid
20 cm radius
2 cm x 1cm spacing
Stabilizing coil
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Magnetic field increases the
electron density by a factor of
16.
Electron temperature decreases
in the presence of a magnetic
field
the discharge voltage decreases
in the presence of a magnetic
field
The magnetic coil can be used
to impose a potential in the
central plasma to control space
charge build up
Overall, the use of the dipole
provides improved ion beam
focusing, ion confinement, and
also appears to favorably affect
the discharge voltage
characteristics.
Uses IEC in low discharge mode for bombardment of
targets.
Experiments done in collaboration with A. Lipson at
Institute of Physics & Chem, Moscow AS, Russia
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Evaluation of DD and DT-reactions at the first wall surface of fusion
reactors like ITER neglect effects of non-linear processes during
high current, low energy bombardment.
Especially crucial as the concentrations of D and T atoms embedded
in the wall surface increases = a “target” for bombarding ions.
Conventional (free space) DD-reaction cross-sections predict the
DD-reactions are negligible at the low energies (≤2 keV) involved.
But, the free space approximation is not accurate for the conditions
involved.
The DD-reaction yield can be orders of magnitude higher than
predicted by extrapolation of the standard (free space) DD-reaction
cross-section to lower deuteron energies. These enhancement
(non-linear) effects came from a drastic increase in the deuteron
screening potential in the crystalline structure of the metal targets at
Ed ~ 1.0 keV, especially at a high deuteron current density where the
ion density in the target can become quite large.
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Nuclear reactions in astrophysical objects also
encounter screening conditions similar to this.
Consequently studies of metal targets
bombarded by low energy accelerators has been
strongly studied by groups such as the European
Astrophysical Lab (LUNA) [ while time integrated
yields become large (hence limiting wall
lifetimes), the instantaneous yields are low.
Thus the key to accurate measurements involves
using high current bombardment plus special
detectors such as CR-39 tracking foils to
measure charged particle emission during
bombardment.
Table 1
Comparison of High Current, Low Energy D Accelerator and Pulsed GD
Parameter
I, range
Ed(lab),
Wmax, [W]
P, mm Hg
keV, range
*High
Current
10-40 μA
100.0- 2.0
2.0
Accelerator
**Pulsed
5*10-7,
T,K,
D+ energy
target
spread
100-350
± 1.0%
200-2000
±
vacuum
Glow
Discharge (PGD)
100-600
2.5- 0.40
200.0
2.0-10.0, D2
mA
10.0%
*The accelerator uses a Duoplasmatron (Ed = 50 keV) ion source, decelerating system and magnetic focusing
installation ].
**Power supply given a periodic rectangular current pulse. The pulse duration can vary within 100 - 600 μs. The
distance between cathode and anode is varied between 4.0 and 6.0 mm.
AiAA 2008
20
3.0 MeV proton
yield detected by
11 m Al covered
CR-39 detectors
in deuterium GD
at the same
current and
different
accelerating
voltages: U1 =
805 V and U2 =
2175 V
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In accelerator measurements with the Ti-target at 2.5 < Ed < 10.0
keV, the deduced screening potential is Ue = 65  10 eV However,
for the PGD experiment, the screening potential is as large as
Us=620  140 eV
= enhancement in terms of DD-proton yield even at Ed=1.0 keV is
about nine orders of magnitude larger than that predicted with bare
(B&H) cross-section.
Illustrates how importance of higher deuteron/electron densities in
the target (due to the higher currents in the GD)
In addition to fusion plasma wall effects, these densities are also
representative of reactions in Astrophysical plasmas
George H. Miley, Hugo Leon, Atuna Khan
Department of Nuclear, Plasma, and Radiological Engineering,
University of Illinois, Urbana, 61801
AiAA 2008
25
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A new type of low E/N discharge, the Controlled
Filament Non-local Discharge (CFND), is described.
Unique cathode design with a “spiked” surface and
built-in ballast resistors, stabilize electron
filaments generated during pulsed operation.
Potential applications to the Electric Oil Laser and
various plasma processes such as ozone
production are discussed.
AiAA 2008
26
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Based on energy transfer from metastable O2 (1∆)
(SDO) to excite the I*(2P1/2) 1.31 μm I (2F3/2)
transition.
The SDO generated chemically ⇨transferred by
gas flow to a laser cell ⇨mixed with I2.
Results dissociation of I2 ⇨subsequent formation
of I*(2P1/2) by the fast near resonant energytransfer reaction:
O2(1∆) + I(2P3/2) ⇆ O2(3Σ) + I*(2P1/2)
AiAA 2008
27
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Chemical approach of the operation of a
chemical SDO generator suffers from several
factors:
↠Limitations to the generation of high SDO
density ↠Need for cooling
↠Involvement of corrosive materials
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Operation times typically restricted by
formation of chemical by-products,
eventually limit the production of SDO.
AiAA 2008
28
Electron excitation and ionization cross sections for
oxygen.
AiAA 2008
29
AiAA 2008
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AiAA 2008
31
The magnetic fields associated with the CFND consist of an
overall poloidal field around the entire discharge and individual
fields around each filament. This configuration is, in effect,
analogous to a wire cage Z-pinch plasma without physical wires.
AiAA 2008
32
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Another way of viewing the CFND: analogy with
dielectric barrier discharge (DBD or “silent discharge”).
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The dielectric coating on one of the electrodes limits the
charge in the micro-discharge channel.
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The micro channel formation and discharge are random
in time and to some extent in space.
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Estimated after initial breakdown at 600 V, an E/N of
10-16 Vcm2 is obtained at roughly atmospheric pressure
in oxygen with an applied voltage of 100 V in planar
electrode geometry at a spacing of ~10 cm.
AiAA 2008
33
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Stability of the CFND configuration is a crucial
issue relative to extended discharge times and
filament lengths.
Goal - to maintain stable filaments long enough
to provide significant non-equilibrium reaction
conditions. (e.g. efficient production of SDO in an oxygen
discharge)
CFND holds great promise for enhanced stability
⇨can be viewed as a plasma analogy of the famous Sandia
wire cage Z-pinch, currently producing world record x-ray
yields.
AiAA 2008
34
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A 1-D theoretical model has been
constructed with features very similar to that
used in earlier work by Eliasson et al. to very
successfully model trends in the DBD filament
discharge.
This model is used to compare trends in E/N
as a function of pressure, voltage, and
filament dimensions.
AiAA 2008
35
AiAA 2008
36
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Reactions that involve electrons must be
considered: positive ions O+, negative ions 0-, O; ground
states O(3P), 02(X3E,), O3(lA1) and excited states O('D), 02(a'A,),
OZ(b' X:), Oz(A 3E:), 02(B 3Z:), 02(v) and O: where 0:stands for a
vibrationally-excited O3 molecule.
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Reaction analysis limited to ~12 key
equations, although a more complete analysis
with a large number of reactions could
eventually be done.
AiAA 2008
37
AiAA 2008
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AiAA 2008
39
The 2.2 kVA power supply built by NPL employees is shown above. The
circuit board controlling the frequency operates between 100 Hz to
1800 Hz and the pulse width modulation operates with duty cycles from
5% to 95%.
AiAA 2008
40
700
Voltage (V)
650
600
550
500
450
400
350
0
20
40
I (mA)
VI Curve 800 mTorr
Vi Curve 600 mTorr
VI Curve 1200 mTorr
VI Curve 500 mTorr
AiAA 2008
41
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Non-local effects in CFND plasma discharges offer unique
opportunity to control the EED to enhance efficiency for excited
state production, light emission, and select chemical reactions.
A very important application of this type is SDO production.
CFND approach- extremely well suited to such operation
⇨ optimum E/N can be achieved in a relatively high pressure,
large volume plasma.
CNDF builds on prior use of filament type discharges for nonequilibrium processes.
Initial experimental set up and computational model have been
described which are being employed for continuing studies of
CFND.
AiAA 2008
42
Miley G. H., Thomas R., Takeyama Y., Wu L., Percel I., Momota H.,
Hora H2., Li X. Z3. and P. J. Shrestha4
1University
of Illinois, Urbana, IL, USA
2University of New South Wales, Sydney, NSW, Australia
3Tsinghua University, Beijing, China
4NPL Associates, Inc., Champaign, IL, USA
DOE FF Hybrid WS Gaithersburg
MD 9/09
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The IEC is already a commercial fusion neutron source at low
levels!!
◦ Replaced Cf-252 in neutron activation analysis at:
 Ore mines in Germany
 Coal mines in USA
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In these cases ease of licensing, long lived “target” (plasma),
on-off capability, simplicity of construction (low cost),
compactness, low maintenance requirement, flexibility in
neutron spectrum (2.54 or 14 MeV), ease of control gave the
IEC the “edge”. The features can carry over to a driver for a
hybrid.
Possibility of small size/power opens door to several near term
applications = university training and research facilities.
DOE FF Hybrid WS Gaithersburg
MD 9/09
Flexible geometry offers new types of
drive configurations ---
Fig. 1 Spherical IEC Device
ICONE-10 April 2002,
Arlington, Virginia
Fig. 2 Cylindrical IEC Device
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Cylindrical IECs offer many advantages for
the present sub-critical reactor system .
The prototype cylindrical IEC version , Cdevice, is a particularly attractive.
Deuterium (or D-T) beams in a hollow
cathode configuration give fusion along the
extended colliding beam volume in the
center of the device = a line-type neutron
source.
DOE FF Hybrid WS Gaithersburg
MD 9/09
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Accelerator approaches to date have used an accelerator
spallation-target system.
The large size and cost of the accelerator remain an
issue. Also, the in-core target system poses significant
design and engineering complications.
The IEC fits in fuel element openings of the sub-critical
core assembly. This provides a distributed source of
neutrons
Replaces both the accelerator system and spallationtarget by by multiple modular sources assembly.
Provides flexibility in core design and in flux profile
control.
Small IEC units can be produced at a lower cost than the
accelerator
DOE FF Hybrid WS Gaithersburg
MD 9/09
Spherical-Equivalent Neutron Yield
(Neutrons/second)
1.00E+8
1.00E+7
1.00E+6
10 mA equivalent MCP
20 mA equivalent MCP
40 mA equivalent MCP
80 mA equivalent MCP
10 mA, 4.3-cm Sperical
10 mA, 4.1-cm Spherical
20 mA, 4.1-cm Spherical
10 mA, 5-electrode C-device
20 mA, 5-electrode C-device
40 mA, 5-electrode C-device
1.00E+5
1.00E+4
1.00E+3
1.00E+2
0
1000
0
2000 3000 4000 5000
0 Applied
0
0
Voltage
(V) 0
6000
0
7000
0
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Present experiments give 10*10 DD n/s (10*12 DT
n/s at 90 kV and 20 mA.
Extrapolation to 10*14 n/s (prototype research
reactor goal) at 100 kV requires 0.3 A or 30 kW
input.
With improved potential profile control, might be
reduced to <10 kW.
Research focusing on power reduction.
Further extrapolation to higher power systems also
promising.
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Present experimental IEC devices are close to
neutron yields required of this application.
Calculations for a representative graphite
moderated subassembly next.
DOE FF Hybrid WS Gaithersburg
MD 9/09
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Figure presents the power obtained per unit source as a
function of the multiplication factor k∞.
assumed to be a cylindrical homogeneous reactor, fueled by
uranium dioxide.
The fuel enrichment is adjusted to give the desired value of
k∞.
the fraction of core volume occupied by the fuel fixed at 5%.
the graphite-moderated system can deliver 1 kW of power
with a source of 1012 neutrons/sec at Keff =0.99
Specifications summarized in Table .
DOE FF Hybrid WS Gaithersburg
MD 9/09
P/S (W/ neutron s-1)
1.E-07
1.E-08
1.E-09
1.E-10
Water
1.E-11
Graphite
1.E-12
1.E-13
1.E-14
1.E-15
0.5
0.6
0.7
0.8
0.9
1
k
Figure 4 Power level per unit source (P/S) as a function as a function of k
moderators
DOE FF Hybrid WS Gaithersburg
MD 9/09
for two different
Fuel
UO2 (0.5% U-235)
Moderator material
Graphite
Moderator volume fraction
95%
Multiplication factor
0.97
Radius (cm); Height (cm)
30;50
Source strength (neutrons/s) 1x1012
Power (kW)
1.2
DOE FF Hybrid WS Gaithersburg
MD 9/09
An alternative to the standard driven reactor acceleratorspallation target design is proposed which employs IEC neutron
sources which can be in a central location or distributed across
a number of fuel channels. Such a modular design has distinct
advantages in reduced driver costs, plus added flexibility in
optimizing neutron flux profiles in the core. The basic physics
for the IEC has been demonstrated in small-scale laboratory
experiments, but a scale-up in source strength is required for
ultimate power reactors.
The IEC source strength is already near the level required for low
power research reactors or for student sub-critical laboratory
devices. This application would be advantageous since the
safety advantages of these reactors should enable a next
generation of research reactors to be constructed quickly,
meeting the educational and research needs facing us as there
is a rebirth of interest in nuclear power.
DOE FF Hybrid WS Gaithersburg
MD 9/09
R.L. Burton, H. Momota,* N. Richardson, Y. Shaban
and G. H. Miley*
University of Illinois at Urbana-Champaign
Urbana, Illinois 61801
*NPL Associates, Inc
912 W. Armory Ave., Champaign IL 61821
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Fusion Ship II, is shown capable of roundtrips to
outer planets with times ~ 1 year, the design
goal.
Development issues include demonstration of a
gain of 9:1 or better. Other issues include R&D
on the Direct Energy Converters, design of
power conditioning, high powered density
NSTAR thrusters, and lightweight crew
shielding.
The 14.7 MeV proton flow (28.3 N) could be
used if mass is added to increase thrust. Then
the energy conversion system could be greatly
simplified. This will be studied in Fusion Ship
III.