George H. Miley and colleagues in IEC groupDept. of Nuclear, Plasma, and Radiological

EngineeringUniversity of Illinois, Urbana, IL. 61801

Other presentations from UIUCHugo Leon et al on UIUC experimental facilitiesGuilherme Amadio, Ben Ulmen, et al. on plasma jet

Hope for help with proposed IEC monograph – Springer Verlag Scientific Press.

Scheduled next summer

Send any suggested inputs to me. Please cc Autumn West [ajwest85@gmail.com]

Coverage ◦ Theory◦ Experiments◦ applications

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

Theoretical studies of scale-up to power reactor◦ Potential well theory – cont’d of H-j Kim and H. Momota’s studies

Space thruster◦ 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 93524f

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;

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. TakeyamaUniversity of Illinois at Urbana-Champaign, Urbana, IL, 61801

G.H. Miley and P.J. ShresthaNPL 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 cmGrid 20 cm radius 2 cm x 1cm spacing

Stabilizing coil

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

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.

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),

keV, range

Wmax, [W] P, mm Hg T,K,

target

D+ energy

spread

*High Current

Accelerator

10-40 μA 100.0- 2.0 2.0 5*10-7,

vacuum

100-350 ± 1.0%

**Pulsed Glow

Discharge (PGD)

100-600

mA

2.5- 0.40 200.0 2.0-10.0, D2 200-2000 ±

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

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 KhanDepartment of Nuclear, Plasma, and Radiological Engineering,

University of Illinois, Urbana, 61801

25AiAA 2008

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.

26AiAA 2008

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 energy-transfer reaction:

O2(1∆) + I(2P3/2) ⇆ O2(3Σ) + I*(2P1/2)

27AiAA 2008

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

Operation times typically restricted by

formation of chemical by-products, eventually limit the production of SDO.

28AiAA 2008

Electron excitation and ionization cross sections for oxygen.

29AiAA 2008

30AiAA 2008

31AiAA 2008

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.

32AiAA 2008

Another way of viewing the CFND: analogy with dielectric barrier discharge (DBD or “silent discharge”).

The dielectric coating on one of the electrodes limits the charge in the micro-discharge channel.

The micro channel formation and discharge are random in time and to some extent in space.

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.

33AiAA 2008

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.

34AiAA 2008

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.

35AiAA 2008

36AiAA 2008

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.

Reaction analysis limited to ~12 key equations, although a more complete analysis with a large number of reactions could eventually be done.

37AiAA 2008

38AiAA 2008

39AiAA 2008

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%.

40AiAA 2008

350

400

450

500

550

600

650

700

0 20 40

Vo

lta

ge

(V

)

I (mA)

VI Curve 800 mTorr Vi Curve 600 mTorr

VI Curve 1200 mTorr VI Curve 500 mTorr

41AiAA 2008

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 non-equilibrium processes.

Initial experimental set up and computational model have been described which are being employed for continuing studies of CFND.

42AiAA 2008

DOE FF Hybrid WS Gaithersburg MD 9/09

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, Australia3Tsinghua University, Beijing, China4NPL Associates, Inc., Champaign, IL, USA

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

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

ICONE-10 April 2002, Arlington, Virginia

Flexible geometry offers new types of drive configurations ---

Fig. 1 Spherical IEC Device Fig. 2 Cylindrical IEC Device

Cylindrical IECs offer many advantages for the present sub-critical reactor system .

The prototype cylindrical IEC version , C-device, 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

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 spallation-target 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

1.00E+2

1.00E+3

1.00E+4

1.00E+5

1.00E+6

1.00E+7

1.00E+8

0 10000

20000

30000

40000

50000

60000

70000 Applied Voltage (V)

Sp

her

ica

l-E

qu

ival

ent

Ne

utr

on

Yie

ld

(Neu

tro

ns

/sec

on

d)

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

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.

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

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

DOE FF Hybrid WS Gaithersburg MD 9/09

1.E-15

1.E-14

1.E-13

1.E-12

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

0.5 0.6 0.7 0.8 0.9 1

k

P/S

(W/ n

eutro

n s

-1)

Water

Graphite

Figure 4 Power level per unit source (P/S) as a function as a function of k for two different moderators

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 accelerator-spallation 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-ChampaignUrbana, Illinois 61801

 *NPL Associates, Inc

912 W. Armory Ave., Champaign IL 61821

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.