coming attractions this is the first of five related presentations: graphite chamber issues and...

Coming attractions

•This is the first of five related presentations:

•Graphite Chamber Issues and trade-offs (Haynes)

•CONDOR: a flock of badgers (Moses)

•W armored ODS designs (Blanchard)

•How UW will support HAPL 3 year plan (Kulcinski)

•Validation of wall response models (Peterson (tomorrow))

•This is the first of five related presentations:

•Graphite Chamber Issues and trade-offs (Haynes)

•CONDOR: a flock of badgers (Moses)

•W armored ODS designs (Blanchard)

•How UW will support HAPL 3 year plan (Kulcinski)

•Validation of wall response models (Peterson (tomorrow))

Responseof

Dry Wall Graphite Chamber Designsto the

Output Spectrumfrom a

Directly Driven Laser IFE Target

Donald A. Haynes, Jr. and Robert R. Peterson§

Fusion Technology Institute

University of Wisconsin

and the High Average Power Laser HAPL team

§Currently X-1, LANL

Inertial Confinement Fusion is a proven method of achieving gain.

“A joint Los Alamos/LLNL program using underground nuclear

experiments, called HALITE at LLNL and Centurion at Los Alamos

(collectively called H/C) demonstrated excellent performance, putting to rest

fundamental questions about the feasibility of achieving high gain.”

(John D. Lindl, Inertial Confinement Fusion (AIP Press, Springer-Verlag,

New York 1998) p.12)

It is, however, still to be demonstrated that the wide gap between ICF and

IFE can be bridged.

“A joint Los Alamos/LLNL program using underground nuclear

experiments, called HALITE at LLNL and Centurion at Los Alamos

(collectively called H/C) demonstrated excellent performance, putting to rest

fundamental questions about the feasibility of achieving high gain.”

(John D. Lindl, Inertial Confinement Fusion (AIP Press, Springer-Verlag,

New York 1998) p.12)

It is, however, still to be demonstrated that the wide gap between ICF and

IFE can be bridged.

1 CH + 300 Å Au

DT Vapor

DT Fuel

Foam + DT

1.875 mm

2.1125 mm

2.43973 mm

Radiatively-smoothed direct drive laser target

Radiation SmoothedDirect Drive KrF Laser

(NRL) 353MJ

n

ions

xrays

c.p.

Chamber Physics Critical Issues Involve Target Output, Gas Behavior and First Wall Response

Design,Fabrication,

Output Simulations,(Output Experiments)

Design,Fabrication,

Output Simulations,(Output Experiments)

Gas Opacities,Radiation Transport,

Rad-Hydro Simulations

Gas Opacities,Radiation Transport,

Rad-Hydro Simulations

Wall Properties,Neutron Damage,

Near-Vapor Behavior,Thermal Stresses

Wall Properties,Neutron Damage,

Near-Vapor Behavior,Thermal Stresses

X-rays,Ion Debris,Neutrons

Thermal Radiation,

Shock

Target Output Gas Behavior Wall Response

UW uses the BUCKY 1-D Radiation-Hydrodynamics Code to Simulate Target, Gas Behavior and Wall Response.

See R. R. Peterson’s presentation for a report on validation experiments of

material response to xrays and ions.

A successful chamber design must simultaneously satisfy many constraints.

• Target injection– Heating– Tracking

• Driver injection• First wall survival: per shot

– no sublimation (graphite)– at most brief melting (W)

• First wall survival: long term– accumulation of ions– repeated thermomechanical stresses

*R.W. Petzoldt, D.T. Goodin, A. Nikroo, E. Stephens, N. Siegel, N.B. Alexander, A. R. Raffray, T.K. Mau, M. Tillack, F. Najmabadi, S. I. Krasheninnikov, R. Gallix, Direct drive target survival during injection in an inertial fusion energy power plant, Accepted for publication in Nuclear Fusion, Manuscript No. 7282 (2002).

General Atomics and UCSD are working to establish constraints on Xe density from target survival requirements.

N.B.:This is merely an

illustration of the constraint as understood

earlier this year.

At the threshold Xe density for vaporization of a graphite wall at 650cm from the PD_EOSOPA target (80mTorr), ion deposition

depth varies from 0.1 to 100 microns.

Ion Implantation Depth, 80mTorr, graphite wall at 650cm, 1000C, PD_EOSOPA Target

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E-05 1.E-04 1.E-03 1.E-02 1.E-01

Deposition Depth (cm)

Nu

mb

er

of

Ion

s/c

m^

2/s

ho

t

D

T

p

Pd

He (burn)

Problemsfor graphite ?

BUCKY simulations of chamber response allow the prediction of first wall surface temperature evolution.

• Roughly speaking, there are three peaks in the first wall temperature:

1) A response to the prompt, unattenuated x-rays hitting the wall (heating it practically volumetrically, in the case of a graphite first wall).

2) Response to soft xrays re-radiated after the Xe slows and captures the least penetrating ions.

3) Bursts of temperature rise as the unstopped ions strike the wall. This effect is somewhat exaggerated in these simulations due to the coarse binning of the ion spectum.

Surface Temperature Evolution, 80mTorr Xe,

650cm radius graphite wall, PD_EOSOPA target

1000

1500

2000

2500

3000

3500

1.E-08 1.E-07 1.E-06 1.E-05

Time (s)

Su

rfac

e T

em

pe

ratu

re (

C)

1

2

3

For a fixed target output, there are several parameters which can be simultaneously varied to obtain a successful chamber design

N.B.-None of these knobs will strongly effect the number of ions getting implanted in the wall. Yield variation is approximated here by varying ion flux, not energy spectrum. In this approximation, ion implantation dominated lifetime is inversely proportional to yield.

Initial Temperature

600C

1000C

•354MJ

•25mTorr

•600C

•6.5m

•372 g/shot

Chamber Radius

6.5m

13m

•354MJ

•25mTorr

•1000C

•8.1m

•0 g/shot

Xe Density

10mTorr

1 Torr

•354MJ

•80mTorr

•1000C

•6.5m

•0 g/shot

Gas

Kr

•Kr requires ~10% more density to achieve same protection as Xe.

•He requires ~1000% more density to achieve same protection as Xe.

•Molecular gases are under consideration.

He

Xe

Yield

160MJ 400MJ

•173.5MJ

•25mTorr

•1000C

•6.5m

•0 g/shot

To a very close approximation, temperature rise is independent of initial temperature.

Effect of initial temperature on surface temperature evolution650cm radius Graphite Chamber, NRL353, 80mTorr Xe

500

1000

1500

2000

2500

3000

3500

1.E-08 1.E-07 1.E-06 1.E-05

Time (s)

Sur

face

Tem

pera

ture

(C

)

T_0 = 600C

T_0 = 1000C

•The small differences arise from the temperature dependence of the thermal conductivity and the heat capacity.

•The output is discretized according to cycle.

Decreasing the Xe density leads to increased temperature rise at the surface of the first wall.

• For a 6.5m radius graphite chamber, lowering the wall temperature all the way to 600C does not lead to an acceptable design in terms of wall survival.

• Note: we deliberately use a conservative 15 bin coarse ion spectrum for both the low and high yield targets.

Peak Temperature Rise of Surface as a function of Xe density, 6.5m radius

NRL400, Graphite Wall, T0=600C

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0.00 0.05 0.10 0.15

Xe Density (Torr)

Tem

pera

ture

Ris

e (C

)

T vap artificially

raised to 10*nominal value for low Xe density cals. where there would otherwise be sublimation.

The effects of varying chamber radius have been studied for a lower (154MJ) yield version of this target at 10mTorr Xe. The partitioning and

spectra of the threat are close to that of the higher yield target.

X-rays Burn Ions Debris Ions

Gas Wall Gas Wall Gas Wall

550cm 0.19 2.14 0.18 17.6 6.73 18.41

600cm 0.20 2.12 0.19 17.5 7.07 18.06

650cm 0.22 2.11 0.20 17.9 7.43 18.14

Energy deposition (in MJ) as a function of radius and threat component

The debris ions are potentially the most immediately threatening, as they penetrate shallowly.

Deposition Depths (650cm, 10mTorr)

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

1.E+18

1.E+19

1.E+20

1.E+21

1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00

Depth

Num

ber

of d

epos

ited

ions

D (debris)

D (burn)

The effect of increased chamber radius aids chamber survival at the cost of pre-shot time spent in the

chamber

Effect of radius on wall surface temperature25mTorr Xe, graphite wall

0

500

1000

1500

2000

2500

3000

0.E+00 2.E-06 4.E-06 6.E-06 8.E-06 1.E-05

Time (s)

Tem

pera

ture

(C

)

Radius = 8.25m

Radius = 10m

•Two advantages are gained:

•Increased surface area

•Increased time of flight spreading

•Two disadvantages are increased:

•Target heating during injection

•Target tracking

•Radius increasing ad absurdum: Towards the “big dumb chamber”?

Alternate protective gases such as He have been considered. He, with only two electrons, is a very poor alternative on a per atom basis.

•80mTorr of Xe (not 25mTorr) is required to prevent first wall vaporization for a graphite wall at 6.5m from the threat of the high yield directly driven laser IFE target.

•883mTorr of He is required to afford similar protection.

•Neither amount prevents the possibly deleterious implantation of H and He burn products.

•80mTorr of Xe (not 25mTorr) is required to prevent first wall vaporization for a graphite wall at 6.5m from the threat of the high yield directly driven laser IFE target.

•883mTorr of He is required to afford similar protection.

•Neither amount prevents the possibly deleterious implantation of H and He burn products.

He provides substantially less first wall protection than does Xe for a given density (883mTorr) of gas

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

1.00E-08 1.00E-07 1.00E-06 1.00E-05 1.00E-04

Time (ns)

Fir

st

wa

ll s

urf

ac

e t

em

pe

ratu

re (

C)

Xe

He

Graphite 6.5m radius first wall response to the target output

from the high yield directly driven laser target.

He does have some attractive characteristics, e.g.:

•Very low non-linear index of refraction.

•Simple EOS/opacity calculation

•No cryo-plating on target.

Unbound electrons dominate ion stopping

3.54

E+

13

7.08

E+

13

1.42

E+

14

2.83

E+

14

5.66

E+

14

1.13

E+

15

2.26

E+

15

4.53

E+

15

9.06

E+

15

1.81

E+

16

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14

Thickness vaporized (A)

Density (atoms/cc)

Temperature (eV)

Graphite Wall, Radius = 4.5m

3-4

2-3

1-2

0-1

3.5

4E

+1

3

7.0

8E

+1

3

1.4

2E

+1

4

2.8

3E

+1

4

5.6

6E

+1

4

1.1

3E

+1

5

2.2

6E

+1

5

4.5

3E

+1

5

9.0

6E

+1

5

1.8

1E

+1

6 0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14


Density (atoms/cc)

Temperature (eV)


3-4

2-3

1-2

0-1

3.54

E+

13

7.08

E+

13

1.42

E+

14

2.83

E+

14

5.66

E+

14

1.13

E+

15

2.26

E+

15

4.53

E+

15

9.06

E+

15

1.81

E+

16

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14


Density (atoms/cc)

Temperature (eV)Graphite Wall, Radius = 6.5m

3-4

2-3

1-2

0-1

3.5

4E

+1

3

7.0

8E

+1

3

1.4

2E

+1

4

2.8

3E

+1

4

5.6

6E

+1

4

1.1

3E

+1

5

2.2

6E

+1

5

4.5

3E

+1

5

9.0

6E

+1

5

1.8

1E

+1

6 0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14


Density (atoms/cc)

Temperature (eV)


3-4

2-3

1-2

0-1

3.5

4E

+1

3

7.0

8E

+1

3

1.4

2E

+1

4

2.8

3E

+1

4

5.6

6E

+1

4

1.1

3E

+1

5

2.2

6E

+1

5

4.5

3E

+1

5

9.0

6E

+1

5

1.8

1E

+1

6 0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14


Density (atoms/cc)

Temperature (eV)


3-4

2-3

1-2

0-1

3.5

4E

+1

3

7.0

8E

+1

3

1.4

2E

+1

4

2.8

3E

+1

4

5.6

6E

+1

4

1.1

3E

+1

5

2.2

6E

+1

5

4.5

3E

+1

5

9.0

6E

+1

5

1.8

1E

+1

6 0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14


Density (atoms/cc)

Temperature (eV)


3-4

2-3

1-2

0-1

3.5

4E

+1

3

7.0

8E

+1

3

1.4

2E

+1

4

2.8

3E

+1

4

5.6

6E

+1

4

1.1

3E

+1

5

2.2

6E

+1

5

4.5

3E

+1

5

9.0

6E

+1

5

1.8

1E

+1

6 0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14


Density (atoms/cc)

Temperature (eV)


3-4

2-3

1-2

0-1

3.5

4E+13

7.0

8E+13

1.4

2E+14

2.8

3E+14

5.6

6E+14

1.1

3E+15

2.2

6E+15

4.5

3E+15

9.0

6E+15

1.8

1E+16

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14


Density (atoms/cc)

Temperature (eV)

Graphite Wall, radius = 11.5m

3-4

2-3

1-2

0-1

3.5

4E

+1

3

7.0

8E

+1

3

1.4

2E

+1

4

2.8

3E

+1

4

5.6

6E

+1

4

1.1

3E

+1

5

2.2

6E

+1

5

4.5

3E

+1

5

9.0

6E

+1

5

1.8

1E

+1

6

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14


Density (atoms/cc)

Temperature (eV)


3-4

2-3

1-2

0-1

A scan through radius, temperature, and density space has defined the per shot evaporation operating window

for graphite chambers and the high yield target.

These 900 results were produced over a weekend.

Conclusions•80mTorr of Xe (not 25mTorr) is required to prevent first wall vaporization for a graphite wall at 6.5m from the threat of the high yield radiatively smoothed target from NRL.

•This combination of Xe density and chamber radius is not acceptable from the point of view of target survival during injection.

•Increasing the chamber radius above 8m and keeping the Xe fixed at 25mTorr avoids vaporization, and would be on the margin of acceptable target heating if the afterglow problem can be solved.

•Because ion energy deposition in the chamber plasma depends strongly on electron density, the buffer gas should have many electrons per particle which contributes to target heating. Thus, He is a poor choice from this point of view.

•Ion implantation occurs up to remarkably high densities, with the He4 from the burn of the target requiring the most gas to prevent implantation.

•For the high yield target considered, a workable graphite wall design seems near at hand, by increasing the radius slightly and decreasing the target yield slightly.

•80mTorr of Xe (not 25mTorr) is required to prevent first wall vaporization for a graphite wall at 6.5m from the threat of the high yield radiatively smoothed target from NRL.

•This combination of Xe density and chamber radius is not acceptable from the point of view of target survival during injection.

•Increasing the chamber radius above 8m and keeping the Xe fixed at 25mTorr avoids vaporization, and would be on the margin of acceptable target heating if the afterglow problem can be solved.

•Because ion energy deposition in the chamber plasma depends strongly on electron density, the buffer gas should have many electrons per particle which contributes to target heating. Thus, He is a poor choice from this point of view.

•Ion implantation occurs up to remarkably high densities, with the He4 from the burn of the target requiring the most gas to prevent implantation.

•For the high yield target considered, a workable graphite wall design seems near at hand, by increasing the radius slightly and decreasing the target yield slightly.

BACKUPSLIDES

The threat spectrum can be thought of as arising from three contributions: fast x-rays, unstopped ions, and re-radiated x-rays

Some debris ions and x-rays are deposited in chamber gas, which re-radiates the energy in the form of soft

x-rays

The x-rays directly released by the target are, for Xe at the pressures contemplated for the DD target, almost all absorbed by the wall.

Some debris ions are absorbed directly in the wall.

The wall (or armor) reacts to these insults in a

manner determined by it’s material

properties (X-ray and ion

stopping lengths, thermal

conductivities and heat capacity)

Chamber Design is Driven by Target Output

Radiation SmoothedDirect Drive KrF Laser

(NRL) 353MJ

n

ions

xrays

c.p.

Output spectrum from R. R. Peterson, UW

The x-ray component of this directly driven target is fairly benign: only 2.7MJ, and mostly above 30keV.

DD 2.7MJ

0.00

0.20

0.40

0.60

0.80

1.00

1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Photon Energy (keV)

Spe

ctru

m (

peak

nor

mal

ized

)

DD 2.7MJ

X-ray energy percentiles

0%10%

20%30%40%50%

60%70%80%

90%100%

1.E-02 1.E+00 1.E+02 1.E+04

Photon Energy (keV)

Fra

cti

on

of

tota

l x-r

ay

en

erg

y

be

low

DD

X-ray Attenuation Lengths (NIST)

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

0.01 0.1 1 10 100

Energy (keV)

Atte

nuat

ion

leng

th (c

m) C

W

Three of the four BUCKY results, and Perkin’s calculation, all show a that significant fraction of the ion threat comes from He4 fusion products..

Au EOSOPA Au IONMIX Pd EOSOPA Pd IONMIX

Yield (MJ) 281.1

(99.0 %)

353.1

(99.2 %)

353.7

(99.2 %)

355.7

(99.2 %)

Neutron (MJ) 209.6

(73.8 %)

257.0

(72.2 %)

256.7

(72.0 %)

260.1

(72.5 %)

X-ray (MJ) 4.94

(1.74 %)

2.66

(0.75 %)

2.68

(0.75 %)

2.71

(0.76 %)

Target Debris (MJ) 68.4

(24.8 %)

74.6

(21.0 %)

78.1

(21.9 %)

68.4

(19.1 %)

Charged Fusion Product (MJ) 1.08

(0.38 %)

21.7

(6.1%)

19.1

(5.4 %)

20.9

(5.8 %)

NRL(Au)EOSOPA 281MJ

n

ions

xrays

c.p.

NRL(Au)IONMIX 353MJ

n

ions

xrays

c.p.

NRL(Pd)EOSOPA 354MJ

n

ions

xrays

c.p.

NRL(Pd)IONMIX 356MJ

n

ions

xrays

c.p.

Results from RRP, last meeting

The dominant threat to first wall survival arising from this target are the ions.

Ion Energy (eV)

#o

fIo

ns

103 104 105 106 107

1016

1017

1018

1019 DTHCPdHeHe - burn

Pd Layered TargetEOSOPA

BUCKY Ion Output LASNEX Burn Ion Output7E19,1.7MeV

He4

Ion # Total Energy (MJ) Average Energy (keV) Energy/amu (keV)

q/m

He4 (debris) 2.2E20 6 179 45 0.5

He4 (burn) 6.9E19 19.1 1700 425 0.5

Pd 6.1E17 2.6 27000 255 0.43

T 8.9E20 39 275 92 0.33

D 8.9E20 26 183 92 0.5

p 1.4E19 0.3 135 135 1

C 1.4E19 3.7 135 11.25 0.5

BUCKY is a Flexible 1-D Lagrangian Radiation-Hydrodynamics Code:Used to model implosion, burn, target output, blast wave propagation, and first wall heating,

vaporization and re-condensation

• 1-D Lagrangian MHD (spherical, cylindrical or slab).• Thermal conduction with diffusion.• Applied electrical current with magnetic field and pressure calculation.• Radiation transport with multi-group flux-limited diffusion, method of short characteristics, and variable

Eddington.• Non-LTE CRE line transport.• Opacities and equations of state from EOSOPA, IONMIX or SESAME.• Equilibrium electrical conductivities• Thermonuclear burn (DT,DD,DHe3) with in-flight reactions.• Fusion product transport; time-dependent charged particle tracking, neutron energy deposition.• Applied energy sources: time and energy dependent ions, electrons, x-rays and lasers with recently

introduced ray tracing package.• Moderate energy density physics: melting, vaporization, and thermal conduction in solids and liquids.• Benchmarking: x-ray burn-through and shock experiments on Nova and Omega, x-ray vaporization,

RHEPP melting and vaporization, PBFA-II K emission, …• Platforms: UNIX, PC, MAC

To quickly scan through parameter space, a cycle sharing CONDOR flock has been used at UW-CAE

1.00

E-0

3

4.01

E-0

3

1.60

E-0

2

6.38

E-0

2

2.56

E-0

1 307.05539.13

771.211003.29

1235.37

0

100

200

300

400

500

600

700

800

900

1000

Mass vaporized (g)

Xe density (Torr)

Initial Temperature (C)

Mass vaporized per shot

CONDOR implementation by Milad Fatenejad, details and refinement to be presented at upcoming HAPL meeting.

At a Xe density sufficient to prevent first wall vaporization (graphite, 6.5m, 1000C), Pd, He, T, and D ions implant in the wall.

Ion Implantation per shot: 88mTorr Xe, 650cm radius, 1000CPd_EOSOPA Target

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05

Ion Energy (keV)

Num

ber

of im

plan

ted

ions

/cm

^2

He4

Pd

T

D

5Hz = 1.8E4/hr, 4.32E5/day, 1.3E7/month, 1.6E8/year5Hz = 1.8E4/hr, 4.32E5/day, 1.3E7/month, 1.6E8/year

Blisteringfor metals

Different ions range out at different Xe densities.

Xe Density required to prevent ion implantation, PD_EOSOPA target, 650cm Radius Chamber, 1000C

0 250 500 750 1000

C

p

D

T

Pd

He

Ion

Sp

eci

es

Xe Density (mTorr)

Definite implantation

Possible Implantation

coming attractions this is the first of five related presentations: graphite chamber issues and...

Documents