threat spectra calculations for hapl chamber first wall

Threat Spectra Calculations for HAPL Chamber First Wall

Greg Moses, John Santarius, and Milad Fatenejad

HAPL Team Meeting

Princeton Plasma Physics Laboratory

October 27-28, 2004

JFS/GAM 2004 Fusion Technology Institute, University of Wisconsin 2

Progress on Three Modeling Issues

• Threat spectra target source computed by BUCKY. Fluid approximation not valid (TOFE ’04).

Hybrid fluid-kinetic approximation.

• Ion threat time of flight transport to first wall and deposition in wall computed by BUCKY. Temporal prediction of ion threat at the first surface in BUCKY

improved (piece-wise continuous model replaces discrete model.) Model verified.

• Chamber—first wall integrated calculation computed by BUCKY. Replace two region model with integrated e.o.s. and conductivity

models. Modifications completed.


30 32 34 36 38 40Timens0

5

10

15

20

enoZsuidarmm DT

vapor

DTice

CHDTmix

CH

Au

For the Examination of Long Mean Free Path Effects,

the Time Near Ignition Will Be the Focus

Lagrangian constant-mass zones from BUCKY run of HAPL case

• Ignition occurs at ~34.6 ns.


104 103 102 101 100

Radiuscm102

103

104

105

106

erutare

pme

TVe

Time 34.592 ns

Ti

Ti

Te Te

DTvapor

DTice

CHDTmix

CH

Au

104 103 102 101 100

Radiuscm107

105

103

101

101

103

ssaM

ytisne

dgmc3 Time 34.592 ns

DTvapor

DTice

CHDTmix

CH

Au

104 103 102 101 100

Radiuscm0

2 108

4 108

6 108

8 108

1 109

diul

Fytic

olevmcs

Time 34.592 ns

DTvapor

DTice

CHDTmix

CH

Au

• Each point represents a Lagrangian zone of constant mass.

DT Core, DT-CH Shock, and CH-Au ShockWill Exemplify the Issues

34.55 34.56 34.57 34.58 34.59 34.6Timens1015

1016

1017

1018

evitalu

mu

Cn

ortue

ndleiy

• Neutrons get produced within ~30 ps.

DT-CH

CH-Au

DT-Core


DTCore

rshock (cm) < 0.001

rshock (cm) < 0.001

vshock (cm/s) 6.6 x 106

ni (cm-3) 1.5 x 1026

Ti (keV) 276

Te (keV) 72

Ave. charge state 1

rshock / mfp > 1000

DTCore

DT-CHShock

rshock (cm) < 0.001 0.026

rshock (cm) < 0.001 0.02

vshock (cm/s) 6.6 x 106 5.5 x 108

ni (cm-3) 1.5 x 1026 5.1 x 1024

Ti (keV) 276 86

Te (keV) 72 47

Ave. charge state 1DT 1CH 1

rshock / mfp > 1000 1.1

DTCore

DT-CHShock

CH-AuShock

rshock (cm) < 0.001 0.026 1.1

rshock (cm) < 0.001 0.02 0.004

vshock (cm/s) 6.6 x 106 5.5 x 108 8.6 x 107

ni (cm-3) 1.5 x 1026 5.1 x 1024 5.0 x 1018

Ti (keV) 276 86 2.8

Te (keV) 72 47 0.69

Ave. charge state 1DT 1CH 1

CH 1Au 36

rshock / mfp > 1000 1.1 0.001

At 34.592 ns, the DT-CH Shock Thickness andIncoming Ion Mean Free Paths Become Comparable


34.58 34.585 34.59 34.595 34.6Timens0

100

200

300

400

500

ygre

nEVek

Ei

Hydrodynamic prediction of ion energy in shock frame

34.58 34.585 34.59 34.595 34.6Timens0

100

200

300

400

500

ygre

nEVek

Ei

Ei

Hydrodynamic prediction of ion energy in shock frame

Actual energy gained by ion

By 30 ps after Ignition, DT-CH Shock WaveIs Ineffective at Transferring Energy

34.58 34.585 34.59 34.595 34.6Timens0.1

0.2

0.5

1

2

5

10

kco

hS

ssenkci

htnaeM

eerfhta

p

• Ignition begins at ~34.56 ns.

• Mean-free path calculations includeion-ion collisions and ion-electron drag.

• shock / mfp ratio quickly falls.


Implications for HAPL Ions

• Hydrodynamic assumption of perfect momentum transfer between Lagrangian zones fails after ~25 ps.

• By ~40 ps after ignition, ions in the shock wave are free streaming.

• Energy spectrum of ions hitting the first wall will be of lower energy than estimated by purely hydrodynamic codes.

Effect is being evaluated using the Icarus (SNL) Discrete Simulation Monte Carlo (DSMC) computer code.

UW 1-D radiation hydrodynamics code, BUCKY, will be modified to predict the HAPL ion energy spectrum.


Icarus mesh for the HAPL problem.

ne Step 1

0200

400600

8001000

Zm0

200400

600800

1000

Rm51026

1 1027

1.51027

0200

400600

8001000

Zm

Initial electron density

UW is Simulating Target Explosions Using the Icarus Direct Simulation Monte Carlo (DSMC) Code

0 0.2 0.4 0.6 0.8 1Zmm0

0.2

0.4

0.6

0.8

1

Rmm

ne Step 1

020

4060

80100

Zm0

2040

6080

100

Rm51026

1 1027

1.51027

020

4060

80100

Zm• Code written by Dr. Tim Bartel, SNL.


Ion threat time of flight transport to first wall and deposition in wall computed by BUCKY.

• Temporal prediction of ion threat at the first surface improved (piece-wise continuous model replaces discrete model.) BUCKY results reproduced in “stand-alone” simulation

and compared to new model.

Further testing and comparisons.

Implementation in BUCKY with verification and validation.


Select a portion of the HAPL ion spectrum to simulate using new model

•Ion energies between 150 keV and 5 MeV

104 103 102 101 100

Radiuscm0

2 108

4 108

6 108

8 108

1 109di

ulF

yticolevmcs

Time 34.592 ns

DTvapor

DTice

CHDTmix

CH

Au


Discrete ion spectrum

Initial ion distribution < 0.5 cm

Outermost ions have highest velocities. Time-of-flight spreading widens pulse length at first wall.

0 s 0.3 microsecFirst wall

6.5 m


Discrete ion spectrum(2)

0.6 microsec 0.9 microsec



Discrete ion spectrum(3)




Continuous ion spectrum

0. s 0.3 microsec


Continuous ion spectrum(2)




Continuous ion spectrum(3)




Surface temperature vs. time for discrete and piece-wise continuous ion spectrums

Time (arbitrary units)

Tem

pera

ture

(ar

bitr

ary

units

)Time integrated source is the same for both curves.


Chamber and first wall integrated calculation computed by BUCKY.

Replace two region model with single region model with integrated equation of state and conductivity for plasma and solid state materials.

Radiation hydrodynamics, plasma properties

Heat conduction, solid state properties.

Two different models communicate across boundary.


Future work in threat spectra task

• Perform DSMC analysis of long mean-free path ions and modify hydrodynamic model.

• Verify and validate BUCKY for new models.

• Continue with improved simulations for HAPL reactor design.

• Continue to interface with wall response simulations and cavity clearing simulations.

threat spectra calculations for hapl chamber first wall

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