aries workshop 20010607 dry wall response to the hib (close-coupled) ife target presented by d. a....

ARIES Workshop20010607

Dry Wall Response to the HIB (close-coupled) IFE target

Presented by

D. A. Haynes, Jr.

for the staff of the

Fusion Technology Institute

University of Wisconsin

HIB (458MJ) n

fusion products

x-rays

D

T

p

He

C

Au

Be

Fe

Br

Gd


Summary/Outline

The target output from the close-copled HIB target is substantially different from that of the direct-drive laser driven targets, in that its

dominant non-neutronic threat component is from x-rays. Protecting the first wall from these x-rays requires more buffer gas than either

SOMBRERO or the AU-coated NRL targets.

The target output from the close-copled HIB target is substantially different from that of the direct-drive laser driven targets, in that its

dominant non-neutronic threat component is from x-rays. Protecting the first wall from these x-rays requires more buffer gas than either

SOMBRERO or the AU-coated NRL targets.

•Comparison of threat spectra

•First wall survival

•Future work


Though the total yields of the SOMBRERO and high yield closely-coupled HIB targets are similar, the partitioning and

spectra of the non-neutronic output differ significantly.

SOMBRERO (423MJ)

n

fusion products

x-rays

D (90keV)

T

p

He

C (1.6MeV)

Au (N/A)

•Over 25% of the yield from this target is in x-rays, compared with 5% of SOMBRERO’s, or 1% of the NRL Au-coated targets’.

HIB (458MJ) n

fusion products

x-rays

D

T

p

He

C

Au

Be

Fe

Br

Gd


X-ray Spectra

•The x-ray spectrum of the HIB target is harder than that of the SOMBRERO, but not so hard as the NRL Au-coated target.

•“Quantity has a certain quality all its own.”

If our goal is to prevent vaporization in a 6.5m chamber, we must include a buffer gas at pressures above those

required for SOMBRERO.

Target output x-ray spectra

0.0

0.2

0.4

0.6

0.8

1.0

0.01 0.1 1 10 100

Energy (keV)

Spe

ctra

(pe

ak n

orm

aliz

ed)NRL165(LASNEX)

SOMBRERO(legislated)

HIB (LASNEX)

22.5MJ

2.14MJ

115MJ


0

500

1000

1500

2000

2500

3000

3500

0 0.1 0.2 0.3 0.4 0.5 0.6

Xe Density (Torr)

Max

.Equ

ilibr

ium

Wal

l Tem

p. to

Avo

id

Vap

oriz

atio

n (C

)

SOMBRERO Target

NRL160 Target

Graphite Chamber Radius of 6.5m

•The gas density and equilibrium wall temperature have been varied to find the highest wall temperature that avoids vaporization at a given gas density.

•Vaporization is defined as more than one mono-layer of mass loss from the surface per shot.

•The use of Xe gas to absorb and re-emit target energy increases the allowable wall temperature substantially.

6.5m Graphite chamber results:

Chamber survives at 1000C, at 240mTorr, 1450C at 300mTorrChamber survives at 1000C, at 240mTorr, 1450C at 300mTorr


Surface Temperature and Temperature Profiles for 6.5m Graphite chamber, T_equilibrium=1000C

The first peak in temperature is due to the prompt x-rays. The second is due to the re-radiation of the x-ray and ion energy by the Xe buffer gas.

Wall surface temperature, 6.5m Graphite chamber, CC/HIB target

1000

1500

2000

2500

3000

3500

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

Time (s)

Tem

pera

ture

(C) 200mTorr Xe

240mTorr Xe

280mTorr Xe

Vaporizes 42g/shot

Wall temperature as a function of depth (CC HIB target, 6.5m C

Chamber)

1000

1500

2000

2500

3000

1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00Depth (cm)

Tem

pera

ture

(C)

t=1.83e-7 s


The amount of Xe necessary to prevent wall vaporization for the 6.5m graphite chamber and the CC HIB target is also

sufficient to stop all the ions except the knock-ons.

Per shot accumulation:

(240mTorr, 1000C T_eq.)

D 6.698E+16

T 7.020E+16

P 5.596E+15

3He 7.592E+11

4He 2.515E+13Does the accumulation of hydrogen and helium isotopes in the 1st mm of the wall at this rate pose a problem?

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

1.E-05 1.E-03 1.E-01 1.E+01

Depth

# o

f io

ns

D

T

p

3He

4He


The x-ray deposition length in W is considerably shorter than that of C. To avoid first wall degradation, between 0.3 and 1 Torr of Xe is

required to protect a W first wall at 6.5m from the CC HIB target, and a T_eq of 1000C.

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)

Att

enuatio

n le

ngth

(cm

)

C

W

Surface T as a function of time (CC HIB target, 6.5m W chamber)

1000

1500

2000

2500

1.E-08 1.E-07 1.E-06 1.E-05time (s)

Tem

per

atu

re (

C) 940 mTorr Xe


Conclusion and future work

•Xe density-T_equilibrium operating windows for the closely coupled HIB indirect drive target have been defined.

•The large fraction of this targets yield in x-rays (115MJ) necessitates some form of first wall protection for a 6.5m C or W wall.

•The amount of Xe required to protect the first wall from vaporization by x-rays is sufficient to stop all but the energetic knock-on ions. Is the accumulation of H and He isotopes in the first mm of the wall a problem?

•Xe density-T_equilibrium operating windows for the closely coupled HIB indirect drive target have been defined.

•The large fraction of this targets yield in x-rays (115MJ) necessitates some form of first wall protection for a 6.5m C or W wall.

•The amount of Xe required to protect the first wall from vaporization by x-rays is sufficient to stop all but the energetic knock-on ions. Is the accumulation of H and He isotopes in the first mm of the wall a problem?

•Future work:•Finish write up of dry wall chamber physics work.

aries workshop 20010607 dry wall response to the hib (close-coupled) ife target presented by d. a....

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