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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
ARIES Workshop20010607
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
ARIES Workshop20010607
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
ARIES Workshop20010607
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
ARIES Workshop20010607
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
ARIES Workshop20010607
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
ARIES Workshop20010607
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
ARIES Workshop20010607
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
ARIES Workshop20010607
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.