Aug. 8-9, 2006 HAPL meeting, GA 1
Advanced Chamber Concept with Magnetic Intervention:- Ion Dump Issues
- Status of Blanket Study
A. René Raffray
UCSD
With contributions from:
M. Sawan, G. Sviatoslavsky, I. Sviatoslavsky
UW
HAPL Meeting
GA, La Jolla, CA
August 8-9, 2006
Aug. 8-9, 2006 HAPL meeting, GA 2
Advanced Chamber Based on Magnetic Intervention Concept Using Cusp Coils (from last time)
• Use of resistive wall (e,g SiC) in blanket to dissipate magnetic energy (>90% of ion energy can be dissipated in the walls).
• Initial chamber schematic from Bertie Robson (with cone-shaped chamber blanket concept).
• The initial configuration was rotated 90° for the blanket analysis as this seems to favor the maintenance scheme.
• Dump plates to accommodate all ions but at much reduced energy (<10%).
• Dump plates could be replaced more frequently than blanket.
Aug. 8-9, 2006 HAPL meeting, GA 3
Ion Energy Deposition and Thermal Response of Dump Plates Estimated for Cone-Shaped Chamber
• For example case with ~10%of ion energy on plate, max. W temp. ~ 2200°C
Rmax
Rmin
y
Ion Dump Plates
Blanket Thickness
• Revised ion energy on dumps:- ~7.7% within 0.5 s- ~23% over 0.5-1.5 s
• Major change, ~30% ion energy on dumps• If dry wall dump within chamber, need ~30% of chamber area for dump• Then, why not design whole chamber the same way?
Aug. 8-9, 2006 HAPL meeting, GA 4
Seems More Advantageous to Position Dump Plate In Separate Smaller Chamber
• Could use W dry wall dump, but would require large surface area and same problem with thermomechanical response and He implantation
• Could allow melting (W or low MP material in W)
Hybrid case•Dry wall chamber to satisfy target and laser
requirements•Separate wetted wall
chamber to accommodate ions and provide long life•Have to make sure no
unacceptable contamination of main chamber
Ion Dump Ring chamber
Aug. 8-9, 2006 HAPL meeting, GA 5
Scoping Analysis of an Example Ring Chamber
• Some flexibility in setting chamber major and minor radii so as not to interfere with laser beams
• e.g., with Rmajor/Rminor =8/2.7 or 9/2.4 m, and assuming 35% of wetted wall area sees ion flux with a peaking factor of 1:- Ion dump area = 300 m2
- From 0 to 0.5 s, q’’ = 4.53x1010 W/m2
- From 0.5 to 1.5 s, q’’= 6.56x1010 W/m2
RmajorRmin
• Three cases:- W with phase change- Low MP metal (e.g. Be) in high porosity W
(~80-90%) which provides integrity and could help retain Be melt layer
- Wetted wall chamber with Pb as example material
0
1000
2000
3000
4000
5000
6000
1.0 10x
-9
1.0 10x
-8
1.0 10x
-7
1.0 10x
-6
1.0 10x
-5
1.0 10x
-4
1- / / + 3.5 mm W Be Pb mm FS
. = 500°Coolant Temp C
=20 /h kW m
2
-K
=4.51 10q'' x
10
/W m
2
0 0.5 from to s
=6.53 10q'' x
10
/W m
2
0.5 1.5 from to s
( )Time s
W
Be
Pb
10%W/90%Be
W
Structure
Coolant
Aug. 8-9, 2006 HAPL meeting, GA 6
Temperature and Phase Change Thickness Histories for W, Be and Pb for Example Case
• 350 MJ target (ion energy = 87.8 MJ)• Ion dump area = 300 m2
• From 0 to 0.5 s, q’’ = 4.53x1010 W/m2 (7.7% of ion energy)• From 0.5 to 1.5 s, q’’= 6.56x1010 W/m2 (22.3% of ion energy)
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
0.0E+0 1.0E-5 2.0E-5 3.0E-5 4.0E-5 5.0E-5
Time (s)
W
Be
Pb
1-mm W/Be/Pb + 3.5 mm FS
Coolant Temp. = 500°C
h =20 kW/m
2
-K
q''=4.51x10
10
W/m
2
from 0 to 0.5 μ s
q''=6.53x10
10
W/m
2
from 0.5 to 1.5 μ s
B
B
B
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-10
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-9
1x10
-8
1x10
-7
1x10
-6
1x10
-5
1x10
-4
1x10
-3
1x10
-9
1x10
-8
1x10
-7
1x10
-6
1x10
-5
1x10
-4
1x10
-3
Time (s)
B Be xmelt (m)
J Be xevap (m)
H W xmelt (m)
F W xevap (m)
R Pb xevap (m)
1-mm W/Be/Pb + 3.5 mm FS
Coolant Temp. = 500°C
h =20 kW/m
2
-K
q''=4.51x10
10
W/m
2
from 0 to 0.5 μ s
q''=6.53x10
10
W/m
2
from 0.5 to 1.5 μ s
Aug. 8-9, 2006 HAPL meeting, GA 7
Maximum Temperature and Phase Change Thicknesses for W, Be and Pb as a Function of Ion Dump Area
• 350 MJ target (ion energy = 87.8 MJ)• Evaporation loss per shot relatively modest
for W but could be a concern for Be (1 nm/shot ~ 0.43 mm/day)
• Stability of melt layer is a concern• Would Be in a porous W matrix be more
stable?• For wetted wall in particular, the evaporated
material (e.g.Pb) must recondense within a shot and not contaminate main chamber
Maximum Be, W and Pb Temperature as a Function of Ion Dump Area
0
1000
2000
3000
4000
5000
6000
7000
8000
150 200 250 300 350 400 450 500
Ion Dump Area (m2)
Maximum Temperature (°C)
PbBeW
• From 350 MJ target• Eff. q over time 0-0.5 microsecond = 1.35e-13 W• Eff. q over time 0.5-1.5 microsecond = 1.96e-13 W
Evaporated Thickness of Be, W and Pb as a Function of Ion Dump Area
1.E-14
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
150 200 250 300 350 400 450 500
Ion Dump Area (m2)
Evaporated Thickness (m)
PbBeW
• From 350 MJ target• Eff. q over time 0-0.5 microsecond = 1.35e-13 W• Eff. q over time 0.5-1.5 microsecond = 1.96e-13 W
Max. Melt Layer Thickness of Be and W as a Function of Ion Dump Area
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
150 200 250 300 350 400 450 500
Ion Dump Area (m2)
Max. Melt Layer Thickness (m)
BeW
• From 350 MJ target• Eff. q over time 0-0.5 microsecond = 1.35e-13 W• Eff. q over time 0.5-1.5 microsecond = 1.96e-13 W
Aug. 8-9, 2006 HAPL meeting, GA 8
Wetted-Wall Concept Could Consist of a Porous Mesh Through Which Pb Oozes to Form a Protective Film
• Need to make sure that protective film is reformed prior to each shot- radial flow through porous mesh- circumferential flow of recondensed Pb- no concern about any droplets falling in chamber
Pb flow
Porous mesh
Pb film
Pump
Liquid recycling
Aug. 8-9, 2006 HAPL meeting, GA 9
Film Condensation in Ion Dump Chamber
jnet = net condensation flux (kg/m2-s)
M = molecular weight (kg/kmol)
R = Universal gas constant (J/kml-K)
= correction factor for vapor velocity towards film
c e condensation and evaporation coefficients
Pg, Tg = vapor pressure (Pa) and temperature (K)
Pf, Tf = saturation pressure (Pa) and temperature (K) of film
Example Scoping Calculations• Ion energy from 350 MJ target =
87.8 MJ- 7.7% of ion energy to dump over
0-0.5 s
- 22.3% of ion energy over 0.5-1.5 s
• Evaporated thickness and vapor temperature rise from ion energy
deposition in ion dump chamber
• Liquid Pb as film material
• Conservatively small ion deposition area = 220 m2
e.g. 35% of chamber with Rmajor = 8 m
and Rminor = 2 m
jcond
jevap
TfPg
Tg
jnet=MR2π
⎛ ⎝ ⎜ ⎞
⎠ ⎟
0.5Γσc
Pg
Tg0.5
−σePf
T f0.5
⎡
⎣
⎢ ⎢
⎤
⎦
⎥ ⎥
Aug. 8-9, 2006 HAPL meeting, GA 10
Scoping Analysis of Pb Condensation in Example
Ring Chamber
• Characteristic condensation time very fast, ~0.01-0.02 s
Pb Vapor Density as a Function of Vapor Temperature Prior to Next Shot
1.0E-09
1.0E-08
1.0E-07
1.0E-06
500 1000 1500 2000 2500 3000 3500
Vapor Temperature prior to Next Shot(K)
Vapor Density Prior to Next Shot
(kg/m3) • Initial Pb density in chamber = 0.041 kg/m3• Rmajor = 8 m, Rminor = 2 m • Wall Pb film temp.= 773 K• Initial vapor temperature = 3190 K (linearly decreasing to final value in 0.2 s)• Sat.vapor density at 773 K =1.75e-8 kg/m3
Characteristic Chamber Condensation Time as a Function of Pb Vapor Temperature
1.0E-02
1.2E-02
1.4E-02
1.6E-02
1.8E-02
2.0E-02
2.2E-02
2.4E-02
1000 1500 2000 2500 3000 3500Vapor Temperature (K)
Chracteristic Condensation Time (s)
0.041 kg/m3 of Pb in Chamber (Rmajor = 8 m, Rminor = 2 m) with wall Pb film at 773 K
• Depending on final vapor temperature, vapor density prior to next shot is about 1-10 times higher than saturated vapor density at assumed wetted wall temperature of 773 K (1.75x10-8 kg/m3 or ~0.01 mTorr at ST)
Aug. 8-9, 2006 HAPL meeting, GA 11
Status of Blanket Study for Magnetic Intervention Chamber
• More detailed study of blanket using Pb-17Li and SiCf/SiC
- Neutronics
- Fabrication
- Assembly and maintenance
- Thermal-hydraulics
• Initial study of blanket using flibe and SiCf/SiC
- Possible configurations
- Neutronics
To be reported by M. Sawan and G. Sviatoslavsky
Aug. 8-9, 2006 HAPL meeting, GA 12
Self-Cooled Blanket Concept Coupled to a Brayton Cycle (Pb-17Li + SiCf/SiC and Flibe + SiCf/SiC)
Blanket Rchamber Max. SiC TMax. SiC/Cool T Coolant Tin Coolant Tout Coolant DP Cycle eff.
Pb-17Li 6 m 1000°C 900°C 483°C 799°C ~0.3 MPa 50%Pb-17Li 6 m 1100°C 950°C 580°C 930°C ~ 0.3 MPa 55%
Flibe 6 m 1000°C 912°C 519°C 700°C ~1 MPa 46%Flibe 6 m 1100°C 1010°C 590°C 790°C ~1 MPa 50%
• From simple estimate for flibe with same blanket configuration as Pb-17Li: - Flibe low Re and poor heat transfer properties result in lower cycle and higher P
for given SiCf/SiC Tmax constraint.
• Need to perform analysis for optimized flibe configuration
Aug. 8-9, 2006 HAPL meeting, GA 13
Summary• Scoping study of self-cooled Pb-17Li + SiCf/SiC blanket concept for use in
the magnetic-intervention cone-shaped chamber geometry completed
• Initial study of flibe + SiCf/SiC blanket started, needs to be completed based on neutronics calculations and optimized configuration
• Separate dump chamber with melted solid wall or wetted wall assessed for magnetic intervention case- Much relaxed atmosphere requirements for separate dump chamber
- Encouraging results as condensation is very fast
- Need to ensure no unwanted contaminants in main chamber
- Need more detailed design of dump chamber configuration including how to recycle liquid for wetted wall concept
• Future work- Complete flibe+SiCf/SiC blanket scoping study
- More detailed design of separate dump chamber