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Measuring Bulk Fuel Velocity at the National Ignition Facility with Neutron Activation
Presentation to 248th American Chemical Society National Meeting
August 10, 2014
Darren Bleuel
NAD Physics Basis Ac-va-on Concept
Four energy regions of interest:
1-‐10 MeV (T-‐T / D-‐D spectrum)
10-‐13 MeV (DownscaGered)
13-‐15 MeV (Primaries)
15-‐30 MeV (Ter-aries)
Yield (n/ M
eV)
Energy (MeV)
Neutron Spectrum
Neutron energy (MeV)
115In(n,n’) ⇒ 115mIn (t1/2=4.5 h) 93Nb(n,2n) ⇒ 92mNb (t1/2=10 d) 90Zr(n,2n) ⇒ 89Zr (t1/2=3.3 d) 63Cu(n,2n) ⇒ 62Cu (t1/2=9.74 m) 12C(n,2n) ⇒ 11C (t1/2=20 m)
Cross sec-o
n (b)
Ac-va-on Foil cross sec-ons
€
Yn =4πR2ANc
mfBR faNAεirrεdet < σ > [e−λ (Δtstart ) − e−λ (Δtend ) ]
14 MeV n
10 MeV n
HPGe
LLNL Nuclear Counting Facility in B151
3
t1/2=4.5h
t1/2=3.3d t1/2=15h
The six “flavors” of Neutron Ac6va6on
4
DIM-‐NAD (DD)
Snout-‐NAD (DD)
Well-‐NAD (DT)
Flange-‐NAD (DT)
NAD20 (DT)
(not actual loca-ons)
In
In
Zr
Zr Zr Zr Zr Zr Zr Zr
Zr Cu
t1/2=4.5h
t1/2=4.5h
t1/2=3.3d
t1/2=3.3d t1/2=9.7m
t1/2=3.3d
Background model valida-on (DT)
Al Zr In
t1/2=4.5h
t1/2=3.3d t1/2=15h
The six “flavors” of Neutron Ac6va6on
5
DIM-‐NAD (DD)
Snout-‐NAD (DD)
Well-‐NAD (DT)
Flange-‐NAD (DT)
NAD20 (DT)
(not actual loca-ons)
In
In
Zr
Zr Zr Zr Zr Zr Zr Zr
Zr Cu
t1/2=4.5h
t1/2=4.5h
t1/2=3.3d
t1/2=3.3d t1/2=9.7m
t1/2=3.3d
Background model valida-on (DT)
Al Zr In
The six “flavors” of Neutron Ac6va6on
6
Flange-‐NAD (DT)
(not actual loca-ons)
Zr Zr Zr Zr Zr Zr Zr
t1/2=3.3d
Flange-NAD Overview
7
• Zirconium samples mounted outside 9-‐16 ports around target chamber.
• Inten-on is to measure yield anisotropy to <2-‐5% precision by taking in ra-o to isotropic shot.
(not actual loca-ons) n
n
Lead Shield
Detector
10 samples
RY (Ω)=
Double ratio to minimize uncertainties
8
Take ra-o of one flange posi-on to another (Well-‐NAD) and normalize to an isotropic shot (exploding pusher). All systema-c errors are eliminated.
Note: <σ> does not cancel in the case of a “bulk fuel velocity.”
Y(Ω2)
Y(Ω1) Shot A: “layered”
Shot B: “exploding pusher” (isotropic)
ΔρR = − ADTσ scatter
ln RSA( ) This “double ra-o” of specific ac-vi-es is related to the areal density differences of the fuel.
RSA =YA (Ω1) /YA (Ω2 )YB (Ω1) /YB (Ω2 )
=mA2mB2
mA1mB1
"
#$
%
&'AA10
AA20
"
#$
%
&'AB20
AB10
"
#$
%
&'
Flange-NAD locations
9
New FNAD locations (blue) were added after Feb 2012.
Flange-NAD locations
10
Activity ratios measured at 17 locations
Flange-NAD locations
11
Fit to low-order spherical harmonics
Activity ratios measured at 17 locations
Flange-NAD is sensitive to both ρR and core velocity along a given line of sight.
12
90Zr and 39K σ-‐(n,2n)
µ0=14.07 MeV, σ=0.150 MeV
nToF and MRS yields are inde-‐pendent of velocity. Peak shil independently measures velocity.
Velocity
ΔρR
How to calibrate when the measurements are on the “calibration” shots?
13
u
Ω2
Ω1
A0
A0=εε1+α⋅ Ω̂
1+α⋅ Ω̂
#
$%
&
'(
Ω2
Ω1 u ε2 ε1
A2 A1
u
NIF Chamber In principle… • 12 calibra-on (Expl. Push.) shots • x 17 zirconium ac-va-on measurements • = 204 datapoints
• 17 irradia-on efficiencies • + 3 velocity vectors x 12 shots • = 53 unknowns
RSA =YA (Ω1) /YA (Ω2 )YB (Ω1) /YB (Ω2 )
=mA2mB2
mA1mB1
"
#$
%
&'AA10
AA20
"
#$
%
&'AB20
AB10
"
#$
%
&'
Assumed isotropic!
Can a global fit to all calibra-on shots give us the efficiencies despite velocity effects?
α =3.2%
100km / s
How to calibrate when the measurements are on the “calibration” shots?
14
u
Ω2
Ω1
A0
A0=εε1+α⋅ Ω̂
1+α⋅ Ω̂
#
$%
&
'(
Ω2
Ω1 u ε2 ε1
A2 A1
u
NIF Chamber
RSA =YA (Ω1) /YA (Ω2 )YB (Ω1) /YB (Ω2 )
=mA2mB2
mA1mB1
"
#$
%
&'AA10
AA20
"
#$
%
&'AB20
AB10
"
#$
%
&'
Assumed isotropic!
If we get clever…
A0
A0=εε1+α⋅ Ω̂ − Ω̂( )+O(α 2 )( )Ω2 Ω1
ε2 ε1
A2 A1
u -
A0A0
A0A0=ε εε ε
1+α⋅ Ω̂ − Ω̂ + Ω̂ − Ω̂( )+O(α 2 )( )Ω2 Ω1
ε2 ε1
A2 A1
u A4 A3 ε3
ε4 Ω4 Ω3
Ω3
Ω4
We found six four-‐vector combi-‐na-ons which sum to <10%, including every FNAD loca-on. Six constraints were added to our global fit, elimina-ng velocity bias.
How to calibrate when the measurements are on the “calibration” shots?
15
Shot #
Low velocity High velocity
Core Velocity Correlates Strongly with Drive Asymmetry N101212-001 exploding pusher (direct drive)
16
Q35T
Q35B
Core velocity fit!!186±20 km/s! θ0=75°φ0=220°!
N101212-001 Flange-NAD!
Q35T
Q35B
Drive distortion (Hydra postshot)!
Core fuel velocity correlates with drive distortion, Doppler-shifting neutron spectrum, increasing activation along velocity axis.
North!pole!
South!pole!
N120217-‐001 Flange-‐NAD example of MRS peak shi8 predic9on from FNAD data set
Author—Yeamans 17 NIF-0000-00000s2.ppt
188±47 km/s!θ0=98°φ0=322°!dropped 22T/22B!
χ2: 9.20 (ν=13) p-‐value: 0.24
MRS peak upshifted 113±16 keV!FNAD predicts 98 ± 13 keV upshift!
MRS has measured the DT peak energy shift predicted from the FNAD fit to within the known errors on every exploding pusher where MRS ran in medium-resolution mode and yield was sufficient for FNAD performance."
N101212-001!!186±20 km/s! θ0=75°φ0=220°!
Flange-NAD Measured Core Velocities Exploding Pushers with Drive Asymmetries normalized to N120721-001 (velocity corrected)
18
Q22T
Q22B
165±33 km/s!θ0=86°φ0=320°!
N120217-001!
N120331-002!135±40 km/s!θ0=99°φ0=244°!
Q43T
Q43B
Q35T
Q35B
N101030-002!!129±36 km/s! θ0=79°φ0=144°!
Q41T
Flange-NAD Measured Core Velocities Exploding Pushers with Target Alignment Problems normalized to N120721-001 (velocity corrected)
19
100±40 km/s!θ0=88°φ0=162°!
Observed velocities on all twelve exploding pusher shots
20
Conclusions
21
• Ac-va-on provides an accurate DT yield measurement at the NIF. • Flange-‐NAD can provide a high-‐precision measure of yield anisotropy and bulk
velocity.
• Making a measurement on a calibra-on shot is tricky, but not impossible when you have clever post-‐docs.
• Measured bulk fuel veloci-es are as high as 200 km/s, correla-ng with laser drive asymmetries and misaligned capsules.
LLNL • Lee Bernstein • Rich Bionta • Jac Caggiano • Charlie Cerjan • Owen Drury • Chris Hagmann • Ed Hartouni • Robert Hatarik • Steve Hatchett • Hesham Khater • Joe Kilkenny • Kenn Knittel • Sebastien Le Pape • Andy Mackinnon • Jim McNaney • Ken Moody • Mike Moran • Dave Munro • Dieter Schneider • Dawn Shaughnessy • Charles Yeamans • Rich Zacharias
UCB • Brian Daub • Bethany Goldblum
LLE • Tim Duffy • Vladimir Glebov • Jim Knauer • Craig Sangster OHIO • Carl Brune SNL • Gary Cooper • Ray Leeper • Carlos Ruiz
LLNL NCF: • Bryan Bandong • Cindy Conrado • Phil Torretto • Todd Wooddy MIT • Dan Casey • Johan Frenje • Maria Gatu Johnson SUNY-Geneseo • Cassie Brown • Steve Padalino
LMJ • Jean-Luc Bourgade
Extra Slides
Are the varia6ons in layered cryo shots real or sta6s6cal? minimum yield 3e13 and Flange-‐NAD diagnos9c success required
Author—Yeamans 24
FNAD loca-on
χ2: 513 (ν=180) p-‐value: 1
Exploding Pusher Shots, velocity-‐corrected minimum yield 3e13 and Flange-‐NAD diagnos9c success required
Author—Yeamans 25
FNAD loca-on
152 data points, p=0.52. Instrument response is demonstrated.
“Layered-cryo” w/ hohlraum (indirect drive) vs. “Exploding pusher” (direct drive)
26
“Layered-‐Cryo” “Exploding Pusher”
Simple direct drive targets
DT Gas
Wall explodes driving shock into DT
Laser beams
Hot core, ‘point’ source of neutrons + soU x-‐rays
n14MeV
• Laser energy produces ~ 10 keV electrons: heats thin Si capsule wall • Low ρR (no n scatter) • Isotropic • Yield up to 5x1015 n
• Laser energy produces ~300 eV x-rays in hohlraum “can,” heating CH or Be capsule wall • Cryogenic DT “layered” fuel shell with gas interior • “Hot spot” ignites high ρR layer burn • Yield up to 1019 n
CH or Be ablator shells
solid cryo DT layer
DT gas
Cryogenic, x-ray driven, layered targets
Flange-NAD needs calibration to low-velocity, high-yield exploding pusher
27
Most low-velocity shots are low yield. N111121 used as calibration for 10-location FNAD.
nToF equator-‐alcove peak -me shil ΔE (keV
)
Calibra-on for 10-‐port FNAD
Calibra-on for 17-‐port FNAD (aler velocity correc-on)
<1014n
} low velocity?
Exploding pusher shots
Courtesy: Jim
Knaur
Core velocities for nTOF LOS"
Shot Core Velocity
Magnitude (km/s)
Polar angle (°)
Azimuthal angle (°)
N110603 132 115 324 N110617 82 116 229 N110618 31 111 200 N111114 187 40 247 N111121 39 39 281 N120217 193 120 319 N120331 129 123 229
Derived core velocity vectors for exploding pushers
FNADS 165km/s (86, 319)
162km/s (112, 227)
Courtesy: Jim
Macnane
y
Flange-NAD results N120808-001 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 29
N120802-001 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 30
N120720-002 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 31
N120716-001 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 32
N120626-002 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 33
N120422-002 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 34
N120417-002 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 35
N120412-001 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 36
N120405-003 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 37
N120321-001 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 38
N120316-002 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 39
N120219-001 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 40
N120213-001 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 41
N120205-002 normalized to N120721-001 velocity-corrected
Author—Yeamans, Aug 2012 42