Thomson-Scattering Study of the Coronal Plasma Conditions ...
Transcript of Thomson-Scattering Study of the Coronal Plasma Conditions ...
![Page 1: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/1.jpg)
D. H. Froula et al.University of RochesterLaboratory for Laser Energetics
41st Annual Anomalous Absorption Conference
San Diego, CA19–24 June 2011
Thomson-Scattering Study of the Coronal Plasma Conditions in Direct-Drive Implosions
263.0
263.5
262.50.0 0.4
Shot 59726 Shot 59727
0.8 1.2 1.6 2.0 2.4 2.8
Wav
elen
gth
(n
m)
Time (ns)
![Page 2: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/2.jpg)
The electron and ion temperatures measured with Thomson scattering show agreement with nonlocal simulations
E19915
• A robust direct-drive-ignition design will require accurate modeling of the underdense plasma to allow laser–plasma instabilities (LPI) mitigation
• Thomson scattering is used to validate our nonlocal hydrodynamic model in the coronal plasma – simulations agree well with electron and ion-temperature measurements made 400 nm from the initial target surface – simulations over-estimate the fluid velocity by 20%
• Future experiments will explore regimes closer to the critical surface
These are the first measurements of direct drive coronal conditions.
Summary
![Page 3: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/3.jpg)
Collaborators
D. H. Edgell, W. Seka, I. V. Igumenshchev, P. B. Radha, and V. N. Gonchorov
University of RochesterLaboratory for Laser Energetics
J. S. Ross
Lawrence Livermore National Laboratory
![Page 4: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/4.jpg)
Two primary laser–plasma instabilities are a concern for direct drive and require an understanding of the underdense hydrodynamics
E19921
A robust direct-drive-ignition design will require accurate modeling of the underdense plasma to allow LPI mitigation.
1.0
10.0
0.10.5 1.0 1.5 2.0 2.50.0
Ho
t el
ectr
on
en
ergy
(%
)
〈I〉Lc
Two-plasmon decay scales withhydrodynamic properties at ncr/4
230 Te
Rbeam/Rtarget
30
0
10
20
0.7 1.0
2
0
4
6
8
0.4
Sca
tter
ed e
ner
gy (
%)
vrm
s (%
)
No
min
al
Calculations suggest an optimumspot size where CBET is minimized
*L-I
keVW cm m
T230
2-
e
14 nc
^^ ^
hh h
G TL
ec\CBET
S. X. Hu, “Simulation and Analysis of Long Scale-Length Plasma Experiments at the Omega EP Laser Facility,” this conference.
W. Seka, “Reducing the Cross-Beam Energy Transfer in Direct-Drive Implosions Through Laser-Irradiation Control,” this conference.
*A. Simon et al., Phys. Fluids 26, 3107 (1983).
![Page 5: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/5.jpg)
Thomson-scattering measurements were performed on direct-drive low-adiabat-implosion experiments
E19916
• 20 kJ of 351-nm light (59 beams) is used to drive a standard implosion
• Triple-picket pulse shape is designed for a low adiabat
• A 263-nm probe beam is used for Thomson scattering
• Scattered light is collected from a 60-nm × 75-nm × 75-nm volume 400 nm from the initial target surface
• Ion-acoustic waves propagating along the target radius are probed
ka = 2 k4~ sin(63/2) = 1.0 k4~
4~ probe TIM-6
TIM-6
k4~
63°
ks
ka
vflow
![Page 6: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/6.jpg)
Nonlocal hydrodynamic simulation parameters in the coronal plasma
E19948
The initial Thomson scattering measurements are made 400 nm from the initial target surface.
0.5
1.0
1.5
2.0
2.5
0.00.2 0.4
t = 1.85 ns t = 1.85 ns
0.6
TS volume
0.8 1.00.0
Ele
ctro
n t
emp
erat
ure
(ke
V)
Radius (mm)
1021
1022
10200.2 0.4 0.6
TS volume
0.8 1.00.0E
lect
ron
den
sity
(cm
3 )
Radius (mm)
![Page 7: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/7.jpg)
Thomson scattering from the ion-acoustic waves in CH plasmas provides a measure of Te, Ti, Vf
E19917
263.0
263.5
262.50.0 0.4
Shot 59726
Time for plasma to propagate to scattering volume
(GvH ~ 430 nm/0.57 ns = 7.5 × 107 cm/s)
Direct reflection
Drive laserspulse shape
Ion-acousticfeatures
Plasma fluidvelocity
Shot 59727
0.8 1.2 1.6 2.0 2.4 2.8
Wav
elen
gth
(n
m)
Time (ns)
4
6
8
2
0–8 –6 –4 –2 0–10
Ps
(arb
. un
its)
TeTe
Wavelength shift (Å)
4~ probe beam
![Page 8: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/8.jpg)
The electron temperature is determined from the wavelength separation in the ion-acoustic features
E19918
• The electron temperature is given by the wavelength separation of the ion-acoustic features
• The electron temperature is measured to within 20%
0.5
1.0
1.5
2.0
2.5
0.0–10 –8 –6 –4 –2 0
Ps
(arb
itra
ry u
nit
s)
Wavelength shift (Å)
Te = 1.8 + 0.2 keVTe = 1.8 – 0.2 keVTe = 1.8 keV
–5 –4 –3 –2 –1 0
Wavelength shift (Å)
t = 1.85 nsTeTe
![Page 9: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/9.jpg)
The measured electron and ion temperatures are in good agreement with nonlocal hydrodynamic modeling
E19919
• Late-time temperature discrepancies indicate anomalous absorption
• Simulations over estimate the flow velocity by 20%
0.5
1.0
1.5
2.0
0.01.0 1.5 2.0 2.5 3.00.5
Ele
ctro
n t
emp
erat
ure
(ke
V)
Time (ns)
0
1
2
3
4
5
6
7
8
1.0
Te
Ti
1.5 2.0 2.5 3.00.5
Flo
w V
elo
city
(×
107
cm/s
)
Time (ns)
![Page 10: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/10.jpg)
4~ light reflected from the target probes plasma properties at the ncr/4 surface
E19922
262.5
264.0
264.5
265.0
265.5
0.0 0.4 0.8–0.4–0.8
Time (ns)
4~ Thomson scattering, shot 59726
Target
300 nm
200 nm
4~ light is reflected from
the ncr/4 surface
30 nmThomsonscattering
Turning-pointreflection
Wav
elen
gth
(n
m)
263.0
263.5
263.0
263.5
300 m
30 m200 m
-II
exp2
10-0
210.
n
n
n=
^f
hp> H
![Page 11: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/11.jpg)
The wavelength shift and absorption of light propagating through the turning point is modeled
E19920
–2
0
2
0.0
Hydrodynamic simulation (nonlocal model)
Measurement
Calculation
0.5 1.0 1.5 2.0 2.5 3.0
Wav
elen
gth
(Å
)
Time (ns)
–2
0
2
Wav
elen
gth
(Å
)
![Page 12: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/12.jpg)
Many of the main features are reproduced by the simulations, but late-time discrepancies indicate over-estimated flow
E19920a
0.5 1.0 1.5 2.0
Measured
Calculations
2.5 3.0
Time (ns)
0.0
Wav
elen
gth
(Å
)
–1
–20.5 1.0 1.5 2.0 2.5 3.0
Time (ns)
0
1
2
0.0
Scattered light provides information about the hydrodynamic properties at the ncr/4 surface.
![Page 13: Thomson-Scattering Study of the Coronal Plasma Conditions ...](https://reader031.fdocuments.us/reader031/viewer/2022012507/6182e403019eb3377f33a8f3/html5/thumbnails/13.jpg)
The electron and ion temperatures measured with Thomson scattering show agreement with nonlocal simulations
E19915
• A robust direct-drive-ignition design will require accurate modeling of the underdense plasma to allow laser–plasma instabilities (LPI) mitigation
• Thomson scattering is used to validate our nonlocal hydrodynamic model in the coronal plasma – simulations agree well with electron and ion-temperature measurements made 400 nm from the initial target surface – simulations over-estimate the fluid velocity by 20%
• Future experiments will explore regimes closer to the critical surface
These are the first measurements of direct drive coronal conditions.
Summary/Conclusions