Optical Diagnostics of Colliding
Laser Produced Plasmas
Paddy Hayden
National Centre for Plasma Science & Technology (NCPST)/
School of Physical Sciences, Dublin City University
EMMI Workshop on Non-Linear Dynamics of Simple Quantum Systems at
Extreme Temperatures and Intensities Nov 2nd 2011
Outline
•
•
•
•
Colliding Plasmas – Orientation
Time Resolved Imaging
Interferometry
Visible Spectroscopy
– Density
– Temperature
• Ion Emission
• Summary
EMMI NDSQS Workshop 2011
Colliding Plasmas - Orientation
EMMI NDSQS Workshop 2011
Colliding Plasmas - Orientation
1
1
0.8
0.8
0.8
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Density (n/n0)
1
Density (n/n0)
Density (n/n0)
Multi-fluid colliding plasma simulations, Rambo and Denavit, J. COMP. PHYS. 98 317 (1992)
0.6
0.4
0.2
0.4
0.2
When plasma plumes collide there are two extreme scenarios:
1. Interpenetration
- interactions
collisions
Distance (x/x )
Distanceare
(x/x ) mostly via binary
Distance
(x/x )
0 time - plumes decelerated
150 timesteps
300rapid
timesteps
2. Stagnation
at collision plane,
accumulation of material, kinetic energy converted into excitation
energy (glow), rapid growth of dense (stagnated) layer,………
0
0
50
100
150
200
0
0
50
100
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1
0.8
0.8
0.6
0.4
0.2
100
Distance (x/x0)
50
100
150
200
200
150
200
6
5
0.6
0.4
0
0
150
0
0.2
50
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200
Density (n/n0)
1
0
0
150
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Density (n/n0)
Density (n/n0)
0.6
4
3
2
1
50
100
Distance (x/x0)
EMMI NDSQS Workshop 2011
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200
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0
50
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Distance (x/x0)
Colliding Plasmas - Orientation
• The parameter which determines whether the
plumes are likely to interpenetrate or stagnate is the
so-called ‘collisionality parameter’ given by:
 
D
ii
• Where D is the separation between the two plasmas
and λii is the ion-ion Mean Free Path (MFP).
ii 1  2 
m v 
2 2
1 12
4e 4 Z 4 n2  ln 12 
EMMI NDSQS Workshop 2011
Colliding Plasmas - Orientation
From laterally colliding
Controllable parameters:
1. Plasma Separation
2. Laser intensity
o)
3. Target
angle One
(0o tocan
180engineer
Key point:
stagnation layer
4. Laser
wavelength/pulse
characteristics;
‘hardness’, density, temperature,
shape,
etc. by varying geometry (D) and laser-target
duration.
interaction physics (mfp, λii) - application specific…..
to counter streaming
EMMI NDSQS Workshop 2011
Time Resolved Imaging
Resolution of ~4 ns (now 1.5 ns), use filters to isolate emission from a particular ion stage
EMMI NDSQS Workshop 2011
Time Resolved Imaging
x 10
4.5
Dt = 30 ns
Delay = 30 ns
Dt = 0 ns
500
4
4
500
1000
3
2.5
1500
2
1.5
2000
Distance (m)
Distance (m)
3.5
Delay = 100 ns
16000
Dt = 100 ns
14000
12000
1000
10000
1500
8000
6000
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4000
1
2500
2500
2000
0.5
500
1000
1500
2000
500
2500
1000
1500
2000
2500
Distance (m)
Distance (m)
12000
Delay = 600 ns
Delay = 200 ns
Dt = 200 ns
10000
1000
8000
1500
6000
2000
4000
2500
2000
500
1000
1500
2000
Dt = 295 ns
500
Distance (m)
Distance (m)
500
1000
Dt = 600 ns
1000
1500
2000
500
2500
500
2500
1500
1000
1500
2000
2500
Distance (m)
Distance (m)
Seed Plasmas with 1.3 mm separation, each formed with 300 mJ, 1064 nm, 6 ns
laser pulses. Spotsize: ca. 100 μm. Time delay measured relative to the peak of
the split laser pulse.
EMMI NDSQS Workshop 2011
0
Angle Resolved Imaging
EMMI NDSQS Workshop 2011
Nomarski Interferometry
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Comparison to Imaging
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Visible Spectroscopy
Min. gate width ~4 ns
Spatial Res. = 70 μm
Spectral Res. = <0.2nm
EMMI NDSQS Workshop 2011
Visible Spectroscopy
Time-Space Density Measurements:
Target
Delay = 300 ns
Wavelength (nm)
Voigt profiles fitted and densities determined
by Lorentzian width and Stark parameters in C.
Colón et al. Phys. Scr. 73 (2006) 410–419.
EMMI NDSQS Workshop 2011
Visible Spectroscopy
100o target
Experimental Parameters used: 140o wedge target,
each seed plasma formed with 200 mJ, 1064 nm,
6 ns pulses. Spotsize: 100 μm, plasma separation:
2.6 mm. Time delay relative to peak of laser pulse.
EMMI NDSQS Workshop 2011
Visible Spectroscopy
Time-Space Temperature Measurements
Target
Delay = 300 ns
Wavelength (nm)
Temperatures from 485.97 nm and 492.57 nm
Sn III lines. Spectrum is binned at 0.5 mm
intervals.
Temperatures were determined from the line
ratios.
EMMI NDSQS Workshop 2011
Visible Spectroscopy
100o target
Distance (mm)
Experimental Parameters used: 140o wedge target, each
seed plasma was formed with 200 mJ, 1064 nm, 6 ns
pulses. Spotsize: 100 μm and plasma separation: 2.6 mm.
Time delay relative to peak of laser pulse.
EMMI NDSQS Workshop 2011
Ion Emission
Angle Resolved Ion Emission Experiment
EMMI NDSQS Workshop 2011
Ion Emission
We observe quite significant narrowing of the TOF
distribution compared to single plasma plumes
Plasma ion bunch
compression
EMMI NDSQS Workshop 2011
Ion Emission
As we move the detector off normal emitted ion flux from each
(left or right hand side) single plume dominates => weak lateral
emission from stagnation layer -fewer damaging fast ions and
perhaps less plasma debris?
EMMI NDSQS Workshop 2011
Ion Emission
One can also tune the width and peak energy of the ‘total ion’ TOF
distribution with the laser energy (6ns/1064nm)
EMMI NDSQS Workshop 2011
Summary
• Strong stagnation in table top colliding plasmas due to
large value of the collisionality parameter (ζ)
• Degree of confinement/ hardness of the stagnation
layer can be controlled by designing the value of ζ
• Stagnation layer becomes quite uniform after 100ns
• It looks attractive for investigation as alternative
injector systems for ion accelerators, pulsed laser
materials deposition source, LIBS, laboratoryastrophysical model experiments, X-ray lasers, fusion
(Hohlraums) etc.
• Real time exploration of t and D to optimise
stagnation layer conditions in an application specific
manner.
EMMI NDSQS Workshop 2011
Acknowledgements
DCU:
J. Costello, P. Hough, J. Dardis, T. Kelly, C. Fallon and B. Doohan
S. S. Harilal. School of Nuclear Engineering, Purdue University
N. Gambino, University of Catania, Italy
UCD:
G. O’Sullivan, P. Dunne, E. Sokell, F. O’Reilly, ...
TCD:
J. Lunney, I. Tobin
Funding: Science Foundation Ireland 07/IN.1/I1771, Irish
Research Council for Science Engineering and Technology
(Embark Initiative), EU COST MP0601 Action and ERASMUS
MUNDUS - EMJD -EXTATIC - FPA 2012-0033 - EACEA programme
EMMI NDSQS Workshop 2011