Characterization of Inertial Confinement Fusion Capsules Using an X-Pinch Source
High Energy Density Physics Summer School Berkeley California, August 2005
D. Haas, E. Shipton, Z. Karim, K. Wagschal, and B. DeBono, F.N. Beg
Department of Mechanical and Aerospace Engineering, University of California, San Diego, California, USA
R. Stephens,
General Atomics, San Diego, California, USA
(Conceived by Jiri Ulshmied in 1984)
• Produces a well localized bright x-ray source
• Allowing high magnifications
• Intense pulsed x-ray source
• Sufficient flux for single shot exposure of films
• Variable wire arrangement
• Control of X-ray pulse
• Tailor spectral emission (get lines in desired range up to 10 keV)
Marx band and compact
X-pinch apparatus in
Farhat Beg’s laboratory at
UCSD
• In this method of analysis the effect of phase contrast is used to
discern/emphasize boundaries of regions with different densities.
15 μm Sn
12.5 μm Ag
10 μm Fe + 50 μm Teflon
First Film
Second Film
Source energy = 7 keV , Source size = 5 μm
10.00
270
7.5 μm Ni + 300 μm PP
2 μm Al
7.6 μm Fe + 270 μm PP
Non used pinholes
(covered)
15 μm Cr
70
-30
4000
4500
5000
-130
1.00
5500
Density
Magnification 10
-230
Magnification 28.6
-330
0.10
Radiographic setup
Radius (μm)
Experimental PC Radiography
At the center of the target chamber (silver) you can see the crossing of the
wires signaling the position of the x-pinch. The anode (yellow) and cathode
(white) hold the x-pinch in place with a separation of 1cm. The capsule to
be imaged using phase contrast radiography is placed at the end of the shell
cone (green). An o-ring seals the cone, chamber, and camera (dark pink)
together. At the back of the camera a film plate (light pink) can be seen, the
x-ray film is placed between these elements and is later developed. In
addition, an algorithm was developed by Dr. Richard Stevens from General
Atomics to model the transmission of x-rays through the ICF capsules.
• For the actual experiment the following parameters were used:
• 5 μm Tungsten wires
• Cu foil filter 10 μm  X-rays 5-9 keV
• The simulation was done using 7 keV photons and a source size of 5μm
• In both cases the source to object distance was 5cm and the object to film
distance was 46.7cm yielding a magnification of 10.2.
Phase Change Radiography plastic CH shell (#051305s4)
(diameter = 1 mm , wall thickness = 20 μm)
Facilities at UCSD
1
Experiment
0.95
theory
0.9
0.85
0.8
0.75
Phase contrast region
0.7
444
464
484
X-ray film
504
524
0.995
0.985
0.975
0.965
0.955
0.945
0.935
0.925
0.915
544
Radius (μm)
O ring
X-pinch
Bright PC ring at boundary
Capsule
Phase Contrast foam filled plastic CH shell (#072105s3)
(diamiter 2mm , foam thickness 100 μm , wall thickness 20 μm)
12000
Contact Radiography
11000
For this method the ICF capsules were placed directly on the imaging film. This
method of analysis is used to eliminate all phase contrast effects and obtain a
baseline absorption profile for the shells.
Phase contrast region
Pixel Value
10000
• A theoretical curve was not generated due to the thin lens approximation in
the algorithm. This coupled with the close proximity of the shell (which acts as
a lens) to the image plane would render the results futile.
9000
8000
7000
6000
5000
390
410
430
450
470
490
510
530
Radius (μm)
• For the experiment the following parameters were used:
Applications
• 5 μm Tungsten wires
• Al foil filter 30 μm thick
Contact Radiography plastic CH shell (#042105s1)
(diamiter = 2mm , wall thickness = 49μm)
190000
170000
40μm
Intensity
Density
295
245
160000
195
150000
145
140000
95
130000
45
120000
-5
110000
100000
300
350
400
450
Radius (μm )
Notice no bright ring at density interface
500
-55
550
Density (g/cc)
180000
Pixel Intensity
• An array of metal and polypropylene filters were used to selectively attenuate the
emitted x-ray spectrum. In this experiment 9 different filter combination were used.
They were chosen so that only the edges of their transmission bands overlap.
•The filters were placed over the hole array below. A description of the filters can be
seen surrounding the shadowgraph at the top of the next column
Phase contrast region
170
.8 μm Al
4 Wire Pinch
• Peak current ~ 80 kA [pulsed]; risetime of ~ 40 ns
• Using x-ray diodes we can see that the peak of the x-ray pulse occurs some time
after the onset of the current pulse
• 14 ns (two 5 μm W wire)
• 30 ns (four 5 μm W wire)
• X-ray pulse length (FWHM) ~ 2ns
• Using a 20 μm Al filter
• Marx bank made of 4 0.22μF 50kV capacitors
• The line impedance is ~ 1.5 Ω
• X-pinch occupies about one square meter
in the laboratory and can be transported
• In a normal shadowgraph one would expect there to be a smooth gradient in
the pixel intensity; starting from the center of the shell and moving outward,
corresponding to the density. In a phase contrast shot you expect to see an
emphasized boundary (i.e. a ring of light at the interface) this can be seen in
the output of the algorithm developed by Dr. Richard Stevens (GA) as well as
the experimental shots below.
Theoredical Data Generated
25 μm Ti + 50 μm Teflon
Pixel Intensity
Advantages of a compact X-pinch
The x-ray films below show photon energies in the 1-10 keV range the first film
(left) is closest to the pinhole camera and the second film sits behind the first.
Intensity (normalized)
Deuterium-Tritium (DT) fuel ice layer
• 100 μm thick DT ice layer inside a 100 μm thick Be Cu capsule
• The ice layer detection requires phase contrast x-ray radiography
• Present sources are too large or require long exposure times, resulting in
blurred images
• X-pinch is a bright and small enough source to eliminate blurring as in current
techniques
• E ~1-10 keV
, Source size < 1 μm , Duration < 1 ns
• Images produced from a compact system show 1-10keV x-ray source capability
Phase Contrast (PC) Radiography
Density (g/cc)
• National Ignition Facility (NIF) cryo-ignition target requires validation of its
Pinhole images
Intensity (normalized)
Review
• Ice layer characterization in NIF cryo shells
• Time resolved images at sequenced time steps can provide an
evolution sequence
• Ice layer melting
• Equation of state studies
Future work and ongoing research
•
•
•
•
Reproducibility in emission brightness
Develop X-ray scaling with current up to 300 kA
Select wire material for optimum emission lines
Control intervals in multiple pinch systems