1. 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 Review cryo-ignition target requires validation of its Deuterium-Tritium (DT) fuel ice layer National Ignition Facility (NIF) cryo-ignition target requires validation of its Deuterium-Tritium (DT) fuel ice layer 100 μm thick DT ice layer inside a 100 μm thick Be Cu capsule 100 μm thick DT ice layer inside a 100 μm thick Be Cu capsule The ice layer detection requires phase contrast x-ray radiography The ice layer detection requires phase contrast x-ray radiography Present sources are too large or require long exposure times, resulting in blurred images 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 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 E ~1-10 keV, Source size < 1 μm, Duration < 1 ns Images produced from a compact system show 1-10keV x-ray source capability Images produced from a compact system show 1-10keV x-ray source capability Advantages of a compact X-pinch (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) 4 Wire Pinch Facilities at UCSD 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 μ m W wire) 30 ns (four 5 μ m 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 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 Pinhole images 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. Contact Radiography 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. 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. For the experiment the following parameters were used: 5 μm Tungsten wires Al foil filter 30 μm thick Phase Contrast (PC) Radiography In this method of analysis the effect of phase contrast is used to discern/emphasize boundaries of regions with different densities. 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. Applications 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 Radiographic setup 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. Experimental PC Radiography 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. 12.5 μm Ag 15 μm Sn25 μm Ti + 50 μm Teflon 10 μm Fe + 50 μm Teflon 7.5 μm Ni + 300 μm PP 7.6 μm Fe + 270 μm PP.8 μm Al 15 μm Cr 2 μm Al First FilmSecond Film Non used pinholes (covered) Bright PC ring at boundary Phase contrast region 40μm Notice no bright ring at density interface Phase contrast region Capsule Marx band and compact X-pinch apparatus in Farhat Beg’s laboratory at UCSD X-pinch X-ray film O ring