Title :
Variations in the Mass Ablation of Tungsten Wire Arrays with Different Initial Wire Sizes
Author :
Sinars, D.B. ; Cuneo, M.E. ; Yu, E.P. ; Waisman, E.M. ; Wenger, D.F. ; Bliss, David E. ; Porter, J.L. ; Lebedev, S.V.
Author_Institution :
Sandia Nat. Labs., Albuquerque, NM
Abstract :
Summary form only given. The radiation source for Z-pinch-driven hohlraum, inertial confinement fusion (ICF) tests on the 20 MA Z facility is a single (or nested) 20-mm diameter tungsten wire array. To ensure that the scaling of these loads to higher currents are well understood, we have been investigating the behavior of these tungsten arrays. During our experiments, the wire array diameter (20 mm), height (10 mm), wire number (300), and pulsed power hardware were kept constant, but the initial wire diameters of the array was varied. Radiography and shadowgraphy measurements show that each array retains core/corona structure until 55-60% of its total implosion time. Using the same techniques as in [D.B. Sinars et al., Phys. Rev. Lett. 93, 145002 (2004)], radiographs of arrays using 5.0, 7.4, and 11.5 mum wires were obtained at the same point in the current pulse, at two different current values chosen so that these arrays were still in the core/corona phase. The radiographs were used to infer the mass distribution of the ablated plasma prefill. A momentum balance ("rocket") model fits the mass profile of the 11.5 mum array assuming a constant ablation velocity of about 13-15 cm/mus, similar to what was inferred for this array in [M.E. Cuneo et al., Phys. Rev. E]. For the lighter two arrays significantly less mass is ablated, and the mass ablation profile appears inconsistent with the rocket model, even if higher velocities are assumed. A variation of the ablation rate with wire size is not explicitly predicted by the rocket model, though variations of the ablation velocity have been inferred for different wire/gap ratios in 1-MA experiments. The data and comparisons to the model and 2D-rthetas ALEGRA simulations will be presented
Keywords :
Z pinch; corona; exploding wires; explosions; plasma diagnostics; plasma inertial confinement; plasma simulation; tungsten; 10 mm; 11.5 mum; 20 MA; 20 mm; 5.0 mum; 7.4 mum; ALEGRA simulations; W; Z-pinch-driven hohlraum; corona structure; implosion; inertial confinement fusion; mass ablation; momentum balance model; radiation source; radiography; shadowgraphy; tungsten wire arrays; Corona; Hardware; Inertial confinement; Phased arrays; Radiography; Rockets; Testing; Time measurement; Tungsten; Wire;
Conference_Titel :
Plasma Science, 2005. ICOPS '05. IEEE Conference Record - Abstracts. IEEE International Conference on
Conference_Location :
Monterey, CA
Print_ISBN :
0-7803-9300-7
DOI :
10.1109/PLASMA.2005.359212