A nonuniform layer of deuterium-tritium (DT) ice inside a spherical inertial confinement fusion (ICF) target held in an isothermal cryogenic environment should be driven toward uniformity by the beta-decay heat of the tritium. Experiments have been performed at KMS fusion to verify this hypothesis. Two major conclusions may be drawn from the initial results: (1) the beta decay of the tritium does deposit energy in the target, as evidenced by melting of DT ice when the target is well insulated from its surroundings, and (2) solid layers of DT ice sublime because of beta-decay heat. Both conclusions are reinforced by companion studies with nonradioactive hydrogen-deuterium (HD) ice in similar targets held under similar experimental conditions.
A solid deuterium–tritium fuel layer within a spherical inertial confinement fusion target will be driven uniform by β-decay energy if the target is held in an isothermal environment. The apparatus we constructed to verify this process provides an isothermal and radiation-tight environment. Heat exchange between the target (≂20 K) and the environment (4.2 K) is regulated by controlling the helium exchange gas through a specially constructed manifold. A unique optical system maintained at low temperatures allows direct observation of the fuel layer uniformity. Tritium containment in the event of a target failure is assured by tungsten–inert gas welding of the stainless-steel structure. This system conveniently fits a standard vendor supplied 100-l Dewar, and is designed to minimize boiloff and cooldown losses by means of an efficient helium vapor counterflow system. We have also incorporated a vibration isolation system to permit holographic interferometry imaging and evaluation of the fuel layers.
To take full advantage of the capabilities offered by the Omega laser facility, the experimental teams at the University of Rochester need the capability to field cryogenic targets. The cryogenic target delivery system must be able to produce uniform solid or liquid DT layers 2-20 pm within polymer shells which are 300-400 fim in diameter. The facility must be able to maintain its experiment rate of one shot per ~ h and each target must be documented within the experimental chamber for postshot analysis. We will discuss the approach and equipment that KMS is using in collaboration with the University of Rochester to provide Omega with the capability to field cryogenic inertial confinement fusion targets.
Thin solid samples of deuterium–tritium (DT) have been seen to sublime and redistribute within spherical inertial fusion targets due to the heat generated by beta decay. We have frozen thin DT samples within glass shells of 890 and 3750 μm diameter, and observed the evolution of the solid towards more symmetric distributions using real time holographic interferometry. Holographic interferometry provides more sensitivity than direct imaging or classical interferometry to observe the thin (10–30 μm) solid samples in these shells.
Development of polyvinyl alcohol shells overcoated with polystyrene layer for inertial confinement fusion experiments J. Vac. Sci. Technol. A 5, 2778 (1987); 10.1116/1.574740 Deuterium permeation properties of betairradiated and unirradiated poly(vinyl alcohol) and polystyrene shells J.
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