An investigation of the effects of system parameters on the production of hollow hydrogen droplets

Abstract

Many inertial confinement target designs have the fuel as a frozen spherical shell of hydrogen isotopes. One method of manufacturing these targets would be to produce the spherical shell first. In this paper we report on an experimental study on the production of spherical shells of liquid and solid hydrogen. These shells are made by acoustically breaking up a jet of superheated liquid hydrogen into drops and at the same time cavitating a bubble in the center of each drop. The resulting growth of the bubbles by evaporation produces the spherical shells. The size and the aspect ratio of the spherical shells are found to be affected by several parameters. The mass of the drop depends on the diameter of the nozzle from which the jet emerges. Also, varying the frequency of the acoustic excitation gives some control of the droplet size. The aspect ratio depends most strongly on the liquid temperature and the droplet-chamber pressure. Increasing the temperature or lowering the pressure increases the aspect ratio of the shell. If the pressure is lowered below the triplet-point pressure of hydrogen, the shells freeze forming a spherical shell of solid hydrogen.

Three‐month, zero‐order piroxicam release from monodispersed double‐walled microspheres of controlled shell thickness

“…PPF technology has been established as a means to fabricate predefined distributions of polymer microspheres 15–17. Furthermore, a modified PPF technology has been developed to produce precision double‐walled microspheres and microcapsules comprising various materials localized to the core or shell phase 18–21. This method was used to produce PLG‐PL double‐walled microspheres of a controlled shell thickness.…”

Uniform Biodegradable Hydrogel Microspheres Fabricated by a Surfactant‐Free Electric‐Field‐Assisted Method

“…Previously, we reported the fabrication of uniform MS of oil‐soluble polymers, such as poly[( D , L ‐lactide)‐ co ‐glycolide] (PLG) and polyanhydride, that was achieved by simultaneously utilizing mechanical and hydrodynamic forces 27–30. This method evolved from the earlier work by Kim et al originally applied to the fabrication of precision frozen hydrogen MS and silica aerogel microcapsules 31–37. In this method, a carrier stream immiscible with the polymer solution was introduced into the outer nozzle of a dual‐nozzle system so that it could surround the solution jet formed by the inner nozzle and accelerate it, to make it thinner than the nozzle opening.…”

“…Recently, following similar work previously performed on other materials,27–37 acoustic vibration was employed to fabricate monodisperse alginate MS (AMS) 38. A nozzle generated a smooth jet of alginate solution, which subsequently broke up into uniform droplets by acoustic excitation.…”

Microspheres for Drug Delivery

“…Following previous work reporting production of core/shell particles made from a variety of inorganic materials [68,85,87], the uniform solid microsphere fabrication methodology described in the preceding sections (Figures 2.1 and 2.2) has been further extended to produce uniform double-walled polymeric microspheres with controllable size and shell thickness. The method, as illustrated in Figure 2.4, employs three coaxial nozzles to produce a smooth coaxial jet of controllable size, comprising a carrier, annular shell and core streams, which is acoustically excited to break up into uniform core-shell droplets.…”

“…Uniform microspheres of controlled sizes, both solid and hollow, were previously fabricated from a variety of non-polymeric materials using acoustic excitation [56,64,68,78,85,87,90].…”