FIELD

The disclosure relates to the field of pulsed fusion events. More particularly, this disclosure relates to a simplified diode assembly containing the fuel material for pulsed fusion events.

BACKGROUND

Nuclear fusion occurs when the atomic nuclei of two or more light atoms collide to make a heavier atom. Following the collision, the total mass of the new atom is less than that of the two atoms that formed it, and the “extra” mass is converted to energy according to the formula E=mc2. In order for fusion to occur, high temperatures and high pressures are required. Under these conditions, atoms are highly excited and are stripped of all their electrons (i.e., ionized), which forms a plasma. The high temperature gives the atoms more kinetic energy, resulting in more collisions. The high pressure causes the atoms to be closer together, making their collision more likely.

Pulsed fusion events are a type of nuclear fusion produced by inertial confinement or compression of a fuel element to very high pressure and temperature conditions in a technique commonly termed “z-pinch.” In typical z-pinch drivers, an axial current is applied across a diode assembly formed of a cylindrical array of small, electrically conducting wires disposed around a fuel element. The large voltage across the diode assembly produces very high temperature conditions that subsequently ionizes the material of the electrically conducting wires and produces the plasma. The cylindrical geometry of the wires in the diode assembly causes an inward compression of the wires with respect to the axis of the current, which confines the plasma around the fuel element. A magnetic field around the plasma further induces a high current through the plasma, which generates a Lorentz force on the fuel element to compress the fuel element to fusion conditions. As the plasma is highly conductive, the energy stored in the fuel element is quickly depleted as a result of the high current running through the plasma. Thus, the nuclear fusion that occurs in the z-pinch driver is often referred to as a “pulsed fusion event.”

The wire array for producing pulsed fusion events in z-pinch drivers has several weaknesses. In particular, a large number of wires are required to be carefully constructed in the diode assembly to produce a symmetrical plasma. An asymmetrical plasma results in Taylor instabilities, which disrupts the compression symmetry on the fuel element and results in non-fusion conditions. Thus, the wire array is time-consuming and complex to assemble. The precision necessary to construct the wire array combined with its complexity severely limit the frequency of pulsed fusion events able to be produced by a z-pinch driver to one event over multiple days. As should be understood, limits on the number of pulsed fusion events that are possible severely impacts potential applications for z-pinch technology.

Further, because the wire array of the diode assembly must be carefully constructed and inserted into a z-pinch driver in order to produce pulsed fusion events, the materials of the wires are limited to those that can be drawn to fine wires yet strong enough to form the symmetrical wire array. Typical materials used are tungsten and aluminum for the electrically conducting wires. Further applications for z-pinch machines would benefit from a wider selection of materials for the generated plasma.

Accordingly, what is needed is a fuel diode assembly for a z-pinch driver that is more efficient to construct for producing pulsed fusion events while decreasing the duration of time between pulsed fusion events produced by the z-pinch driver. It is also desired to provide a diode assembly that is efficiently made from electrically conducting materials disposed around the fuel element in addition to tungsten and aluminum.

SUMMARY

The present disclosure provides a diode assembly for producing a pulsed fusion event in a z-pinch driver. The diode assembly includes an inner core and a lithium metal outer sheath. The inner core is formed of a fusionable fuel source material including a lithium compound formed of one or more lithium isotopes and one or more hydrogen isotopes. The lithium metal outer sheath is integrally formed around the inner core and in a symmetrical relationship with the inner core by decomposing a surface of the fusionable fuel source material.

According to certain embodiments, the lithium compound of the inner core is selected from a group consisting of6LiD,6LiT,7LiD, and7LiT. In some embodiments, the inner core consists of the lithium compound.

According to certain embodiments, the symmetrical relationship is selected from the group consisting of: the inner core and the lithium metal outer sheath each being cylindrical such that the diode assembly is cylindrical, and the inner core and the lithium metal outer sheath each being a one-dimensional plate such that the diode assembly includes a layered plate arrangement.

According to certain embodiments, the diode assembly further includes a tamper disposed around the lithium metal outer sheath with the tamper including a non-conducting polymer layer disposed around the lithium metal outer sheath and a tamper layer disposed around the non-conducting polymer layer. According to this embodiment, the tamper layer may be selected from a group consisting of uranium, platinum, tungsten, niobium, molybdenum, osmium, rhenium, and combinations thereof.

According to certain embodiments, the diode assembly further includes a tamper layer disposed around the electrically conducting outer sheath with the tamper layer including an electrical conductance less than the electrical conductance of the electrically conducting outer sheath. According to this embodiment, the tamper layer may be selected from a group consisting of uranium, platinum, tungsten, niobium, molybdenum, osmium, rhenium, and combinations thereof. In certain embodiments, the tamper layer includes238U.

According to another embodiment of the disclosure, a method of forming a diode assembly for producing a pulsed fusion event in a z-pinch driver includes: providing a fusionable fuel source material including a lithium compound formed of one or more lithium isotopes and one or more hydrogen isotopes; heating the fusionable fuel source material under controlled conditions in a vacuumed environment such that a surface of the fusionable fuel source material decomposes to lithium metal and a hydrogen isotopic gas; and extracting the hydrogen isotopic gas from the vacuumed environment such that a lithium metal outer sheath is integrally formed around the fusionable fuel source material.

According to certain embodiments, the fusionable fuel source material is selected from a group consisting of6LiD,6LiT,7LiD, and7LiT.

According to certain embodiments, the controlled conditions include a vapor pressure ranging from about 2.2 torr to about 11.1 torr.

According to certain embodiments, the surface of the fusionable fuel source material is heated to a temperature ranging from about 400° C. to about 680° C.

According to certain embodiments, the surface of the fusionable fuel source material is heated to a temperature ranging from about 600° C. to about 660° C.

According to certain embodiments, the controlled conditions include a vapor pressure ranging from about 2.2 torr to about 11.1 torr and the surface of the fusionable fuel source material being heated to a temperature ranging from about 400° C. to about 680° C. According to this embodiment, the heating step may further include raising the vapor pressure of the vacuumed environment as the temperature of the surface of the fusionable fuel source material increases.

According to certain embodiments, the method further includes controlling a thickness of the lithium metal outer sheath between about ten microns and about 150 microns by selecting the controlled conditions to include a temperature between about 560° C. to about 660° C. and a heating time between about one hour to about three hours.

According to certain embodiments, the method further includes controlling a thickness of the lithium metal outer sheath such that the lithium metal outer sheath of the formed diode assembly includes a mass that is substantially equal to a mass of the fusionable fuel source material.

According to certain embodiments, the heating and extracting steps are performed in a sealed vessel having a separator disposed between the fusionable fuel source material and an interior surface of the sealed vessel.

