Astronomy:Lattice confinement fusion

Short description: Type of nuclear fusion

Lattice confinement fusion (LCF) is a type of nuclear fusion in which deuteron-saturated metals are exposed to gamma radiation or ion beams, such as in an IEC fusor, avoiding the confined high-temperature gasses used in other methods of fusion.^[1]^[2]

History

In 2020, a team of NASA researchers seeking a new energy source for deep-space exploration missions published the first paper describing a method for triggering nuclear fusion in the space between the atoms of a metal solid, an example of screened fusion.^[3] The experiments did not produce self-sustaining reactions, and the electron source itself was energetically expensive.^[1]

Technique

The reaction is fueled with deuterium, a widely available non-radioactive hydrogen isotope composed of one proton, one neutron, and one electron. The deuterium is confined in the space between the atoms of a metal solid such as erbium or titanium. Erbium can indefinitely maintain 10²³ cm⁻³ deuterium atoms (deuterons) at room temperature. The deuteron-saturated metal forms an overall neutral plasma. ^{[dubious – discuss]} The electron density of the metal reduces the likelihood that two deuterium nuclei will repel each other as they get closer together.^[1]

A dynamitron electron-beam accelerator generates an electron beam that hits a tantalum target and produces gamma rays, irradiating titanium deuteride or erbium deuteride. A gamma ray of about 2.2 megaelectron volts (MeV) strikes a deuteron and splits it into proton and neutron. The neutron collides with another deuteron. This second, energetic deuteron can experience screened fusion or a stripping reaction.^[1]

Although the lattice is notionally at room temperature, LCF creates an energetic environment inside the lattice where individual atoms achieve fusion-level energies.^[3] Heated regions are created at the micrometer scale.

Screened fusion

The energetic deuteron fuses with another deuteron, yielding either a ³helium nucleus and a neutron or a ³hydrogen nucleus and a proton. These fusion products may fuse with other deuterons, creating an alpha particle, or with another ³helium or ³hydrogen nucleus. Each releases energy, continuing the process.^[1]

Stripping reaction

In a stripping reaction, the metal strips a neutron from accelerated deuteron and fuses it with the metal, yielding a different isotope of the metal.^[1] If the produced metal isotope is radioactive, it may decay into another element, releasing energy in the form of ionizing radiation in the process.

Palladium-silver

A related technique pumps deuterium gas through the wall of a palladium-silver alloy tubing. The palladium is electrolytically loaded with deuterium. In some experiments this produces fast neutrons that trigger further reactions.^[1] Other experimenters (Fralick et al.) also made claims of anomalous heat produced by this system.

Comparison to other fusion techniques

Pyroelectric fusion has previously been observed in erbium hydrides. A high-energy beam of deuterium ions generated by pyroelectric crystals was directed at a stationary, room-temperature ErD
2 or ErT
2 target, and fusion was observed.^[2]

In previous fusion research, such as inertial confinement fusion (ICF), fuel such as the rarer tritium is subjected to high pressure for a nano-second interval, triggering fusion. In magnetic confinement fusion (MCF), the fuel is heated in a plasma to temperatures much higher than those at the center of the Sun. In LCF, conditions sufficient for fusion are created in a metal lattice that is held at ambient temperature during exposure to high-energy photons.^[3] ICF devices momentarily reach densities of 10²⁶ cc⁻¹, while MCF devices momentarily achieve 10¹⁴.

Lattice confinement fusion requires energetic deuterons and is therefore not cold fusion.^[1]

Lattice confinement fusion is used as a method to increase the cathode fuel density of inertial electrostatic fusion devices such as a Farnsworth-Hirsch fusor. This increases the probability of fusion events occurring and therefore the radiation output produced. In applications where fusors are used as X-ray, neutron, or proton radiation source, lattice confinement fusion improves the energy efficiency of the device. ^{[citation needed]}