Polywell

These strikes conduct mass and energy away from the plasma, as well as spall off metal ions into the gas, which cools it.

In June 2014 EMC2 published a preprint[3] providing (1) x-ray and (2) flux loop measurements that the diamagnetic effect will impact the external field.

The solution, suggested by Robert Bussard and Oleg Lavrentiev,[19] was to replace the negative cage with a "virtual cathode" made of a cloud of electrons.

Inside the MaGrid, single electrons travel straight through the null point, due to their infinite gyroradius in regions of no magnetic field.

The collision rate may vary greatly across the system:[citation needed] Critics claimed that both the electrons and ion populations have bell curve distribution;[31] that the plasma is thermalized.

There are several general criticisms of the Polywell: Todd Rider (a biological engineer and former student of plasma physics)[41] calculated that X-ray radiation losses with this fuel would exceed fusion power production by at least 20%.

[48] Other studies disproved some of the assumptions made by Rider and Nevins, arguing the real fusion rate and the associated recirculating power (needed to overcome the thermalizing effect and sustain the non-Maxwellian ion profile) could be estimated only with a self-consistent collisional treatment of the ion distribution function, lacking in Rider's work.

The energetic alpha particles (up to a few MeV) generated by the aneutronic fusion reaction would exit the MaGrid through the six axial cusps as cones (spread ion beams).

[52][53] The first proposal to combine this configuration with an electrostatic potential well in order to improve electron confinement was made by Oleg Lavrentiev in 1975.

In 1995 he sent a letter to the US Congress stating that he had only supported Tokamaks in order to get fusion research sponsored by the government, but he now believed that there were better alternatives.

While Bussard did not publicly document the reasoning underlying this estimate,[61] if true, it would enable a model only ten times larger to be useful as a fusion power plant.

"[59] An extra $900k of Office of Naval Research funding allowed the program to continue long enough to reach WB-6 testing in November 2005.

He noted, "We are probably the only people on the planet who know how to make a real net power clean fusion system"[58] He proposed to rebuild WB-6 more robustly to verify its performance.

He wrote "The only small scale machine work remaining, which can yet give further improvements in performance, is test of one or two WB-6-scale devices but with "square" or polygonal coils aligned approximately (but slightly offset on the main faces) along the edges of the vertices of the polyhedron.

[65] In 2007, Steven Chu, Nobel laureate and former United States Secretary of Energy, answered a question about polywell at a tech talk at Google.

[71] In September 2008 the Naval Air Warfare Center publicly pre-solicited a contract for research on an Electrostatic "Wiffle Ball" Fusion Device.

"[89] In June EMC2 demonstrated for the first time that the electron cloud becomes diamagnetic in the center of a magnetic cusp configuration when beta is high, resolving an earlier conjecture.

Park presented these findings at various universities,[90][91][92][93][94] the Annual 2014 Fusion Power Associates meeting[95] and the 2014 IEC conference.

On May 2, Jaeyoung Park delivered a lecture at Khon Kaen University in Thailand, claiming that the world has so underestimated the timetable and impact that practical and economic fusion power will have, that its ultimate arrival will be highly disruptive.

In June 2019, the results of long-running experiments at the University of Sydney (USyd) were published in PhD thesis form by Richard Bowden-Reid.

Exploring this problem, Bowden-Reid developed new field equations for the device that explained the potential well without electrode formation, and demonstrated that this matched both their results and those of previous experiments.

[102] Further, exploring the overall mechanism of the virtual electrode concept demonstrated that its interactions with the ions and itself would make it "leak" at a furious rate.

Further, it is shown that the existence of potential wells reported in previous publications can be explained without the requirement of a virtual cathode produced by trapped electrons.

Moreover, it is shown that potential wells, which produce electron confinement and heating from virtual cathodes, no longer exist with increasing plasma density.

[112] In November 2012, Trend News Agency reported that the Atomic Energy Organization of Iran had allocated "$8 million"[113] to inertial electrostatic confinement research and about half had been spent.

The funded group published a paper in the Journal of Fusion Energy, stating that particle-in-cell simulations of a polywell had been conducted.

The study suggested that well depths and ion focus control can be achieved by variations of field strength, and referenced older research with traditional fusors.

This was funded through the National Defense Science and Engineering Graduate Fellowship and was presented at the 2013 American Physical Society conference.

The MaGrid was made of a unique diamond shaped hollow wire, into which an electric current and a liquid coolant flowed.

Fusion One Corporation was a US organization founded by Dr. Paul Sieck (former Lead Physicist of EMC2), Dr. Scott Cornish of the University of Sydney, and Randall Volberg.

A homemade fusor
Farnsworth–Hirsch fusor during operation in so called "star mode" characterized by "rays" of glowing plasma which appear to emanate from the gaps in the inner grid.
Figure 1 : Illustration of the basic mechanism of fusion in fusors. (1) The fusor contains two concentric wire cages. The cathode (blue) is inside the anode (red). (2) Positive ions are attracted to the inner cathode. The electric field does work on the ions heating them to fusion conditions. (3) The ions miss the inner cage. (4) The ions collide in the center and may fuse. [ 1 ] [ 2 ]
Figure 3 : Polywell cusps. The line cusp runs along the seam between two electromagnets. The funny cusp is the cusp between three magnets, running along the corners. The point cusp lies in the middle of one electromagnet.
Figure 2 : A plot of the magnetic field generated by the MaGrid inside a polywell. The null point is marked in red in the center.
Figure 1 : Sketch of a MaGrid in a polywell
Figure 4 : Illustration of single electron motion inside the polywell. It is based on figures from "Low beta confinement in a polywell modeled with conventional point cusp theories" but is not an exact copy.
Figure 5 : Thermalized plasma ion energy distribution inside a polywell. [ 31 ] This model assumes a maxwellian ion population, broken into different groups. (1) The ions which do not have enough energy to fuse, (2) the ions at the injection energy (3) the ions that have so much kinetic energy that they escape.
Figure 6 : Non-thermalized plasma energy distribution inside a polywell. [ 35 ] It is argued that the region of unmagnetized space leads to electron scattering, this leads to a monoenergetic distribution with a cold electron tail. This is supported by 2 dimensional particle-in-cell simulations.
Figure 7 : Plot of the cross section of different fusion reactions.