page_title: Polywell
section_title: Fusor
hierarchical_section_title: Polywell / Mechanism / Fusor
caption_attribution_description: English: A homemade IEC fusion reactor created by a high school student, William Jack, clearly showing the plasma and poissors emanating from it.
context_page_description: The polywell was a proposed design for a fusion reactor using an electric field to heat ions to fusion conditions. Research was conducted and prototypes built between the 1960s and 2019. The concept was taken further by physicist Robert Bussard. His company, EMC2, Inc., developed prototypical devices for the U.S. Navy. Current research by the University of Sydney seems to show that the design is impractical in practice.
  The design was related to the fusor, the high beta fusion reactor, the magnetic mirror, and the biconic cusp. A set of electromagnets generates a magnetic field that traps electrons. This creates a negative voltage, which attracts positive ions. As the ions accelerate towards the negative center, their kinetic energy rises. Ions that collide at high enough energies can fuse.
context_section_description: A Farnsworth-Hirsch fusor consists of two wire cages, one inside the other, often referred to as grids, that are placed inside a vacuum chamber. The outer cage has a positive voltage versus the inner cage. A fuel, typically, deuterium gas, is injected into this chamber. It is heated past its ionization temperature, making positive ions. The ions are positive and move towards the negative inner cage. Those that miss the wires of the inner cage fly through the center of the device at high speeds and can fly out the other side of the inner cage. As the ions move outward, a Coulomb force impels them back towards the center. Over time, a core of ionized gas can form inside the inner cage. Ions pass back and forth through the core until they strike either the grid or another nucleus. Most nucleus strikes do not result in fusion. Grid strikes can raise the temperature of the grid as well as eroding it. These strikes conduct mass and energy away from the plasma, as well as spall off metal ions into the gas, which cools it.
  In fusors, the potential well is made with a wire cage. Because most of the ions and electrons fall into the cage, fusors suffer from high conduction losses. Hence, no fusor has come close to energy break-even.
caption: A homemade fusor
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