Polywell

The polywell is a type of nuclear fusion reactor that uses an electric field to heat ions to fusion conditions. It is closely 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.5252.204-9504 DISCLOSURE OF CONTRACT INFORMATION (NAVAIR) (JAN 2007)(a) The Contractor shall not release to anyone outside the Contractor's organization any unclassified information (e.g., announcement of contract award), regardless of medium (e.g., film, tape, document), pertaining to any part of this contract or any program related to this contract, unless the Contracting Officer has given prior written approval.(b) Requests for approval shall identify the specific information to be released, the medium to be used, and the purpose for the release. The Contractor shall submit its request to the Contracting Officer at least ten (10) days before the proposed date for release.(c) The Contractor agrees to include a similar requirement in each subcontract under this contract. Subcontractors shall submit requests for authorization to release through the prime contractor to the Contracting Officer. The polywell is a type of nuclear fusion reactor that uses an electric field to heat ions to fusion conditions. It is closely 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. The polywell is one of many devices that use an electric field to heat ions to fusion conditions. This branch of fusion research is known as inertial electrostatic confinement. The polywell was developed by physicist Robert Bussard, as an improvement over the fusor. His company, EMC2, Inc., developed prototypical devices for the U.S. Navy. 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. 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, they feel a Coulomb force that directs 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. 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. The main problem with the fusor is that the inner cage conducts away too much energy and mass. The solution, suggested by Robert Bussard and Oleg Lavrentiev, was to replace the negative cage with a 'virtual cathode' made of a cloud of electrons. A polywell consists of several parts. These are put inside a vacuum chamber The magnetic energy density required to confine electrons is far smaller than that required to directly confine ions, as is done in other fusion projects such as ITER.