Inertial electrostatic confinement

Inertial electrostatic confinement is a branch of fusion research that uses an electric field to elevate a plasma to fusion conditions. Electric fields can do work on charged particles (either ions or electrons), heating/confining them to fusion conditions. This is typically done in a sphere, with material moving radially inward, but can also be done in a cylindrical or beam geometry. The electric field can be generated using a wire grid or a non-neutral plasma cloud. Inertial electrostatic confinement is a branch of fusion research that uses an electric field to elevate a plasma to fusion conditions. Electric fields can do work on charged particles (either ions or electrons), heating/confining them to fusion conditions. This is typically done in a sphere, with material moving radially inward, but can also be done in a cylindrical or beam geometry. The electric field can be generated using a wire grid or a non-neutral plasma cloud. For every volt that an ion is accelerated across, its kinetic energy gain correspond to increase of temperature of 11,604 kelvins. For example, a typical magnetic confinement fusion plasma is 15 keV, or 170 megakelvin. An ion with a charge of one can reach this temperature by being accelerated across a 15,000 V drop. In fusors, the voltage drop is made with a wire cage. However high conduction losses occur in fusors because most ions fall into the cage before fusion can occur. This prevents current fusors from ever producing net power. Mark Oliphant adapts Cockcroft and Walton's particle accelerator at the Cavendish Laboratory to create Tritium and Helium-3 by nuclear fusion. Three researchers at LANL including Jim Tuck first explored the idea, theoretically, in a 1959 paper. The idea had been proposed by a colleague. The concept was to capture electrons inside a positive cage. The electrons would accelerate the ions to fusion conditions. Other concepts were being developed which would later merge into the IEC field. These include the publication of the Lawson criterion by John D. Lawson in 1957 in England. This puts on minimum criteria on power plant designs which do fusion using hot Maxwellian plasma clouds. Also, work exploring how electrons behave inside the Biconic cusp, done by Harold Grad group at the Courant Institute in 1957. A biconic cusp is a device with two alike magnetic poles facing one another (i.e. north-north). Electrons and ions can be trapped between these. In his work with vacuum tubes, Philo Farnsworth observed that electric charge would accumulate in regions of the tube. Today, this effect is known as the Multipactor effect. Farnsworth reasoned that if ions were concentrated high enough they could collide and fuse. In 1962, he filed a patent on a design using a positive inner cage to concentrate plasma, in order to achieve nuclear fusion. During this time, Robert L. Hirsch joined the Farnsworth Television labs and began work on what became the fusor. Hirsch patented the design in 1966 and published the design in 1967. The Hirsch machine was a 17.8 cm diameter machine with 150 kV voltage drop across it and used ion beams to help inject material. Simultaneously, a key plasma physics text was published by Lyman Spitzer at Princeton in 1963. Spitzer took the ideal gas laws and adapted them to an ionized plasma, developing many of the fundamental equations used to model a plasma. Meanwhile, Magnetic mirror theory and direct energy conversion were developed by Richard F. Post's group at LLNL. A magnetic mirror or magnetic bottle, is similar to a biconic cusp except that the poles are reversed. In 1980 Robert W. Bussard developed a cross between a fusor and magnetic mirror, the polywell. The idea was to confine a non-neutral plasma using magnetic fields. This would, in turn, attract ions. This idea had been published previously, notably by Oleg Lavrentiev in Russia. Bussard patented the design and received funding from Defense Threat Reduction Agency, DARPA and the US Navy to develop the idea. Bussard and Nicholas Krall published theory and experimental results in the early nineties. In response, Todd Rider at MIT, under Lawrence Lidsky developed general models of the device. Rider argued that the device was fundamentally limited. That same year, 1995, William Nevins at LLNL published a criticism of the polywell. Nevins argued that the particles would build up angular momentum, causing the dense core to degrade.