Polywell

Polywell (Greek -engl. Approximately " multiwell ") is a nuclear fusion reactor concept, which comes from Robert W. Bussard. It belongs to the so-called Inertial Electrostatic Confinement (IEC ) fusion concepts such as the Farnsworth - Hirsch Fusor, because these materials destined for fusion ions are held together by an electric field. This field is not generated by high-voltage electrode, but by a cloud of electrons which in turn is enclosed in a more or less spherically symmetrical magnetic field.

The Polywell development work is carried out by the EMC2 Fusion Development Corporation and funded by the U.S. Navy. As intended usage so far primarily space propulsion, but also power generation were called.

Description

In a high- vacuum container having a number of identical, spatially three-dimensionally arranged annular coils generates a centrally symmetric magnetic field. An electron cloud is enclosed by the field in the manner of the magnetic mirrors to form an electric potential well. Positively charged ions are supplied to this region, accelerated by the potential gradient towards the center and are on closed orbits circulate so long that carried a sufficient number of nuclear fusion reactions in their clashes. Details about the type and arrangement of the electron and ion sources have not yet been published.

Physical observations

The accumulation of electrons and ions in the electrostatic fusion devices is not strictly comparable with the thermal plasma of other fusion concepts such as fusion by magnetic confinement or inertial confinement fusion. In these the plasma by collisions of neutral atoms or molecules arises with each other, so it is electrically neutral and thermally in equilibrium. In contrast, a low Polywell etc. excess of electrons is necessary to make the potential well for ions including the plasma is thus not neutral. It is also not in thermal equilibrium, so do not be described by a temperature because electrons and ions coming from different sources with given kinetic energy and move around in the field with spatially dependent and spatially directed speeds.

Near the center of the potential well occurs relatively high ion velocities. Therefore, energy loss of the plasma can be important by bremsstrahlung. This would be particularly important in the case of the boron -11 proton fusion reaction (see fusion reactor # Other fuels ), their use has been proposed Buzzard, because it does not produce free neutrons. He argued that the losses by bremsstrahlung would be also with this fuel only 1/ 12 of the fusion energy produced because of the high speeds in the center and the resulting low cross section for the ion Coulombstöße a significant deceleration made ​​unlikely there. On the other hand put Todd Rider 1995 is that the losses by bremsstrahlung with this fuel would exceed the production of fusion energy by at least 20 %.

Experiments and results

Buzzard reported in 2006 on the experimental set- WB -6 ( " Whiffleball 6"). This had six ring coils arranged on the surfaces of an imaginary cube (diameter about 30 cm). With WB -6 up to 1 billion deuterium -deuterium fusion reactions have been achieved per second. This corresponds to a fusion power of about 0.6 milliwatts; the electrical power requirements of the equipment while attempting expected to have been at least a few hundred watts.

The plants WB -7 and WB -8 were then built and operated at EMC2. Maybe ( to refer only vaguely of a map) were at least in WB -7 to get the ball closer to symmetry, eight coils in octahedral or 12 coils used in dodecahedral arrangement. EMC2 declines with regard to the rights of the Principal U.S. Navy to publish full details and measurement results. The apparatus WB -8, at the time (2011) seems to be the experimenter runs should show excellent plasma confinement properties, according to report of the company.

According to a Bussard reactor with a radius of 1.5 meters would achieve a net energy gain of many megawatts.