Editing Inertial electrostatic confinement (section)

==Designs with fields==
Several schemes attempt to combine [[magnetic confinement fusion|magnetic confinement]] and [[electrostatics|electrostatic]] fields with IEC. The goal is to eliminate the inner wire cage of the fusor, and the resulting problems.

===Polywell===

<!-- Deleted image removed: [[File:Polywell WB-6 complete.jpg|thumb|An example of a polywell's electromagnets]] -->
The polywell uses a magnetic field to trap electrons. When electrons or ions move into a dense field, they can be reflected by the magnetic mirror effect.<ref name="Mirror Systems 1969"/> A polywell is designed to trap electrons in the center, with a dense magnetic field surrounding them.<ref name="Carr, M. 2013"/><ref>"Vlasov–Poisson calculations of electron confinement times in Polywell(TM) devices using a steady-state particle-in-cell method". The DPP13 Meeting of The American Physical Society. Retrieved 2013-10-01.</ref><ref>"Electrostatic potential measurements and point cusp theories applied to a low beta polywell fusion device" PhD Thesis, Matthew Carr, 2013, The University of Sydney</ref> This is typically done using six electromagnets in a box. Each magnet is positioned so their poles face inward, creating a [[null (physics)|null point]] in the center. The electrons trapped in the center form a "virtual electrode"<ref name="bussard">{{cite journal |last1=Bussard |first1=R.W. |year=1991 |title=Some Physics Considerations of Magnetic Inertial-Electrostatic Confinement: A New Concept for Spherical Converging-flow Fusion |journal=Fusion Technology |volume=19 |issue=2 |page=273 |bibcode=1991FuTec..19..273B |doi=10.13182/FST91-A29364}}</ref> Ideally, this electron cloud accelerates ions to fusion conditions.<ref name="ReferenceA"/>

===Penning trap===
[[File:Penning Trap.svg|thumb|300px|Penning trap cross-section. Axis is vertical. Electrons orbit the center under DC electrostatic (blue) and DC magnetic (red) confinement. In this diagram the confined particles are positive; to confine electrons, the electrodes' polarities must be swapped.]]
A [[Penning trap]] uses both an electric and a magnetic field to trap particles, a magnetic field to confine particles radially and a quadrupole electric field to confine the particles axially.<ref>{{cite web |title=Penning Traps |url=https://web2.ph.utexas.edu/~iheds/IntroductionPlasmaPhysics/375%20P%207%20(Penning).pdf |access-date=2014-01-07 |url-status=live |archive-url=https://web.archive.org/web/20130120015434/http://www.ph.utexas.edu/~iheds/IntroductionPlasmaPhysics/375%20P%207%20(Penning).pdf |archive-date=2013-01-20}}</ref>

In a Penning trap fusion reactor, first the magnetic and electric fields are turned on. Then, electrons are emitted into the trap, caught and measured. The electrons form a virtual electrode similar to that in a polywell, described above. These electrons are intended to then attract ions, accelerating them to fusion conditions.<ref name="barnes">{{cite journal |last1=Barnes |first1=D. C. |last2=Nebel |first2=R. A. |last3=Turner |first3=Leaf |title=Production and application of dense Penning trap plasmas |journal=Physics of Fluids B: Plasma Physics |publisher=AIP Publishing |volume=5 |issue=10 |year=1993 |issn=0899-8221 |pages=3651–3660 |bibcode=1993PhFlB...5.3651B |doi=10.1063/1.860837}}</ref>

In the 1990s, researchers at [[LANL]] built a Penning trap to do fusion experiments. Their device (PFX) was a small (millimeters) and low power (one fifth of a [[tesla (unit)|tesla]], less than ten thousand volts) machine.<ref name="ReferenceB"/>

===Marble===

<!-- Deleted image removed: [[File:The multipole Ion-beam experiment magnet.png|thumbnail|The electromagnet used in the MIX system]] -->
MARBLE (multiple [[non-neutral plasma|ambipolar]] recirculating beam line experiment) was a device which moved electrons and ions back and forth in a line.<ref name="AlexPoster">"The Multiple Ambipolar Recirculating Beam Line Experiment" Poster presentation, 2011 US-Japan IEC conference, Dr. Alex Klein</ref> Particle beams were reflected using [[electrostatic lens|electrostatic optics]].<ref>"Dynamics of Ions in an Electrostatic Ion Beam Trap", http://www.weizmann.ac.il/conferences/frisno8/presentations05/thursday/Zajfman.pdf {{Webarchive|url=https://web.archive.org/web/20140108011658/http://www.weizmann.ac.il/conferences/frisno8/presentations05/thursday/Zajfman.pdf |date=2014-01-08}} Presentation, [[Daniel Zajfman]]</ref> These optics made static voltage surfaces in free space.{{citation needed|date=January 2014}} Such surfaces reflect only particles with a specific kinetic energy, while higher-energy particles can traverse these surfaces unimpeded, although not unaffected. Electron trapping and plasma behavior was measured by [[Langmuir probe]].<ref name="AlexPoster"/> Marble kept ions on orbits that do not intersect grid wires—the latter also improves the space charge limitations by multiple nesting of ion beams at several energies.<ref>{{cite web |title=Our Technology |website=Beam Fusion |url=http://www.beamfusion.org/technology/index.html |url-status=dead |archive-url=https://web.archive.org/web/20130406024952/http://www.beamfusion.org/technology/index.html |archive-date=2013-04-06}}</ref> Researchers encountered problems with ion losses at the reflection points. Ions slowed down when turning, spending much time there, leading to high [[electrical conductor|conduction]] losses.<ref>Alex Klein, in person interview, April 30, 2013</ref>

===MIX===

The multipole ion-beam experiment (MIX) accelerated ions and electrons into a negatively charged electromagnet.<ref name=mix/> Ions were focused using [[Dennis Gabor|Gabor]] lensing. Researcher had problems with a very thin ion-turning region very close to a solid surface<ref name=mix/> where ions could be conducted away.

===Magnetically insulated===

Devices have been proposed where the negative cage is magnetically insulated from the incoming plasmas.<ref>{{cite journal |arxiv=1510.01788 |title=Fusion in a magnetically-shielded-grid inertial electrostatic confinement device |first1=John |last1=Hedditch |first2=Richard |last2=Bowden-Reid |first3=Joe |last3=Khachan |journal=Physics of Plasmas |volume=22 |issue=10 |date=1 October 2015 |pages=102705 |bibcode=2015PhPl...22j2705H |doi=10.1063/1.4933213}}</ref>