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'''Trisops''' was an experimental machine for the study of [[Magnetic confinement fusion|magnetic confinement]] of [[Plasma (physics)|plasmas]] with the ultimate goal of producing [[fusion power]]. The configuration was a variation of a [[Magnetic confinement fusion#Compact toroids|compact toroid]], a [[torus|toroidal]] ([[doughnut]]-shaped) structure of plasma and magnetic fields with no [[electromagnetic coil]]s or [[electrode]]s penetrating the center. It lost funding in its original form in 1978.

The configuration is produced by combining two individual toroids produced by two conical θ pinch guns, located at either end of a length of [[Pyrex]] pipe with a constant guide [[magnetic field]]. The toroidal currents in the toroids are in opposite directions, so that they repel each other. After coming to an equilibrium, they are compressed [[Adiabatic process|adiabatically]] by increasing the external field.

== Force free plasma vortices ==
Force free plasma vortices have uniform [[magnetic helicity]] and therefore are stable against many instabilities. Typically, the current decays faster in the colder regions until the gradient in helicity is large enough to allow a turbulent redistribution of the current.

Force free vortices follow these equations:
:<math> 
\begin{align}
 \vec{\nabla} \times \vec{B} = \alpha\vec{B} \\
\vec{v} = \pm\beta\vec{B}
\end{align}
</math>

The first equation describes a [[Lorentz force]]-free fluid: the <math> \vec{j} \times \vec{B} </math> forces are everywhere zero. For a laboratory plasma α is a constant and β is a scalar function of spatial coordinates.

The magnetic flux surfaces are toroidal, with the current being totally [[Toroidal and poloidal|toroidal]] at the core of the torus and totally [[Toroidal and poloidal|poloidal]] at the surface of the torus. This is similar to the field configuration of a [[tokamak]], except that the field-producing coils are simpler and do not penetrate the plasma torus.

Unlike most plasma structures, the [[Lorentz force]] and the [[Magnus effect|Magnus force]], <math> \rho\vec{\nabla} \times \vec{v} </math>, play equivalent roles. <math>\rho </math> is the mass density.

== Project ==
Dr. Daniel Wells, while working on the [[Stellarator]] at the [[Princeton Plasma Physics Laboratory]] in the 1960s conceived of colliding and then compressing stable force free plasma toroids to produce conditions needed for thermonuclear fusion. The name, Trisops, is an [[acronym]] for Thermonuclear Reactor In Support of [[Project Sherwood]]. He later moved to the [[University of Miami]] where he set up the Trisops machine, supported by the [[National Science Foundation]] and [[Florida Power and Light]].

The project continued until 1978, when the [[National Science Foundation]] (NSF) discontinued the grant and the [[United States Department of Energy]] (DOE) did not pick up the support.

== Machine ==
[[File:Trisops machine.svg|300px|right|Schematic diagram of Trisops machine used for creation and secondary compression of plasma vortex structures. Machine length is about 2m.]]

The fourth and final version of the Trisops machine consisted of DC mirror coils producing a 0.5&nbsp;[[Tesla (unit)|T]] guide field, two conical θ-pinch guns which produced two counter-rotating plasma vortices inside a pyrex vacuum chamber. The vortices approached each other, collided, repelled each other, and finally came to rest. At that time the compression coils produced a 3.5&nbsp;T field with a quarter-cycle rise time of 10&nbsp;μs.

== Results ==
The compressed rings retained their structure for 5&nbsp;μs, with a density of 2 x 10<sup>17</sup>&nbsp;cm<sup>−3</sup>, an ion temperature of 5&nbsp;keV, an electron temperature of 300&nbsp;eV. Defunding prevented further measurements to resolve the discrepancy between the above figures, and the plasma electron-ion temperature equilibration time of 1&nbsp;μs.

== Followup ==
The project lost funding in 1978. The machine was disassembled and remained at the [[University of Miami]] until 1997. Then, the machine was moved to [[Lanham, Maryland]] and reassembled for the CMTX project (see reference). {{As of|2024}}, the status of the project and the machine are unknown.

== References ==
* {{cite journal |last1=Wells |first1=D. R. |last2=Davidson |first2=J. |last3=Phadke |first3=L. G. |last4=Hirschberg |first4=J. G. |last5=Ziajka |first5=P. E. |last6=Tunstall |first6=J. |title=High-Temperature, High-Density Plasma Production by Vortex-Ring Compression |journal=Physical Review Letters |publisher=American Physical Society (APS) |volume=41 |issue=3 |date=1978-07-17 |issn=0031-9007 |doi=10.1103/physrevlett.41.166 |pages=166–170 |bibcode=1978PhRvL..41..166W}}
* [https://web.archive.org/web/20070930162422/http://www.rsiprinceton.com/pubs/APS%20DPP97.pdf CMTX Project], Nov. 1997

{{Fusion power}}

[[Category:Magnetic confinement fusion devices]]