The Prairie View (PV) Rotamak is a plasma physics experiment at Prairie View A&M University. [1] The experiment studies magnetic plasma confinement to support controlled nuclear fusion experiments. Specifically, the PV Rotamak can be used as either a spherical tokamak or a field-reversed configuration. Some time between 2015 and 2017, most personnel moved on to advanced career opportunities. [2] In 2017, a Final Report to Department of Energy (DOE) was prepared and submitted by Dr. Saganti of PVAMU on the entire research work supported by DOE for 12 years. [3]
FRCs and spherical tokamaks are of interest to the plasma physics community because of their confinement properties and their small size. While most large fusion experiments in the world are tokamaks, FRCs and STs are seen as a viable alternative because of their higher Beta, meaning the same power output could be produced from a smaller volume of plasma, and their good plasma stability.
The PV Rotamak was built in 2001, largely out of components of the disassembled Flinders Rotamak. [4] The PV Rotamak has furnished the experimental data to produce more than 12 academic papers on plasma physics as of 2017. [5] More recent pictorial depictions and short videos with all the equipment layout can be found from Saganti-PVSO Google Site. [6]
The experimental apparatus consists of a vacuum vessel, electromagnetic coils, a high-power radio-frequency (RF) generation system to run the rotating magnetic field (RMF), and diagnostics. The vacuum vessel is made of Pyrex glass and is 80 cm long and 40 cm in diameter. [7] The electromagnetic coils can produce up to 230 Gauss (0.023 Tesla) magnetic fields center of the vacuum vessel. Another electromagnetic coil running through the axis of the vacuum vessel can produce the magnetic field necessary to make the apparatus a spherical tokamak. The RF generation system can deliver 400 kW of power to the plasma in the form of a rotating magnetic field at a frequency of 500 kHz. The RMF can run for 40ms at a time.
The electron density during a typical discharge of the PV Rotamak is . [7] This is about 1000x lower than a burning thermonuclear plasma would have to achieve. [8] The electron temperature during a typical discharge is 10-30eV, again about 1000x lower than a burning thermonuclear plasma. The power into the plasma is 400 kW, compared to 10s of MW in large Tokamaks.
Early experiments in the PV Rotamak sought to characterize the difference between FRC and Spherical tokamak configurations. [7] They found that the inclusion of a toroidal magnetic field (turning the FRC into an ST) led to increased particle confinement and performance.
Later experiments sought to characterize and mitigate the n=1 tilt mode of the FRC. [9] This is an instability of FRCs that can cause loss of the plasma. They measured the stability boundaries of this mode, and found that an additional electromagnetic coil around the middle of the machine pinched the FRC into two separate pieces, mitigating the tilt mode.
Recent (2015) experiments on the PV Rotamak dealt with heating the plasma with microwaves. [10] 6 kW of power was injected into the plasma. Researchers found that they were able to drive current with the microwaves relatively efficiently, but this small amount of power was not sufficient to appreciably change the density or temperature of the plasma.
A stellarator is a plasma device that relies primarily on external magnets to confine a plasma. Scientists researching magnetic confinement fusion aim to use stellarator devices as a vessel for nuclear fusion reactions. The name refers to the possibility of harnessing the power source of the stars, such as the Sun. It is one of the earliest fusion power devices, along with the z-pinch and magnetic mirror.
The Levitated Dipole Experiment (LDX) was an experiment investigating the generation of fusion power using the concept of a levitated dipole. The device was the first of its kind to test the levitated dipole concept and was funded by the US Department of Energy. The machine was also part of a collaboration between the MIT Plasma Science and Fusion Center and Columbia University, where another dipole experiment, the Collisionless Terrella Experiment (CTX), was located.
A field-reversed configuration (FRC) is a type of plasma device studied as a means of producing nuclear fusion. It confines a plasma on closed magnetic field lines without a central penetration. In an FRC, the plasma has the form of a self-stable torus, similar to a smoke ring.
A spheromak is an arrangement of plasma formed into a toroidal shape similar to a smoke ring. The spheromak contains large internal electric currents and their associated magnetic fields arranged so the magnetohydrodynamic forces within the spheromak are nearly balanced, resulting in long-lived (microsecond) confinement times without external fields. Spheromaks belong to a type of plasma configuration referred to as the compact toroids. A spheromak can be made and sustained using magnetic flux injection, leading to a dynomak.
The Small Tight Aspect Ratio Tokamak, or START was a nuclear fusion experiment that used magnetic confinement to hold plasma. START was the first full-sized machine to use the spherical tokamak design, which aimed to greatly reduce the aspect ratio of the traditional tokamak design.
DIII-D is a tokamak that has been operated since the late 1980s by General Atomics (GA) in San Diego, USA, for the U.S. Department of Energy. The DIII-D National Fusion Facility is part of the ongoing effort to achieve magnetically confined fusion. The mission of the DIII-D Research Program is to establish the scientific basis for the optimization of the tokamak approach to fusion energy production.
The National Spherical Torus Experiment (NSTX) is a magnetic fusion device based on the spherical tokamak concept. It was constructed by the Princeton Plasma Physics Laboratory (PPPL) in collaboration with the Oak Ridge National Laboratory, Columbia University, and the University of Washington at Seattle. It entered service in 1999. In 2012 it was shut down as part of an upgrade program and became NSTX-U, for Upgrade.
The beta of a plasma, symbolized by β, is the ratio of the plasma pressure (p = nkBT) to the magnetic pressure (pmag = B²/2μ0). The term is commonly used in studies of the Sun and Earth's magnetic field, and in the field of fusion power designs.
An edge-localized mode (ELM) is a disruptive instability occurring in the edge region of a tokamak plasma due to the quasi-periodic relaxation of a transport barrier previously formed during a transition from low to high-confinement mode. This phenomenon was first observed in the ASDEX tokamak in 1981. Diamagnetic effects in the model equations expand the size of the parameter space in which solutions of repeated sawteeth can be recovered compared to a resistive MHD model. An ELM can expel up to 20 percent of the reactor's energy.
The Helically Symmetric Experiment, is an experimental plasma confinement device at the University of Wisconsin–Madison, with design principles that are intended to be incorporated into a fusion reactor. The HSX is a modular coil stellarator which is a toroid-shaped pressure vessel with external electromagnets which generate a magnetic field for the purpose of containing a plasma. It began operation in 1999.
Compact toroids are a class of toroidal plasma configurations that are self-stable, and whose configuration does not require magnet coils running through the center of the toroid. They are studied primarily in the field of fusion energy, where the lack of complex magnets and a simple geometry may allow the construction of dramatically simpler and less expensive fusion reactors.
A spherical tokamak is a type of fusion power device based on the tokamak principle. It is notable for its very narrow profile, or aspect ratio. A traditional tokamak has a toroidal confinement area that gives it an overall shape similar to a donut, complete with a large hole in the middle. The spherical tokamak reduces the size of the hole as much as possible, resulting in a plasma shape that is almost spherical, often compared to a cored apple. The spherical tokamak is sometimes referred to as a spherical torus and often shortened to ST.
The GLAss Spherical Tokamak is a name given to a set of small spherical tokamaks located in Islamabad, Pakistan. They were developed by the Pakistan Atomic Energy Commission (PAEC) as part of the National Tokamak Fusion Program (NTFP) in 2008 and are primarily used for teaching and training purposes.
COMPASS, short for Compact Assembly, is a compact tokamak fusion energy device originally completed at the Culham Science Centre in 1989, upgraded in 1992, and operated until 2002. It was designed as a flexible research facility dedicated mostly to plasma physics studies in circular and D-shaped plasmas.
The Princeton field-reversed configuration (PFRC) is a series of experiments in plasma physics, an experimental program to evaluate a configuration for a fusion power reactor, at the Princeton Plasma Physics Laboratory (PPPL). The experiment probes the dynamics of long-pulse, collisionless, low s-parameter field-reversed configurations (FRCs) formed with odd-parity rotating magnetic fields. FRCs are the evolution of the Greek engineer's Nicholas C. Christofilos original idea of E-layers which he developed for the Astron fusion reactor. The PFRC program aims to experimentally verify the physics predictions that such configurations are globally stable and have transport levels comparable with classical magnetic diffusion. It also aims to apply this technology to the Direct Fusion Drive concept for spacecraft propulsion.
TJ-II is a flexible Heliac installed at Spain's National Fusion Laboratory.
The Star Thrust Experiment (STX) was a plasma physics experiment at the University of Washington's Redmond Plasma Physics Laboratory which ran from 1999 to 2001. The experiment studied magnetic plasma confinement to support controlled nuclear fusion experiments. Specifically, STX pioneered the possibility of forming a Field-reversed configuration (FRC) by using a Rotating Magnetic Field (RMF).
The Translation Confinement Sustainment experiment (TCS) was a plasma physics experiment at the University of Washington's Redmond Plasma Physics Laboratory from 2002 until 2009. The experiment studied magnetic plasma confinement to support controlled nuclear fusion experiments. Specifically, TCS pioneered the sustainment and heating of a Field-Reversed Configuration (FRC) by Rotating Magnetic Field (RMF).
Wendelstein 7-AS was an experimental stellarator which was in operation from 1988 to 2002 by the Max Planck Institute for Plasma Physics (IPP) in Garching. It was the first of a new class of advanced stellarators with modular coils, designed with the goal of developing a nuclear fusion reactor to generate electricity.
The Tokamak Physics Experiment (TPX) was a plasma physics experiment that was designed but not built. It was designed by an inter-organizational team in the USA led by Princeton Plasma Physics Laboratory. The experiment was designed to test theories about how Tokamaks would behave in a high-performance, steady-state regime.
