Princeton field-reversed configuration experiment

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One rotating magnetic field pulse of the PFRC 2 device during an experiment PFRC 2 pulse.jpg
One rotating magnetic field pulse of the PFRC 2 device during an experiment

The Princeton field-reversed configuration experiment (PFRC) is a plasma physics 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, [1] low s-parameter [2] field-reversed configurations (FRCs) formed with odd-parity rotating magnetic fields. [3] [4] It aims to experimentally verify the physics predictions that such configurations are globally stable and have transport levels comparable with classical magnetic diffusion. [2] It also aims to apply this technology to the Direct Fusion Drive concept for spacecraft propulsion.

Fusion power type of electricity generation

Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices designed to harness this energy are known as fusion reactors.

Princeton Plasma Physics Laboratory research institute

Princeton Plasma Physics Laboratory (PPPL) is a United States Department of Energy national laboratory for plasma physics and nuclear fusion science. Its primary mission is research into and development of fusion as an energy source.

Field-reversed configuration Magnetic confinement fusion reactor

A field-reversed configuration (FRC) is a type of plasma device that 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.

Contents

History

The PFRC was initially funded by the United States Department of Energy. Early in its operation it was contemporary with such RMF-FRCs as the Translation Confinement Sustainment experiment (TCS) and the Prairie View Rotamak (PV Rotamak).

United States Department of Energy Cabinet-level department of the United States government

The United States Department of Energy (DOE) is a cabinet-level department of the United States Government concerned with the United States' policies regarding energy and safety in handling nuclear material. Its responsibilities include the nation's nuclear weapons program, nuclear reactor production for the United States Navy, energy conservation, energy-related research, radioactive waste disposal, and domestic energy production. It also directs research in genomics; the Human Genome Project originated in a DOE initiative. DOE sponsors more research in the physical sciences than any other U.S. federal agency, the majority of which is conducted through its system of National Laboratories. The agency is administered by the United States Secretary of Energy, and its headquarters are located in Southwest Washington, D.C., on Independence Avenue in the James V. Forrestal Building, named for James Forrestal, as well as in Germantown, Maryland.

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).

The Prairie View (PV) Rotamak is a plasma physics experiment at Prairie View A&M University. 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, all personnel left the project, leaving it vacant.

The PFRC-1 experiment ran at PPPL from 2008 through 2011. [5]

The current experiment is PFRC-2.

Odd-parity rotating magnetic field

The electrical current that forms the field-reversed configuration (FRC) in the PFRC is driven by a rotating magnetic field (RMF). This method has been well-studied and produced favorable results in the Rotamak series of experiments. [6] However, rotating magnetic fields as applied in these and other experiments (so-called even parity RMFs) induce opening of the magnetic field lines. When a transverse magnetic field is applied to the axisymmetric equilibrium FRC magnetic field, rather than magnetic field lines closing on themselves and forming a closed region, they spiral around in the azimuthal direction and ultimately cross the separatrix surface which contains the closed FRC region. [3]

One rotating magnetic field pulse of the PFRC 2 device during an experiment, in slow motion PFRC-2 discharge.gif
One rotating magnetic field pulse of the PFRC 2 device during an experiment, in slow motion

The PFRC uses RMF antennae which produce a magnetic field which changes direction about a symmetry plane oriented with its normal along the axis, half-way along the length of the axis of the machine. This configuration is called an odd parity rotating magnetic field. Such magnetic fields, when added to axisymmetric equilibrium magnetic fields, do not cause opening of the magnetic field lines. [3] Thus the RMF is not expected to contribute to transport of particles and energy out of the core of the PFRC.

Low s-parameter

In an FRC, the name s-parameter is given to the ratio of the distance between the magnetic null and the separatrix, and the thermal ion Larmor radius. That is how many ion orbits can fit between the core of the FRC and where it meets the bulk plasma. [2] A high-s FRC would have very small ion gyroradii compared to the size of the machine. Thus, at high s-parameter, the model of magnetohydrodynamics (MHD) applies. [7] MHD predicts that the FRC is unstable to the "n=1 tilt mode," in which the reversed field tilts 180 degrees to align with the applied magnetic field, destroying the FRC.

Magnetohydrodynamics study of the interaction of electrically conducting fluids with magnetic fields

Magnetohydrodynamics is the study of the magnetic properties and behaviour of electrically conducting fluids. Examples of such magneto­fluids include plasmas, liquid metals, salt water, and electrolytes. The word "magneto­hydro­dynamics" is derived from magneto- meaning magnetic field, hydro- meaning water, and dynamics meaning movement. The field of MHD was initiated by Hannes Alfvén, for which he received the Nobel Prize in Physics in 1970.

A low-s FRC is predicted to be stable to the tilt mode. [7] An s-parameter less than or equal to 2 is sufficient for this effect. However, only two ion radii between the hot core and the cool bulk means that on average only two scattering periods (velocity changes of on average 90 degrees) are sufficient to remove a hot, fusion-relevant ion from the core of the plasma. Thus the choice is between high s-parameter ions that are classically well confined but convectively poorly confined, and low s-parameter ions that are classically poorly confined but convectively well confined.

The PFRC has an s-parameter between 1 and 2. [2] Stabilizing the tilt-mode is predicted to aid confinement more than the small number of tolerable collisions will hurt confinement.

Spacecraft propulsion

Scientists from Princeton Satellite Systems are working on a new concept called Direct Fusion Drive (DFD) that is based on the PFRC. It would produce electric power and propulsion from a single compact fusion reactor. The first concept study and modeling (Phase I) was published in 2017, [8] and was proposed to power the propulsion system of a Pluto orbiter and lander. [8] [9] Adding propellant to the cool plasma flow results in a variable thrust when channeled through a magnetic nozzle. Modeling suggests that the DFD might produce 5 Newtons of thrust per each megawatt of generated fusion power. [10] About 35% of the fusion power goes to thrust, 30% to electric power, 25% lost to heat, and 10% is recirculated for the RF heating. [8] The concept has advanced to Phase II [10] to further advance the design and shielding.

Related Research Articles

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The stability of a plasma is an important consideration in the study of plasma physics. When a system containing a plasma is at equilibrium, it is possible for certain parts of the plasma to be disturbed by small perturbative forces acting on it. The stability of the system determines if the perturbations will grow, oscillate, or be damped out.

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, 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.

In plasma physics, a lower hybrid oscillation is a longitudinal oscillation of ions and electrons in a magnetized plasma. The direction of propagation must be very nearly perpendicular to the stationary magnetic field, within about me/mi radians. Otherwise the electrons can move along the field lines fast enough to shield the oscillations in potential. The frequency of oscillation is

Madison Symmetric Torus

The Madison Symmetric Torus (MST) is a reversed field pinch (RFP) physics experiment with applications to both fusion energy research and astrophysical plasmas located at University of Wisconsin-Madison. RFPs are significantly different from tokamaks in that they tend to have a higher power density and better confinement characteristics for a given average magnetic field. RFPs also tend to be dominated by non-ideal phenomena and turbulent effects. MST is one of the sites in the Center for Magnetic Self Organization (CMSO).

The diffusion of plasma across a magnetic field was conjectured to follow the Bohm diffusion scaling as indicated from the early plasma experiments of very lossy machines. This predicted that the rate of diffusion was linear with temperature and inversely linear with the strength of the confining magnetic field.

A dense plasma focus (DPF) is a type of plasma generating system originally developed as a fusion power device starting in the early 1960s. The system demonstrated scaling laws that suggested it would not be useful in the commercial power role, and since the 1980s it has been used primarily as a fusion teaching system, and as a source of neutrons and X-rays.

The helicon double-layer thruster is a prototype spacecraft propulsion engine. It was created by Australian scientist Dr Christine Charles, based on a technology invented by Professor Rod Boswell, both of the Australian National University.

The polywell is a type of nuclear fusion reactor that uses an electric field to heat ions to fusion conditions. It is closely related to the fusor, the high beta fusion reactor, the magnetic mirror, and the biconic cusp. A set of electromagnets generates a magnetic field that traps electrons. This creates a negative voltage, which attracts positive ions. As the ions accelerate towards the negative center, their kinetic energy rises. Ions that collide at high enough energies can fuse.

Helically Symmetric Experiment

The Helically Symmetric Experiment (HSX), stylized as Helically Symmetric eXperiment, is an experimental plasma confinement device at the University of Wisconsin-Madison, with design principles that are hoped 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.

Magnetized target fusion (MTF) is a fusion power concept that combines features of magnetic confinement fusion (MCF) and inertial confinement fusion (ICF). Like the magnetic approach, the fusion fuel is confined at lower density by magnetic fields while it is heated into a plasma. As with the inertial approach, fusion is initiated by rapidly squeezing the target to greatly increase fuel density and temperature. Although the resulting density is far lower than in ICF, it is thought that the combination of longer confinement times and better heat retention will let MTF operate, yet be easier to build. The term magneto-inertial fusion (MIF) is similar, but encompasses a wider variety of arrangements. The two terms are often applied interchangeably to experiments.

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TAE Technologies is an American company based in Foothill Ranch, California, created for the development of aneutronic fusion power. The company's design relies on a field-reversed configuration (FRC), which combines features from other fusion concepts in a unique fashion.

Reversed-Field eXperiment

The Reversed-Field eXperiment (RFX) is the largest reversed field pinch device presently in operation, situated in Padua, Italy. It was constructed from 1985 to 1991, and is operated since 1992.

Direct Fusion Drive

Direct Fusion Drive (DFD) is a conceptual low radioactivity, nuclear-fusion engine designed to produce both thrust and electric power for interplanetary spacecraft. The concept is based on the Princeton field-reversed configuration reactor invented in 2002 by Samuel A. Cohen, and is being modeled and experimentally tested at Princeton Plasma Physics Laboratory, a US Department of Energy facility, and modeled and evaluated by Princeton Satellite Systems. As of 2018, the concept has moved on to Phase II to further advance the design.

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).

References

  1. Cohen, S. A.; Berlinger, B.; Brunkhorst, C.; Brooks, A.; Ferraro, N.; Lundberg, D. P.; Roach, A.; Glasser, A. H. (2007). "Formation of Collisionless High-β Plasmas by Odd-Parity Rotating Magnetic Fields". Physical Review Letters. 98 (14): 145002. Bibcode:2007PhRvL..98n5002C. doi:10.1103/physrevlett.98.145002. PMID   17501282.
  2. 1 2 3 4 Cohen, S. A. (June 4, 2008). "Field-reversed configuration: Community input to FESAC" (PDF). General Atomics Fusion Energy Research. General Atomics. Retrieved December 11, 2015.
  3. 1 2 3 Cohen, S. A.; Milroy, R. D. (2000-06-01). "Maintaining the closed magnetic-field-line topology of a field-reversed configuration with the addition of static transverse magnetic fields". Physics of Plasmas. 7 (6): 2539–2545. Bibcode:2000PhPl....7.2539C. doi:10.1063/1.874094. ISSN   1070-664X.
  4. Glasser, A. H.; Cohen, S. A. (2002-05-01). "Ion and electron acceleration in the field-reversed configuration with an odd-parity rotating magnetic field". Physics of Plasmas. 9 (5): 2093–2102. Bibcode:2002PhPl....9.2093G. doi:10.1063/1.1459456. ISSN   1070-664X.
  5. Jones, Ieuan R. (1999-05-01). "A review of rotating magnetic field current drive and the operation of the rotamak as a field-reversed configuration (Rotamak-FRC) and a spherical tokamak (Rotamak-ST)". Physics of Plasmas. 6 (5): 1950–1957. Bibcode:1999PhPl....6.1950J. doi:10.1063/1.873452. ISSN   1070-664X.
  6. 1 2 Barnes, Daniel C.; Schwarzmeier, James L.; Lewis, H. Ralph; Seyler, Charles E. (1986-08-01). "Kinetic tilting stability of field‐reversed configurations". Physics of Fluids. 29 (8): 2616–2629. Bibcode:1986PhFl...29.2616B. doi:10.1063/1.865503. ISSN   0031-9171.
  7. 1 2 3 Thomas, Stephanie (2017). "Fusion-Enabled Pluto Orbiter and Lander – Phase I Final Report" (PDF). NASA Technical Reports Server. Princeton Satellite Systems. Retrieved 2019-06-14.
  8. Hall, Loura (April 5, 2017). "Fusion-Enabled Pluto Orbiter and Lander". NASA. Retrieved July 14, 2018.
  9. 1 2 Thomas, Stephanie J.; Paluszek, Michael; Cohen, Samuel A.; Glasser, Alexander (2018). Nuclear and Future Flight Propulsion – Modeling the Thrust of the Direct Fusion Drive. 2018 Joint Propulsion Conference. Cincinnati, Ohio: American Institute of Aeronautics and Astronautics. doi:10.2514/6.2018-4769 . Retrieved 2019-06-14.