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Fusion Science and Technology
Latest News
In transition: Commercializing fusion power
Commercial fusion power is closer than ever. There are now around 30 U.S. fusion companies, several of which claim to be on track to connect to the grid as early as the 2030s.
Tokamak and laser inertial confinement approaches benefit from decades of research at facilities such as the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory and ITER, with alternative concepts including stellarator, magnetic mirror, and Z-pinch confinement also making notable progress as private and government funding for fusion increases.
Richard E. Siemon, W. Thomas Armstrong, Daniel C. Barnes, R. Richard Bartsch, Robert E. Chrien, James C. Cochrane, Waheed N. Hugrass, Ralph W. Kewish, Jr., Phillip L. Klingner, H. Ralph Lewis, Rulon K. Linford, Kenneth F. McKenna, Richard D. Milroy, Donald J. Rej, James L. Schwarzmeier, Charles E. Seyler, Eugene G. Sherwood, Ross L. Spencer, Michel Tuszewski
Fusion Science and Technology | Volume 9 | Number 1 | January 1986 | Pages 13-37
Technical Paper | doi.org/10.13182/FST86-A24698
Articles are hosted by Taylor and Francis Online.
The FRX-C device is a large field-reversed theta pinch experiment with linear dimensions twice those of its FRX-A and FRX-B predecessors. It is used to form field-reversed configurations (FRCs), which are high-beta, highly prolate compact toroids. The FRX-C has demonstrated an R2 scaling for particle confinement in FRCs, indicating particles are lost by diffusive processes. Particle losses were also observed to dominate the energy balance. When weak quadrupole fields were applied to stabilize the n = 2 rotational mode, FRC lifetimes >300 µs were observed. Detailed studies of the FRC equilibrium were performed using multichord and holographic interferometry. Measurements of electron temperature by Thomson scattering showed a flat profile and substantial losses through the electron channel. The loss rate of the internal poloidal flux of the FRC was observed to be anomalous and to scale less strongly with temperature than predicted from classical resistivity. Following a modification to the device, FRCs were translated from the theta-pinch coil into a direct current (dc) solenoid and metallic vacuum chamber. The translation process was observed to be in reasonable agreement with adiabatic theory. The FRCs were translated and trapped in a dc solenoid without active auxiliary coils. Trapping was aided by the inelastic reflection of FRCs off a magnetic mirror. Measurements of the radiated power from translating FRCs indicated that radiation is a small component in the power balance; thus it appears that electron thermal conduction is more important. The particle confinement of an FRC is expected to improve as s, which measures the number of local ion gyroradii between the field null and the separatrix, increases. A regime of increased susceptibility to magnetohydrodynamic modes, notably the internal tilt, however, has recently been predicted to have a threshold in s of 3 to 4. To address these issues, as well as the issues of electron energy loss and poloidal flux loss, a three-stage experiment has been proposed that is predicted to reach s of ~7. The FRX-D device will consist of separate formation, heating, and confinement regions. Plasma translation permits separation of these functions in a manner thought to be desirable for a fusion reactor.