Formation of Collisionless High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>Plasmas by Odd-Parity Rotating Magnetic Fields

Cohen, Samuel A.; Berlinger, B.; Brunkhorst, C.; Brooks, A.; Ferraro, N.M.; Lundberg, D.P.; Roach, A.; Glasser, A. H.

doi:10.1103/physrevlett.98.145002

“…The amount of the shift is consistent with a reduced system inductance that results when the RM F o fields are excluded from the interior of the plasma column. 5 As the plasma evolves, its parameters, such as n e and Φ ex , change (Fig. 6a).…”

Section: Target Plasma and Hts-fc Parameters For The Pfrc-2 Devicementioning

confidence: 99%

“…The RM F coil array, which is usually external to the FRC's electrically non-conducting vacuum vessel, operates at a radio frequency (rf) near the ion-cyclotron range-of-frequencies. Because of several theoreticallypredicted unique benefits, 3,4 the RM F mode studied in the Princeton FRC (PFRC) device 5,6 has odd-parity symmetry (RM F o ). 7 For an FRC plasma to achieve equilibrium, a magneticflux-conserving external boundary must be enforced.…”

Section: Introductionmentioning

confidence: 99%

Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations

Oz¹,

Myers²,

Edwards³

et al. 2011

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The Princeton Field-Reversed Configuration (PFRC) experiment employs an odd-parity rotating magnetic field (RM F o ) current drive and plasma heating system to form and sustain high-β plasmas. For radial confinement, an array of coaxial, internal, passive, flux-conserving (FC) rings applies magnetic pressure to the plasma while still allowing radio-frequency RM F o from external coils to reach the plasma. The 3 ms pulse duration of the present experiment is limited by the skin time (τ f c ) of its room-temperature copper FC rings. To explore plasma phenomena with longer characteristic times, the pulse duration of the next-generation PFRC-2 device will exceed 100 ms, necessitating FC rings with τ f c > 300 ms. In this paper we review the physics of internal, discrete, passive FCs and describe the evolution of the PFRC's FC array. We then detail new experiments that have produced higher performance FC rings that contain embedded high-temperature superconducting (HTS) tapes. Several HTS tape winding configurations have been studied and a wide range of extended skin times, from 0.4 s to over 10 3 s, has been achieved. The new FC rings must carry up to 3 kA of current to balance the expected PFRC-2 plasma pressure, so the dependence of the HTS-FC critical current on the winding configuration and temperature was also studied. From these experiments, the key HTS-FC design considerations have been identified and HTS-FC rings with the desired performance characteristics have been produced.

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“…The RM F coil array, which is usually external to the FRC's electrically non-conducting vacuum vessel, operates at a radio frequency (rf) near the ion-cyclotron range-of-frequencies. Because of several theoreticallypredicted unique benefits, 3,4 the RM F mode studied in the Princeton FRC (PFRC) device 5,6 has odd-parity symmetry (RM F o ). For an FRC plasma to achieve equilibrium, a magneticflux-conserving external boundary must be enforced.…”

Section: Introductionmentioning

confidence: 99%

“…Thus the 3 ms value of the existing FC rings is already marginal. 5 In order to study longer-lived, better-confined plasmas in the larger-radius, higher-field PFRC-2 device now under construction, τ f c must be significantly extended. The experiments described herein lay the foundation for the nextgeneration, extended-skin-time PFRC FC.…”

mentioning

confidence: 99%

Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations

Myers

¹

,

Edwards

²

,

Berlinger

³

et al. 2012

Fusion Science and Technology

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The Princeton Field-Reversed Configuration (PFRC) experiment employs an odd-parity rotating magnetic field (RM F o ) current drive and plasma heating system to form and sustain high-β plasmas. For radial confinement, an array of coaxial, internal, passive, flux-conserving (FC) rings applies magnetic pressure to the plasma while still allowing radio-frequency RM F o from external coils to reach the plasma. The 3 ms pulse duration of the present experiment is limited by the skin time (τ f c ) of its room-temperature copper FC rings. To explore plasma phenomena with longer characteristic times, the pulse duration of the next-generation PFRC-2 device will exceed 100 ms, necessitating FC rings with τ f c > 300 ms. In this paper we review the physics of internal, discrete, passive FCs and describe the evolution of the PFRC's FC array. We then detail new experiments that have produced higher performance FC rings that contain embedded high-temperature superconducting (HTS) tapes. Several HTS tape winding configurations have been studied and a wide range of extended skin times, from 0.4 s to over 10 3 s, has been achieved. The new FC rings must carry up to 3 kA of current to balance the expected PFRC-2 plasma pressure, so the dependence of the HTS-FC critical current on the winding configuration and temperature was also studied. From these experiments, the key HTS-FC design considerations have been identified and HTS-FC rings with the desired performance characteristics have been produced.

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“…Historically, most FRCs have been allowed to resistively decay after formation. More recently, techniques have been proposed and/or utilized to sustain the plasma, including neutral beam injection ͑NBI͒ 8,9 and rotating magnetic fields ͑RMF͒ [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] in axially elongated prolate FRCs. For the more spherical oblate FRC, inductive sustainment [27][28][29] has been utilized with some success.…”

Section: Introductionmentioning

confidence: 99%

Inductive Sustainment of Oblate FRCs with the Assistance of Magnetic Diffusion, Shaping and Finite-Lamor Radius Stabilization

Gerhardt¹,

Белова²,

Ji³

et al. 2008

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Oblate field-reversed configurations ͑FRCs͒ have been sustained for Ͼ300 s, or Ͼ15 magnetic diffusion times, through the use of an inductive solenoid. These argon FRCs can have their poloidal flux sustained or increased, depending on the timing and strength of the induction. An inward pinch is observed during sustainment, leading to a peaking of the pressure profile and maintenance of the FRC equilibrium. The good stability observed in argon ͑and krypton͒ does not transfer to lighter gases, which develop terminal co-interchange instabilities. The stability in argon and krypton is attributed to a combination of external field shaping, magnetic diffusion, and finite-Larmor radius effects.

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Formation of Collisionless High-βPlasmas by Odd-Parity Rotating Magnetic Fields

Cited by 58 publications

References 19 publications

Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations

Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations

Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations

Inductive Sustainment of Oblate FRCs with the Assistance of Magnetic Diffusion, Shaping and Finite-Lamor Radius Stabilization

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