Conceptual design of the field-reversed mirror reactor

Abstract

We have completed a conceptual design study of the field-reversed mirror reactor. For this reactor a reference case conceptual design was developed in some detail. The parameters of the design result partly from somewhat arbitrary physics assumptions and partly from optimization procedures. Two of the assumptions-that only 10% of the alphaparticle energy is deposited in the plasma and that particle confinement scales with the ionion collison time-may prove to be overly conservative. A number of possible start-up scenarios for the field-reversed plasmas were considered, but the choice of a specific start-up method for the conceptual design was deferred, pending experimental demonstration of one or more of the schemes in a mirror machine. Basic to our plasma model is the assumption that, once created, the plas<na can be stably maintained by injection of a neutral-beam current sufficient to balance the particle-loss rate. The reference design is a multicell con figuration with 11 field-reversed toroidal plasma layers arranged along the horizontal axis ofu long-superconducting solenoid. Each plasma layer requires the injection of 3.6 MW of 200-keV deuterium and tritium, and produces 20 MW of fusion power. The reactor has a net electric output of 74 MWe. The preliminary estimate for the direct capital cost of the reference design is $ 1200/kWe. A balance-of-plant study is now underway and will result in a more accurate cost estimate.

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“…Comparing this to r p for a very elongated Hill's vortex (X > 1), we find an effective 5 = 0.18 R o . This effective thickness is roughly a factor of six smaller than previous heuristic values of 5 (5 «* R o ) [12]; this implies a life-time 6 times shorter than the heuristic answer. Another calculation which Eq.…”

“…The ion-energy confinement time may also be expressed in terms of the plasma size measured in ion gyro-radii and the ion-ion collision time: (22) where p 4 is the ion gyro-radius, based on the ion temperature at the 0-point and the magnetic field on axis at z = 0, and (T^) 0 is the ion-ion collision time at the 0-point. This result for the ion-energy confinement time is, like the previous result for the particle confinement time, substantially lower than heuristic estimates [12,13] In practical units, the energy confinement time for a plasma with one ion species, with mass /i X proton mass, and unit charge, is…”

“…It should be mentioned that our definition of the gyro-radius is slightly unconventional. A more common definition [12] bases p e on the mean energy and the vacuum magntic field. For a spherical vortex the vacuum field, B v , is given by…”

“…The Bessel function model estimates r p by equating it to the flux decay time T B of an infinite cylinder with resistivity r\ and a field null at radius R o . The time, r B , is calculated by solving the diffusion equation in cylindrical geometry: (12) with the boundary condition B Z (R O ) = 0. The result is…”

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“…The field-reversed-mirror reactor [1,2] has many attractive features, such as simple geometry (no centre column), high beta, and the possibility of relatively low power output compared to tokamaks. However, since there is no centre column, it is difficult to prevent the magnetic flux from decaying.…”