Non-inductive Current Research Articles

Saturation induction and radiation in wave-driven plasmas

A study of some problems associated with noninductive current drive is presented. Both slow and fast waves, weak and strong power, and transient and steady-state responses are considered. The wave-induced deformation of the electron distribution function is expressed as a linear functional of the absorbed power. This expression is then used to study three important phenomena: saturation of the absorption, coupling with an inductive field, and wave-induced electron cyclotron emission.

Wave–plasma interaction near the second electron cyclotron harmonic

The linear wave propagation and spatial damping near the second electron cyclotron harmonic in a weakly relativistic Maxwellian plasma for an arbitrary angle of wave incidence are investigated. It is found that mode interaction with linear conversion of the extraordinary mode into a quasilongitudinal mode occurs over a relatively large range of plasma parameters. The absorption properties of the extraordinary and ordinary modes and their scaling laws are examined. The noninductive current drive by electron cyclotron waves is also discussed. The results obtained indicate quite favorable features of the wave–plasma interaction near the second electron cyclotron harmonic for plasma heating, current drive, and diagnostics applications.

High power heating and current drive in JT-60

Advances of JT-60 experiments in current drive and high power heating are presented. Fully noninductive current drive of 2 MA is achieved by LHRF without OH assistance. Thecurrent drive efficiency ηCD, defined as n-bare(1019 m-3)IRF(MA)Rp(m)/PLH(MW), is in the range0.8 - 1.7 and is improved to 1.7 - 3.0 when NB heating is applied to the LHCD plasma.Confinement improvement is also obtained when LHCD and NB heating are combined. TheMHD fluctuations in the central plasma region of such a discharge are suppressed by a factor of 10 compared to the case of NB heating only. In the electron heating mode of LHRF,Te(0) of 6±1 keV is obtained with a high heating efficiency of 2- 3 × 1019 keV/MWm3, andL-mode-like behavior is seen in the energy confinement in such plasmas. High iontemperatures of Ti(O) = 11 ± 2 keV are attained in hydrogen plasmas at densities ofn-bare = 2 - 3 × 1019 /m3 with NB heating. Substantial beam acceleration is observed when NB andICRF heating are combined. Charge exchange neutral spectra show that high energy ion tailof up to at least 160 keV is generated compared to the NB acceleration voltage of 60 kV.

A comparison of pulsed and steady-state tokamak reactor burn cycles. Part II: Magnet fatigue, power supplies, and cost analysis

Pulsed operation of a tokamak reactor imposes cost penalties due to such problems as mechanical fatigue and the need to periodically transfer large amounts of energy to various reactor components. This study focuses on lifetime limitations and capital costs of reactor subsystems in an attempt to quantify sensitivity to pulsed operation. Major problem areas include: fatigue in pulsed poloidal field coils; out-of-plane bending fatigue in toroidal field coils; electric power supply costs; and noninductive current driver costs. A capital cost comparison is made for tokamak reactors operating under the four distinct operating cycles which have been proposed. Since high availability and a low cost of energy will be mandatory for a commercial fusion reactor, we can characterize improvements in physics and technology which will help achieve these goals for different burn cycles. A key conclusion is that steady-state operation is likely to result in the least expensive tokamak reactor (perhaps 20% cheaper than the best pulsed reactor), provided noninductive current drive efficiency can be increased roughly four-fold over present-day experimental results.

A comparison of pulsed and steady-state tokamak reactor burn cycles. Part II: Magnet fatigue, power supplies, and cost analysis

Pulsed operation of a tokamak reactor imposes cost penalties due to such problems as mechanical fatigue and the need to periodically transfer large amounts of energy to various reactor components. This study focuses on lifetime limitations and capital costs of reactor subsystems in an attempt to quantify sensitivity to pulsed operation. Major problem areas include: fatigue in pulsed poloidal field coils; out-of-plane bending fatigue in toroidal field coils; electric power supply costs; and noninductive current driver costs. A capital cost comparison is made for tokamak reactors operating under the four distinct operating cycles which have been proposed. Since high availability and a low cost of energy will be mandatory for a commercial fusion reactor, we can characterize improvements in physics and technology which will help achieve these goals for different burn cycles. A key conclusion is that steady-state operation is likely to result in the least expensive tokamak reactor (perhaps 20% cheaper than the best pulsed reactor), provided noninductive current drive efficiency can be increased roughly four-fold over present-day experimental results.

Formation of a 100-kA Tokamak Discharge in the Princeton Large Torus by Lower Hybrid Waves

The development of noninductive current drive is of great importance in establishing the tokamak as a long-pulse or steady-state fusion reactor. Lower hybrid waves, carrying 200 kW of power at 800 MHz, have been launched into the Princeton Large Torus tokamak to initiate and drive the discharge current to a level in excess of 100 kA.