Nondimensional transport scaling in DIII-D: Bohm versus gyro-Bohm resolved
- and others
The scaling of cross-field heat transport with relative gyroradius {rho}{sub *} was measured in low (L) and high (H) mode tokamak plasmas using the technique of dimensionally similar discharges. The relative gyroradius scalings of the electron and ion thermal diffusivities were determined separately using a two-fluid transport analysis. For L-mode plasmas, the electron diffusivity scaled as {chi}{sub e}, {proportional_to} {chi}{sub B}{rho}{sub *}{sup 1.1{+-}0.3} (gyro-Bohm-like) while the ion diffusivity scaled as {chi}{sub i} {proportional_to} {chi}{sub B}{rho}{sub *}{sup -0.5{+-}0.3} (worse than Bohm-like). The results were independent of the method of auxiliary heating (radiofrequency or neutral beam). Since the electron and ion fluids had different gyroradius scalings, the effective diffusivity and global confinement time scalings were found to vary from gyro-Bohm-like to Bohm-like depending upon whether the electron or ion channel dominated the heat flux. This last property can explain the previously disparate results with dimensionally similar discharges on different fusion experiments that have been published. Experiments in H-mode were also done with the expected values of beta, collisionality, safety factor, and plasma shape for thermonuclear ignition experiments. For these dimensionally similar discharges, both the electron and ion diffusivities scaled gyro-Bohm-like, {chi}{sub e},{chi}{sub i} {proportional_to} {chi}{sub B}{rho}{sub *}, as did the global thermal confinement time. This leads to a very favorable prediction for the confinement time of future ignition devices.
- Research Organization:
- General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-89ER51114; W-7405-ENG-48
- OSTI ID:
- 10122078
- Report Number(s):
- GA-A-21904; CONF-941101-8; ON: DE95007581; TRN: 95:002613
- Resource Relation:
- Conference: Meeting of the Division of Plasma Physics of the American Physical Society,Minneapolis, MN (United States),7-11 Nov 1994; Other Information: PBD: Feb 1995
- Country of Publication:
- United States
- Language:
- English
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