DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 263: Direct Measurement of E_rad Corrugation at Rational Surfaces | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Transport | Presentation time: | Not requested | Co-Author(s): | M. E. Austin |
| Description: | Use the combination of co and counter MSE views to directly measure the corrugation in the radial electric field at rational q surfaces that is responsible for transport barriers. The target plasmas are balanced-NBI L-modes with early heating so that q>2. The analysis will focus on MSE channels that view the radius where a rational surface, such as the q=2 surface, first enters the plasma. In the absence of E_rad effects, the co and counter viewing MSE channels will measure the same magnetic field pitch angle. Thus, a separation between the co/counter MSE signals at the time a rational q surface enters the plasma is a direct measurement of the E_rad corrugation effect. | ||
| Experimental Approach/Plan: | (1) Establish L-mode plasma with early beam heating to slow the evolution of the current profile. (2) Use 30LT and 210RT beams without modulation to collect continuous MSE and CER data. (3) May need to move the plasma location around to make sure the MSE channels are looking exactly at the location where the rational q surface (especially q=2) first enters the plasma. | ||
| Background: | Previous experiments by Max Austin found corregations in the electron temperature profile when a rational q surface entered the L-mode plasma. These corrugations were observed for both co-NBI and balanced-NBI (although only the co-NBI cases resulted in long lasting transport barriers). The GYRO turbulence simulation code predicted the existence of these corrugations by means of a equilibrium ExB shear flow driven by the zonal flows. This experimental proposal will look for direct evidence of this ExB shear flow by means of the E_rad sensitivity of the MSE diagnostic. | ||
| Resource Requirements: | NBI: 30LT and 210RT essential. | ||
| Diagnostic Requirements: | MSE is critical. | ||
| Analysis Requirements: | Need GYRO simulations. | ||
| Other Requirements: | -- | ||
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