Measurement of particle transport coefficients on Alcator C-Mod
The goal of this thesis was to study the behavior of the plasma transport during the divertor detachment in order to explain the central electron density rise. The measurement of particle transport coefficients requires sophisticated diagnostic tools. A two color interferometer system was developed and installed on Alcator C-Mod to measure the electron density with high spatial ({approx} 2 cm) and high temporal ({le} 1.0 ms) resolution. The system consists of 10 CO{sub 2} (10.6 {mu}m) and 4 HeNe (.6328 {mu}m) chords that are used to measure the line integrated density to within 0.08 CO{sub 2} degrees or 2.3 {times} 10{sup 16}m{sup {minus}2} theoretically. Using the two color interferometer, a series of gas puffing experiments were conducted. The density was varied above and below the threshold density for detachment at a constant magnetic field and plasma current. Using a gas modulation technique, the particle diffusion, D, and the convective velocity, V, were determined. Profiles were inverted using a SVD inversion and the transport coefficients were extracted with a time regression analysis and a transport simulation analysis. Results from each analysis were in good agreement. Measured profiles of the coefficients increased with the radius and the values were consistent with measurements from other experiments. The values exceeded neoclassical predictions by a factor of 10. The profiles also exhibited an inverse dependence with plasma density. The scaling of both attached and detached plasmas agreed well with this inverse scaling. This result and the lack of change in the energy and impurity transport indicate that there was no change in the underlying transport processes after detachment.
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC02-78ET51013
- OSTI ID:
- 28385
- Report Number(s):
- DOE/ET/51013-307; PFC/RR-94-12; ON: DE95007763; TRN: 95:008381
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: Oct 1994
- Country of Publication:
- United States
- Language:
- English
Similar Records
Scaling and transport analysis of divertor conditions on the Alcator C-Mod tokamak
Observations of Alcator C-Mod plasmas from a five chord high energy resolution x-ray spectrometer array