An experimental study of ion behavior in the Advanced Toroidal Facility

Wade, Mickey Ray.  Georgia Institute of Technology. ProQuest Dissertations Publishing, 1991. 9206116.

Abstract (summary)

Stellarators represent one of the most promising magnetic confinement concepts for a fusion reactor because of their intrinsic ability to operate at steady state, though legitimate concerns about various aspects of the stellarator concept must be addressed. One of these concerns is the seemingly unfavorable single-particle confinement properties inherent to the stellarator design. Although previous experimental studies of ion confinement in stellarators have indicated that the ions behave classically and are generally well confined, these studies were limited in scope. To complement these experiments and to provide additional information about ion behavior in stellarators, an experimental investigation of ion behavior has been performed on the Advanced Toroidal Facility (ATF). Measurements were made of both the thermal- and fast-ion distributions during electron cyclotron heating (ECH) and neutral beam injection (NBI). The purpose of this work was to study thermal- and fast-ion confinement in ATF with particular emphasis placed on constructing a consistent picture of ion confinement based on experimentally measured data. The primary ion diagnostic used in these studies was a two-dimensional scanning neutral particle analyzer (NPA).

Extensive studies of fast-ion behavior in various operating regimes on ATF were conducted. These studies were performed during NBI and encompass a wide range of plasma densities, ranging from extremely low density $(\bar{n}\sb{e}$ $\leq$ 7.5 $\times$ 10$\sp{12}$ cm$\sp{-3})$ to extremely high density $(\bar{n}\sb{e}$ $\geq$ 8.0 $\times$ 10$\sp{13}$ cm$\sp{-3})$. Fokker-Planck simulations of the measured data suggest that the injected ions behave classically and indicate that the injected beam power is not well absorbed at low and intermediate densities because of large charge-exchange and shine-through losses. Further simulations using the PROCTR transport analysis code indicate that this reduced absorption is probably the cause of the thermal collapse observed in intermediate-density NBI discharges.

Thermal ion confinement studies were generally confined to ECH-heated discharges with densities below $\bar{n}\sb{e}$ = 8.0 $\times$ 10$\sp{12}$ cm$\sp{-3}$. Typical ion temperatures inferred from NPA measurements were in the range of 100-200 eV. Although these temperatures are consistent with neoclassical heat transport predictions, there are large uncertainties at these temperatures and densities due to the unknown magnitude of the charge-exchange and convective losses.

Indexing (details)

Fluid dynamics;
Nuclear physics
0759: Fluid dynamics
0759: Gases
0552: Nuclear physics
Identifier / keyword
Applied sciences; Pure sciences; stellarators
An experimental study of ion behavior in the Advanced Toroidal Facility
Wade, Mickey Ray
Number of pages
Degree date
School code
DAI-B 52/09, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Thomas, C. E.
Georgia Institute of Technology
University location
United States -- Georgia
Source type
Dissertation or Thesis
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL