Asset Details
Do you wish to reserve the book?
Measurements of Reynolds Stress and its Contribution to the Momentum Balance in the HSX Stellarator
Hey, we have placed the reservation for you!
By the way, why not check out events that you can attend while you pick your title.
Oops! Something went wrong.
Looks like we were not able to place the reservation. Kindly try again later.
Are you sure you want to remove the book from the shelf?
Measurements of Reynolds Stress and its Contribution to the Momentum Balance in the HSX Stellarator
Do you wish to request the book?
Measurements of Reynolds Stress and its Contribution to the Momentum Balance in the HSX Stellarator
Please be aware that the book you have requested cannot be checked out. If you would like to checkout this book, you can reserve another copy
We have requested the book for you!
Your request is successful and it will be processed during the Library working hours. Please check the status of your request in My Requests.
Oops! Something went wrong.
Looks like we were not able to place your request. Kindly try again later.
Dissertation
Measurements of Reynolds Stress and its Contribution to the Momentum Balance in the HSX Stellarator
2014
Overview
In a magnetic configuration that has been sufficiently optimized for quasi-symmetry, the neoclassical transport and viscosity can be small enough that other terms can compete in the momentum balance to determine the plasma rotation and radial electric field. The Reynolds stress generated by plasma turbulence is identified as the most likely candidate for non-neoclassical flow drive in the HSX stellarator. Using multi-tipped Langmuir probes in the edge of HSX in the quasi-helically symmetric (QHS) configuration, the radial electric field and parallel flows are found to deviate from the values calculated by the neoclassical transport code PENTA using the ambipolarity constraint in the absence of externally injected momentum. The local Reynolds stress in the parallel and perpendicular directions on a surface is also measured using the fluctuating components of floating potential and ion saturation current measurements. Although plasma turbulence enters the momentum balance as the flux surface averaged radial gradient of the Reynolds stress, the locally measured quantity implies a significant contribution to the momentum balance. If extrapolated to a flux surface average, this locally measured Reynolds stress gradient is calculated to result in a flow drive many times larger than the observed flows. Probe measurements made at two locations on the device in regions with different magnetic geometry indicate very different, but consistently large Reynolds stress drive terms. The large variation of the local Reynolds stress on a flux surface suggests that a small number of measurement locations is insufficient to properly sample the flux surface averaged quantity. Contrary to expectations, measurements in configurations with the quasi-symmetry intentionally degraded deviate more from the neoclassically calculated velocity profiles than those in the QHS configuration. Measured density fluctuations and the Reynolds stress are reduced in these cases, indicating that additional terms may be important in the momentum balance.
