Structure of the ion wakefield potential surrounding objects immersed in a plasma
Abstract
Ion flow past a isolated, negatively charged structure such as a Langmuir probe tip or a dust particle immersed in a charge neutral plasma can result in ion focusing and creation of a positive space charge region downstream from the object. The structure and magnitude of the positive space charge region is a sensitive function of the bulk plasma parameters, the sheath that forms around the object, the sheath associated with the driven electrode and the charge on the object. We present measurements of the absolute magnitude and shape of the ion wakefield potential derived from extremely low-energy, head-on collisions between micron diameter dust particles levitated in a weak rf driven plasma. Over a range of particle spacing, there exists an attractive interaction between the two negatively charged dust particles due to the positive space charge region. The magnitude of the attractive and repulsive particle-particle interactions is found to be on the order of 10-14 N. A model for the particle-particle interaction potential that includes the attractive potential has been developed and is good agreement with experimental data. This work was performed at Sandia National Laboratories and supported by DoE Office of Science and the United States Department of Energy (DE-AC04-94AL85000).
- Publication:
-
APS Annual Gaseous Electronics Meeting Abstracts
- Pub Date:
- October 2002
- Bibcode:
- 2002APS..GECTR1001H