63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010;
Paris, France
Session LW3: Electron and Positron Collisions with Molecules
4:00 PM–6:00 PM,
Wednesday, October 6, 2010
Room: Petit Amphitheatre
Chair: Murtadha Khakoo, California State University, Fullerton
Abstract ID: BAPS.2010.GEC.LW3.1
Abstract: LW3.00001 : Gaseous positronics: collisions and transport of positrons in gases
4:00 PM–4:30 PM
Preview Abstract
Abstract
Author:
Zoran Petrovic
(Institute of Physics Belgrade)
While it may still be too early to call for a Gaseous Positronics
Conference, as a result of the increased activity in the field of
positron induced atomic and molecular physics, cross section sets
that are sufficiently complete to model low energy positron
transport in gases could be developed for a number of gases
including Ar, N2, H2 and CF4. Calculations of the transport
coefficients of low energy positrons ($<$10 eV) in gases have shown
some of the standard features similar to electrons, but also some
new kinetic phenomena that were not observed for electrons.
These include the negative differential conductivity (NDC) for
the bulk component of the drift velocity, while there is not even
a favourable situation for the NDC for the flux component. A
similar effect is observed as a large anisotropy of the bulk
diffusion. Most recently, in the studies of positron transport in
ExB fields, it was found that direction of drift may be quite
different, by as much as 70 degrees, between the flux and the
bulk components. In all cases it was found that the
non-conservative nature of positronium (Ps) formation leads to
all those processes.
The recently developed positron trap at ANU in Canberra,
Australia, has been used to cover the cross section data for a
large number of gases, and our main interest has been focused on
water vapour and other organic molecules
that would provide the physical basis for modeling positron
interaction with living organisms. Such data now exist, together
with the corresponding transport data that show all the features
induced by the Ps formation cross section. Finally, our improved
ability to model collisions of positrons in gases has made it
possible to model a gas-filled Surko trap and show how
distributions of positrons develop from the initial beam like
distributions and how positrons are thermalized.
In collaboration with S.J. Buckman, J.Sullivan, C.Makochekanwa,
A. Bankovic, S.Dujko, R. White, G. Malovic, M. Suvakov and S.
Marjanovic
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.GEC.LW3.1