Dynamic investigation of defects induced by short, high current pulses of high energy lithium ions
- PDF / 631,718 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 5 Downloads / 175 Views
Dynamic investigation of defects induced by short, high current pulses of high energy lithium ions Hua Guo1,2,3, Arun Persaud1, Steve Lidia1, Andrew M. Minor2,3, P. Hosemann2,4, Peter A. Seidl1, and Thomas Schenkel1 1
Accelerator and Fusion Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA 3 Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA 4 Nuclear Engineering Department, University of California, Berkeley, CA 94720, USA
ABSTRACT We employ intense and short pulses of energetic lithium (Li+) ions to investigate the relaxation dynamics of radiation induced defects in single crystal silicon samples. Ions both create damage and track damage evolution simultaneously at short time scales when we use the channeling effect as a diagnostic tool. Ion pulses, ~20 to 600 ns long and with peak currents of up to ~1 A are formed in an induction type linear accelerator, the Neutralized Drift Compression eXperiment at Lawrence Berkeley National Laboratory. By rotating silicon () membranes of different thicknesses and changing the incident ion energy, the fraction of channeled ions in the transmitted beam could be varied. In preliminary experiments we find that the Li ion intensity is not high enough to generate overlapping cascades (in time and space) that would be necessary to measure a change in the shape of the current waveform of the transmitted ion beam. We discuss the concept of pump-probe type experiments with short ion beam pulses to access defect dynamics in materials and outline a path to increasing damage rates with heavier ions and by the application of longitudinal and lateral pulse compression techniques.
INTRODUCTION Defect relaxation is a multi-scale event from picoseconds to years [1, 2], which has been attracting attention for scientific reasons and engineering applications for quite a long time. Up to now the fast time scales (on the order of picoseconds) could not be accessed directly [3, 4]. Current simulation tools assume certain time constants, but experimental data that verify these time constants are currently not available. Although conventional analytical tools, like transmission electron microscopy and atomic force microscopy, can easily reach atomic resolution in defect characterization, these techniques can only access long-lived defects in postmortem tests. In this regard, short-lived defects are invisible, since they self-anneal before a possible investigation using these techniques. Gaining access to short time scales will influence materials design and prediction of the material failure, especially under extreme conditions.
EXPERIMENT Intense, short pulses of energetic ions are highly desirable for studies of warm dense matter, high energy density physics experiments with volumetrically heated targets, and for studies of defect dynamics in solids [5]. To investigate radiation induced d
Data Loading...
