Numerical method for determining electrode shapes for high-perveance extractors
Abstract
The design of high-perveance extractors is dominated by the space-charge forces in the beam and by the aberrations caused by fringing fields at the apertures. Computer programs were developed for various extractor geometries that incorporate these effects. Basically the approach was to find a Laplace solution, external to the beam, that matches smoothly to the Child-Langmuir potential distribution in a laminar-flow ion beam. The electrode shapes calculated are not unique but do provide the desired beam optics. The application of this technique to the development of electrodes for a 250-mA, 75-keV hydrogen-ion extractor is discussed. For this application spherical geometry was used. The beam obtained was of high quality, that is, low emittance and small angular divergence.
- Publication:
-
Presented at the Linear Accelerator Conf
- Pub Date:
- 1981
- Bibcode:
- 1981liac.confS..19S
- Keywords:
-
- Design Analysis;
- Electrodes;
- Ion Beams;
- Ion Extraction;
- Mathematical Models;
- Shapes;
- Child-Langmuir Law;
- Computer Programs;
- Current Density;
- Differential Equations;
- Perveance;
- Electronics and Electrical Engineering