THE PRODUCTION OF LARGE-DIAMETER LOW-VOLTAGE ELECTRON BEAMS IN THE ABSENCE OF A MAGNETIC FIELD,
Abstract
The production of long 10 mm diameter electron beams in the absence of a magnetic field was studied experimentally. The gun design is described at length. Pencil beams of several hundred eV energy were obtained in noble gases in the 1-20 microns pressure range. However, measurements disclosed that in these space-charge focused beams there may be a severe diminution of beam electron current with axial distance from the gun. Analyses showed that a large low-energy electron population exists in the beam volume, forming with the neutralizing positive ions a plasma in which two-stream instabilities can develop and produce the spread found in the energy of the primary beam electrons. Space potential measurements showed that a positive potential well existed in the beam volume, resulting in the trapping of the low-energy electrons. The unavoidable presence of this relatively large population of low-energy electrons in the beam volume prevented precise measurements of the high-energy beam electron current; reasonable measurements were obtained through special experimental precautions. The beams were studied over a range of the parameters of pressure and beam current, energy, and length. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1965
- Accession Number
- AD0627329
Entities
People
- M. J. Kofoid
- P. Zieske
Organizations
- Boeing