Ion controlling electrode assembly for a scanning electron beam computed tomography scanner
US5193105A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 18, 1991 |
| Grant date | Mar 9, 1993 |
| Priority date | — |
| Expiry date | Dec 18, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J35/04
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An electron beam scanning system employing a relatively short housing chamber wherein an electron beam is produced includes an ion controlling electrode assembly. Located in the housing between the electron gun and system beam optics, the assembly includes a generally cone-shaped rotating field ion controlling electrode (or "RICE") unit comprising cylindrically symmetrical element pairs disposed on opposite sides of the housing Z-axis. Preferably equal and opposite potential sources coupled to elements comprising an element pair create a transverse electric field therebetween. The vector sum of the fields produced by all element pairs is the transverse field created by the RICE unit. The potentials are varied, rotating the overall RICE field to controllably remove most but not all positive ions. The remaining ions improve the electron beam space-charge density, resulting in a sharply focused scanning electron beam. Preferably a disk-like positive ion electrode (or "PIE") unit coupled to a large positive potential is disposed downstream from the RICE unit to block upstream migration of positive ions. Where discontinuities are present in the housing, a periodic axial field ion contro…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.