APPLICATIONS OF TECHNOLOGY:
- Semiconductor industry
- Extends lifetime of ion source backplate and chamber
- Does not alter extracted ion beam
Scientists at Berkeley Lab have invented a device that captures back streaming electrons in an RF-driven ion source, thereby significantly reducing the number of electrons that strike the dielectric backplate and cause it to crack or break. As a result, the invention prolongs the life of the ion source.
In the Berkeley Lab invention, the chamber backplate (a dielectric window) of an RF-driven ion source is fused to a tube with a durable, metal plug at its end. The back streaming electrons go through the tube and strike the plug rather than the dielectric window. The scientists tested the device on hydrogen gas with an RF power source operating at 13.6 MHz. As the power was increased to 1,800 W, the current density of the back-streaming electrons entering the dump increased in direct proportion to that of the extracted proton beam, which reached 125 mA/cm2. Thus, the dump appropriately captured electrons and did not adversely affect the extracted proton beam.
Ion sources often consist of chambers in which plasma is generated from a background gas by an external RF antenna coupled to the chamber backplate, i.e., a dielectric window. As the positive ions in the plasma are accelerated through an aperture in the front wall of the chamber to strike the desired target, secondary electrons produced in the accelerator column are accelerated backwards. These electrons strike, raise the temperature of, and eventually damage, the dielectric window. The Berkeley Lab invention solves this longstanding, damaging problem.
STATUS:Patent pending. Available for licensing or collaborative research.
DEVELOPMENT STATUS: Prototype tested.
Figure (a) Schematic of the RF ion source with a back-streaming electron dump. (b) A photograph of the ion source in operation.
FOR ADDITIONAL INFORMATION:
Ji Q., A. Sy, J.W. Kwan. “Radio frequency-driven proton source with a back-streaming electron dump,” Rev Sci Instrum. 81(2):02B312 (2010).
REFERENCE NUMBER: IB-2744