Technology Commercialization and Partnerships | BSA 10-17: Diamond Amplified Photocathode for the Generation of High-Current High Brightness Electron Beams

Category: electronics & instrumentation

BSA 10-17: Diamond Amplified Photocathode for the Generation of High-Current High Brightness Electron Beams

BNL Reference Number: BSA 10-17

Patent Status: PCT filed on May 9, 2012

Summary

A vacuum encapsulated, hermetically sealed cathode capsule for generating a high-intensity electron beam and a method for making the same.

Description

This invention comprises a vacuum encapsulated, hermetically sealed cathode capsule for generating an electron beam of secondary electrons, which generally includes a cathode element having a primary emission surface adapted to emit primary electrons, an annular insulating spacer, a diamond window element comprising a diamond material and having a secondary emission surface adapted to emit secondary electrons in response to primary electrons impinging on the diamond window element, a first cold-weld ring disposed between the cathode element and the annular insulating spacer and a second cold-weld ring disposed between the annular insulating spacer and the diamond window element. The cathode capsule is formed by a vacuum cold-weld process such that the first cold-weld ring forms a hermetical seal between the cathode element and the annular insulating spacer and the second cold-weld ring forms a hermetical seal between the annular spacer and the diamond window element whereby a vacuum encapsulated chamber is formed within the capsule. This invention also involves a method for reducing contamination of a diamond amplified cathode capsule caused by out-gassing during use of the capsule. The method generally includes the steps of installing a hermetically sealed, vacuum encapsulated, diamond amplified cathode capsule within an electron gun chamber, heating the capsule to a temperature sufficient to clean a diamond element of the capsule, deforming the capsule during the heating step to break the hermetical seal of the capsule, whereby an interior of the capsule is brought into fluid communication with the electron gun chamber, and pumping the electron gun chamber to evacuate out-gases from both the chamber and the interior of the capsule.

Benefits

It would be desirable to provide an encapsulated secondary emission enhanced cathode device for use in an electron gun, which is easily and reliably manufactured. It would be further desirable to provide such a cathode device having an optimum non-contaminating structure, which permits simple and reliable manufacture and which will efficiently operate in superconducting RF electron guns for the generation of high-current high brightness electron beams. A diamond amplified photocathode can perform multiple functions: 1) It amplifies the primary current from a conventional photocathode with amplification factors exceeding 200, thereby reducing the demands on the primary cathode and the laser; and 2) It also acts as a window that isolates the cathode from the RF cavity, thereby shielding them from contaminating each other.

Applications and Industries

Electron guns are most commonly used to generate electron beams for vacuum tube applications such as cathode ray tubes (CRTs) found in televisions, game monitors, computer monitors and other types of displays. Electron guns provide the electron source for the generation of X-rays for both medical and scientific research applications, provide the electron beam for imaging in scanning electron microscopes, and are used for microwave generation. Photocathode-injectors are the electron source of choice for future linear colliders, high-power free electron lasers (FELs), linear accelerators with energy recovery, fourth generation light sources, injectors for laser-driven plasma wake field accelerators, or low-energy electron linacs for applied research. Highly efficient FELs have particularly desirable commercial characteristics, potentially applicable to activities from non-surgical liposuction and artery cleaning to significant military and security applications.