Abstract:
Various embodiments are described herein for nanostructure field emission cathode structures and methods of making these structures. These structures generally comprise an electrode field emitter comprising a resistive layer having a first surface, a connection pad having a first surface disposed adjacent to the first surface of the resistive layer, and a nanostructure element for emitting electrons in use, the nanostructure element being disposed adjacent to a second surface of the connection pad that is opposite the first surface of the connection pad. Some embodiments also include a coaxial gate electrode that is disposed about the nanostructure element.
Abstract:
An exemplary electron emission device includes an electron emitter, an anode opposite to and spaced apart from the electron emitter, a first power supply circuit, and a second power supply circuit. The first power supply circuit is configured for electrically connecting the electron emitter and the anode with a power supply to generate an electric field between the electron emitter and the anode. The second power supply circuit is configured for electrically connecting the electron emitter with a power supply to supply a heating current for heating the electron emitter whereby electrons emit therefrom. Methods for generating an emission current with a relatively higher stability also are provided.
Abstract:
A method for preparing an iridium tip with atomic sharpness. The method includes tapering an iridium wire to a needle shape and heating the iridium needle in an oxygen atmosphere. Also disclosed is an iridium needle having a pyramidal structure which terminates with a small number of atoms prepared by the methods.
Abstract:
PROBLEM TO BE SOLVED: To provide a method for preparing an iridium tip with atomic sharpness. SOLUTION: The method includes steps of tapering an iridium wire to a needle shape and heating the iridium needle in an oxygen atmosphere. Also an iridium needle is provided which has a pyramidal structure which terminates with a small number of atoms. COPYRIGHT: (C)2009,JPO&INPIT
Abstract:
An x-ray source for use in Phase Contrast Imaging is disclosed. In particular, the x-ray source includes a cathode array of individually controlled field-emission electron guns. The field emission guns include very small diameter tips capable of producing a narrow beam of electrons. Beams emitted from the cathode array are accelerated through an acceleration cavity and are directed to a transmission type anode, impinging on the anode to create a small spot size, typically less than five micrometers. The individually controllable electron guns can be selectively activated in patterns, which can be advantageously used in Phase Contrast Imaging.
Abstract:
The present invention describes a field-emitter array cathode structure with two stacked control electrodes and their driving method to produce short electron pulses. A sequence of electric stimuli applied to the field emitter array drives generates an electron beam with precisely controlled emission angle, allowing for the production of short collimated electron pulses with high electron beam brightness.
Abstract:
Described here is a method for performing phase contrast imaging using an array of independently controllable x-ray sources. The array of x-ray sources can be controlled to produce a distinct spatial pattern of x-ray radiation and thus can be used to encode phase contrast signals without the need for a coded aperture. The lack of coded aperture increases the flexibility of the imaging method. For instance, because a fixed, coded aperture is not required, the angular resolution of the imaging technique can be increased as compared to coded-aperture imaging. Moreover, the lack of a radioopaque coded aperture increases the photon flux that reaches the subject, thereby increasing the attainable signal-to-noise ratio.
Abstract:
An x-ray source for use in Phase Contrast Imaging is disclosed. In particular, the x-ray source includes a cathode array of individually controlled field-emission electron guns. The field emission guns include very small diameter tips capable of producing a narrow beam of electrons. Beams emitted from the cathode array are accelerated through an acceleration cavity and are directed to a transmission type anode, impinging on the anode to create a small spot size, typically less than five micrometers. The individually controllable electron guns can be selectively activated in patterns, which can be advantageously used in Phase Contrast Imaging.