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Although a focused electron beam is required in field emission-based various applications, the electron beam is generally diverged in a conventional triode because the gate has a circular aperture through which the electrons are accelerated to reach the anode. To prevent the beam divergence, a suspended multi-layer graphene (MLG) was fabricated on a very large gate aperture to be used as an electron-transparent...
We propose an advanced active current-control (ACC) unit composed of two cascade transistors for extremely stabilizing field emission currents. The upper transistor connected to the cathode modulates high voltages for field emission while the other one regulates emission current stably. Using the ACC unit developed, very stable emission currents were achieved from the fully vacuum-sealed x-ray tube...
We tried to improve field emission properties of carbon nanotube (CNT) paste emitters by controlling the size distribution of aggregated SiC fillers. The SiC fillers used as an adhesion promoter strongly affects the dispersion of CNT paste, determining uniformity and reproducibility of the field emitter. We found, to date, that the optimum distribution is about 1 μm of D50, the value of the particle...
Vertically aligned CNTs were synthesized on a four inch wafer, followed by the preparation of a CNT yarn. The yarn emitter was found to have an extremely high field enhancement factor, which was confirmed to have originated from multi-stage effect. In addition to superb field emission characteristics, the energy exchange during field emission, called Nottingham effect, was observed from the CNT yarn...
We developed a field emission nano-focus x-ray source using carbon nanotube (CNT) emitters and electron beam (E-beam) focusing modules, which could be used in the applications requiring the high-resolution x-ray images. For the nano-size focusing of E-beam from CNT emitters, we designed special focusing modules consisting of electrostatic and magnetic lenses. The geometries and operating conditions...
We developed a fully vacuum-sealed carbon nanotube (CNT)-based field emission x-ray tube with commercial-level performance for dental imaging application. The CNT x-ray tube was designed in a triode configuration with the focus-functional gate and had a compact size, much smaller than the conventional hot-cathode tubes. The small size of CNT x-ray tubes along with no cathode heating enables us to...
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