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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 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...
We describe reliable CNT x-ray tubes and their digital properties such as easy modulation of x-ray dose, high-speed operation, and low-voltage and low-power consumption control with an active-current control unit (ACCU) developed. The simple and advanced ACCU was found to shorten the response time of CNT x-ray tube down to sub-microsecond along with stable and reliable operation. The fast digital...
We have optimized the aging process of fully vacuum-sealed carbon nanotube (CNT) X-ray tubes in terms of an anode voltage, a cathode current and pulse on-time. Degradation and electrical arcing have been monitored and severely suppressed during the aging process. The completely aged CNT X-ray tube with an outer diameter of 15 mm and a length of 60 mm shows a cathode current of 3 mA at an anode voltage...
The advanced active-current control with a push-up voltage source is proposed for the fast operation of a carbon nanotube (CNT) field-emission X-ray tube while maintaining the advantages of improved stability and reliability. The push-up voltage source, composed of a resistor and a voltage supply, was found to reduce the response time of CNT X-ray tubes down to sub-microsecond.
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