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We reported fabrication and field emission properties of carbon nanotube (CNT) field emitters which indicated the point-type CNT film emitter and line-type CNT film emitter. The CNT film field emitters were made by cutting CNT film using a razor. The CNT film emitters showed good emission properties such as the low turn-on field, the high emission current in a triode configuration. Especially, the...
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...
We fabricated the point-type CNT emitter for cold cathode x-ray source applications. The CNT point emitter was made by CNT film with a triangular tip shape, which was clamped using two stainless steel plates. Electrical properties of the point-type CNT emitter measured in triode structure showed the low turn-on and threshold electric fields, the high emission current and relatively high electron transmittance...
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...
Field emission properties of boron nitride (BN) nanomaterials have been studied for years to apply it at harsh ambient condition. However, the field emitters fabricated using the BN nanomaterials have limitations to utilize it as field emission devices due to their poor emission performances. Here, we report much enhanced field emission properties of the BN nanomaterial with low turn-on electric field,...
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 fabricated graphite nanoplatelet (GNP) field emitters using graphite adhesive and graphite rod. Comparing the field emission properties for different gap, turn-on electric field and threshold electric field were decreased almost in half, and maximum current density was increased about half as many again. The long-term emission stability also shows better results in large gap more than small gap...
Open source hardware (OSHW) has been created by the design movement and is a promising technology as it applies a compatible concept to a variety of components. Also, OSHW is intended to enable anyone to study specific hardware, makes modifications, and share hardware changes with peers. In this paper, we present the sensor interface application of OSHW. To develop embedded systems using the concept...
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...
We demonstrated high performance field emission of carbon nanotube (CNT) field emitters fabricated on a graphite rod. After the thermal annealing at 900 °C in vacuum ambient, the emitter showed a high emission current of 11.3 mA, corresponding to an emission current density of 5.8 A/cm2. The CNT emitter indicated a low turn-on field of 1.9 V/µm and stable emission stability at a current of 1 mA. In...
Boron nitride nanotubes (BNNTs) have been studied as a field emission material due to their unique and excellent properties such as high oxidation resistance and negative electron affinity. However, field emission properties of BNNT field emitters were rarely reported until now because it is difficult to synthesize high purity BNNTs and fabricate stable BNNT field emitters. Here, we report high field...
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.
A novel method for fabricating a small-sized carbon nanotube (CNT) emitter was developed. The emitter was fabricated by contacting the tungsten probe covered with CNT paste to the surface of Kovar rod, and then the brightness of electron beam generated from the CNT paste emitter was measured. We obtained the virtual source size of 1.13 × 10−10 m2 and the brightness of 1.2 × 107 A m−2sr−1 at an applied...
A tomographic methodology for inspection of TSV (Through Silicon Via) process wafers is developed by utilizing an X-ray source. In conventional X-ray computed tomography (CT), the scanning axis of X-ray source and detector is approximately parallel to the long axis of the phantom and perpendicular to the plane of X-ray source. However, because TSV projection data are captured by angling the phantom...
We have designed and fabricated a novel electrostatic lens module composed of a micro- and macro-focusing lens in carbon nanotube field-emission electron guns for energy-variable X-ray sources maintaining their focal spot size. The effective focal spot was observed to be small and isotropic by the micro-focusing lens to suppress the divergence of an individual electron beam and the elliptical macro-focusing...
Boron nitride (BN) nanomaterials have negative electron affinity, which makes BN a promising cold electron emission material. BN nanotube (BNNT) field emitters show excellent oxidation endurance after high temperature thermal annealing at 600 °C in air ambient. There is no damage to the BNNTs after the thermal annealing at a temperature of 600 °C and also no degradation of field emission properties...
We have developed a super-miniaturized X-ray tube with an outer diameter of 2 mm. Highly adhesive CNT field emitters were used as an electron source for super-miniaturized X-ray tube. We observed stable operation of the developed super-miniaturized X-ray tube, showing a clear X-ray image of an object.
We have fabricated a compact X-ray tube with carbon nanotube (CNT) field emitters. The compact X-ray tube exhibited stable and reliable digital operation with a high current. The good X-ray image was taken by using the X-ray tube at an anode voltage of 37 kV.
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