This work presents experiments about the transmission of electrons with an energy of around 15 keV with beam currents up to 20 µA through macroscopic glass capillaries. A systematic study was conducted to experimentally investigate the transmission of electrons through borosilicate glass capillaries with curve angles of 90°, 180°, 270° and 360° for the first time. The focus of the work was to identify the conditions under which the injected electron current is transmitted through the capillary. It was also shown that the transmission process in the macroscopic capillaries can be optically observed by cathodoluminescence—the interaction of electrons with the capillary surface causes locally a blue glow. Different distinctive “glow states” were observed and are found to correlate with different states of electron transmission.
A cubic Bézier-profile plate for multimodal vibration energy harvesting was developed. The design of the plate was based on an optimization procedure in which the profile of the plate was optimized via the parameters of a cubic Bézier curve to meet the requirements. The multimodal energy harvesting of the plate exploited its first bending mode and its first twisting mode. The conversion of vibration energy into electrical energy was by electromagnetic induction with a magnet attached to a corner of the plate. These two closely spaced vibration modes achieved the multi-modal energy harvesting of the device. Prototypes of the device were manufactured using a numerical-control machining process. The experimental results were in good agreement with the design specifications. With the same base lengths, height, and thickness, the maximum von Mises stress of the proposed plate was much lower due to its bell-shaped profile. The cubic Bézier curve chosen for the plate profile was effective for design of the closely-spaced multimodal vibration energy harvester. With the flexibility of its controllable parametric curve, a high design freedom of the energy harvester with specified frequency ratios could be achieved.
This work presents experiments about the transmission of electrons with an energy of around 15 keV with beam currents up to 20 µA through macroscopic glass capillaries. A systematic study was conducted to experimentally investigate the transmission of electrons through borosilicate glass capillaries with curve angles of 90°, 180°, 270° and 360° for the first time. The focus of the work was to identify the conditions under which the injected electron current is transmitted through the capillary. It was also shown that the transmission process in the macroscopic capillaries can be optically observed by cathodoluminescence – the interaction of electrons with the capillary surface causes locally a blue glow. Different distinctive “glow states” were observed and are found to correlate with different states of electron transmission.
In this work, we present observations about the transport of 15.2 keV electrons with a beam current of 21 μA through macroscopic dielectric capillaries. These capillaries are made of borosilicate glass with an inner diameter of about 6 mm, and samples with a bending angle of 90° and 360° were investigated. The electron gun was adjusted, and the beam injected into the capillary had a current of 21 μA and a divergence half angle of about 0.75°. A retarding field analyzer (RFA) was installed at the outlet of the capillary to collect the transported current and to investigate the particle energy of exiting electrons (Fig. 1). The transport of electrons to the outlet occurred nearly instantaneous in both capillaries, and the RFA at the outlet detected a current of around 20 μA for both capillary samples resulting in a transmission coefficient of over 95%. Energy measurements showed that the particle energy at the outlet is only at several electron volts, which reveals that electrons lost almost all of their incident energy while traveling through the capillary. A large amount of exiting particles are most likely secondary electrons emitted from the capillary sample. The fact that transmission coefficients for both samples are similarly high, and that the particles can still be transported through the 360° capillary although most of their energy is already lost at 90°, results in many questions that shall be investigated in further studies. The capillaries showed a blueish glow during electron transmission due to cathodoluminescence effects.
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