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A Fully-Sealed Carbon-Nanotube Cold-Cathode Terahertz Gyrotron

View Article: PubMed Central - PubMed

ABSTRACT

Gigahertz to terahertz radiation sources based on cold-cathode vacuum electron technology are pursued, because its unique characteristics of instant switch-on and power saving are important to military and space applications. Gigahertz gyrotron was reported using carbon nanotube (CNT) cold-cathode. It is reported here in first time that a fully-sealed CNT cold-cathode 0.22 THz-gyrotron is realized, typically with output power of 500 mW. To achieve this, we have studied mechanisms responsible for CNTs growth on curved shape metal surface, field emission from the sidewall of a CNT, and crystallized interface junction between CNT and substrate material. We have obtained uniform growth of CNTs on and direct growth from cone-cylinder stainless-steel electrode surface, and field emission from both tips and sidewalls of CNTs. It is essential for the success of a CNT terahertz gyrotron to have such high quality, high emitting performance CNTs. Also, we have developed a magnetic injection electron gun using CNT cold-cathode to exploit the advantages of such a conventional gun design, so that a large area emitting surface is utilized to deliver large current for electron beam. The results indicate that higher output power and higher radiation frequency terahertz gyrotron may be made using CNT cold-cathode electron gun.

No MeSH data available.


Related in: MedlinePlus

An image of the structure and morphology of the curved-shape CNT-SS cathode, where (a) top: before CNTs growth, and bottom: after CNTs growth, and (b) SEM image of CNTs morphology, and (c) TEM image of a typical CNT, the insert is the high resolution TEM image showing the graphite layer of CNT, and (d) Raman spectrum of CNTs grown on stainless steel. The D-band intensity is almost half of G-band feature, proving high structural quality of the sample.
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f3: An image of the structure and morphology of the curved-shape CNT-SS cathode, where (a) top: before CNTs growth, and bottom: after CNTs growth, and (b) SEM image of CNTs morphology, and (c) TEM image of a typical CNT, the insert is the high resolution TEM image showing the graphite layer of CNT, and (d) Raman spectrum of CNTs grown on stainless steel. The D-band intensity is almost half of G-band feature, proving high structural quality of the sample.

Mentions: The CNTs film covers uniformly the whole surface of cone-cylinder cathode electrode with large density, as shown in Fig. 3a. Typically, the height of cathode is 5.0 mm and the top and bottom diameter are 8.5 mm and 9.5 mm, respectively, and thus CNT-covered surface area is 1.41 cm2. The CNTs grow upward with a disorder shape (Fig. 3b), and their diameter typically ranges between 20–50 nm and the length is in between 2–6 μm, see Table 1. The TEM image (Fig. 3c) shows that a typical CNT has a smooth surface without amorphous carbon layer which demonstrates a good crystallization. The HRTEM image (Fig. 3c) shows the enlarged detail of the CNT walls that have about 36 graphite layers parallel to each other showing high quality with good graphitization, which means excellent electron transport ability and enables the high current carrying capacity. Typical Raman spectrum of the as-grown CNTs is shown in Fig. 3d. The ratio of ID/IG(ratio of G band over D band) results to be 0.61, about half of the G-band feature, suggesting that our carbon nanotubes are characterized by very few structural imperfections.


A Fully-Sealed Carbon-Nanotube Cold-Cathode Terahertz Gyrotron
An image of the structure and morphology of the curved-shape CNT-SS cathode, where (a) top: before CNTs growth, and bottom: after CNTs growth, and (b) SEM image of CNTs morphology, and (c) TEM image of a typical CNT, the insert is the high resolution TEM image showing the graphite layer of CNT, and (d) Raman spectrum of CNTs grown on stainless steel. The D-band intensity is almost half of G-band feature, proving high structural quality of the sample.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5017026&req=5

f3: An image of the structure and morphology of the curved-shape CNT-SS cathode, where (a) top: before CNTs growth, and bottom: after CNTs growth, and (b) SEM image of CNTs morphology, and (c) TEM image of a typical CNT, the insert is the high resolution TEM image showing the graphite layer of CNT, and (d) Raman spectrum of CNTs grown on stainless steel. The D-band intensity is almost half of G-band feature, proving high structural quality of the sample.
Mentions: The CNTs film covers uniformly the whole surface of cone-cylinder cathode electrode with large density, as shown in Fig. 3a. Typically, the height of cathode is 5.0 mm and the top and bottom diameter are 8.5 mm and 9.5 mm, respectively, and thus CNT-covered surface area is 1.41 cm2. The CNTs grow upward with a disorder shape (Fig. 3b), and their diameter typically ranges between 20–50 nm and the length is in between 2–6 μm, see Table 1. The TEM image (Fig. 3c) shows that a typical CNT has a smooth surface without amorphous carbon layer which demonstrates a good crystallization. The HRTEM image (Fig. 3c) shows the enlarged detail of the CNT walls that have about 36 graphite layers parallel to each other showing high quality with good graphitization, which means excellent electron transport ability and enables the high current carrying capacity. Typical Raman spectrum of the as-grown CNTs is shown in Fig. 3d. The ratio of ID/IG(ratio of G band over D band) results to be 0.61, about half of the G-band feature, suggesting that our carbon nanotubes are characterized by very few structural imperfections.

View Article: PubMed Central - PubMed

ABSTRACT

Gigahertz to terahertz radiation sources based on cold-cathode vacuum electron technology are pursued, because its unique characteristics of instant switch-on and power saving are important to military and space applications. Gigahertz gyrotron was reported using carbon nanotube (CNT) cold-cathode. It is reported here in first time that a fully-sealed CNT cold-cathode 0.22 THz-gyrotron is realized, typically with output power of 500 mW. To achieve this, we have studied mechanisms responsible for CNTs growth on curved shape metal surface, field emission from the sidewall of a CNT, and crystallized interface junction between CNT and substrate material. We have obtained uniform growth of CNTs on and direct growth from cone-cylinder stainless-steel electrode surface, and field emission from both tips and sidewalls of CNTs. It is essential for the success of a CNT terahertz gyrotron to have such high quality, high emitting performance CNTs. Also, we have developed a magnetic injection electron gun using CNT cold-cathode to exploit the advantages of such a conventional gun design, so that a large area emitting surface is utilized to deliver large current for electron beam. The results indicate that higher output power and higher radiation frequency terahertz gyrotron may be made using CNT cold-cathode electron gun.

No MeSH data available.


Related in: MedlinePlus