Hu, Qiuhong; Luxbright; Sweden
Hu, Q.-H.; Luxbright AB; Sweden
X-rays find applications in medical diagnostics, airport security inspection, and nondestructive testing in industry. However, the technology for generating X-rays has essentially been the same since the birth of the Coolidge tube for about 100 years ago, and the same physics for generating X-rays is still broadly in use today.
In the past two decades or so, the emergence of new classes of nano-materials has boosted advancement in fundamental research and applications of field emission cathodes in X-ray generation. Most of the X-ray tubes based on CNT cathode disclosed or published in literature seems to have too low emission current to replace the hot cathode tubes in applications. This can in principle be remedied by increasing the area of the cathode. However, larger cathode area will naturally lead to larger focal spot size and poorer spatial resolution of the image, an unwanted consequence. It is well known that the smaller the focal spot size, the higher the spatial resolution of the image. Likewise, for the hot cathode X-ray tubes, in order to decrease the focal spot size to the so called micro focus range, strong electromagnetic lenses are used to focus the electron beam traversing in the space between the cathode and the anode. Consequently, the region of the anode under the focal spot may be subjected to too high thermal load to maintain being solid.
In this paper, we report our work on the development of micro focus tubes by introducing a different microfocus solution combining with nanostructured ZnO cold cathode and/or hot cathode. These tubes are glass sealed and backward compatible. The key performance parameters are presented and evaluated, such as focal spot size, power output and anode power density. Comparison is made between these tubes and some of the microfocus tubes in the market.