Development of a planar x-ray source with CNT field emitters

Summary form only given. Since the first cold cathode application of carbon nanotube (CNT) as an electron source, there were many attempts to make field emissive source because of its superior emission properties with digital-driving and large-area capability for advanced vacuum device applications. Especially, the utilization of these cathodes is an attractive alternative for the replacement of thermionic cathodes for generating X-rays. We have investigated the potential of screen printed CNT field emitters for improving the efficiency and reliability of large-area planar X-ray sources, and then we have fabricated and estimated about our flat-panel X-ray source (photo-bar) with glass body using vacuum sealing technique. The electron current density from the CNT emitters with gated triode structure was about 50 mA/cm² and was stable within 3% for continuous DC biasing time t >; 12 h. The electrons passing through hole in the gate electrode were accelerated to the desired energy, and were made to impinge on the metal target (such as Mo and W etc) for generating X-rays. The X-rays transmitted through Be-window were characterized using a dosimeter. At an acceleration voltage of V_a~15 kV and an emitted current of I_a~1.5 mA, the dose rates of X-rays were approximately 10mSv with low panel temperature (compared with thermionic X-ray source). Also an ionized current in air ambient can be achieved by approximately 900 nA at measured condition of 30cm distance between a planar X-ray source and ion current meter. Our developed planar X-ray source : photo-bar, design utilizing CNTs cold cathodes with vacuum sealing technique may be a significant advance in X-ray technology development and could lead to high-functional large-area X-ray sources for medical and industrial applications.