| 摘要 |
PURPOSE:To prevent the local heat generation at a focal point and to obtain an X-ray beam with strong and high intensity by forming the target surface of twin cathodes into a cylindrical shape and making the length (l) within a range of the specific relationship in relation to the inner diameter and an X-ray full reflection critical angle. CONSTITUTION:The target surface of twin cathodes is formed to satisfy the relation of phi/4thetac<=(l)<=4phi/thetac. For example, if (l)=2lc=2phi/thetac, where lc is the tube length to satis fy the critical angle, an increase of the strength of 1.5 times at the maximum is available on the center line of the tube and within the distance of lc from an X-ray outgoing window due to the full reflection phenome non of X-rays. Accordingly, if the twin cathodes are made of copper (thetac= 7.4X10<-3> radians) and phi=1mm., (l)=135mm., a load of up to 398kW (60kV, 6.6A) derived from multiplying by the area of the tube wall (848.2mm.<2>), which is practically referred as the focal point area for the tube cross section of 6.3mm.<2>, can be generated. Therefore, the effect is the same as obtaining a load of 600kW X-rays at the focal point of 6.3mm.<2>, and X-rays with 1.6 times of intensity and 10 times of strength can be obtained as compared with a case that X-rays of 60kW load are available at the focal point of 1X1mm.<2> under a normal condition with an X-ray extraction angle of 6 deg. using a rotary twin cathode method. |
