Constructing a field-emission (FE) x-ray tube

本课题旨在构建一个以多场阴极（MFC）为电子源的x射线相机。x射线照相机的建造和测试工作于1999年3月1日前完成。我们的x射线相机的整个系统基本上由相机室、电子源和泵送系统组成。各自的组件概述如下。1) x射线相机x射线相机完全由一个不锈钢圆柱形腔室组成，有七个观察和连接端口。在室内安装了一个人工智能靶和一个格拉泽透镜，后者是水冷的。2)电子源FE发射极或电子源在不破坏主真空的情况下可互换。它的位置调整是在机械手的帮助下完成的，从它发射的电子通过格雷泽透镜聚焦到目标上。3)泵送系统在两台涡轮分子泵的帮助下，摄像机室的泵送温度降至-10^<-7> Torr。所采用的磁场阴极是用剪刀简单切割的钼网。强调使用这种简单的网格发射器可以获得清晰的x射线图像。这确实是“划时代的”，因为迄今为止还没有使用场电子记录x射线图像。一个不希望的结果是，由于将腔室和高压绝缘体结合在一起的0环，腔室压力保持在10^<-7> Torr的数量级。由于场发射是一种典型的表面现象，因此需要超高真空来维持电子源的稳定运行。因此，我们的下一步是根据我们在目前项目中的各种经验构建一个特高压x射线相机。

This project aimed at constructing an x-ray camera equipped with a multiple field cathode (MFC) as the electron source. The construction of the x-ray camera and its test were completed before March 1, 1999.The total system of our x-ray camera is basically composed of camera chamber, electron source and pumping system. The respective components are outlined as follows.1) x-ray cameraThe x-ray camera is entirely composed of a stainless-steel cylindrical chamber with seven viewing and connection ports. Inside the chamber are installed an Al target and a Grazer lense, the latter of which is water-cooled.2) Electron sourceThe FE emitter, or the electron source, is exchangeable without breaking the main vacuum. Its position adjustment is done with the aid of a manipulator, and electrons emitted from it are focused onto the target through the Glazer lense.3) Pumping systemThe camera chamber is pumping down to -10^<-7> Torr, with the aid of two turbomolecular pumps. The field cathode employed were Mo meshes simply cut by a scissor. It is emphasized that sharp x-ray images were obtained using such a simple mesh emitter. This is really "epoch-making" because no x-ray image has been recorded so far by using field electrons. One undesirable result is that the chamber pressure remained at the order of 10^<-7> Torr because of an 0-ring to combine the chamber and the high-voltage insulator. Since field emission is a typical surface phenomenon, a ultrahigh vacuum (UHV) is demanded to maintain a stable operation of the electron source. Our next step is thus to construct a UHV x-ray camera based on a variety of experiences that we had in the present project.