WO2014172936A1

WO2014172936A1 - X-ray tube based on thermal emission of lab6 nanomaterial, and movable ct scanner

Info

Publication number: WO2014172936A1
Application number: PCT/CN2013/076029
Authority: WO
Inventors: 徐如祥; 林祖伦; 代秋声; 高枫; 张涛
Original assignee: 中国人民解放军北京军区总医院
Priority date: 2013-04-27
Filing date: 2013-05-22
Publication date: 2014-10-30
Also published as: CN103337442A; CN103337442B

Abstract

An X-ray tube based on thermal emission of a LaB6 nanomaterial, and a movable CT scanner. The X-ray tube based on thermal emission of a LaB6 nanomaterial comprises anode (10), a cathode (11), and a tube case (12). The tube case (12) is used for supporting the anode (10) and the cathode (11), and enables a working environment of the anode (10) and the cathode (11) to be insulated from the outside, thereby keeping the working environment to be vacuum. The cathode (11) is manufactured by using the LaB6 nanomaterial, and when the cathode (11) is heated to the working temperature of the LaB6 nanomaterial, electrons of thermal emission bombard the anode (10), so as to generate X-rays. According to the cathode manufactured by using the LaB6 nanomaterial, in a case in which the a same emission current density is obtained, the working temperature of the cathode manufactured by using the LaB6 nanomaterial is lower than that of a wolfram filament cathode by more than 1000 degrees centigrade, thereby greatly reducing the evaporation rate of the cathode material; in addition, the emission current, the stability and the service life of the used thermal emission cathode X-ray tube are greatly improved.

Description

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基于 LaB6纳米材料热发射的 X射线管及移动 CT扫描仪 X-ray tube and mobile CT scanner based on thermal emission of LaB6 nanomaterials

本发明要求 2013年 4月 27日向中国国家知识产^ ^提交的、申请号为 20130152452.7、名称为 "基于 LaB6纳米材料热发射的 X射线管及移动 CT扫描仪" 的中国专利申请的优先权。 The present invention claims the priority of a Chinese patent application filed on April 27, 2013, to the Chinese National Intellectual Property No. 20130152452.7, entitled "X-ray Tube and Mobile CT Scanner Based on Thermal Emission of LaB6 Nanomaterials".

技术领域 Technical field

本发明涉及医疗器械领域，特别涉及一种基于六硼化镧（La 米材料热发射的 X射线管及移动 CT扫描仪。 The invention relates to the field of medical instruments, in particular to an X-ray tube and a mobile CT scanner based on lanthanum hexaboride (La rice material thermal emission).

背景技术 Background technique

随着医疗科学技术的发展，涌现出了各种各样的医用病情探测仪 ( Computer tomography; CT )设备。其中 X射线管为一种常见的小型医用 CT设备。阴极是 X射线管的核心部件，直接决定着 X射线管的性能、成像的质量如分辨率和对比度，以及整机的工作效率。 With the development of medical science and technology, a variety of medical tomography (CT) devices have emerged. The X-ray tube is a common small medical CT device. The cathode is the core component of the X-ray tube, which directly determines the performance of the X-ray tube, the quality of the image such as resolution and contrast, and the efficiency of the whole machine.

现有技术中 X射线管通常是基于钨（W )丝热发射的 X射线管，即采用钨（W )丝制作 X射线管的阴极，其工作原理是钨 ( W )丝加热至其工作温度时热发射电子，热发射的电子轰击阳极，从而产生 X射线。 In the prior art, the X-ray tube is usually an X-ray tube based on tungsten (W) wire thermal emission, that is, a cathode made of tungsten (W) wire to make an X-ray tube, and the working principle is that the tungsten (W) wire is heated to its working temperature. When the heat emits electrons, the heat-emitting electrons bombard the anode, thereby generating X-rays.

现有技术基于钨（W )丝热发射的 X射线管中至少存在如下缺点：现有的 X射线管中的阴极采用的钨的电子逸出功高（(|)_W=4.52eV )，发射电流密度小，纯钨材料在 2200"€时，其热发射电流密度只有 0.3A/cm²。如果要想获得较大的总发射电流，通常采用提高阴极温度，但是提高阴极温度会使阴极材料的蒸发率增加，阴极材料蒸发会使钨丝变细，变细后的钨丝阴极又会使阴极温度升高，阴极蒸发加剧，从而形成恶性循环；此外，被蒸发的钨阴极材料会沉积在管壳上，形成连续或断续的钨导电薄膜，破坏了 X射线管的绝缘强度，使管压降低、管子报废，降低了 X射线管的寿命；同时，这种钨导电薄膜还阻挡了输出窗口的 X射线强度，降低了成像灵敏度。因此现有技术的基于钨（W )丝热发射的 X射线管的整体性能较差。 - - 发明内容 The prior art X-ray tube based on tungsten (W) wire thermal emission has at least the following disadvantages: The cathode in the existing X-ray tube uses tungsten with high electron emission work ((|) _W = 4.52 eV), emission The current density is small. The pure tungsten material has a thermal emission current density of only 0.3 A/cm ² at 2200". If a larger total emission current is to be obtained, the cathode temperature is usually increased, but the cathode temperature is increased. The evaporation rate increases, the evaporation of the cathode material causes the tungsten filament to become thinner, and the thinned tungsten cathode increases the cathode temperature and the cathode evaporation is intensified, thereby forming a vicious cycle; in addition, the evaporated tungsten cathode material is deposited on the On the shell, a continuous or intermittent tungsten conductive film is formed, which destroys the insulation strength of the X-ray tube, reduces the tube pressure, and the tube is scrapped, thereby reducing the life of the X-ray tube; at the same time, the tungsten conductive film blocks the output. The X-ray intensity of the window reduces the imaging sensitivity. Therefore, the overall performance of the prior art X-ray tube based on tungsten (W) wire thermal emission is poor. - - Invention content

在下文中给出关于本发明的简要概述，以便提供关于本发明的某些方面的基本理解。应当理解，这个概述并不是关于本发明的穷举性概述。它并不是意图确定本发明的关键或重要部分，也不是意图限定本发明的范围。其目的仅仅是以简化的形式给出某些概念，以此作为稍后论述的更详细描述的前序。 A brief summary of the invention is set forth below in order to provide a basic understanding of certain aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to identify key or critical aspects of the invention, and is not intended to limit the scope of the invention. Its purpose is to present some concepts in a simplified form as a pre-

本发明提供一种基于 LaB6纳米材料热发射的 X射线管及移动 CT 扫描仪，用以提高 X射线管的整体性能，可满足医学检测等应用需求。 The invention provides an X-ray tube and a mobile CT scanner based on thermal emission of LaB6 nanomaterials, which are used for improving the overall performance of the X-ray tube, and can meet the application requirements of medical testing and the like.

一方面，本发明了提供一种基于 LaB6纳米材料热发射的 X射线管，包括：阳极、阴极和管壳；所述管壳用于支撑所述阳极和所述阴极，并使得所述阳极和所述阴极的工作环境与外界绝缘，保持所述工作环境为真空；所述阴极采用 LaB6纳米材料制成，且所述阴极在加热到 LaB6纳米材料的工作温度时，热发射的电子轰击所述阳极以产生 X射线。 In one aspect, the present invention provides an X-ray tube based on thermal emission of a LaB6 nanomaterial, comprising: an anode, a cathode, and a tube; the tube case is for supporting the anode and the cathode, and the anode and the anode are The working environment of the cathode is insulated from the outside, keeping the working environment as a vacuum; the cathode is made of LaB6 nano material, and the cathode is heated to the working temperature of the LaB6 nano material, and the electrons are bombarded by heat. The anode is used to generate X-rays.

另一方面，本发明还提供了一种移动 CT扫描仪，包括如上所述的基于 LaB6纳米热发射的 X射线管。 In another aspect, the invention also provides a mobile CT scanner comprising an X-ray tube based on LaB6 nano-thermal emission as described above.

本发明提供的基于 LaB6纳米材料热发射的 X射线管，阴极采用 LaB6 纳米材料， LaB6纳米材料的逸出功只有金属钨（W ) 的一半左右，理论上，在同样的温度下， LaB6纳米材料的热发射电流密度比钨的热发射电流密度高几个数量级。因此，在获得同样发射电流密度的条件下， LaB6 纳米材料制成的阴极的工作温度要比钨丝阴极低 1000"€以上，这就大大减少了阴极材料的蒸发率。在相同发射电流密度下， LaB6纳米材料制成的阴极的蒸发率比钨丝阴极的蒸发率降低约 3个数量级，彻底解决了因钨丝阴极在高温工作下因材料蒸发导致 X射线管的损坏，使使用热发射阴极的 X射线管的发射电流、稳定性和寿命得到大幅度的提高。同时， LaB6 纳米材料制成的阴极大大减少了阴极材料的蒸发率，大大减少了在管壳上形成导电薄膜的概率，从而大大减少了导电薄膜阻挡输出窗口的 X射线强度，降低成像灵敏度的现象，有效地提高 X射线管的整体性能。 The invention provides an X-ray tube based on thermal emission of LaB6 nano material, the cathode adopts LaB6 nano material, and the work function of LaB6 nano material is only about half of that of metal tungsten (W). Theoretically, at the same temperature, LaB6 nano material The thermal emission current density is several orders of magnitude higher than the thermal emission current density of tungsten. Therefore, under the same emission current density, the cathode made of LaB6 nanomaterial has a working temperature of 1000" or more lower than that of the tungsten cathode, which greatly reduces the evaporation rate of the cathode material. Under the same emission current density The evaporation rate of the cathode made of LaB6 nanomaterial is about 3 orders of magnitude lower than that of the tungsten cathode, which completely solves the damage of the X-ray tube caused by the evaporation of the material of the tungsten cathode at high temperature, so that the thermal emission cathode is used. The emission current, stability and lifetime of the X-ray tube are greatly improved. At the same time, the cathode made of LaB6 nano material greatly reduces the evaporation rate of the cathode material, and greatly reduces the probability of forming a conductive film on the shell. The X-ray intensity of the conductive film blocking output window is greatly reduced, the imaging sensitivity is reduced, and the overall performance of the X-ray tube is effectively improved.

通过以下结合附图对本发明的最佳实施例的详细说明，本发明的这些以及其它的优点将更加明显。 These and other advantages of the present invention will become more apparent from the detailed description of the preferred embodiments of the invention.

附图说明本发明可以通过参考下文中结合附图所给出的描述而得到更好的理解，其中在所有附图中使用了相同或相似的附图标记来表示相同或者相似的部件。所述附图连同下面的详细说明一起包含在本说明书中并且形成本说明书的一部分，而且用来进一步举例说明本发明的优选实施例和解释本发明的原理和优点。在附图中： DRAWINGS The invention may be better understood by referring to the following description in conjunction with the drawings, wherein the same or similar reference numerals are used throughout the drawings. The drawings, which are included in the specification, and in the claims In the drawing:

图 1 为本发明实施例给出了几种阴极材料蒸发率 Figure 1 shows the evaporation rate of several cathode materials according to an embodiment of the present invention.

( (dM/dt)/(g · cm"² · s"¹) )与热发射电流密度 ( J/(A · cm"²) )的关系图。 ((dM/dt)/(g · cm" ² · s" ¹ )) is a graph showing the relationship between the thermal emission current density (J/(A · cm" ² )).

图 2为本发明实施例提供的基于 LaB6纳米材料热发射的 X射线管的结构示意图。 2 is a schematic structural view of an X-ray tube based on thermal emission of LaB6 nanomaterials according to an embodiment of the present invention.

图 3为本发明实施例涉及的 MB₆类型的六硼化物的结构示意图。图 4为本发明实施例提供的一种固定式阳极的基于 LaB6纳米材料热发射的 X射线管的电子光学原理示意图。图 5为本发明实施例提供的 X射线管阳极模型示例；图 6 为本发明实施例提供的阳极最大耐受电流随钨合金片厚度变化曲线示例；图 7为本发明另一实施例提供的三极结构 X射线管的结构示意图；图 8为本发明实施例提供的电子束入射角（或者靶面倾角）与光子产额的关系曲线示例；图 9为本发明实施例提供的 X射线管在如头部 CT扫描成像等医学检测的成像原理示意图；图 10为本发明实施例提供的靶面倾角 5度时，与靶面不同夹角的光子面密度的分布曲线示例；图 11为本发明实施例提供的不同靶面倾角下与电子束入射方向垂直的出射面内 X光子的数量的分布曲线示例；图 12为本发明实施例提供的靶面倾角与可用于成像的 X光子数的关系曲线示例。本领域技术人员应当理解，附图中的元件仅仅是为了简单和清楚起见而示出的，而且不一定是按比例绘制的。例如，附图中某些元件的尺寸可能相对于其他元件放大了，以便有助于提高对本发明实施例的理 - - 3 is a schematic structural view of an hexaboride of the MB ₆ type according to an embodiment of the present invention. FIG. 4 is a schematic diagram showing the electro-optical principle of an X-ray tube based on thermal emission of a LaB6 nanomaterial according to an embodiment of the present invention. 5 is an example of an anode model of an X-ray tube according to an embodiment of the present invention; FIG. 6 is an example of a curve of a maximum withstand current of an anode according to a thickness of a tungsten alloy sheet according to an embodiment of the present invention; FIG. 8 is a schematic diagram showing an relationship between an incident angle of an electron beam (or a target tilt angle) and a photon yield according to an embodiment of the present invention; FIG. 9 is an X-ray tube according to an embodiment of the present invention; FIG. 10 is a schematic diagram showing a distribution principle of a photon surface density at a different angle from a target surface when the target surface angle is 5 degrees according to an embodiment of the present invention; FIG. An example of a distribution curve of the number of X-photons in an exit plane perpendicular to the incident direction of the electron beam under different target tilt angles provided by the embodiment of the invention; FIG. 12 is a view of the target tilt angle and the number of X-photons usable for imaging according to an embodiment of the present invention; Example of a relationship curve. The elements in the figures are only shown for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements in order to help improve the scope of the embodiments of the invention. - -

具体实施方式 detailed description

为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。在本发明的一个附图或一种实施方式中描述的元素和特征可以与一个或更多个其它附图或实施方式中示出的元素和特征相结合。应当注意，为了清楚的目的，附图和说明中省略了与本发明无关的、本领域普通技术人员已知的部件和处理的表示和描述。基于本发明中的实施例，本领域普通技术人员在没有付出创造性劳动的前提下所获得的所有其他实施例，都属于本发明保护的范围。 The technical solutions in the embodiments of the present invention are clearly and completely described in conjunction with the drawings in the embodiments of the present invention. It is a partial embodiment of the invention, and not all of the embodiments. The elements and features described in one of the figures or one embodiment of the invention may be combined with elements and features illustrated in one or more other figures or embodiments. It should be noted that, for the sake of clarity, representations and descriptions of components and processes known to those of ordinary skill in the art that are not related to the present invention are omitted from the drawings and the description. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without departing from the inventive scope are the scope of the present invention.

X射线管是一种较为常见的小型医用 CT设备，主要通过热电子发射机制来实现，详细可以参考相关现有技术。对于热电子发射来说，总希望阴柘射电流密度越高越好，而工作温度越低越好，同时还要求阴极材料具有很好的化学稳定性、很低的蒸发率和耐高能离子的轰击能力，以保证 X射线管成像的稳定性和足够的寿命，这就对阴极材料和阴极电子枪结构提出了苛刻的要求。在现有传统的阴极材料中，能满足这样苛刻的阴极材料很少，根据 X射线管对阴极的要求，最常见的阴极材料是钨，所以，国内外的各种 X射线管全部使用热钨丝作为热阴极。但是钨的电子逸出功高（(|)_w=4.52eV )，发射电流密度小，纯钨材料在 2200"€时，其热发射电流密度只有 0.3A/cm²，如果要想获得较大的总发射电流，通常采用提高阴极温度，但是提高阴极温度会使阴极材料的蒸发率增加，阴极材料蒸发会使钨丝变细，变细后的钨丝阴极又会使阴极温度升高，阴极蒸发加剧，从而形成恶性循环；此外，被蒸发的钨阴极材料会沉积在管壳上，形成连续或断续导电薄膜，破坏了 X射线管的绝缘强度，使管压降降低、管子报废，降低了 X射线管的寿命；同时，这种钨导电薄膜还阻挡了输出窗口的 X射线强度，降低了成像灵敏度。 The X-ray tube is a relatively common small medical CT device, which is mainly realized by a thermal electron emission mechanism. For details, reference may be made to the related prior art. For thermionic emission, it is desirable that the higher the cathode current density, the better, and the lower the operating temperature, the better the cathode material has good chemical stability, low evaporation rate and high energy ion resistance. The bombardment ability to ensure the stability and sufficient life of the X-ray tube imaging imposes stringent requirements on the cathode material and cathode electron gun structure. Among the conventional cathode materials, there are few cathode materials that can meet such severe requirements. According to the requirements of the X-ray tube for the cathode, the most common cathode material is tungsten. Therefore, all kinds of X-ray tubes at home and abroad use hot tungsten. The wire acts as a hot cathode. However, the electron mobility of tungsten is high ((|) _w = 4.52eV), and the emission current density is small. When the pure tungsten material is 2200", its thermal emission current density is only 0.3A/cm ² , if you want to get a larger The total emission current is usually increased by the cathode temperature, but increasing the cathode temperature increases the evaporation rate of the cathode material. The evaporation of the cathode material causes the tungsten filament to become thinner, and the tapered tungsten cathode increases the cathode temperature. Evaporation is intensified, thereby forming a vicious circle; in addition, the evaporated tungsten cathode material is deposited on the envelope to form a continuous or intermittent conductive film, which destroys the insulation strength of the X-ray tube, reduces the tube pressure drop, and the tube is scrapped and lowered. The life of the X-ray tube; at the same time, this tungsten conductive film also blocks the X-ray intensity of the output window, reducing the imaging sensitivity.

基于上述原因，导致现有技术中采用材料钨制作而成的 X射线管的性能较差，因此，要解决阴极蒸发的问题，必须从阴极材料出发，选择同时具有低逸出功、耐高温和蒸发率低的材料。然而，这样的材料选择范围十分有限，表 1 为本发明实施例列出的各种阴极的主要发射特性。图 1 为本发明实施例给出了几种阴极材料蒸发率（（dM/dt)/(g · cm"² · s"¹) )与 - - 热发射电流密度（J/(A 'cm ²) )的关系图。如图 1所示，图 1示出了钼（Mu ) 作为阴极、纯钨（W ) 阴极、钍钨（Th-W ) 阴极和 LaB6 阴极的材料蒸发率与热发射电流密度的关系图。 For the above reasons, the performance of the X-ray tube made of tungsten material in the prior art is poor. Therefore, in order to solve the problem of cathode evaporation, it is necessary to select from the cathode material to have both low work function and high temperature resistance. A material with a low evaporation rate. However, such material selection ranges are very limited, and Table 1 shows the main emission characteristics of the various cathodes listed in the examples of the present invention. Figure 1 shows the evaporation rate of several cathode materials ((dM/dt) / (g · cm" ² · s" ¹ ) ) and - - Diagram of thermal emission current density (J / (A 'cm ² )). As shown in FIG. 1, FIG. 1 shows a relationship between material evaporation rate and thermal emission current density of molybdenum (Mu) as a cathode, a pure tungsten (W) cathode, a tantalum tungsten (Th-W) cathode, and a LaB6 cathode.

表 1 Table 1

由表 1和图 1所示，可见，在各种阴极材料中， LaB6的各项性能指标最适合于 X射线管中的工作^ K 因此，本发明从阴极材料入手，通过研制采用 LaB6制成的阴极，以实现大发射电流密度、长寿命、稳定可靠的阴极、优良的电子光学***，而且还能实现整管在短脉冲、高频工作条件下获得高分辨率图像输出，有效减少 X射线辐射剂量，满足现代医学诊断对医用 CT设备的要求，解决医用 CT的迫切需求，该 X射线管可以稳定、可靠、安全地用于舰载、车载、甚至机载的小型医用 CT设备，详细参见下述实施例的具体记载。 As shown in Table 1 and Figure 1, it can be seen that among various cathode materials, the performance indexes of LaB6 are most suitable for the work in the X-ray tube. Therefore, the present invention is started from the cathode material and is made by using LaB6. The cathode is used to achieve large emission current density, long life, stable and reliable cathode, excellent electro-optical system, and high-resolution image output under short pulse and high frequency operation conditions, effectively reducing X-rays. The radiation dose meets the requirements of modern medical diagnosis for medical CT equipment and solves the urgent need of medical CT. The X-ray tube can be used stably, reliably and safely for small medical CT equipment on board, on-board and even on-board. The specific description of the following examples.

图 2为本发明实施例提供的基于 LaB6纳米材料热发射的 X射线管的结构示意图。如图 2所示，本实施例的 X射线管包括阳极 10、阴极 11和管壳 12; 管壳 12用于支撑阳极 10和阴极 11，并使得阳极 10和阴极 11 - - 的工作环境与外界绝缘，保持管壳 12内的工作环境为真空；阴极 11采用 LaB6纳米材料制成，且阴极 11在加热到 LaB6纳米材料的工作温度时，热发射的电子轰击阳极 10以产生 X射线。 FIG. 2 is a schematic structural diagram of an X-ray tube based on thermal emission of a LaB6 nano material according to an embodiment of the present invention. As shown in FIG. 2, the X-ray tube of the present embodiment includes an anode 10, a cathode 11, and a bulb 12; the bulb 12 is for supporting the anode 10 and the cathode 11, and the anode 10 and the cathode 11 are provided. - The working environment is insulated from the outside, keeping the working environment inside the envelope 12 vacuum; the cathode 11 is made of LaB6 nanomaterial, and the cathode 11 is heated to the operating temperature of the LaB6 nanomaterial, and the electron-emitting anode 10 is thermally emitted. To generate X-rays.

本实施例的 X射线管具体在工作时，在管壳 12中的真空环境中，阴极 11在加热到阴极 11采用的 LaB6纳米材料的工作温度时，阴极 11热发射产生电子，产生的电子轰击阳极 10从而产生 X射线。 When the X-ray tube of this embodiment is in operation, in the vacuum environment in the envelope 12, when the cathode 11 is heated to the operating temperature of the LaB6 nanomaterial used in the cathode 11, the cathode 11 is thermally emitted to generate electrons, and the generated electron bombardment The anode 10 thus produces X-rays.

下面结合现有技术对比说明本发明实施例提供的基于 LaB6纳米材料热发射的 X射线管的优点： The advantages of the X-ray tube based on the thermal emission of LaB6 nanomaterials provided by the embodiments of the present invention are described below in conjunction with the prior art:

( 1 )现有技术中作为阴极的钨的电¾½射密度低，产生的电子束亮度低，为了得到较好的成像质量，整机在工作中必须增加扫描时间，降低了设备的使用效率，由于扫描时间增加，对高速扫描成像的物体十分不利，出现彗尾，降低了图像的分辨率，同时增加了辐射剂量，对被辐射体产生危害。而本实施例通过采用 LaB6纳米材料制作而成的阴极，具有较高的电流发射密度，产生的电子束亮度也较高，可以保证较高的成像质量。而且，与现有技术者相比，本发明实施例提供的基于 LaB6纳米材料热发射的 X射线管无须增加扫描时间，可以有效地提高设备的使用效率。 (1) In the prior art, tungsten as a cathode has a low electrical density of light, and the generated electron beam has low brightness. In order to obtain better image quality, the whole machine must increase the scanning time during operation, thereby reducing the use efficiency of the device. Due to the increase of scanning time, the object imaged by high-speed scanning is very disadvantageous, and the appendix appears, which reduces the resolution of the image and increases the radiation dose, which is harmful to the object to be irradiated. In the present embodiment, the cathode made of LaB6 nano material has a high current emission density, and the generated electron beam brightness is also high, which can ensure high image quality. Moreover, compared with the prior art, the X-ray tube based on the thermal emission of the LaB6 nano material provided by the embodiment of the invention does not need to increase the scanning time, and can effectively improve the use efficiency of the device.

( 2 )现有技术的钨丝阴极的温度很高（约 2200-3000 "C )，电子束发散度大，电子的初始发散角大，轰击阳极靶产生的 X射线斑品质不好，电子束的利用效率降低。而本发明实施例的 LaB6阴极相对于钨丝阴极工作温度较低，电子束发射度较小，电子的初始发散角较小，可以保证轰击阳极靶产生的 X射线光斑品质，电子束的利用效率也有效的得到提高。 (2) The temperature of the prior art tungsten wire cathode is very high (about 2200-3000 "C), the electron beam divergence is large, the initial divergence angle of the electron is large, and the quality of the X-ray spot generated by bombarding the anode target is not good, the electron beam The utilization efficiency of the LaB6 cathode of the embodiment of the invention is lower than that of the tungsten cathode, the electron beam emittance is small, and the initial divergence angle of the electron is small, which can ensure the quality of the X-ray spot generated by the bombardment of the anode target. The utilization efficiency of the electron beam is also effectively improved.

需要说明的是，碱土金属、稀土金属或钍与硼形成 MB₆类型的六硼化物都具有相同的立方晶体结构，体积较小的硼原子形成很强的共价键结合的硼框架，包围着较大的金属原子，图 3为 MB₆类型的六硼化物的结构示意图。如图 3所示，陷入硼晶格中的金属原子的配位数为 24，然而，金属原子和周围的硼原子之间没有价键联系，因此金属原子的价电子变成了自由电子，赋予这类化合物呈金属性。硼原子之间强大的键合力导致 MB₆ 化合物的熔点都在 2200 "C以上，而且化学性质稳定， 600 以下不与水、氧，甚至也不与酸碱发生化学反应。 It should be noted that the alkaline earth metal, the rare earth metal or the lanthanum and the boron form the MB ₆ type hexaboride have the same cubic crystal structure, and the smaller boron atom forms a strong covalently bonded boron framework, surrounded by Larger metal atoms, Figure 3 is a schematic view of the structure of the MB ₆ type hexaboride. As shown in Fig. 3, the coordination number of the metal atom trapped in the boron crystal lattice is 24, however, there is no valence bond between the metal atom and the surrounding boron atom, so the valence electron of the metal atom becomes a free electron, giving Such compounds are metallic. The strong bonding force between the boron atoms causes the melting point of the MB ₆ compound to be above 2200 "C, and is chemically stable. The chemical reaction below 600 does not react with water, oxygen, or even with acid or alkali.

在所有的六硼化物中， LaB6纳米材料具有最优良的理化性能和电子发射性能，大量的实验结果表明， LaB6纳米材料的逸出功为 2.4-2.8eV(纯钨阴极为 4.52 eV )，其导电能力与金属铅相近，蒸汽压极低，远低于钨、 - - 钼（Mu )等难熔金属材料的蒸汽压，硬度与金刚石相近。 LaB6纳米材料耐离子轰击的能力强，大量试验亦可证明， LaB6纳米材料阴极在高温下具有优异的抗高能离子和高能电子轰击的能力。 Among all the hexaborides, LaB6 nanomaterials have the best physical and chemical properties and electron emission properties. A large number of experimental results show that the LaB6 nanomaterials have a work function of 2.4-2.8 eV (4.52 eV for pure tungsten cathodes). The conductivity is similar to that of metal lead, and the vapor pressure is extremely low, much lower than tungsten. - - The vapor pressure of refractory metal materials such as molybdenum (Mu) is similar to that of diamond. LaB6 nanomaterials have strong resistance to ion bombardment. A large number of experiments can also prove that LaB6 nanomaterial cathodes have excellent resistance to high energy ions and high energy electron bombardment at high temperatures.

LaB6纳米材料的逸出功只有金属钨的一半左右，理论上，在同样的温度下， LaB6纳米材料的热发射电流密度比钨的热发射电流密度高几个数量级。由图 1给出的阴射电流密度与材料功函数的关系。因此，在获得同样发射电流密度的 ^下， LaB6纳米材料制成的阴极的工作温度要比钨丝阴极低 1000 以上，这就大大减少了阴极材料的蒸发率。由图 1 可见，在相同发射电流密度下， LaB6纳米材料制成的阴极的蒸发率比钨丝阴极的蒸发率降低约 3个数量级，彻底解决了因钨丝阴极在高温工作下因材料蒸发导致 X射线管的损坏，使使用热发射阴极的 X射线管的发射电流、稳定性和寿命得到大幅度的提高，从而有效地提高了 X射线管的性能。 The work function of LaB6 nanomaterials is only about half of that of tungsten. Theoretically, at the same temperature, the thermal emission current density of LaB6 nanomaterials is several orders of magnitude higher than that of tungsten. The relationship between the negative current density and the material work function given in Figure 1. Therefore, under the same emission current density, the cathode made of LaB6 nanomaterial has a working temperature lower than 1000 tungsten cathode, which greatly reduces the evaporation rate of the cathode material. It can be seen from Fig. 1 that at the same emission current density, the evaporation rate of the cathode made of LaB6 nanomaterial is about 3 orders of magnitude lower than that of the tungsten cathode, which completely solves the problem of evaporation of materials due to the tungsten cathode under high temperature operation. The damage of the X-ray tube greatly increases the emission current, stability and life of the X-ray tube using the thermal emission cathode, thereby effectively improving the performance of the X-ray tube.

( 3 )现有技术中的钨丝阴极采用单螺旋结构，阴极的发射面为非连续的曲面而非平面，从而使钨丝阴极的电子发射很不均匀，使得成像不均匀，分辨率下降。为了解决该问题，在上述实施例的基础上，本发明实施例的 X射线管中，采用 LaB6纳米材料制成的阴极的热发射面为连续平面。例如可以采用电火花切割、精密研磨和电化学抛光技术获得阴极所要求的表面光洁度。从而可以保证 LaB6纳米材料制成的阴极的电子发射均匀，使得成像均匀，从而提高分辨率，提高 X射线管的性能。可选地，本发明实施例中的阳极分为固定式阳极和旋转式阳极两种。其中固定式阳极方案设计 X射线管，可以有效降低 X射线源的重量和体积, 并降低 X射线管的制造和使用难度，但是其热容量有限，需要考虑如何有效散热，否则 X射线管将无法正常使用。 (3) The prior art tungsten wire cathode adopts a single spiral structure, and the emitting surface of the cathode is a non-continuous curved surface instead of a plane, so that the electron emission of the tungsten wire cathode is uneven, so that the imaging is uneven and the resolution is lowered. In order to solve this problem, in the X-ray tube of the embodiment of the present invention, the heat emitting surface of the cathode made of the LaB6 nano material is a continuous plane. For example, EDM, precision grinding, and electrochemical polishing techniques can be used to achieve the desired surface finish of the cathode. Thereby, the electron emission of the cathode made of LaB6 nano material can be ensured to be uniform, so that the imaging is uniform, thereby improving the resolution and improving the performance of the X-ray tube. Optionally, the anode in the embodiment of the invention is divided into a fixed anode and a rotary anode. The fixed anode design of the X-ray tube can effectively reduce the weight and volume of the X-ray source, and reduce the difficulty in manufacturing and using the X-ray tube. However, the heat capacity is limited, and it is necessary to consider how to effectively dissipate heat. Otherwise, the X-ray tube will not be able to function normally. use.

进一步地，与传统 X射线管不同，本发明实施例的 X射线管管可以采用栅控电子发射电子光学结构。即在阳极 10和阴极 11之间还设有栅极，在栅极和阳极 10之间外加电场以加速阴极 11热发射的电子，使之轰击阳极 10以产生 X射线。这种电子光学结构要求在满足发射电流的前提下，还需要能够方便的调制电流发射的大小和截止电流发射。图 4为本发明实施例提供的一种固定式阳极的 X射线管的电子光学原理示意图。如图 4 所示，当阳极电压 Va—定时，由阴相射的电子流的大小是通过栅极电压 Vg来调节的，当栅极电压相对于阴极电位为 "零" 时，发射电流达到最大值，调节栅极电压由 "零" 到 "负 "，阴招射的电子受到拒斥场的 - - 作用，发射到达阳极的电子流变小，当栅极电压的绝对值增大到一定值后，阴 «I射的电子便不能越过拒斥场形成的 "势垒"而返回阴极，此时阳极不能收集到电子流。因此在实际设计中，该固定式阳极的 X射线管既要满足阳极电流的要求，又要截止电压不能太高，还要使发射的电子能够按要求的电子束斑自动会聚到阳极上，需要综合考虑上述各方面，以设计符合需求的 X射线管。 Further, unlike the conventional X-ray tube, the X-ray tube of the embodiment of the present invention may employ a gate-controlled electron emission electron optical structure. That is, a gate is further provided between the anode 10 and the cathode 11, and an electric field is applied between the gate and the anode 10 to accelerate the electrons emitted by the cathode 11 to bombard the anode 10 to generate X-rays. Such an electro-optical structure requires that the size of the current emission and the off-current emission can be conveniently modulated while satisfying the emission current. 4 is a schematic diagram of an electro-optical principle of an X-ray tube of a fixed anode according to an embodiment of the present invention. As shown in FIG. 4, when the anode voltage Va-timing, the magnitude of the electron flow emitted by the cathode phase is adjusted by the gate voltage Vg, and the emitter current reaches the maximum when the gate voltage is "zero" with respect to the cathode potential. Value, adjust the gate voltage from "zero" to "negative", the electrons emitted by the yin are rejected by the field - - The effect is that the electron flow reaching the anode becomes smaller. When the absolute value of the gate voltage increases to a certain value, the electrons of the negative electrons cannot pass over the "barrier" formed by the rejection field and return to the cathode. The anode cannot collect the electron flow. Therefore, in the actual design, the X-ray tube of the fixed anode must meet the requirements of the anode current, and the cut-off voltage should not be too high, and the emitted electrons can be automatically concentrated on the anode according to the required electron beam spot. Consider all of the above aspects to design an X-ray tube that meets your needs.

为了对 X射线管阴极形成更好的保护，可选的，栅极可为采用金属网制成的金属网栅极。 In order to provide better protection for the X-ray tube cathode, the gate may alternatively be a metal mesh gate made of a metal mesh.

需要说明的是，本发明实施例中的阳极可以包括阳极体以及设于阳极体上的靶面。通过合理选择阳极材料，可有效提高其承受的最大束流强度，优选的，阳极体为铜阳极体，靶面为钨合金靶面。在 X射线管中，阴极发射的电子经电场加速后撞击到阳极靶上产生 X 射线，其中电子束 99%以上的能量转化成热量沉积在阳极内，只有不到 1%左右的能量转变成 X射线。如果电子在阳极靶上产生的大量热量得不到及时有效的散失，阳极靶表面的温升很快，在很短的时间内，阳极靶的表面材料就会融化，导致 X射线管损坏。因此，阳极靶的耐热和散热性能直接影响了 X射线管的使用。 It should be noted that the anode in the embodiment of the present invention may include an anode body and a target surface provided on the anode body. By reasonably selecting the anode material, the maximum beam intensity that it can withstand can be effectively improved. Preferably, the anode body is a copper anode body and the target surface is a tungsten alloy target surface. In an X-ray tube, electrons emitted from the cathode are accelerated by an electric field and then impinged on the anode target to generate X-rays, wherein more than 99% of the energy of the electron beam is converted into heat deposited in the anode, and less than about 1% of the energy is converted into X. Rays. If the large amount of heat generated by the electrons on the anode target is not lost in time, the temperature rise on the surface of the anode target is fast, and in a short period of time, the surface material of the anode target melts, causing damage to the X-ray tube. Therefore, the heat resistance and heat dissipation of the anode target directly affect the use of the X-ray tube.

X射线管的研制过程中一般涉及到以下几种材料：表 2: 材料特性参数 The following materials are generally involved in the development of X-ray tubes: Table 2: Material properties

从材料的性能可知，钨的熔点高，但是导热性能差；铜的导热性能好, 但是熔点低。石墨虽然熔点和比热都比钨、铜高，但是其原子序数低， X 射线的产生效率低。因此，可以采用铜做阳极体，以利用其良好的导热性能，采用钨合金片做靶面，以利用其高熔点性能。 - - 由于铜和钨的性能不一致，钨合金片的厚度是阳极设计的一个关键参数。如果钨合金片太厚，热量来不及传递，则钨合金片可能先熔化；如果钨合金片太薄，热量立刻传递给铜，则铜可能先熔化。无论哪种情况出现，都会影响到 X射线管的正常工作。因此，钨合金片的厚度需要选择最优值。为了计算钨合金片的最优厚度值，可使用热分析软件模拟不同厚度的钨合金片在不同强度的电子束脉冲轰击下，钨合金片与相邻金属铜的温度上升曲线，以及热量在阳极中的传递过程，研究材料厚度、电子束流强度与温度之间的关系。由于脉冲状态下电子束的热量生成比同强度下恒流状态下的低，为了给设计留有余量，我们主要模拟恒流状态下的参数。阳极的物理模型如下图 5所示：铜阳极体的几何尺寸为 040x50mm, 靶面材料为钨，钨合金片的直径为 010mm，焦点直径为 01mm，钨合金片的厚度范围为 20μιη~2ιηιη， X 射线管电压为 140kV，电流范围为 2mA~10mA。可使用 ANSYS12建立 X射线管阳极有限元模型，进行热分析计算，通过更改钨合金片的厚度及电流强度来计算分析阳极上的温度分布。电子束打在钨表面上，其焦点直径为 01mm , 电子进入钨的表层平均深度为 5μηι , 电子是在这段微小的体积内生热。施加热载荷的方法有两种：一种是简化了的施加载荷方法，将载荷施加在面上，即在钨的中心 01的表面上施加热载荷，根据电压和电流可以计算出施加在面上的热流量大小；另外一种方法是一局实际情况施加载荷，将热载荷施加到体上，即 01x0.005mm的圆柱上。传热率与面积成正比，由于 ^S^fTn^OJSSmm², S_vol =nr²+2nrh= .S 1 mm², 如果将载荷以面载荷的方施加，二者误差

From the properties of the material, tungsten has a high melting point but poor thermal conductivity; copper has good thermal conductivity but low melting point. Although graphite has higher melting point and specific heat than tungsten and copper, its atomic number is low and X-ray generation efficiency is low. Therefore, copper can be used as the anode body to take advantage of its good thermal conductivity, and a tungsten alloy sheet is used as a target surface to utilize its high melting point performance. - - Due to the inconsistent properties of copper and tungsten, the thickness of tungsten alloy sheets is a key parameter in anode design. If the tungsten alloy sheet is too thick and the heat is too late to pass, the tungsten alloy sheet may be melted first; if the tungsten alloy sheet is too thin and heat is immediately transferred to the copper, the copper may be melted first. In either case, it will affect the normal operation of the X-ray tube. Therefore, the thickness of the tungsten alloy sheet needs to be selected to an optimum value. In order to calculate the optimum thickness value of the tungsten alloy sheet, thermal analysis software can be used to simulate the temperature rise curve of the tungsten alloy sheet with different thicknesses under different electron beam pulse bombardment, tungsten alloy sheet and adjacent metal copper, and heat at the anode. In the transfer process, the relationship between material thickness, electron beam intensity and temperature is studied. Since the heat generation of the electron beam in the pulse state is lower than that in the constant current state under the same intensity, in order to leave a margin for the design, we mainly simulate the parameters in the constant current state. The physical model of the anode is shown in Figure 5: The copper anode body has a geometry of 040x50mm, the target surface material is tungsten, the tungsten alloy sheet has a diameter of 010mm, the focal diameter is 01mm, and the thickness of the tungsten alloy sheet ranges from 20μιη to 2ιηιη, X. The tube voltage is 140kV and the current range is 2mA~10mA. The ANSYS12 can be used to establish an X-ray tube anode finite element model for thermal analysis calculations. The temperature distribution on the anode can be calculated by changing the thickness and current intensity of the tungsten alloy sheet. The electron beam is struck on the tungsten surface with a focal diameter of 01 mm, and the electrons enter the surface of the tungsten with an average depth of 5 μm. The electrons generate heat within this tiny volume. There are two ways to apply a heating load: One is a simplified method of applying a load, applying a load on the surface, that is, applying a thermal load on the surface of the center 01 of tungsten, and calculating the applied surface according to the voltage and current. The amount of heat flow; another method is to apply a load in a practical situation, apply a thermal load to the body, that is, a cylinder of 01x0.005mm. The heat transfer rate is proportional to the area, since ^S^fTn^OJSSmm ² , S _vol =nr ² +2nrh= .S 1 mm ² , if the load is applied as the surface load, the error

^ = ^ " ^ = 0.019 , 可以忽略。为了建模求解方便，在此使用面载荷的施加方法，计算公式如下： ^ = ^ " ^ = 0.019 , can be ignored. For the convenience of modeling and solving, the application method of surface load is used here, and the calculation formula is as follows:

Q _ KA(T_hot - T_cold ) Q _ KA(T _hot - T _cold )

t d 上式中： Q——时间 ί内的传热量或者热流量。 Κ一一为热传导率。 Τ——温度。 t d In the above formula: Q – the amount of heat transfer or heat flow in time ί. One is the thermal conductivity. Τ - temperature.

A—— 触面积 - - d——两平面之间的巨离在 X射线管工作中，由于传导散热和辐射散热同时发生，故可计算它们对阳极温度上升的影响。在实际使用过程中，整个 X射线管都被放入油中绝缘、冷却。由于油的导热系数很小，因此在 X射线管工作的时候，热量主要存储在阳极上。扫描结束后，经过一段时间才能冷却下来。故在建模时，可以先忽略油的冷却效果。可通过热仿真来计算阳极上的温度分布，进而估算整个阳极的辐射散热。阳极温度分布中高温区域很小，主要集中在电子束焦点，绝大部分表面的温度低于 468。C。根据斯蒂芬-波尔兹曼定理： A—— touch area - - d - The large separation between the two planes In the X-ray tube operation, since conduction heat dissipation and radiation heat dissipation occur simultaneously, their influence on the anode temperature rise can be calculated. In actual use, the entire X-ray tube is placed in the oil to insulate and cool. Since the thermal conductivity of the oil is small, heat is mainly stored on the anode when the X-ray tube is operated. After the scan is over, it will take a while to cool down. Therefore, when modeling, you can ignore the cooling effect of the oil. The temperature distribution on the anode can be calculated by thermal simulation to estimate the radiation dissipation of the entire anode. The high temperature region of the anode temperature distribution is small, mainly concentrated in the electron beam focus, and most of the surface temperature is lower than 468. C. According to Stephen Boltzmann's theorem:

E = _£C(—)⁴ E = _£C (—) ⁴

100 为辐射力，单位为 W/m²; 100 is the radiation force, the unit is W/m ² ;

s为物体的辐射率； c为黑体辐射系数， 5.67W/(m².K⁴); s is the emissivity of the object; c is the blackbody emissivity, 5.67 W / (m ² .K ⁴ );

Γ为物体表面温度。按照电子束焦点温度 3300摄氏度，其他表面温度为 400。C进行估算，则阳极的辐射功率为： Γ is the surface temperature of the object. According to the electron beam focus temperature of 3300 degrees Celsius, the other surface temperature is 400. C estimates, then the radiant power of the anode is:

■P辐射 =^4钨£钨 "ΚΑ铜 Ε ■P radiation = ^ 4 tungsten £ tungsten "ΚΑ copper Ε

=(π*Γ*Γ)* ε钨 *c*(7V100)⁴+(2*7T*r₁*r₁+2*7r*r₁*/ * *c*(7V100)⁴ =(π*Γ*Γ)* εTungsten*c*(7V100) ⁴ +(2*7T*r ₁ *r ₁ +2*7r*r ₁ */ * *c*(7V100) ⁴

=92.17(W) 阳极的输入功率为 1050W , 那

辐射的功率占输入功率的比重艮小，可以忽略掉。下面是忽略辐射散热和绝缘油传导散热的仿真结果。根据设计要求，完成一次 CT扫描的最长时间为 30s，故在扫描时， X射线管必须可以持续工作 30s，此为依据，计算最优的钨合金片厚度以及可以耐受的最大恒流电流值。 - - 由图 6可见，在连续入射电子的情况下，当钨合金片厚度为 400~500μιη 的时候，最大耐受电流为 7.5mA。在图中曲线最高点的左边，铜将先熔化，右边，钨合金片将先熔化。对于脉冲工作模式，不同占空比下，同一厚度的钨合金片所能够耐受的最大脉冲电流随着占空比的减少而增加。考虑阳极靶的使用寿命，以及电子束的脉冲工作模式，本发明实施例将选用钨合金靶面的厚度为 400-500um，例如优选 0.5mm为钨合金片的优选厚度值。可选的，如图 7所示， X射线管的阳极 10包括阳极体 101和靶面 102。靶面 102 ^目对参考方向形成有预定的靶面倾角 α，参考方向与电子入射方向垂直，如图 7所示。靶面倾角 α是一个关键参数，它将直接影响到 X射线管的光产额、有效焦点尺寸、热量分布与传递等。为了研究靶面倾角的变化对 X光子的产额和角度分布的影响，可采用蒙特卡罗方法对其进行了模拟计算。例如使用 EGS软件模拟了 lxlO⁷个 140keV的电子轰击不同倾角的钨靶，统计了光产额和光子的空间分布。靶面倾角与光子产额的关系见图 8。从图 8中可以看出，靶面倾角越小， X光子产额越高。不过，靶面倾角是不是越小越好，这需要进行仔细的分析。在 CT扫描过程中最终利用的是以电子束入射方向近似垂直的扇形束之内 X光子，这部分 X光子才是真正为 CT成傳教出贡献的（如图 9所示），因此这个角度范围内的 X光子越多越好。下图为靶面倾角 5度时，与靶面不同夹角的光子面密度。从图 10中可以看出，随着与靶面夹角的增加，光子的面密度越来越小，即可用于成像的 X光子数越来越少。因此，虽然靶面倾角 5度时的总光子产额很高，但是与靶面夹角 85度处的光子面密度却很低。对不同靶面倾角下与电子束入射方向垂直的出射面内 X光子的数量进行统计，统计结果见图 11。从图 11中可以看出，随着靶面倾角的增加，出射面的光子数随之增加,但是在 45度左右达到最大值,然后便开始减小。在 CT成像中，影响断层图像分辨率的是 X射线管的有效焦点，而不是实际焦点。假设电子束平行入射，则实际焦点尺寸 L与投影后的有效焦点尺寸 d之间的关系如下： - - 从上式可以看出，如果实际焦点的尺寸 L很难减小时，可以通过减小靶面倾角 α来控制有效焦点的尺寸 d。如果入射的电子束单位横截面积的密度无法提高，根据下式可知，增大电子束流宽度 h减小靶面倾角 α有可能提高可成像 X光子的总数。 =92.17(W) The input power of the anode is 1050W, then

The radiated power accounts for a small proportion of the input power and can be ignored. The following is a simulation result that ignores the radiation heat dissipation and the conduction heat dissipation of the insulating oil. According to the design requirements, the maximum time for completing a CT scan is 30s, so the X-ray tube must be able to work continuously for 30s during scanning. Based on this, the optimal tungsten alloy sheet thickness and the maximum constant current that can be tolerated are calculated. value. - - As can be seen from Fig. 6, in the case of continuous incident electrons, the maximum withstand current is 7.5 mA when the thickness of the tungsten alloy sheet is 400 to 500 μm. On the left side of the highest point of the curve in the figure, the copper will melt first, and on the right, the tungsten alloy sheet will melt first. For the pulse mode of operation, the maximum pulse current that a tungsten alloy sheet of the same thickness can withstand at different duty cycles increases as the duty cycle decreases. Considering the service life of the anode target and the pulsed operation mode of the electron beam, the embodiment of the present invention will select a tungsten alloy target surface having a thickness of 400-500 um, for example, preferably 0.5 mm, as a preferred thickness value of the tungsten alloy sheet. Alternatively, as shown in FIG. 7, the anode 10 of the X-ray tube includes an anode body 101 and a target surface 102. The target surface 102 is formed with a predetermined target tilt angle α for the reference direction, and the reference direction is perpendicular to the electron incident direction, as shown in FIG. The target tilt angle α is a key parameter that directly affects the light yield, effective focus size, heat distribution and transfer of the X-ray tube. In order to study the influence of the change of the target tilt angle on the yield and angular distribution of X-ray photons, Monte Carlo method can be used to simulate the calculation. For example, EGS software was used to simulate lxlO ⁷ 140keV electrons bombarding tungsten targets with different dip angles, and the spatial distribution of light yield and photons was counted. The relationship between the target tilt angle and the photon yield is shown in Fig. 8. As can be seen from Figure 8, the smaller the target tilt angle, the higher the X-photon yield. However, the smaller the target angle, the better, which requires careful analysis. In the CT scanning process, the X-ray photons in the fan beam which are approximately perpendicular to the incident direction of the electron beam are used. This part of the X-ray photo is actually contributing to the CT mission (as shown in Fig. 9), so this angle range The more X-rays inside, the better. The figure below shows the photon areal density at an angle different from the target surface at a target angle of 5 degrees. As can be seen from Fig. 10, as the angle with the target surface increases, the areal density of photons becomes smaller and smaller, and the number of X-photons that can be used for imaging becomes less and less. Therefore, although the total photon yield at a target angle of 5 degrees is high, the photon surface density at an angle of 85 degrees from the target surface is low. The number of X-photons in the exit plane perpendicular to the incident direction of the electron beam at different target inclination angles is counted. The statistical results are shown in Fig. 11. As can be seen from Fig. 11, as the target tilt angle increases, the number of photons on the exit surface increases, but reaches a maximum at about 45 degrees and then begins to decrease. In CT imaging, the resolution of the tomographic image is the effective focus of the X-ray tube, not the actual focus. Assuming that the electron beams are incident in parallel, the relationship between the actual focus size L and the projected effective focus size d is as follows: - - As can be seen from the above equation, if the size L of the actual focus is difficult to reduce, the size d of the effective focus can be controlled by reducing the target tilt angle α. If the density of the cross-sectional area of the incident electron beam unit cannot be increased, it is known from the following equation that increasing the electron beam width h by decreasing the target tilt angle α may increase the total number of imageable X-photons.

£|— & 保持有效焦点尺寸和电子束单位横截面积的密度不变，靶面倾角与可用于成像的 X光子数之间的关系曲线见图 12。从图 12中可以看出，靶面倾角越小，通过增加电子束流宽度可以有效增加可用于成像的 X光子数量。不过结合前图可知，此时，入射的电子束流的总量显著增加，进而增加了阳极所接受的热量，这将给 X射线管的散热提出了挑战。因此，阳极的靶面倾角的确定需要在可用于成像的 X光子数量与入射电子的热量之间寻求一种平衡。经过综合考虑，靶面倾角优选为 11度。 £|— & Keep the effective focus size and the density of the cross-sectional area of the electron beam constant. The relationship between the target tilt angle and the number of X-photons available for imaging is shown in Figure 12. As can be seen from Fig. 12, the smaller the target tilt angle, the more the number of X-photons available for imaging can be effectively increased by increasing the beam width. However, as can be seen from the previous figure, at this time, the total amount of incident electron beam current is significantly increased, which in turn increases the heat received by the anode, which poses a challenge to the heat dissipation of the X-ray tube. Therefore, the determination of the target face tilt angle of the anode requires a balance between the amount of X-photons available for imaging and the heat of incident electrons. After comprehensive consideration, the target tilt angle is preferably 11 degrees.

进一步优选地，上述实施例中的 X射线管总长度小于或等于 120mm，以充分保证 X射线管的小巧型，可以便于携带，方便适用于舰载、车载、战地医院等特殊环境。 Further preferably, the total length of the X-ray tube in the above embodiment is less than or equal to 120 mm, so as to fully ensure the compact shape of the X-ray tube, which can be easily carried, and is convenient for use in special environments such as shipboard, vehicle, and battlefield hospitals.

进一步优选地，上述实施例中的最大直径小于或等于 60mm。进一步优选地，上述实施例中的阳极和阴极的距离小于或等于 10um。这样可以保证 X射线管的优良性能。 Further preferably, the maximum diameter in the above embodiment is less than or equal to 60 mm. Further preferably, the distance between the anode and the cathode in the above embodiment is less than or equal to 10 um. This will ensure the excellent performance of the X-ray tube.

进一步优选地，上述实施例中的 X射线管的同心度小于 1，即可以认为 X射线管的阳极和阴极的中心都非常靠近整个 X射线管的轴，从而可以有效地保证 X射线管的优良性能。 Further preferably, the concentricity of the X-ray tube in the above embodiment is less than 1, that is, the anode and the cathode of the X-ray tube can be considered to be very close to the axis of the entire X-ray tube, thereby effectively ensuring the excellent X-ray tube. performance.

经试验验证，本发明实施例的基于 LaB6 纳米热发射的 X射线管饱和发射电流（脉冲） > 10mA; 且 X射线管焦点投影光斑尺寸≤1.2x1.2mm²; 而且 X射线管能够承受 7倍重力加速度考验，因此，本实施例的 LaB6纳米材料制成的阴极的 X射线管与现有的钨丝阴极的 X射线管相比，不仅能能够提高成像灵敏度，成像分辨率，具有较好的性能；还能有效地延长 X 射线管的寿命，节约成本。此外，本发明还提供了一种移动 CT扫描仪，该移动 CT扫描仪包括上述任一实施例提供的基于 LaB6纳米热发射的 X射线管，通过该 X射线管产生 X射线以对脑部等人体部位进行医学检测。 It has been experimentally verified that the saturation emission current (pulse) of the X-ray tube based on LaB6 nano-thermal emission of the embodiment of the present invention is >10 mA; and the spot projection spot size of the X-ray tube is ≤1.2×1.2 mm ² ; and the X-ray tube can withstand 7 times The gravity acceleration test, therefore, the X-ray tube of the cathode made of the LaB6 nano material of the embodiment can not only improve the imaging sensitivity and the imaging resolution, but also has better imaging performance than the existing X-ray tube of the tungsten cathode. Performance; can also effectively extend the life of the X-ray tube, saving costs. In addition, the present invention also provides a mobile CT scanner comprising the X-ray tube based on LaB6 nano-heat emission provided by any of the above embodiments, by which X-rays are generated to the brain, etc. Medical examination of the human body parts.

在本发明上述各实施例中，实施例的序号仅仅便于描述，不代表实施 - - 例的优劣。对各个实施例的描述都各有侧重，某个实施例中没有详述的部分，可以参见其他实施例的相关描述。 In the above embodiments of the present invention, the serial numbers of the embodiments are merely for convenience of description, and do not represent implementation. - - The pros and cons of the example. The descriptions of the various embodiments are all focused on, and the parts that are not detailed in an embodiment can be referred to the related description of other embodiments.

本领域普通技术人员可以理解：实现上述方法实施例的全部或部分步骤可以通过程序指令相关的硬件来完成，前述的程序可以存储于一计算机可读取存储介质中，该程序在执行时，执行包括上述方法实施例的步骤；而前述的存储介质包括：只读存储器（Read-Only Memory, 简称 ROM )、随才1 ^储器（Random Access Memory, 筒称 RAM )、磁碟或者光盘等各种可以存储程序代码的介质。 A person skilled in the art can understand that all or part of the steps of implementing the above method embodiments may be completed by using hardware related to the program instructions. The foregoing program may be stored in a computer readable storage medium, and the program is executed when executed. The foregoing storage medium includes: a read-only memory (ROM), a random access memory (Random Access Memory), a magnetic disk, or an optical disk. A medium that can store program code.

在本发明的装置和方法等实施例中，显然，各部件或各步骤是可以分解、组合和 /或分解后重新组合的。这些分解和 /或重新组合应视为本发明的等效方案。同时，在上面对本发明具体实施例的描述中，针对一种实施方式描述和 /或示出的特征可以以相同或类似的方式在一个或更多个其它实施方式中使用，与其它实施方式中的特征相组合，或替代其它实施方式中的特征。 In the embodiments of the apparatus and method of the present invention, it is apparent that the various components or steps may be recombined after being decomposed, combined, and/or disassembled. These decompositions and/or recombinations should be considered as equivalents to the invention. Also, in the above description of the specific embodiments of the present invention, features described and/or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, and in other embodiments. The features are combined or substituted for features in other embodiments.

应该强调，术语 "包括 /包含" 在本文使用时指特征、要素、步骤或组件的存在，但并不排除一个或更多个其它特征、要素、步骤或组件的存在或附加。 It is to be understood that the term "comprises" or "comprises" or "comprises" or "comprising" or "comprising" or "comprising" or "comprising" or "comprising"

最后应说明的是：虽然以上已经详细说明了本发明及其优点，但是应当理解在不超出由所附的权利要求所限定的本发明的精神和范围的情况下可以进行各种改变、替代和变换。而且，本发明的范围不仅限于说明书所描述的过程、设备、手段、方法和步骤的具体实施例。本领域内的普通技术人员从本发明的公开内容将容易理解，根据本发明可以使用执行与在此所述的相应实施例基本相同的功能或者获得与其基本相同的结果的、现有和将来要被开发的过程、设备、手段、方法或者步骤。因此，所附的权利要求旨在在它们的范围内包括这样的过程、设备、手段、方法或者步骤。 It is to be understood that the present invention and its advantages are described in detail, and it is understood that various changes, substitutions and modifications can be made without departing from the spirit and scope of the invention as defined by the appended claims. Transform. Further, the scope of the invention is not limited to the specific embodiments of the processes, apparatus, means, methods and steps described in the specification. It will be readily apparent to those skilled in the art from this disclosure that the present invention can be used in accordance with the present invention to perform substantially the same functions as the corresponding embodiments described herein or to obtain substantially the same results as the present and future The process, equipment, means, method or step being developed. Therefore, the appended claims are intended to cover such a process, apparatus, means, methods or steps.

Claims

权利要求书 claims

1、一种基于 LaB6纳米材料热发射的 X射线管，其特征在于，包括：阳极、阴极和管壳；所述管壳用于支撑所述阳极和所述阴极，并使得所述阳极和所述阴极的工作环境与外界绝缘，保持所述工作环境为真空；所述阴极采用 LaB6纳米材料制成，且所述阴极在加热到 LaB6纳米材料的工作温度时，热发射的电子轰击所述阳极以产生 X射线。 1. An X-ray tube based on thermal emission of LaB6 nanomaterial, characterized in that it includes: an anode, a cathode and a tube shell; the tube shell is used to support the anode and the cathode, and make the anode and the The working environment of the cathode is insulated from the outside world, and the working environment is kept in a vacuum; the cathode is made of LaB6 nanomaterial, and when the cathode is heated to the working temperature of the LaB6 nanomaterial, thermally emitted electrons bombard the anode to produce X-rays.

2、根据权利要求 1所述的基于 LaB6纳米材料热发射的 X射线管，其特征在于，采用 LaB6纳米材料制成的所述阴极的热发射面为连续平面。 2. The X-ray tube based on thermal emission of LaB6 nanomaterial according to claim 1, characterized in that the thermal emission surface of the cathode made of LaB6 nanomaterial is a continuous plane.

3、才权利要求 1所述的基于 LaB6纳糾料热发射的 X射线管，膽于，所述阳所述阴极之间还设有栅极，在所述栅所述阳极之间外加电场以加速斤述阴极热发射的电子，使之轰击所述阳极以产生 X射线。 3. The X-ray tube based on thermal emission of LaB6 nanomaterial according to claim 1, further, a grid is provided between the anode and the cathode, and an electric field is applied between the grid and the anode to Electrons thermally emitted by the cathode are accelerated so that they bombard the anode to produce X-rays.

4、根据权利要求 3所述的基于 LaB6纳米材料热发射的 X射线管，其特征在于，所述栅极为金属网栅极。 4. The X-ray tube based on thermal emission of LaB6 nanomaterial according to claim 3, characterized in that the grid is a metal mesh grid.

5、根据权利要求 1所述的基于 LaB6纳米材料热发射的 X射线管，其特征在于，所述阳极为固定式阳极或者旋转式阳极。 5. The X-ray tube based on thermal emission of LaB6 nanomaterial according to claim 1, characterized in that the anode is a fixed anode or a rotating anode.

6、根据权利要求 5所述的基于 LaB6纳米热材料发射的 X射线管，其特征在于，所述固定式阳极包括：固定的铜阳极体以及固定于所述铜阳极体上的钨合金靶面。 6. The X-ray tube emitted based on LaB6 nanothermal material according to claim 5, characterized in that the fixed anode includes: a fixed copper anode body and a tungsten alloy target surface fixed on the copper anode body .

7、根据权利要求 6所述的基于 LaB6纳米材料热发射的 X射线管，其特征在于，所述钨合金靶面相对参考方向形成有预定的靶面倾角，所述参考方向与电子入射方向垂直。 7. The X-ray tube based on thermal emission of LaB6 nanomaterial according to claim 6, characterized in that the tungsten alloy target surface forms a predetermined target surface inclination angle relative to a reference direction, and the reference direction is perpendicular to the electron incident direction. .

8、根据权利要求 7所述的基于 LaB6纳米材料热发射的 X射线管，其特征在于，所述钨合金靶面的厚度为 400-500um，和 /或，所述靶面倾角为 11度。 8. The X-ray tube based on thermal emission of LaB6 nanomaterial according to claim 7, characterized in that the thickness of the tungsten alloy target surface is 400-500um, and/or the inclination angle of the target surface is 11 degrees.

9、根据权利要求 1所述的基于 LaB6纳米材料热发射的 X射线管，其特征在于，所述 X射线管总长度小于或等于 120mm，和 /或，所述 X 射线管的最大直径小于或等于 60mm，和 /或，所述 X射线管的同心度小于 1，和 /或，所述阳极和所述阴极的距离小于或等于 10um。 9. The X-ray tube based on thermal emission of LaB6 nanomaterial according to claim 1, characterized in that the total length of the X-ray tube is less than or equal to 120 mm, and/or the maximum diameter of the X-ray tube is less than or equal to Equal to 60mm, and/or, the concentricity of the X-ray tube is less than 1, and/or, the distance between the anode and the cathode is less than or equal to 10um.

10、一种移动 CT扫描仪，其特征在于，包括如权利要求 1-9任一所述的基于 LaB6纳米材料热发射的 X射线管。 10. A mobile CT scanner, characterized by including an X-ray tube based on thermal emission of LaB6 nanomaterial as described in any one of claims 1-9.