X-ray tube with field-radiating cathode

FIELD: flaw inspections, customs examination equipment, medicine, and roentgen diagnosing spectroscopic installations.

SUBSTANCE: proposed X-ray tube has vacuum envelope accommodating anode, X-ray output aperture, cathode assembly incorporating field-radiating cathode in the form of bundle of carbon fibers placed in conducting or semiconducting shell, contact assembly of field-radiating cathode, and cap that functions as control electrode. In order to prevent stray surface electric conductance caused by sputtering of field-radiating cathode material on structural components of X-ray tube, dielectric washer is inserted in this tube wherein during X-ray tube assembly annular cavity is formed between inner hole of washer, field-radiating cathode shell, and upper end of field-radiating cathode contact assembly. Cavity provided in dielectric washer and also its slots prevent formation of solid conducting and semiconducting films which enhances stability of electrical and radiating characteristics of tube. For raising electric strength of tube and excluding breakdown of its envelope cap is installed on dielectric washer that functions as control electrode. Cap is installed so that axis of carbon fiber bundle is aligned with that of optoelectronic system of X-ray tube and symmetry axis of cap.

EFFECT: enhanced operating stability, electric strength, reliability, and service life of X-ray tubes with field-radiating cathode.

1 cl, 3 dwg

 

The invention relates to x-ray tubes, containing automated made on the basis of the carbon materials, and can be used as an x-ray source in the instrument testing, inspection equipment, medical x-ray apparatus, diagnostic facilities x-ray spectroscopy.

Known x-ray tube containing enclosed in a vacuum flask anode, control electrode, a window for displaying x-ray radiation as a source of electrons; [1]. Such x-ray tube is powered by a high voltage power source and from the source to the filament cathode. The cost of power to heat the cathode reduces the efficiency of the tube. In addition, the required heating of the cathode leads to the production of heat and undesirable heating of the x-ray tube.

Also known x-ray tube, which contains enclosed in a vacuum flask anode and automated made of carbon fibers, consisting of a large number of carbon fibers [2], and a window for displaying x-ray radiation. However, in the known device does not provide protection dielectric part of the membrane of the x-ray tube from its irradiation by electrons from automated and from its dust products cathode sputtering when operating x-ray tube. In addition, lack the t the possibility of changing or adjusting the current x-ray tube and the x-ray intensity at a constant high voltage.

Closest to the technical essence and the achieved result of the claimed invention is the x-ray tube [3], containing enclosed in a vacuum flask automated and the anode with electrical connection, a control electrode in the form of a mesh window for displaying x-ray radiation. As automated used nanostructured carbon film fixed inside the x-ray tube and film selected from the group comprising nanocrystalline graphite, carbon nanotubes, diamond, diamond-like carbon, or a combination of two or more elements selected from this group.

However, in the known device does not provide protection dielectric part of the membrane of the x-ray tube from its irradiation by electrons from automated and from its dust products cathode sputtering when operating x-ray tube.

These factors result in the reduction of electrodiagnostic, reliability and durability of the x-ray tube due to the formation of conductive films and progressive conductivity between the electrodes of the x-ray tube and do not allow to obtain a field emission and x-ray radiation with repeatable characteristics.

The aim of the present invention is to improve stability, electrodiagnostic, reliability, and took the prolong service life of x-ray tubes with automatedly.

This goal is achieved by the fact that in the proposed x-ray tube containing placed in a vacuum flask electron-optical system consisting of automated, made of carbon material, the anode and the electrical pins and a window for displaying x-ray radiation, automated made in the form of a bundle of carbon fibers that are enclosed in the shell and connected through a contact node automated with electric output, and placed inside the holes have been added to the dielectric spacers in such a way that between the shell automated, the walls of the holes in the washer and the end of the contact node is formed a cavity in the dielectric washer still has a cap with an electric output in its end wall, perform the function of the control electrode, and the axis of the bundle of carbon fibers coincides with the axis of the electron optical system of the x-ray tube and the axis of symmetry of the holes in the cap.

The proposed design is illustrated by drawings.

Figure 1 presents the design of the x-ray tube Assembly.

Figure 2 presents the dielectric washer executed by longitudinal grooves.

Figure 3 presents the dielectric washer executed by transverse grooves.

X-ray tube (figure 1) contains placed in a vacuum to the company code 1 field gun 2, the anode 3 made, in particular, the chamber, the window for displaying x-ray radiation 4. As for field guns 2, it contains automated 5, cap 6 with an electric output 7, the dielectric washer 8, the contact node automated 9

The bundle of carbon fibers 10 is enclosed in the casing 11 to provide orientation of the carbon fibers and their mechanical fasteners and provide resistance to vibration. The shell 11 is made of conductive or semi-conductive material, for example, from Windows Explorer, semi-conducting glass or metal on a dielectric surface, i.e. a material excluding the random change of the membrane potential relative to the bundle of carbon fibers when operating x-ray tube. The bundle of carbon fibers 10 from the emitter protrudes from the shell 11. For a span of autoelectronic from the cathode to the anode in the end wall of the cap 6, performs the function of the control electrode of the tube, made aperture in the form of holes 12.

Contact node automated 9 made of electrically conductive material 13, for example, from a conductive paste based powder of Ag, Al or other metals or conductive materials. The specified material 13 deposited on the opposite from the emitter end of the bundle of carbon fibers and a portion of the shell, objetos metal shell 14, which can be made is, for example, in the form of a cylinder or a cylinder cut by a plane through its axis. Shell 14 has an electric (cathode) output 15 of the vacuum bulb 1 and rigidly connected with the dielectric plate 8, for example, by cement, glue or the hardened resin. While the Central axis of the shell 14, the bundle of carbon fibers 10 enclosed in the casing 11, and the hole of the dielectric spacers 8 are aligned with the axis of the electron optical system of the x-ray tube.

The Assembly of tubes perform in such a way that between the inner walls of the holes in the washer 8, the shell 11 and the upper end of the contact node 9 is formed cavity 16. This cavity is designed to prevent the formation of surface conductivity between the cathode 5 and a control electrode 6 that occur due to the formation of semi-conductive and conductive films and tracks on the shell surfaces of the cathode 11, the dielectric spacers 8 and the control electrode 6. Conductive and semi-conductive film are formed during thermal processing of x-ray tube, and the sputtering of cathode material exposed to ionic bombardment, and the breakdown between the electrodes of the x-ray tube that arise during training and in the process the x-ray tube.

To prevent the formation of these films DOP is niteline to the cavity 16 in the dielectric washer 8 can be performed longitudinal 17 (2) and/or cross-section 18 (3) protective grooves, increasing the surface strength of the dielectric washer 8 and prevents the formation of surface conductivity between autocatalog 5 and a control electrode 6. Protective grooves 17 and 18 to increase the distance between the cathode 5 and a control electrode 6 and prevent the formation of parasitic conductive films. Washer 8 with protective grooves 17 and 18 may be set, for example, from a separate washers with holes and in addition to the dielectric elements may be metal elements, fastening the individual parts washer 8 in whole. Border typesetting washers figure 2 and 3 shown by the dotted line.

The durability of the x-ray tube is proportional to the number of grooves and their depth, because the more the slots in the washer, the larger the area of the shadow, i.e. nezavisimykh plots washers and the higher its strength and, accordingly, the durability and reliability of the x-ray tube.

The number performed in dielectric washer grooves, their geometrical shape and dimensions are the dimensions of the field gun in the x-ray tube and, as a consequence, the dimensions of the dielectric spacers, and technological equipment.

X-ray tube operates as follows. When applying to the anode 3 high positive potential relative to the cathode 5 and nab is agenia between autocatalog 5 and a control electrode 6 with the ends of carbon fibers, projecting from the shell 11, there is autoelectronic emission. On the surface the ends of the carbon fibers extend numerous fibrils is elongated along the axis of the fibers tetragonal crystal formation of carbon length 250-1000and a diameter of 20-50They are the center of the field emission of carbon fibers. Avtoelektrika from the cathode 5 are emitted through the opening 12 made in the end wall of the cap 6, and are in a strong accelerating electric field between the anode 3 and the cap 6. Diaphragmalyse hole 12 in the cap 6 allows Avtoelektrika to fly only on the anode 3, preventing the ingress of autoelectronic with the cathode on the dielectric portion of the shell 1 x-ray tube. The placement of the cathode node, consisting of automated 5, dielectric Sabi 8 and the contact node automated 9, in the cavity of the cap 6 excludes electrons from automated 5 on the inner surface of the dielectric vacuum bulb 1 x-ray tube. The result is increased strength of the tube, as it eliminates the possibility of charging and subsequent breakdown of the dielectric coating of the vacuum flask.

As a result of bombardment of the anode by high-energy electrons occurs x-rays, the rays which emerge from the Tr is the KJV through the window 4. When the change of potential on the cap 6, performs the function of the control electrode, changing the value of electric field intensity at the face surface emitting carbon fiber automated 5 and, thus, regulate the current x-ray tube and the x-ray intensity.

In the process of x-ray tube between the electrodes, due to ion bombardment and sputtering of carbon fibers automated and sheath material, on the gate electrode, the membrane between the electrodes, as well as on the surface of the bonding electrode dielectric can be formed conductive and semi-conductive film. The appearance of the films leads to an increase in parasitic conductivity between the electrodes of the x-ray tube, changes its characteristics, deteriorating the strength, reliability, reduced durability.

Addressing these deficiencies is achieved in the proposed design use in an electron gun of the dielectric washer 8, in the upper part of which is a 17 vertical and/or horizontal grooves. In addition, automated 5 is placed in a dielectric washer 8 so that between the Central hole in the washer 8 and the shell 11, which is enclosed bundle of carbon fibers 10, there is formed the cavity 16. She can have, for example, an annular shape. the moreover, introduction dielectric washer provides centering and aligning automated 5 in the optical system, which allows to increase the frequency of emission and radiative characteristics of the x-ray tube. The formation of the cavity 16 between the shell 11 and the dielectric plate 8, and running grooves 17 (2) and 18 (figure 3) in dielectric washer 8 prevents the formation of continuous conductive and semi-conductive film between the cathode and control electrode 6 on the surface of the dielectric washer 8. This is because in the process of x-ray tube in the cavity 16 and the grooves 17 and 18 are formed closed contour around the cathode, a “shadow” for dusty areas, on which the products cathode sputtering to get into the process tube can't. Therefore, a conductive film on the surface of the dielectric washer 8 will be closed contour, not dusty areas (gaps) in the cavity 16 and the grooves 17 and 18, to prevent the appearance of spurious conductivity between the cathode 5 and a control electrode 6.

The tests of the inventive x-ray tube of a type of miniature, confirmed the effectiveness of its design solutions. The tube voltage of 50 kV and a current of 100 μa worked without failures more than 10,000 hours, which indicates its high reliability and electrodiagnostic this instability characteristics of the x-ray tube was less than 1%.

Sources of information

1. Patent EP No. 1037248, IPC H 01 J 9/32, H 01 J 35/02, 20.09.2000.

2. The US patent No. 3883760, IPC H 01 J 35/06, 13.05.1975.

3. The application for US patent No. 2003/0002627 A1, IPC H 01 J 35/06 published 2 Jan. 2003 - the prototype.

X-ray tube containing placed in the vacuum shell electron-optical system consisting of automated and anode with electrical connection, a control electrode and a window for displaying x-ray radiation, characterized in that automated made in the form of a bundle of carbon fibers that are enclosed in the shell and connected through a contact node automated with electric output, and placed inside the holes in the added dielectric washer so that the shell automated, the walls of the holes in the washer and the end of the contact node is formed cavity, the control electrode is made in the form of a cap with an electrical outlet and a hole in its end wall, still mounted on the dielectric plate and the axis of the bundle of carbon fibers coincides with the axis of the electron optical system of the x-ray tube and the axis of symmetry of the holes in the cap.



 

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