Pulse-type x-ray tube. RU patent 2521433.

IPC classes for russian patent Pulse-type x-ray tube. RU patent 2521433. (RU 2521433):

H01J35/00 - X-ray tubes (X-ray lasers H01S0004000000; X-ray technique in general H05G)

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FIELD: measurement equipment.

SUBSTANCE: invention refers to X-ray equipment and can be used for the development of pulse-type X-ray tubes to be applied in small X-ray apparatuses. A pulse-type X-ray tube comprises a metal casing in the form of a hollow cylinder with one its base being connected to the greater base of an insulator which is made as a hollow truncated cone and set beyond the casing, and the other casing base being connected to a X-radiation output window and a cathode, a pointed anode passes through the hole in the centre of the cathode perpendicular to the latter in the direction to the window. The tube is fitted by the first protective shield presented as a cup formed by a hollow cylinder with one its base being connected to the casing and the other - to the greater base of the hollow truncated cone while the smaller base of the latter with a hole in the centre is turned to the smaller base of the insulator. The pointed anode terminal passes through the hole in the first protective shield to the insulator cavity and is connected to its smaller base. The second protective shield, for example, made as a disk, coaxial to the pointed anode and installed in the same volume with it with the volume being limited by the first protective shield, and diameters of the hole in the cathode D₁, of the second protective shield D₂, of the hole in the first protective shield D₃, distance between the upper surface of the second protective shield and the plane of the cathode location S₁, distance between the upper surface of the second protective shield and the outer surface of the smaller base of the hollow truncated cone at the first protective shield S₂ are interrelated according to the following ratio (D₂-D₁)/S₁≥(D₃-D₂)/S₂, the cathode is made from the material having surface nanostructure, for example, from polyacrylonitrile carbon fibres set on a substrate and directed by the radius perpendicular to the device axis, the end faces of the carbon fibres form the border of the cathode hole and are fixed on the substrate by, for example, a metal disk in the form of a ring by spot welding.

EFFECT: provision for X-radiation in soft range ensuring high contrast image when working with the objects of different optical density.

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The invention relates to the field of x-ray technology and can be used in the development of pulsed x-ray tubes for use in small-size x-ray machines, in particular for medical diagnostics and treatment of diseases, as well as in other areas of technology.

Known pulse x-ray tube containing metal case with " through " the target and the window for displaying x-ray radiation, the cathode, internal isolating element, in this case the target is separated from the window and fastened in a hollow tube with two cylindrical rings having a tooth and a groove so that the gap between the target and the cathode is made within ratios from 1:20 to 1:5 to the outer diameter of the cathode [RF Patent №2160480, 01J 35/00, H01J 35/02, H05G 1/02, 2000].

This design has small dimensions and, upon application of the pulse of accelerating voltage of 100 kV, with the duration of 1.5·10 -10 with electronic current between the cathode target is more than 10 kA, and the dose of x-ray radiation from the outer surface of the output window reaches of 0.01 Grams per pulse. The use of tantalum as the material of electrodes offers several advantages compared to other materials such as tungsten. Tantalum has a lower output operation of the electrodes, which increases the radiation intensity by about 10-20%.

The disadvantages of this pulse x-ray tube should be attributed to low resource stable operation at voltage at the anode less than 100 kV. It is known that in the process of explosive electron emission is the destruction of microstrip cathode surface with the formation of new microstrip from one pulse to, the nature of microstrip depends on the input of energy in the cathode. When the voltage at the anode less than 100 kV in the process of elaboration is smoothing microstrip, reducing the gain of the external field on the cathode surface (polished effect). In this case the pulse x-ray tube cannot be used at low operating voltages (<100 kW) for reception of soft radiation range.

Also known pulse x-ray tube containing vakuumirovannoj case, the anode and mounted on the high-voltage bushing insulator with explosive-emission cathode, made of a material with nanostructure surfaces, for example, based on graphite or carbon fibres of polyacrylonitrile [RF Patent №2308781, H01J 35/00, 2007].

The main advantage of this x-ray tube in comparison with tubes with cathodes from a metal, is to increase resource stable operation and expansion of functional possibilities of x-ray unit by producing of soft radiation range, providing high contrast images when working with objects of different optical density.

The disadvantages include a limited life due to the small working surface of the cathode defined by the selected design and method of manufacture. In this design of the cathode limited number emitting centers, as well as a high level of potential field emission, which reduces the intensity of x-ray radiation, and hence the efficiency of the tube.

The domestic industry produces polyacrylonitrile fiber carbon in the form of bundles of hundreds and even thousands of single fibers with diameter from 2 to 10 microns. Individual thin thread of these fibers do not have sufficient mechanical strength and in the manufacture of pulsed x-ray tubes in particular in the process of pumping when outgassing going in the electrode gap and create electrical leakage to units of IOM. This General lack of carbon fibres of polyacrylonitrile eliminated technological operations or constructive decision - carbon cleanup from light fractions of carbon threads should not fall on the inner membrane of the insulator

Closest to the proposed invention is a pulse x-ray tube containing a metal case in the form of a hollow cylinder, the base of which is connected with a large base insulator, made in the form of a hollow truncated cone and located outside of the body, and other Foundation of the building are connected with window for output of x-ray radiation and cathode, through the hole in the center of which in the direction perpendicular to the window cathode passes ostrinia the anode, the first protective shield formed a hollow cylinder, United by one basis with the case, and other - with a large base of hollow truncated cone, less the basis of which with a hole in the center facing the smaller base insulator, conclusion stringo anode through a hole in the ground protective screen in the cavity of the facility and connected to it a smaller base, the second protective screen in the form of a disk, coaxial astronomy the anode and set him in the volume, limited to the first protective screen, and the diameters of the holes in the cathode D 1 , the second protective screen D 2 , holes in the ground the shield D 3 , the distance between the upper surface of the second protective screen the location plane cathode S 1 , the distance between the upper surface of the second protective screen and the outer surface of the smaller base of hollow truncated cone first protective screen TV S 2 are connected by the relation (D 2-D-1 )/S 1 & GE; (D 3-D 2 )/S 2 [RF Patent №2446508, H01J 35/00, 2012 - a prototype].

The first protective screen in the form of a hollow-shaped glass, consisting of a cylinder and a truncated cone, allows you to select the dimensions and location of the construction elements of x-ray tube according to the specified value, where there is no direct exposure to the products of erosion material of electrodes formed as a result of vacuum discharge, on the inner surface of the insulator, which reduces deposition of erosion products on this surface, providing, thus, greater durability x-ray tube.

The disadvantage of this design is that it allows to receive soft x-ray radiation in a restricted mode.

The objective of the invention is the creation of pulse x-ray tube radiation soft range, providing high image contrast when working with objects of different optical density.

This technical result is achieved by the famous pulse x-ray tube containing a metal case in the form of a hollow cylinder, the base of which is connected with a large base insulator, made in the form of a hollow of a truncated cone and located outside of the body, and other Foundation of the building are connected with window for output of x-ray radiation and cathode, through the hole in the center of which in the direction perpendicular to the window cathode passes ostrinia the anode, the first protective shield formed a hollow cylinder, United by one basis with the case, and the other with a large base of hollow truncated cone, less the basis of which with a hole in the center facing the smaller base insulator, conclusion stringo anode through a hole in the ground protective screen in the cavity of the facility and connected with its smaller base, the second protective screen, for example, in the form of a disk, coaxial astronomy the anode and set him in the volume, limited to the first protective screen, and the diameters of the holes in the cathode D 1 , the second protective screen D 2 , holes in the ground the shield D 3 , the distance between the upper surface of the second protective screen and location plane cathode S 1 , the distance between the upper surface of the second protective screen and the outer surface of the smaller base of hollow truncated cone first protective screen TV S 2 are connected by the relation (D 3-D 1 )/S 1 & GE; (D 3-D 2 )/S 2 , cathode made from a material with nanostructure surfaces, for example, from polyacrylonitrile carbon fibers, located on the substrate and directed by radius perpendicular to the axis of the device, the ends of polyacrylonitrile carbon fibers form the boundary of the holes of the cathode and fixed on a backing, for example, by means of a metal disc in the form of rings by means of spot welding.

Pulse x-ray tube cathode given configuration allows to receive high-power radiation soft range, providing high contrast images when working with objects of different optical density.

To check inventive step was held an additional search of the known solutions, the results of which show that the claimed invention is not necessary for a specialist explicitly from the prior art, as it is not identified technical solutions enabling to get x-rays, high-power soft range, due to the performance of the cathode of carbon fibres of polyacrylonitrile, located in the plane perpendicular astronomy the anode, and directed by radius to the axis of the device so that the inner ends of the fibers form a hole in the cathode, fixed on a backing, for example through a thin metallic disk and spot welding.

Therefore, the claimed invention meets the requirement of "inventive step" by applicable law.

The declared technical solution is illustrated by a drawing.

Figure 1 shows one of the options stated pulse x-ray tube.

Pulse x-ray tube (figure 1) contains a metal body 1 in the form of a hollow cylinder, the base of which is connected with a large base insulator 2, executed in the form of a hollow truncated cone and located outside of the housing 1, and the other case base 1 are connected with window of 3 in the form of a cylinder, with the bottom of beryllium for output of soft x-rays, and through the holder 4 (liner) to the cathode 5, made of carbon fibres of polyacrylonitrile, laid on the holder 4 in the plane perpendicular to the axis stringo anode 6 tantalum, and attached to the holder (substrate) 4 thin metal ring disc 7 through spot welding, with polyacrylonitrile fiber carbon sent by radius to the axis of the device so that the inner ends of the fibers form a hole in the cathode through which in direction open 3 passes anode 6, the first protective screen 8 in the form of a cylindrical glass, the edges of which are connected with the upper base of the case 1, the bottom is made in the form of a hollow truncated cone with a bore diameter D 3 , and the first protective screen 8 limits the amount, which has ostrinia anode 6 and a second protective screen 9 in the form of a disk with diameter D 3 , located under the edge of the anode, the conclusion of the anode 10 through a hole in the ground protective screen 8 in cavity 2 detention centre, and connected to it a smaller base, Stengel 11 for pumping of x-ray pipes, and the location plane cathode 5 and the external surface of the smaller base of hollow truncated cone first protective screen 8 deleted from the upper surface of the second protective screen 8 distances S 1 and S-3, respectively.

When applying a pulse of high voltage at the anode 6 (the cathode is grounded 5) in interelectrode space creates a high electric field, which causes the explosive electron emission from microstrip cathode 5 with the formation of the flow of electrons, moving to the anode 6. In the result of collision of electrons with anode 6 and braking generation of soft x-rays. In the process of x-ray tube, the claimed design, vacuum breakdown between the cathode 5 and 6 anode is cleaned interelectrode space from light fraction thin carbon fibres obtained in the process of production of pipes, in particular when pumping, the outgassing of the device and the spraying of cathode material, the products spray (carbon) under the effect of electrodynamic forces moved on volume of x-ray tube, colliding with the inner surface shell tube from Windows 3, with surfaces of protective screens 8 and 9, are deposited practically not getting on the inner surface of the insulator 2, which increases the electric strength of the x-ray tube and its resources.

On the basis of the claimed invention created a prototype of the pulse x-ray tube in which D 1 =6 mm, D 2 =11 mm, l 3 =13.5 mm, S 1 =7 mm, S 2 =18 mm, cathode of carbon fibres of polyacrylonitrile (ribbon "Pendant"). Tests of the x-ray tube was conducted in the laboratory of St. PETERSBURG State University of telecommunications. A potential electrode x-ray tube pulse was applied voltage from the generator nanosecond voltage pulses with variable duration 10-80 the national Assembly and the amplitude of 15-80 kV. In the specified ranges of variation of the amplitude and pulse duration was observed powerful soft x-ray radiation, fixed on the glowing fluorescent screen.

Thus, the claimed solution allows you to create pulse x-ray tube with a soft x-ray radiation, providing high contrast images when working with objects of different optical density.

Pulse x-ray tube containing a metal case in the form of a hollow cylinder, the base of which is connected with a large base insulator, made in the form of a hollow truncated cone and located outside of the body, and other Foundation of the building are connected with window for output of x-ray radiation and cathode, through the hole in the center of which in the direction perpendicular to the window cathode passes ostrinia the anode, the first protective shield formed a hollow cylinder, United by one basis with the case, and the other with a large base of hollow truncated cone, smaller base of which with a hole in the center facing the smaller base insulator, conclusion stringo anode through a hole in the ground protective screen in the cavity of the facility and connected to it a smaller base, the second protective screen, for example, in the form of a disk, coaxial astronomy the anode and set him in the volume, limited to the first protective screen, and the diameters of the holes in the cathode D 1 , the second protective screen D 2 , holes in the ground the shield D 3 , the distance between the upper surface of the second protective screen and location plane cathode S 1 , the distance between the upper surface of the second protective screen and the outer surface of the smaller base of hollow truncated cone first protective screen TV S 2 are connected by the relation (D 2-D-1 )/S 1 & GE; (D 3-D 2 )/S 2 , characterized in that the cathode is made of material with nanostructure surfaces, for example, from polyacrylonitrile carbon fibers, located on the substrate and directed by radius perpendicular to the axis of the device, while the ends of carbon fibers form the boundary of the holes of the cathode and fixed on a backing, for example, by means of a metal disc in the form of rings by means of spot welding.