Compact x-ray generator

 

(57) Abstract:

Usage: in rechentechnik and can be used in the design and manufacture of compact x-ray generators. The essence of the invention: improved efficiency by providing the possibility of pre-adjustment of the trajectory of the electron beam in the x-ray tube. The latter is achieved in the design complexity of at least one of the shielding ring and use advanced two controllable voltage dividers and two corresponding controls. 4 Il.

The invention relates to rechentechnik and can be used in the design and manufacture of compact x-ray generators.

Known x-ray generator, comprising a housing in which are located three-electrode x-ray tube and sectional diode-capacitor voltage multiplier, made under the scheme of Cockroft-Walton; the multiplier is set coaxially with the x-ray tube and made in the form of two diametrically arranged raising and leveling of columns, each section of which has a single point of doubling the voltage. A disadvantage of the known generators is UEMOA technical solution is a compact x-ray generator, comprising a housing in which are located three-electrode x-ray tube and sectional diode-capacitor voltage multiplier, made under the scheme of Cockroft-Walton, while the diode-capacitor multiplier is installed coaxially with the x-ray tube and made in the form of two diametrically located multiplying columns and the alignment columns, each section of which has a single point of doubling the voltage, as well as screening tools, in the form of metal rings mounted coaxially x-ray tube, each ring is electrically connected with the point of voltage doubling opposite him partitions voltage multiplier [2] .

Generator-the prototype is small, involves the use of a three-electrode x-ray tube and provides the opportunity to work with the anode voltage of 100 kV. The disadvantage of the generator prototype is a relatively low efficiency; the latter is due to the fact that the Assembly and adjustment of the generator not possible to accurately project the electron beam in the x-ray tube on the target anode. This reduces the dose rate at the output of generowanie efficiency of the x-ray generator by extending its functionality by providing the possibility of pre-adjustment of the trajectory of the electron beam in the x-ray tube.

The goal in a known compact x-ray generator, comprising a housing in which are located three-electrode x-ray tube and sectional diode-capacitor voltage multiplier, made under the scheme of Cockroft-Walton, while the diode-capacitor multiplier is installed coaxially with the x-ray tube and made in the form of two diametrically located multiplying columns and the alignment columns, each section of which has a single point of doubling the voltage, as well as screening tools, in the form of metal rings mounted coaxially x-ray tube, each ring is electrically connected with the point of voltage doubling opposite him partitions voltage multiplier, is due to the fact that at least one, for example n-e, the metal ring of shielding provided with first and second sector of the metallic elements, the voltage multiplier circuit is further provided with first and second controllable voltage dividers, each having one managed element and one middle point, and first and second control means, while the first and second metal elements of the n-th ring is made Tela voltage electrically connected with the point of doubling voltage n-1-th section of the voltage multiplier, the second terminals of the voltage dividers are electrically connected with the point of voltage doubling n+1-th section of the voltage multiplier, the midpoint of the first voltage divider is electrically connected with the first element of the n-th metal rings, the midpoint of the second voltage divider is electrically connected with the second element of the n-th metal rings, the first controls the contactless related to the driven element of the first voltage divider, and the second controls the contactless related to the driven element of the second voltage divider.

In Fig. 1 shows a simplified construction of the compact generator of Fig. 2 is a diagram of the sections of the voltage multiplier circuit, electrically connected with the metal shielding ring and its elements; Fig. 3 schematically shows the placement of components dividers and controls sections of the voltage multiplier of Fig. 4 illustrates the principle of control by the trajectory of the electron beam in the x-ray tube.

X-ray generator is assembled in a metal case 1. Coaxial with the three-electrode tube 2 that is installed inside the housing 1 and having three electrodes (anode, cathode, grid and filament), is sextasy increase of 5 and leveling 6 columns, located diametrically opposite one another relative to the axis of the tube 2. Columns 5, 6 multiplier 3 consist of a series of sections 7 arranged in series one behind the other along the x-ray tube 2, which provides a uniform increase in capacity in the direction from the cathode to the anode 2 [2] .

The electrical circuit sections 7 (n-1-I, n-I and n+1-I section) multiplier 3 voltage shown in Fig. 2. Each section 7 contains at least two capacitor 8, 9 (C1, C2) and two diodes 10, 11 (D1, D2) connected according to the scheme of Comfort-Walton and providing a doubling of the capacity of each section 7, each section corresponds to one point of doubling the voltage, which results in a doubling of capacity in relation to the potential of similar points in the previous section.

The multiplier 3 voltage includes first managed divider 12 voltage, consisting of series-connected first resistor 13 (R1), a managed element 15, the second resistor 14 (R 2). The first output of the divider 12 (the output resistor R1) is electrically connected with the point of doubling voltage n-1-th section 7, and the second output of the divider 12 (the output resistor R 2) is electrically connected to a point of voltage doubling n+1-th section 7.tion included the third resistor 17 (R 3), a managed element 19 and the fourth resistor 18 (R 4). The first output of the divider 16 (the output resistor R 4) is electrically connected with the point of doubling voltage n-1-th section 7, and the second output of the divider 16 (the output resistor R 3) is electrically connected to a point of voltage doubling n+1-th section 7.

The multiplier 3 voltage includes first means 20 of the control, contactless associated with the managed element 15 of the divider 12, and the second means 21 of the control, contactless associated with the managed element 19 of the divider 16. As managed elements 15, 19 can be used fotopribor variable resistance value (for example, a photosensitive or photoconductive), and as a means 20, 21 controls can be used in light-emitting devices (for example, incandescent bulbs or LEDs with variable power of the glow). Controls and a managed element can be combined within a single device - power optocoupler, which does not reach beyond the boundaries of the scope of the invention. Resistors R1, R3 can have the same nominal values, the smaller of the resistors R2, R4, ensuring implementation of the required adjustment range of the voltages at the outputs of the dividers 12, 16. As the outputs of the dividers use the element 19 and the resistor 18.

The dividers 12, 16 and means 20, 21 control constructively placed in sections 17 multiplier 3 voltage (in this example, the n-th and n+1-th section, see Fig. 3). This means 20, 21 management and related items 15, 19 should be placed in sections opposite each other, and between them, should be free channel (for example, when filling) for the implementation of proximity (for example, optical interaction). In addition, you should place the tools 20, 21 control as far as possible from the other elements of section 7 in order to avoid electrical breakdown. Withdrawals 20, 21 of the control are displayed through a wired connection to the surface of the multiplier 3 voltage in the region of the cathode tube 2, which provides easy access to the controls in the setup process.

Between the x-ray tube 2 and each section 7 of the multiplier 3 voltage set cylindrical metal ring 22 is electrically connected with the point of voltage doubling this section 7. A set of metal rings 22 forms a means of shielding the x-ray tube 2. In the proposed x-ray generator is at least one metal ring 22 (for example, n-first - 23 and second 24. These elements are electrically isolated to each other and relative to the ring 22. The axis of the elements 23, 22 spaced to each other by an angle of 90aboutand the corresponding sector angles of about 60about(see Fig. 2). The first element 23 of the ring 22 is electrically connected to the middle point of the first divider 12 voltage multiplier 3 voltage. High voltage resulting from the conversion multiplier 3 AC voltage of the transformer is fed from the output of the second section 7 of the multiplier 3 anode x-ray tube 2, resulting in the formation of a high voltage (about 80-100 kV) potential difference between anode and cathode (filament) of the tube 2.

Heater supply tube 2 are external to the generator low voltage power supply (Fig. 1 is not shown). When applying to the control electrode of tube 2 (grid) of the triggering voltage pulses (in the conditions of submission of the anode and filament voltages) x-ray generator must generate at the output of the x-ray pulses with a pattern, bearing symmetrical character.

The amplitude of these pulses (i.e. actually on Velenje nature of electron beam irradiation "through" the target anode x-ray tube 2. In practice, the focused electron beam in the x-ray tube is sometimes not completely irradiates the target anode, which causes a decrease in the amplitude of the output x-ray pulse and waveform distortion pattern at the output of the x-ray generator. Such displacement of the electron beam relative to the target may be inherent in the x-ray tube 2 or occur during operation due to the aging of the target (such deficiencies are not always detected when the output control tube on the manufacturer and can lead to the rapid replacement of tubes in operation).

To address these shortcomings in the proposed generator are two (at least) the control electrode (two segmented metal element 23, 24 of the ring 22). By feeding on these electrodes control voltages that differ somewhat from the potential of the ring 22 (differences can be up to U= 1kV), can provide the ability to control the trajectory of the electron beam in the tube 2.

The ring 22 is used solely for the purpose of shielding the x-ray tube from the influence of external electrostatic fields.

So agenie UnU. This voltage is generated at the output of the first controlled voltage divider in the submission of the corresponding impact on its managed element 15. Control action, usually formed by a circuit that is external to the generator, and is transmitted through the first means 20 controls. The use of the above means (a control electrode, a voltage divider and controls) allows you to control the trajectory of the electron beam (to the extent necessary) in the same plane of the tube 2. Accordingly, the second control electrode (element 24 of the ring 22), the second voltage divider and the second means 21 of the control allows the correction of the trajectory of the electron beam in another plane of tube 2 (orthogonal to the first plane). Enabling correction of the trajectory of the electron beam two-dimensionally accurately project the focused electron beam on the target anode and on that basis significantly (30-50% ) to increase the amplitude of the output pulses of the generator (and hence the magnitude of the efficiency of the generator), as well as to approximate the shape of the output beam to symmetric. External is the use of regulated DC power source when performing the initial setup of the generator in terms of its manufacture) or automatically (for example, during operation of the generator with the use of appropriate radiation detectors controlling the output signal of the generator, and schema conversion and formation control action). These control schemes, except for the controls 20, 21, are external in relation to the proposed generator and beyond the scope of the invention.

Thus, in the proposed compact x-ray generator while maintaining the same dimensions by expanding its functionality associated with the use of means of correction of the trajectory of the electron beam in the x-ray tube is increased, the generator efficiency and the improvement of its output beam. The latter also facilitates adjustment of the generator in its manufacture and use, and the period of use of x-ray tubes. (56) USSR Author's certificate N 599738, CL N 05 G 1/02, 1978.

USSR author's certificate N 1526555, CL N 05 G 1/02, 1988.

COMPACT X-ray GENERATOR, comprising a housing that houses the x-ray tube and sectional diode-capacitor voltage multiplier, made by the scheme Macroplan in the form of two diametrically arranged raising and leveling columns, each section of which has a single point of doubling the voltage, as well as screening tools, in the form of metal rings mounted coaxially x-ray tube, each ring is electrically connected with the point of voltage doubling opposite him partitions voltage multiplier, wherein at least one n-e, metal ring provided with a first and second sector of the metallic elements, the voltage multiplier circuit is further provided with first and second controllable voltage dividers, each having one managed element and one middle point, and first and second control means, while the first and the second sector of the metallic elements of the n-th metal rings made of electrically isolated from each other and from the ring and posted on the 90ofirst conclusions controllable voltage dividers are electrically connected with the point of voltage doubling (n - 1)-th section of the voltage multiplier, the second conclusions controllable voltage dividers are electrically connected with the point of voltage doubling (n + 1)-th section of the voltage multiplier, the midpoint of the first controlled voltage divider electrically tie what about the voltage divider electrically connected with the second sector of a metallic element of the n-th metal rings, the first and second controls the contactless related to the driven element, respectively, the first and second voltage divider.

 

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