JPS6297300A - X-ray tube controller - Google Patents

Abstract

PURPOSE:To stop the exposure of X-rays at the time of something trouble and protect an X-ray tube from being damaged, by connecting a vacuum tube, having plural grid, to an interval between a high-voltage power source and the X-ray tube, and installing a protective device which impresses negative voltage to the screen grid. CONSTITUTION:Tetrodes 1 and 2 are connected to an interval between a high- voltage power source and an X-ray tube 3. Constant positive voltage is impressed on both grids 52 and 62 of these tetrodes 1 and 2 by a G2 control circuit 25, while these grids 51 and 61 opens or closes a high-tension circuit in impressing positive or negative voltage to cathodes 50 and 60 by a G1 control circuit 26, controlling the exposure of X-rays. When something trouble occurs in the circuit 26, a trouble current detecting circuit 20 detects this trouble and transmits it to a protective circuit 21. This circuit 21 opens a power switch 8 and a filament circuit switch 31 and simultaneously impresses the negative voltage to these grids 52 and 62 via the circuit 25, intercepting the current. With this constitution, even in case something trouble happens in a grid control circuit, the X-ray tube is protectable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an X-ray tube control device using a high voltage switch used to control an X-ray tube, such as a tetrode tube.

[Technical background of the invention and its problems] XI using a conventional tetrode tube! The second pipe control device
' Shown in Figure. As shown in Fig. 2, the anode side high voltage voltage 8!
40 and the cathode side high voltage power supply 41 are respectively connected to the tetrode tube 1.
, 2 of the X-ray tube 3 through l! A high voltage is supplied to 1t4i4 and the cathode 5. This X-ray tube is of a center metal grounding type, and the center metal 6 is grounded.

The tetrode tube 1.2 is a high voltage switch, and is connected to the grid control device 70 and each grid G151.61, and opens and closes the switch according to an electric signal from the grid control device 70.

In other words, the second grid (screen grid) G2 of the tetrode tube is kept constant at approximately +500V, and the first grid (control grid) G1 is varied from approximately -900V to +1ooV.
This is done by changing the voltage to V to generate a high voltage in the XII tube. If cathode 50.60 is OV, grid G15
1.61, a voltage higher than the cathode 50.60 e.g. +1
When 00V is applied, electrons from the cathode 50.60 are accelerated and a current flows. On the other hand, grid G151゜6
When a voltage lower than that of the cathode 50.60, for example -900v, is applied to the cathode 1, no current flows and xIIa is not irradiated.

The grid control device 70 controls the X-rays from the X-ray tube 3 by simultaneously performing this control. Tetrode tube 1.
2 grid G252°62 has a grid Gl 51.6 so as to absorb the secondary electrons from the anode 53.63.
A higher voltage, for example, +500v, than the on-voltage of 1, for example, +100v, is always applied.

In the above control, if the grid control device malfunctions and grid G1 cannot be controlled,
There is a risk that it will not be possible to stop the exposure of Xl1l.

[Object of the Invention] The present invention was made based on this situation, and an object of the present invention is to provide an X-ray tube 11J control device that protects the XwA tube even if the grid G1 control circuit malfunctions. There is.

[Summary of the invention'g! ] In order to achieve this object, the present invention utilizes a high-voltage power source that generates a high voltage and a high voltage supplied from this high-voltage power source.
a vacuum tube connected between the X-ray tube and the high-voltage power source and having at least a control grid and a screen grid; and a vacuum tube that controls the control grid and switches the high voltage. This Xm tube IIIO device is characterized in that it is provided with a grid control circuit and a protection means for applying a negative voltage lower than the cathode of the vacuum tube to the screen grid when the control grid cannot be controlled.

[Embodiments of the invention] Hereinafter, the present invention will be explained in detail with reference to FIG.

In FIG. 1, for example, an AC power supply 7 that supplies 200V
is connected to the primary side of a high voltage transformer 9 via a power switch 8. On the secondary side of this transformer 9 there are two coils with the same number of turns, connected to each diode bridge 11, 12. These bridges 11, 12 then rectify the high voltage.

Furthermore, one end of a capacitor 13, 14 and a tetrode tube 1.degree. 2 are connected to the output terminals of the bridges 11, 12, respectively. These capacitors 13 and 14 are charged with charges from the bridges 11 and 12 to obtain a smoothed DC high voltage. The obtained DC voltage is applied to the anode 4 of the X-ray tube 3 via the tetrode tubes 1 and 2 and resistors 15 and 16.
is applied to the cathode 5. One end of each of the resistors 15 and 16 is connected to the grounded center metal 6 of the X-ray tube 3.

The other ends are connected to controls 13 and 14, respectively. On the other hand, the cathode 5 of the X-ray tube 3 is heated by applying electric power from the filament circuit power supply 29 via the switch 31 and the filament heating circuit 30, thereby emitting electrons from the cathode.

In such a configuration, the opening/closing control of the tetrode tubes 1 and 2, which are high-pressure switches, is performed separately during a normal state and when an abnormality is detected.

When tetrode tube 1.2 is operating normally,
The G1 control circuit 26 receives the X-ray exposure command signal generated from the X-ray exposure control circuit 23. Upon receiving this signal, the 01 control circuit 26 controls the grid Gl 51, 61 by this signal.
positive voltage (e.g. +
100V) is applied. As a result, each tetrode tube 1゜2 closes almost simultaneously, current flows, and X-ray tube 3
X-rays are emitted from the On the contrary, X-rays are l1rAL
Otherwise, a reverse bias (for example, -900V) is applied from each 01 control circuit 26 to each cathode 50,60. In such a normal state, the grid G
252.62 always has a positive voltage (
For example, +500V) is applied. In this normal state without failure, control is performed by opening and closing the two tetrode tubes 1.2 almost simultaneously. However, if grid Gl 51.61 cannot be controlled due to a failure in the 01 control circuit 26, an abnormal current flows through the X-ray tube 3, so the resistor 1
A voltage different from the normal state is applied to both ends of 5.16.

The abnormal current detection circuit 20 detects X1! It is determined whether a normal current is flowing by comparing the X-ray radiation signal from the radiation control circuit 23 and the voltage across the resistor 15 and 16, and if the comparison does not match, a signal indicating an abnormality is sent. Output. The protection circuit 21 receives this signal, learns of the abnormality, and immediately switches on the power switch 8 and the filament circuit switch 31.
At the same time as opening, the error display circuit 22 is commanded to display an error. A signal is also output to the G2 control circuit 25 to notify that an abnormality has occurred. Upon receiving this signal, the protection circuit 21 becomes aware of the abnormality, immediately opens the power switch 8 and the filament circuit switch 31, and at the same time instructs the error display circuit 22 to display an error. Furthermore, a signal is outputted to the 02 control circuit 25 as well to notify that an abnormality has occurred. When the 02 control circuit 25 receives this signal, it sends each cathode 50 .
A negative voltage (for example, -900V) is applied to the voltage 60. In other words, the state is such that a reverse bias is applied to the tetrode tube 1.2. By doing this, the cathode 50.
The electrons emitted from 60 are repelled by the negative voltage of grid G252.62 and do not reach the anode 53.63. Therefore, the current can be interrupted even if a positive voltage is applied to the grid Gl 51.61.

Note that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications within the scope of the gist thereof.

For example, in the above-mentioned embodiments, examples of i-in-body electric circuits for performing the respective required controls are shown, but these are not limited to the illustrated electric circuits and have similar functions. For example, the necessary control may be performed using software using a computer. In addition, a tetrode tube is used for the high pressure switch to control grid G2, but 4
Similar control may be achieved using other grids using more than one pole. Furthermore, in the example, tetrode tubes were used for both the positive and negative electrodes, but X
Control may be performed using a single tetrode tube.

Effects of the Invention] As described above, according to the present invention, even if the grid G1 itself or the control circuit of the grid G becomes abnormal, the X-ray tube can be protected.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an X-ray tube control device according to the present invention, and FIG. 2 is a block diagram of a conventional X-ray control device. 1.2... Tetrode tube, 3... X-ray tube 20
...Abnormal 'R inflow and outflow circuit 25...G2 control circuit 2
6...01 control circuit

Claims (3)

[Claims] (1) A high voltage power supply that generates high voltage, Due to the high voltage supplied from this high voltage power supply, An X-ray tube that emits X-rays, and a connected between the high voltage power supply and at least Control grid and screen grid A vacuum tube with a pad, control the control grid; Grid system for high voltage switching control circuit and The control grid cannot be controlled. to the screen grid when Apply a negative voltage lower than the cathode of the vacuum tube It is characterized by the provision of protective measures to X-ray tube control device. (2) The X-ray tube control device according to claim 1, wherein the X-ray tube is a center metal grounded X-ray tube. (3) The X-ray protection means applies a negative voltage lower than the cathode of the vacuum tube to the screen grid when an abnormal current flows through the center metal. Pipe control device.