JPS597200B2 - charged particle accelerator - Google Patents

Description

[Detailed description of the invention] The present invention relates to a charged particle accelerator.

As is well known, in this type of accelerator, it is sometimes required to change the acceleration energy of charged particles, and to do this, the high voltage applied for acceleration is changed.

However, if the high voltage is simply changed, the amount of particles emitted from the filament changes at the same time as the acceleration energy, and the focal length also changes, changing the particle trajectory.

For this reason, in the past, a constant voltage device was installed in the high potential part, and the constant voltage obtained by this device was applied to the accelerating electrode of the accelerating tube, etc., to feed the accelerating electrode, but this caused the following problems. There is a point.

In other words, ■ Requires a constant voltage device and its power source.

@ It is difficult to feed electricity from a constant voltage device, etc. installed in a high potential area to an accelerating electrode, etc.

It is.

On the other hand, as shown in FIG. 1, it has been considered to provide a constant voltage element 1 between the accelerating electrodes 3 of the first stage to several stages of the accelerating tube 2 to appropriately adjust the voltage of the accelerating tube 2 to a constant voltage.

In the figure, 4 is a power source, 5 is a filament transformer, and 6 is a filament.

According to this, the above-mentioned problem (■) is solved to a certain extent, but when the applied voltage decreases from the constant voltage region of the constant voltage element 1, the so-called so-called current flows through the resistance for feeding the accelerating electrode 3. The bleeder current stops flowing and the potential of each electrode becomes unstable.

Additionally, an acceleration tube 2 is installed for voltage conditioning purposes.
Even if an overvoltage is applied to the voltage, the overvoltage is not applied to the constant voltage portion, so there is a drawback that conditioning cannot be performed completely.

This invention attempts to solve the above-mentioned problems and drawbacks all at once. Among the accelerating electrodes constituting the accelerating tube, the accelerating electrodes located within the region that determines the focal length of charged particles from the first stage accelerating electrode. The present invention is characterized in that a composite element formed by connecting a constant voltage element and a resistance element in series and a resistance element in parallel is provided between each stage.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 2 and 3. Reference numerals 11a to llf are a plurality of accelerating electrodes constituting the accelerating tube 10, which are formed in a disk shape, with a hole 12 provided in the center. As will be described later, charged particles are accelerated downward through this hole 12.

Each of the acceleration rods 11a to 11f is stacked with an insulating ring 13 interposed therebetween.

14 is a filament, 15 is a focusing cup, 16 is an electrode that supports the focusing cup, 17 is a power supply terminal to which a DC high voltage that is an accelerating voltage is applied, and 18 is the first stage of accelerating electrodes 11a to 11f that constitute the accelerating tube 10. A composite element is provided between each stage of accelerating electrodes in a region that determines the focal length of charged particles from the accelerating electrode, and its specific configuration is as shown in FIG.

That is, this composite element 18 is constructed by connecting a constant pressure element ZD and a resistive element R8 in series, and a resistive element RP connected in parallel.

Reference numeral 19 denotes a voltage dividing resistor connected in series with the composite element 18 and connected in parallel between each stage of the accelerating electrodes other than those mentioned above constituting the accelerating tube 10.

The upper end of a series-connected circuit consisting of a plurality of composite elements 18 and the voltage dividing resistor 19 is connected to the power supply terminal 17, and the lower end is connected to ground.

The electrical values of the composite element 18 during rated operation are as shown in FIG.

In other words, tFiI flows through E1 through the voltage applied to the crotch.
When is 1, the voltage shared by the resistance element R8 connected in series with the constant voltage element zD is 0.03E to 0.3E, and the current shunted to the other resistance element R is 0.03I to 0.3■ It is.

In the above configuration, the charged particles extracted from the filament 14 by the first-stage accelerating electrode 11aVc are accelerated by the potential of each accelerating electrode and move downward.

Therefore, in the illustrated configuration, when the DC high voltage applied to the power supply terminal 17K is changed to change the acceleration energy, the potential of the final stage accelerating electrode 11f with respect to the first stage accelerating voltage 11a is changed. Also, the potential of each accelerating electrode from the first stage to the third stage accelerating electrodes 11a to 11c is not changed at all by the presence of the constant voltage element ZD constituting the composite element 18.

Even if the interstage voltage E in these accelerating lightning poles 11a to 11c becomes small, the bleeder Hit will not become zero because there is a resistive element Rp in parallel with the constant voltage element zD.

Therefore, each accelerating electrode is fed with some potential, and potential instability caused by the absence of bleeder current is eliminated.

Furthermore, when the current I is increased, the interstage lightning pressure E becomes a dog because there is a resistive element R8 in series with the constant voltage element ZD.
Therefore, the voltage applied to the accelerating electrode increases, creating an overvoltage.

This overvoltage allows conditioning.

Here, the voltage region in which the composite element 18 is provided may be a region including the accelerating electrode that determines the focal length as described above, and specifically, a voltage range of 1/5 to 1/'2 of the maximum accelerating voltage. It is better to make it an area.

As detailed above, according to the present invention, even if the voltage of the accelerating electrodes from the first stage to multiple stages is changed to change the DC high voltage to change the acceleration energy, the crotch voltage can be maintained at a constant value. Therefore, the amount of particles emitted from the filament does not change, and the optical system does not change at all during this time.

Furthermore, since the composite element is provided, the accelerating electrode is supplied with a certain potential, which prevents the potential from becoming unstable and makes it possible to perform conditioning by overvoltage.

Particularly in high-voltage equipment such as the accelerator, it is important to be able to perform such conditioning in order to operate the equipment safely and stably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional charged particle accelerator, FIG. 2 is a schematic diagram showing one embodiment of the present invention, and FIG. 3 is a block diagram of a composite element. 10...Sukeren tube, 11a-llf...Acceleration electrode, 18...Composite element, zD...
Constant voltage element, R8... Resistance element, shame...
・Resistance element.

Claims (1)

[Claims] 1 Among the multiple accelerating electrodes that make up the accelerating tube, a constant voltage element and a resistance element are connected in series between each stage of the accelerating electrodes in the area that determines the focal length of charged particles from the first accelerating electrode. A charged particle accelerator comprising a composite element formed by connecting a resistive element and a resistive element in parallel.