JPH0325845A - Conditioning device of charged particle beam accelerating tube - Google Patents

Abstract

PURPOSE:To prevent roughening of an electrode surface on the lower electric potential side due to the discharge between adjoining electrodes by preferentially applying voltage for conditioning only between specified electrodes, in the same direction as in used. CONSTITUTION:At the time of conditioning, each electrode 1a-1f is connected to a power source 7 for conditioning through a connection switching circuit 6. In the drawing, the conditioning between electrodes 1a and 1b is depicted, in which electrodes 1b-1f are commonly connected together by the connection switching circuit 6. An electric field of the same direction as in use is thus applied between the electrodes 1a and 1b, whereby conditioning is performed. As the voltage is applied between the specified electrodes in the same direction as in the normal use, through the discharge during conditioning, roughening of the electrode surface on the lower electric potential side can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a charged particle beam accelerator tube conditioning device for conditioning an accelerator tube used in a high accelerating voltage electron beam device or ion beam device.

(Prior Art) FIG. 3 shows an acceleration tube used in a focused ion beam device with a high acceleration voltage. The accelerating tube has a large number of accelerating electrodes 1
a to 1f and insulators 2a to 2 arranged between each electrode
It is composed of e. The electrodes 18 to 1f are connected by dividing resistors 3a to 3e, respectively, and a high voltage is applied from the acceleration power source 4 between the first electrode 1a and the last electrode 11f. Voltages divided by dividing resistors 38 to 3e are applied to each electrode, and the ion beam is introduced into the acceleration tube! B is accelerated by each electrode.

Now, when conditioning is performed in such an acceleration tube, as shown in FIG.
are connected to every other electrode, and an AC voltage from an AC power source 5 is applied between adjacent electrodes.

(Problem to be Solved by the Invention) In the above-described conditioning method, as shown in FIG. The presence of the microprotrusions T on the surface causes discharge, which roughens the lower surface of the upper electrode 1a. On the other hand, the sixth
As shown in the figure, the electric field in the opposite direction to that in use is l'fi.
When J is applied, a discharge occurs due to the presence of microprotrusions T on the upper electrode surface due to conditioning.
The upper surface of the lower electrode 1b will become rough. As a result of this conditioning, the surface of the lower electrode 1b, that is, the electrode on the low potential side in normal use, is roughened by electrons, which causes dielectric breakdown when a positive electrostatic potential is applied.

It may be possible to perform conditioning in the same state as in normal use, but in that case, it is necessary to increase the voltage from the acceleration power source 4 in the configuration shown in FIG. 3 so that conditioning can be performed. However, in this connection, if a discharge occurs between certain electrodes, an excessive voltage will be applied to the gap formed by the adjacent electrodes, leading to deterioration of the insulator.

The present invention has been made in view of these points, and its purpose is to prevent the electrode surface on the low potential side from being damaged by discharge during normal use, and to prevent excessive voltage from being applied between specific electrodes. The object of the present invention is to realize a conditioning device for a charged particle beam accelerator tube that can perform conditioning so that the charged particle beam is not damaged.

(Means for Solving the Problems) A conditioning device for a charged particle beam accelerator tube based on the present invention applies a conditioning voltage to one of the many accelerating electrodes adjacent to the charged particle beam accelerating tube. It is characterized in that it is structured so that it can be selectively applied between two matched electrodes.

(Function) When conditioning an accelerator tube, some of the many accelerating electrodes are connected in common, an electric field is applied in the same direction as in normal use only between two specific electrodes, and the electric field is The combination of electrodes to which is applied is switched, and conditioning is performed between each electrode.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a conditioning device according to the invention, in which the same parts as in FIG. 3 are given the same numbers.

In this embodiment, during conditioning, each of the electrodes 1a to 1f is connected to a conditioning power source [7] via a connection switching circuit 6. The state shown in FIG. 1 shows a case where conditioning is performed between electrodes 1a and 1b, and in this case, electrodes 1b to 1f are commonly connected by a connection switching circuit 6. Therefore, electrode 1
An electric field in the same direction as in use is applied between a and lb to perform conditioning.

Next, when conditioning the electrodes 1b and 1c, the connection switching circuit 6 connects the electrodes 1a and 1b in common, as shown in FIG.
are commonly connected. As a result, an electric field in the same direction as in the use state is applied between the electrodes 1b and 1c. Thereafter, similarly, the connection state between the electrodes is switched by the connection switching circuit 6 so that each electrode is selectively conditioned.

In this way, since voltage is applied in the same direction as in normal use only between specific electrodes, the electrode surface on the low potential side is prevented from becoming rough due to discharge during conditioning.

(Effects of the Invention) As explained above, in the present invention, since the conditioning voltage is selectively applied only between specific electrodes in the same direction as in the usage state, the The electrode surface on the potential side is not roughened by discharge, and dielectric breakdown is prevented even if a positive electrostatic potential is applied. Furthermore, since conditioning is performed between individual electrodes in order, it is possible to accurately determine which electrodes are likely to cause discharge.

Furthermore, since all accelerating electrodes are not conditioned at the same time, excessive voltage is prevented from being applied between specific electrodes due to discharge.

[Brief explanation of drawings]

FIGS. 1 and 2 show an acceleration tube conditioning device according to an embodiment of the present invention, FIG. 3 shows an acceleration tube, and FIG. 4 shows a conventional acceleration tube conditioning device. 5 and 6 are diagrams showing the state of discharge due to conditioning. 1a to 1f...Accelerating electrodes 2a to 2e...Insulators 3a to 3e...Dividing resistors

Claims (1)

[Claims] A charged particle beam accelerator tube consisting of a large number of accelerating electrodes is characterized in that a conditioning voltage can be selectively applied between two adjacent electrodes among the large number of accelerating electrodes. Conditioning device for charged particle beam accelerator tube.