JPS62122038A - Power supply for emitting charged particle beam - Google Patents

Abstract

PURPOSE:To improve the reproducibility of electron emission by starting cathode heating and voltage application simultaneously and making current and voltage attainable to the predetermined set values respectively. CONSTITUTION:An emitting cathode 6, the first anode 7 and the third anode 8 are set in a vacuum envelope 9 and heating current If flows through the emitting cathode from a heating power supply 10. At a time of impressing high voltage from an extracting high voltage power supply 12 on the first anode 7 placed at a position facing the emitting cathode 6, electron 11 are emitted from the tip of the emitting cathode 6 and electrons 14 passing the aperture 13 of the first anode among the emitted electrons are accelerated by an accelerating high voltage power supply 15. In a case of lower accelerating high voltage than extracting high voltage, the electrons 14 passing through the aperture 13 are decelerated. That is, the heating power supply 10 and the extracting high voltage power supply 12 are controlled by a same operating power supply 16. The heating power supply 10 and the extracting high voltage power supply 12 are made so as to output heating current and high voltage respectively in proportion to the output of the operating power supply 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a power supply device for a field emission electron source, and particularly relates to a power supply device suitable for a heated field emission electron source that performs field emission while heating a cathode. .

[Background of the invention]

The conventional device, as described in Japanese Patent Application Laid-Open No. 47-41464, applies four heating currents and a high pressure IS.

They were carried out completely separately, and no consideration was given to the timing relationship between the two.

However, in heating type field emission, it was found that the reproducibility of electron emission deteriorates unless the timing of heating and electric field is adjusted. Here, a metal atom ('ri) is attached to a tungsten needle.
This timing is particularly important for field emission cathodes in the form of diffused + zr).

[Purpose of the invention]

The present invention has been made for the purpose of improving the reproducibility of electron emission by timing the heating of a heated field emission B electron source and the application of an electric field to the same timing.

[Summary of the invention]

The present invention can of course be applied to IT field emission in which electrons are emitted by heating a needle cathode such as tungsten or LaBg and applying a strong field.
It is particularly effective when used for field emission from a cathode in which r (zirconium) or Ti (titanium) is diffused on the surface of an acicular tungsten cathode. In the following explanation, only the electric field radiation that diffuses Ti will be explained.

Figure 1 shows the structure of a tungsten needle B pole for diffusing Ti. Thickness approximately 0, bent into a hairpin shape
．． Single crystal tungsten (thickness 0.12 m, axial direction <i 00>) 2 was spot welded to the center of a 15 m long support tungsten 1 and processed into a needle shape by electropolishing. The radius of curvature of the tip 3 of this needle is approximately 1100n.

1) is a Ti diffused field emission cathode completed by diffusing Ti into the cathode shown in FIG. 1(a).

This Ti is heated to about 1300 t:' by applying electricity to the support tungsten 1. As a result, Ti diffuses to the tip 3 of the needle. At this time, at the tip 3 of the needle,
When i is diffused by one atomic layer through oxygen, electron emission with very good timing is obtained. For more information on these,
It is described in Japanese Patent Application No. 136410/1983.

This situation is schematically shown in FIG. Good electron emission is determined by the balance between the surface tension of Ti, which is determined by the temperature 3 at the tip 3 of the needle, and the strong electric field [F] applied here. At this time, one atomic layer of Ti5 is conveniently formed at the tip. However, in order to stop electron emission, an electric field [
When F] is cut, Ti5 is drawn toward the base of the needle, and Ti disappears at the tip (Fig. 2(b)). After this, even if the electric field CF)t- is applied again, Ti does not diffuse into the tip. In order to return this to the tip as shown in FIG. 2(a), it is necessary to further raise the temperature T'f and to reactivate it by introducing oxygen. Here, the electric field CF'l was turned off first, but if the heating was turned off first, the Ti at the tip
There are problems such as scattering due to electric field.

Therefore, in the present invention, the electric field (1) is lowered and the heating temperature is also lowered at the same time to prevent Ti from retreating as shown in () in FIG.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. A radiation cathode 6, a first anode 7, and a third anode 8 are installed in a vacuum container 9. Only the main elements of the electron gun have been described here. A heating current of Ir flows through the radiation cathode 6 from a heating power source 10 . A first anode 7 is located opposite the radiation pole 6.
is placed, and when a high voltage of 2 to 5 kV is applied from the high voltage power source 12, electrons 11 are emitted from the tip of the radiation cathode 6.

Among the emitted electrons, the electrons 14 that have passed through the aperture 13 of the first anode are accelerated by the acceleration high voltage power supply 15 . When the accelerating high voltage is lower than the extraction height ridge pressure, the electrons 14 passing through the aperture 13 are decelerated.

Conventionally, the heating power supply 10 and the draw-out high voltage power supply 12 were operated separately. It has already been mentioned that there are problems with this conventional method of operation. In this embodiment, the heating power source 10 and the draw-out high voltage power source 12 are connected to the same operating power source 16. The heating power source 10 and the draw-out high voltage power source 12 are made to output heating current and high voltage in proportion to the output of the operating power source 16.

FIG. 4 shows an example of the internal configuration of the operating power source 16.

The pulse oscillator 17 generates a fixed number of pulses (for example, 256) by starting manually or by a command from a computer.
Figure 5 ■). The output of pulse oscillator 17 is input to counter 18 . The counter 18 performs addition of pulses, and its output increases stepwise as shown in FIG. 5, and finally reaches a constant value. The output of the color/liquid 18 is input to a heating current setting circuit 19 and a drawer high voltage setting circuit 20. In both circuits, the input signal is increased/decreased to set the desired heating current,
Can be set to high draw voltage. Furthermore, in both of these circuits, in addition to mirroring the final voltage, it is also possible to increase the voltage not only linearly but also functionally. For example, do it exponentially. Moreover, the rising time can also be set arbitrarily. Typical values are 10 seconds to 30 seconds, which is longer than the thermal time constant of only 6 radiation shadows.

To stop the electron radiation tray, the pulse oscillator 17 oscillates a pulse of opposite polarity, and the counter 18 performs subtraction to return the set value to zero.

〔Effect of the invention〕

By implementing the present invention, it has become possible to use heated field radiation with good reproducibility, which has hitherto had a problem with reproducibility.

[Brief explanation of drawings]

FIG. 1 is a front view of a Ti diffused field emission @ pole. Fig. 2 is a model diagram of the diffusion and retreat of Ti at the cathode tip, Fig. 3 is a schematic diagram of an embodiment of the present invention, and Fig. 4 is a block diagram showing the configuration of the operating circuit. ￥ J5 Figure Time 0 Upper #-11 Imaja

Claims (1)

[Claims] 1. The tip of the cathode is heated by heating a thinly sharpened metal cathode or a cathode obtained by diffusing another type of metal onto a thinly pointed metal needle, and applying a high electric field. A charged particle beam radiation power source for a charged particle beam source that emits more charged particles, characterized in that it is configured to simultaneously start heating the cathode and applying voltage so that a predetermined set current or voltage is reached at the same time. . 2. The charged particle beam radiation power source according to claim 1, wherein the set current or voltage is reached linearly with respect to time.