JP3504867B2 - Field emission type electron gun - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam apparatus using a field emission type electron gun (hereinafter, referred to as FEG). 2. Description of the Related Art FEGs have a smaller electron source than conventional thermoelectron guns, an extremely narrow energy width of electron beams, and a much higher brightness. By using it for various electron beam devices, its performance can be dramatically improved. FIG. 3 shows an FE of an electron beam apparatus using FEG.
FIG. 3 is a diagram illustrating a schematic configuration example of a G peripheral portion. In the figure, 1 is a high-voltage power supply, 2 is a flashing circuit, 3 is an extraction voltage generation circuit, 4 is an acceleration voltage generation circuit, 5 is a detection display circuit,
Is a detection resistor, 10 is an FEG, 11 is an emitter, 12 is an extraction electrode for extracting electrons from the emitter 11,
Reference numeral 13 denotes an accelerating electrode for accelerating electrons. 21 is
A start / fall control unit that controls the flushing circuit, the extraction voltage generation circuit 3, and the acceleration voltage generation circuit 4 to automatically start and stop the FEG 10;
Reference numeral 0 denotes an operation console that sends a start / fall instruction to the control unit 21. In the device configured as described above, when the start of the FEG 10 is instructed from the console 20, the control unit operates the flashing circuit 2 with the emission of the electron beam from the emitter 11 stopped first. By doing so, the tungsten wire for supporting the emitter is heated, and this heat is transmitted to the emitter 11 by heat conduction to perform flushing. Next, after the flushing, a voltage generated by the extraction voltage generation circuit 3 is applied between the emitter 11 and the extraction electrode 12. The extraction voltage is increased in steps, for example, by 50 V, and is increased to a predetermined extraction voltage. The emitter 11 raises the potential of the extraction electrode 12 so that the emitter 11
A strong electric field acts between the electrode and the extraction electrode 12, and an electron beam is emitted from the emitter. As described above, the electron beam emitted from the emitter 11 has an excellent feature that the energy width is narrow and the brightness is high as described above. In general, there are various methods for monitoring the emission current.
As shown in FIG. 3, a detection resistor R for detecting an emission current is provided between the power source for each electrode and the emitter, and a potential difference between both ends is detected by the detection display circuit 5 as shown in FIG. The display method is widely adopted. [0006] However, the FEG
The emission current at the time of start-up and at the time of stop of the device 10 fluctuates due to the following factors, so that an accurate emission current cannot be displayed. [0007] As shown in FIG. 3, each configuration of the FEG 10 and the high voltage power supply 1 includes an emitter 1 on an accelerating voltage generating circuit 4.
1. The flashing circuit 2, the extraction electrode 12, and the extraction generation circuit 3 are superimposed. The accelerating voltage generating circuit 4 is generally a Cockcroft-Walton circuit widely used, and is a high-voltage power supply having a voltage of several hundred KV and a high-impedance output. The output of the acceleration voltage generating circuit 4 having such a configuration has a relatively large capacitance between the output and the ground (casing). FE
When the G10 is started and stopped, the extraction voltage that changes stepwise has a stepped voltage waveform including a pulsating flow (AC) due to the effect of the output capacity of the acceleration voltage generation circuit 5. As a result, the emission current fluctuates under the influence of the extraction voltage including the pulsating flow, so that even if this is displayed, an accurate current value cannot be shown. The present invention has been made to solve the above-mentioned problem, and does not always monitor the emission current as in the related art, but shows an accurate value and monitors the emission current only when necessary. The FEG with the above is provided. In order to achieve the above object, the present invention provides a field emission emitter, an extraction electrode arranged to face the emitter, and an extraction electrode between the emitter and the extraction electrode. An extraction power supply for applying a voltage, an acceleration electrode for accelerating electrons passing through the extraction electrode, an acceleration power supply for applying an acceleration voltage between the emitter and the acceleration electrode, and a pre-stored power supply. A field emission type electron gun comprising: automatic startup control means for controlling the extraction power supply according to a schedule to perform automatic startup; and means for detecting and displaying an emission current radiated from the emitter. Based on a signal indicating that the automatic startup by the control means has been completed,
A display of the emission current by the emission current display means is started. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a peripheral portion of an FEG to which the present invention is applied. 1, the same reference numerals as those in the explanatory diagram of FIG. 3 denote the same components. In the configuration shown in FIG. 1, reference numeral 20 denotes a console, 21 denotes a control unit, 22 denotes a switch drive circuit, and 23 denotes a switch.
The control unit 21 has a memory (not shown) configured internally by a computer or the like, and stores a startup sequence of the FEG 10. FIG. 2 shows a basic operation flow from startup to termination as a sequence of the FEG 10 of the present invention. The operation console 8 is an operation unit for controlling the FEG 10 and includes a keyboard and the like (including dedicated knobs, button switches, and the like). Each circuit (2,3,2
2) is controlled by the control unit 21 in accordance with the basic operation flow shown in FIG. The switch drive circuit 22 includes the control unit 2
When the display signal indicating the monitoring of the emission current is received from 1, the switch 24 is opened as shown by the solid line in the figure, and when the stop signal indicating that the monitoring of the emission current is released is received, The switch 24 is closed as indicated by the dashed line. The operation of such a configuration will now be described. In the embodiment shown in FIG. 1, the FEG 10 is activated by flushing and then stepping up the extraction voltage to a predetermined voltage, as in the conventional activation procedure. Now, the operation console 20 is operated by the operator.
When the start signal of the FEG 10 is input to the control unit 21 through the control unit (S1), the control unit 21 starts control according to the basic operation flow shown in FIG. 2 according to the input start signal. First, the control unit 21 to which the start signal has been input activates the flushing circuit 2 to apply a predetermined current to the tungsten wire of the emitter 11 to heat the tungsten wire. (S2). Next, after the flushing is completed, the control unit 2
1 controls the extraction voltage between the emitter 11 and the extraction electrode 12 by the extraction voltage generation circuit 3. This extraction voltage is controlled in a step shape of about 50 V, and is increased to a predetermined extraction voltage (S3). Emitter 11
Rises in the emitter 1 due to the rise in the potential of the extraction electrode.
A strong electric field acts between the electrode 1 and the extraction electrode 12, a predetermined emission current is obtained, and the startup of the FEG 10 is completed (S4). As described above, the emission current at the time of startup varies due to the adverse effect of the step-up of the extraction voltage. Therefore, the control unit 21
The switch 24 is kept short-circuited (broken line) during the period from the start to the completion of the start-up, as a period during which the emission current does not need to be displayed. After the start-up of the FEG 10, during the operation of the apparatus (S5), the stability of the emission current value is monitored or the emission current value may be changed depending on the observation purpose. It is common to use them. Therefore, after the start-up of FEG10 is completed,
In order to display the emission current, this is realized by inputting an emission current display signal from the control unit 21 to the switch drive circuit 22 and switching the switch 24 from short circuit (dashed line) to open (solid line). (So) In order to terminate the FEG 10 after using the device, the operator sends a stop signal of the FEG 10 via the console 20 to the control unit 2.
1 is input (S6). The control unit 21 that has received the stop signal
Sends a stop signal to the extraction voltage generation circuit 3 and the switch drive circuit 22. Extraction voltage generation circuit 3 that has received a signal
Performs control so as to reduce the extraction voltage to 0 V (S7), and terminates the FEG 10 (S8). On the other hand, the switch drive circuit 22 that has received the stop signal
Switch from open (solid line) to short circuit (dashed line). Thus, the emission current is not displayed due to the short circuit of the detection resistor R. The emission current after the stop operation of the FEG 10 decreases the extracted voltage in steps of 0.
Until V, the emission current fluctuates in the same manner as when the FEG 10 starts up, and the period during which the emission current needs to be displayed because the FEG 10 is stopped. In the present invention, the display of the emission current is accurate and is displayed only for a necessary period. That is, the display of the emission current is shown in FIG.
From the completion of start-up until the stop signal of the FEG 10 is generated. Except for this period, the display of the emission current is not accurate and is not required. Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, although the description has been given of the cold cathode type (cold type) as the FEG, the heat emission type (thermal type) FEG is described.
May be similarly implemented. As a method of detecting the emission current, a current flowing into the extraction electrode, an electrode dedicated to the emission current, or the like may be used in addition to the present embodiment. Furthermore, as a method of displaying the emission current,
In addition to this embodiment, the operation of the display unit (for example, a meter and a digital meter) of the detection display circuit may be controlled by turning on and off. As described above, according to the present invention, the extraction voltage applied to the emitter and the extraction electrode is changed stepwise according to a predetermined schedule, so that the FEG is automatically activated and automatically activated. In the FEG that is stopped, the emission current is not displayed because the emission current varies when the FEG is automatically started and when the FEG is automatically stopped. As a result, it is possible to display an accurate value and to display the emission current only when necessary, instead of constantly monitoring the emission current as in the prior art. [0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration diagram of one embodiment of a field emission type electron gun of the present invention. FIG. 2 is a diagram showing a basic operation flow of the field emission electron gun of the present invention. FIG. 3 is a diagram showing a configuration diagram of one embodiment of a conventional field emission electron gun. [Description of Symbols] 1 ... High voltage power supply, 2 ... Flashing circuit, 3 ... Extraction voltage generation circuit, 4 ... Acceleration voltage generation circuit, 5 ... Detection display circuit, R ... Detection resistance, 10 ... FEG, 11 ... Emitter, 1
2 ... extraction electrode, 13 ... acceleration electrode, 20 ... console, 2
DESCRIPTION OF SYMBOLS 1 ... Control part, 22 ... Switch drive circuit, 23 ... Switch

Claims (1)

(57) Claims 1. A field emission emitter, an extraction electrode arranged opposite to the emitter, and an extraction power supply for applying an extraction voltage between the emitter and the extraction electrode. An acceleration electrode for accelerating electrons passing through the extraction electrode; an acceleration power supply for applying an acceleration voltage between the emitter and the acceleration electrode; and controlling the extraction power supply according to a previously stored schedule. In the field emission type electron gun provided with automatic start-up control means for performing automatic start-up, and means for detecting and displaying emission current radiated from the emitter, the automatic start-up by the automatic start-up control means is completed. Based on the signal indicating that
A field emission type electron gun characterized in that display of emission current by said emission current display means is started.