JPH04105451U - Electron source filament life detection device - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to detect the lifetime of the filament of an electron source with high accuracy. [Structure] An insulating plate having a pair of electrodes facing each other on its surface is arranged near the filament. When the filament is turned on, evaporated matter adheres between the two electrodes and the resistance value between the two electrodes changes. Since the amount of evaporated material is proportional to the life of the filament, the life of the filament can be determined by measuring the resistance value.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention detects the filament life of electron sources used in electron beam irradiation equipment, etc. related to a device for

0002

[Conventional technology]

To detect the lifespan of this type of filament, the voltage and current supplied to the filament are This is said to be possible by managing the filament, but in reality the filament In order to keep the emitted electron dose constant even though the resistance of The filament voltage must be increased, so the filament voltage and current It is extremely difficult to detect its lifespan from its management.

0003 For this reason, in the past, the specified lifespan of the filament was calculated based on past results and calculations. When the cumulative lighting time of the filament reaches this specified life time, the life has expired. We are trying to do the exchange accordingly.

0004 However, in reality, it depends on the usage conditions of the filament, such as degree of vacuum, electron flow value, etc. The actual filament life time and the specified life time determined as above. There is a considerable difference in the lifespan, and as a result, the life of the wire may come to an end and break before the specified life time is reached. Even if the product has been stored away or is still usable, it is assumed that it has reached its specified lifespan. You may end up replacing it.

[0005]

[Problem that the idea aims to solve]

This invention improves the accuracy of predicting filament lifespan. The purpose of this is to optimize the timing of replacing ment.

[0006]

[Means to solve the problem]

The present invention uses a pair of electrodes facing each other near the filament. Install the edge plate and detect the remaining life of the filament from the change in resistance between both electrodes. It is characterized by the following.

[0007]

[Effect]

The resistance value between the electrodes of the insulating plate is initially constant, but when the filament is lit Thermionic electrons are ejected from the heated filament, and the evaporated tungsten Steam from stainless steel, etc. adheres to the insulation board. Therefore, the resistance value between both electrodes is the amount of adhesion It changes accordingly. The amount of evaporation from the filament depends on the lifetime of the filament. It is proportional to life, and the amount of evaporated matter is considered to be constant until the end of life. Therefore, the remaining life of the filament can be detected from the resistance value. It becomes like this.

[0008]

【Example】

FIG. 1 shows a sectional view of an embodiment of the present invention. In the same figure, 1 is the cathode flange , 2 is a filament, 3 is a support rod that supports filament 2, and this is a cassette It passes through the field flange 1 in an airtight manner. 4 is the cathode cup, 5 is the focus cup. It is a top. These configurations are not particularly different from ordinary electron sources.

[0009] According to the present invention, a pair of electrodes facing each other (Fig. In this example, an insulating plate 8 having conductors (6, 7 such as conductive wires) attached to its surface is installed. 9 is a measurement lead connected to the end of each electrode 6, 7, which is also connected to the cathode flare. It passes through the cable 1 in an airtight manner.

0010 The filament 2 and the insulating plate 8 are covered with a cathode cup 4, and the electron extraction A focus cup 5 is placed on the side facing the mouth. Opposing area of both electrodes 6 and 7 In order to make it wider, it is best to bend it as shown in the figure.

[0011] When filament 2 is turned on, evaporated matter from filament 2 flows between both electrodes 6 and 7. By adhering to the electrodes, the resistance value between both electrodes 6 and 7 changes in proportion to the lighting time. do. If the amount of evaporated matter is constant during the life of filament 2, then The remaining life of the filament 2 can be determined from the resistance value. 10 is a measurement circuit that measures the resistance value.

0012

[Effect of the idea]

As explained above, according to the present invention, based on the amount of evaporated matter from the filament, Since the lifespan of the filament is detected using It has the effect of becoming a Noh play.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view of an insulating plate.

[Explanation of symbols]

2 filament 3 Support rod 6 Electrode 7 Electrode 8 Insulating board 10 Measurement circuit

Claims (1)

[Scope of utility model registration request] 1. An electron source in which an insulating plate having a pair of electrodes facing each other is installed near a filament of the electron source, and the life of the filament is detected from the resistance value between the two electrodes. Filament life detection device.