JP4140464B2 - Electron beam irradiation apparatus and electron beam emission tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam irradiation apparatus that performs a curing treatment of ink or resin, a crosslinking reaction of a film or rubber, a sterilization treatment, a smoke removal treatment, etc. by irradiating a workpiece with a high energy electron beam. relates to that electron-emitting tube be used therewith.
[0002]
[Prior art]
In general, an electron beam irradiation apparatus is provided with an irradiation head serving as an anode in which an electron beam irradiation window is formed on one end side of a sealed tube (body) having a high vacuum inside, and a hot cathode for generating an electron beam and Using an electron beam emission tube in which one or more grids are arranged in the body, the hot electrons generated by heating the hot cathode are extracted by the grid, and an acceleration voltage of 30 to 100 kV is applied between the grid and the anode. Thus, electrons are accelerated to a high speed, and an object is irradiated with an electron beam from an irradiation window.
[0003]
In this case, in order to make the processing quality of the electron beam irradiation processing constant, it is important to control the amount of electrons to be irradiated constant. Therefore, the beam flowing between the hot cathode and the anode by adjusting the grid voltage. The current is kept constant.
[0004]
Also, the heating power supplied to the hot cathode is usually set at the time of manufacturing the device so that sufficient electrons can be supplied even if the hot cathode's electron emission capability changes due to changes in the hot cathode over time or other factors. A large amount of power is available.
[0005]
However, if sufficient power is supplied as the heating power, the burden on the hot cathode is increased, and the life of the hot cathode is shortened accordingly.
In an electron beam generator used in an image display device having the same problem, a hot cathode (wire) is used in response to a change in grid current (absorbed electron current) at the grid (beam extraction electrode) to solve this problem. A technique for reducing the burden on the hot cathode and extending the life by controlling the heating power to the cathode) has been proposed (see Patent Document 1).
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-31345
[Problems to be solved by the invention]
However, as described above, even if the grid current is monitored and the heating power to the hot cathode is controlled, the grid current depends on the grid voltage, so that the beam current, that is, the electron beam irradiation intensity can be kept constant. Can not.
[0008]
In this case, if the grid voltage is kept constant, the grid current is approximately proportional to the beam current. Therefore, theoretically, the beam current can be kept constant by controlling the heating power according to the grid current. It is possible to maintain.
[0009]
However, in reality, the response speed of the grid current (beam current) to the change in the heating power is extremely slow. Therefore, if the heating power is controlled so that the grid current is maintained constant, the grid increases as the heating power increases. When the current (beam current) reaches the set value, the heating power is excessive.
Therefore, as time elapses, the grid current (beam current) exceeds the set value and overshoots, and if the heating power is reduced accordingly, there is a problem that undershoot occurs and control becomes impossible.
[0010]
Further, since the electron beam emission tube has a very large potential difference (acceleration voltage) between the anode and the grid of 30 to 100 kV, even if the grid voltage is reduced to 0 in order to temporarily stop the electron beam irradiation, The thermoelectrons generated at the cathode are affected by the electric field due to the acceleration voltage, and leak to the anode to generate a leakage beam current.
If this leakage beam current exceeds 5% of the beam current when the grid voltage is maximized, there is a concern about an adverse effect due to leakage of the electron beam.
[0011]
Furthermore, the irradiation intensity of the electron beam irradiated from the electron beam emission tube is normally strongest on the irradiation axis line connecting the center of the irradiation window from the hot cathode, and has a distribution that gradually decreases as the distance from the irradiation axis increases. However, in order to perform uniform processing over the entire irradiation area, the irradiation intensity distribution of the electron beam is required to be as uniform as possible.
[0012]
For this reason, conventionally, a shielding member in which a through hole with a small aperture ratio is drilled in the central portion where the electron beam irradiation intensity is high and a through hole with a large aperture ratio is drilled around the support frame of the electron beam irradiation window. An arranged electron beam irradiation apparatus has been proposed (see Patent Document 2).
[0013]
[Patent Document 2]
JP-A-9-166700 [0014]
However, if the aperture ratio at the central part of the electron beam irradiation window is reduced, electrons that cannot be transmitted collide with the support frame of the irradiation window and are wasted. The energy loss at this time is a product of the amount of electrons (current) that cannot be transmitted and the acceleration voltage, and even a slight loss of the amount of electrons has a high voltage value of the acceleration voltage, and is usually several tens to several tens of watts.
[0015]
In view of this, the present invention firstly enables the beam current to be stably controlled and kept constant while keeping the heating power as low as possible, and secondly, the leakage beam current when the grid voltage is set to 0 is substantially reduced. Third, the technical problem is to be able to control the irradiation intensity distribution of the electron beam with a small energy loss.
[0016]
[Means for Solving the Problems]
In order to solve this problem, the present invention provides an electron beam emission tube in which an irradiation head serving as an anode formed with an electron beam irradiation window is provided on one end side of a body portion, and supplies power to the electron beam emission tube. In an electron beam irradiation apparatus connected to an electron beam controller, a hot cathode for generating an electron beam and one or more grids are shields having a substantially circular or substantially polygonal cross section arranged in the body of the electron beam emitting tube Provided in the pipe,
L ≧ 0.18D × lnV _A
L: Distance from the tip of the shield tube to the tip of the hot cathode (mm)
D: Inscribed circle diameter of shield tube (mm)
V _A : acceleration voltage (kV)
The position of the hot cathode, the size of the shield tube, and the accelerating voltage are selected so as to satisfy the relationship, and according to the irradiation intensity distribution of the electron beam to be irradiated from the irradiation window to at least one of the grids A grid voltage adjusting unit that adjusts the grid voltage so that a beam current flowing between the hot cathode and the anode is maintained constant, and a plurality of through holes are formed with a designed aperture ratio distribution. A heating power adjustment means is provided for detecting the electron emission capability of the hot cathode and increasing the heating power supplied to the hot cathode by a preset value when it is determined that the electron emission capability has reached the lower limit. Features.
[0017]
According to the present invention, the electron beam is irradiated by adjusting the grid voltage so that the beam current is maintained constant by the electron beam controller.
Moreover, although the change in which the hot cathode is deteriorated and the electron emission capacity is lowered is long-term, it is surely lowered according to the usage time of the electron beam emission tube. In this case, control is performed to increase the grid voltage so that the beam current does not decrease with a decrease in the electron emission capability. Therefore, the voltage value of the grid voltage is an index indicating the electron emission capability.
[0018]
Therefore, when the grid voltage reaches a preset upper limit value, it is determined that the electron emission capability has reached the lower limit, and the heating power supplied to the hot cathode is increased by a preset value.
At this time, since the response speed of the beam current to the change in the heating power is extremely slow, the beam current does not increase immediately but gradually increases. When the beam current becomes higher than the set value, the beam current can be kept constant by lowering the grid voltage.
[0019]
In this way, when the electron emission capacity reaches the lower limit due to deterioration of the hot cathode, etc., the heating power is gradually increased, and when the beam current fluctuates, the grid voltage is adjusted to maintain the beam current constant. As a result, the heating power is kept as low as possible, the life of the hot cathode and thus the electron beam emission tube is extended, and the beam current is also stably controlled.
[0020]
Further, when the grid voltage is reduced to 0 in order to temporarily stop the electron beam irradiation, there is no practical problem if the leakage beam current is 5% or less of the beam current when the grid voltage is maximized. .
And according to the inventors' experiment, the hot cathode and one or more grids are provided in a shield tube having a substantially circular or substantially regular polygonal cross section disposed in the body of the electron beam emission tube,
L: Distance from the tip of the shield tube to the tip of the hot cathode (mm)
D: Inscribed circle diameter of shield tube (mm)
V _A : acceleration voltage (kV)
And when
L ≧ 0.18D × lnV _A
It was found that the position of the hot cathode, the size of the shield tube, and the acceleration voltage should be selected so as to satisfy the above relationship.
In the electron beam emission tube, the acceleration voltage is preset as the rated voltage. Therefore, the distance L from the tip of the shield tube to the tip of the hot cathode, and the inscribed circle of the shield tube are usually set against the acceleration voltage. The diameter D may be determined, whereby the beam current is reliably controlled by adjusting the grid voltage.
[0021]
Furthermore, if the aperture ratio distribution of a large number of through holes formed in the grid of the electron beam emission tube is uniform, the irradiation intensity of the electron beam is high at the central portion, and the irradiation intensity gradually decreases as the distance from the central portion increases. Output in intensity distribution.
At this time, only electrons that have passed through the through holes of the grid reach the anode, and electrons that have directly collided with the grid become currents that flow into the grid without passing through the through holes.
Therefore, for example, if the aperture ratio of the through hole in the vicinity of the center is small and the aperture ratio of the surrounding through holes is designed to be large, the irradiation intensity at the center portion is reduced, so that the substantially uniform flat irradiation intensity distribution as a whole The electron beam is output.
[0022]
At this time, the electrons colliding with the grid become a grid current and cause an energy loss. In this case, the energy loss is obtained by grid voltage × current. Since the grid voltage is significantly smaller than the acceleration voltage and is several hundred V at most, the energy loss due to the reduction of the grid aperture ratio in the central part is normally suppressed to several tens of mW.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram showing an electron beam irradiation apparatus according to the present invention, FIG. 2 is a graph showing measurement results, FIG. 3 is a graph showing a profile of irradiation intensity distribution of electron beams, and FIG. FIG. 5 is an explanatory diagram showing an embodiment, FIG. 5 is a flowchart showing a processing procedure of the electron beam controller, and FIG. 6 is an explanatory diagram showing another embodiment.
In this embodiment, the electron beam emission tube has a sealed shape without an evacuation system. However, the electron beam emission tube is used while evacuating the electron beam emission tube with a separate exhaust device and keeping the inside of the tube at a high vacuum. The effect is the same even with a tube.
[0024]
In an electron beam irradiation apparatus 1 shown in FIG. 1, an electron beam emission tube 2 that irradiates an electron beam is connected to an electron beam controller 3 that maintains the irradiation intensity constant.
The electron beam emission tube 2 is provided with an irradiation head 7 serving as an anode 6 on which an electron beam irradiation window 5 is formed on one end side of a sealing tube (body portion) 4, and an electron beam directed toward the irradiation window 5 in the inside thereof. The hot cathode 8 and the grid 9 are provided, and the hot cathode 8 and the grid 9 are provided in a shield tube 10 having a substantially circular or substantially regular polygonal cross section disposed in the sealing tube 4.
Then, the anode 6 is connected to the ground, the acceleration voltage _{V A} of -30~100kV between anode 6 grid 9 is applied by electron beam controller 3, dozens V grid voltage to the grid 9 hot cathode 8 V _G is applied.
[0025]
The irradiation head 7 is made of SUS, and when irradiated with an electron beam, the dose equivalent rate of secondary X-rays emitted to the outside of the electron beam emission tube 2 is 0.6 μSv / hr (October 23, 2000). (See Science and Technology Agency Notification No. 5, Article 2) The thickness is selected to be as follows.
In this example, when the head thickness is 10 mm or more even at the minimum part, the secondary voltage when operating with the acceleration voltage V _A = 60 kV and the beam current I _B flowing between the hot cathode 8 and the anode 6 = 1 mA is used. The dose equivalent rate of X-rays was 0.5 μSv / hr.
[0026]
Further, in order to ensure control of the beam current I _B in the regulation of the grid voltage V _G, a result of the inventors has repeated experiments and research, the leaking beam current when set to the grid voltage V _{G =} 0, 5% to become such a design condition of the electron beam emitting tube 2 of the beam current when the maximum grid voltage V _G was found.
[0027]
Experiments, first, in advance by supplying heating power W _K as a maximum beam current Maxi B ₌ 1 mA flowing between the hot cathode 8- anode 6 while the maximum grid voltage V _G to the hot cathode 8, then, The grid voltage V _G is decreased to 0, and the inscribed circle diameter (the inner diameter when the cross section is circular) D, the distance L from the tip of the shield tube 10 to the tip of the hot cathode 8 and the acceleration voltage V _A are changed. when the beam current I _B was measured leakage limit acceleration voltage V _M which is 5% of the maximum beam current Maxi _B.
[0028]
Figure 2 represents the measurement result, the vertical axis distance L (mm), was expressed in graph plotting the logarithmic axis of the leakage limit acceleration voltage V _M to the horizontal axis, the inscribed circle diameter D of the shield tube 10 Is constant, the distance L and the logarithmic value lnV _M (kV) of the leakage limit acceleration voltage have a linear relationship, and the slope thereof depends on the inscribed circle diameter D (mm) .
Furthermore, in this case, increasing the number of grids 9 did not affect the leakage current value.
[0029]
And it was analyzing this, the distance L and the inscribed circle diameter D, against leakage limit acceleration voltage V _M,
L = 0.18D × lnV _M
And the acceleration voltage V _A needs to be smaller than the leakage limit acceleration voltage V _M.
L ≧ 0.18D × lnV _A
Designed with the conditions of
And, thereby, the leakage beam current was suppressed to less than 5% of the beam current I _B when the maximum grid voltage V _G.
Incidentally, hot cathode 8 because it is disposed in the shield tube 10, the distance L is shorter than the length L _S of the shield tube 10, it holds the relationship of L <L _S.
[0030]
The grid 9 is formed with a large number of through holes 11 having an aperture ratio distribution designed in accordance with the irradiation intensity distribution of the electron beam to be irradiated from the irradiation window 5.
The grid 9 is based on, for example, a reference irradiation intensity distribution of an electron beam transmitted through a grid in which a through hole having a uniform aperture ratio distribution is formed and a target irradiation intensity distribution of an electron beam to be irradiated from an irradiation window. Designed on the basis of the difference in irradiation intensity distribution at the corresponding position.
[0031]
FIG. 3A is a beam profile showing an intensity distribution when an electron beam is cut in the diameter direction of the irradiation spot, where profile A is a reference irradiation intensity distribution and profile B is a target irradiation intensity distribution.
Then, when the electron beam is to be irradiated to the object to be processed with a flat irradiation intensity distribution as shown in profile B, the reference irradiation intensity distribution of profile A is subtracted from the target irradiation intensity distribution of profile B, and FIG. As shown in (b), the difference in irradiation intensity distribution at the corresponding position is obtained, and when the difference is negative, the aperture ratio is reduced according to the absolute value, and when the difference is positive, the aperture ratio is increased according to the absolute value. As a result, an irradiation intensity distribution such as profile B was obtained.
[0032]
At this time, generated in the hot cathode 8, and impinge on the grid 9 is attracted by the grid voltage electron is caused energy loss become grid current I _G, the energy loss in this case is determined by the grid voltage × current .
Since the grid voltage V _G is much smaller than the acceleration voltage V _A and is several hundreds V at most, even if the loss current due to the grid voltage 150 V and the aperture ratio being reduced is 0.5 mA, the loss is 0.5. Only 075 W, and the irradiation intensity distribution of the electron beam can be controlled with a small energy loss.
[0033]
The number of the beam profile shaping grids 9 is arbitrary as long as at least one grid profile shaping grid 9 is provided. Also, as shown in FIG. 4, one or more beam profile shaping grids 9 and a substantially uniform aperture ratio are provided. One or more grids 13 in which a large number of distributed through holes 12 are formed may be used in an overlapping manner.
In short, at least one of the plurality of grids may be the beam profile shaping grid 9.
[0034]
When the plurality of grids 9... 13 are used in an overlapping manner, the total opening area of the through holes 11 and 12 of the grids 9... 13 is gradually increased from the hot cathode 8 side toward the anode 6 side. When formed in such a manner, the electron beam irradiation efficiency is excellent.
[0035]
Electron beam controller 3, the grid voltage adjusting means 21 for adjusting the grid voltage V _G to maintain the beam current I _B flowing between the hot cathode 8 anode 6 constant, to detect the electron emission capability of the hot cathode 8 The heating power adjustment for increasing the heating power W _K (= filament voltage V _K × filament current I _K ) supplied to the hot cathode 8 when it is determined that the electron emission capacity has reached the lower limit. Means 22 are provided.
[0036]
And, thereby suppressing the heating power W _K supplied to the hot cathode 8 as low as possible, and, while maintaining the beam current I _B constant flowing between the hot cathode 8 anode 6, the electron beam emission tube 2 An electron beam can be irradiated.
[0037]
The grid voltage regulator 21, an ammeter 23 to monitor the beam current I _B is connected, the feedback detection signal beam current I _B in response to the adjust the grid voltage V _G to be maintained at a constant value Take control.
Further, the heating power adjusting means 22, the grid voltage regulating means 21 to monitor the voltmeter 24 as an index of the electron emission capability of the grid voltage V _G of the hot cathode 8 output from the connected grid voltage V _G is preliminarily electron emission capability are made to determine that has reached the lower limit when it reaches a set upper limit value MAXV _G.
[0038]
FIG. 5 is a flowchart showing the processing procedure of the electron beam controller 3. Note that the electronic controller 3 includes an initial heating power DW _K , an acceleration voltage V _A , an initial grid voltage DV _{G at} which a target beam current TI _B is obtained, and a maximum grid voltage maxV corresponding to the lower limit of the electron emission capability of the hot cathode 8. _G is set at the time of factory shipment.
[0039]
Then, when the switch (not shown) is turned on and the processing is started, first, in step STP1, the heating power W _K = DW _K and the grid voltage V _G = DV _G are set, and in step STP2, the hot cathode is set. supplying heating power W _K to 8, applying a respective grid voltage V _G and the acceleration voltage V _a across between the grid 9 hot cathode 8 and anode 6 grid 9.
[0040]
Then, the process proceeds to step STP3, whether the beam current _{I B} is equal to the target beam current TI _B judged by the difference ΔI _B = _{I B} -TI _B.
If the difference ΔI _B = 0, it is determined that the grid voltage V _G and the heating power W _K are appropriate, and the process returns to step STP2.
In the case of the difference [Delta] I _B> 0, the process proceeds to step STP4 to reduce the beam current _{I B,} in the case of a difference [Delta] I _B <0 proceeds to step STP6 to raise the beam coulometric _{I B.}
[0041]
In step STP4 and step STP5, it lowers the grid voltage _{V G} until the difference ΔI _B = 0, at the time point when the difference [Delta] I _B = 0 returns to step STP2.
[0042]
Up On the other hand, in step STP6 and step STP7, which increase the grid voltage _{V G} until the difference [Delta] I _B = 0, the process proceeds to STP8 when it becomes the difference [Delta] I _B = 0, grid voltage _{V G} is set in advance whether reaches the grid voltage MAXV _G is determined.
Then, when the grid voltage V _G = maxV _G is reached, it is determined that the electron emission capability of the hot cathode 8 has reached the lower limit, and the process proceeds to STP 9 where the heating power W _K = W _K + ΔW is set in advance. The heating power is increased by the power value ΔW, and the process returns to step STP2.
[0043]
Here, the processes of steps STP4 and S5 and steps STP6 and 7 are the processes in the grid voltage adjusting means 21, and the processes of steps STP8 and 9 are the processes in the heating power adjusting means 22.
[0044]
The above is an example of the present invention, and its operation will be described next.
First, when the electron beam controller 3 is turned on, is adjusted grid voltage V _G so that the beam current I _B is kept constant, the electron beam is irradiated from the electron beam emission tube 2.
[0045]
On the other hand, although the change in which the hot cathode 8 is deteriorated and the electron emission capability is lowered is long-term, it is surely changed according to the usage time of the electron beam emission tube 2. In this case, as the beam current I _B due to the decrease of the electron emission capability does not decrease, since the control for increasing the grid voltage V _G contrast, the voltage value of the grid voltage V _G is the current of the electron emission capability It becomes the index which shows.
[0046]
Therefore, it is determined that the electron emission capability has reached the lower limit when the grid voltage V _G = the upper limit value maxV _G , and the heating power W _K supplied to the hot cathode 8 is increased by a preset value.
Since the response speed of the beam current I _B to the change in the heating power W _K is slow, the beam current I _B does not increase immediately but gradually increases. Therefore, when the beam current I _B increases, It can maintain the beam current I _B constant by lowering the voltage V _G.
[0047]
In this way, by increasing the heating power W _K little by little when the electron emission capability reaches the lower limit due to deterioration of the hot cathode 8 and the like, by adjusting the grid voltage V _G when the beam current I _B fluctuates. Since the beam current I _B is kept constant, the heating power W _K is kept as low as possible, the life of the hot cathode 8 and thus the electron beam emission tube 2 is extended, and the control of the beam current I _B is stable. To be done.
[0048]
The electron beam emission tube 2 is
L ≧ 0.18D × lnV _A
L: Distance from the tip of the shield tube to the tip of the hot cathode (mm)
D: Inscribed circle diameter of shield tube (mm)
V _A : acceleration voltage (kV)
The position of the hot cathode 8 with respect to the acceleration voltage _VA and the size of the shield tube 10 are selected so as to satisfy the above relationship.
Accordingly, the leakage beam current is suppressed to less than 5% of the beam current I _B when the maximum grid voltage V _G, trying to stop temporarily the electron beam irradiation by squeezing the grid voltage V _G There is no problem in practical use.
[0049]
Further, a large number of through holes 11 are formed in the grid 9 of the electron beam emitting tube 2, and only electrons that have passed through the through holes 11 reach the anode 6, and electrons that directly collide with the grid 9 pass through the through holes 11. The current flows into the grid 9 without passing through.
Therefore, for example, if the aperture ratio of the through holes 11 in the vicinity of the center is designed to be small and the aperture ratio of the surrounding through holes 11 to be designed to be large, the irradiation intensity at the center portion is lowered, and the substantially uniform flat as a whole. An electron beam with an irradiation intensity distribution is output.
[0050]
At this time, electrons colliding directly to the grid 9, increases the grid current I _G is a current I _GL flowing into the grid, the energy loss in this case is obtained by the grid voltage V _G × current I _GL, grid voltage Since V _G is remarkably small compared with the acceleration voltage V _A and is several hundred V at most, even if 0.5 mA of the grid current I _G detected when the grid voltage V _G = 150 V is lost, The loss is only 75 mW, and there is little energy loss for controlling the irradiation intensity distribution of the electron beam.
[0051]
In the above description, a case has been described in which to monitor the grid voltage V _G as an electron emission capability of the hot cathode, as shown in FIG. 6, the provided separately detecting electrodes 14 in the vicinity of the hot cathode 8, a hot cathode A predetermined potential difference is given to 8 and the current value flowing into the detection electrode 14 is monitored as the electron emission capability of the hot cathode, and the electron emission capability when the current value falls to a preset lower limit value. May be determined to have reached the lower limit.
[0052]
Moreover, the irradiation intensity distribution of the electron beam is not limited to a flat shape, and the distribution pattern thereof is arbitrary, such as sharpening more sharply or forming a plurality of peaks.
[0053]
【The invention's effect】
As described above, according to the present invention, the beam current is maintained constant by adjusting the grid voltage even when the electron emission capability of the hot cathode decreases and the beam current fluctuates. However, since the heating power is increased little by little, the beam current can be controlled stably, and at the same time, the heating power can be kept as low as possible to extend the life of the hot cathode. effective.
[0054]
Further, since the leakage beam current when the grid voltage is set to 0 can be suppressed to 5% or less of the beam current when the grid voltage is maximized, the electron beam irradiation is temporarily stopped when the electron beam irradiation is temporarily stopped. The effect of wire leakage does not become a practical problem.
[0055]
Furthermore, since the aperture ratio distribution according to the irradiation intensity distribution of the electron beam to be irradiated from the irradiation window is designed to irradiate a large number of through holes formed in the grid, unlike the case where such an opening is provided in the irradiation window, An excellent effect is obtained that the irradiation intensity distribution of the electron beam can be controlled with a small energy loss.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an electron beam irradiation apparatus according to the present invention.
FIG. 2 is a graph showing measurement results.
FIG. 3 is a graph showing a profile of an electron beam irradiation intensity distribution.
FIG. 4 is an explanatory diagram showing another embodiment in which the grid arrangement is different.
FIG. 5 is a flowchart showing a processing procedure of the electron beam controller.
FIG. 6 is an explanatory diagram showing another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electron beam irradiation apparatus 2 ... Electron beam emission tube 3 ... Electron beam controller 4 ......... Sealing tube (body part)
5. Electron beam irradiation window 6... Anode 7... Irradiation head 8... Hot cathode 9 ... Grid 10 ... Shield tube 11 ... Through hole 21 ... Grid voltage adjusting means 22... Heating power adjusting means V _A ... Acceleration voltage V _G ... Grid voltage I _B ... Beam current W _K ... Heating power L ... Distance D ... Inscribed circle diameter

Claims (2)

An electron beam irradiation apparatus in which an electron beam emission tube having an irradiation head serving as an anode having an electron beam irradiation window provided on one end side of the body is connected to an electron beam controller that supplies power to the electron beam emission tube In
A hot cathode for generating an electron beam and one or more grids are provided in a shield tube having a substantially circular or substantially regular polygonal cross section disposed in a body portion of the electron beam emitting tube,
L ≧ 0.18D × lnV _A
L: Distance from the tip of the shield tube to the tip of the hot cathode (mm)
D: Inscribed circle diameter of shield tube (mm)
V _A : acceleration voltage (kV)
The position of the hot cathode, the size of the shield tube and the acceleration voltage are selected so as to satisfy the relationship
At least one of the grids is formed with a large number of through holes with an aperture ratio distribution designed according to the irradiation intensity distribution of the electron beam to be irradiated from the irradiation window,
The electron beam controller includes a grid voltage adjusting means for adjusting a grid voltage so that a beam current flowing between the hot cathode and the anode is kept constant, and an electron emission capability of the hot cathode by detecting the electron emission capability of the hot cathode. An electron beam irradiation apparatus comprising heating power adjusting means for increasing the heating power supplied to the hot cathode by a preset value when it is determined that the temperature has been reached. In the electron beam emission tube provided with an irradiation head on the one end side of the body part as an anode that forms an electron beam irradiation window,
A hot cathode for generating an electron beam and a grid are provided in a shield tube having a substantially circular or substantially regular polygonal cross section disposed in the body part,
L ≧ 0.18D × lnV _A
L: Distance from the tip of the shield tube to the tip of the hot cathode (mm)
D: Inscribed circle diameter of shield tube (mm)
V _A : acceleration voltage (kV)
An electron beam emission tube characterized in that the position of the hot cathode and the size of the shield tube are selected so as to satisfy the above relationship.

Images