JP2005209424A - Beam stopping mechanism of scanning type electron beam irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a beam stopping mechanism of an electron beam irradiation device having a long life at low cost, of a type, to which filament power is provided by a motor generator method, capable of instantaneously nullifying the electron beam, and easy to re-start. <P>SOLUTION: In a high-voltage stand, a high-voltage power terminal N and a first acceleration electrode K are not directly connected to a filament power source M of a high potential part, but connected through a parallel circuit of a switching element and a resistor R; the switching element is switched by the power source installed in the high-voltage stand and a light-receiving element; a switch control signal is transmitted from the light-emitting element formed at a grounding side to the light-receiving element at a high-voltage side; and draw-out and stopping of the electron beam is to be controlled from grounding side. Thus, by turning on the switching element, the potential of the first electrode K is made same with that of the filament M, and the electron beam is drawn out to an acceleration tube, and by turning off the switching element, the potential of the first electrode K is made higher than that of the filament M to prevent the electron beam from coming out, and the draw-out of the electron beam is quickly stopped. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mechanism for suddenly stopping an electron beam in a scanning electron beam irradiation apparatus. An electron beam irradiation device is a variety of devices such as polymer heating, sterilization, coating film curing, waste gas treatment, etc. by heating filaments in vacuum, generating thermoelectrons and accelerating them through the window foil and taking them out to the atmosphere. It is a device that performs the function. The acceleration voltage and the form of conveyance vary depending on the type and purpose of the workpiece.

  The electron beam irradiation apparatus has a vacuum part for generating and accelerating an electron beam and an atmospheric pressure part through which an object is processed. The part that generates the electron beam is mounted on a high-voltage mount. The part that conveys the workpiece is ground voltage (ground potential). The transport portion is surrounded by a casing partitioned by heavy metal walls. The conveyance mechanism is an endless circular conveyor or the like when the object to be processed is a solid having a fixed shape. A vibration conveyor or the like is used when an object whose form is not determined is a workpiece. X-rays are emitted when an electron beam hits a conveyor or workpiece. The transport mechanism is heavily surrounded by a metal casing so that X-rays do not leak outside. Since X-rays oxidize air to generate ozone, an atmosphere in which air is replaced with nitrogen gas or argon gas may be used inside the housing.

  Electron beam irradiation apparatuses are classified into a scanning type and a non-scanning type (area type) depending on whether or not the beam is scanned. In the case of a high acceleration voltage of 5 MeV to 500 keV, a scanning type that scans the beam is used. If it is lower, a non-scanning type is often used. Of course, the object to be processed and the purpose of irradiation differ depending on the electron energy.

  The scanning electron beam irradiation apparatus includes a high-voltage power supply unit, a vacuum exhaust device, a thermoelectron generation chamber, a filament, a filament power supply, an acceleration tube, a scanning tube, an irradiation window, a transport mechanism, a housing, and the like. The high-voltage power supply often uses a cockcroft-type power supply circuit in which a rectifier and a capacitor are combined to double voltage rectify a commercial power supply and repeat double voltage rectification to obtain a negative high voltage. The high-voltage power supply and the thermoelectron generation chamber are mounted on a high-voltage stand that is insulated from the ground. As described above, the high-voltage power source has a high negative voltage of 5 MeV to 500 keV and gives electron acceleration energy.

The filament power supply is different. The voltage itself is low and the current value is large. The filament must be on the high-voltage gantry and insulated from the ground side. Even with an isolation transformer, such high voltage cannot be completely isolated. Therefore, a mechanism is used in which a motor is provided on the ground side, a generator is provided on the high-voltage gantry side, and the motor shaft and the generator shaft are directly connected by an insulating rod.

The insulating rod is provided across the ground side and the high pressure side. Rotate the motor with commercial power on the ground side. It is an insulating rod that is transmitted to the generator on the high-voltage gantry side and turns the generator. Thereby, a low voltage alternating current is generated and applied to the filament. In this way, a double conversion mechanism that converts electrical energy into mechanical energy and further converts into electrical energy is used. The alternating current obtained by the generator is connected to both ends of the filament through an insulating transformer. In order to determine the potential of the filament, the negative electrode potential of the acceleration high-voltage power source is applied to the intermediate terminal of the secondary coil of the insulation transformer. Thereby, the average potential of the filament becomes the potential of the negative electrode of the acceleration power source.

When a low voltage alternating current is passed through the filament, the filament generates heat. Thermoelectrons jump out of the filament because it is in a vacuum and a negative high voltage is applied.
The accelerating tube is a vertically long vacuum tube following the thermoelectron generation chamber, and is formed by superposing a large number of ring-shaped accelerating electrodes and insulating rings. For example, the acceleration electrodes are vertically arranged at intervals of 2 cm to 3 cm, and a voltage of 30 keV to 50 keV is distributed per stage. A voltage dividing resistor is connected to the accelerating electrode in order to equally distribute the voltage from the first electrode closest to the filament to the m-th electrode on the ground side.

  Directly below the acceleration tube is a triangular tube-shaped scanning tube. There is a scanning coil in the upper part of the scanning tube, and an alternating current flows. As a result, an alternating magnetic field is formed, and the electron beam can be scanned left and right. The lower part of the scanning tube is an opening. This is called an irradiation window. The opening of the irradiation window is covered with a window foil of Ti and Al. The window foil is for separating the upper vacuum and the lower atmospheric pressure. When the electron beam penetrates the window foil, energy loss occurs and the window foil is heated. The window foil is cooled by a water cooling and air cooling mechanism. The object to be processed is carried by the transport mechanism in the atmospheric pressure space immediately below the window foil. By scanning the beam in a direction (y direction) orthogonal to the transport direction (x direction), the entire surface of the workpiece can be irradiated with an electron beam.

  In a scanning electron beam irradiation apparatus, a beam shutter is used to quickly block electron beam irradiation on an irradiated object while maintaining an acceleration voltage for accelerating the electron beam.

  The beam shutter is a movable water cooling plate that can move horizontally. Air pressure is used to drive the beam shutter. Move between the irradiation window and the object to be irradiated. During the irradiation work, the shutter is shifted to the side from the irradiation window. At the time of interruption, the beam shutter moves horizontally and moves directly below the irradiation window. The beam shutter stops irradiation by directly blocking the beam.

  FIG. 1 is a schematic configuration diagram of an electron beam irradiation apparatus having a beam shutter for showing a conventional example. This uses a cockcroft power supply as an acceleration power supply. Filament power is supplied by a ground-side motor and a high-voltage generator. The filament 2 is provided in a thermoelectron generation unit above the acceleration tube 3. Filament 2 has a negative high voltage. When the filament 2 is heated, thermoelectrons are emitted. The thermoelectrons are accelerated by the acceleration electrode of the acceleration tube 3 to which a high voltage is applied. The acceleration electrodes are connected by a voltage dividing resistor. The beam is scanned left and right by the scanning coil 4 below the accelerating tube 3. An irradiation window 6 is provided on the lower surface of the scanning tube 5 and a window foil is applied. There is a transport mechanism surrounded by a casing under the irradiation window 6, and the workpiece 7 is on the transport mechanism. The electron beam is accelerated by the accelerating tube, exits from the irradiation window to the atmosphere, and hits the object 7 to be processed.

  The beam shutter 8 is provided between the irradiation window 6 and the workpiece 7 so as to be able to advance and retract horizontally. The beam shutter is a horizontal metal plate that allows cooling water to pass through it and cool the entire plate. Although supported by rollers and rails, the support mechanism is not shown. The beam shutter 8 is connected to an air cylinder 9 via a rod. The air cylinder 9 is connected to a pump via an electromagnetic valve 22. Compressed air 23 is introduced from the pump into the air cylinder 9 through an electromagnetic valve. The sequencer 20 of the control panel opens and closes the electromagnetic valve 22. Normally, the beam shutter is retracted, and the electron beam hits the workpiece 7.

  When it is necessary to stop the beam urgently, the electromagnetic valve 22 is opened by the signal from the sequencer 20, air is introduced, the air cylinder 9 is extended, and the beam shutter 8 is closed. FIG. 1 shows a state in which the beam shutter is closed. The electron beam is cut off directly under the irradiation window so that the electron beam does not hit the workpiece.

  The beam shutter 8 directly blocks the electron beam. Even when thermionic electrons continue to be emitted and the electron beam remains emitted, the electron beam does not strike the object to be processed. This does not require stopping the acceleration power source and the filament power source. There is an advantage that it is easy to resume beam irradiation.

  The beam shutter 8 is most commonly used for a beam emergency stop device of an electron beam irradiation device. However, the operation time of the beam shutter requires about 3 seconds. Because it moves heavy metal plates, it can't be helped. In some cases, such a delay is acceptable. However, delaying the beam stop may cause fatal damage to the workpiece, so it may be necessary to stop it more quickly.

  In addition, the beam shutter 8 has a limited irradiation interruption duration depending on the electron dose and the cooling water amount. When an electron beam hits the beam shutter, all the kinetic energy is changed to heat, so the beam shutter is heated. Although the cooling water passes through the inside, it is still insufficient and if the electron beam is blocked for a long time, the beam shutter is deteriorated.

Japanese Patent Application No. 2002-237728

  Japanese Patent Application Laid-Open No. H10-228707 is for the present applicant. Focusing on the fact that the beam shutter is slow, so the filament power is given by the ground-side motor and the generator on the high-voltage gantry. Has been proposed, and a mechanism for instantaneously reducing the filament power to zero is proposed. Since there is inertia of the motor and generator rotor and the thermoelectrons do not stop immediately even when the filament power supply voltage becomes zero, there is also a delay time of about 3 seconds. Depending on the type of object to be processed and the purpose of irradiation, it may be too slow.

  In the electron beam irradiation apparatus, a conventionally used beam shutter moves a water-cooled plate having a large weight, and thus requires a long time to move. There is a time delay until the beam is cut off by the moving time. Therefore, the delay time until the electron current is cut off is about 3 seconds.

  As a method of cutting off the electron beam, there is also a method of cutting off the main power source that is a power supply source. That is, the negative high voltage is reduced to 0 so that the high voltage is not applied to the filament, and the extraction of thermoelectrons is stopped. In this method, since the high voltage is lowered to 0 V, a discharge time is required and a delay time is long. The acceleration voltage is also cut off at the same time. All capacitors of cockcroft power supply are discharged. It takes time to charge all this again. Therefore, the next irradiation cannot be performed promptly. There are such drawbacks.

  It is also possible to shut off the filament power by stopping the motor for supplying power to the filament. However, since the rotation of the motor having a force of inertia and the generator cannot be stopped immediately, the electron current interruption is delayed. There is a delay of about 3 seconds between filament current interruption and electron beam stop.

  A means to stop the electron flow more quickly is desired. I don't want to move heavy objects because they stop and pass the beam quickly. In addition, if the acceleration power supply is set to 0 V, it takes too much time to start up again. If the filament power is also reduced to 0V, it takes time to start up again.

In a normal electron beam irradiation apparatus, the negative electrode N of the high-voltage power supply is connected to the intermediate terminal M of the filament power supply transformer and the first acceleration electrode K (V _N = V _M = V _K ). In the present invention, the negative electrode N of the high-voltage power source is connected to the first acceleration electrode K, but it is not directly connected to the intermediate terminal M of the filament power transformer, and the resistor R having a high value and the switch element are connected in parallel (V _N = V _K ≠ V _M ).

At the time of electron beam irradiation, the switch element is closed, and the filament power transformer intermediate potential M, the potential of the first acceleration electrode K, and the power supply voltage N are made the same (V _N = V _M = V _K ). However, when it is necessary to stop the beam urgently, the switch element is turned off so that the current flows from the filament side M to the first electrode K through the resistor R, and the first acceleration electrode K is set to be higher than the filament power supply M voltage. A low voltage (V _K <V _M = V _N ) is set so that electrons emitted from the filament are pushed back by the first acceleration electrode K.

  Since the signal wire cannot be drawn across the ground side and the high-voltage mount, transmission and reception of signals are performed by optical signals. The switch element is opened and closed by a light receiving element provided on the high voltage gantry, and a light emitting element is provided so as to face the light receiving element, and the light emission of the light emitting element is controlled from the ground side to send a signal to the light receiving element. The combination of the light emitting element (LED; LD) and the light receiving element (PD) does not break the insulation between the ground side and the high voltage side.

The present invention is an electron beam repels electrons by raising the potential V _K of the first accelerating electrode of the accelerating tube from the filament voltage V _M is accelerated in the electron beam irradiation apparatus of the type supplying filament power in motor generator system Do not go out to the tube. Since the switch element can be turned on and off only, the operation is quick. It takes less than 3 seconds and can cut off the beam in less than 1 second.

The high voltage power supply (cockcroft power supply) is not turned off. Therefore, the electron beam can be stopped quickly while maintaining the acceleration voltage, and irradiation to the irradiated object can be stopped instantaneously.
It does not cut off the filament power. The motor / generator remains rotating. The filament continues to light up.

  Since the filament continues to be lit while the acceleration voltage is generated, the subsequent electron beam irradiation can be resumed promptly. In that respect, the beam can be restarted more easily than when the acceleration power supply (cockcroft power supply) is turned off. The beam can be resumed more quickly than when the filament power is cut off.

  Furthermore, it has excellent durability because it has fewer mechanical parts than a beam shutter. Since the beam shutter moves a heavy metal plate horizontally, rails, rollers, gears, etc. are worn out. Further, if the electron beam is blocked by the beam shutter, the beam shutter is heated by the electron beam, so a large amount of cooling water is required.

  Since the present invention does not block the electron beam with a plate, cooling is unnecessary. Therefore, useless power is unnecessary. Power consumption is reduced. Compared with the beam shutter, the beam is cut off quickly.

  However, since the beam is blocked by the presence of the leaking beam, the beam blocking of the present invention is not perfect. However, the leakage beam does not adversely affect the object to be processed unless it is a special object to be processed. More on that later.

An electron beam irradiation apparatus according to an embodiment of the present invention will be described with reference to FIG.
The filament 2 is at the top of the accelerating tube 3, from which thermionic electrons exit. A scanning tube 5 having a triangular spread continues below the longitudinally accelerating tube 3. A scanning coil 4 is provided at the end of the acceleration tube 3 and scans the electron beam left and right. The scanned electron beam passes through the window foil of the irradiation window 6 immediately below the scanning tube 5 and is irradiated onto the object 7 to be processed. The workpiece 7 is sent in a direction (x direction) orthogonal to the scanning direction (y direction) by a transport mechanism (not shown).

The acceleration power source 25 is a cockcroft type in which a rectifier and a capacitor are connected in series. AC power is supplied from the main power source (commercial power source: E ₁ ) to the primary winding of the transformer 26 via the main power regulator 24. One terminal S of the secondary winding of the transformer 26 is connected to the ground. On the secondary winding side, a series body of capacitors 27, 28, and 29 and a series body of capacitors 30, 31, and 32 are connected.

Only 3 pairs are drawn here, but there are many more. The capacity, breakdown voltage, and number of capacitors are appropriately determined according to the required acceleration voltage and beam current. Rectifiers 33, 34, 35, 36, 37, and 38 are connected in a staggered manner between the capacitors on both sides. A negative high voltage V _N (acceleration voltage: V _N <0) is generated between SN between the start and end of the series capacitor. This is a cockcroft type in which capacitors are sequentially stored for every half wave of alternating current, and is a common series full-wave rectifier circuit. Of course, other circuits may be used.

This gives kinetic energy to the electron beam. Since it is a scanning type, it is often 500 keV or more. The acceleration voltage V _N can be measured by resistors 40, 42, 43, 44 and an ammeter 45 connected in series from the negative power supply pole to the ground side. If the total resistance of the resistor is R _m and the current flowing through the ammeter 45 is I _a , the power supply voltage is given by V _N = −R _m I _a . So the supply voltage is constantly monitored. The signal is input to the control unit 48.

The power source for heating the filament 2 is completely different from the acceleration power source 25. From the external power source E _2, the power supplied to the motor inverter 49 provided on the ground side. The motor inverter 49 once converts external power into direct current and reversely converts it into alternating current of an arbitrary frequency f. The motor inverter 49 rotates the AC motor (D) 50 on the ground side. Since AC motor D changes the number of rotations by changing the frequency, motor inverter 49 is required. The output shaft of the motor 50 is directly connected to the input shaft of the generator (G) 53 on the high voltage gantry side by an insulating rod 52.

The insulating rod 52 is passed between the ground side and the high voltage side, but since this is an insulator, the insulation between the ground and the high voltage side can be maintained. Since the generator (G) 53 rotates on the high voltage side, AC power is obtained. Since the power of the generator is proportional to the number of revolutions, the generator output can be freely adjusted by controlling the number of revolutions.

  The outputs 54 and 55 of the generator 53 are converted into a large current by a transformer 59 at a low voltage suitable for driving the filament 2. The transformer 59 also serves to insulate the generator 53 from the filament 2. Secondary wires 60 and 62 of the transformer 59 are connected to both ends of the filament 2. Let M be the intermediate terminal of the transformer.

The acceleration tube 3 is provided with a number of ring-shaped acceleration electrodes 72, 73,. It does not mean that the number of electrodes is eight. The number of electrodes is arbitrary. The number of electrodes appropriately increases or decreases depending on the magnitude of the voltage. The first electrode, the second electrode, etc. are called from the electrode closest to the filament. A glass insulating ring is provided between the ring-shaped acceleration electrodes 72, 73,. Voltage dividing resistors 82, 83,... 89 are connected between the acceleration electrodes. The last electrode 79 is grounded via an ammeter 90. The current I _c, which is measured by the ammeter 90 is an electron beam current impinging on the accelerating electrode.

The electron beam emitted from the filament 2 strikes the workpiece 7. Some are lost in window foil. Some do not hit the workpiece and hit the transport mechanism. Those electron beam currents can be measured by an ammeter 46 connected to the ground side terminal S of the acceleration power source 25. The current _Ib is an electron beam current. I _c + I _b is equal to the total electron current emanating from the filament.

The electrode N (potential V _N <0) of the acceleration power supply 25 is connected to the first electrode 72 (K). Since there is a voltage dividing resistance, a voltage in which V _N is equally distributed is applied to the acceleration electrodes 72, 73,.

Such a structure is the same as the conventional example.
In the conventional structure, the electrode N and the first electrode K of the high-voltage power supply 25 and the intermediate terminal M of the filament power supply are connected together. Otherwise, the potential of the filament 2 will float and will not be accelerated even if electrons are emitted from the filament. In other words, there is a connection relationship of K-N-M (V _K = V _N = V _M ), and the electric potential of the electrons emitted from the filament is V _N , so that it is accelerated between the ground.

  However, in the present invention, the high voltage power supply N and the first acceleration electrode K are connected, but the filament potential M is not directly connected. A resistor 64 having a high resistance value and a switch element 63 are connected in parallel between NK and M. The switch element 63 is an arbitrary high-speed semiconductor element such as a transistor or FET.

  A new power supply circuit is required for the switch element 63. It can be taken from the generator 53 (G). Part of the filament power is used for the switch element. The power supply circuit 56 takes AC power from the generator outputs 54 and 55 and converts it to a DC voltage of an appropriate voltage. It also serves as a power source for the light receiving element (PD, APD, phototransistor PTR) 57. The power supply circuit 56 supplies power to the drive circuit 58. A light emitting element 67 is disposed so as to face the light receiving element 57. The light emitting element 67 is on the ground potential side and is driven by a light emitting element driving circuit 66 connected to the sequencer. The optical signal is used to maintain the insulation between the ground side and the high voltage gantry.

  The light receiving element 57 receives a signal from the light emitting element 67. A drive circuit 58 that amplifies the output of the light receiving element 57 turns the switch element 63 on and off. Normally, there is no light emitting element signal, the light receiving element does not receive the signal, and the switch element 63 is conductive. The power supply terminal N and the filament intermediate terminal M are connected by a switch element and have the same potential. In order to stop the beam urgently, the light emitting element 67 is turned on to send an optical signal to the light receiving element 57, the switch element 63 is turned off, the filament potential M is set higher than the power supply N (the absolute value is lowered), and the beam is stopped. .

  The relationship between the light emitting element 67 and the light receiving element 57 is not limited to simple on / off signal transmission, and the switch element 63 may be switched on / off by changing the frequency, amplitude, or waveform. It should be devised so that it does not malfunction due to external noise.

At the time of beam extraction, the switch element 63 is turned on. The high-voltage power supply N, the first acceleration electrode K, and the filament M are at the same potential (V _K = V _N = V _M ). Since the potential is the same, the first accelerating electrode K does not disturb the electron motion. Since the second accelerating electrode and lower electrodes have a higher potential (negative and lower absolute value), electrons can be attracted. Therefore, thermoelectrons are extracted from the filament and guided to the acceleration tube.

When it is desired to urgently cut off the beam, the switch element 63 is turned off. Then, the potentials of the high voltage power supply N, the first acceleration electrode K, and the filament M are different. A current flows through the resistor 64 from the filament potential M toward the power supply potential N. Although the current I _x is small, since the resistance value R of the resistor 64 is large, the potential difference RI _x (positive) becomes considerably large. V _M = RI _x + V _N Since the filament power supply potential increases (V _K = V _N <V _M <0), the potential of the first acceleration electrode K decreases when viewed from the filament electrons. Since the electrons are accelerated toward the higher potential, they are decelerated by the first acceleration electrode K. That is, the first acceleration electrode K cannot be overcome. This stops the electron beam.

  However, the beam blocking method of the present invention is not perfect for beam blocking such as beam shutter closing, acceleration power off, and filament power off. Some leakage electron beam is generated. It is unavoidable.

  This point is a little difficult to understand, but it is as follows. It is assumed that the switch element is conductive and the object 7 is irradiated with an electron beam from the filament through the acceleration tube 3 and the scanning tube 5. Here, it is assumed that the switch element 63 is turned off. From that moment on, the filament potential begins to rise.

As a result, the beam extraction current I _b (taken positive) decreases. Since the same current flows through the resistor 64, the voltage drop between NM (between KM) is V _f = RI _b . This is the difference between the filament average potential M and the potential of the first acceleration electrode K. When the potential difference between the filament potential and the first accelerating electrode is about 100 V, the beam is hardly extracted. Decreases the beam current _{I b,} the beam current is not reduced more when the 100 V = RI _b. If it decreases below that, the deterrence of the first accelerating electrode disappears, and the beam starts to increase. If it exceeds that, the first accelerating electrode voltage rises and the electrons are driven back.

  Therefore, when the resistance value of the resistor 64 is about 100 MΩ, the critical ion beam becomes about 1 μA. There is such a leakage ion beam, and the potential difference between the first electrode K and the filament potential M can be maintained at about 100V. The value of the leakage beam can be determined by the value R of the resistor 64.

  A minute leak beam of about 1 μA will not adversely affect the workpiece. As described above, the method of the present invention has a drawback that the beam cannot be completely blocked because the voltage of the first accelerating electrode is increased by the leakage beam. However, it is almost safe.

  The first acceleration electrode K blocks the electron beam only by changing the switch element 63 from on to off. There is no need to move a heavy beam shutter or to stop the rotor of an inertial motor / generator. Since only the semiconductor element is turned on and off, the operation is quick. The delay time can be reduced to about 1 ms.

  A further advantage is that the acceleration power supply 25 does not need to be cut off, and the potential of the electrode N is maintained at a negative high voltage, so that there is no time delay for charging the high voltage for beam resumption. That is. There is no need to turn off the filament power supply. Although the filament remains lit, the first accelerating electrode K is at a negative potential from the filament and is not extracted as an electron beam. In this way, the beam can be stopped urgently while the acceleration power supply filament power is on, so that it does not take time to resume the beam irradiation.

FIG. 3 is a schematic cross-sectional view of an electron beam emergency shut-off device using a beam shutter in an electron beam irradiation device. BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the electron beam emergency cutoff apparatus of the scanning electron beam irradiation apparatus concerning the Example of this invention.

Explanation of symbols

2 Filament
3 Accelerating tube
4 Scanning coil
5 Scan tube
6 Irradiation window
7 Workpiece
8 Beam shutter
9 Air cylinder
20 Sequencer
22 Solenoid valve
23 Compressed air 24 Main power regulator
25 Cockcroft high-voltage power supply (acceleration power supply)
26 transformer
27-32 capacitors
33-38 Rectifier
40-44 resistance
45 Ammeter for power supply voltage measurement
46 Electron Beam Current Measurement Ammeter
47 Sequencer
48 Control unit
49 Motor inverter
50 motor
52 Insulating rod
53 Generator
54, 55 Generator output 56 Power circuit
57 Light receiving element
58 Drive circuit (amplifier circuit)
59 Trans
60, 62 Filament power line
63 Switch element
64 resistance
66 Light emitting element control system (by sequencer)
67 Light Emitting Element
72-79 Accelerating electrode
82-89 Partial resistance
90 Ammeter for accelerating electrode leakage current measurement

Claims (1)

Accelerating power source that generates negative high voltage provided in the high voltage part, filament that generates thermoelectrons in vacuum in the high voltage part, and rotating the high voltage generator with the ground side motor A filament power supply in a high voltage section for generating a voltage, an accelerating tube having a plurality of accelerating electrodes for accelerating electrons in vacuum to form an electron beam, a scanning tube for scanning the accelerated electron beam, and a lower portion of the scanning tube In a scanning electron beam irradiation apparatus having an irradiation window having a window foil, a transfer device that conveys an object to be processed so as to pass directly under the irradiation window, and a casing surrounding the transfer device, a filament power supply potential at a high voltage portion M is connected directly to the high voltage negative electrode N of the acceleration power source and the first acceleration electrode K of the acceleration tube, and the filament power source potential M is connected to the negative electrode N and the acceleration electrode K by a resistor and a switch element arranged in parallel. Elementary Is driven to be opened and closed by a light receiving element provided on the high voltage side, and from the light emitting element provided on the ground side to send a close signal to the light receiving element, and the filament voltage V _M by closing the switching element, the potential of the first electrode V _K, equal the acceleration power supply potential V _N draws heat electrons from the filament, the filament voltage V _M by opening the switch, withdrawal of the electron beam is higher than the first accelerating electrode potential V _K, and acceleration power supply potential V _N The beam stop mechanism of the scanning electron beam irradiation apparatus is characterized in that the beam is almost stopped.

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