JPS5858800B2 - charged particle device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to suppressing surge voltage generated within a power supply device of a charged particle beam device.

Hereinafter, an electron beam device, which is a type of charged particle device, will be explained as an example.

FIG. 1 is a conceptual diagram showing a conventional electron beam device.
is a power supply device with 10 cathode heating power sources and 1 electron beam acceleration power source.
1. Consists of current limiting resistor 12.

The cathode heating power source 10 includes a first insulation transformer 13, a second insulation transformer 14, a rectifier 15, and a smoothing filter 16.

2 is a coaxial cable, core wires 20, 21, outer shield 2
Consists of 3.

3 is an electron gun, which includes a cathode 31, a Wehnelt electrode 32, and an anode 3.
3, 34 is an electron beam, 35 is a spark discharge in vacuum, 40 is a stray capacitance between the primary winding of the first isolation transformer 13 and the iron core and the secondary winding, and 41 is between the input and output of the rectifier 15. , and 42 is the stray capacitance between the input and output of the smoothing filter 16.

When the terminal of the cathode 31 is connected to the cathode heating power supply 10 via the core wire 20° 21 of the coaxial cable, the current limiting resistor 1
2 to the negative electrode of the electron beam Calorie speed power source 11.

The Wehnelt electrode 32 is connected to the cathode heating power source 1 via the core wire 21.
0 negative electrode (this is connected.

The grounded anode 33 is connected to the outer shield 2 of the coaxial cable 2.
3 to the positive electrode of the electron beam accelerating power source 11.

In the conventional electron beam device configured as described above, the electron gun 2 is
The inside is evacuated and the coaxial cable 2 is connected from the power supply 1 to the
When a predetermined voltage is applied to each electrode of the electron gun 3 via
Thermionic electrons emitted from the cathode 31 heated by Joule heat are accelerated by the voltage applied between the cathode 31 and the anode 33, and an electron beam 34 is generated.

Since a high voltage is applied between the cathode section consisting of the cathode 31 and the Wehnelt electrode 32 and the anode 33, the Wehnelt electrode 3 is disposed on the outermost periphery of the cathode section and faces the anode 33.
A spark discharge 35 may occur in a vacuum between the anode 2 and the anode 33.

Particularly in electron guns used for electron beam welding, electron beam melting, etc., spark discharge 35 in vacuum is likely to occur because a portion of the generated metal vapor flows into the electron gun chamber.

When a short circuit occurs between the Wehnelt electrode 32 and the anode 33 due to the spark discharge 35 in vacuum, the short circuit occurs between the primary winding and the iron core of the first insulation transformer 13 that insulates the cathode power supply 10 from the ground potential, and the secondary winding. A surge voltage is applied to the rectifier 15 and the smoothing filter 16 due to the charges accumulated in the stray capacitance 40 .

FIG. 2 shows an equivalent circuit in which the stray capacitance and inductance of the cathode power supply 10 are replaced by focusing constants C and L.

C40 is the stray capacitance 40. between the primary winding and iron core of the first isolation transformer 13 and the secondary winding. C41 is the stray capacitance between the input and output of the rectifier 15, C4□ is the stray capacitance between the input and output of the smoothing filter 16, Ld and Rd are the self-inductance and resistance of the rectifier, Lf and Rf are the self-inductance and resistance of the smoothing filter 16, S35 is a switch indicating the presence or absence of spark discharge 35 in vacuum, and E is a voltage applied between the iron core and secondary winding of the first isolation transformer 13, which is approximately equal to the electron beam accelerating voltage.

When S35 closes due to a steep spark discharge in vacuum, the charges accumulated in C40 are C41t, C4□ and Rd.

Discharges through Ld, R4, and Lf.

El and R2 at the moment S35 closes are approximated by the following equation.

If C40 C41 C42, Eo = 60 KV, the surge voltage applied to the rectifier 15 and smoothing filter 16 will have the following value.

Since the output voltage of the cathode heating power supply 10 is generally several tens of volts or less, an element with an insulation withstand voltage of 1000 volts or less is used as a component of the cathode heating electrode 10.

For this reason, if a surge voltage of about 20 KV is applied, it will be damaged due to dielectric breakdown.

As described above, in the conventional device, when a spark discharge 35 occurs in a vacuum between the Wehnelt electrode 32 and the anode 33 of the electron gun 3, the primary winding, iron core, and secondary winding of the first isolation transformer 13 A surge voltage is generated inside the cathode thermal power source 10 due to the charge accumulated in the stray capacitance 40 between the
There was a drawback that component parts were damaged due to dielectric breakdown.

This invention has been made with the aim of eliminating the drawbacks of the conventional devices described above.It provides a circuit that allows the charge accumulated in the stray capacitance of the isolation transformer to flow to the Wehnelt electrode, so that when a spark discharge occurs in vacuum in the electron gun, the cathode This suppresses the wavefront value of surge voltage generated in an electron beam control power source such as a heating power source to a predetermined value.

FIG. 3 is a conceptual diagram showing one embodiment of the present invention.
42 is exactly the same as the conventional device described above.

43 is a stray capacitance between the primary winding and the iron core of the second isolation transformer and the secondary winding, and 51 is a capacitor for absorbing surge voltage.

The stray capacitance between the primary winding and the iron core of the first isolation transformer 13 and the secondary winding is shown divided into two parts, 40.40'.

Further, one terminal of the secondary winding of the first insulating transformer 13 is connected to a terminal connected to the Wehnelt electrode 32 among the output terminals of the cathode heating power source 10 by a wiring 52.

FIG. 4 shows an equivalent circuit when a vacuum spark discharge 35 occurs between the Wehnelt electrode 32 and the anode 33 in the electron beam apparatus configured as described above.

In the figure, Ll is the inductance of the secondary winding of the first isolation transformer 13, and Zi is the input impedance of the cathode heating power supply 10 viewed from the input side of the second isolation transformer 14.

When S35 is closed, the charge accumulated in C40 is transferred to wiring: 5
2 and discharge through S35.

The charge accumulated in C40' is discharged through C51 and Zl via power distribution 52 and S35.

Since both ends of C4o, C4□, and C4□ are bright-circuited by the wiring 52, no surge voltage is generated.

The moment S35 closes (when applied to C51, voltage E3
is approximated by the following equation.

The value of the surge absorption capacitor C51 is the stray capacitance C4o
If it is chosen to be sufficiently large compared to ', the crest of the surge voltage E3 can be suppressed.

Since the surge voltage E3 is a surge voltage applied to the human power of the second isolation transformer 14, the surge voltage E3
C51 is selected in consideration of the transformation ratio of and the withstand voltage of the components constituting the cathode heating power supply 10.

E as an example. A design example for -60KV is shown below.

(Design example) ○Transformation ratio of the second isolation transformer 14; 1:115
0 Withstand voltage of the primary winding of the second insulation transformer 14; 00V ○Withstand voltage of the secondary winding of the second insulation transformer 14 and other parts constituting the cathode heating power supply 10; 00V OFirst insulation 100PF in the stray capacitance C40' between the primary winding and iron core of the transformer 13 and the secondary winding ○ Under the above conditions, if C5, -〇, 02μF are selected, the surge voltage E3 is the following value from equation (4). becomes.

The surge voltage applied to the primary winding of the second isolation transformer is 300V, and the surge voltage applied to the secondary winding is 60V.
The cathode heating power supply 1"0 is not damaged by the surge voltage.

FIG. 5 is a conceptual diagram showing a second embodiment of the invention,
A capacitor 53 is connected between one terminal of the secondary winding of the first insulating transformer 13 and a terminal connected to the Wehnelt electrode 32 among the output terminals of the cathode heating power source 10.

FIG. 6 shows the other circuit in this case, and Zio is the impedance between the input and output terminals of the cathode heating power source 10.

When S35 closes, the charges accumulated in C401C40' are discharged through C51j C53tZi and Zio.

Compared to the stray capacitance between the input and output of the cathode heating power supply 10, C53
If the value of E3. is selected to be sufficiently large, the surge voltage E3. E4 is approximated by the following equation.

In this 5, C40 = C4o ' y C5, >> C40t C
5+〉×+.

As shown in equations (6) and (7), stray capacitance C4o
If C51t and C53 are selected to be sufficiently large compared to C51t and C53, the surge voltage generated within the cathode heating power source 10 can be suppressed within a predetermined value.

FIG. 7 is a conceptual diagram showing a third embodiment of the present invention,
A capacitor 5 is connected between both terminals of the secondary winding of the first isolation transformer 13 and both output terminals of the cathode heating power supply 10.
3.53' are connected, and a capacitor 54 is connected between the output terminals of the cathode thermal power source 10.

Figure 8 shows the equal circuit in this case, and Z□ is the cathode heating power source 10.
is the output impedance of

When B53 closes, the charge accumulated on C40t C40 becomes C53+ Zio and C53Z C54t Zl□
Discharge through y Z□.

Surge voltage E4 y E4 at the moment S53 closes
' r E 5 is approximated by the following equation.

As shown in equations (8) and (9), the stray capacitance C40t
If C53yc53't C54 is selected to be sufficiently large compared to c40', the surge voltage generated in the cathode heating power supply 10 can be suppressed within a predetermined value.

In FIGS. 5 and 7, a second isolation transformer 14 is used to transform the input voltage to the cathode heating power source 10 to a predetermined value.
Although shown in the figure, the same effect of the present invention can be expected even when the function of the second isolation transformer 14 is combined with the first isolation transformer 13 and the 20th) isolation transformer is omitted.

FIG. 8 is a conceptual diagram showing a fourth embodiment of the present invention,
This is an example in which there is a plurality of cathode heating power sources.

Reference numeral 60 denotes a bias power source, the negative electrode of which is connected to the Wehnelt electrode 32 via the core wire 22 of the coaxial cable 2.

The cathode heating power supply 10 and the bias power supply 60 have the same configuration as the cathode heating power supply 10 in the first embodiment shown in FIG. rectifier, 66 is a smoothing circuit, 61 is a surge voltage absorption capacitor, 62 is wiring for sanitation current, 6
7/ is the stray capacitance between the primary winding and iron core of the first isolation transformer 63 and the secondary winding.

The wiring 62 of the bias power supply 60 is connected to the Wehnelt electrode 32 via the core wire 22, and the wiring 52 of the cathode heating power supply 10 is connected to the Wehnelt electrode 32 via the core wire 22.
A capacitor 7 is connected between the wiring 62 of the power supply 60.
0 is connected.

Figure 10 shows the equivalent circuit in this case, Z! , Z.

' are the input impedance of the bias power supply 60,
is the output impedance.

S35 is closed, the surge voltage E3. applied to the bias power supply 60 and the cathode heating power supply 10. E3' and E6 are each approximated by the following equations.

Here αo), (11), (As shown in equation 19, compared to stray capacitance C40y C67, C51t C70
If C6□ and C6□ are each selected to be sufficiently large, the surge voltage generated in cathode heating power supply 10 and bias power supply 60 can be controlled within a predetermined value.

Similar effects can be expected by using a fast-response arrester (for example, a voltage-dependent resistance element) in place of the surge voltage absorbing capacitors C5□t, C53t, and C70 in the first, second, third, and fourth embodiments. can.

Incidentally, in the above explanation, an electron beam device consisting of a diode and an electron gun with a diode structure was used as an example, but the invention can be widely applied to devices that generate charged particles such as electron beam devices of other structures and ion beam devices. This is obvious without much explanation.

As is clear from the above description, the present invention relates to a charged particle generator having a grounded accelerating electrode and an ungrounded control electrode; In a charged particle device comprising a power supply device having a control power source for particle generation and a charged particle acceleration power source, and a coaxial cable connecting the power supply device and the charged particle generator, non-grounding control of the charged particle generator. When a spark discharge occurs in a vacuum between the electrode and the ground potential member, between the primary and secondary windings and between the iron core and the insulation transformer that insulates the control power source for generating charged particles from the ground potential.
It is characterized by comprising a circuit for flowing the charge accumulated in the stray capacitance between the next windings to the electrode closest to the ground potential member among the non-grounded control electrodes of the charged particle generator,
When a spark discharge occurs in a vacuum between the electrodes of the charged particle generator, the wave front value of the surge voltage generated inside the control power supply for charged particle generation due to the stray capacitance of the isolation transformer is suppressed to within a predetermined value. can do.

Therefore, it is possible to prevent dielectric breakdown of the components constituting the charged particle generation control power source due to the stray capacitance of the isolation transformer.

Furthermore, since elements with low withstand voltage can be used as components of the power source for generating charged particles, the device becomes inexpensive.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of a conventional electron beam device, and Figure 2 is a conceptual diagram of a conventional electron beam device.
In the electron beam device shown in the figure, an equivalent circuit diagram when a spark discharge occurs in a vacuum inside the electron beam generation source, FIG. 3 is a conceptual diagram showing an embodiment of the present invention, and FIG. An equivalent circuit diagram, FIG. 5 is a conceptual diagram showing a second embodiment of the present invention, FIG. 6 is an equivalent circuit diagram in FIG. 5, and FIG. 7 is a conceptual diagram showing a third embodiment of the present invention. 8th
The figure is an equivalent circuit diagram of FIG. 7, and FIG. 9 is an equivalent circuit diagram of the fourth embodiment of the present invention.
FIG. 10 is an equivalent circuit diagram of FIG. 9. In the figure, 1 is a power supply, 2 is a coaxial cable 3 is an electron gun, 10 is a cathode heating power supply, 60 is a bias power supply, 13.
63 is the first isolation transformer, 40° 67 is the stray capacitance of the first isolation transformer 13, 63, 20, 21, 22 is the core wire of the coaxial cable, 35 is the Wehnelt electrode 32 and the anode 33
51.53, 54, and 70 are surge voltage absorbing capacitors, and 52.53 is surge voltage control wiring. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A charged particle generator having a grounded accelerating electrode and a non-grounded electrode, an accelerating power source that supplies accelerating power between the Calorie velocity electrode and the non-grounded electrode, and the above non-grounded electrode. In those equipped with a power source for driving non-grounded electrodes that is insulated from the ground potential by an isolation transformer that supplies driving power to the grounded electrodes,
A discharge low impedance circuit is provided to connect between the output terminal of the secondary winding of the insulation transformer and the non-grounded electrode, and when a spark discharge occurs between the non-grounded electrode and the accelerating electrode, the A charged particle device characterized in that the charged particle device is configured to discharge the charge of the secondary winding of the transformer through the low impedance circuit for discharging. 2 When the non-grounded electrode and one output terminal of the secondary winding of the isolation transformer are connected, S and the other output terminal of the secondary winding are sufficiently larger than the stray capacitance of the secondary winding. The charged particle device according to claim 1, comprising a low impedance circuit for discharging connected by a capacitor or aresph having a capacitance. 3 Discharge connected between the output terminals of the secondary winding of an isolation transformer and between one of these output terminals and a non-grounded electrode with a capacitor or Aresph having a capacitance sufficiently larger than the stray capacitance of the secondary winding. 2. A charged particle device according to claim 1, comprising a low impedance circuit. 4 A capacitor with a capacitance sufficiently larger than the stray capacitance of the secondary winding is connected between the output terminals of the power supply for driving the non-grounded electrodes, and between both of these output terminals and both output terminals of the secondary winding of the isolation transformer. The charged particle device according to claim 1, further comprising a discharge low impedance circuit connected by an Aresph.