JP3133155B2 - Electron beam accelerator and bending magnet used for the accelerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam accelerator used for, for example, ultra-fine LSI microfabrication and a bending electromagnet used for the accelerator.

[0002]

2. Description of the Related Art Generally, an electron beam accelerator accelerates an electron beam to a high energy state of 1 billion electron volts (1 GeV) or more. Recently, synchrotron radiation (SOR light) has been radiated from the electron beam. Application to new fields such as ultra LSI microfabrication (lithography) has attracted attention.

[0003] Many electromagnets are used in an electron beam accelerator, and a bending electromagnet and a quadrupole electromagnet are indispensable among them. The bending electromagnet serves as a guide magnetic field for deflecting the electron beam and rotating on a predetermined circular orbit, and the quadrupole electromagnet converges the electron beam,
It has the function of stabilizing the electron beam by diverging.

FIG. 7 shows a schematic configuration of a conventional electron beam accelerator.
Shown in This electron beam accelerator has a linear accelerator 1,
The linear accelerator 1 generates electrons and accelerates them to tens of millions of electron volts (tens of MeV). The electron beam emitted from the linear accelerator 1 passes through the transport pipe 2, and is injected into the center of the vacuum duct 4 by the injector 3. Guided on the set design trajectory. The vacuum duct 4 is maintained in a high vacuum state in order to prevent the electron beam from colliding with the residual gas and causing loss.

The electron beam that has entered the vacuum duct 4 is applied with a magnetic field in a predetermined direction (in the figure, a magnetic field extending from the front to the back of the paper) in a predetermined direction (clockwise in the figure). While being deflected, the electron beam is converged and diverged by the quadrupole electromagnet 6, and the electron beam incident from the linear accelerator 1 is accelerated by the high-frequency acceleration cavity 7 to higher energy (about GeV).

The orbital position of the electron beam in the vacuum duct 4 is monitored by a beam position monitor 8.
The synchrotron radiation port 9 takes out the synchrotron radiation emitted in the tangential direction of the deflection curvature of the deflection electromagnet 5, and the vacuum duct 4
It is attached by welding.

FIG. 8 shows a cross section of the beam position monitor 8. The beam position monitor 8 is usually provided with four pickup electrodes 10 and four introduction terminals 11 for extracting signals from these pickup electrodes 10, which are attached to the vacuum duct 4.

Therefore, when the electron beam passes through the center O of the vacuum duct 4, the beam is
Although the voltage induced to 0 is the same, for example, if the beam shifts in the lower right direction in the figure, the induced voltage of the lower right pickup electrode 10 is large, and the others are small. Therefore, these four voltage values are compared. Thereby, the beam position can be known.

The beam position monitor 8 has an introduction terminal 11
Are protruding, so that it is difficult to install them in the portion where the electromagnet is arranged, and is usually installed in the straight portion of the vacuum duct 4 where the electromagnet is not arranged.

FIG. 9 schematically shows an example of the radiation light monitor 12. The emitted light monitor 12 is attached to the tip of the emitted light port 9, and four photodiodes 13 are arranged. The emitted light emitted in a direction perpendicular to the paper surface has a Gaussian distribution. If the center of this radiation light distribution is at the center O 'of the photodiode 13 divided into four, the output voltages of the four photodiodes 13 are the same, but the output voltage shifts from the center O'. By comparing the four output voltages, the position of the center of gravity of the emitted light can be known. Then, if the position of the center of gravity of the emitted light is known, it can be obtained by converting the position of the electron beam, which is the emission point of the emitted light.

FIGS. 10 to 12 show a cross section of the bending electromagnet 5, which is made of a ferromagnetic material and has a vacuum duct 4. As shown in FIG.
, A yoke 15 constituting a magnetic circuit with the magnetic pole 14, and a magnetic pole 14
A plurality of tightening bolts 16 for fixing the
Upper and lower excitation windings 17 wound around each of the above, a plurality of upper and lower correction windings 18 for correcting the trajectory of the electron beam,
It comprises a plurality of holders 19 and 20 for fixing the excitation winding 17 and the correction winding 18.

A vacuum duct 4 maintained in an ultra-high vacuum is disposed between the magnetic poles 14, and the electron beam moves in the center of the vacuum duct 4 in a direction perpendicular to the plane of the drawing. For example, if the beam is an electron and travels from the back surface to the front surface in FIG. 10 and the upper magnetic pole of the deflection magnetic field is an N pole and the lower magnetic pole is an S pole, the electron beam is applied to the holder 19 according to Fleming's left-hand rule. It receives a deflection force to the side.

[0013]

By the way, it is impossible to ideally produce the magnetic field of the bending electromagnet 5 or the quadrupole electromagnet 6, and the magnetic field deviates from the design value. In addition, it is impossible to install these magnets without any error.
A slight deviation and a rotation of about 0.3 mrad must be allowed. Due to the error magnetic field resulting from such fabrication and installation, the beam trajectory is necessarily deviated from the ideal value. In order to make the beam trajectory as close as possible to the ideal value, a correction electromagnet is used in the electron beam accelerator, and the correction winding 18 of the deflection electromagnet 5 is also provided for this purpose.

[0014] Even if the beam trajectory is corrected once, the beam trajectory drifts due to fluctuations in the power supply, changes in the surrounding environment, and the like. Then, in order to correct the beam trajectory, it is necessary to know the beam position in the vacuum duct 4, and therefore, the beam position monitor 8 and the radiation light monitor 12 are used.

However, conventionally, one of the bending electromagnets 5
Since the number of correction windings 18 per unit is small, only the signals of the two beam position monitors 8 installed in the vacuum duct 4 before and after the bending electromagnet 5 in the beam traveling direction are used for correction, The optical monitor 12 is used for positioning the intensity of the emitted light and the sample to be irradiated with the emitted light, and the beam position information obtained from the monitor 12 has not been used effectively. For this reason, the correction of the beam trajectory in the bending electromagnet 5 was insufficient.

Further, as shown in FIG. 12, the conventional correction winding 18 is wound around the entire magnetic pole 14 similarly to the excitation winding 17, so that the correction amount, that is, the correction amount, The magnitude of the exciting current of the correction winding 18 is only one type, and the correction function is insufficient. For this reason, in the related art, the deviation of the beam trajectory in the bending electromagnet 5 is large, and the width of the vacuum duct 4 and the width of the magnetic pole 14 must be increased, which causes the deflection electromagnet 5 and the vacuum duct 4 to become large. was there.

The present invention has been made in view of the above circumstances, and controls the amount of excitation of a correction winding of a bending electromagnet based on beam positions obtained from both a beam position monitor and a radiation light monitor. It is another object of the present invention to provide an electron beam accelerator capable of reducing a deviation of a beam trajectory in a bending electromagnet.

Another object of the present invention is to provide a small and high-performance bending electromagnet for an electron beam accelerator, which has an improved correction function to reduce the deviation of the beam trajectory, and has a narrow magnetic pole width.

[0019]

In order to solve the above-mentioned problems, an electron beam accelerator according to the present invention deflects an electron beam along a beam trajectory in a vacuum duct by a deflecting electromagnet. In an electron beam accelerator for extracting radiation emitted in a tangential direction of a curvature from a radiation light port, a plurality of beam position monitors provided in the vacuum duct, a radiation light monitor provided in the radiation light port, A plurality of correction windings provided on the deflection electromagnet for correcting the beam trajectory; a plurality of beam position signals detected by the beam position monitor; and a plurality of beam position signals detected by the synchrotron radiation monitor are read. An arithmetic circuit for calculating the amount of excitation of the correction winding based on the output signal, and a plurality of correction winding electrodes controlled by the signal of the arithmetic circuit. It is those with a door.

Further, a deflection electromagnet for an electron beam accelerator according to the present invention comprises a pair of magnetic poles made of a ferromagnetic material, a yoke fixing the magnetic poles and forming a magnetic circuit with the magnetic poles, and a winding wound around the magnetic poles. And a correction winding wound around the magnetic pole and divided into a plurality of pairs to correct the beam trajectory.

[0021]

In the electron beam accelerator according to the present invention having the above configuration, the excitation amount of the correction winding of the bending electromagnet is controlled based on the beam position signals from the beam position monitor and the radiation light monitor. A plurality of correction windings can be excited independently and optimally, and it is possible to perform correction so as to keep the deviation of the beam trajectory in the bending electromagnet small.

Further, in the deflection electromagnet for an electron beam accelerator according to the present invention, the correction winding of the deflection electromagnet is divided into a plurality of pairs and wound around magnetic poles, so that a plurality of correction windings can be independently excited. It is possible to correct the deviation of the beam trajectory in the bending electromagnet so as to keep it small.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a schematic configuration of an embodiment of the electron beam accelerator according to the present invention. This electron beam accelerator has a linear accelerator 21. The linear accelerator 21 generates electrons and accelerates them to tens of millions of electron volts. The electron beam emitted from the linear accelerator 21 passes through a transport tube 22 and further passes through an injector. 23 guides the tube on a design trajectory set at the center of the vacuum duct 24. The vacuum duct 24 is maintained in a high vacuum state in order to prevent the electron beam from losing due to collision with the residual gas.

The electron beam entering the vacuum duct 24 is applied with a magnetic field in a predetermined direction by a bending electromagnet 25 and is deflected in a predetermined direction, while the convergence and divergence of the electron beam are performed by a quadrupole electromagnet 26, and the linear accelerator is used. The electron beam incident from 21 is further accelerated by the high-frequency acceleration cavity 27 to higher energy.

Here, the position of the electron beam in the vacuum duct 24 is monitored by a plurality of beam position monitors 28,
The radiation light port 29 is attached to the vacuum duct 24 by welding or the like in order to extract radiation light radiated in the tangential direction of the deflection curvature of the bending electromagnet 25. A plurality of synchrotron radiation monitors 30 (shown in FIG. 1) for monitoring the position of the center of gravity of synchrotron light are attached to the tip of the synchrotron light port 29.

FIG. 1 is a block diagram showing an embodiment of an electron beam accelerator according to the present invention.

The electron beam accelerator shown in FIG. 1 has two beam position monitors 28 and 28 and two radiation light monitors 3.
These four monitor signals are sent to a beam position detection circuit 31 to detect the beam position. The excitation amount of each correction winding 32 is calculated from the beam position detected by the beam position detection circuit 31 by a correction winding excitation amount calculation device 33, and a signal from the calculation device 33 operates a correction winding power supply 34. The excitation amount of the correction winding 32 is controlled via the correction winding power supply 34. The correction winding 32 is provided on the bending electromagnet 25 and is for correcting the trajectory of the electron beam.

Next, the operation of this embodiment will be described.

In FIG. 1, there are four detectable beam positions including the beam position monitors 28, 28 and the emission light monitors 30, 30, and the deviations of the respective positions from the ideal beam positions are represented by x ₁ , x _2. , X ₃ , x ₄ , the current values i ₁ , i ₂ , i of the four correction windings 32 for setting the deviation to zero.
The relationship between ₃ and i ₄ is

(Equation 1) Here, a _mn (m = 1 to 4, n = 1 to 4) is the correction winding 3
2 is a constant determined by the positional relationship between the beam position monitor 28 and the radiation light monitor 30. Generally, when written in determinant,

(Equation 2) As

A · i = X, and the solution is

I = A ⁻¹ · x (2) In equation (2), A ⁻¹ is the inverse matrix of A. Therefore, by causing the calculation of the expression (2) to be performed by the correction winding excitation amount calculation device 33, the optimum excitation amount of the correction winding 32 can be determined.

That is, in this embodiment, a plurality of correction windings 3
2 can be excited independently and optimally, so that the deviation of the beam trajectory in the bending electromagnet 25 can be corrected to be small.

In the above embodiment, an example in which the number (m) of detectable beam positions and the number (n) of the correction windings 32 are the same has been described. However, the numbers need not always be the same. For example, when m> n, that is, when the number of the correction windings 32 is smaller, the least square method is used. When m <n, that is, when the number of the correction windings is larger, a mathematical method such as the undetermined counting method is used. The optimum excitation amount of the correction winding 32 can be determined by the correction winding excitation amount calculation device 33.

As described above, according to the present embodiment, the correction winding 3 of the bending electromagnet 25 is based on the beam position signals from the beam position monitors 28, 28 and the radiation light monitors 30, 30.
2 is controlled, the plurality of correction windings 32 can be excited independently and optimally.
It is possible to correct so that the deviation of the beam trajectory in the inside is kept small.

FIGS. 3 and 4 show a first embodiment of the bending electromagnet in the electron beam accelerator of FIG. As shown in FIGS. 3 and 4, the bending electromagnet 25 is made of a ferromagnetic material and is disposed above and below the vacuum duct 24.
5 and a yoke 36 forming a magnetic circuit with the yoke 3
6, a plurality of tightening bolts 37 for fixing the magnetic pole 35
And upper and lower excitation windings 38 wound around the magnetic pole 35, and a plurality of upper and lower correction windings 3 for correcting the trajectory of the electron beam.
2 and a plurality of holders 40 and 41 for fixing the excitation winding 38 and the correction winding 32.

Here, the correction winding 32 is housed in a groove 42 formed in the magnetic pole 35, and is wound around the magnetic pole 35.
And the yoke 36 is fixed by tightening with the tightening bolt 37.

Next, the operation of this embodiment will be described.

In FIG. 4, there are four correction windings 32, each of which is connected to the correction winding power supply 34 shown in FIG. Therefore, the four correction windings 32 can be controlled independently,
For example, excitation of the opposite polarity is also possible. Therefore, the deviation of the beam trajectory can be easily corrected, and the deviation of the beam trajectory in the bending electromagnet 25 can be reduced.

FIG. 5 shows a second embodiment of the bending electromagnet in the electron beam accelerator of FIG. 2, and the same parts as those in the first embodiment are denoted by the same reference numerals. This embodiment is an example in which the position of the groove 42 is moved to the surface facing the magnetic pole 35. If the groove 42 is too deep or too large, the magnetic flux generated by the exciting winding 38 disturbs the main deflection magnetic field. Therefore, the groove 42 is small. That is, it is effective when the correction winding 32 is small.

Therefore, as shown in FIG.
2 is moved between the magnetic poles 35, the magnetic flux generated by the correction winding 32 reduces the coupling between the magnetic fields.
Can be easily controlled independently. The other configuration and operation are the same as those of the first embodiment, and the description thereof will be omitted.

FIG. 6 shows a third embodiment of the bending electromagnet in the electron beam accelerator shown in FIG. This embodiment is an example in which the groove 42 is eliminated and the correction winding 32 is attached to the surface facing the magnetic pole 35. Thus, according to this embodiment,
This is applicable when the vacuum duct 24 is small and does not interfere with the correction winding 32. The other configuration and operation are the same as those of the first embodiment, and the description thereof will be omitted.

[0041]

As described above, in the electron beam accelerator according to the present invention, the amount of excitation of the correction winding of the bending electromagnet is controlled based on the beam position signals from the beam position monitor and the radiation light monitor. In the deflection electromagnet for an electron beam accelerator, the deflection winding of the deflection electromagnet is divided into a plurality of pairs and wound around the magnetic poles. The deviation of the beam trajectory in the electromagnet can be kept small.

For this reason, the magnetic pole width of the bending electromagnet can be reduced, and the magnetic flux passing through the yoke becomes smaller almost in proportion to the magnetic pole width, so that the width of the yoke can be reduced, and the size and weight of the bending electromagnet as a whole can be reduced. Can be achieved. Therefore, the capacity of the excitation power supply of the bending electromagnet can be reduced. Further, since the width of the vacuum duct of the bending electromagnet can be reduced, the size of the vacuum duct can be reduced.

According to the electron beam accelerator of the present invention, the beam position of the bending electromagnet can be controlled in real time, so that the stability of the beam and the emitted light is improved.
In addition, since the size and performance can be improved, an inexpensive and high-performance electron beam accelerator can be provided.

Further, according to the deflection electromagnet for an electron beam accelerator according to the present invention, since the size can be reduced, it is possible to provide an inexpensive deflection electromagnet, an excitation power supply for the deflection electromagnet and a vacuum duct. Cost reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an electron beam accelerator according to the present invention.

FIG. 2 is a configuration diagram schematically showing an electron beam accelerator to which the present invention is applied.

FIG. 3 is a sectional view showing a first embodiment of a bending electromagnet in the electron beam accelerator of FIG. 2;

FIG. 4 is a sectional view taken along line AA in FIG. 3;

FIG. 5 is a sectional view showing a second embodiment of the bending electromagnet in the electron beam accelerator of FIG. 2;

FIG. 6 is a sectional view showing a third embodiment of the bending electromagnet in the electron beam accelerator of FIG. 2;

FIG. 7 is a configuration diagram schematically showing a general electron beam accelerator.

FIG. 8 is a sectional view of a beam position monitor.

FIG. 9 is a sectional view of a synchrotron radiation monitor.

FIG. 10 is a sectional view taken along line BB in FIG. 7;

11 is a sectional view of the bending electromagnet shown in FIG.

FIG. 12 is another sectional view of the bending electromagnet shown in FIG. 10;

[Explanation of symbols]

 24 Vacuum Duct 25 Bending Electromagnet 28 Beam Position Monitor 29 Synchrotron Radiation Port 30 Synchrotron Radiation Monitor 31 Beam Position Detection Circuit 32 Correction Winding 33 Correction Winding Excitation Amount Calculation Device 34 Correction Winding Power Supply 35 Magnetic Pole 36 Yoke 37 Tightening Bolt 38 Excitation winding 39 Correction winding 40 Holder 41 Holder

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05H 13/04

Claims (2)

(57) [Claims] 1. An electron beam accelerator for deflecting an electron beam along a beam trajectory in a vacuum duct by a deflecting electromagnet and extracting radiation emitted in a tangential direction of a deflection curvature of the deflection electromagnet from a radiation light port. A plurality of beam position monitors provided in a vacuum duct; a radiation light monitor provided in the radiation light port; a plurality of correction windings provided in the bending electromagnet for correcting the beam trajectory; An arithmetic circuit for reading a plurality of beam position signals detected by the above and a plurality of beam position signals detected by the emission light monitor, and calculating an excitation amount of the correction winding based on the read signals; An electron beam accelerator comprising a plurality of power supplies for correction windings controlled by the signals of (1) and (2). 2. A pair of magnetic poles made of a ferromagnetic material, a yoke that fixes the magnetic poles and forms a magnetic circuit with the magnetic poles, a pair of exciting windings wound around the magnetic poles, and a winding around the magnetic poles. And a correction winding for correcting the beam trajectory by dividing the beam into a plurality of pairs.