JPH11354298A - High frequency type accelerating tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce capacity of a tank for inductors, to secure stable operation, and to improve electric power efficiency in a 3-gap type accelerating tube capable of obtaining excellent accelerating/decelerating efficiency in a wide incident energy range and having excellent versatility in various ion species. SOLUTION: Coil parts 39c, 40c are formed in inductors 39, 40, the total length is shortened, and capacity of a tank 45 is reduced. Mechanical strength becoming a problem at this time is secured by selecting support by insulating plates 46, 47 of the straight line parts 39a, 40a and the ratio of a coil part winding diameter D to a tube diameter (d) as 9 to 13, the center of drift tubes 36, 37 is accurately and stably held on the beam axis, and stable operation is realized. Shunt impedance is enhanced by selecting the D/d in the range to improve electric power efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an ion implantation apparatus,
Ion beam irradiation equipment and PIXE (Proton Induced
X-Ray Emission) and SIMS (Secondary Ion Mass S
The present invention relates to a linear acceleration tube which is preferably implemented in a surface analyzer using an ion beam such as spectrometry, and accelerates ions at a high frequency, and particularly to a three-gap acceleration tube.

[0002]

2. Description of the Related Art Techniques for accelerating ions at a high frequency have been studied for a long time, and are widely used in semiconductor manufacturing processes, medical treatment and the like. Examples of high-frequency accelerators that have been developed for ion acceleration include the Vidley-type, Alvaret-type, and RFQ (high-frequency quadrupole accelerator), which can provide high energy with a relatively short accelerator length. Research has been advanced.

[0003] However, these accelerators have poor energy variability. In particular, in order to apply them to a semiconductor manufacturing process, it is essential that energy can be continuously varied. As a method of solving this, for example, Japanese Patent Publication No. 6-28146, Japanese Patent Publication No. 8-23067,
As disclosed in Japanese Patent Application Laid-Open No. 0-125273 and Japanese Patent Application Laid-Open No. 10-125272, it has been proposed to connect accelerator tubes having a small number of gaps in multiple stages.

For example, the energy gains E2 and E3 for monovalent ions in a two-gap accelerator tube and a three-gap accelerator tube are respectively expressed by the following equations.

E2 = 2V * T * cosφ (1) E3 = 4V * T * cosφ (2) where V is an excitation voltage generated when a high frequency is introduced into the drift tube, and φ is a synchronous phase. Where T is a constant determined by the time for the ions to pass through the accelerating tube and the electrode arrangement, and TTF (Transit Time
Factor), which represents the acceleration / deceleration efficiency with respect to the incident velocity.

FIG. 8 shows a change in the TTF with respect to a change in the incident velocity of ions into the accelerator tube for each gap number.
Shown in In FIG. 8, β ₀ is the optimum value of the ratio β of the incident velocity v of the ions to the light flux c, and the value β ₀ is synchronized with the acceleration timing determined by the gap distance. is there.

As is apparent from FIG. 8, as the number of gaps increases, ions having different incident velocities cannot be efficiently accelerated. On the other hand, the excitation voltage V
Are the same, the energy gain increases as the number of gaps increases. For example, as is apparent from Equations 1 and 2, the energy gain of the 3-gap type is twice as large as that of the 2-gap type.

Therefore, in the case of the ion implantation apparatus or the ion beam irradiation apparatus which accelerates various ions with various energies, a relatively large energy gain can be obtained and a three-gap having a gradual change in TTF can be obtained. The type is considered optimal. For example, for a 5-gap type, the energy gain E5 is 10V * T * cosφ
However, if the change in TTF is large and the ion species and incident energy are different, acceleration may not be possible at all, which is fatal in the ion implantation apparatus and the like.

FIG. 9 is a longitudinal sectional view showing the structure of a typical prior art accelerator tube 1 having three gaps as described above. The ions 4 incident from the holes 3 formed in the acceleration chamber 2 form a gap between the ground electrode 5 connected to the wall surface of the acceleration chamber 2 at the ground potential and the drift tube 6 excited by the high-frequency voltage. The drift tube 6 is accelerated by the first acceleration gap 7, and its phase changes by 180 ° while passing through the drift tube 6. , And accelerated in a third acceleration gap 11 between the drift tube 8 and the ground electrode 10 connected to the wall of the acceleration chamber 2, and emitted from the hole 12. Is done.

Drift tubes 6 and 8 have tank 13
Resonance inductor poles 14 erected from the bottom of
15 are connected. One of the inductor poles 14 is connected to a tank 13 via a coupler 17 from a coaxial tube or cable (a coaxial cable in the example of FIG. 9) indicated by reference numeral 16.
The high-frequency power introduced into the power supply is supplied to the inductor pole 14 by electromagnetic coupling or capacitive coupling (capacitive coupling in the example of FIG. 9) between the coupler 17 and the inductor pole 14. A tuner 18 having the same configuration as the coupler 17 faces the other inductor pole 15. By adjusting the capacitance between the tuner 18 and the inductor pole 15, the reflected power is minimized. The high-frequency power is introduced under conditions.

FIG. 10 is a partially cutaway perspective view of a tank 22 for explaining the structure of another prior art acceleration tube 21 having three gaps. This accelerating tube 21 is a Nuclear
Instruments and Methods in Physies Research 224
(1984), paragraphs 17 to 26. In the acceleration tube 21, portions corresponding to the above-described acceleration tube 1 are denoted by the same reference numerals, and description thereof will be omitted. In this acceleration tube 21, the inductors 23 and 24 for the drift tubes 6 and 8 are formed in a spiral shape.

[0012]

In the acceleration tubes 1 and 21 constructed as described above, the inductor pole 1
The inductors 4 and 15 and the inductors 23 and 24 are called １ ／ wavelength resonators and are formed to have a length near １ ／ of the resonance wavelength λ of the acceleration tube. Therefore, for example, if the resonance frequency is 10
In the case of 0 (MHz), the length is 75 cm. on the other hand,
When accelerating relatively heavy ions such as B, P, and As used in the ion implantation apparatus, the resonance frequency of the accelerating tube is usually set to 10 to 50 (MHz).

Therefore, the resonance frequency is set to, for example, 10
(MHz), the inductor poles 14, 15
And the lengths of the inductors 23 and 24 are as large as 7.5 (m). In this case, with a structure like the acceleration tube 1, the height of the tank 13 becomes close to 10 (m), which is not practical.

In this respect, in the accelerating tube 21, the number of turns of the inductors 23 and 24 is increased so that the tank 22
Capacity can be reduced. However, if the number of turns is increased, the rigidity of the inductors 23 and 24 becomes insufficient. On the other hand, since the inductors 23 and 24 consume a large amount of high-frequency power to be injected, the inductors 23 and 24 have a double-cylinder structure, and a large flow rate of several to several tens (liter / minute) flows through the cylinder. ing. Therefore, if the number of turns is large, the inductor 2 supporting the drift tubes 6 and 8 can be used.
The mechanical strength of the drift tubes 3 and 24 is insufficient, and the drift tubes 6 and 8 cannot be accurately positioned on the beam advancing axis. In some cases, vibration occurs and the resonance frequency can be kept constant. And the stable operation of the acceleration tube 21 is hindered.

If the number of turns of the inductors 23 and 24 is increased, a sufficient working space cannot be secured near the mounting portion when the drift tubes 6 and 8 are fixed to the inductors 23 and 24. There is also a problem that is bad. From the above, in the accelerating tube 21, mechanical accuracy and strength are required for the inductors 23 and 24, so that the number of turns of the inductors 23 and 24 cannot be increased so much and the capacity of the tank 22 can be reduced. Can not.

Further, a parameter for evaluating the excitation voltage, called a shunt impedance R ₀ , is defined for the accelerator tube. Using this parameter, the total excitation voltage of the 3-gap accelerator tube is expressed by the following equation. expressed.

4V = {2 * P * R ₀ } ^1/2 (3) where P represents input power.

Therefore, the shunt impedance R ₀
Is a parameter for determining the energy gain of the accelerating tube. As the shunt impedance R ₀ increases, the energy efficiency per accelerating tube, that is, the power gain per input power can be increased. The shunt impedance R ₀ is determined by the shape of the inductor, the position in the tank, and the like, and is desirably increased to improve power efficiency.

An object of the present invention is to provide a high-frequency accelerating tube capable of reducing the tank capacity of the inductor and improving the stable operation and power efficiency.

[0020]

A high-frequency accelerator according to the present invention has three acceleration gaps in an acceleration chamber, and a resonance inductor associated with each of two drift tubes constituting the acceleration gap is a tank. In the high-frequency type acceleration tube provided in the inside, each of the inductors is composed of a tube body through which cooling water can pass, and is connected to a first straight portion standing upright from a tank bottom surface and the first straight portion. A coil portion, and a second linear portion that connects between the coil portion and the drift tube, wherein the second linear portion is held and fixed to an inner wall of the tank by an insulating member; The ratio between the winding diameter and the outer diameter of the tube is formed in the range of 9 to 13.

According to the above configuration, a relatively large energy gain can be obtained and a relatively gentle TTF
In a three-gap high-frequency accelerator capable of coping with various ion species and incident energies by changing, in order to accelerate relatively heavy ions, the resonance inductor becomes longer due to its lower resonance frequency. A coil section is formed to reduce the tank capacity, and at the time of connection between the drift tube and the inductor, a large work space is secured around the drift tube in order to improve the assembling workability.

At this time, in the inductor, a first linear portion connected to the coil portion is held and fixed to the tank bottom surface, and a second linear portion connecting between the coil portion and the drift tube is formed by an insulating member. The ratio of the winding diameter of the coil portion to the outer diameter of the pipe is 9
To 13 to secure necessary mechanical strength and cooling capacity. As a result, a stable operation and an improvement in power efficiency can be achieved without causing a shift in the resonance frequency.

Further, since the ratio between the winding diameter of the coil portion of the inductor and the outer diameter of the tube is formed in the range of 9 to 13, the shunt impedance _R0 can be set relatively high. In addition, power efficiency can be improved.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The following is a description based on FIGS. 1 to 6.

FIG. 1 shows an acceleration tube 31 according to an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view showing the structure of FIG. 1, and FIG.
It is sectional drawing seen from -A. The acceleration tube 31 is a linear acceleration tube having three acceleration gaps 32, 33, and 34.
, A ground electrode 35, a drift tube 36,
The acceleration chamber 41 includes a drift tube 37 and a ground electrode 38, and a tank 45 includes resonance inductors 39 and 40.

In the acceleration tube 31, the inductors 39 and 40 connected to the two drift tubes 36 and 37 to which the high-frequency voltage is applied become L, and the acceleration gaps 32, 33 and 34 and the distributed capacitance of each part become C. Thus, a three-dimensional resonance circuit is formed.

The acceleration chamber 41 and the tank 45 are made of copper,
It is formed of a highly conductive material such as aluminum, silver, or a non-magnetic material obtained by plating them. However, in the case of the plated material, it goes without saying that the plating thickness is sufficiently thicker than the skin thickness determined by the material and the frequency. The remaining portions having relatively small power loss other than the inductors 39 and 40 described later are also formed of such a material.

The ions 43 incident from the holes 42 of the acceleration chamber 41 are supplied to the first acceleration gap 32 between the ground electrode 35 connected to the wall surface of the acceleration chamber 41 at the ground potential and the drift tube 36, Drift tubes 36, 37
Between the second acceleration gap 33 and the drift tube 37
After being sequentially accelerated by the third acceleration gap 34 between the ground electrode 38 and the ground electrode 38 connected to the wall surface of the acceleration chamber 41, the light is emitted from the hole 44. The interior of the acceleration chamber 41 is maintained at a high vacuum in order to reduce the beam loss of the ions 43 and prevent discharge.

The drift tubes 36 and 37 are connected to linear portions 39a and 40a at one end of resonance inductors 39 and 40, respectively.
The straight portions 39b and 40b on the other end side of the tanks 9 and 40 are
5 is connected to the bottom surface. These inductors 39 and 40
The distance L1 on the bottom side of the tank 45 is selected such that the shunt impedance _R0 does not decrease, and the distance L2 on the drift tubes 36, 37 side is the distance L3 between the acceleration gaps 32, 33, 34. And the distances L1 and L2 do not necessarily need to be equal.

The portions of the inductors 39 and 40 other than the linear portions 39a and 39b; 40a and 40b at both ends are wound in a coil shape to form coil portions 39c and 40c, and the λ / 4 resonator is formed. The length of the coil portions 39c and 40c is significantly shorter than the required inductor length, and the height H of the tank 45 is sufficiently small. The winding directions of the two coil portions 39c and 40c may be either the same direction or different directions. The inductors 39 and 40 have a double-cylinder structure as described in detail later, and a coolant supplied from outside such as pure water or Freon is circulated in the cylinder.

The linear portions 39a and 40a on the free ends of the inductors 39 and 40 are held and fixed to the inner wall of the tank 45 by insulating plates 46 and 47, respectively.
As a result, the centers of the drift tubes 36 and 37 are accurately positioned on the beam axis, and are stably held. Since the insulating plates 46 and 47 are arranged at a place where the high-frequency electric field is high, heat generation, that is, power loss occurs. Therefore, in order to suppress this, it is formed from a material having a sufficiently low dielectric loss tangent, for example, high-purity alumina or high-frequency ceramic.

The introduction of high-frequency power may be either electromagnetic coupling or capacitive coupling. FIG. 1 shows an example of capacitive coupling. The high-frequency power is introduced into the tank 45 from a high-frequency power supply by a coaxial tube or cable (coaxial cable in the example of FIG. 1) indicated by reference numeral 48 and having a characteristic impedance of, for example, 50Ω, and is provided in a loop type or plate type (FIG. In the example of (1), a plate-type coupler 49 is provided. The coupler 49 faces the linear portion 39a of the inductor 39, and by adjusting the capacitance between the coupler 49 and the inductor 39, the coaxial cable 48 and the inductor 39 are impedance-coupled and the reflected power is minimized. The high-frequency power is introduced under conditions.

When the high-frequency power is introduced, as shown in FIG. 2, the inductors 39 and 40 are excited by high-frequency excitation voltages V of opposite polarities, that is, 180 degrees out of phase, and an acceleration electric field E is generated. . The principle of acceleration is described in, for example, paragraphs [0009] to [0018] of JP-A-10-125272. When the acceleration tube 31 is excited, heat is generated inside and the resonance frequency is shifted. To compensate for this, the loop-type or plate-type (plate-type in the example of FIG.
Is provided facing the linear portion 40a.

In the acceleration tube 31 configured as described above, according to the present invention, the inductors 39 and 40 are formed as described in detail below.

First, consider the shunt impedance R ₀ . In order to increase the energy gain of the accelerator tube as much as possible, it is necessary to increase the shunt impedance _R0 as much as possible as described above. This shunt impedance R ₀ can be represented by R ₀ = Q ₀ * (R ₀ / Q ₀ ) (4).

Here, Q ₀ is called an unloaded Q value, and increases as the power loss in the acceleration tube decreases. Also, (R ₀
/ Q ₀ ) is the characteristic impedance of the accelerator, which is determined by the structure of the accelerator. The Q value can be improved by using a material having good conductivity as described above or an insulating member having a small dielectric loss tangent. Further, in general, when a conductive material blocks a magnetic field component generated in an acceleration tube, a current flows in that portion, and the Q value is reduced. On the other hand, the above (R ₀ / Q ₀ )
Is substantially determined by the shape of the inductor. Therefore, the present inventor has performed a three-dimensional dynamic electromagnetic field analysis, and based on the analysis result, has determined the optimum shapes of the inductors 39 and 40.

FIG. 3 shows a magnetic field distribution around the inductor by the three-dimensional dynamic electromagnetic field analysis. In this example, the winding directions of the coil portions 39c and 40c of the inductors 39 and 40 are the same, and the coupler 49, the tuner 50, and the insulating plates 46 and 47 are omitted.

As is apparent from FIG. 3, since the inductors 39 and 40 are excited by excitation voltages V of opposite polarities, the flow of the magnetic field is controlled by the coil portions 39c and 40c as indicated by reference numeral 60. It has a large loop shape that runs through the inside. If the winding directions of the inductors 39 and 40 are opposite to each other, the flow of the magnetic field becomes a small loop shape that goes from the inner circumference to the outer circumference of the coil sections 39c and 40c, respectively.

The coil portions 39c and 40c are
When approaching the bottom side of the tank, the magnetic field loop comes into contact with the bottom of the tank 45, and when approaching the acceleration chamber 41 side, when the acceleration chamber 41 is relatively small compared to the tank 45, The magnetic field loop comes into contact with the upper surface of the tank 45. As a result, when the magnetic field is cut off, the Q value decreases as described above, and the shunt impedance R ₀ decreases. For example, the shunt impedance R ₀ is 11.35 in the structure of FIGS.
(MΩ). However, when a conductive plate is inserted between the inductors 39 and 40 to cut off the magnetic field loop 60, 10.
77 (MΩ), which is about 5 (%) lower.

Therefore, the coil portions 39c, 40c are supported by the linear portions 39a, 39b; 40a, 40b, respectively, within a range where the tank height H can be made as low as possible. They are arranged so that the disturbance of the magnetic field loop 60 is minimized.

On the other hand, changes in the shunt impedance R ₀ when the tube diameter d of the inductors 39 and 40 and the winding diameter D of the inductors 39 and 40 are changed are shown in FIGS. 4 (a) and 5 (a), respectively. ). 4 and 5 are examples in which the resonance frequency is set to 33 (MHz). However, the winding diameter D is equal to the coil portions 39c, 4
0c is the average diameter, which is the diameter at the center of the tube.

In the example of FIG. 4, the inner diameter L10 of the tank 45 is 350 (mm), and the distance L1 between the inductors is 150.
(Mm), and the winding diameter D is 80 (mm).
FIG. 4B shows a change in the ratio of the shunt impedance R _{0 to} the peak value when the ratio between the winding diameter D and the tube diameter d is changed by changing the tube diameter d. FIG. 4 shows that the shunt impedance R ₀ is the highest when the tube diameter d is 8 (mm), and the allowable value is set to 9 for the peak value, for example.
If 0 (%) is set, it is understood that D / d may be set in the range of 9 to 13.

In the example of FIG. 5, the tank inner diameter L10
Is 500 (mm), and the distance L1 between the inductors is 250
(Mm), and the tube diameter d is 10 (mm). FIG. 5B shows a change in the ratio of the shunt impedance R _{0 to} the peak value when D / d is changed. From FIG. 5, the winding diameter D is 10
0 (mm) indicates that the shunt impedance R ₀ is the highest, and with respect to the peak value,
Assuming that the allowable value is 90 (%), it is understood that D / d should be 8 or more.

As is apparent from FIGS. 4 and 5,
Even when the tank inner diameter L10 and the distance L1 between the inductors are changed, D / d when the shunt impedance _R0 is maximized becomes substantially the same. For example, if the allowable value is 90 (%) of the peak value, 9 to Within the range of 13, a shunt impedance within the allowable value can be obtained.

Next, the workability of the inductors 39 and 40 will be discussed. These inductors 39, 40
It is formed by spirally winding a metal tube having good conductivity, such as gold, silver, or copper, or a tube having a surface plated with such a metal. These inductors 39,
The total length of 40 is determined from the resonance frequency (1 / λ), so the number of turns is not necessarily an integer. However, the mounting positions of the inductors 39 and 40 are mechanically determined.
At least one of the start end and the end (both in FIGS. 1 and 3) of the coil portion 0c is the winding center, that is, the coil portion 3
It is necessary to return to the axes 9c and 40c. Therefore, the bending radius of the starting portion or the ending portion that returns to the center becomes the smallest.

Usually, the bending radius of a metal tube is determined by the following equation:
Then, the minimum is R. However, since the inductors 39 and 40 are formed by annealing a material, if formed with such a small bending radius, the bent portions will be crushed. Therefore, the bending radius is required to be at least 1.5R or more for actual production.

For example, as shown in FIGS. 4 and 5, the coil portions 39c, 4 when D = 100 (mm) and d = 12 (mm), that is, when D / d ≒ 8.3.
The shape of 0c is shown in FIG. A portion other than the start end or the end is wound at a predetermined pitch with a bending radius R = 44 (mm). On the other hand, the start or end portion is R = 19 (mm), and the tube diameter d =
At about 1.5 times of 12 (mm), the bending radius approaches the limit.

In such a case, three-dimensional bending is performed by adding the axial directions of the inductors 39 and 40 (the axial directions of the coil portions 39c and 40c and the longitudinal directions of the linear portions 39a and 39b; 40a and 40b). Thereby, the bending radius R can be increased. However, the manufacturing becomes complicated and the manufacturing cost increases. For this reason, D / d = 9 or more is desirable from the viewpoint of workability.

Next, the cooling efficiency will be discussed. Most of the power supplied to the accelerating tube, except for accelerating the beam, is consumed by these inductors 39 and 40, and generates heat. In a typical ion implantation apparatus used for manufacturing semiconductors, the input power reaches several (kW), and therefore, without cooling, the inductors 39 and 40 are instantaneously melted and damaged. If the cooling is insufficient, a shift in the resonance frequency occurs due to the heat generated by the inductors 39 and 40. If the compensation frequency exceeds the compensation range of the tuner 50, the accelerator tube 31 cannot be operated stably. I will.

Therefore, it is desirable that the temperature change of the inductors 39 and 40 be about 10 (° C.) or less when the maximum power is applied. For this purpose, the high frequency power 1 (k
W), the cooling water flow rate is required to be 1 (liter / minute) or more.

On the other hand, the inductors 39 and 40 have a double cylindrical structure as described above, and it is necessary to form a reciprocating cooling water channel in the tube having the tube diameter d. Therefore, for example, the resonance frequency is 33 (MHz), the input power is 5 (kW), and thus the two inductors 39, 40
Is 2.5 (kW), and D = 10
0 (mm), d = 8 (mm), that is, D / d = 12.
When it is set to 5, the outer diameter of the outer cylinder is 8 (mm), for example, the thickness is 0.5 (mm), and the outer diameter of the inner cylinder is 5 (m).
m) and a wall thickness of 0.5 (mm), a cooling water flow rate of 2.5 (liter / min) is required, and in this case, the water pressure is 5 (kg / cm ² ).

This flow rate is the limit value of the withstand pressure of the outer cylinder with respect to the stable operation of the accelerator tube and the water pressure. As a result, the acceleration voltage is reduced. Therefore, from the viewpoint of cooling efficiency, it is desirable that D / d = 13 or less.

Lastly, in order to accurately and stably position the centers of the drift tubes 36 and 37 on the beam axis, it is necessary to suppress vibrations caused by the flow of the cooling water and the like. The smaller the D / d, the better.

Table 1 summarizes the above examination results.
By setting D / d to 9 to 13,
While ensuring the required cooling efficiency and mechanical strength, the shunt impedance _R0 can be increased, the power efficiency can be increased, and good workability can be obtained.

[0055]

[Table 1]

According to the results of the three-dimensional dynamic electromagnetic field analysis, the shunt impedance R ₀ can be improved in proportion to other parameters, for example, the tank inner diameter L10 according to the results of the three-dimensional dynamic electromagnetic field analysis. It has been confirmed that it is determined according to the shunt impedance R ₀ required for the accelerator tube, the installation space, the exhaust capacity of the vacuum pump, and the like.

The distance L1 between the inductors is determined by the remaining tubes in the accelerator 31, such as the drift tubes 36 and 37, the ground electrodes 35 and 38, the coupler 49 and the tuner 50, and the relationship with the discharge limit distance. You. According to the result of the conducted magnetic field analysis, the distance L between the inductors
Even if 1 is changed, the shunt impedance R ₀ cannot be significantly improved. However, if it is too small, the capacitance between the inductors 39 and 40 increases, and the shunt impedance R ₀ decreases. Therefore, the distance L1 may be at least 1.5 times the winding diameter D.

Furthermore, the characteristic impedance (R ₀ / Q0) of the accelerator tube generally increases as C decreases and L increases. Therefore, even with the same inductance length, it is apparent that the smaller the winding pitch of the coil portions 39c and 40c, that is, the smaller the height of the coil portions 39c and 40c, the higher the shunt impedance _R0. .

The shape of the tank 45 may be any of a cylindrical shape and a rectangular tube shape, and the arrangement direction of the inductors 39 and 40 is, as shown by the acceleration tube 71 in FIG. The directions may intersect.

[0060]

As described above, the high-frequency accelerator according to the present invention can obtain a relatively large energy gain and can respond to various ion species and incident energies with a relatively gentle TTF change. In the three-gap high-frequency accelerator tube, a coil portion is formed in a resonance inductor that is elongated corresponding to relatively heavy ions.

Therefore, the capacity of the tank can be reduced, and a large work space can be secured around the drift tube when connecting the drift tube and the inductor, so that the assembling workability can be improved. .

At this time, the first linear portion connected to the coil portion of the inductor is held and fixed to the bottom surface of the tank, and the second linear portion connecting the coil portion and the drift tube is formed of an insulating member. And the ratio of the winding diameter of the coil portion to the outer diameter of the tube is 9 to 9
13, ensuring the required mechanical strength and cooling capacity.

Therefore, a stable operation and an improvement in power efficiency can be achieved without causing a shift in the resonance frequency.

Further, by forming the ratio between the winding diameter of the coil portion of the inductor and the outer diameter of the tube in the range of 9 to 13, the shunt impedance R ₀ can be set relatively high, and this also enables In addition, power efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a structure of an acceleration tube according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a longitudinal sectional view showing a dynamic electromagnetic field analysis result in the accelerator tube shown in FIGS. 1 and 2.

FIG. 4 is a graph showing a change in shunt impedance when the tube diameter of the inductor in the acceleration tube shown in FIG. 1 is changed.

FIG. 5 is a graph showing a change in shunt impedance when the winding diameter of the inductor in the acceleration tube shown in FIG. 1 is changed.

FIG. 6 is a view for explaining the workability of the inductor.

FIG. 7 is a perspective view showing a structure of an acceleration tube according to another embodiment of the present invention.

FIG. 8 is a graph showing a change in acceleration / deceleration efficiency with respect to a change in the incident velocity of ions into the accelerator tube at various gap numbers.

FIG. 9 is a longitudinal sectional view showing the structure of a typical prior art accelerator tube.

FIG. 10 is a partially cutaway perspective view for explaining a structure of another conventional acceleration tube.

[Explanation of symbols]

 31, 71 Accelerator tube 32, 33, 34 Acceleration gap 35, 38 Ground electrode 36, 37 Drift tube 39, 40 Inductor 39a, 40a Linear part (second linear part) 39b, 40b Linear part (first linear part) 39c, 40c Coil part 41 Acceleration part 43 Ion 45 Tank 46, 47 Insulating plate 48 Coaxial cable 49 Coupling device 50 Tuner D Winding diameter d Tube diameter (tube outer diameter)

Claims (1)

[Claims] 1. A high-frequency accelerating tube having three acceleration gaps in an acceleration chamber, and resonance inductors respectively associated with two drift tubes constituting the acceleration gap are provided in a tank. A first straight portion, which is formed of a pipe body through which cooling water can pass, and is provided upright from the tank bottom surface, a coil portion connected to the first straight portion, and a portion between the coil portion and the drift tube. And a second linear portion that connects and fixes the coil portion, wherein the second linear portion is held and fixed to an inner wall of the tank by an insulating member, and a ratio of a winding diameter of the coil portion to an outer diameter of the tube is 9 to 10. 1
3. A high-frequency accelerating tube which is formed in 3.