JP2000268999A - Cavity resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrahigh vacuum cavity resonator of simple configuration and to reduce the operating cost. SOLUTION: This cavity resonator is provided with structure materials 22B and 22L having a thickness resistant to an atmospheric pressure, a thin conductor plate 30 disposed along the inside thereof in the metal touch condition an auxiliary evacuating part 40 formed between the structure materials and the conductor plate 30 and an ultrahigh vacuum part 50 surrounded by the conductor plate 30. Thereby, the ultrahigh vacuum part 50 and the auxiliary evacuating part 40 are evacuated by different evacuating pumps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cavity resonator, and particularly to an ion accelerator, an electron beam accelerator, etc.
Suitable for use when generating high voltage acceleration voltage,
The present invention relates to a low-cost cavity resonator having a simple structure, strength enough to withstand atmospheric pressure, and capable of maintaining an ultra-high vacuum state.

[0002]

2. Description of the Related Art When generating high-frequency and high-voltage accelerating voltages with an ion accelerator, an electron beam accelerator, or the like, a cavity resonator is usually used. In such a case, the conductor in the resonator is usually made of a water-cooled plate of oxygen-free copper. On the other hand, when accelerating particles pass through the cavity resonator,
In particular, when multiply charged ions such as heavy ions are accelerated, they must be in an ultra-high vacuum state of about 10 ⁻⁶ Pa in order to maintain the transmittance (survival rate). Then, the cavity resonator in which the inside is in a vacuum state must have, of course, a strength that can withstand the atmospheric pressure.

Generally, when manufacturing such an ultra-high vacuum cavity resonator, a stainless steel material is used as the outermost structural material from the viewpoint of strength and magnetic permeability. The inner conductor is a plate of oxygen-free copper, which is cooled by cooling water.

Therefore, conventionally, in order to apply to an ultra-high vacuum, as shown in FIG.
There was no other choice but to use the cladding material 10 of 0S. In the drawing, 10W is a cooling water passage formed in, for example, oxygen-free copper 10C.

[0005] Unless an ultra-high vacuum is used, as shown in FIG. 2, a stainless steel plate 12 provided on the air side and a perforated copper plate 16 provided with a space inside and having a hole 16h provided therein. Alternatively, it is also conceivable to form a double structure with a mesh-shaped copper plate, and to provide a copper tube 18 for passing cooling water in the space 14 between the stainless steel plate 12 and the copper plate 16.

[0006]

However, in the configuration as shown in FIG. 2, since there is much outgas in the space 14 between the copper plate 16 and the stainless steel plate 12 and the conductance is small, the inside of the cavity inside the copper plate 16 is small. However, it is difficult to maintain the vacuum in an ultra-high vacuum, and a large amount of evacuation pumps is required, so that the cost is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has a simple structure, a cavity resonance strength capable of withstanding atmospheric pressure, and capable of maintaining an ultra-high vacuum state. It is an object to provide a vessel.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a cavity resonator comprising a structural member having a thickness capable of withstanding atmospheric pressure, a thin conductive plate disposed in a metal touch state along the inside thereof, and An auxiliary evacuation unit formed between the material and the conductor plate and an ultra-high vacuum unit surrounded by the conductor plate are configured, and the ultra-high vacuum unit and the auxiliary vacuum unit are evacuated by different evacuation pumps. This has solved the above problems.

Further, the auxiliary exhaust unit is provided with 10 ^-3 to 10 ^-5 P
a normal high vacuum of about a, the ultra-high vacuum unit, ^10-6
It is an ultra-high vacuum of Pa or less.

First, the feasibility of the present invention will be discussed.
As shown in FIG. 3, the cavity resonator 20 is divided into an ultra-high vacuum section 50 and an auxiliary exhaust section 40, and a vacuum calculation model is considered as a model as shown in FIG.

That is, the outermost structural materials (for example, the stainless steel body 22B and the stainless steel lid 22L) have a thickness enough to withstand the atmospheric pressure, and a relatively thin plate (for example, the copper plate 30) is used as the conductive plate. Used. The space between the structural material and the conductor plate is referred to as an auxiliary exhaust unit 40, and the inside of the cavity surrounded by the conductor (copper plate 30) is referred to as an ultra-high vacuum unit 50.

Now, as shown on the left side of FIG.
0 and the auxiliary exhaust unit 40 have a certain conductance C (m ³ /
The outgas amount and the pressure when it is considered that the single exhaust was performed before the connection in s) are respectively represented by Q10 (Pa · m ³ / s),
P10 (Pa), Q20 (Pa · m 3 / s), P20 (Pa)
As shown on the right side of FIG. 4, the outgas amount and the pressure after the connection with the conductance C are Q1 (Pa ·
m ³ / s), P1 (Pa), Q2 (Pa · m ³ / s), P2
In the case of (Pa), the following equation holds in an equilibrium state after connection.

Q1 = Q10 + C · (P2−P1) (1) Q2 = Q20 + C · (P1−P2) (2)

Assuming that the outgas amount and the ultimate pressure are proportional in each exhaust chamber, the following equations (3) and (4) can be obtained by solving equations (1) and (2).

K1 = P1 / P10 = (Q10 · Q20 + C · P20 · Q10 + C · P20 · Q20) / (Q10 · Q20 + C · P20 · Q10 + C · P10 · Q20) (3) K2 = P2 / P20 = (Q20 + C · P10)・ K1) / (Q20 + C ・ P20)… (4)

Therefore, if Q10, P10, Q20, and P20 are known, the relationship between C and K1 is evaluated, and the ultra-high vacuum is maintained at a certain conductance C while maintaining the target ultimate pressure of the ultra-high vacuum section 50. The unit 50 and the auxiliary exhaust unit 40 can be connected.

The ultra-high vacuum section 50 and the auxiliary exhaust section 4 are controlled so that the permissible conductance C obtained in this manner is not more than C.
By allowing a gap between zero, an ultrahigh-vacuum cavity resonator having a simple metal-touch double structure, which does not require an elastomer or a metal seal mechanism, can be manufactured with an evacuation pump equivalent to that of a single evacuation.

[0018]

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

In this embodiment, as shown in FIG. 3, a hollow resonator 20 is made up of a stainless steel box-shaped body 22B and a lid 22L, which are structural members having a thickness capable of withstanding the atmospheric pressure.
2B and a thin copper plate 30 disposed in a metal touch state by directly screwing to the pedestal 24 made of, for example, stainless steel along the inside of the lid 22L and the body 22B.
Or, the auxiliary exhaust unit 4 formed between the lid 22L and the copper plate 30
0, a copper pipe 32 for cooling water disposed on the copper plate 30 side of the auxiliary exhaust unit 40, and an ultra-high vacuum unit 50 surrounded by the copper plate 30. Is evacuated by an auxiliary evacuation unit exhaust pump composed of, for example, a turbo molecular pump, and the ultrahigh vacuum unit 50 is evacuated by an ultrahigh vacuum unit exhaust pump composed of, for example, a cryopump.

In this embodiment, as shown on the left side of FIG. 4, when there is no leakage between the ultrahigh vacuum section 50 and the auxiliary exhaust section 40, the outgas amounts Q10 and Q20 of each exhaust section and the ultimate pressure P10, P20 is as follows.

Q10 = 1.0 × 10 ⁻⁵ (Pa · m ³ / s) Q20 = 5.0 × 10 ⁻⁵ (Pa · m ³ / s) P10 = 1.0 × 10 ⁻⁶ (Pa) P20 = 5.0 × 10 ^-4 (Pa)

These are calculated values for each exhaust chamber alone. The ultrahigh vacuum section 50 uses two 10,000 (liter / s) class cryopumps, and the auxiliary exhaust section 40
This is a result of using two turbo molecular pumps of 00 (liter / s).

Under these conditions, as shown on the right side of FIG.
Conductance C (m ³ /
FIG. 5 shows the calculation result of the relationship between s) and the pressure P1 of the ultrahigh vacuum section 50. As is clear from the figure, the allowable conductance C for maintaining the pressure P1 in the ultrahigh vacuum section 50 at an ultrahigh vacuum of 2 × 10 ⁻⁶ Pa or less is 2 × 10 ⁻² (m ³ / s) or less. You can see that there is.

On the other hand, the main part spatially connecting the ultrahigh vacuum section 50 and the auxiliary exhaust section 40 is considered to be a joint of the copper plate 30. FIG. 6 shows a calculation result of the relationship between the gap b and the conductance C at the joint of the copper plates 30. Here, it is assumed that the total length a of the joint of the copper plate 30 is 50 m and the thickness l of the gap is 5 mm.

The conductance C is 2 × 10 ^-2 (m ³ /
s) In order to be less than or equal to, the allowable value of the gap is 0.063 m
It can be seen that it should be m or less. This gap is the copper plate 3
0 is a size that can be easily realized by fixing the same with a simple structure as shown in FIG.

In this way, it is possible to manufacture an ultra-high vacuum cavity resonator having a simple metal touch double structure without an elastomer or a metal seal mechanism.

In the above-described embodiment, stainless steel is used as the structural material and a copper plate is used as the conductive plate. However, the material of the structural material and the conductive plate is not limited to this.

[0028]

According to the present invention, an ultra-high vacuum cavity resonator can be manufactured with a simple double metal touch structure without using an expensive clad material or providing an elastomer or a metal seal mechanism. The cavity resonator can be configured at low cost. Furthermore, since there is no need to use a large amount of exhaust pump, the operating cost is low.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a wall of a conventional cavity resonator using a stainless-copper clad material.

FIG. 2 is a cross-sectional view showing a configuration of a wall of a conventional cavity resonator using a perforated copper plate.

FIG. 3 is a sectional view showing the configuration of the embodiment of the present invention.

FIG. 4 is a conceptual diagram of working exhaust for explaining the principle of the present invention.

FIG. 5 is a diagram showing calculation results of conductance and pressure of an ultra-high vacuum section when each exhaust section is connected.

FIG. 6 is a table showing a calculation result of a relationship between a gap and a conductance of a joint of a copper plate.

[Explanation of symbols]

 Reference Signs List 20 cavity resonator 22B stainless steel body 22L stainless steel lid 24 pedestal 30 copper plate 32 copper tube 40 auxiliary exhaust unit 50 ultra-high vacuum unit

Claims (2)

[Claims] 1. A structural member having a thickness capable of withstanding atmospheric pressure, a thin conductive plate disposed in a metal touch state along the inside thereof, an auxiliary exhaust portion formed between the structural member and the conductive plate, A cavity resonator comprising: an ultra-high vacuum section surrounded by the conductor plate; wherein the ultra-high vacuum section and the auxiliary exhaust section are evacuated by different exhaust pumps. 2. The apparatus according to claim 1, wherein the auxiliary exhaust unit is configured to
A cavity resonator characterized by a normal high vacuum of about 0 ^-3 to 10 ^-5 Pa and an ultra-high vacuum of the ultra-high vacuum section of 10 ^-6 Pa or less.