JPH0810639B2 - External resonance quadrupole particle accelerator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an RFQ (Radio Frepuency Quadrupole) ion accelerator, and particularly to an external resonance type in which a high-frequency resonance circuit is outside an accelerating tube. Improvement of quadrupole particle accelerator.

[Conventional technology]

A conventional external resonance type quadrupole particle accelerator is disclosed in, for example, JP-A-60
-115199. An example of the structure of the external resonance type quadrupole particle accelerator is shown in FIG. (A) is an elevation view of the apparatus, and (B) is a side view. In the figure
2a, 2b, 2c and 2d are quadrupole rods having a wavy shape in the axial direction. The ion beam is introduced into the central portion surrounded by the quadrupole rods 2a, 2b, 2c, 2d and is accelerated by the high-voltage electric field formed by the quadrupole rods. The ions are accelerated as they progress in the axial direction, and the incident ions are emitted as high-energy ions. In FIG. 2, the high frequency high voltage generated in the resonance circuit composed of the one-turn coil 4 and the variable capacitor 5 is supplied to the quadrupole rod. Reference numeral 3 in the drawing denotes an inductive coupling coil for transmitting the electric power from the high frequency power source to the resonance circuit. Since the resonance frequency changes by changing the capacitance of the resonance circuit, the ion species that can be accelerated and the final acceleration energy can be freely adjusted. The high voltage required to accelerate ions varies depending on the ion species, the desired final energy, the length of the quadrupole rod, etc., but is usually several tens of kV to several hundred kV, which allows Beam acceleration can be achieved with practically sized equipment. As for the variable frequency range, several tens to several hundreds of MHz is sufficient when boron (boron), phosphorus, arsenic ions, etc. are used as the accelerating ion species. In order to efficiently generate such high frequency and high voltage in the resonance circuit, the so-called Q value of the resonance circuit Must be high. In particular, considering the practical size and power supply capacity of an ion beam accelerator, a Q value of 1000 or more is necessary at the least.

[Problems to be solved by the invention]

As the Q value obtained by the resonance circuit of the conventional example shown in FIG. 2, although the Q value that can be used for the accelerator has been obtained, consideration is given to the configuration for achieving the most efficient Q value. There was a problem in obtaining a higher Q value.

Generally, the Q of a resonant circuit for the frequency range of the order of MHz
The value varies greatly depending on how the circuit parts are arranged.

An object of the present invention is to provide a resonance circuit for an external resonance type quadrupole particle accelerator, which comprises a one-turn coil and a variable capacitance capacitor, or an inductance-variable one-turn coil and a capacitor, or a combination of a coil and a capacitor whose inductance and capacitance are both variable. An object of the present invention is to provide a resonant circuit having the above-mentioned arrangement of circuit components efficiently.

[Means for Solving Problems] In order to efficiently accelerate the ion beam by using RFQ, it is essential to realize a high Q value in the resonance circuit. Since the Q value has a strong dependence on the structure and arrangement of circuit parts such as capacitors and inductors, a high Q value optimizes the arrangement of these parts, that is, each of the capacitors and coils that make up the high frequency resonant circuit is This is achieved by being arranged symmetrically with respect to a plane that passes through the center position and is perpendicular to the axis of the acceleration tube.

[Action]

In a resonant circuit configured using LC, the electrical energy stored in the circuit alternates between L and C. Specifically, a current flows between L and C to cause the above movement. The Q value of the circuit changes depending on the line along which this current flows. If the layout of the circuit parts changes, the shape and length of the line of the current flowing between L and C will change,
Since the resistance value of the line changes, the Q value also changes. To reduce the resistance value of the line, the current line may be symmetrical with respect to the circuit configuration.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the one-turn coil 4 is connected to the quadrupole electrode set 2a, 2
It is installed in the middle of b, 2c, 2d and the variable capacitor 5, and the one-turn coil 4 and the variable capacitor 5 are placed in the center of the one-turn coil 4 to improve the symmetry of the arrangement (see plan view (A)) ). In the sectional view (B), the one-turn coil and the quadrupole electrode sets 2a, 2b,
2c and 2d are arranged symmetrically. This is because of the ease of assembling the electrode set. Length 1.3m
The quadrupole electrode rod was attached and the circuit characteristics were measured using a copper one-turn coil with a diameter of 100 mm to 300 mm and a length of 400 to 1300 mm. A vacuum condenser was used as the variable capacity condenser. In the case of the conventional device shown in FIG. 2, the Q value of the resonance circuit composed of the one-turn coil 4 and the vacuum capacitor 5 was about 400 to 500 when the excitation frequency was 20 MHz. On the other hand, in the embodiment of the present invention in which the condenser and the coil are symmetrically arranged as shown in FIG. 1, the same circuit parts were used and a Q value of 1500 or more was obtained. Therefore, the high frequency power required to generate the same high frequency and high voltage in the quadrupole rod (transmitted from the high frequency power source to the resonance circuit through the inductive coupling coil 3) is inversely proportional to the increase in the Q value. I made it small. That is, it is possible to efficiently generate a high frequency and a high voltage with a small amount of power. In general, a high-power high-frequency power source has different power source dimensions depending on the size of the output. Therefore, the reduction of the required power becomes large as it contributes to the downsizing of the power supply, and the external resonance type quadrupole particle accelerator having a practical size is realized as the size of the device including the power supply.

FIG. 3 is a diagram for explaining another embodiment based on the present invention. In this figure, the variable capacitor for changing the frequency is 2
(3) The installation symmetry of the circuit configuration relating to mounting and coil and capacitor is improved. In this case, the capacitors were arranged symmetrically with respect to the center of the coil.

The values of 5 ′ and 5 ″ were changed so that their capacitances were equal to each other, and the resonance frequency was changed.

When the same quadrupole electrode set as described in the embodiment of FIG. 1 was attached and the Q value of the resonance circuit was measured, it was 10 to 30 MH.
A high Q value of 1500 or more was obtained in the excitation frequency region of z.

Although FIG. 3 shows the case where the number of variable capacitors is two, it is clear that if the number of variable capacitors is three, one may be added to the central portion to maintain symmetry. Also, the first
In Fig. 3 and Fig. 3, the same high Q value can be obtained when the positions of the one-turn coil 4 and the vacuum capacitor 5 are interchanged, that is, when the quadrupole electrode set, the capacitor, and the one-turn coil are arranged in this order from the top. It was This is because the same high Q value was obtained because the arrangement symmetry of the condenser and the one-turn coil did not change. When an ion beam of several tens KeV (boron, phosphorus, arsenic ions, etc.) is injected into the external resonance type quadrupole particle accelerator shown in Figs. 1 and 3, a high frequency power of several tens to 100 kW is supplied as a power source. It has been found that it is possible to efficiently accelerate to an ion beam of several MeV or more in the state of being injected from.

In FIGS. 1 and 3, an example in which the inductive coupling coil 3 is installed only on one side is shown. When the Q value becomes high, the influence of this coil on the Q value also appears. It is clear that arranging two coils for inductive coupling symmetrically is also effective for increasing the Q value, and it was confirmed experimentally. First
Although FIGS. 3 and 4 show an example in which the inductive coupling coil 3 is arranged outside the one-turn coil 4, it is also possible to arrange the coils 3 symmetrically inside the one-turn coil 4 for the purpose of the present invention. it is obvious.

〔The invention's effect〕

According to the present invention, a high Q value of the resonance circuit is realized in the external resonance type quadrupole particle accelerator, and it becomes possible to efficiently generate a high voltage for acceleration with a small amount of high frequency power.
This is a major contribution to the miniaturization of equipment, including the power supply, and the high efficiency of acceleration.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention, in which (A) is a plan view, (B) is a side view, and FIG. 2 is a diagram for explaining a conventional example based on the prior art. ) Is a front view, (B) is a side view, and FIG. 3 is a view for explaining another embodiment based on the present invention. 1 ... Vacuum container, 2a, 2b, 2c, 2d ... Quadrupole electrode rod, 3 ...
... Inductive coupling coil, 4 ... One-turn coil, 5, 5 ',
5 ″ ... Variable capacity condenser.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takayoshi Seki, 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Metropolitan Research Laboratory, Hitachi, Ltd. (72) Kensuke Amamiya 1-280, Higashi Koigakubo, Kokubunji, Tokyo Hitachi, Ltd. Central Research Center

Claims (4)

[Claims] 1. An ion beam is accelerated by undulating the mutually facing surfaces of a quadrupole electrode, and feeding the quadrupole electrode with a high-frequency voltage generated by a high-frequency resonance circuit composed of a capacitor and an inductor coil. In the external resonance type quadrupole particle accelerator, the capacitors and the coils forming the high frequency resonance circuit are arranged symmetrically with respect to a plane that passes through the center position of the acceleration tube axis and is perpendicular to the acceleration tube axis. External quadrupole particle accelerator characterized by: 2. The high-frequency resonant circuit comprises a coil of one-turn winding for inductance and a variable capacitance capacitor, and the variable capacitance capacitor is installed at a central portion in the axial direction of the one-turn coil. The external resonance type quadrupole particle accelerator according to claim 1. 3. The high-frequency resonant circuit is configured by connecting a single-turn coil for inductance and a plurality of variable capacitance capacitors in parallel, and the plurality of variable capacitance capacitors of the single-turn coil. The external resonance type quadrupole particle accelerator according to claim 1, wherein the external resonance type quadrupole particle accelerator is arranged symmetrically with respect to an axial center. 4. A coil for inductive coupling for supplying electric power from a power supply to the high-frequency resonance circuit is installed at a position substantially symmetrical with respect to the axial direction of the high-frequency resonance circuit. The external resonance type quadrupole particle accelerator according to claim 1.