JPS60115199A - Quadruple pole particle accelerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to RF Q (Radio Frequency)
The present invention relates to quadrupole ion accelerators, and particularly to improvements to quadruple seed particle accelerators that efficiently accelerate various ions to arbitrary energies.

[Background of the invention]

The structure of a conventional RPQ ion accelerator is shown in FIG. The facing surfaces of the quadrupole electrodes 1, 2, 3.4 are unevenly undulating, and this is shown in the second vertical and horizontal cross sections.
It is a diagram. Figure 2(a) shows a vertical section, Figure 2(b)
) indicates a horizontal section. A high frequency is applied to these electrodes, and when electrodes 1 and 3 are ■, electrodes 2 and 4 are θ, and when electrodes 1 and 3 are O, electrodes 2 and 4 are ■. Further, as can be seen from FIG. 2, the phase of the concave and convex portions of the electrode 1.3 and the electrodes 2 and 4 are shifted by 180 degrees, and therefore, for example, the phase of the concave and convex portions of the electrode 1.3 is shifted by 180°.

When 3 is ■ and electrode 2.4 is e, as shown in Figure 2,
An axial electric field is generated on the central axis. Arrows 6.7.8 indicate the direction of the electric field. When the polarity of the voltage applied to the electrodes is reversed, the direction of the electric field in FIG. 2 is also reversed. Now, the second
Ions entering this quadrupole electric field from the left side of the figure are
Dingho, at such a speed that he is constantly receiving an accelerating electric field to the right.
When it enters with the phase , the energy increases monotonically. In addition, ions that enter the particle at a phase in which they are initially decelerated are bunched into later particles when the accelerating electric field is applied, and are then monotonically accelerated. In this way, in the FQ, incoming ions with any high-frequency phase can be effectively accelerated in the end, and the strong focusing effect of the high-frequency electric fields in the vertical and horizontal directions can be utilized. At the same time, a high-frequency cavity resonator was formed.

Figure 3 shows the cross section of conventional R and FQ. 9 is a high frequency cable for supplying high frequency power to this cavity resonator. The tip 10 of the center conductor is a loop antenna-like coupler. The resonant frequency of this resonator is determined by its geometric dimensions and cannot be changed. For example, a 100MH2 H" accelerator has a length of about 1.5 ml and a diameter of 0.5 m. If this is used to accelerate another ion species, the energy of the ions will be eV voltage, m is the ion quality (jkz v is the speed of the ion), so in order to make the incident speed the same as in the case of H+, it is necessary to increase the incident energy in proportion to the mass mK, and the output energy also increases with the mass mK. In other words, in RFQ that accelerates Hl to 1 MeV, A8'' becomes 75 MeV.

Such characteristics are not suitable for the purpose of implanting various ions with various energies like an ion implanter.

Also, from a different perspective, we have developed an IMeV accelerator exclusively for As+.
To make it with FQ, the frequency remains the same and the length is changed to l/
75, or leave the length as is and set the high frequency to 1/75.

In the former case, the periodic length of the unevenness on the electrode surface is l/75, which poses a problem in electrode processing. Moreover, in the latter case, in order to match the resonance conditions of the cavity resonator, it is necessary to increase the diameter of the accelerating tube by about 75 times - both of which are unrealistic.

In addition, in the conventional structure shown in Figure 1, if the inner wall of the accelerator tube becomes contaminated by ion spatter during long-term operation, the Q value of the cavity resonator will drop, making it impossible to generate the specified high-frequency voltage. There is.

[Purpose of the invention]

The purpose of the present invention is to solve the above problems and provide an ion accelerator that can accelerate various ions to any energy from several hundred KeV to several MeV.
This makes it possible to realize an ion implanter with high voltage and large current.

[Summary of the invention]

As mentioned above, the disadvantages of the conventional method are that the frequency cannot be changed, that the accelerator tube becomes too large when the frequency is lowered, and that it is difficult to maintain the α value of the cavity resonator. To solve these problems, the quadrupole particle accelerator is equipped with an external resonant circuit.

[Embodiments of the invention]

An embodiment of the present invention will be described using FIG. 4.

Quadrupole electrodes 1/, 2/, a/, and 4/ are insulators 1
It is insulated from the accelerator tube 5 via the tube 1. Also, acceleration tube 5
A resonant circuit consisting of a coil 12 with an inductance L and a variable capacitor 13 with a capacitance CI is installed outside. The equivalent circuit in this case is shown in Figure 5. In this equivalent circuit, capacitor 17 is connected to quadrupole electrodes 1', 3' and 2'.
, 4' is the stray capacitance C2. Therefore, it is tuned to the resonant output frequency of this resonant circuit. Also, oscillator 1
The output of 6 is amplified by an amplifier 15 and then supplied to this resonant circuit through a coupling coil 14.

As a result, 1. Even if the ion species changes, the output energy can be determined arbitrarily by changing the frequency accordingly.

Furthermore, as an improvement of this method, the frequency setting of the oscillator 16, the coil 12, the variable capacitor 13, and the interelectrode capacitance 1
It is possible to use a mechanism in which the frequency setting of the resonant circuit consisting of 7 is performed in conjunction with each other.

Further, since an oscillation circuit can be constructed by applying positive feedback to the amplifier 5 from the external resonant circuit, the oscillator 16 can be omitted in this case.

In addition, by providing multiple external circuits, sine waves of multiple frequencies can be superimposed on the electrodes, and as a result,
For example, a waveform close to a rectangular wave can be used, and acceleration efficiency can be increased.

Another embodiment of the invention is shown in FIG. The DC insulation capacitors 18 and 19 are connected to the electrodes X/
, a/ and the electrodes 2/, a/ to apply a DC voltage between them. The capacitance of capacitors 18 and 19 allows high frequency voltage to be applied to electrodes 1/, 2/ and 3/.

A sufficiently large value is selected so that there is no problem in giving it to 4'. With these electrodes 1/, 3/ and 2/, 4/
A DC voltage and a high frequency voltage can be applied in a superimposed manner between the two. Therefore, in addition to the high-frequency electric field in the axial direction, an electric field similar to that of a quadrupole mass filter is generated in the direction perpendicular to the axis, so that ion acceleration and mass analysis can be performed simultaneously.

It is clear from electric circuit theory that a similar effect can be obtained by using a variable inductance instead of a variable capacitor for frequency tuning of the external resonant circuits shown in FIGS. 4 and 6.

〔Effect of the invention〕

According to the present invention, the ion species and energy can be arbitrarily set while maintaining the high efficiency of the RFQ accelerator, so that it can be applied as a high-energy, large-current ion implanter.

[Brief explanation of drawings]

Figure 1 is a diagram showing the structure of a conventional RFQ accelerator, Figure 2 is a diagram explaining the operation of the FQ accelerator, and Figure 3 is a diagram showing the structure of a conventional RFQ accelerator.
A diagram showing the electrical circuit structure of the Q accelerator and a high frequency supply method, FIG. 4 is a diagram showing an embodiment of the present invention, FIG. 5 is a diagram showing an electrical equivalent circuit of the present invention, and FIG. 6 is a diagram showing another example. It is a figure showing an example. 1, 2.3.4.1', 2', 3', 4'...quadrupole electrode, 5...acceleration tube, 6,7.8...axial electric field component on the axis Arrow showing, 9... Coaxial cable, lO...
- Loop antenna, 11... Insulator, 12... Inductance, 13... Variable capacitor, 14... Coupling coil, 15... Amplifier, 16... Oscillator, 17... Stray capacitance i between electrodes, 18.19... Capacitor, 20... Line 2 Figure ta) Figure 4 - Figure 5 Figure 1 (Inside the Central Research Institute

Claims (1)

[Scope of Claims] 1. A quadruple seed particle accelerator having a structure in which opposing surfaces of quadrupole electrodes are corrugated, characterized in that a high frequency resonance circuit is installed outside the acceleration tube. 2. A quadruple seed particle accelerator according to claim 1, characterized in that a plurality of resonant circuits are provided, whereby a plurality of high-frequency electric fields of different frequencies are superimposed and applied to the electrodes. . 3.% The quadruple seed particle accelerator according to claim 1 or 2, characterized in that the resonance frequency is variable. 4. A quadruple seed particle accelerator according to claim 1, characterized in that direct current and alternating current can be applied in a superimposed manner to the quadrupole electrodes.