JPH0220949B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dummy load for high frequency heating, and particularly to a dummy load employed in a high frequency heating device used as plasma additional heat in a nuclear fusion device.

[Background of the invention]

In a type of nuclear fusion device that uses a magnetic field to confine high-temperature plasma at approximately 100 million degrees Celsius to generate a fusion reaction and extract heat, the fuel gas exists in a plasma state separated into electrons and ions, and plasma confinement It moves by winding around the lines of magnetic force of the magnetic field and following a linear trajectory. This motion is due to the Lorentz force, and the frequency of one revolution around the magnetic field line when it is wrapped around the magnetic field line is:
Generally known as electron cyclotron frequency and ion cyclotron frequency.

In addition, in order to generate a nuclear fusion reaction, it is necessary to generate high-temperature, high-density plasma, and even the torus-type fusion device, which currently has the highest temperature, can efficiently generate a nuclear fusion reaction. In order to heat the plasma to about 100 million degrees Celsius, additional heat with a large heat input of more than 20 MW is essential. Typical examples of this additional heating method include a neutral particle incident heating method and a high frequency heating method. In particular, the high-frequency heating method has many advantages, such as excellent heating efficiency and overall efficiency of the heating system. Among high-frequency heating methods, the ion cyclotron frequency of ions in the plasma, which is proportional to the square root of the product of the plasma confinement magnetic field strength and the ion's charge, and inversely proportional to the square root of the mass, or the high frequency frequency and the high frequency applied externally. The ion cyclotron resonance heating method, which directly resonantly heats ions by matching the frequencies of electromagnetic waves, is a particularly effective heating method for realizing fusion plasma.

The frequency of this high frequency electromagnetic wave is from 20MHz to 200M
It is approximately Hz, which is in the frequency range normally used by broadcasting stations. The high power in this frequency band is typically
This is achieved by a system that combines multiple stages of high-output vacuum tube amplifiers. On the other hand, high-frequency high power is measured and calibrated using a directional coupler or high-frequency dummy load. In particular, the dummy load is a basic component for high-frequency, high-power measurements, which requires little change in matching characteristics for high frequencies and resistance characteristics for large heat inputs, and excellent heat removal characteristics.

FIG. 1 shows an example of a conventional high-power dummy load. As shown in the figure, in the conventional dummy load, the outer conductor 1 has a tapered tubular shape so that the characteristic impedances are matched and the impedance is constant over a wide band. The inner conductor 2 is composed of an insulating tube 3 with a double tube structure and a sodium hydroxide aqueous solution 4 that serves as a resistor flowing inside the insulating tube 3. High frequency high power is converted into heat by the sodium hydroxide aqueous solution 4 and absorbed. be done. In such a configuration, it is essential to keep the temperature of the sodium hydroxide aqueous solution 4 constant in order to keep the resistance value constant, and normally this sodium hydroxide aqueous solution 4 is passed through a circulation pump 5, a heat exchanger 6, and an inlet/outlet. In addition to keeping the temperature of the sodium hydroxide aqueous solution 4 constant by exchanging heat with a temperature sensor 7, etc., the system also removes heat.

As described above, conventional high-frequency heating dummy loads have used conductive electrolyte solutions such as aqueous sodium hydroxide solutions as resistors. However, in this case, in order to keep the resistance value of the resistor constant, it is necessary to keep the temperature and concentration of the electrolyte constant at all times, and in order to remove heat, it is necessary to use separate systems for cooling water and electrolyte. Since a heat exchanger is required between the pumps and a pump for circulating the electrolytic solution is also required, there are problems such as corrosion, a short service life, and a long time required for operation. Additionally, in general, dummy loads for high-frequency heating have characteristics that match the impedance of the transmission line with non-reflection termination, and that the impedance of the dummy load does not change while consuming high frequency power and the matching conditions are met. required to be satisfied. Furthermore, since the impedance of the transmission line is usually designed to have a characteristic impedance of only pure resistance, the dummy load is also designed to have pure resistance against high frequencies. Furthermore, in consideration of the above points, the cooling method and structure of a dummy load for measuring the high frequency high power of a high frequency oscillator such as that used for plasma heating in a nuclear fusion device must be specially designed.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and its purpose is to provide a dummy load for high frequency heating that can suppress the temperature change of the resistor to prevent the characteristics from changing, and that can easily match the characteristic impedance. It is about providing.

[Summary of the invention]

an inner conductor connected to the transmission line; an outer conductor having a tapered extension disposed coaxially with the inner conductor and extending in the axial direction from an end of the inner conductor; and one end connected to the tip of the extension. In a dummy load for high frequency heating, which is equipped with a resistor whose other end is connected to the inner conductor, and a cooling path that serves as a passage for a cooling medium to cool the resistor, the resistor is made of conductive ceramic. an inner cylinder having one end of the resistor in direct contact with the tip of the extension, and a center portion of which forms a water supply channel for supplying a cooling medium; the inner cylinder and a spacer; and an outer cylinder which is disposed coaxially through the resistor and is fitted into the inner circumference of the resistor to form a drainage channel for draining the cooling medium between the inner cylinder and the inner cylinder.

[Embodiments of the invention]

The present invention will be explained below based on the illustrated embodiments.

FIG. 2 shows an embodiment of a dummy load for high frequency heating of the present invention.

As shown in the figure, the dummy load of this embodiment has an outer conductor flange 11 and an inner conductor 1 connected to the transmission line.
2. Outer conductor 1 arranged coaxially with the inner conductor 12
3. The outer conductor 13 is extended in the axial direction from the end of the inner conductor 12, and the extended part is formed into a tapered shape, and is terminated at the tip of the tapered outer conductor 13, and the other end is connected to the inner conductor. 12 directly connected to resistor 1
4. It is generally composed of a cooling water channel 15 through which cooling water passes for directly cooling the resistor 14, and a spacer 16 disposed between the inner conductor 12 and the outer conductor 13. Here, the inner conductor 12 and the outer conductor 13 are made of a conductor such as copper, and the spacer 16 is made of a fluororesin plate having excellent high frequency characteristics and electrical insulation characteristics. Furthermore, the cooling water channel 15 connects the inner cylinder 15a and the outer cylinder 1.
5b are arranged coaxially, and an inner cylinder 15a arranged in the center forms a water supply channel 17, through which water is supplied, and this inner cylinder 15a
A drainage channel 18 is formed by an outer cylinder 15b that is disposed outside of the resistor 14 and is in contact with the resistor 14, and this drainage channel 18
Cooling water is forced to circulate through the still,
A perforated spacer 19 is interposed between the inner cylinder 15a and the outer cylinder 15b, and the spacer 19 integrates the two, and the cooling water channel 15 also serves as a support for the resistor 14. In this embodiment, the resistor 14 is made of conductive ceramic such as silicon carbide or silicon nitride, and the inner cylinder 15a and outer cylinder 15b forming the cooling water passage 15 are made of fluorocarbon resin, epoxy resin, etc. It is composed of a molded product, and the outer surface of the outer cylinder 15b and the inner surface of the conductive ceramic are sufficiently bonded with an adhesive such as epoxy resin. Furthermore, conductive ceramic and inner conductor 1
In addition to maintaining sufficient electrical contact, the resistance value of the conductive ceramic in the longitudinal direction is designed to match the characteristic impedance of the transmission line. Further, the shape of the outer conductor 13 is such that it satisfies the characteristics of a normal non-reflection terminator.

With this configuration, since it is made of conductive ceramic, temperature changes in the resistor 14 are suppressed, so there is no fear of corrosion, etc., and the high frequency power consumed by the resistor 14 is removed by cooling water. It can be used with high power without changing its characteristics, has a long service life, and does not require a long time to operate. In addition, since a heat exchanger and an electrolyte tank are not required, the resistor 14 can be directly cooled with a simple configuration, which not only improves cooling efficiency but also has the effect of absorbing high frequency high power while satisfying matching conditions. be. Further, a cooling water channel 15 through which cooling water for cooling the resistor 14 flows is coaxially connected to an inner cylinder 15a whose central portion forms a water supply water passage through which cooling water is supplied, through the inner cylinder 15 and a spacer 16. an outer cylinder 1 which is arranged and fitted into the inner peripheral part of the resistor 14 and forms a drainage channel between it and the inner cylinder 15 for draining cooling water;
5b, so that the resistor 14 is cooled from its inner peripheral side, and the tip of the tapered extension of the outer conductor 13 is connected to one end of the resistor 14, and the members constituting the cooling channel and the cooling water Because they are brought into direct contact without going through a , it also has the effect of making it easier to match the characteristic impedance.

Note that it is particularly effective when there are restrictions on material selection or dimensions if an impedance converter is provided in front of the dummy load so that the design impedance of the dummy load becomes an appropriate value determined from the material, etc.

〔Effect of the invention〕

As explained above, according to the present invention, the resistor, whose one end is located at the tip of the tapered extension of the outer conductor and whose other end is connected to the inner conductor, is made of conductive ceramic. Temperature changes are suppressed and the product can be used without changing its characteristics. In addition, the resistor is cooled from the inner circumferential side thereof, and the tip of the tapered extension of the outer conductor is brought into direct contact with one end of the resistor without using any cooling path components or cooling medium. Therefore, it is possible to easily match the characteristic impedance.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a conventional dummy load for high-frequency heating, and FIG. 2 is a cross-sectional view of an embodiment of the dummy load for high-frequency heating of the present invention. 1, 13... Outer conductor, 2, 12... Inner conductor, 11...
Outer conductor flange, 14...Resistor, 15...Cooling channel, 15a...Inner tube, 15b...Outer tube, 16...Spacer, 17...Supply channel, 18...Drainage channel, 19...Perforated spacer.

Claims (1)

[Claims] 1. An inner conductor connected to a transmission line, an outer conductor having a tapered extension part arranged coaxially with the inner conductor and extending in the axial direction from an end of the inner conductor, and one end of which is a tip of the extension part. A dummy load for high frequency heating is provided with a resistor whose other end is connected to the inner conductor, and a cooling path that serves as a passage for a cooling medium to cool the resistor. an inner cylinder made of ceramic, in which one end of the resistor is brought into direct contact with the tip of the extension part, and the cooling path is connected to the inner cylinder, the central part of which forms a water supply channel for supplying a cooling medium; An outer cylinder is arranged coaxially with a spacer interposed therebetween and is fitted into the inner circumference of the resistor to form a drainage channel for draining the cooling medium between the outer cylinder and the inner cylinder. Dummy load for high frequency heating.