JP4853940B2 - High frequency power measuring device in high frequency heating device - Google Patents

Description

  The present invention relates to a high-frequency heating device for a nuclear fusion device, and more particularly to a high-frequency power measuring device.

  A high-frequency heating device has one purpose of heating a super-high temperature of 100 million degrees or higher where high-power high-frequency waves are incident on high-temperature plasma and a nuclear fusion reaction occurs efficiently. The MW class high frequency generated by the oscillation tube and the amplifier is lost in the transmission line until reaching the plasma, and all of the oscillated power cannot enter the plasma.

 The apparatus of the present invention measures transmission power in a specific range by measuring the transmitted high-frequency power and measuring the power incident on the plasma, or by measuring the high-frequency power at an arbitrary location on the transmission path. And abnormal loss (high frequency discharge, etc.) of the equipment constituting the transmission circuit. In the conventional apparatus, high-frequency power measurement has been performed by the following methods (1), (2), and (3).

(1) A method of calibrating the transmission power by making a small hole that leaks high frequency in the mirror part of the 90 ° bend portion of the transmission line and measuring the high frequency leaking from the hole (Non-Patent Document 1).
(2) A high-frequency beam is branched from the main transmission line, and all high-frequency waves are incident on a cylindrical tank for high-frequency absorption called a dummy load. heat. A method of measuring the amount of electric power from this generated heat (Non-Patent Document 2).

(3) Although the structure is similar to the above (2), it is not a method of removing heat by repeating reflection inside the high frequency absorption tank, but the high frequency beam is incident on the center of the high frequency absorption tank, The high frequency is scattered by being incident on the center of the aluminum reflector on the cone, the high frequency is absorbed by a cylindrical ceramic measuring plate, and the heat is removed with cooling water. A method of measuring the amount of power from this generated heat.
IA Gorelov et al; "Calorimetric Power Measurements of the DIII-D Gyrotron System," Bull. Am Phys. Soc. 46, p. 302 (2001) Moeller ,; CP; Prater, -R; Lin, SH; "Components and transmission systems for ECH," GA Technologies, Inc, San Diego, CA (USA).

The problem of the background technology (1) is
1) The amount of power varies depending on the high frequency polarization and mode.
2) Use a detector to detect the minute high frequency leaking from the hole. Therefore, it depends on the performance inherent to the detector. The 100GHz band detector has unstable characteristics and cannot maintain a certain level of performance due to aging and environmental conditions.

The problem of the background technology (2) is
1) Since the beam must enter the dummy load by changing the direction of the high-frequency beam in the main transmission path, a loss occurs in the process.

2) Since high-frequency waves are scattered inside the dummy load, the degree of vacuum is likely to increase depending on the conditions, and there is a high possibility of simultaneous discharge.
3) It is difficult to reduce the size and weight, and cannot be easily installed in high places or complicated places.

4) Cannot be installed directly on the main transmission line. (In order to guide high frequency to the dummy load, it is necessary to change the transmission line with a waveguide switch etc.)
The problem of the background technology (3) is
1) Since the beam must enter the dummy load by changing the direction of the high-frequency beam in the main transmission path, a loss occurs in the process.

2) When the center axis of the high-frequency beam deviates from the center of the aluminum reflector on the cone, the high frequency concentrates in a certain direction and the cylindrical ceramic is damaged.
3) When the ceramic breaks, cooling water leaks into the waveguide that is the transmission path, and oxidation and damage in the waveguide occur simultaneously with the vacuum break.

  In the present invention, high power high frequency waves propagating in the waveguide of the main transmission path are directly passed through the dielectric, and the high frequency power converted into heat is measured there. Can be measured. In addition, by using a dielectric having an optimum dielectric loss tangent value according to the amount of electric power, the device can control the temperature rise of the dielectric detector.

  The total polarization is expressed in the direction of the electric field direction and has any polarization angle of 0 to 360 degrees, and means linear polarization, elliptical polarization, and circular polarization. Also, the dielectric loss tangent means that when a substance is placed in an alternating electric field and there is a part that changes its direction violently according to the change of the electric field, frictional resistance is generated at the molecular level and heat is generated. The tangent value is a value specific to the type of dielectric that represents the magnitude of this heat generation.

 The cooling structure (cooling water leakage) in the device, which was problematic in the prior art, is outside the power detection unit that generates heat without being affected by high power and high frequency, and after the power measurement is completed, the detection unit moves to the extraction position from the transmission line At this point, the problem is solved by removing the heat by contacting the cooling medium.

  That is, the present invention is a high frequency power measurement unit comprising a high frequency power detection unit, an absorbed power holding unit, a drive unit, a heat insulation unit, a heat removal unit, a detector fixing unit, a waveguide, a movable waveguide, and a vacuum exhaust port. When measuring high-frequency power, the drive unit is operated to move the power detection unit into the waveguide of the high-frequency transmission path, and the high-power high-frequency wave propagating in the waveguide is directly passed through the dielectric of the detection unit. Therefore, the high frequency power converted into heat is measured with a thermometer, the high frequency power is found from a predetermined relationship with the measured temperature, and when the power measurement is completed, the power detection unit is moved and stored outside the transmission line. In the power detector insertion position, the movable waveguide moves and fills the waveguide gap of the transmission line, thereby entering the measuring instrument without increasing the high frequency loss of the transmission circuit. High frequency to reduce leakage high frequency It is a power measurement device.

  The high-frequency power measuring device of the present invention can measure power of all polarized waves and all modes, and can be installed at any location on the main transmission line, and does not interfere with high-power transmission on the main high-frequency transmission line. Thereby, there is an advantage that transmission efficiency measurement at an arbitrary place on the transmission path and high-frequency power measurement corresponding to all polarized waves can be performed. The characteristic effects are shown below.

(1) High-frequency power measurement with different polarization and mode can be performed. (2) Long transmission path waveguides can be installed at any location.
(3) Since the heat generated by the high frequency does not escape due to the heat insulation structure of the power detector, high-precision measurement is possible.

(4) Since a paper heater is built in the power detector, heat input calibration can be performed easily.
The above heat input calibration has the following meaning. When high frequency passes through the dielectric, frictional resistance is generated at the molecular level and heat is generated. The increase in heat generation temperature at this time is expressed as heat input. In the device of the present invention, by incorporating an electric heater, the power supplied to the high-frequency power detection unit can be determined from the energized voltage and current, and by measuring the rising temperature of the detection unit at this time, the supply power and the rising temperature The relationship is known, and power calibration is performed from this calibration value and the temperature when a high frequency passes through the dielectric, and this operation is heat input calibration.

 (5) During high power transmission, the power detector is movable and optionally equipped with a function to close the waveguide gap, so that it does not increase the high-frequency transmission loss of the main transmission path and enters the measuring instrument. This has the effect of minimizing leakage high frequency.

 (6) The heat removal of the high-frequency power detection unit is performed by contact with the cooling unit at the position pulled out from the main transmission path, and can be either water-cooled or air-cooled depending on the environment of the installation site. In the case of water cooling, the cooling water flow path is outside the power detection unit that generates heat, and water leakage into the apparatus can be made almost as long as the metal in the cooling water path is not mechanically broken.

 (7) MW-class high-power, high-frequency power measuring device is compact, lightweight, easy to install, can be directly coupled to the main transmission path, and can be used in various environments.

  In the high-frequency power detector for measuring MW class high power, artificial diamond is used for the dielectric element. The reason is that it is excellent in heat conduction (it is easy to escape the heat generated by the diamond detector) and the dielectric loss is small (it is difficult to generate heat even when a large high frequency power passes through the diamond detector). Is suitable.

 The high-frequency power detector is inserted into the main high-frequency transmission line only at the time of measuring the high-frequency power, and is cooled by being drawn out from the transmission line after the measurement is completed. In order to insert a high-frequency power detector into the high-frequency transmission line, a gap is opened in the waveguide cross section (the narrowest possible gap has a lower high-frequency transmission loss). The waveguide gap of the path is compatible with all polarized waves and all modes without losing the transmission loss of the main high-frequency transmission line by replacing the high-frequency power detector with the movable waveguide inserted and fixed in the main transmission line A high-power high-frequency power measuring device can be realized. The waveguide gap is a gap of a cut portion provided between the waveguides 11a and 11b. A high-frequency power detector is inserted between the cut portions at the time of measurement, and pulled up outside the time of measurement. Is sealed with a movable waveguide having the same diameter as the waveguide.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a vertical cross-sectional view of a high-frequency power measuring device during high-frequency power measurement. FIG. 2 is a longitudinal sectional view of the high-frequency power measuring device outside the high-frequency power measurement time. The main components are a high-frequency power detection unit 1, an absorbed power heat holding unit 2, heat insulation units 3a and 3b, a drive mechanism 5, a heat removal unit 6, a cooling contact 7, a movable waveguide 12, and a power detection unit fixing unit 13. An electric heater 19 for power calibration and a thermocouple 20 for temperature measurement are main components, and the same waveguides 11a and 11b as the high-frequency transmission path are connected to the main body outer cylinder 14 for connection to the high-frequency transmission path. It is attached via a vacuum flange 18. The waveguide has a narrow gap in the cross section (a narrow gap as much as possible is desirable in terms of measurement accuracy, but is 3 to 4 mm due to structural limitations), so that the high-frequency power detector 1 as shown in FIG. Is inserted to detect the high-frequency power transmitted through the waveguide.

  For the high-frequency detector 1, selection of materials, shape design, and manufacturing accuracy are important. In selecting a dielectric detection element material, dielectric materials having different dielectric loss tangents are used according to the magnitude and frequency of the high-frequency power to be measured. In the examples, the design was performed on the premise of high-power high-frequency power measurement at 110 GHz, 1 MW class, and short pulses. Since the dielectric loss is proportional to the frequency and the dielectric loss tangent of the material, a material having a lower dielectric loss tangent is suitable for a higher frequency such as 110 GHz. For this reason, the material of the high-frequency detection unit 1 can easily remove the heat generated by the dielectric detection element (having a high thermal conductivity up to 10 W / cmK), and the heat generated by the 1 MW class high power high frequency is relatively low (dielectric loss tangent up to 5 × 10 5 -4) Artificial diamonds (artificial diamonds with a relatively large dielectric loss tangent were selected) were used.

The thickness t of the dielectric detection element is
t = n · λL / 2 (t: thickness n: integer)
λL is the wavelength in the dielectric, and the wavelength in vacuum is λ0
λL = 1 / √ε ・ λ0 (ε: dielectric constant of dielectric)
In this example, the diamond dielectric constant ε = 5.68 and the frequency f = 110 GHz.
λL / 2 = 0.572 (mm)
Therefore, the thickness of the dielectric detection element is 1.14 mm when n = 2 and 1.72 mm when n = 3. Further, since the reflected wave is generated in the dielectric element portion when the thickness is different, the manufacturing accuracy is set to ± 0.01 mm. In the example, n = 2 and 1.14 mm ± 0.01 mm.

  The dielectric detection element of the detection unit 1 generates heat due to the high frequency propagated in the waveguide and is transmitted to the absorbed power heat holding unit 2. Heat is measured by an infrared thermometer or a radiation thermometer attached to the temperature measurement thermocouple 20 and the temperature measurement observation window port 16. The absorbed power heat holding unit 2 is thermally insulated by the heat insulating unit 3a, the heat insulating unit 3b, and the vacuum heat insulating layer, and can measure the high frequency power converted into heat by the dielectric detection element as the heat generation temperature without escaping to the outside.

  Heat insulation part 3a and heat insulation part 3b have a low dielectric loss tangent [~ 2x10-4 / 106 MHz], low thermal conductivity [~ 3x10-3 W / cm · K], high heat resistance [~ 150 ° C], vacuum The material with a small amount of gas [~ 2 × 10-8 Pa · m3 · s-1 · m-2] was selected. In this example, polytetrafluoroethylene was used.

  The heat insulation part 3b and the power detection part fixing part 13 have a structure in which the absorbed power heat holding part 2 is not in contact with the waveguide gap of several millimeters (3 to 4 mm in the embodiment), and unintentional release to the atmosphere or stress at the time of evacuation. In addition, since the heat insulating portion 3b and the power detecting portion fixing portion 13 have a fixed strength, they are provided with a taper structure, a fixing strength, and a fitting structure excellent in fixing accuracy that are effective when the fixing portion is inserted into the heat insulating portion 3b. Further, the gap end faces of the waveguides 11a and 11b and the end face of the movable waveguide 12 are chamfered to prevent high-frequency discharge and enable a good driving operation. Therefore, since the movable waveguide 12 is composed of a tube having the same diameter as the waveguides 11a and 11b, the waveguide gap of the transmission line is sealed when the detection unit 1 is pulled up outside the time of high frequency power measurement. To do.

  After the power measurement is completed, as shown in FIG. 2, the high frequency power detection unit 1 and the absorbed power heat holding unit 2 are moved and stored outside the transmission path, and the high frequency power detection unit 1 is pulled out by the movable waveguide 12. Moves to a fixed position and is fixed. Since the movable waveguide 12 fills the waveguide gap of the high-frequency transmission path, an effect of not increasing the high-frequency transmission loss of the high-frequency transmission main circuit can be expected, and long-pulse transmission and steady-state transmission can be handled outside the time of power measurement. The structure. Further, the heat held by the absorbed power heat holding unit 2 at the position where the movable waveguide 12 is moved and fixed to a specified position is cooled by cooling water or air cooling (air cooling fins 8 and an air cooling fan installed if necessary). Heat is removed by the structure in contact with the cooled heat removal unit 6. The cooling contact 7 used indium to improve the contact surface.

  The vacuum seal of the main body outer cylinder 14 is composed of metal gaskets 10a, 10b, 10c, 10d, and 10e for high-frequency shielding, and the other vacuum seals are manufactured by welding or brazing. In addition, since a part of the high frequency leaks from the waveguide gap at the time of power measurement, the leakage high frequency absorption dielectric (large dielectric loss tangent, high heat resistance, excellent vacuum characteristics) in the main body outer cylinder 14, In the embodiment, SiC ceramic cylinders 21a and 21b are mounted, and a space of about 0.5 mm is opened and fixed to the inner wall of the main body outer cylinder 14 for gas exhaust of the released gas. This ceramic cylinder also has a role of a fixed seat for maintaining the accuracy of the center axis deviation of the waveguides 11a and 11b.

  The absolute value of the amount of high-frequency power converted into heat by the dielectric element of the high-frequency power detection unit 1 is the electric heater 19 for power calibration built in the absorbed power heat holding unit 2 (the heater insulation is vacuum performance, heat resistance, A material having excellent electrical insulation is desirable, and in the examples, a polyimide sheet is used), and heat input calibration is performed. The detected high-frequency power amount is a part of the total high-frequency power amount, and in the calibration of the total power, comparative calibration is performed by a reference measuring instrument that absorbs the total power and measures the total heat amount. In actual calibration, a reference measuring instrument is attached to the waveguide on the downstream side of the high-frequency power measuring apparatus, and the transmitted high-frequency power is measured at the same time.

  This high-frequency power measuring device is small and light, and can be installed in the vicinity of an oscillator output or in a long transmission line of a large fusion device of several 10 to 100 meters or in a narrow place near the fusion plasma by a simple waveguide attachment / detachment operation. There are advantages. In addition, it is possible to measure transmission loss by installing it at the start and end points of a long transmission line, and if there are several places in trouble (discharge etc.) in a long transmission line, there is a possibility that it can contribute to the determination of abnormal parts. Have.

  The high-frequency power measuring device of the present invention can be used in nuclear fusion devices, large accelerator devices, high-frequency industries (for example, high-frequency incinerators), high-frequency devices that transmit through waveguides, and the like.

These are the longitudinal cross-sectional views of the high frequency electric power measuring apparatus at the time of the high frequency electric power measurement of one Example of this invention. These are the longitudinal cross-sectional views of the high frequency electric power measuring apparatus outside the time of the high frequency electric power measurement of one Example of this invention.

Explanation of symbols

1 ・ ・ ・ High frequency power detector
2 ・ ・ ・ Absorption power heat holding part
3a ・ ・ ・ Heat insulation part a
3b ・ ・ ・ Insulation part b
4 ・ ・ ・ Dielectric drive mechanism shaft
5 ・ ・ ・ Drive mechanism
6 ・ ・ ・ Heat removal part
7 ・ ・ ・ Cooling contact
8 ・ ・ ・ Air cooling fins
9 ・ ・ ・ Cooling water pipe
10a ・ ・ Metal vacuum gasket a
10b ・ ・ Metal vacuum gasket b
10c ・ ・ Metal vacuum gasket c
10d ・ ・ Metal vacuum gasket d
10e ・ ・ Metal vacuum gaskete
11a ・ ・ ・ Waveguide
11b ・ ・ ・ Waveguide
12 ... Moveable waveguide
13 ・ ・ ・ Power detector fixing part
14 ・ ・ ・ Main body outer cylinder
15 ... Dielectric movable part vacuum flange
16 ... Temperature measurement observation window port
17 ... Vacuum exhaust port
18 ... Vacuum vacuum flange
19 ・ ・ ・ Electric heater for power calibration
20 ... Thermocouple for temperature measurement
21a ・ ・ ・ SiC ceramic cylinder a
21b ・ ・ ・ SiC ceramic cylinder b

Claims (9)

A waveguide with a gap having a plane perpendicular to the waveguide of the waveguide;
A dielectric plate inserted into the gap, and
A thermometer and a heat removal metal plate installed outside the waveguide;
With
Said dielectric plate a RF power measuring device that measure the high frequency power at the thermometer by measuring the heat generated by high frequency to pass through,
It said dielectric plate mounting a driving mechanism, drained off from the gap, the high-frequency power measurement apparatus capable of contacting the rejector plate. The high-frequency power measuring apparatus according to claim 1, wherein the dielectric plate is propagated by measuring a temperature of the dielectric plate when the dielectric plate is heated by high-frequency transmission in the waveguide. A high-frequency power measuring device that calculates high-frequency power.   The high-frequency power measuring device according to claim 1, wherein the high-frequency waves propagating in the waveguide are all polarized waves and all modes.   The high-frequency power measuring apparatus according to claim 1, wherein when the dielectric plate is removed from the gap, the gap is closed with a movable waveguide having the same diameter, and power measurement is not necessary. A high-frequency power measuring device that can eliminate the influence of dielectrics and gaps on high-frequency transmission.   2. The high frequency power measuring apparatus according to claim 1, wherein a plurality of dielectric plates are made of a plurality of materials having different dielectric loss tangents and can be exchanged according to the magnitude of the measured power.   2. The high frequency power measuring apparatus according to claim 1, wherein an artificial diamond is used for the dielectric plate, and a megawatt class high power high frequency used in a fusion experiment can be measured. A waveguide with a gap having a plane perpendicular to the waveguide of the waveguide;
  A dielectric plate inserted into the gap, and
  A thermometer and a heat removal metal plate installed outside the waveguide;
With
  A high-frequency power measuring device that measures high-frequency power with the thermometer by measuring heat generated by high-frequency passage through the dielectric plate,
  At the time of high-frequency power measurement using a high-frequency power measurement device that allows a drive mechanism to be attached to the dielectric plate, removed from the gap, and brought into contact with the metal plate for heat removal,
  A high frequency power measurement method capable of quickly cooling a high frequency dielectric plate after measurement by providing a step of bringing the dielectric plate into contact with the heat removal metal plate when removing the dielectric plate from the gap.   The high-frequency power measurement device according to claim 1, wherein the dielectric plate has a built-in heater equipped with a heating wire, thereby enabling measurement calibration without opening a vacuum vessel. apparatus.   The high-frequency power measuring apparatus according to claim 1, further comprising an outer cylinder that surrounds the gap portion of the waveguide, and a radio wave absorber disposed in an inner wall surface of the outer cylinder. A high-frequency power measuring device capable of removing floating minute high-frequency components.