JP2016146244A - Klystron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a klystron capable of collecting energy with CPD and improving overall efficiency.SOLUTION: The klystron includes: an electron gun section 1, having a cathode 1b and an anode 1c, for emitting an electron beam; a collector 2; a high frequency interaction section 3 for outputting a high frequency output signal obtained by amplifying an input signal; a focusing coil 4; an output waveguide 5; an acceleration power supply 20; a power supply 30; and a controller 40. The acceleration power supply 20 supplies a voltage between the cathode 1b and the high frequency interaction section 3. The power supply 30 supplies a voltage between the cathode 1b and the collector 2. The controller 40 controls output signal power to have 85% of a saturation region or less.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a klystron.

  In general, a klystron is known as a vacuum tube for amplifying radio waves. The klystron includes an electron gun unit that emits an electron beam, a collector that captures a used electron beam, a high-frequency interaction unit, and a focusing coil that focuses the electron beam emitted from the electron gun unit. .

  The high-frequency interaction unit includes a drift tube through which the electron beam emitted from the electron gun unit passes, and an input cavity, an intermediate cavity, and an output cavity provided along the traveling direction of the electron beam in the middle of the drift tube. , And by inputting an input signal to the input cavity, a high-frequency output signal amplified from the output cavity is output. In order to extract high frequency from the output cavity, an output waveguide is joined to the side surface of the output cavity.

  The used electron beam after the amplification is still incident on the collector with a certain amount of energy. When the electron beam collides with the inner wall (metal wall) of the collector, the energy of the electron beam is converted into thermal energy. The converted thermal energy is consumed by the cooling mechanism around the collector.

  In the gyrotron, a method of recovering energy by CPD (Collector Potential Depression) is known. In this method, the collector potential is lowered below the potential of the high-frequency interaction unit, thereby surplus energy of the electron beam is electrostatically recovered to improve the operation efficiency and reduce the collector thermal load. In electron tubes other than klystrons, such as gyrotrons and traveling wave tubes, the overall efficiency is improved by recovering the energy of electrons by this CPD.

JP-A-57-82938 JP-A-7-37515 JP 2002-203488 A

  By the way, when the method of recovering the energy is applied to the klystron, there are the following problems. In the klystron, due to its operating principle, the energy conversion efficiency of the electron beam is higher than that of other electron tubes. Therefore, there is a characteristic that the energy dispersion of the used electron beam (spent beam) is large. Therefore, when energy recovery by CPD is performed in the klystron, electrons having energy close to zero become retrograde electrons, and there is a high possibility that the stable operation of the klystron will be hindered.

For this reason, there are almost no klystrons using a method of recovering energy by CPD except for a few special cases, and they are not put into practical use. For this reason, a klystron capable of recovering energy by CPD and improving the overall efficiency is desired.
The present invention has been made in view of the above points, and an object thereof is to provide a klystron capable of recovering energy by CPD and improving the overall efficiency.

The klystron according to one embodiment
An electron gun unit having a cathode and an anode and emitting an electron beam;
A collector for capturing the electron beam;
An input cavity connected between the electron gun portion and the collector, electrically insulated from the collector, located between the electron gun portion and the collector, at least one located between the input cavity and the collector Two intermediate cavities, an output cavity located between the intermediate cavities and the collector and having a hole, and a drift pipe connecting the input cavities, the intermediate cavities and the output cavities, and the input A high-frequency interaction unit that outputs an output signal of a high frequency amplified from the output cavity by inputting an input signal to the cavity;
A focusing coil that surrounds the outer periphery of the high-frequency interaction unit and focuses the electron beam emitted from the electron gun unit;
An output waveguide joined to the high-frequency interaction unit, communicated with the hole, and extracts the output signal from the output cavity through the hole;
An accelerating power supply for applying a voltage between the cathode and the high-frequency interaction unit;
A power supply for applying a voltage between the cathode and collector;
And a control unit that controls the power of the output signal to be 85% or less of a saturation region.

FIG. 1 is a schematic configuration diagram illustrating a klystron according to an embodiment. FIG. 2 is an enlarged schematic cross-sectional view showing a part of the klystron, and shows a state in which the top drift portion and the collector shown in FIG. 1 are electrically insulated by a high voltage insulating member. FIG. 3 is a graph showing changes in output power with respect to input power in the klystron. FIG. 4 is a graph showing a change in output power with respect to input power when the klystron is operated in the non-saturated linear region and the saturated region, respectively. FIG. 5 is a graph showing changes in the RF conversion efficiency, the overall efficiency, and the CPD voltage with respect to the electron beam perveance when the klystron is operated in the unsaturated linear region. FIG. 6 is a schematic configuration diagram showing a modified example of the klystron, showing a collector and a power supply power source.

Hereinafter, a klystron according to an embodiment will be described in detail with reference to the drawings.
As shown in FIG. 1, the klystron includes an electron gun unit 1, a collector 2, a high frequency interaction unit 3, a focusing coil 4, an output waveguide 5, an acceleration power source 20, a power supply power source 30, And a control unit 40. In this embodiment, the klystron is a pulse klystron. The collector 2, the high-frequency interaction unit 3, and the output waveguide 5 are each formed of metal.

  The electron gun unit 1 includes an electron gun 1a that emits an electron beam, and a cathode 1b and an anode 1c that accelerate the electron beam emitted from the electron gun 1a and create an electron flow in the collector 2 direction. The electron gun 1a emits one electron beam. In this embodiment, the electron gun unit 1 has one electron gun 1a. When it is desired to emit a plurality of electron beams, the electron gun unit 1 only needs to have a plurality of electron guns 1a.

  The collector 2 captures a used electron beam (spent beam) that has passed through the high-frequency interaction unit 3 and converts the remaining energy into thermal energy. The collector 2 is cooled by a cooling mechanism (not shown). Here, the main cooling system of the cooling mechanism is a water cooling system.

  The high frequency interaction part 3 is a body part of a klystron. The high-frequency interaction unit 3 is hermetically connected between the electron gun unit 1 and the collector 2. The high-frequency interaction unit 3 includes an input cavity 3a located between the electron gun unit 1 and the collector 2, at least one intermediate cavity 3b located between the input cavity 3a and the collector 2, an intermediate cavity 3b, and a collector. 2 and an output cavity 3c in which a hole O is formed, and a drift pipe 3d in which the input cavity 3a, the intermediate cavity 3b, and the output cavity 3c are connected in an airtight manner. In this embodiment, the high-frequency interaction unit 3 has three intermediate cavities 3b. The input cavity 3a, the intermediate cavity 3b, and the output cavity 3c are formed by cavities formed in the drift tube 3d.

  Each of the cavities includes a cylindrical inner peripheral wall, a cylindrical outer peripheral wall, an annular lower end wall that hermetically closes a lower end between the inner peripheral wall and the outer peripheral wall, and an upper end between the inner peripheral wall and the outer peripheral wall. It has an annular upper end wall that closes and an opening that opens in the axial direction at the center, and is formed coaxially. The surface of the high-frequency interaction unit 3 on the vacuum side is excellent in conductivity, and the surface is plated with copper, for example.

  Here, the operation principle of the high-frequency interaction unit 3 will be described in detail. An input signal to be amplified is introduced into the input cavity 3a. The input signal is a radio wave (microwave). When the electron beam passes through the input cavity 3a, the electron beam is velocity-modulated by the introduced input signal. Thereafter, while the electron beam passes through the uniform electric field, density modulation occurs in the electron beam, and the electron beam is gradually bunched. Further, each time the gathered electron beams pass through the intermediate cavity 3b, a high frequency electric field is generated in the cavity by interaction. As a result, the electron beam is again subjected to velocity modulation by the electric field.

The finally gathered electron beams induce a large alternating electric field when passing through the gap of the output cavity 3c, and are extracted from the output cavity 3c to the outside as an amplified high frequency (high power microwave) output signal. It is.
That is, the high frequency interaction part 3 outputs the high frequency output signal amplified from the output cavity 3c by inputting an input signal into the input cavity 3a.

The focusing coil 4 is formed in a cylindrical shape and surrounds the outer periphery of the high-frequency interaction unit 3. The focusing coil 4 focuses the electron beam emitted from the electron gun unit 1.
The output waveguide 5 is joined to the high-frequency interaction unit 3 and communicated with the hole O. An output window 5a formed of a dielectric is airtightly attached to the output waveguide 5. The surface on the vacuum side of the output waveguide 5 is excellent in conductivity, and the surface on the vacuum side of the output waveguide 5 is plated with copper, for example. The output waveguide 5 takes out an output signal from the output cavity 3c through the hole O.

Next, the high-frequency interaction unit 3 and the collector 2 will be further described.
As shown in FIGS. 1 and 2, the high-frequency interaction unit 3 further includes a top drift unit 10.

  The top drift part 10 is formed in a cylindrical shape. The inner peripheral surface of the top drift portion 10 is excellent in conductivity, and the inner peripheral surface is subjected to, for example, copper plating. The top drift part 10 has a flange 10 a on the side facing the collector 2. The flange 10a is formed in an annular shape.

  The collector 2 has a collector body 2a and a flange 2b. The flange 2b is located on the outer peripheral surface side of the collector body 2a. The collector body 2a and the flange 2b are integrally formed. The flange 2b is formed in an annular shape. The flange 2b faces the flange 10a with a sufficient interval.

The flange 10 a and the flange 2 b are joined via the high voltage insulating member 11. The high voltage insulating member 11 is formed in a cylindrical shape. The high voltage insulating member 11 maintains a sufficient insulation distance between the flange 10a and the flange 2b. The high voltage insulating member 11 connects the flange 10a and the flange 2b in a vacuum-tight manner.
The collector 2, the high frequency interaction part 3, the output waveguide 5 and the like form an airtight vacuum vessel. Although not shown, the electron gun unit 1 is accommodated in the vacuum container.

  As shown in FIG. 1, the acceleration power source 20 applies a voltage between the cathode 1 b and the high-frequency interaction unit 3. Specifically, the acceleration power source 20 applies a voltage between the cathode 1b and the drift tube 3d. The acceleration power supply 20 applies a voltage of, for example, −90 kV to the cathode 1b as a negative high voltage. The high frequency interaction unit 3 including the drift tube 3d is set to the ground potential. The anode 1c connected to the high frequency interaction unit 3 is also set to the ground potential.

  The power supply power source 30 provides a voltage between the cathode 1 b and the collector 2. The power supply power source 30 applies a negative high voltage to the collector 2. The collector 2 is set to a high potential of, for example, −50 kV as a negative high potential. Since a deceleration electric field is applied between the high-frequency interaction unit 3 (body unit) and the collector 2, the klystron is configured to recover the energy of the electron beam. The klystron is also configured to recover energy for a voltage of −50 kV (CPD voltage).

  The control unit 40 can adjust the current of the input signal and control the power of the output signal. The detection unit 50 can detect at least a part of the output signal. For example, the control unit 40 can acquire information on the output signal detected by the detection unit 50 and adjust the current of the input signal based on the acquired information.

In addition, the control unit 40 can control the perveance per electron beam to be 1.6 μP or less. Further, the control unit 40 can control the pulse duty ratio of the output signal to be from 10% to CW (continuous wave).
A klystron is formed as described above.

Next, the operation of the klystron will be described from the viewpoint of the power of the input signal (hereinafter referred to as input power) -power of the output signal (hereinafter referred to as output power).
FIG. 3 is a graph showing changes in output power with respect to input power in the klystron. As shown in FIGS. 1 and 3, it can be seen that the output power has a saturated region and a non-saturated linear region.

The saturation region is a region where the output power is saturated and the change in the output power is small even when the input power is changed. The conventional klystron has been operated in the saturation region.
On the other hand, the non-saturated linear region is a region where the output power changes in a form close to linear with respect to the change in input power. In the output power with the same electron beam voltage and current, the non-saturated linear region has a value of 85% or less of the saturated region. In this embodiment, as described above, the control unit 40 controls the output power to be 85% or less of the saturation region.

  As described above, in the non-saturated linear region, the output power changes in a form close to linear with respect to the input power. Therefore, in the non-saturated linear region, the control unit 40 uses the detection unit 50 to feed back the output power. It is suitable when controlling to apply to input power. The control unit 40 can control the output power with high accuracy by adjusting the input power (current of the input signal) within the non-saturated linear region, thereby stabilizing the output power.

  FIG. 4 is a graph showing a change in output power with respect to input power when the klystron is operated in each of the unsaturated linear region and the saturated region. As shown in FIG. 4, when attention is paid to RF (radio frequency) conversion efficiency, the same output power is output, so that the operation is performed in a non-saturated linear region, and the voltage or current of the electron beam is decreased to be saturated. It can be seen that the RF conversion efficiency is higher when operating in the saturation region than when operating in the region.

  Therefore, in this embodiment, by adopting a system in which the klystron recovers energy by CPD, the output power (total efficiency) is improved to the same extent as when operating in the saturated region in the operation in the unsaturated linear region. Can do. In addition, the output power can be improved without increasing the voltage or current of the electron beam.

  Here, the CPD is an abbreviation of Collector Potential Depression, and the excess energy of the electron beam is electrostatically reduced by lowering the potential of the collector 2 from the potential of the high-frequency interaction unit 3 (body portion). This is a system that improves the operation efficiency and reduces the collector thermal load.

Next, the result of the energy analysis of the electron beam using the simulation code for analyzing the operation of the klystron will be described.
Since the RF conversion efficiency is high in the saturation region, the energy dispersion of the used electron beam becomes large and energy recovery by CPD is almost impossible. On the other hand, since the RF conversion efficiency is lower in the unsaturated linear region than in the saturated region, the energy dispersion of the used electron beam can be reduced, so that more energy can be recovered by CPD. It can be expected that the overall efficiency including output power can be greatly improved.

  FIG. 5 is a graph showing changes in the RF conversion efficiency, the overall efficiency, and the CPD voltage with respect to the electron beam pervance when the klystron is operated in the unsaturated linear region. FIG. 5 is also an example of the calculation result of the efficiency improvement effect by CPD. As shown in FIG. 5, it can be seen that the overall efficiency can be further increased by lowering the electron beam perveance.

  As described above, the operation conditions of the klystron of this embodiment equipped with CPD are as follows.

The operating region is a non-saturated linear region that is 85% or less of the output power in the saturated region.

-The perveance per electron beam is set to 1.6 μP or less.

• The pulse duty ratio of the high-frequency output signal is 10% to CW (continuous wave).

• The number of CPD stages is one.

The high frequency interaction part 3 (body part) is set to the ground potential, and the collector 2 side is set to the negative potential.

-The main cooling method of the collector 2 is a water cooling type.

  According to the klystron according to the embodiment configured as described above, the klystron is electrically insulated from the electron gun unit 1, the collector 2, and the collector 2, and amplifies the input signal that is input. The high-frequency interaction unit 3 that outputs a high-frequency output signal, the focusing coil 4, the output waveguide 5, the acceleration power source 20, the power supply power source 30, and the control unit 40 are provided.

  The acceleration power supply 20 can apply a voltage between the cathode 1b and the high-frequency interaction unit 3. The power supply power source 30 can apply a voltage between the cathode 1 b and the collector 2. The control unit can control the output power to be 85% or less of the saturation region.

  Since the klystron can be operated in the unsaturated linear region, energy can be recovered by CPD, and the overall efficiency can be improved to the same level as the RF conversion efficiency when operated in the saturated region.

Since the control unit 40 can control the output power with high accuracy by adjusting the input power (current of the input signal) within the non-saturated linear region, the output power can be stabilized. Further, the control unit 40 controls the pervance per electron beam to be 1.6 μP or less, whereby the output power can be further stabilized.
From the above, it is possible to obtain a klystron capable of recovering energy by CPD and improving the overall efficiency.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

  The number of stages of the CPD is not limited to one and may be a plurality of stages (multistage type). For example, as shown in FIG. 6, the collector 2 is divided along the traveling direction of the electron beam, and is formed of N divided portions D (D1, D2,... DN) that are electrically insulated from each other. Yes.

  The power supply 30 has N-1 power supply units PB (PB1, PB2,... PBN-1). The 2nd power supply part PB gives a voltage between the adjacent division parts D so that the potential difference between the adjacent division parts D may be 5 kV or less.

The plurality of divided portions D are joined via the high voltage insulating member 12. The high voltage insulating member 12 is formed in an annular shape. The high voltage insulating member 12 maintains a sufficient insulation distance between the divided portions D, and the high voltage insulating member 11 does not have to hold the insulation distance as much as the high voltage insulating member 11. The high voltage insulating member 12 connects the plurality of divided portions D in a vacuum-tight manner.
Here, the N may be a natural number of 2 or more. When N = 10 and the potential difference between the division parts D is 5 kV, the division part D1 is set to a high potential of −50 kV as in the above-described embodiment. Can be considered.
The present invention is not limited to the klystrons described above, and can be applied to various klystrons.

  DESCRIPTION OF SYMBOLS 1 ... Electron gun part, 1a ... Electron gun, 1b ... Cathode, 1c ... Anode, 2 ... Collector, 3 ... High frequency interaction part, 3a ... Input cavity, 3b ... Intermediate cavity, 3c ... Output cavity, 3d ... Drift tube, 4 ... Focusing coil, 5 ... Output waveguide, 5a ... Output window, 10 ... Top drift part, 11, 12 ... High voltage insulating member, 20 ... Acceleration power supply, 30 ... Power supply power supply, 40 ... Control part , 50... Detecting unit, D (D1, D2,... DN)... Dividing unit, PB (PB1, PB2,... PBN-1).

Claims (6)

An electron gun unit having a cathode and an anode and emitting an electron beam;
A collector for capturing the electron beam;
An input cavity connected between the electron gun portion and the collector, electrically insulated from the collector, located between the electron gun portion and the collector, at least one located between the input cavity and the collector Two intermediate cavities, an output cavity located between the intermediate cavities and the collector and having a hole, and a drift pipe connecting the input cavities, the intermediate cavities and the output cavities, and the input A high-frequency interaction unit that outputs an output signal of a high frequency amplified from the output cavity by inputting an input signal to the cavity;
A focusing coil that surrounds the outer periphery of the high-frequency interaction unit and focuses the electron beam emitted from the electron gun unit;
An output waveguide joined to the high-frequency interaction unit, communicated with the hole, and extracts the output signal from the output cavity through the hole;
An accelerating power supply for applying a voltage between the cathode and the high-frequency interaction unit;
A power supply for applying a voltage between the cathode and collector;
A klystron comprising: a control unit that controls the power of the output signal to be 85% or less of a saturation region.   The klystron according to claim 1, wherein the control unit adjusts a current of the input signal and controls power of the output signal. The electron gun unit further includes an electron gun that emits one electron beam,
2. The klystron according to claim 1, wherein the control unit controls a perveance per one electron beam to be 1.6 μP or less.   2. The klystron according to claim 1, wherein the control unit performs control so that a pulse duty ratio of the output signal is from 10% to a continuous wave. The collector is divided along the traveling direction of the electron beam, and is formed of N divided portions that are two or more natural numbers that are electrically insulated from each other.
The power supply power source includes N-1 power supply units for applying a voltage between the adjacent division units so that a potential difference between the adjacent division units is 5 kV or less. The klystron according to 1. The high-frequency interaction unit is set to a ground potential,
The klystron according to claim 1, wherein the power supply power supply applies a negative high voltage to the collector.

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