KR102253837B1 - Plasma density measuring apparatus using dispersion interferometer with single passing non-linear crystal and plasma density measuring method using the same - Google Patents

Abstract

The present invention relates to a plasma density measuring apparatus using a dispersion interferometer and a plasma density measuring method using the same. The plasma density measuring apparatus using a dispersion interferometer according to the present invention comprises: a laser oscillator which outputs laser light of a first frequency; non-linear crystals (NLC) which receive laser light from the laser oscillator and output laser light (first light) of a first frequency and laser light (second light) of a second frequency; an acousto-optic modulator (AOM) which receives the first light and the second light from the NLC and modulates the frequency, respectively, and outputs the first light, the second light, laser light (third light) obtained by frequency-modulating the first light, and laser light (fourth light) obtained by frequency-modulating the second light; an optical system which injects the first light and the second light received from the optical modulator into plasma, changes an optical path of the first light and the second light emitted through the plasma in a preset direction, and changes the optical path of the third light and the fourth light received from the optical modulator in a preset direction; a first detector for receiving, from the optical system, the first light and the third light which have passed through the plasma; a second detector for receiving, from the optical system, the second light and the fourth light which have passed through the plasma; and a density meter for measuring the phase of the laser light which has passed through the plasma based on signals output from the first and second detectors, and measuring the density of the plasma based on the measured phase.

Description

Plasma density measurement device using a dispersion interferometer that passes through a nonlinear crystal once, and a plasma density measurement method using the same.

The present invention relates to an apparatus for measuring plasma density using a distributed interferometer and a method for measuring plasma density using the same.In more detail, the structure of a distributed interferometer to which a heterodyne technique is applied can be simplified, and measurement accuracy can be improved. The present invention relates to an apparatus for measuring plasma density using an interferometer and a method for measuring plasma density using the same.

When a substance is heated to hundreds of millions of degrees (℃), electrons are separated from the gas in a molecular state one by one, and eventually separated into negatively charged electrons and positively charged ions into a plasma state. The self-constrained fusion method is a method in which the plasma is floated in the air and heated by applying a strong magnetic field to the plasma and causing the charged particles to circulate around it, focusing on the fact that the plasma is made of charged particles. For example, there are Tokamak devices and Stellarator devices as types of nuclear fusion devices using a self-constrained fusion method.

Tokamak is a round donut-shaped plasma confinement device using a magnetic field. Tokamak is a form in which a donut-shaped vacuum container is made in which the end is connected to prevent the plasma from escaping, and a magnetic coil is installed around it. When a magnetic field is formed by installing a magnet perpendicular to the moving direction of the plasma particles, the plasma moves around the magnetic field line in an orderly manner and cannot escape from inside the donut. Tokamak has the advantage that it is easy to construct due to its simple structure, and it can be manufactured and maintained at low cost. However, the tokamak has a disadvantage in that it is difficult to stably maintain and precisely control a high-capacity plasma current for a long time.

Stellar is also similar to Tokamak in that it is a donut-shaped plasma confinement device using a magnetic field. However, the Stellar is a form in which the coil itself is uniformly twisted several times like a Mobius strip, so the plasma flows along the twisted magnetic field like a pretzel and does not escape outside. Stellar has the advantage of being able to stably maintain the plasma current for a long time, precisely control it, and form a uniform plasma. However, the stellator has a disadvantage that it is not easy to construct due to its complicated structure and is expensive to manufacture.

One of the technological goals of a fusion device is to obtain a burning plasma with a high temperature and high density that can maintain its own extreme state with the fusion energy generated by the atomic fusion reaction. In order to obtain such a plasma, it is necessary to create a plasma of hundreds of millions of degrees (℃) or more. In order to maintain the plasma at a high temperature, a high-density plasma must be controlled while confining it for a long time to prevent heat loss.

For this reason, measuring and monitoring the density of plasma is an important issue in the fabrication and operation of fusion devices.

Republic of Korea Patent Publication 10-2009-0132421 (2009.12.30.) pages 4 to 6

The present invention provides a plasma density measurement apparatus using a distributed interferometer that can simply configure a structure of a distributed interferometer in a distributed interferometer to which a heterodyne technique is applied, and a plasma density measurement method using the same.

The present invention is a plasma density measuring apparatus using a distributed interferometer capable of improving measurement accuracy by allowing two lights of different wavelengths to always coincide and transmit the plasma in a distributed interferometer to which a heterodyne technique is applied, without separate laser light alignment. And it provides a plasma density measurement method using the same.

The present invention provides a plasma density measuring apparatus using a distributed interferometer and a plasma density measuring method using the same, which can reduce the cost of the apparatus and facilitate maintenance by simply configuring the structure of the distributed interferometer.

The apparatus for measuring plasma density using a distributed interferometer according to the present invention includes a laser oscillator that outputs a laser light of a first frequency, and receives laser light from the laser oscillator to obtain a first frequency of laser light (first light) and a second frequency. Non-linear crystals (NLC) that output laser light (second light), the first light and the second light are received from the non-linear crystal and frequency-modulated, respectively, and the first light, the second light, and the second light are An optical modulator (AOM, Acousto-Optic Modulator) that outputs a frequency-modulated laser light (third light) of one light and a frequency-modulated laser light (fourth light) of the second light, and a second light received from the optical modulator. The first light and the second light are incident into the plasma, the first light and the second light emitted through the plasma are changed in a predetermined direction, and the third light and the fourth light received from the optical modulator are An optical system that changes an optical path in a preset direction, a first detector that receives the first light and the third light that has passed through the plasma from the optical system, and the second light and the fourth light that has passed through the plasma from the optical system A second detector that receives a second detector and a density meter that measures the phase of the laser light that has passed through the plasma based on the signals output from the first and second detectors, and measures the density of the plasma based on the measured phase. Includes.

In one embodiment, the nonlinear crystal may output w-frequency laser light (first light) and 2w-frequency laser light (second light).

In an embodiment, the nonlinear crystal may output the first light and the second light in the same direction as the incident direction of the received laser light.

In an embodiment, the optical modulator may frequency-modulate the first light and the second light into signals of a radio frequency (RF) frequency band, respectively, and output third light and fourth light.

In an embodiment, the optical modulator may output the first light and the second light in the same direction, and output the third light and the fourth light at an angle refracted by modulation.

In an embodiment, in the optical system, the first light and the second light received from the optical modulator are passed in a traveling direction to enter the plasma, and the first light and the second light emitted after passing through the plasma are in a preset direction. A first mirror that is reflected by a light beam, a beam splitter that reflects the first light reflected from the first mirror toward the first detector, and passes the second light reflected from the first mirror toward the second detector, the A second mirror reflecting the third light received from the optical modulator toward the first detector, and a third mirror reflecting the fourth light received from the optical modulator toward the second detector.

In an embodiment, the first detector may output a signal in an RF frequency band by removing a high-frequency component and a low-frequency component from the first light and the third light interfered with each other.

In an embodiment, the second detector may output a signal in an RF frequency band by removing high-frequency components and low-frequency components from the second light and the fourth light interfered with each other.

In one embodiment, the density meter is a frequency multiplier that amplifies the frequency of the signal output from the first detector by a factor of two, a mixer that mixes the signal output from the frequency multiplier and the signal output from the second detector, the mixer A filter that removes and outputs a high-frequency component from the signal output from the filter, and a phase measurer that outputs a phase value of the signal output from the filter.

In an embodiment, the density meter may further include a digitizer that calculates a plasma density value corresponding to the measured phase value.

In one embodiment, the phase value may correspond to a phase value from which a vibration noise component caused by vibration of the fusion device is removed.

In the method for measuring plasma density using a distributed interferometer according to the present invention, a laser oscillator outputs laser light of a first frequency, and a nonlinear crystal (NLC) receives laser light from the laser oscillator to obtain a first frequency. Outputting a laser light (first light) and a second frequency laser light (second light), an optical modulator (AOM, Acousto-Optic Modulator) receives the first light and the second light from the nonlinear crystal Frequency-modulating each, and outputting a first light, a second light, a laser light (third light) obtained by frequency-modulating the first light, and a laser light (fourth light) obtained by frequency-modulating the second light, optical system The first light and the second light received from the optical modulator are incident into the plasma, the first light and the second light emitted through the plasma are changed in a predetermined direction, and received from the optical modulator. Changing the optical path of the third light and the fourth light in a predetermined direction, the first detector receiving the first light and the third light passing through the plasma from the optical system, the second detector is the optical system Receiving the second light and the fourth light that has passed through the plasma from and a density meter measures the phase of the laser light that has passed through the plasma based on the signals output from the first and second detectors, and the measurement And measuring the density of the plasma based on the phase.

In one embodiment, the step of measuring the density includes a frequency multiplier amplifying the frequency of the signal output from the first detector by a factor of two, and the mixer is the signal output from the frequency multiplier and the signal output from the second detector. Mixing, the filter outputting by removing a high frequency component from the signal output from the mixer, and a phase meter outputting a phase value of the signal output from the filter.

In an embodiment, the measuring of the density may further include calculating, by a digitizer, a plasma density value corresponding to the measured phase value.

As described above, the apparatus for measuring plasma density using the distributed interferometer and the method for measuring plasma density using the same according to the present invention can simply configure the structure of the distributed interferometer in the distributed interferometer using the heterodyne technique.

The apparatus for measuring plasma density using a distributed interferometer according to the present invention and a method for measuring plasma density using the same are applied so that two lights having different wavelengths are always coincident without separate laser light alignment in a distributed interferometer to which the heterodyne technique is applied to transmit the plasma. By doing so, the measurement accuracy can be improved.

The apparatus for measuring plasma density using the distributed interferometer and the method for measuring plasma density using the same according to the present invention can reduce the cost of the apparatus and facilitate maintenance by simply configuring the structure of the distributed interferometer.

1 is a block diagram showing the configuration of a plasma density measuring apparatus using a distributed interferometer according to an embodiment of the present invention
2 is a flowchart illustrating a plasma density measurement method using a distributed interferometer according to an embodiment of the present invention

Hereinafter, a detailed description of the plasma density measurement apparatus using the distributed interferometer and the plasma density measurement method using the same according to the present invention will be described.

An interferometer using a laser measures the distance (or thickness) of the medium, measures the refractive index, and measures the density by using the characteristic that the phase of the laser beam changes in proportion to the distance and refractive index of the medium passing through it. It can be used for the etc. For example, an interferometer can be used to measure the plasma density of a fusion device. When measuring the density of the plasma, a dichroic interferometer using two different wavelengths may be used in order to eliminate the effect of the distance change. For example, a Dispersion Interferometer transmits laser light from one laser oscillator through a nonlinear crystal (NLC) to create two laser lights with different wavelengths, and uses this to create plasma density. Can be measured.

Dispersion interferometer can measure the density of plasma by frequency-modulating the generated laser light. This method of utilizing the modulated laser light is called the Heterodyne technique. When the heterodyne technique is applied to a distributed interferometer, the direction of the phase change (increase or decrease direction) of the laser light can also be measured, and there is an advantage in that the signal can be processed by lowering the laser light to a frequency of the easy-to-handle propagation range. . However, when the heterodyne technique is applied to a distributed interferometer, one of two laser lights having different wavelengths must be separated for frequency modulation, and the two laser lights must be combined again after frequency modulation. Therefore, when the heterodyne technique is applied to a distributed interferometer, the advantage of a distributed interferometer that always matches the paths of two laser lights having different wavelengths and transmits them to a measurement object (eg, plasma) may be impaired.

The apparatus for measuring plasma density using a distributed interferometer according to the present invention can maintain the advantages of a distributed interferometer by not separating two laser beams having different wavelengths, but always matching the paths and passing them through the measurement object. In addition, the apparatus for measuring plasma density using a distributed interferometer according to the present invention can simplify the structure of the distributed interferometer by using only one nonlinear crystal (NLC), and has advantages in that cost and maintenance of the apparatus are easy.

1 is a block diagram showing the configuration of a plasma density measuring apparatus using a distributed interferometer according to an embodiment of the present invention.

Referring to FIG. 1, a plasma density measuring apparatus 100 using a dispersion interferometer includes a laser oscillator 110, a non-linear crystal (NLC) 120, and an optical modulator (AOM, Acousto-Optic Modulator) 130. , A mirror 150, optical systems 162, 164, 166, 168, a first detector 170, a second detector 180, and a density meter 190.

The laser oscillator 110 outputs laser light of a first frequency. Hereinafter, for convenience of description, it is assumed that the laser oscillator 110 outputs laser light having a preset angular frequency of ω (ω = 2πf, f is a frequency).

The nonlinear crystal 120 receives laser light from the laser oscillator 110 to receive laser light at a first frequency (hereinafter, referred to as first light 102) and laser light at a second frequency (hereinafter, referred to as second light 104). Prints. In one embodiment, the nonlinear crystal 120 may output a laser light of a ω frequency (first light 102) and a laser light of a 2 ω frequency (second light 104). Nonlinear crystal (NLC) is a kind of functional material and can be used for frequency conversion of laser light. The nonlinear crystal 120 outputs the first light 102 and the second light 104 in the same direction as the incident direction of the received laser light. The laser light enters the nonlinear crystal once before passing through the plasma. Plasma density measuring apparatus 100 using a distributed interferometer is implemented using only one nonlinear crystal 120, so manufacturing cost can be reduced, and the problem of beam alignment that may occur when a plurality of nonlinear crystals is used is fundamental. Is to be cut off.

The optical modulator 130 receives the first light 102 and the second light 104 from the nonlinear crystal 120 and performs frequency modulation, respectively. The optical modulator 130 includes a first light 102, a second light 104, a laser light obtained by frequency-modulating the first light (hereinafter, the third light 106), and a laser light obtained by frequency-modulating the second light ( Hereinafter, the fourth light 108 is output. The first light 102 and the second light 104 output from the nonlinear crystal 120 are not separated and are incident on the optical modulator 130 in the same direction, and the first light 102 output from the optical modulator 130 ) And the second light 104 are also output in the same direction without the light path being separated. In one embodiment, the optical modulator 130 outputs the first light 102 and the second light 104 in the same direction, and the third light 106 and the fourth light 108 are refracted by modulation, respectively. It can be output at the specified angle. For example, the optical modulator 130 may output the first light 102 and the second light 104 in the same direction as the incident direction.

The optical modulator 130 performs frequency modulation on the received first light 102 and the second light 104 with a signal of _{a modulation frequency (f 0) band generated by the frequency generator 191, respectively.} The third light 106 and the fourth light 108 may be output. In one embodiment, the optical modulator 130 frequency-modulates the first light 102 and the second light 104 into signals of a radio frequency (RF) frequency band, respectively, so that the third light 106 and the fourth light ( 108). Compared to the ω frequency and the 2ω frequency, which are visible or infrared frequency bands, the modulation frequency (f ₀ ) is only a few tens of MHz to several hundreds of MHz, so there may be a frequency difference of about a million times or more. (ω >> f ₀ )

In an embodiment, when the laser light is assumed to be a sinusoidal signal, an I-channel (In-phase Channel) value of each laser light may be expressed as Equation 1 below.

[Equation 1]

First light: Acos(ωt)

Second light: Bcos(2ωt)

3rd light: Ccos((ω+ f ₀ )t)

Light 4: Dcos((2ω+ f ₀ )t)

Here, A, B, C, and D are arbitrary coefficients, and t is time.

In the optical system, the first light 102 and the second light 104 received from the optical modulator 130 are incident on the plasma 140, and the first light 102 and the second light emitted through the plasma 140 (104) Changes the optical path in the preset direction. The optical system changes the optical path of the third light 106 and the fourth light 108 received from the optical modulator 130 in a preset direction.

In one embodiment, the first mirror 162 passes the first light 102 and the second light 104 received from the optical modulator 130 in a traveling direction to enter the plasma 140, and the plasma 140 The first light 102 and the second light 104 emitted after passing through) are reflected in a preset direction. For example, the first mirror 162 passes through the plasma 140 and reflects the first light 102 and the second light 104 from the mirror 150 in the direction of the beam splitter 164 Can be reflected. The plasma 140 may correspond to a plasma confined to a fusion device (Tokamak or Stellarator), and a mirror 150 capable of reflecting laser light may be installed inside the fusion device. .

Physical vibration may occur in the fusion device during operation, and the mirror 150 installed in the fusion device may also be affected by the physical vibration. Accordingly, the first light 102 and the second light 104 reflected from the mirror 150 after passing through the plasma 140 have a phase value changed by the density of the plasma 140 and the vibration of the mirror 150. The resulting phase noise is included, and in order to accurately measure the density of the plasma 140, a method of removing the phase noise caused by the vibration of the mirror 150 is required.

In one embodiment, the I-channel (In-phase Channel) values of the first light 102 and the second light 104 that are reflected from the mirror 150 through the plasma 140 are as shown in Equation 2 below. Can be indicated.

[Equation 2]

First light emitted after passing through plasma: Acos(ωt + pi(ω))

Second light emitted after passing through plasma: Bcos(2ωt + pi(2ω))

Here, pi() is a phase component of each light and includes a component due to the density of the plasma 140 and a component due to the vibration of the mirror 150. pi() can be expressed as in Equation 3 below.

[Equation 3]

pi(ω) = ωd/c + c _p nL/ω

pi(2ω)= 2ωd/c + c _p nL/(2ω)

Here, c _p nL/ω and c _p nL/(2ω) are components due to plasma density, ωd/c and 2ωd/c are components due to vibration, c _p and c are proportional constants, n is the density of plasma, L is the length of the plasma through which light has passed, and d is the path difference due to vibration.

The beam splitter 164 reflects the first light 102 reflected from the first mirror 162 toward the first detector 170, and the second light 104 reflected from the first mirror 162 is 2 It can pass in the direction of the detector 180.

The second mirror 166 reflects the third light 106 received from the optical modulator 130 toward the first detector 170, and the third mirror 168 reflects the fourth light received from the optical modulator 130. The light 108 is reflected toward the second detector 180.

The first light and the third light received by the first detector 170 cause interference, and the first detector 170 is It outputs a signal in the RF frequency band by removing the low frequency component.

In an embodiment, the output of the wave measured by the first detector 170 may be expressed as Equation 4 below.

[Equation 4]

I= [Acos(ωt+pi(ω)) + Ccos((ω+ f ₀ )t)] ²

= A ² /2 + C ² /2 + 2ACcos(ωt+pi(ω))cos(ω+f ₀ )t

= A ² /2 + C ² /2 + AC[cos(f ₀ t-pi(ω))+cos((ω+f ₀ )t+pi(ω))]

(cos α cos β = ½ [cos(α-β) + cos(α+β)])

The first detector 170 outputs a signal in an RF frequency band by removing high-frequency components and low-frequency components from the interfered first light 102 and third light 106.

That is, in Equation 4, the term cos((ω+f ₀ )t+pi(ω)) is removed as a high frequency component, and the term A ² /2 + C ² /2 is removed as a low frequency component. Accordingly, the first detector 170 finally _{outputs a signal of A*cos(f 0} t-pi(ω)). (A*=AC)

The second light 104 and the fourth light 108 received by the second detector 180 cause interference, and the second detector 180 generates the interfered second light 104 and the fourth light ( 108), the high-frequency component and the low-frequency component are removed to output a signal in the RF frequency band.

In one embodiment, the output of the wave measured by the second detector 180 may be expressed as Equation 5 below.

[Equation 5]

I= [Bcos(2ωt+pi(2ω)) + Dcos((2ω+ f ₀ )t)] ²

= B ² /2 + D ² /2 + 2BDcos(2ωt+pi(2ω))cos(2ω+f ₀ )t

= B ² /2 + D ² /2 + BD[cos(f ₀ t-pi(2ω))+cos((2ω+f ₀ )t+pi(2ω))]

(cos α cos β = ½ [cos(α-β) + cos(α+β)])

The second detector 180 removes the high frequency component and the low frequency component from the interfered second light 104 and the fourth light 108 and outputs a signal in the RF frequency band.

That is, in Equation 5, the term cos((2ω+f ₀ )t+pi(2ω)) is removed as a high frequency component, and the term B ² /2 + D ² /2 is removed as a low frequency component. Accordingly, the second detector 180 finally _{outputs a signal of B*cos(f 0} t-pi(2ω)). (B*=BD)

The density meter 190 measures the phase of the laser light passing through the plasma based on the signals output from the first detector 170 and the second detector 180, and measures the density of the plasma based on the measured phase. The density meter 190 may include a frequency generator 191, a frequency doubler 193, a mixer 195, a filter 197 and a phase meter 199. have.

The frequency generator 191 generates _{a modulation frequency f 0} of a radio frequency (RF) frequency band.

The frequency multiplier 193 amplifies the frequency of the signal output from the first detector 170 by two times. In an embodiment, a signal output from the frequency multiplier 193 may be expressed as Equation 6 below.

[Equation 6]

A*cos(2f ₀ t-2pi(ω))

The mixer 195 mixes and outputs the signal output from the frequency multiplier 193 and the signal output from the second detector 180. The mixer 195 mixes the signal output from the frequency multiplier 193 and the signal output from the second detector 180 to correspond to the sum (+) and the difference (-) of the frequencies centering on the center frequency. Output signal. The signal output from the mixer 195 can be expressed as in Equation 7 below.

[Equation 7]

A*cos(2f ₀ t-2pi(ω)) B*cos(f ₀ t-pi(2ω)) = C*cos(f ₀ t-2pi(ω)+pi(2ω)) + D*cos( 3f ₀ t-2pi(ω)-pi(2ω))

(cos α cos β = ½ [cos(α-β) + cos(α+β)])

Here, C* and D* represent coefficients.

The filter 197 removes a high frequency component from the signal output from the mixer 195 and outputs it. In an embodiment, the filter 197 may filter components of an upper side band. For example, the filter 197 filters _{a component of the 3f 0} frequency band (D*cos(3f ₀ t-2pi(ω)-pi(2ω))), and filters the _{signal of the f 0} frequency band (C*cos( f ₀ t-2pi(ω)+pi(2ω))) can be output.

In an embodiment, a signal output from the filter 197 may be expressed as Equation 8 below with reference to Equation 3.

[Equation 8]

C*cos(f ₀ t-2pi(ω) + pi(2ω)) = C*cos(f ₀ t-2(ωd/c + c _p nL/ω) + (2ωd/c + c _p nL/( 2ω)))

= C*cos(f ₀ t-3c _p nL/2ω)

In the phase of the signal output from the filter 197, the vibration noise component caused by the vibration of the fusion device is removed and only the density component is included. That is, the filter 197 outputs a signal from which a component caused by vibration of the mirror 150 has been removed.

A phase meter (IQ-mixer) 199 outputs a phase value of a signal output from the filter 197. In an embodiment, the phase meter 199 may _{convert the measured phase value (3c p} nL/2ω) into an electrical signal such as a voltage level and output it. The density (n) can be calculated by dividing the measured phase value by predetermined proportional constants (C _{p, L, ω).}

In one embodiment, the density meter 190 may further include a digitizer that calculates a plasma density value corresponding to the phase value measured by the phase meter 199. In an embodiment, a density value corresponding to a voltage level output from the phase meter 199 may be previously stored in the digitizer. The digitizer calculates and outputs a density value corresponding to the voltage level output from the phase meter 199.

2 is a flowchart illustrating an object damage method according to an embodiment of the present invention.

Referring to FIG. 2, the laser oscillator 110 outputs laser light of a first frequency (step S210). In one embodiment, the laser oscillator 110 outputs laser light having a preset angular frequency of ω (ω = 2πf, f is a frequency).

The nonlinear crystal (NLC) 120 receives laser light from the laser oscillator 110 to receive a first frequency of laser light (first light 102) and a second frequency of laser light (second light 104). Output (step S220). In one embodiment, the nonlinear crystal 120 may output a w-frequency laser light (first light 102) and a 2w-frequency laser light (second light 104).

The optical modulator (AOM) 130 receives the first light 102 and the second light 104 from the nonlinear crystal 120 and performs frequency modulation, respectively, and the first light 102, the second light 104, and The first light is frequency-modulated laser light (third light 106) and the second light is frequency-modulated laser light (fourth light 108) is output (step S230). In one embodiment, the optical modulator 130 frequency-modulates the first light 102 and the second light 104 into signals of a radio frequency (RF) frequency band, respectively, so that the third light 106 and the fourth light ( 108).

In the optical system, the first light 102 and the second light 104 received from the optical modulator 130 are incident into the plasma, and the first light 102 and the second light 104 emitted through the plasma are preset. The optical path is changed in the direction, and the optical paths of the third light 106 and the fourth light 108 received from the optical modulator 130 are changed in a preset direction (step S240).

The first detector 170 receives the first light 102 and the third light 106 passing through the plasma from the optical system (step S250), and the second detector 180 receives the second light passing through the plasma from the optical system. (104) and the fourth light 108 are received (step S260).

The density meter 190 measures the phase of the laser light passing through the plasma based on the signals output from the first detector 170 and the second detector 180, and measures the density of the plasma based on the measured phase ( Step S270). In one embodiment, the density meter 190 may include a frequency generator 191, a frequency multiplier 193, a mixer 195, a filter 197 and a phase meter 199.

The frequency multiplier 191 amplifies the frequency of the signal output from the first detector 170 by two times, and the mixer 193 combines the signal output from the frequency multiplier 191 and the signal output from the second detector 180. Mix. The filter 197 removes and outputs a high frequency component from the signal output from the mixer 197, and the phase measurer 199 outputs a phase value of the signal output from the filter 197. As described in FIG. 1, the phase value output from the phase meter 199 may correspond to a phase value from which a vibration noise component caused by vibration of the fusion device is removed. The digitizer (not shown) may calculate a plasma density value corresponding to the measured phase value. Details of the operation and processing method of each component are as described with reference to FIG. 1.

The apparatus for measuring plasma density using the distributed interferometer described with reference to FIGS. 1 to 2 and the method for measuring density using the same are implemented in the form of a recording medium including instructions executable by a computer such as an application or module executed by a computer. It could be.

Computer-readable media can be any available media that can be accessed by a computer, and includes both volatile and nonvolatile media, removable and non-removable media. Further, the computer-readable medium may include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, modules or other data. Communication media typically includes computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, or other transmission mechanism, and includes any information delivery media.

The term module may mean hardware capable of performing functions and operations according to the respective names described in the specification, and may also mean computer program code capable of performing specific functions and operations, In addition, it may refer to an electronic recording medium, such as a processor, on which a computer program code capable of performing specific functions and operations is mounted.

Although described above as an embodiment of the present invention, the technical idea of the present invention is not limited to the above embodiment, and can be implemented by a plasma density measurement apparatus and a density measurement method using various distributed interferometers within the scope not departing from the technical idea of the present invention. have.

100: plasma density measuring device using a distributed interferometer
110: laser oscillator
120: Non Linear Crystal (NLC)
130: Optical Modulator (AOM, Acousto-Optic Modulator)
150: mirror
162, 164, 166, 168: optical system
170:, the first detector
180: second detector
190: density meter

Claims (14)

A laser oscillator outputting laser light of a first frequency;
Non-linear crystals (NLC) for receiving laser light from the laser oscillator and outputting laser light (first light) of a first frequency and laser light (second light) of a second frequency;
The first light and the second light are received from the nonlinear crystal and frequency-modulated, respectively, and the first light, the second light, and the laser light (third light) obtained by frequency-modulating the first light, and the second light are frequency-modulated. An optical modulator (AOM, Acousto-Optic Modulator) that outputs the modulated laser light (fourth light);
The first light and second light received from the optical modulator are incident into a plasma, the first light and the second light emitted through the plasma are changed in a predetermined direction, and the first light received from the optical modulator is An optical system for changing the optical path of the third light and the fourth light in a predetermined direction;
A first detector configured to receive the first light and the third light passing through the plasma from the optical system;
A second detector configured to receive the second light and the fourth light passing through the plasma from the optical system; And
Dispersion interferometer including a density meter that measures the phase of the laser light that has passed through the plasma based on the signals output from the first and second detectors, and measures the density of the plasma based on the measured phase. As a plasma density measuring device using ),
The optical modulator is a plasma density measuring apparatus using a distributed interferometer for frequency-modulating the first light and the second light into signals of a radio frequency (RF) frequency band, respectively, and outputting third light and fourth light. A laser oscillator outputting laser light of a first frequency;
Non-linear crystals (NLC) for receiving laser light from the laser oscillator and outputting laser light (first light) of a first frequency and laser light (second light) of a second frequency;
The first light and the second light are received from the nonlinear crystal and frequency-modulated, respectively, and the first light, the second light, and the laser light (third light) obtained by frequency-modulating the first light, and the second light are frequency-modulated. An optical modulator (AOM, Acousto-Optic Modulator) that outputs the modulated laser light (fourth light);
The first light and second light received from the optical modulator are incident into a plasma, the first light and the second light emitted through the plasma are changed in a predetermined direction, and the first light received from the optical modulator is An optical system for changing the optical path of the third light and the fourth light in a predetermined direction;
A first detector configured to receive the first light and the third light passing through the plasma from the optical system;
A second detector configured to receive the second light and the fourth light passing through the plasma from the optical system; And
Dispersion interferometer including a density meter that measures the phase of the laser light passing through the plasma based on the signals output from the first and second detectors, and measures the density of the plasma based on the measured phase. As a plasma density measuring device using ),
The optical system
A first mirror that passes the first light and the second light received from the optical modulator in a traveling direction to enter the plasma, and reflects the first light and the second light emitted after passing through the plasma in a predetermined direction;
A beam splitter for reflecting the first light reflected from the first mirror toward the first detector, and allowing the second light reflected from the first mirror to pass toward the second detector;
A second mirror reflecting the third light received from the optical modulator toward the first detector; And
Plasma density measuring apparatus using a dispersion interferometer comprising a third mirror reflecting the fourth light received from the optical modulator toward the second detector. The method of claim 1 or 2, wherein the nonlinear crystal is
Plasma density measuring apparatus using a distributed interferometer that outputs w-frequency laser light (first light) and 2w-frequency laser light (second light). The method of claim 1 or 2, wherein the nonlinear crystal is
Plasma density measuring apparatus using a dispersion interferometer in which the first light and the second light are output in the same direction as the incident direction of the received laser light, and the laser light is once incident on a nonlinear crystal before passing through the plasma. The method of claim 1, wherein the optical modulator
Plasma density measuring apparatus using a distributed interferometer in which the first light and the second light are output in the same direction, and the third light and the fourth light are respectively output at an angle refracted by modulation. delete The method of claim 1 or 2, wherein the first detector is
Plasma density measurement apparatus using a distributed interferometer that outputs a signal in an RF frequency band by removing high-frequency components and low-frequency components from the interference first and third light. The method of claim 1 or 2, wherein the second detector is
Plasma density measurement apparatus using a distributed interferometer that outputs a signal in an RF frequency band by removing high-frequency components and low-frequency components from the interference second and fourth light. The method of claim 1 or 2, wherein the density meter
A frequency multiplier for amplifying the frequency of the signal output from the first detector by two times;
A mixer for mixing the signal output from the frequency multiplier and the signal output from the second detector;
A filter that removes and outputs a high-frequency component from the signal output from the mixer; And
Plasma density measuring apparatus using a distributed interferometer comprising a phase measuring device for outputting a phase value of the signal output from the filter. The method of claim 9, wherein the density meter
Plasma density measuring apparatus using a distributed interferometer further comprising a digitizer for calculating a plasma density value corresponding to the measured phase value.
The method of claim 9, wherein the phase value is
Plasma density measuring apparatus using a dispersion interferometer, which is a phase value from which vibration noise components caused by vibration of the fusion device confining the plasma are removed. delete delete delete

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