A high spatial resolution far infrared laser interferometer

Abstract

The application discloses a high-spatial-resolution far-infrared laser interferometer and relates to the technical field of optical interferometers.The high-spatial-resolution far-infrared laser interferometer comprises an optical platform, an optical tower, an optical support and a phase comparator system, the optical platform is fixedly provided with a far-infrared laser light source, a heterodyne interferometer table light path, a single-point frequency mixer and a linear array frequency mixer, the far-infrared laser light source comprises a first far-infrared light source and a second far-infrared light source, the light signal transmitting ends of the first far-infrared light source and the second far-infrared light source are connected with the heterodyne interferometer table light path, the far-infrared laser light emitted by the two far-infrared light sources enters the single-point frequency mixer through the interferometer table light path, the linear array frequency mixer is used as a detection channel frequency mixer and is used for receiving the signals emitted by the two sources, and the application realizes the system layout of multi-position detection under a single detection channel light path and provides a reliable measurement tool for high-spatial-resolution measurement of plasma electron density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical interferometer, and particularly relates to a high spatial resolution far-infrared laser interferometer. BACKGROUND

[0002] The far-infrared laser interferometer is a conventional diagnosis for measuring the electron density of the plasma by using the propagation characteristics of the electromagnetic wave in the plasma. With the deepening of the tokamak research, the plasma parameters are gradually improved, and the requirements for the far-infrared laser interferometer diagnosis technology are gradually increased. The far-infrared laser interferometer has been developed and applied rapidly in recent years. The technical development mainly embodies two points: the first point is that the improvement of the structure and performance of the far-infrared laser interferometer can meet the more needs of the tokamak devices of different parameters. This is realized by improving the performance of all the equipment parts of the interferometer and the overall cooperation, such as developing a compact far-infrared interferometer system to reduce the occupied space of the interferometer system, making the application of the far-infrared interferometer system more flexible, developing a high-speed rotating grating or a double-laser system to improve the time resolution of the interferometer system, and meeting the needs of the tokamak device for high time resolution, developing a short-wavelength terahertz light source to meet the needs of high-density plasma measurement, and the like. The second point is that the far-infrared laser interferometer system can be applied to different experimental devices, such as low-temperature plasma devices and plasma density measurement of rocket exhaust, so that the far-infrared laser interferometer is not limited to only being used for diagnosis in the magnetic confinement fusion device, and can also have application value in other fields.

[0003] At present, some compact tokamak fusion experimental devices (such as spherical tokamak experimental devices) have small device vacuum chambers, small plasma sizes, and large density gradients, and therefore require the far-infrared laser interferometer to have high spatial resolution to detect the plasma density distribution under high spatial resolution and perform physical experiment analysis. However, the compact tokamak has a small vacuum chamber, and the size of the diagnostic window is limited. In addition, the wavelength of the far-infrared laser is relatively long, and the diameter of the detection beam is generally large, so it is difficult to meet the multi-channel measurement under the high spatial resolution (millimeter level) performance of the compact tokamak.

[0004] Therefore, how to develop a multi-channel high spatial resolution far-infrared laser interferometer used in the small window of the compact tokamak has become a technical problem to be solved by researchers in the field. SUMMARY

[0005] The application aims to provide a high spatial resolution far-infrared laser interferometer, solve the technical problem of high spatial resolution measurement of plasma electron density on a compact tokamak fusion experimental device, and realize the system layout of multi-position detection under a single detection channel light path by using a linear array detector, an optical tower, a parabolic mirror and other devices and reasonable optical design, thereby providing a reliable measurement tool for high spatial resolution measurement of plasma electron density.

[0006] The object of the application can be achieved by the following technical solutions.

[0007] A high spatial resolution far-infrared laser interferometer comprises an optical platform, an optical tower, an optical support and a phase comparator system.

[0008] A far-infrared laser light source, a heterodyne interferometer bench light path, a single-point frequency mixer and a linear array frequency mixer are fixedly installed on the optical platform.

[0009] The far-infrared laser light source comprises a first far-infrared light source and a second far-infrared light source; the light signal sending ends of the first far-infrared light source and the second far-infrared light source are connected with the heterodyne interferometer bench light path, and the far-infrared laser emitted by the two far-infrared light sources enters the single-point frequency mixer through the interferometer bench light path; the linear array frequency mixer serves as a detection channel frequency mixer and is used for receiving the signals emitted by the two sources; the signal emitted by the first far-infrared light source directly enters the linear array frequency mixer, the detection beam emitted by the second far-infrared light source is emitted to the optical tower beside the device, the detection beam enters the plasma through the optical tower, returns to the heterodyne interferometer bench light path of the optical platform after passing through the plasma, and then enters the linear array frequency mixer; the reference signal obtained by the single-point frequency mixer and the multi-point detection signal obtained by the linear array frequency mixer enter the phase comparator system for phase calculation at the same time, and the plasma electron density values of multiple points are obtained.

[0010] As a further scheme of the application, the linear array frequency mixer is provided with multiple probes close to each other, which are used for obtaining intermediate frequency signals of multiple close point positions of the detection beam.

[0011] As a further scheme of the application, the heterodyne interferometer bench light path comprises a first converging lens, a first light splitting plate, a second light splitting plate, a second converging lens, a third converging lens, a third light splitting plate, a fourth light splitting plate, a first plane mirror, a second plane mirror, a third plane mirror, a fourth plane mirror, a fifth plane mirror, a sixth plane mirror, a first convex mirror, a first concave mirror and a second concave mirror.

[0012] As a further scheme of the present application: the light signal sending end of the first far-infrared light source is connected with the receiving end of the single-point frequency mixer in sequence through the first converging lens, the first light splitting plate, the second light splitting plate and the second converging lens; and the light signal sending end of the first far-infrared light source is connected with the receiving end of the linear array frequency mixer in sequence through the first converging lens, the first light splitting plate, the fourth light splitting plate, the second concave mirror.

[0013] As a further scheme of the present application: the light signal sending end of the second far-infrared light source is connected with the receiving end of the single-point frequency mixer in sequence through the third converging lens, the third light splitting plate, the second light splitting plate and the second converging lens; and the light signal sending end of the second far-infrared light source is connected with the receiving end of the linear array frequency mixer in sequence through the third converging lens, the third light splitting plate, the first plane mirror, the second plane mirror, the third plane mirror, the first convex mirror, the first concave mirror and the fourth plane mirror, and emits the light beam to the optical tower far away.

[0014] As a further scheme of the present application: the fifth plane mirror and the sixth plane mirror are used for receiving the detection light beam passing through the plasma, and the light beam is connected with the linear array frequency mixer in sequence through the fifth plane mirror, the sixth plane mirror, the fourth light splitting plate and the second concave mirror.

[0015] As a further scheme of the present application: the optical tower is made of non-magnetic stainless steel and is not affected by the high-strength electromagnetic field of the tokamak, is fixed by using chemical bolts, and has an internal sand filling for improving the stability of the optical tower, and a plurality of optical panels for fixing optical devices are welded on the optical tower.

[0016] As a further scheme of the present application: the optical panel is fixed with a second convex mirror, a third concave mirror, a seventh plane mirror, an eighth plane mirror and a parabolic mirror; the light emitted by the heterodyne interferometer table light path passes through the second convex mirror, the third concave mirror, the seventh plane mirror, the eighth plane mirror and the parabolic mirror in sequence, and then becomes a parallel light with a wider width, and then enters the plasma of the tokamak device.

[0017] As a further scheme of the present application: the fundamental frequency of the first far-infrared light source and the second far-infrared light source is the same, a micro frequency of the order of megahertz of the first far-infrared light source is adjusted, so that a frequency difference of the order of megahertz is generated between the two far-infrared light sources, and a middle frequency signal of the order of megahertz is obtained by the frequency mixer.

[0018] As a further scheme of the present application: the linear array frequency mixer is an integrated array detector of a plurality of single-point frequency mixers, the probe diameter is less than 2 mm, the number of probes can be 2-20 according to requirements, and the probe center spacing is less than 2.5 mm.

[0019] The present application has the following beneficial effects:

[0020] (1) Using compact array detector, small volume, compact structure, can detect multiple points of single parallel light beam, realize single beam detection beam under multi-channel high spatial resolution measurement.

[0021] (2) Using optical tower, the detection beam system and the device are separated, avoiding the influence of device vibration on optical system; the optical devices of the upper and lower windows of the device are fixed on the optical support, facilitating optical design and optical debugging.

[0022] (3) Parabolic mirror cooperates with optical tower, making the detection light become parallel light passing through the plasma in the center of the device, realizing multi-point measurement under the condition of limited window size, improving spatial resolution while saving valuable diagnostic window. BRIEF DESCRIPTION OF DRAWINGS

[0023] The application will be further described below with reference to the drawings.

[0024] Fig. 1 is the overall structure diagram of a high spatial resolution far infrared laser interferometer of the application;

[0025] Fig. 2 is the planar top view of a high spatial resolution far infrared laser interferometer of the application;

[0026] Fig. 3 is the principle diagram of high spatial resolution detection using compact array detector of the application.

[0027] In the figure: 1, optical platform; 2, first far infrared light source; 3, second far infrared light source; 4, optical tower; 5, optical support; 6, parabolic mirror; 7, single-point mixer; 8, linear array mixer; 9, plasma; 10, first converging lens; 11, first beam splitter; 12, second beam splitter; 13, second converging lens; 14, third converging lens; 15, third beam splitter; 16, fourth beam splitter; 17, first plane mirror; 18, second plane mirror; 19, third plane mirror; 20, fourth plane mirror; 21, fifth plane mirror; 22, sixth plane mirror; 23, first convex mirror; 24, first concave mirror; 25, second concave mirror 25; 26, second convex mirror; 27, third concave mirror; 28, seventh plane mirror; 29, eighth plane mirror; 30, device window; 31, 45-degree angle mirror. DETAILED DESCRIPTION

[0028] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] In the description of the present application, it should be understood that the terms "upper", "lower", "left", "right", etc. indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, and a particular orientation configuration and operation, therefore, it cannot be understood as a limitation on the present application. In addition, "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0030] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between the two elements inside. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0031] Please refer to Figs. 1-3 The present application is a kind of high spatial resolution far infrared laser interferometer, including optical platform 1, first far infrared light source 2, second far infrared light source 3, heterodyne interferometer mesa light path, optical tower 4, optical support 5, parabolic mirror 6, single point mixer 7, linear array mixer 8, phase comparator system;

[0032] The far infrared laser light source 2 / 3, the heterodyne interferometer mesa light path, the single point mixer 7 and the linear array mixer 8 are fixed on the optical platform 1.

[0033] The far infrared laser light sources include a first far infrared light source 2 and a second far infrared light source 3. The light signal transmitting ends of the first far infrared light source 2 and the second far infrared light source 3 are connected with the interferometer bench light path, the far infrared laser light emitted by the two far infrared light sources enters the single-point mixer 7 through the heterodyne interferometer bench light path, the single-point mixer 7 is used as a reference channel mixer and is a reference for phase comparison calculation of the interferometer system; the linear array mixer 8 with a plurality of linearly arranged probes is used as a detection channel mixer and also receives the signals emitted by the two far infrared light sources, the signal of the first far infrared light source 2 directly enters the linear array mixer 8, the detection light beam emitted by the second far infrared light source 3 is emitted to the optical tower 5 beside the device, the detection light beam enters the plasma 9 through the optical tower 5, returns to the optical platform bench light path after passing through the plasma 9, and then enters the linear array mixer 8. The reference signal obtained by the reference channel mixer and the multi-point detection signal obtained by the detection channel mixer enter the phase comparator system for phase calculation at the same time, and the electron density values of the plasma 9 at a plurality of points can be obtained.

[0034] The reference channel mixer and the detection channel mixer are used for beam combination of the light beams emitted by the two light sources received by the reference channel mixer and the detection channel mixer respectively to obtain interference signals, so as to provide sinusoidal intermediate frequency signals required for calculation of the plasma electron density and accurately calculate the plasma electron density. The linear array mixer 8 has a plurality of probes with close intervals, the intermediate frequency signals of a plurality of close point positions of the detection beam can be obtained, and the interferometer system has high spatial resolution measurement performance.

[0035] The heterodyne interferometer bench light path includes a first converging lens 10, a first beam splitter 11, a second beam splitter 12, a second converging lens 13, a third converging lens 14, a third beam splitter 15, a fourth beam splitter 16, a first plane mirror 17, a second plane mirror 18, a third plane mirror 19, a fourth plane mirror 20, a fifth plane mirror 21, a sixth plane mirror 22, a first convex mirror 23, a first concave mirror 24, and a second concave mirror 25.

[0036] The light signal transmitting end of the first far infrared light source 2 is connected with the receiving end of the single-point mixer 7 in sequence through the first converging lens 10, the first beam splitter 11, the second beam splitter 12, and the second converging lens 13; and the light signal transmitting end of the first far infrared light source 2 is connected with the receiving end of the linear array mixer 8 in sequence through the first converging lens 10, the first beam splitter 11, the fourth beam splitter 16, and the second concave mirror 25.

[0037] The optical signal transmitting end of the second far-infrared light source 3 is connected to the receiving end of the single-point mixer 7 in sequence through the third focusing lens 14, the third beam splitter 15, the second beam splitter 12, and the second focusing lens 13; the optical signal transmitting end of the second far-infrared light source 3 emits the light beam to the optical tower 4 at a distance through the third focusing lens 14, the third beam splitter 15, the first plane mirror 17, the second plane mirror 18, the third plane mirror 19, the first convex mirror 23, the first concave mirror 24, and the fourth plane mirror 20.

[0038] The fifth plane mirror 21 and the sixth plane mirror 22 are used to receive the probe beam after passing through the plasma. The beam will pass through the fifth plane mirror 21, the sixth plane mirror 22, the fourth beam splitter 16, and the second concave mirror 25 in sequence, and be connected to the linear array mixer 8.

[0039] The optical tower 4 is made of non-magnetic stainless steel, which is not affected by the high-intensity electromagnetic field of the tokamak. It is fixed with chemical bolts and internal sand filling to improve the stability of the tower. Multiple optical panels are welded on the tower to fix optical devices.

[0040] The optical panel is fixed with a second convex mirror 26, a third concave mirror 27, a seventh plane mirror 28, an eighth plane mirror 29, and a parabolic mirror 6. The light emitted from the stage optical path passes sequentially through the second convex mirror 26, the third concave mirror 27, the seventh plane mirror 28, and the eighth plane mirror 29, and then passes through the parabolic mirror 6 to turn the beam into a wider parallel beam, and then enters the plasma 9 of the tokamak device through the device window 30.

[0041] After passing through the plasma 9, the beam exits through the lower window and is incident on the 45-degree angle reflector 31 fixed on the optical support 5. The 45-degree angle reflector 31 returns the probe light to the fifth plane reflector 21 on the optical platform 1, and then enters the linear array mixer to be combined with the reference light to generate intermediate frequency signals at multiple points.

[0042] like Fig. 3 As shown, the parallel light has very short intervals between different positions (a, b, c, d) in plasma 9. After passing through plasma 9, the beam is focused by the focusing mirror in front of the detector to hit the four detector probes. The outer boundary of the beam just covers the outer boundaries of probes a and d, so the line integral electron density of the four plasma 9 points a, b, c, and d can be obtained at the same time, which has extremely high spatial resolution.

[0043] The base frequency of the first far-infrared light source 2 and the second far-infrared light source 3 is the same, and a micro frequency adjustment of the first far-infrared light source 2 in the order of megahertz makes a frequency difference between the two far-infrared light sources in the order of megahertz, so that the frequency mixer obtains an intermediate frequency signal in the order of megahertz. The two far-infrared light sources can be electrically excited HCN lasers, optically pumped terahertz gas lasers, terahertz solid frequency doubling sources or other continuous wave terahertz laser light sources.

[0044] The line array mixer 8 is an integrated array detector of a plurality of single-point mixers, the probe diameter is less than 2 mm, the number of probes can be 2 to tens according to requirements, and the center distance between the probes is less than 2.5 mm. High spatial resolution measurement better than 2.5 mm can be realized in far-infrared interferometric measurement.

[0045] Working principle: two far-infrared lasers with constant difference frequency are used as far-infrared laser light sources, a heterodyne signal is generated by a double-laser method, and a heterodyne interferometer optical path is used for plasma 9 electron density measurement; the interferometer uses a line array mixer 8, an optical tower 4, a parabolic mirror 6 and other devices, and reasonable optical design is performed, so that a system layout of multi-position detection under a single detection channel optical path is realized, and a reliable measurement tool is provided for high spatial resolution measurement of plasma electron density on a compact tokamak fusion experimental device.

[0046] The above describes one embodiment of the present application in detail, but the content is only the preferred embodiment of the present application, and cannot be considered as limiting the scope of the present application. Any equivalent changes and improvements made according to the scope of the present application should still belong to the scope of the present application.

Claims

1. A high spatial resolution far infrared laser interferometer characterized by, It comprises an optical platform (1), an optical tower (4), an optical support (5) and a phase comparator system; The optical platform (1) is fixedly installed with a far-infrared laser light source, a heterodyne interferometer table light path, a single-point frequency mixer (7) and a linear array frequency mixer (8); The far-infrared laser light source comprises a first far-infrared light source (2) and a second far-infrared light source (3); the light signal sending ends of the first far-infrared light source (2) and the second far-infrared light source (3) are connected with the heterodyne interferometer table light path, and the far-infrared laser light emitted by the two far-infrared light sources enters the single-point frequency mixer (7) through the interferometer table light path; the linear array frequency mixer (8) is used as a detection channel frequency mixer and is used for receiving the signals emitted by the two far-infrared light sources; the signal emitted by the first far-infrared light source (2) directly enters the linear array frequency mixer (8), and the detection light beam emitted by the second far-infrared light source (3) is emitted to the optical tower (4) beside the device, so that the detection light beam enters the plasma (9) through the optical tower (4), returns to the heterodyne interferometer table light path of the optical platform (1) after passing through the plasma (9), and then enters the linear array frequency mixer (8); the reference signal obtained by the single-point frequency mixer (7) and the multi-point detection signal obtained by the linear array frequency mixer (8) enter the phase comparator system for phase calculation at the same time, so as to obtain the electron density values of the plasma (9) at multiple points; The linear array frequency mixer (8) has multiple probes with close intervals, which are used to obtain intermediate frequency signals of multiple close points of the detection beam; The optical tower (4) is welded with multiple optical panels for fixing optical devices, and the optical panels are fixed with a second convex mirror (26), a third concave mirror (27), a seventh plane mirror (28), an eighth plane mirror (29) and a parabolic mirror (6); the light emitted by the heterodyne interferometer table light path passes through the second convex mirror (26), the third concave mirror (27), the seventh plane mirror (28) and the eighth plane mirror (29) in sequence, and then passes through the parabolic mirror (6) to change the light beam into parallel light with a wider width, and then enters the plasma (9) of the tokamak device; The linear array frequency mixer (8) is an integrated array detector of multiple single-point frequency mixers (7).

2. A high spatial resolution far infrared laser interferometer according to claim 1, characterized in that The heterodyne interferometer table light path comprises a first converging lens (10), a first beam splitter (11), a second beam splitter (12), a second converging lens (13), a third converging lens (14), a third beam splitter (15), a fourth beam splitter (16), a first plane mirror (17), a second plane mirror (18), a third plane mirror (19), a fourth plane mirror (20), a fifth plane mirror (21), a sixth plane mirror (22), a first convex mirror (23), a first concave mirror (24) and a second concave mirror.

3. A high spatial resolution far infrared laser interferometer according to claim 2, characterized in that The light signal sending end of the first far infrared light source (2) is connected with the receiving end of the single-point frequency mixer (7) through the first converging lens (10), the first light splitting plate (11), the second light splitting plate (12) and the second converging lens (13) in sequence; the light signal sending end of the first far infrared light source (2) is connected with the receiving end of the linear array frequency mixer (8) through the first converging lens (10), the first light splitting plate (11), the fourth light splitting plate (16), the second concave mirror in sequence.

4. A high spatial resolution far infrared laser interferometer according to claim 2, characterized in that The light signal sending end of the second far infrared light source (3) is connected with the receiving end of the single-point frequency mixer (7) through the third converging lens (14), the third light splitting plate (15), the second light splitting plate (12) and the second converging lens (13) in sequence; the light signal sending end of the second far infrared light source (3) is connected with the optical tower (4) through the third converging lens (14), the third light splitting plate (15), the first plane mirror (17), the second plane mirror (18), the third plane mirror (19), the first convex mirror (23), the first concave mirror (24) and the fourth plane mirror (20) in sequence.

5. A high spatial resolution far infrared laser interferometer according to claim 2, wherein The fifth plane mirror (21) and the sixth plane mirror (22) are used for receiving the detected light beam after passing through the plasma (9), and the light beam will be connected with the linear array frequency mixer (8) through the fifth plane mirror (21), the sixth plane mirror (22), the fourth light splitting plate (16) and the second concave mirror in sequence.

6. A high spatial resolution far infrared laser interferometer according to claim 1, characterized in that The optical tower (4) is made of non-magnetic stainless steel and is not affected by the high-strength electromagnetic field of the tokamak, is fixed by using chemical bolts, and the inside is filled with sand to improve the stability of the optical tower (4).

7. A high spatial resolution far infrared laser interferometer according to any one of claims 1-6, characterized in that The fundamental frequency of the first far infrared light source (2) and the second far infrared light source (3) is the same, and a frequency difference of the order of megahertz is generated between the two far infrared light sources through the micro-frequency adjustment of the order of megahertz of the first far infrared light source (2), so that the frequency mixer obtains a middle frequency signal of the order of megahertz.

8. A high spatial resolution far infrared laser interferometer according to any one of claims 1-6, characterized in that The probe diameter of the integrated array detector is less than 2mm, the number of probes is 2-20, and the center distance between probes is less than 2.5mm.

Images