High-spatial-resolution far infrared laser interferometer

Abstract

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

Description

Technical Field

[0001] The invention relates to the technical field of optical interferometers, and in particular to a high spatial resolution far-infrared laser interferometer. Background Art

[0002] Far-infrared laser interferometer is a conventional diagnosis that uses the propagation characteristics of electromagnetic waves in plasma to measure the electron density of plasma. With the deepening of tokamak research, plasma parameters are gradually improved, and the requirements for far-infrared laser interferometer diagnostic technology are gradually increasing. Far-infrared laser interferometer has been rapidly developed and applied in recent years. Its technical development is mainly reflected in two points: the first point is that the improvement of the structure and performance of the far-infrared laser interferometer itself can meet more requirements of tokamak devices with different parameters. This is achieved through the performance improvement and overall coordination of all equipment components of the interferometer. For example, the development of compact far-infrared interferometer system can reduce the space occupied by the interferometer system, making the application of the far-infrared interferometer system more flexible; the development of high-speed rotating grating or dual laser system to improve the time resolution of the interferometer system can meet the needs of tokamak devices for high time resolution; the development of short-wavelength terahertz light source can meet the needs of high-density plasma measurement, etc. The second point is that the far-infrared laser interferometer system can be applied to different experimental devices, such as low-temperature plasma devices, plasma density measurement of rocket tail flames, etc., so that the far-infrared laser interferometer is not limited to diagnosis only on magnetic confinement fusion devices, but also has application value in other fields.

[0003] At present, some compact tokamak fusion experimental devices (such as spherical tokamak experimental devices) require far-infrared laser interferometers with high spatial resolution to detect the plasma density distribution under high spatial resolution and conduct physical experimental analysis due to their small vacuum chambers, small plasma size and large density gradient. However, the vacuum chamber of the compact tokamak is small, the diagnostic window size is limited, and the wavelength of the far-infrared laser is long, and the diameter of the detection beam is generally large, which makes it difficult to meet the multi-channel measurement requirements of the compact tokamak under high spatial resolution (millimeter level) performance.

[0004] It can be seen that how to develop a multi-channel, high spatial resolution, far-infrared laser interferometer for use in a compact tokamak small window has become a technical problem that researchers in this field are currently eager to solve. Summary of the invention

[0005] The purpose of the present invention is to provide a high spatial resolution far-infrared laser interferometer to solve the technical problem of high spatial resolution measurement of plasma electron density on a compact tokamak fusion experimental device. By using linear array detectors, optical towers, parabolic mirrors and other devices and performing reasonable optical design, a system layout of multi-position detection under a single detection optical path is realized, providing a reliable measurement tool for high spatial resolution measurement of plasma electron density.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A high spatial resolution far-infrared laser interferometer, comprising an optical platform, an optical tower, an optical bracket and a phase comparator system;

[0008] The optical platform is fixedly installed with a far-infrared laser light source, a heterodyne interferometer table optical path, a single-point mixer and a linear array mixer;

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

[0010] As a further solution of the present invention: the linear array mixer is provided with a plurality of closely spaced probes for obtaining intermediate frequency signals of a plurality of close points of the detection beam.

[0011] As a further solution of the present invention: the heterodyne interferometer table optical path includes a first condensing lens, a first beam splitter, a second beam splitter, a second condensing lens, a third condensing lens, a third beam splitter, a fourth beam splitter, a first plane reflector, a second plane reflector, a third plane reflector, a fourth plane reflector, a fifth plane reflector, a sixth plane reflector, a first convex mirror, a first concave mirror, and a second concave mirror.

[0012] As a further solution of the present invention: the optical signal sending end of the first far-infrared light source is connected to the receiving end of the single-point mixer through the first condensing lens, the first beam splitter, the second beam splitter and the second condensing lens in sequence; the optical signal sending end of the first far-infrared light source is connected to the receiving end of the linear array mixer through the first condensing lens, the first beam splitter, the fourth beam splitter and the second concave reflector in sequence.

[0013] As a further solution of the present invention: the optical signal sending end of the second far-infrared light source is connected to the receiving end of the single-point mixer through the third condensing lens, the third beam splitter, the second beam splitter and the second condensing lens in sequence; the optical signal sending end of the second far-infrared light source is connected to the receiving end of the single-point mixer through the third condensing lens, the third beam splitter, the first plane reflector, the second plane reflector, the third plane reflector, the first convex reflector, the first concave reflector and the fourth plane reflector in sequence to emit the light beam to an optical tower at a farther distance.

[0014] As a further solution of the present invention: the fifth plane reflector and the sixth plane reflector are used to receive the detection light beam after passing through the plasma. The light beam will pass through the fifth plane reflector, the sixth plane reflector, the fourth beam splitter, the second concave reflector in sequence, and be connected to the linear array mixer.

[0015] As a further solution of the present invention: the optical tower is made of non-magnetic stainless steel and is not affected by the high-intensity electromagnetic field of the tokamak. It is fixed with chemical bolts and filled with sand inside to improve the stability of the optical tower. A plurality of optical panels for fixing optical devices are welded on the optical tower.

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

[0017] As a further solution of the present invention: the fundamental frequencies of the first far-infrared light source and the second far-infrared light source are the same, and through a tiny frequency adjustment of the first far-infrared light source in the megahertz range, a frequency difference in the megahertz range is generated between the two far-infrared light sources, so that the mixer obtains an intermediate frequency signal in the megahertz range.

[0018] As a further solution of the present invention: the line array mixer is an integrated array detector of multiple single-point mixers, the probe diameter of which is less than 2 mm, the number of probes can be 2-20 according to demand, and the probe center spacing is less than 2.5 mm.

[0019] Beneficial effects of the present invention:

[0020] (1) Using a compact array detector, which is small in size and compact in structure, it can detect multiple points of a single parallel beam and achieve high spatial resolution measurement of multiple channels under a single detection beam.

[0021] (2) An optical tower is used to separate the detection beam system from the device, avoiding the influence of device vibration on the optical system; the optical devices of the upper and lower windows of the device are fixed on the optical bracket, which is convenient for optical design and optical debugging.

[0022] (3) The parabolic mirror cooperates with the optical tower to convert the detection light into parallel light that passes through the plasma in the center of the device, realizing multi-point measurement under the condition of limited window size, improving the spatial resolution and saving the precious diagnostic window. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] Figure 1 It is a schematic diagram of the overall structure of a high spatial resolution far-infrared laser interferometer of the present invention;

[0025] Figure 2 It is a plan view of a high spatial resolution far-infrared laser interferometer of the present invention;

[0026] Figure 3 It is a schematic diagram of the principle of using a compact array detector to perform high spatial resolution detection in the present invention.

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

[0028] The following will be combined with the drawings in the embodiments of the present invention / invention to clearly and completely describe the technical solutions in the embodiments of the present invention / invention. Obviously, the described embodiments are only part of the embodiments of the present invention / invention, not all of them. Based on the embodiments of the present invention / invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention / invention.

[0029] In the description of the present invention / invention, it should be understood that the terms "upper", "lower", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, and a specific direction structure and operation, and therefore, cannot be understood as a limitation on the present invention. In addition, "first" and "second" are only for descriptive purposes, 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" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] See also Figure 1-Figure 3 As shown, the present invention is a high spatial resolution far-infrared laser interferometer, comprising an optical platform 1, a first far-infrared light source 2, a second far-infrared light source 3, a heterodyne interferometer table optical path, an optical tower 4, an optical bracket 5, a parabolic mirror 6, a single-point mixer 7, a linear array mixer 8, and a phase comparator system;

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

[0033] There are two far-infrared laser light sources: a first far-infrared light source 2 and a second far-infrared light source 3. The optical signal sending ends of the first far-infrared light source 2 and the second far-infrared light source 3 are connected to the optical path of the interferometer table. The far-infrared lasers emitted by the two far-infrared light sources enter the single-point mixer 7 through the optical path of the heterodyne interferometer table. The single-point mixer 7 serves as a reference channel mixer and is the basis for the phase comparison calculation of the interferometer system; the linear array mixer 8 with multiple probes arranged linearly serves 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, and the detection beam emitted by the second far-infrared light source 3 is emitted to the optical tower 5 next to the device. The detection beam enters the plasma 9 through the optical tower 5, returns to the optical path of the optical platform table 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 simultaneously enter the phase comparison system for phase calculation, so that the electron density values ​​of the plasma 9 at multiple points can be obtained.

[0034] The reference channel mixer and the detection channel mixer are used to combine the light beams emitted by the two light sources received by each other to obtain an interference signal, so as to provide a sinusoidal intermediate frequency signal required for the calculation of the plasma electron density and accurately calculate the plasma electron density. The linear array mixer 8 has multiple probes with close spacing, which can obtain intermediate frequency signals of multiple close points of the detection beam, so that the interferometer system has a high spatial resolution measurement performance.

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

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

[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 through the third condensing lens 14, the third beam splitter 15, the second beam splitter 12 and the second condensing lens 13 in sequence; the optical signal transmitting end of the second far-infrared light source 3 transmits the light beam to the optical tower 4 which is farther away through the third condensing lens 14, the third beam splitter 15, the first plane reflector 17, the second plane reflector 18, the third plane reflector 19, the first convex reflector 23, the first concave reflector 24 and the fourth plane reflector 20 in sequence.

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

[0039] The optical tower 4 is made of non-magnetic stainless steel, is not affected by the high-intensity electromagnetic field of the Tokamak, is fixed with chemical bolts, and is filled with sand inside to improve the stability of the tower. A plurality of optical panels are welded on the tower to fix the optical devices;

[0040] The optical panel is fixed with a second convex mirror 26, a third concave mirror 27, a seventh plane reflector 28, an eighth plane reflector 29, and a parabolic mirror 6; the light emitted from the table optical path passes through the second convex mirror 26, the third concave mirror 27, the seventh plane reflector 28, and the eighth plane reflector 29 in sequence, and then is converted into parallel light with a wider width by the parabolic mirror 6, and then enters the plasma 9 of the tokamak device through the device window 30.

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

[0042] like Figure 3 As shown, the distance between the parallel light at different positions (a, b, c, d) in the plasma 9 is very short. After passing through the plasma 9, the focal length is adjusted by the focusing mirror in front of the detector, and the light beam signal is hit on the four detector probes. The outer boundary of the light beam just covers the outer boundaries of the two probes a and d, so the line integrated electron density of the four plasma 9 points a, b, c, and d can be obtained at the same time, with extremely high spatial resolution.

[0043] The fundamental frequencies of the first far-infrared light source 2 and the second far-infrared light source 3 are the same. Through the micro-frequency adjustment of the first far-infrared light source 2 in the order of megahertz, a frequency difference in the order of megahertz is generated between the two far-infrared light sources, so that the 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 linear array mixer 8 is an integrated array detector of multiple single-point mixers, the probe diameter is less than 2 mm, the number of probes can range from 2 to more than ten according to demand, the probe center spacing is less than 2.5 mm, and high spatial resolution measurement better than 2.5 mm can be achieved in far-infrared interferometry.

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

[0046] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A high spatial resolution far-infrared laser interferometer, characterized in that: It comprises an optical platform (1), an optical tower (4), an optical bracket (5) and a phase comparator system; A far-infrared laser light source, a heterodyne interferometer table optical path, a single-point mixer (7) and a linear array mixer (8) are fixedly mounted on the optical platform (1); The far-infrared laser light source comprises a first far-infrared light source (2) and a second far-infrared light source (3); the optical signal sending ends of the first far-infrared light source (2) and the second far-infrared light source (3) are connected to the optical path of the heterodyne interferometer table, and the far-infrared lasers emitted by the two far-infrared light sources enter the single-point mixer (7) through the optical path of the interferometer table; the linear array mixer (8) serves as a detection channel mixer, and is used to receive signals emitted by the two sources, and the signal emitted by the first far-infrared light source (2) directly enters the linear array mixer (8). ), a detection light beam emitted by a second far-infrared light source (3) is emitted to an optical tower (4) next to the device, and the detection light beam enters a plasma (9) through the optical tower (4), and after passing through the plasma (9), returns to the optical path of the heterodyne interferometer table of the optical platform (1), and then enters a linear array mixer (8); a reference signal obtained by the single-point mixer (7) and a multi-point detection signal obtained by the linear array mixer (8) simultaneously enter a phase comparator system for phase calculation, and obtains electron density values ​​of the plasma (9) at multiple points.

2. A high spatial resolution far-infrared laser interferometer according to claim 1, characterized in that: The linear array mixer (8) is provided with a plurality of closely spaced probes for obtaining intermediate frequency signals at a plurality of close points of the detection beam.

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

4. A high spatial resolution far-infrared laser interferometer according to claim 3, characterized in that: The optical signal sending end of the first far-infrared light source (2) is connected to the receiving end of the single-point mixer (7) through the first condenser lens (10), the first beam splitter (11), the second beam splitter (12) and the second condenser lens (13) in sequence; and the optical signal sending end of the first far-infrared light source (2) is connected to the receiving end of the line array mixer (8) through the first condenser lens (10), the first beam splitter (11), the fourth beam splitter (16) and the second concave reflector in sequence.

5. The high spatial resolution far-infrared laser interferometer according to claim 3, characterized in that: 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) through the third condensing lens (14), the third beam splitter (15), the second beam splitter (12) and the second condensing lens (13) in sequence; the optical signal transmitting end of the second far-infrared light source (3) transmits the light beam to the optical tower (4) at a relatively long distance through the third condensing lens (14), the third beam splitter (15), the first plane reflector (17), the second plane reflector (18), the third plane reflector (19), the first convex reflector (23), the first concave reflector (24) and the fourth plane reflector (20) in sequence.

6. The high spatial resolution far-infrared laser interferometer according to claim 3, characterized in that: The fifth plane reflector (21) and the sixth plane reflector (22) are used to receive the detection light beam after passing through the plasma (9), and the light beam will sequentially pass through the fifth plane reflector (21), the sixth plane reflector (22), the fourth beam splitter (16), and the second concave reflector to be connected to the line array mixer (8).

7. The 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-intensity electromagnetic field of the Tokamak. It is fixed using chemical bolts and filled with sand to improve the stability of the optical tower (4). A plurality of optical panels for fixing optical devices are welded to the optical tower (4).

8. The high spatial resolution far-infrared laser interferometer according to claim 7, characterized in that: A second convex mirror (26), a third concave mirror (27), a seventh plane reflector (28), an eighth plane reflector (29) and a parabolic mirror (6) are fixed on the optical panel; light emitted from the optical path of the heterodyne interferometer table passes through the second convex mirror (26), the third concave mirror (27), the seventh plane reflector (28), and the eighth plane reflector (29) in sequence, and then is converted into parallel light with a wider width by the parabolic mirror (6), and then enters the plasma (9) of the tokamak device.

9. A high spatial resolution far-infrared laser interferometer according to any one of claims 1 to 8, characterized in that: The fundamental frequencies of the first far-infrared light source (2) and the second far-infrared light source (3) are the same, and a frequency difference of the order of megahertz is generated between the two far-infrared light sources through a micro-frequency adjustment of the order of megahertz of the first far-infrared light source (2), so that a frequency difference of the order of megahertz is generated, and a mixer obtains an intermediate frequency signal of the order of megahertz.

10. A high spatial resolution far-infrared laser interferometer according to any one of claims 1 to 8, characterized in that: The line array mixer (8) is an integrated array detector of multiple single-point mixers (7), the probe diameter of which is less than 2 mm, the number of probes can be 2-20 according to demand, and the probe center spacing is less than 2.5 mm.

Images