CN104852257A - Large-diameter laser liquid cooling mirror structure - Google Patents

Abstract

The invention discloses a large-caliber laser liquid cooling mirror structure which comprises a reflection panel, a distribution plate and a back plate, wherein a water inlet primary flow passage and a water outlet primary flow passage are arranged on the back surface of the distribution plate, and a water inlet secondary flow passage and a water outlet secondary flow passage which are distributed in parallel are arranged on the front surface of the distribution plate; the back plate is provided with a plurality of water inlet holes and water outlet holes; the front surface of the reflecting panel is a reflecting surface, and the back surface is a three-stage flow channel. The invention adopts the multi-stage cooling flow channel structure based on the interdigital flow channel, can provide cooling liquid with larger flow for transferring the heat deposited on the reflecting surface under smaller water pressure, simultaneously ensures that the pressure and the flow distribution of the cooling liquid in each micro flow channel are relatively uniform, and realizes more uniform heat dissipation on the reflecting surface, thereby inhibiting the overlarge thermal distortion of the large-caliber cavity mirror. The adjacent secondary flow channels are respectively communicated with the water inlet primary flow channel and the water outlet primary flow channel and are vertically stacked with the tertiary flow channels, and the flow resistance is greatly reduced because the flow does not need to flow through the whole long and thin tertiary flow channel.

Description

A Large Aperture Laser Liquid-cooled Mirror Configuration

technical field

The invention belongs to the field of laser optics, and specifically relates to a liquid-cooled reflector structure, in particular to a large-diameter laser liquid-cooled mirror configuration, which is mainly used for high-energy laser optical resonators and optical resonators with high requirements for high power density and surface shape accuracy. chain.

Background technique

The laser optical resonator mirror will absorb part of the energy when it is irradiated by laser light, which will cause the temperature of the mirror surface to rise. The wavefront is distorted, deteriorating the output beam quality and stability. Therefore, reducing the thermal distortion of the reflective surface and improving the accuracy of the surface shape are the keys to the development of high-power laser resonator mirrors. The current solution is mainly divided into three aspects: choose a base material with a low thermal expansion coefficient, so that the reflective surface has the smallest thermal deformation under the same amount of heat absorbed; coat the reflective surface with a high reflective film to improve the reflectivity and reduce the reflection of the mirror on the laser beam. Energy absorption rate; adopt active cooling technology to transfer the heat deposited on the reflective surface, thereby reducing its temperature rise. Since the choice of mirror body material is limited by the physical properties, optical processing performance and mechanical properties of the material, only a single method of optimizing the base material can no longer meet the special requirements of high-energy lasers for high beam quality; improving the reflectivity of the reflective surface is the most important Direct and effective means, but the current reflectivity has reached the technological limit of 99.99%, and it is still difficult to meet the growing demand for high power. Therefore, the use of active cooling technology to transfer the heat deposited on the mirror surface is considered to be the most important solution to the thermal deformation of laser resonator mirrors, especially high-power resonator mirrors.

Among various cooling technologies, liquid cooling technology is widely used due to its high heat transfer efficiency. In the existing liquid-cooled mirror structure, micro-flow channel arrays with cross-sectional dimensions ranging from millimeters to hundreds of microns are widely used. The micro-channel arrays can provide a large surface area/volume ratio, thereby enhancing the heat transfer effect and reducing the reflective surface. Thermal deformation. Moreover, the structure of the straight-through channel is simple, which is convenient for design and machining. However, due to the heat inlet effect in the straight channel, the heat transfer coefficient decreases with the increase of the inlet distance, and at the same time, affected by the flow resistance, the fluid has a pressure loss along the way. This causes temperature and pressure differences between the inlet and outlet of the fluid, resulting in uneven temperature on the reflective surface; in addition, for large-diameter laser reflectors, as the laser irradiation area becomes larger, the corresponding water-cooling area area also becomes larger, so the length of the flow channel Longer, the resistance along the way increases, and a higher supply pressure must be provided to maintain heat dissipation performance. In this case, fluid pressure can cause large mirror distortions.

U.S. Patent US4314742 proposes a laser mirror with multi-layered helical cooling channels. The multiple helical channels take the center of the mirror as the entrance and flow to the edge of the mirror. They have uniform heat transfer characteristics and are suitable for large diameters. The mirror surface of the mirror is cooled; but the cooling liquid will also encounter great resistance when flowing in the channel structure of the mirror body. Moreover, for difficult-to-process materials such as single crystal silicon, this structure is extremely difficult to process.

Contents of the invention

In view of the above, in order to solve the shortcomings of the existing design methods, the present invention proposes a large-diameter laser liquid-cooled mirror configuration with small cooling liquid flow resistance and easy processing.

In order to achieve the above object, the concrete technical scheme that the present invention adopts is as follows:

A design method for the configuration of a large-diameter laser liquid-cooled mirror, which is used in laser optical resonators and optical chains. By setting a number of intersecting interdigitated flow channels under the micro-channels, the cooling liquid in the micro-channels can be shortened. the flow distance. Interdigitated runners, also known as interdigitated runners or cross-combed runners, are a comb-shaped runner structure.

A large-diameter laser liquid-cooled mirror configuration, including a reflective panel, a distribution plate and a back plate, the back of the distribution plate has a number of primary water inlet channels and primary water outlet channels, and the front of the distribution plate has parallel Distributed water inlet secondary flow channels and water outlet secondary flow channels; there are a number of water inlet holes and water outlet holes on the back plate; the front of the reflective panel is a reflective surface, and the back is 0.1-2mm wide with a spacing of 0.1 -2mm tertiary flow channels; the reflective surface is the working surface, which is irradiated by the laser and reflects the laser light; the number of water inlet primary flow channels and water outlet primary flow channels on the back of the distribution plate are directly connected to the back plate The water inlet hole on the top is connected with the water outlet hole; the water inlet secondary flow channel is connected with the water inlet primary flow channel, the water outlet secondary flow channel is connected with the water outlet primary flow channel, and the water inlet secondary flow channel and the water inlet secondary flow channel are connected. The secondary flow channels of the outlet water are arranged at intervals on the distribution plate to form an interdigitated flow channel structure; the back of the reflective panel is attached to the front of the distribution plate, and the length direction of the tertiary flow channels on the reflective panel and the secondary flow channels on the distribution plate The length directions of the tracks are perpendicular to each other.

The cross-sectional shape of the three-stage flow channel in the present invention includes rectangle, trapezoid, triangle or semicircle.

The reflective panel, the distribution plate and the back plate of the present invention have the same plane outline shape, and the plane outline shape includes a circle or a regular polygon.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1. Since the present invention adopts the multi-stage cooling flow channel structure based on the interdigitated flow channel, it can provide a large flow of cooling liquid for transferring the deposition heat of the reflective surface under a small water pressure, and at the same time make the micro flow channels The pressure and flow distribution of the cooling liquid is relatively uniform, and a relatively uniform heat dissipation is realized on the reflective surface, thereby suppressing excessive thermal distortion of the large-diameter cavity mirror.

2. The adjacent secondary flow channels of the present invention communicate with the primary flow channel of the water inlet and the primary flow channel of the water outlet respectively, and vertically stack with the tertiary flow channels. As a key structure, the drainage function of the secondary flow channel makes the cooling liquid flow from the water inlet hole to the water outlet hole, without having to flow through the entire slender third-level flow channel, but only through the third-level flow channel located in two adjacent two The part between the stage flow channels, thus greatly reducing the flow resistance. In addition, due to the large cross-sectional size of the primary and secondary flow channels, the theoretical flow resistance is small, and the pressure loss along the cooling liquid is also small. The drop consistency is good, so as to ensure that the distributed flow is relatively uniform, and finally realize the relatively uniform heat transfer around the reflective surface.

3. Compared with the traditional straight channel liquid cooling mirror, the new configuration of the mirror body proposed by the present invention not only retains the advantages of high heat transfer efficiency of the fine flow channel, but also has small flow resistance, uniform flow rate and good heat transfer consistency And other characteristics, it is more suitable for large-aperture laser liquid-cooled mirrors.

4. Through the layered design, the present invention retains the straight channel structure and avoids excessive use of non-linear structure design, so that even if difficult-to-process materials such as single crystal silicon are used, the mirror can also be made by diamond grinding wheel circumferential grinding. Compared with chemical etching, electric discharge, grinding head grinding and other processing methods, this processing method has the advantages of high processing efficiency, easy control of precision and small tool wear.

5. The present invention is composed of a reflective panel, a distribution plate and a back plate stacked in sequence. The cooling flow on the back of the reflective panel directly plays a role in heat dissipation, and the liquid flow is driven by the pressure difference between adjacent interdigitated channels in the distribution plate. Through the specially designed interdigitated flow channel, the flow resistance of the cooling liquid is greatly reduced, and, through the layered design, even if difficult-to-machine materials such as monocrystalline silicon are used, the mirror body can be processed by traditional grinding processes.

Description of drawings

Figure 1 is an exploded view of the structure of the present invention.

Fig. 2 is a component diagram of a large-aperture laser liquid-cooled mirror configuration with interdigitated flow channels.

Fig. 3 is a flow field structure of a large-aperture laser liquid-cooled mirror configuration with interdigitated flow channels.

Fig. 4 is a nephogram of the temperature distribution on the reflective surface when the example of the present invention reaches thermal equilibrium.

Fig. 5 is a curve of thermal deformation on the reflective surface changing with radial distance in the x direction when the example of the present invention reaches thermal equilibrium.

Fig. 6 is a curve of thermal deformation on the reflective surface changing with radial distance in the y direction when the example of the present invention reaches thermal equilibrium.

In the figure: 1. Reflective panel, 2. Distribution plate, 3. Back plate, 11. Reflective surface, 12. Tertiary flow channel, 21. Secondary flow channel for water outlet, 22. Secondary flow channel for water inlet, 23. Inlet Water primary flow channel, 24, water outlet primary flow channel, 31, water outlet hole, 32, water inlet hole.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing. In the design scheme of the present invention, on the basis of retaining the fine channel cooling structure of the traditional direct-flow liquid-cooled mirror, an interdigitated channel structure is added to reduce the flow resistance of the mirror body, and improve the uniformity of the flow field and heat dissipation. Excessive thermal distortion of the entire reflective surface is avoided.

As shown in FIGS. 1-3 , the reflective surface 11 and the micro-channel heat dissipation structure are designed on the same panel, that is, the reflective panel 1 . The front side of the reflective panel 1 is plated with a high-reflection film as the reflective surface 11 for reflecting laser light, and the three-stage flow channels 12 made on the back are some fine straight channels for cooling the mirror body. The front of the distribution plate 2 is made with large cross-section flow channels parallel to each other, as the water inlet secondary flow channel 21 and the water outlet secondary flow channel 22. The water primary flow channel 23 communicates with the water outlet primary flow channel 24 . The cross-sectional dimensions of the primary water inlet channel 23 and the primary water outlet channel 24 are also very large, communicate with the water inlet hole 32 and the water outlet hole 31 respectively, and form the secondary water inlet channel 21 and the water outlet secondary channel 22. Interdigitated structure. Like this, water inlet hole 32→water inlet primary flow channel 23→water inlet secondary flow channel 21→tertiary flow channel 12→water outlet secondary flow channel 22→water outlet primary flow channel 24→water outlet 31 has just constituted cooling A flow path for liquids to enter and exit the lens body

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific implementation examples. Among them, the diameter of the mirror body is 300mm, the cross-section of the third-stage flow channel is rectangular, the width is 1mm, the depth is 2mm, and the spacing is 2mm. The water-cooling area formed by it is approximately circular and the diameter is 200mm; , the width is 4mm, wherein the depth connected with the water inlet primary flow channel 23 is 10mm, the depth connected with the water outlet primary flow channel 24 is 15mm, and the distance is 16mm; the primary flow channel section is also rectangular, and the hydraulic diameter is greater than The three-stage flow channel is more than 10 times; the diameter ratio of the water inlet hole 32 and the water outlet hole 31 is 1:2, so that the Reynolds number of the two holes can always be consistent; the total thickness of the assembled mirror body is 52.5mm; the mirror body material is Single crystal silicon; the laser irradiation area is a circular area with a diameter of 200mm and the center coincides with the center of the mirror surface. The power density absorbed by the reflective surface is 5000W/m2, the initial ambient temperature is 300K, and the total inlet flow rate is 62.8mL/s.

As shown in FIG. 4 , it is a nephogram of the temperature distribution on the reflective surface 11 when the large-aperture laser liquid-cooled mirror with interdigitated flow channels proposed in this embodiment reaches a steady state after receiving laser irradiation. The calculation results obtained by using the fluid-thermo-solid coupling analysis based on the finite volume method show that the maximum temperature rise of the reflecting surface is only 1.5K, while the maximum temperature rise difference in the irradiated area is less than 1K. This shows that the new configuration can achieve a lower and uniform temperature rise of the reflective surface 11 .

As shown in Fig. 5 and Fig. 6, when the large-aperture laser liquid-cooled mirror with interdigitated flow channels proposed in this embodiment reaches a steady state after receiving laser irradiation, the thermal deformation on the reflecting surface 11 is in the x and y directions Variation curve with radial distance. The calculation results obtained by using the flow-thermo-solid coupling analysis based on the finite volume method show that the maximum thermal deformation of the reflective surface is about 158nm, and the peak-to-valley value (the difference between the maximum value and the minimum value) of the thermal deformation in the irradiation area is 104nm, which is less than ten One of the oxygen iodine chemical laser wavelengths (1.31 μm), which meets the requirements for the use of oxygen iodine chemical lasers. In addition, the pressure drop at the inlet and outlet of the mirror body is only 80Pa. Compared with the traditional direct-flow water-cooled mirror of the same scale, the required water pressure is greatly reduced, and the influence on the mirror distortion is negligible.

Claims (3)

1. A large-diameter laser liquid-cooled mirror configuration is characterized in that: it comprises a reflective panel (1), a distribution plate (2) and a back plate (3), and the distribution plate (2) back has several The water inlet primary flow channel (23) and the water outlet primary flow channel (24), the distribution plate (2) front has parallel water inlet secondary flow channels (22) and water outlet secondary flow channels (21); There are several water inlet holes (32) and water outlet holes (31) on the back plate (3); the front side of the reflective panel (1) is a reflective surface (11), and the back side is a width of 0.1-2mm with a spacing of 0.1-2mm The three-stage flow channel (12); the reflective surface (11) is the working surface, which is irradiated by the laser light and reflects the laser light; the number of water inlet primary flow channels (23) on the back of the distribution plate (2) and The water outlet primary channel (24) directly communicates with the water inlet hole (32) and the water outlet hole (31) on the back plate (3); the water inlet secondary channel (22) communicates with the water inlet primary channel The flow channels (23) are connected, the water outlet secondary flow channel (21) is connected with the water outlet primary flow channel (24), and the water inlet secondary flow channel (22) and the water outlet secondary flow channel (21) are connected at the distribution plate (2 ) are arranged at intervals to form an interdigitated channel structure; the back of the reflective panel (1) is attached to the front of the distribution plate (2), and the length direction of the three-stage flow channel (12) on the reflective panel (1) and the distribution plate (2) The length directions of the secondary runners on the top are perpendicular to each other. 2. A large-aperture laser liquid-cooled mirror configuration according to claim 1, characterized in that: the cross-sectional shape of the tertiary flow channel (12) includes rectangle, trapezoid, triangle or semicircle. 3. A kind of large-aperture laser liquid-cooled mirror configuration according to claim 1, characterized in that: the plane profile shapes of the reflective panel (1), the distribution plate (2) and the back plate (3) are the same, Planar outline shapes include circles or regular polygons.