JPS62113104A - Mirror for high luminance radiant light - Google Patents

Abstract

PURPOSE:To obtain a mirror for high luminance radiant light having high heat conductivity, a low coefft. of thermal expansion and high radiation resistance by which the mirror can safely be exposed to a high luminance radiant light source, by using a substrate of sintered silicon carbide ceramics contg. beryllia (BeO) and having high heat conductivity. CONSTITUTION:A substrate of sintered silicon carbide (SiC) ceramics contg. 1-10wt% beryllia and having high heat conductivity is used. The substrate is formed by sintering silicon carbide powder mixed with beryllia at 2,050 deg.C for 1hr in vacuum under 300kg/cm<2> pressure. The relative density of the substrate is >=98% and pores are hardly present in the substrate. The surface of the substrate is mirror-polished to <=10Angstrom surface roughness with diamond. Thus, a mirror for high luminance radiant light having high heat conductivity, a low coefft. of thermal expansion and satisfactory radiation resistance is obtd.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a mirror for high-intensity synchrotron radiation, coherent radiation, etc., and particularly to a front reflector used near a light emitting point. The present invention relates to a mirror for high-intensity synchrotron radiation suitable for.

[Background of the invention]

Reflectors, which are frequently used as optical elements in high-brightness radiation sources such as synchrotron radiation and coherent radiation, are required to be able to withstand large heat loads and radiation loads. For example, in synchrotron radiation with a brightness of 30W/(miraradian)2, the heat flow at a point 1m from one emission point is 3kW.
/ad is reached.

In particular, in reflective mirrors, such as front deflector mirrors, where synchrotron radiation first enters, the reflectance may decrease due to thermal distortion, radiation damage, etc.
Misalignment of the optical axis becomes a major problem.

The higher the thermal conductivity and the lower the coefficient of thermal expansion.

It has low thermal strain and can withstand larger heat loads, making it suitable as a substrate material for synchrotron radiation reflectors.

Furthermore, it must be stable against heat and radiation, and must be able to be processed into a mirror surface with high precision.

Conventionally, reflective mirrors for synchrotron radiation have been made by chemical vapor deposition of silicon carbide on a copper, synthetic quartz, or artificial graphite substrate, or by chemical vapor deposition of silicon carbide on a silicon carbide substrate for structural materials, and using these as substrates. Gold on mirror surface.

Materials coated with platinum or the like have been used. (For example, optical engineering
NGINEERING), vol. 17, 504-511
Pages, and Proceedings of 5PIE
, vol. 315, pp. 123-130. ) Their thermal conductivity and thermal expansion coefficient are shown in Table 1.

Copper in Table 1 is characterized by extremely high thermal conductivity, but also has a high coefficient of thermal expansion, so it has the disadvantage of being susceptible to thermal strain. Synthetic quartz is characterized by the fact that a highly accurate mirror surface can be easily obtained. However, it has the drawbacks of being susceptible to thermal distortion due to its low thermal conductivity, and being physically and chemically unstable when exposed to large amounts of heat and radiation due to its glassy nature. Artificial graphite and silicon carbide for structural materials are physically and chemically stable, but their thermal conductivity is 1/6 to 1/1 that of copper.
2, mirrors that are exposed to large amounts of heat and radiation have the disadvantage of causing thermal distortion, resulting in a decrease in reflectance and misalignment of the optical axis. There has been no material that simultaneously satisfies high thermal conductivity, low thermal expansion, and radiation resistance.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a mirror for high-brightness synchrotron radiation that has high thermal conductivity, low thermal expansion, and radiation resistance and can be used with high-brightness radiation light sources.

[Summary of the invention]

The gist of the present invention is a mirror for high-intensity synchrotron radiation, characterized in that a highly thermally conductive silicon carbide ceramic sintered with beryllia (BeO) added thereto is used as a substrate.

Generally, mirrors for high-brightness synchrotron radiation must have high thermal conductivity, low thermal expansion, and radiation resistance.

In general, ceramics are physically and chemically stable, have excellent radiation resistance, and are well known for having low thermal expansion. The present invention relates to a synchrotron radiation mirror whose substrate is made of highly thermally conductive silicon carbide ceramics sintered with the addition of beryllia. In other words, the thermal conductivity of high thermal conductivity silicon carbide ceramics sintered with the addition of beryllia is 270 W/m・℃, which is 1.6 times higher than that of artificial graphite and 4 times higher than that of silicon carbide for structural materials, and the coefficient of thermal expansion is 270 W/m・℃. is 3.7X
It is as small as 10-81/'C and is extremely effective as a mirror substrate for synchrotron radiation.

Highly thermally conductive silicon carbide ceramics sintered with the addition of beryllya have a relative density of 98% or more, so polishing methods such as diamond lapping can be used to obtain a mirror surface sufficient to completely reflect the radiation. It is possible. In order to obtain a more precise mirror surface, it is effective to form silicon carbide on the surface of beryllia-doped silicon carbide by chemical vapor deposition and then mirror polish it.

Further, the wavelength dependence and the incident angle dependence of reflectance largely depend on the reflective surface element. For example, when using a mirror as a filter to remove xB with a wavelength of several angstroms or less, light elements are advantageous, and conversely, in order to increase the reflectance of X-rays with a wavelength of several angstroms or less, heavy elements are advantageous. . Therefore, depending on the purpose of use, a vapor-deposited film of heavy elements can be deposited on a mirror surface with a thickness of 50 to 11,000 nm.
It is effective to form and use it.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which a synchrotron radiation mirror is used as a front mirror to reflect synchrotron radiation. The synchrotron radiation 7 emitted from the electron storage ring 6 is reflected by the synchrotron mirror 2, and is guided to the experimental apparatus 8.

The substrate 1 is made of high thermal conductivity silicon carbide ceramics, and 300 kg of silicon carbide powder added with 2% beryllia is packed in a vacuum.
It was created by sintering at 2050° C. for 1 hour under pressure conditions of /cnf. In this state, the relative density of the substrate is 98% or more, and there are almost no pores.

The mirror surface 2 is polished to a surface roughness of 10 Å or less by diamond polishing.

The thermal conductivity of this substrate at room temperature was 270 W/m·°C, and the coefficient of thermal expansion was 3.7×10 −81/′C.

The reflectance of the thus manufactured mirror at an incident angle of 89 degrees for synchrotron radiation with a wavelength of 1.2 nm was measured and the results were 1 reflectance 7
It showed a high reflectance of 7% and was proved to be suitable as a mirror for synchrotron radiation.

According to the mirror of this embodiment, since the thermal conductivity is high and the coefficient of thermal expansion is low, deformation of the mirror can be suppressed to a very small amount even if it is used for a long time with a high-intensity radiation light source.

At the same time, it is also possible to prevent deterioration of the mirror surface due to radiation irradiation. Furthermore, since no vapor deposited film is used on the mirror surface, there is no fear of the vapor deposited film peeling off due to heat or radiation.

In the above embodiment, the main elements of one reflecting mirror surface are silicon and carbon, which have different atomic numbers.

They are light elements 14 and 6. In cases where other elements (for example, heavy elements such as gold and platinum) are preferred as the elements of the reflective surface, as shown in the cross-sectional view shown in FIG.
The element is deposited in a thickness of 50"1000 nm onto a mirror surface of a highly thermally conductive silicon carbide ceramic substrate.

When a more dense reflective surface is required, as shown in the cross-sectional view of Figure 3, silicon carbide is further coated with an additional layer of 300 to 1000 μm on the surface of the high thermal conductivity silicon carbide ceramic.
m chemical vapor deposition and mirror polishing by diamond lapping, or as shown in Figure 4.
Further, 50 to 1 heavy elements are added to the mirror surface of this chemical vapor deposited silicon carbide.
It is also possible to use a material deposited with a thickness of 1000 nm.

〔Effect of the invention〕

According to the present invention, a mirror for high-intensity synchrotron radiation with high thermal conductivity, low coefficient of thermal expansion, and good radiation resistance can be manufactured, so it can be suitably used for a front mirror near the light emitting point and can be used for one reflection. It is also extremely effective in stabilizing synchrotron radiation and extending the life of mirrors.

[Brief explanation of drawings]

Claims (1)

[Claims] 1. A mirror for high-intensity synchrotron radiation, characterized in that the substrate is made of highly thermally conductive silicon carbide (SiC) ceramics sintered with 1 to 10% by weight of beryllia (BeO) added thereto. 2. A mirror for high-intensity radiation according to claim 1, characterized in that a reflecting mirror surface made of a heavy element vapor-deposited film is provided on the substrate. 3. A high-intensity synchrotron radiation mirror according to claim 1, characterized in that a chemical vapor deposited silicon carbide film is provided on the substrate. 4. A mirror for high-intensity radiation according to claim 3, characterized in that a reflective mirror surface made of a heavy element vapor-deposited film is provided on the surface of the chemical vapor-deposited silicon carbide film.