CN117250212A - X-ray refraction focusing and detecting system - Google Patents

Abstract

The invention relates to an X-ray refraction focusing and detecting system, which collects X-ray signals and detects the signals in a refraction focusing mode and comprises an array type X-ray refraction lens, an array type diaphragm and an X-ray detector. The array type X-ray refraction lens is used for carrying out high-gain focusing on parallel incident X-ray photons; the array diaphragm is used for limiting the size of a focal spot, improving the angular resolution and filtering out spatial noise particles irradiated on a square hole area of the non-array diaphragm; the X-ray detector converts the focused X-ray photons into electrical signals, and reads out information such as energy, time, position and the like of the photons. The invention realizes the detection of light-weight short-focal-length X-ray pulsar signals, and can be spliced in a modularized manner to form a large detection area.

Description

X-ray refraction focusing and detecting system

Technical field:

the invention belongs to the technical field of X-ray detection and application, and relates to an X-ray refraction focusing and detection system.

The background technology is as follows:

the X-ray refraction focusing and detecting system is a novel system for realizing X-ray photon focusing detection by utilizing the refraction principle, and when X-rays penetrate through a material to be refracted, the material is absorbed to cause attenuation, so that the lower the energy is, the greater the absorption attenuation is. The X-ray pulsar radiation is in power law spectrum distribution, and the radiation flux is weak, so that a large X-ray focusing and detecting area is required for realizing detection of low-energy X-ray photons, and the X-ray pulsar radiation can be formed by splicing a plurality of array lens units. In 2019, m.wujun et al, the swedish royal college of academy of technology, proposed the concept of array arrangement of refractive lenses to construct a hard X-ray telescope, which designed an array telescope structure based on the X-ray focusing performance of a single compound refractive lens on 13.5 keV. The invention designs a low-attenuation refractive lens structure by utilizing an X-ray low-attenuation material beryllium instead of a photoresist material which is not applicable to space environment and a silicon material which is widely used for a synchronous radiation source and has larger attenuation on X-rays at present aiming at the detection of soft X-ray signals of a low energy section, and develops a corresponding manufacturing technology. This is one of the main innovation points of the present invention, which is different from the international related work, and there is no document data of the array type X-ray refraction lens in China.

In 1996, the concept of X-ray complex refractive lenses was proposed, after which various materials and corresponding fabrication techniques were developed. But in addition to materials that match semiconductor processes, array type compound refractive lenses have not been made more efficiently on other materials (e.g., beryllium). The array type X-ray lens can carry out batch processing on the composite refractive lens of the beryllium material by adopting a hot pressing technology, and the use of the beryllium material and the development of a lens processing method are comprehensive manifestations of the light weight and low X-ray attenuation characteristics of the focusing unit of the X-ray telescope.

The X-ray refraction focusing and detecting system for pulsar navigation should have higher angular resolution, such as 1 or even higher, and the invention can provide technical support for the telescope with angular resolution. However, for the soft X-ray detection band (0.5-10 keV) required for pulsar navigation, the X-ray refractive focusing and detection system cannot focus all the energy at one point at the same time. In practice, detection for a broad spectrum will result in a larger focal spot at the focal plane of the detector, which reduces the angular resolution if photons of a large part of the energy are to be detected. Therefore, the photon detection efficiency and the angular resolution are comprehensively balanced, a diaphragm structure is arranged on the focal plane of the optimal energy design value, and the diaphragm is also an array type focusing characteristic. Further, to prevent the incidence of X-rays from non-lens areas on the plane of the lens array, an X-ray blocking layer is plated on these areas. The design is different from the design concept proposed by M.Wujun et al, the angular resolution of the telescope can be effectively improved, and the system is lighter.

Currently, an X-ray refraction focusing and detecting system is mainly used for focusing and microscopic imaging of an X-ray wave band of a synchrotron radiation source, and the beam size of the synchrotron radiation determines that the lens size is within 1 mm. In recent years, the concept of using a refractive lens for detecting hard X-ray photons is developed abroad, and the concept of constructing an array type X-ray refractive lens by using photoresist and combining a high-energy detector to form an X-ray telescope structure is proposed. Compared with the reflection-based X-ray focusing and detecting system on the existing X-ray telescope satellite projects NuSTAR and ASTRO-H, the weight is obviously reduced, the focal length is greatly shortened, and the load ratio requirement on X-ray space detection is greatly reduced. However, the photoresist material is difficult to be applied to the actual space environment for a long time due to the characteristics of the photoresist material, and at present, the overseas is in a conceptual stage, no report of space application is seen, and the technology tracking stage is in China.

The research of X-ray refraction lenses is carried out for more than ten years in China, the materials used are mainly aluminum, silicon, PMMA and photoresist, the corresponding processing technologies are laser drilling, deep reactive ion etching, extreme ultraviolet or X-ray lithography, and the lenses are mainly used for focusing hard X-ray photons on a synchrotron radiation source. The concept of using refractive lenses for pulsar soft X-ray signal detection has not been proposed or implemented in China.

The invention comprises the following steps:

the invention aims to provide an X-ray refraction focusing and detecting system which can realize light weight and short focal length and can be spliced in a modularized manner to form a large detecting area.

In order to achieve the above purpose, the invention adopts the following technical scheme:

an X-ray refractive focusing and detecting system, characterized in that: the device comprises an array type X-ray refraction lens, an array type diaphragm and an X-ray detector; the array type X-ray refraction lens is used for carrying out high-gain focusing on parallel X-rays; the array diaphragm is used for limiting the size of a focal spot, improving the angular resolution and filtering out the space noise particles irradiated on the non-hole area of the array diaphragm; the X-ray detector converts the focused X-ray photons into electric signals, and reads out the energy, time and position information of the photons.

The array type X-ray refraction lens is made of light element materials and is selected as Be materials; the array type X-ray refraction lens is composed of a plurality of tiny parabolic lenses, and each lens can focus parallel incident X-rays.

An array diaphragm is arranged between the array refractive lens and the X-ray detector, so that the size of a focal spot is limited, and the angular resolution is improved; the array diaphragm is manufactured by silicon wafer etching, film plating and bonding, the number of diaphragm holes is the same as that of the refracting lenses, and the optical axes of the array diaphragm and the refracting lenses are accurately coincident when the array diaphragm is installed.

The rear end of the array diaphragm is tightly attached to the X-ray detector, and light spots formed after passing through the array diaphragm can be detected by the X-ray detector; the X-ray detector selects a high time resolution, high energy resolution, silicon-based detector with position information readout.

After passing through the array type refracting lens, X-ray photons of pulsar radiation are focused, pass through the array type diaphragm hole, are converged on the focal plane of the X-ray detector, and are acquired by the X-ray detector.

The distance between the array type refraction lens and the X-ray detector is set to 25cm, so that 2keV X-ray photons are guaranteed to have high transmittance; for higher energy X-ray photons, the focal length through the array refractive lens is greater than 25cm; for the X-ray photons with lower energy, the focal length of the array type refractive lens is smaller than 25cm, and the highest-efficiency detection of the whole energy section of the soft X-ray photons of pulsar radiation is realized by adjusting the aperture size of the array type diaphragm.

Compared with the prior art, the invention has the following advantages and effects:

1. the invention relates to a light X-ray refraction focusing and detecting system with short focal length and modular splicing. The technical innovation is as follows:

(1) Light element material beryllium is selected to manufacture the X-ray refractive lens, and the weight of the X-ray refractive lens is reduced by more than 1 time compared with that of the existing system X-ray detection system.

(2) The design and optimization method of the low attenuation array type X-ray composite refraction focusing system can realize the high-efficiency detection of soft X-ray photons.

(3) The array type composite refractive lens is manufactured in batches by adopting a hot press forming technology, and the array type diaphragm and the silicon-based X-ray detector are configured, so that modular splicing can be realized.

(4) The X-ray refraction lens adopts an array microstructure, the focal length can be controlled within 25cm, and the short focal length is beneficial to the light miniaturization of the X-ray refraction focusing and detecting system.

2. Compared with the traditional Wolter-I type X-ray telescope based on a multilayer nested structure, the array type composite refractive lens has the characteristics that the X-ray telescope is required to be light and oriented to pulsar navigation, and the weight and the volume of the X-ray telescope are greatly reduced on the premise of ensuring the detection area due to the adoption of a light material and a short focal length mode.

3. One of the directions of the load development of the X-ray refraction focusing and detecting system applied to space engineering is that the manufacturing technology is simple and convenient, the cost is low, a large number of reflecting lenses are required to be nested in a high-precision mode by a Wolter-I type focusing system which is a traditional X-ray telescope for pulsar navigation, the requirements on the roughness and the surface type precision of the lenses are extremely high, the technical process complexity is high, the manufacturing difficulty is high, the cost is high, and the manufacturing cost is greatly reduced by reducing the implementation difficulty through a mature micro-nano manufacturing technology.

4. At present, the X-ray pulsar navigation technology is in a development stage, no practical and mature pulsar navigation terminal exists at home and abroad, and the X-ray refraction focusing and detecting system related by the invention can be suitable for pulsar navigation engineering application, has the advantages of small volume, light weight, short focal length and the like, and can effectively inhibit background and reduce power consumption.

Description of the drawings:

FIG. 1 is a block diagram of an X-ray refractive focusing and detecting system of the present invention;

FIG. 2 is a schematic cross-sectional view of an array diaphragm;

FIG. 3 is a schematic diagram of the principle of refractive X-ray focusing;

FIG. 4 is a schematic diagram of the principle of collimated X-ray focusing;

FIG. 5 is a schematic diagram of the working principle of a Wolter-I type X-ray focusing mirror.

The specific embodiment is as follows:

the present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. For ease of understanding, the specific examples described herein are intended to be illustrative of the invention and are not intended to be limiting.

The invention relates to an X-ray refraction focusing and detecting system, which comprises an array type X-ray refraction lens, an array type diaphragm and an X-ray detector, wherein the array type diaphragm is arranged on the front surface of the X-ray refraction lens; the array type X-ray refraction lens is used for carrying out high-gain focusing on parallel X-rays; the array diaphragm is used for limiting the size of a focal spot, improving the angular resolution and filtering out the space noise particles irradiated on the non-hole area of the array diaphragm; the X-ray detector converts the focused X-ray photons into electrical signals, and reads out information such as energy, time, position and the like of the photons.

The array type X-ray refractive lens is made of a light element material, which has a lower attenuation coefficient for soft X-rays, and is an ideal material for manufacturing the X-ray refractive lens, and is generally selected as Be material. The array type X-ray refraction lens is composed of a plurality of tiny parabolic lenses, and each lens can focus parallel incident X-rays.

An array diaphragm is arranged between the array refractive lens and the X-ray detector, so that the size of a focal spot is limited, and the angular resolution is improved. The array diaphragm is formed by etching a whole Bao Guipian, the number of diaphragm holes is the same as that of the refractive lenses, and the optical axes of the array diaphragm and the refractive lenses are accurately coincident when the array diaphragm is installed.

The rear end of the array diaphragm is tightly attached to the X-ray detector, and light spots formed after passing through the array diaphragm can be detected by the X-ray detector. The X-ray detector selects a high time resolution, high energy resolution, silicon-based detector with position information readout.

After passing through the array type refracting lens, X-ray photons of pulsar radiation are focused, pass through the array type diaphragm hole, are converged on the focal plane of the X-ray detector, and are acquired by the X-ray detector.

In order to realize the highest detection efficiency of the X-ray refraction focusing and detecting system on the X-ray pulsar on a soft X-ray energy section, and ensure that the detecting system has smaller space volume, the distance between the array type refraction lens and the X-ray detector is set to be 25cm, and the photon of 2keV is ensured to have high transmittance. For higher energy X-ray photons, the focal length through the array refractive lens is greater than 25cm; for the X-ray photons with lower energy, the focal length of the array type refractive lens is smaller than 25cm, and the highest-efficiency detection of the soft X-ray photons of pulsar radiation can be realized by adjusting the aperture size of the array type diaphragm. The invention relates to an X-ray refraction focusing and detecting system which consists of an array type X-ray refraction lens, an array type diaphragm and an X-ray detector.

An array type X-ray refraction lens (such as 100 microns of each caliber) realizes the focusing of parallel incident X-ray photons;

the array diaphragm is used for limiting the size of a focal spot, improving the angular resolution and shielding the space noise particles in the non-hole area of the array diaphragm;

the X-ray detector converts the focused X-ray photons into electrical signals, and reads out information such as energy, time, position and the like of the photons.

The working principle of the X-ray refraction focusing and detecting system is as follows: an array refractive lens, which is optimally designed for 2keVX rays, can be aligned to the pulsar to collect the X-ray photons it radiates. X-ray photons with energy of 2keV are focused by an array refractive lens, pass through the micropores of the array diaphragm, and are converged at the focal point (25 cm behind the lens). An array diaphragm is arranged at the focus, an X-ray detector is closely arranged, and X-ray photons can be captured by the X-ray detector through micropores of the array diaphragm. For X-rays with higher energy, the focusing effect of the lenses on them is not ideal, the focal distance is far, a focal spot is formed at a focal position of 25cm, and the larger the energy, the larger the focal spot is formed. At this time, the function of the array diaphragm is embodied, and since the angular resolution can be expressed by dividing the focal spot size by the focal length, controlling the aperture of the array diaphragm can limit the focal spot size, thereby controlling the angular resolution. If the pore size is 30 microns, the angular resolution is 20 angular seconds. Similarly, for X-rays with energies lower than 2keV, the focal length after passing through the lens is shorter than 25cm, so a focal spot will be formed also at 25cm, and high resolution can be achieved by controlling the aperture size of the array diaphragm. Meanwhile, the array diaphragm can also prevent non-parallel X-ray photons from entering the X-ray detector through the position of the non-lens on the array lens, thereby inhibiting background noise and improving the detection signal-to-noise ratio.

The following is a comparative analysis of the presently existing collimation type and Wolter-I type soft X-ray telescopes, and the X-ray refraction focusing and detecting system of the present invention.

1. The invention is compared with collimation type

The refraction type lens and the collimation type system are simple in physical structure, and the principle of collecting X-ray photons is shown in schematic diagrams 3 and 4. The refraction type X-ray detection system focuses the X-ray photons with a larger area by using a lens array, a multi-focus structure is formed on a focal plane, and a focal plane detector with the same area as the lens array is used for receiving the X-ray photon signals; whereas a collimator-type detection system limits the field of view of the X-ray photons to be received by means of a collimator, i.e. the field of view is limited by means of a collimator, and X-ray photons falling within the field of view are received by the detector. The detector area of the two detection systems is the upper limit of the detection area of the system.

The performances of the field of view, angular resolution, detection efficiency, noise level, etc. of the two types of X-ray detection systems are compared as follows. First, the field of view of the collimation type is determined by the depth-to-width ratio of the collimator structure, for example, the field of view of the HXMT satellite low-energy telescope in China is 1.6 degrees×6 degrees, while the refractive field of view is related to the size of the system by the size of the lens opening, and is generally selected to be in the range of a plurality of angles or even an angle second, so that the range of the sight direction of the pulsar can be covered. If the areas of the X-ray detectors used by the two detection systems are the same, the background noise levels of the two detection systems are equivalent, and the large-view-field detection system collects pulsar photon signals in a larger range, so that the signal to noise ratio of the pulsar signals can be seriously influenced, and the refraction type detection system can better shield various space particle noises due to the smaller view field and has higher signal to noise ratio. In the aspect of angle resolution, the focusing structure of the refraction type detection system is matched with a specially designed system structure, so that the angle resolution can be greatly improved, and the angle resolution of the refraction type detection system can be within 1 angle, and compared with a collimation type detection system, the refraction type detection system has an order of magnitude improvement. Finally, in terms of detection efficiency, assuming that the two types of detection systems use the same X-ray detector, then, because of refraction, the X-rays need to be focused through the lens array, some attenuation of the X-rays will occur, and for an X-ray photon energy of 2keV, about 61.8% of the X-ray photons will penetrate; and a layer of soft X-ray shielding film is arranged above the collimator and used for removing visible light and ultraviolet signals in the space and allowing soft X-rays to pass through, so that detection noise is reduced. The light shielding film of the HXMT satellite low-energy telescope is designed into an aluminum/polyimide/nickel screen three-layer structure, the thickness of the aluminum film is about 200nm and is used for blocking visible light, the thickness of the polyimide film is about 400nm, and the mechanical property of the light shielding film is mainly enhanced. The transmittance of the two materials to 2keVX rays is about 85%, and the final transmittance cannot be obtained without the duty cycle data of the nickel screen. If the duty cycle is considered to be 80%, the 2keV X-ray transmittance is about 68%.

2. Comparison of the invention with Wolter-type I

The principle of operation of a Wolter-I type X-ray detection system is shown in FIG. 5, which focuses on grazing incidence and increases the receiving area by a multi-layer nested approach. As the aperture of the focusing mirror increases, the glancing incidence angle of the X-rays increases and the reflection efficiency decreases. If the focal length is required to be short, the aperture of the focusing lens is necessarily limited on the premise of ensuring the efficiency.

The Wolter-I type and refractive type lens system is compared in terms of structure and performance. Firstly, according to the analysis, in terms of structure, as the lens area is large, and meanwhile, in order to realize the grazing incidence focusing of X-ray photons, the surface roughness requirement of the lens is extremely high and is about 0.5nm, so that the processing difficulty of Wolter-I type lens is great, the materials used for the large-area lens are more, and the overall weight of a detection system is increased by adding a plurality of layers of nested auxiliary structures such as hubs and the like; the refraction type focusing part is a light material lens, the lens is thin, the material density is low, the weight of the beryllium lens is less than 2g even if the detection area is 100mm multiplied by 100mm, the weight of the polyimide lens is similar, and the weight of the polyimide lens is far lower than that of a Wolter-I type focusing lens. In addition, the two focusing structures have different requirements on surface roughness, and the refractive lens surface roughness requirement is 1000 times lower than that of the reflective focusing lens. In addition, the refraction focusing mode can control the focal length by changing the size of the lens opening and the number of the lens units, so that the focal length is easily lower than 0.5m and is greatly lower than that of the Wolter-I type focusing lens by a plurality of meters, and therefore, the refraction focusing mode has more advantages in volume.

And secondly, comparing indexes such as the field of view, the angular resolution, the detection efficiency and the like. At a resolution of 30 "for a refractive index at 2keV energy, the field of view is 2.75', which is smaller than Wolter-I. In terms of resolution, a focusing mirror based on direct polishing of glass (Chandra telescope) has so far kept a record of resolution of 0.5 ", and a focusing mirror based on nickel electroformed lenses has also achieved a resolution of better than 30". Overall, both focusing mirrors can achieve 30 "angular resolution, with higher Wolter-type I performance.

Regarding detection efficiency, for Wolter-I type, it is mainly dependent on specular reflectance; for refractive types, the lens transmissivity is mainly dependent. Wolter-I uses paraboloids of revolution and hyperboloids of revolution for two reflections, assuming a focusing efficiency of 80% for the primary reflection, the total focusing efficiency of the two reflections is 64%; the transmissivity of a refractive lens is related to the lens material, the lens opening size, and the selected operating wavelength. The refraction lens designed by the invention uses beryllium, the opening size is 100 μm, and the photon energy is 2keV. The refractive lens transmittance was calculated to be about 61.8%. It can be seen that the focusing efficiency of the Wolter-type I lens is substantially comparable to that of the refractive lens. The Wolter-I type lens detection area also depends on the lens aperture and the number of nested layers; the refractive lens detection area is related to the size of the lens array in addition to the aperture of the lens.

In fact, the Wolter-I type has larger advantages in noise level, angular resolution capability and the like compared with the collimation type, but has the main defects that the volume weight is difficult to adapt to navigation load requirements, and the manufacturing difficulty is larger. In view of these problems, the present invention proposes a solution to a refractive focusing and detection system. The main significance is as follows:

(1) The light weight is a necessary feature of the pulsar navigation-oriented X-ray detection system, and compared with a Wolter-I type X-ray detection system based on a multilayer nested structure, the array type refraction lens has the advantages that the weight and the volume of the space X-ray detection system are greatly reduced on the premise of ensuring the detection area due to the adoption of a light material and a short focal length mode.

(2) The technical difficulty is reduced, which is one of the important directions of the development of pulsar navigation terminals, the Wolter-I type focusing system needs multi-layer lens nesting, the lens roughness requirement is very strict, the technical process complexity is high, the manufacturing difficulty is high, and the cost is high; the refractive lens system utilizes a mature micro-nano manufacturing technology to reduce the manufacturing cost by reducing the processing difficulty.

Compared with a Wolter-I type X-ray detection system, the X-ray refraction lens has great advantages in weight and volume, can be spliced into a required area in a modularized manner, and is easy to realize in high angle resolution. The weight and volume reduction in turn reduces the cost of satellite emissions. In addition, the manufacturing difficulty is reduced, the economic cost is also reduced, and the popularization of the application of the method is facilitated.

The foregoing description is only illustrative of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, and all changes that may be made in the equivalent structures described in the specification and drawings of the present invention are intended to be included in the scope of the invention.

Claims (6)

1. An X-ray refractive focusing and detecting system, characterized in that: the device comprises an array type X-ray refraction lens, an array type diaphragm and an X-ray detector; the array type X-ray refraction lens is used for carrying out high-gain focusing on parallel X-rays; the array diaphragm is used for limiting the size of a focal spot, improving the angular resolution and filtering out the space noise particles irradiated on the non-hole area of the array diaphragm; the X-ray detector converts the focused X-ray photons into electric signals, and reads out the energy, time and position information of the photons.

2. An X-ray refractive focusing and detecting system according to claim 1, wherein: the array type X-ray refraction lens is made of light element materials and is selected as Be materials; the array type X-ray refraction lens is composed of a plurality of tiny parabolic lenses, and each lens can focus parallel incident X-rays.

3. An X-ray refractive focusing and detecting system according to claim 1, wherein: an array diaphragm is arranged between the array refractive lens and the X-ray detector, so that the size of a focal spot is limited, and the angular resolution is improved; the array diaphragm is manufactured by silicon wafer etching, film plating and bonding, the number of diaphragm holes is the same as that of the refracting lenses, and the optical axes of the array diaphragm and the refracting lenses are accurately coincident when the array diaphragm is installed.

4. An X-ray refractive focusing and detecting system according to claim 1, wherein: the rear end of the array diaphragm is tightly attached to the X-ray detector, and light spots formed after passing through the array diaphragm can be detected by the X-ray detector; the X-ray detector selects a high time resolution, high energy resolution, silicon-based detector with position information readout.

5. An X-ray refractive focusing and detecting system according to claim 1, wherein: after passing through the array type refracting lens, X-ray photons of pulsar radiation are focused, pass through the array type diaphragm hole, are converged on the focal plane of the X-ray detector, and are acquired by the X-ray detector.

6. An X-ray refractive focusing and detecting system according to claim 1, wherein:

the distance between the array type refraction lens and the X-ray detector is set to 25cm, so that 2keV X-ray photons are guaranteed to have high transmittance; for higher energy X-ray photons, the focal length through the array refractive lens is greater than 25cm; for the X-ray photons with lower energy, the focal length of the array type refractive lens is smaller than 25cm, and the highest-efficiency detection of the whole energy section of the soft X-ray photons of pulsar radiation is realized by adjusting the aperture size of the array type diaphragm.