Patent Publication Number: US-11662484-B2

Title: Neutral atom imaging unit, neutral atom imager, neutral atom imaging method, and space detection system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefits of priority to Chinese Patent Application No. CN 2020110184647, entitled “Neutral Atom Imaging Unit, Neutral Atom Imager, Neutral Atom Imaging Method, and Space Detection System”, filed with CNIPA on Sep. 24, 2020, the contents of which are incorporated herein by reference in its entirety. 
     BACKGROUND 
     Field of Disclosure 
     The present disclosure relates to the field of neutral atom imaging, in particular, to a neutral atom imaging unit, a neutral atom imager, a neutral atom imaging method, and a space detection system. 
     Description of Related Arts 
     Holistic observation and global imaging have become one of the most promising approaches to solving geospatial physics issues. Energetic Neutral Atoms (ENA) are generated during the charge exchange process between ring current ions and geocorona hot particles. ENA is not bounded by magnetic fields and can leave the source area along a straight line at the speed of the initial energetic ion. Therefore, telemetry ENA imaging provides a new opportunity to distinguish the temporal and spatial changes of space plasma. 
     However, the development of space neutral atom detection technology has not been easy. The extremely strong extreme ultraviolet/ultraviolet radiation (EUV/UV) background existing in the space is the biggest obstacle to reliable ENA measurements. The space community has made unremitting efforts in the field of space neutral atom detection technology. 
     The first attempt at direct field observation of space ENA flux was the rocket carrying test on Apr. 25, 1968. The technology of the first ENA detection instrument is based on SSD foil-stripping technology, which makes ENA become positively charged particles again, and then analyzes the newly generated positively charged particles. The subsequent development of ENA detection technology was to add a diffraction filter to filter out the background of extreme ultraviolet/ultraviolet radiation, to increase the ratio of ENA to EUV/UV photons of the sensor. However, due to the extremely strong extreme ultraviolet/ultraviolet radiation in space, the flux of the neutral components would be reduced by 20 times while the diffraction filter attenuates the extreme ultraviolet/ultraviolet radiation by 100,000 times. Therefore, the problem is still not well resolved. 
     Traditional low-energy ENA detectors are generally made of channel multipliers, microchannel plates and diffraction filters. However, these ENA detectors are still seriously affected by ultraviolet radiation, and almost no scientifically valuable low-energy ENA detection results in near-Earth space have been obtained. 
     SUMMARY 
     The present disclosure provides a grid imaging unit, a neutral atom imager, a neutral atom imaging system and a neutral atom imaging method, to protect the ENA detectors from being affected by the extremely strong extreme ultraviolet/ultraviolet radiation, and realize the neutral atom imaging technology with high temporal and spatial resolution. 
     The first aspect of the present disclosure provides a neutral atom imaging unit, including at least one set of detection units, and the at least one set of detection units includes: 
     at least one semiconductor detector line array; and 
     at least one modulation grid, the at least one modulation grid is arranged in front of the at least one semiconductor detector line array and has a distance D from the semiconductor detector line array, and corresponds to the at least one semiconductor detector line array one to one, and the modulation grid performs Fourier transform on the incident neutral atom; 
     the modulation grid includes a slit and a slat forming the slit, the direction of the semiconductor detector line array is consistent with that of the slit of the modulation grid; the modulation grid includes a plurality of grid periods, each of the grid periods includes n slits, the width of the semiconductor detector line array is d, and the width (w i ) of the i-th slit of the modulation grid satisfies the following relationship: 
     
       
         
           
             
               w 
               i 
             
             = 
             
               
                 n 
                 i 
               
               × 
               
                 d 
                 . 
               
             
           
         
       
     
     Optionally, in each grid period, the width of the narrowest slit and the width of the slat forming the narrowest slit are the same as the width of the semiconductor detector line array. 
     Optionally, the lengths of the plurality of grid periods of the modulation grid are the same, the i-th slit in each grid period corresponds to the i-th slat, and the i-th slit has the same width as the i-th slat. 
     Optionally, the thickness t of the modulation grid satisfies: t≤¼d. 
     Optionally, the angular resolution of the neutral atom imaging unit is: 
     
       
         
           
             2 
             ⁢ 
             
               
                 arctan 
                 ⁡ 
                 
                   ( 
                   
                     d 
                     
                       2 
                       ⁢ 
                       D 
                     
                   
                   ) 
                 
               
               . 
             
           
         
       
     
     Optionally, the modulation grid includes m grid periods, m≥2 and n≥3. 
     Optionally, the neutral atom imaging unit further includes a collimation-and-deflection module. The collimation-and-deflection module is arranged in front of a modulation grid of at least one detection unit, and the collimation-and-deflection module includes a collimator and a deflection plate. 
     A second aspect of the present disclosure provides a neutral atom imager, including at least one imaging probe. The at least one imaging probe includes at least one neutral atom imaging unit provided in the first aspect of the present disclosure, at least one preamplifier unit, and at least one master-control-and-interface unit; the at least one neutral atom imaging unit, the at least one preamplifier unit, and the at least one master-control-and-interface unit are electrically connected to each other; 
     the at least one neutral atom imaging unit detects and images the neutral atoms; 
     the at least one preamplifier unit reads the imaging data of the at least one neutral atom imaging unit, and amplifies the imaging data. 
     Optionally, the at least one preamplifier unit includes a plurality of application-specific integrated circuits. The plurality of application-specific integrated circuits read the imaging signal of the at least one neutral atom imaging unit in real time and amplify the imaging signal. 
     Optionally, the preamplifier unit includes at least one charge-sensitive preamplifier, at least one multi-stage shaper, and at least one peak detector. The peak detector detects the peak value of the imaging signal and maintains the peak value until the peak value is read out. 
     Optionally, the at least one master-control-and-interface unit provides an operation timing to at least one application-specific integrated circuit, controls at least one application-specific integrated circuit to collect and read out the imaging signals, and preliminarily fuses and processes the imaging signal. 
     Optionally, the neutral atom imager further includes a data processing unit. The data processing unit receives the imaging signal transmitted by the preamplifier, and processes, packs, and compresses the imaging signal for storage. 
     Optionally, the neutral atom imaging unit in the at least one imaging probe is electrically connected with the data processing unit by using a master-control-and-interface unit as an interface. 
     Optionally, the imaging probe further includes at least one housing. The housing includes a base portion and a fan-shaped portion located above and fixedly connected to the base portion. 
     The collimation-and-deflection module of the neutral atom imaging unit in the imaging probe is provided on the fan-shaped portion. The outer panel of the fan-shaped portion constitutes the collimator of the collimation-and-deflection module. The deflection plate of the collimation-and-deflection module is provided on the inner side of the fan-shaped panel of the outer panel. 
     At least one modulation grid of the neutral atom imaging unit is provided above the base portion and close to the fan-shaped portion of the housing, and the at least one semiconductor detector line array is provided below the modulation grid. 
     Optionally, the plurality of application-specific integrated circuits of the preamplifier unit and the at least one master-control-and-interface unit are provided at intervals in the lower part of the housing. 
     Optionally, the neutral atom imager further includes a fixed enclosure. The at least one housing is spaced and at an angle in the fixed enclosure, and the middlemost housing of the at least one housings is vertically arranged in the fixed enclosure. 
     Preferably, the angle between the at least one housings ranges from 3° to 60°. 
     A third aspect of the present disclosure provides a space detection system. The space detection system includes a satellite platform and a neutral atom imager provided by the second aspect of the present disclosure, and the neutral atom imager is installed on the satellite platform. The satellite platform includes a detection microsatellite for space neutral atom imaging. 
     Preferably, the space detection system further includes a miniature GPS navigator, and the miniature GPS navigator is mounted on the satellite platform. 
     A fourth aspect of the present disclosure provides a neutral atom imaging method, including the following: 
     obtaining neutral atoms; 
     performing Fourier transform on the neutral atoms by using a modulation grid; 
     detecting, by a semiconductor detector line array, the neutral atoms transformed by Fourier transform, to generate an imaging signal; 
     the modulation grid includes a slit and a slat forming the slit, the direction of the semiconductor detector line array is consistent with that of the slit of the modulation grid; the modulation grid includes a plurality of grid periods, each of the grid periods includes n slits, the width of the semiconductor detector line array is d, and the width (w i ) of the i-th slit of the modulation grid satisfies the following relationship: 
     
       
         
           
             
               w 
               i 
             
             = 
             
               
                 n 
                 i 
               
               × 
               
                 d 
                 . 
               
             
           
         
       
     
     Optionally, the operation of obtaining neutral atoms includes the following: 
     deflecting the charged particles, and detecting the neutral atoms. 
     Optionally, the method further includes: 
     amplifying the imaging signal; 
     processing, packing, and compressing the amplified imaging signal. 
     Optionally, the operation of amplifying the imaging signal includes the following: 
     providing an operation timing to the at least one preamplifier unit; 
     collecting and reading the imaging signal according to the operation timing; 
     preliminarily fusing and processing the imaging signal. 
     Optionally, the operation of collecting and reading the imaging signal according to the operation timing further includes the following: 
     shaping the imaging signal, and converting the imaging signal into an analog signal; 
     detecting and maintaining the peak value of the imaging signal until the peak value is read out. 
     As described above, the neutral atom imaging unit, the neutral atom imager, the neutral atom imaging method, and the space detection system of the present disclosure have the following technical effects: 
     1. In the present disclosure, the grid imaging technology is applied to the field of neutral atom detection, and the widths of the slit and slat of the modulation grid are designed to be adjustable. Therefore, the widths of the slit and slat of the modulation grid may be adjusted according to actual needs to adapt to the imaging of central atoms of different energies. The imaging efficiency of neutral atoms is greatly improved, the time required for imaging is shortened, and the counting rate of imaging detection of neutral atoms is improved. 
     2. The energy threshold of the silicon semiconductor detector used in the present disclosure for imaging neutral atoms is reduced from the traditional 30 keV to 2 keV, which can cover the energy range of most ring current particles that generate geomagnetic storms. 
     3. The neutral atom imager of the present disclosure may include nearly one thousand semiconductor detectors, with the detection area reaching 200 cm 2  and the geometrical factor reaching 13.3 cm 2 sr. Therefore, the neutral atom imager of the present disclosure has good spatial resolution, time resolution and energy resolution. 
     4. The neutral atom imaging method of the present disclosure would not be affected by the extreme ultraviolet/ultraviolet radiation in space, thus can ensure that neutral atoms with sufficient flux participate in imaging, so as to obtain better imaging effects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the present disclosure will be more clearly understood by referring to the drawings. The drawings are merely schematic representations and shall not be interpreted as limiting the present disclosure. In the drawings: 
         FIG.  1    is a schematic diagram of a semiconductor detector line array and a modulation grid in a set of detection units in a neutral atom imaging unit according to Embodiment 1 of the present disclosure. 
         FIG.  2    is a schematic diagram showing the structure of a modulation grid of a neutral atom imaging unit according to Embodiment 1 of the present disclosure. 
         FIG.  3    is a schematic diagram showing the structure of a semiconductor detector line array of a neutral atom imaging unit according to Embodiment 1 of the present disclosure. 
         FIG.  4    is a schematic diagram showing the imaging principle of a set of semiconductor detector line array and modulation grid of a neutral atom imaging unit according to Embodiment 1 of the present disclosure. 
         FIG.  5    is a schematic diagram showing the principle of a neutral atom imaging unit according to Embodiment 1 of the present disclosure. 
         FIG.  6    is an enlarged schematic diagram showing the circle A part in  FIG.  5   . 
         FIG.  7    is a schematic diagram showing the structure of a neutral atom imager according to Embodiment 2 of the present disclosure. 
         FIG.  8    is a schematic diagram showing the structure of a neutral atom imager according to a preferred embodiment of Embodiment 2 of the present disclosure. 
         FIG.  9    is a schematic diagram showing the structure of a housing of a neutral atom imager according to Embodiment 2 of the present disclosure. 
         FIG.  10    is a schematic diagram showing the structure of a fixed enclosure of a neutral atom imager according to Embodiment 2 of the present disclosure. 
         FIG.  11    is a schematic flowchart of a neutral atom imaging method according to Embodiment 4 of the present disclosure. 
     
    
    
     
       
         
           
               
             
               
                   
               
               
                 Description of reference numerals 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 10 
                 Modulation grid 
               
               
                 101 
                 Slit between grids 
               
               
                 102 
                 Slat forming the slit 
               
               
                 11 
                 Semiconductor detector line array 
               
               
                 110 
                 Carrier plate for semiconductor detector line array 
               
               
                 111 
                 Semiconductor detector strip in the semiconductor detector line 
               
               
                   
                 array 
               
               
                 12 
                 The first incidence direction of neutral atoms 
               
               
                 121 
                 Counting rate of neutral atoms in the first incident direction 
               
               
                 13 
                 The second incidence direction of neutral atoms 
               
               
                 131 
                 Counting rate of neutral atoms in the second incident direction 
               
               
                 20 
                 Imaging probe 
               
               
                 21 
                 Housing 
               
               
                 211 
                 Fan-shaped portion 
               
               
                 212 
                 Base portion 
               
               
                 213 
                 Deflection plate 
               
               
                 214 
                 Collimator 
               
               
                 22 
                 Application-specific integrated circuit 
               
               
                 23 
                 Master-control-and-interface unit 
               
               
                 30 
                 Neutral atom imager 
               
               
                 31 
                 Fixed enclosure 
               
               
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In order to make the objectives, technical solutions and advantages of embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings. The described embodiments are only a part of the embodiments of the present disclosure, instead of all embodiments of the present disclosure. All other embodiments that persons of ordinary skill in the art obtain without creative efforts based on the embodiments of the present disclosure also fall within the scope of the present disclosure. 
     Embodiment 1 
     This embodiment provides a neutral atom imaging unit. In this embodiment, the neutral atom imaging unit includes at least one set of detection units as shown in  FIG.  1   . The detection unit includes a semiconductor detector line array  11  and at least one modulation unit grid  10 . The modulation grid  10  is arranged in front of the semiconductor detector line array  11  and has a distance D from the semiconductor detector line array  11 . The at least one modulation grid  10  and the at least one semiconductor detector line array are arranged in one-to-one correspondence. In the neutral atom imaging unit, the above-mentioned modulation grid  10  performs Fourier transform on the incident neutral atom; 
       FIG.  2    is a schematic structural diagram depicting a modulation grid  10  of the neutral atom imaging unit as shown in  FIG.  1   . In this embodiment, the modulation grid  10  includes a single-layer modulating multi-slit grid. As shown in  FIG.  2   , the modulation grid  10  includes a slit  101  and a slat  102  forming the slit. Each slit  101  has the same width as the slat  102  forming the slit  101 , and one slit  101  and one slat  102  form a pitch. It should be understood that each slit is defined by two adjacent solid grid bars along the arrangement direction of the slits  101  shown in  FIG.  2   . Here, a solid grid bar  102  on the right side of a slit  101  is defined as the solid grid bar forming such slit. 
     Referring to  FIG.  3   ,  FIG.  3    is a schematic structural diagram showing the semiconductor detector line array  11  of the above-mentioned neutral atom imaging unit. As shown in  FIG.  3   , the semiconductor detector line array  11  is arranged on a carrier plate  110 , and the size of the carrier plate of the semiconductor detector line array ranges from 150 mm×45 mm to 180 mm×60 mm. In a more preferred embodiment of this embodiment, the distance D between the semiconductor detector line array and the modulation grid ranges from 10 mm to 15 mm. One semiconductor detector line array  11  includes a plurality of semiconductor detector strips  111 . Each semiconductor detector strip  111  includes a plurality of semiconductor detectors arranged linearly. Referring again to  FIG.  1   , the semiconductor detector strips  111  in the semiconductor detector line array  11  extends in the same direction as the slit  101  of modulation grid  10 . Preferably, the length of the semiconductor detector line array is consistent with that of the modulation grid. 
     In an alternative embodiment, the width of the semiconductor detector strip  111  is defined as d. The widths of the semiconductor detector strip vary with the types of semiconductor detectors. 
     In an alternative embodiment of this embodiment, the semiconductor detector in the semiconductor detector strip  111  includes a thin window with a threshold of about 2 keV, and a semiconductor detector (solid-state detector, SSD) with an extremely low energy threshold. The surface of the sensitive region of the semiconductor detector is coated with a polysilicon layer and an aluminum layer coated on the polysilicon layer. The width d of the semiconductor detector strips formed by the semiconductor detectors is about 0.45 mm. The gap between the semiconductor detector strips is very small, only 0.05 mm. In a more preferred embodiment, the thickness of the polysilicon layer ranges from 100 Å to 200 Å, and the thickness of the aluminum layer ranges from 100 Å to 500 Å. In the most preferred embodiment, the semiconductor detector includes a semiconductor detector with a polysilicon layer having a thickness of 100 Å, an aluminum layer having a thickness of 200 Å and a window having a thickness of 300 Å, and a semiconductor detector with a polysilicon layer having a thickness of 100 Å, an aluminum layer having a thickness of 400 Å and a window having a thickness of 500 Å. In this preferred embodiment, the particles that may be detected by the semiconductor detector include neutral hydrogen atoms (H) and oxygen atoms (O). The energy of the detected H ranges from 2 keV to 200 keV, and the energy of O ranges from 8 keV to 250 keV. 
     Referring again to  FIG.  2   , in this embodiment, one modulation grid  10  includes a plurality of grid periods, and each grid period includes a plurality of slits. The widths of the slits vary regularly over a grid period. The modulation grid  10  includes m grid periods. It is defined that a grid period contains n slits, the widest slit is the first slit, and the width of the i-th slit is wi. The width (w i ) of the i-th slit and the width (d) of the semiconductor detector line array satisfy the following relationship: 
               w   i     =       n   i     ×     d   .             
In a preferred embodiment, the width of the narrowest slit (i.e., the n-th slit) in a grid period is defined to be the same as the width d of the semiconductor detector strip, that is, w i =d. In an embodiment, m≥2 and n≥8. According to the above formula of slit width, the widths of each slit and the slat forming the slit in a grid period can be determined, and the required modulation grid may thus be formed according to the number of grid periods in the modulation grid. Based on the principle of neutral atom imaging, the thickness of the modulation grid should be as small as possible, and the ideal thickness is 0. In this embodiment, in order to obtain as thin a modulation grid as possible, the thickness of the modulation grid is defined as t, which satisfies: t≤¼d. In a more preferred embodiment, the thickness of the modulation grid is close to 0.1 mm.
 
     As described above, after determining the width d of the semiconductor detector strip (that is, the width of the narrowest slit in the modulation grid), and the distance D between the modulation grid and the semiconductor detector line array, the angular resolution of the neutral atom imaging unit can be determined as follows: 
     
       
         
           
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                 arctan 
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                     d 
                     
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     Still referring to  FIG.  2   , in a preferred embodiment, the outer length L 1  of the modulation grid  10  ranges from 120 mm to 130 mm, the inner length L 2  of the modulation grid  10  ranges from 110 mm to 120 mm. The outer width H 1  of the modulation grid  10  ranges from 30 mm to 50 mm, and the inner width H 2  of the modulation grid  10  ranges from 20 mm to 30 mm. That is, the size of the multi-slit grid ranges from 120 mm×30 mm to 130 mm×50 mm. The thickness of the multi-slit grid may be 0.1 mm or 0.2 mm. 
     In another alternative embodiment of this embodiment, as shown in  FIG.  4   , the principle of the detection unit of the neutral atom imaging unit shown in  FIG.  1    is illustrated. As shown in  FIG.  4   , neutral atoms from the same incident direction (i.e., having the same velocity), such as those from the first incident direction  12  or the second incident direction  13 , pass through the modulating multi-slit grid with varying to slit widths. The modulating multi-slit grid performs Fourier transform on the incident neutral atom, such that the counting rate of neutral atoms received by the detector line array would vary with the position of the detector. As shown in  FIG.  4   , the counting rate  121  of the detector line array for neutral atoms in the first incident direction  12  and the counting rate  131  of the detector line array for neutral atoms in the second incident direction  13  vary with the position of the detector. For different incident directions, such as the first incident direction  12  and the second incident direction  13 , the Fourier transform of the modulating multi-slit grid is different. Using the above-mentioned characteristics of the neutral atom imaging unit and performing Fourier inversion on the neutral atoms sensed by the semiconductor detector line array, the spatial distribution of the neutral atoms in different directions can be obtained, thereby obtaining the position and size of the active region. 
     In another preferred embodiment, the neutral atom imaging unit further includes a collimation-and-deflection module, and the collimation-and-deflection module includes a collimator and a deflection plate. The collimation-and-deflection module includes a collimator and a deflection plate. By applying a deflection voltage to the deflection plate, the charged particles, such as various electrons and ions, are deflected away, such that the grid imaging unit only detects the neutral atoms and images the neutral atoms. 
       FIG.  5    is a schematic diagram showing the principle of the neutral atom imaging unit. In  FIG.  5   , the imaging opening angle in the neutral atom imaging unit is 45°. In  FIG.  5   , for ease of illustration, the modulation grid  10  and semiconductor detector line array  11  of the neutral atom imaging unit are shown in the XY directions. However, during the actual imaging process, the modulation grid and semiconductor detector line array of the neutral atom imaging unit are placed along the YZ plane shown in  FIG.  5   , with an imaging opening angle of 45°. The neutral atoms are detected and imaged by the neutral atom imaging unit within a 45° field of view on the XZ plane. That is, the view of the circle A in  FIG.  5    is actually a view rotated by 90° along the normal direction of the YZ plane. The field angle of the neutral atom imaging unit in the XY plane is 10°. In this preferred embodiment, the length of the deflection plate  213  is set to 190 mm, the distance between the two deflection plates is set to 30 mm, and the distance between the deflection plate  213  and the modulation grid  10  is set to 30 mm. A voltage of 6 kV is applied to the deflection plate  213 . The particles (including neutral atoms and various charged particles) passing through the collimator  214  enter the deflection plate  213  with the above voltage. The deflection plate  213  deflects the various charged particles. In this embodiment, the above-mentioned deflection plate can deflect most of the charged particles of 30 keV, such that only neutral atoms could enter the neutral atom imaging unit. The modulation grid of the neutral atom imaging unit performs Fourier transform on the neutral atoms, and the semiconductor detector detects and images the neutral atoms. 
     Further referring to  FIG.  6   ,  FIG.  6    shows an enlarged schematic diagram of the circle A part in  FIG.  5   . In the above-mentioned preferred embodiment of this embodiment, two adjacent sets of detection units in the neutral atom imaging unit are shown. Each set of detection units includes a modulation grid  10  and a semiconductor detector line array  11 . In each set of detection units, the direction of the semiconductor detector line array is consistent with that of the slits of the modulation grid. In the two adjacent sets of detection units, the directions of the slits of the modulation grids (or the detector line arrays) differ by 18°. Therefore, for a neutral atom imaging unit including at least one set of detection units, the Fourier transform may be performed on the incident neutral atom in different directions For example, in a more preferred embodiment, the neutral atom imaging unit may include 10 sets of the aforementioned detection units, such that the neutral atom imaging unit includes 10 sets of semiconductor line arrays and modulation grids. In a more preferred embodiment, each semiconductor detector line array may include 256 semiconductor detectors. Therefore, the neutral atom imaging unit may include 10×256=2560 semiconductor detectors. The semiconductor detector line array may obtain modulation signals generated by the modulation grids in 10 different directions at the same time. The field of view of the neutral atom imaging unit is a two-dimensional cone with an opening angle of 45°, and the angular resolution may reach about 2°. Therefore, the neutral atom imager can provide a neutral atom imaging unit with high sensitivity, large field of view, and high angular resolution. 
     Embodiment 2 
     As shown in  FIG.  7   , this embodiment provides a neutral atom imager, which includes at least one neutral atom imaging unit, at least one preamplifier unit, and at least one master-control-and-interface unit; the at least one neutral atom imaging unit, the at least one preamplifier unit, and the at least one master-control-and-interface unit are electrically connected to each other. 
     The at least one neutral atom imaging unit detects and images neutral atoms. The at least one preamplifier unit reads the imaging data of the at least one neutral atom imaging unit, and preliminarily amplifies the imaging data. 
     The preamplifier unit includes a plurality of application-specific integrated circuits. The application-specific integrated circuits read the imaging signal of the at least one neutral atom imaging unit in real time and amplify the imaging signal. 
     Still referring to  FIG.  7   , in a preferred embodiment, the preamplifier unit includes at least one charge-sensitive preamplifier, at least one multi-stage shaper, and at least one peak detector. The peak detector detects the peak value of the imaging signal and maintains the peak value until the peak value is read out. 
     In another preferred embodiment, the master-control-and-interface unit provides an operation timing to at least one application-specific integrated circuit, controls at least one application-specific integrated circuit to collect and read out the imaging signal, and performs preliminarily fuse and process the imaging signal. 
     In another preferred embodiment, as shown in  FIG.  8   , the neutral atom imager further includes a data processing unit. The data processing unit receives the imaging signal transmitted by the preamplifier in the neutral atom imager, and processes, packs, and compresses the imaging signal for storage. 
     In a preferred embodiment, at least one neutral atomic imaging unit communicatively connects with the data processing unit by using the master-control-and-interface unit of the at least one neutral atomic imaging unit as an interface. 
     Embodiment 3 
     This embodiment also provides a neutral atom imager. As shown in  FIG.  9   , the imaging probe  20  of the neutral atom imager further includes at least one housing  21 . The housing  21  includes a base portion  212  and a fan-shaped portion  211  located above and fixedly connected to the base portion  212 . In a more preferred embodiment, the fan-shaped portion  211  and the base portion  212  may be integrally formed, or may be fixedly connected by screw fastening, riveting, welding or the like. As shown in  FIG.  9   , the collimation-and-deflection module of the neutral atom imaging unit is provided on the fan-shaped portion  211 . The outer panel of the fan-shaped portion  211  constitutes the collimator  214  of the collimation-and-deflection module. The deflection plate  213  is provided on the inner side of the fan-shaped panel of the outer panel. At least one detection unit of the neutral atom imaging unit is provided above the base portion  212  of the housing  21 . The modulation grid  10  of the detection unit is close to the fan-shaped portion  211 . The semiconductor detector line array is provided below the modulation grid  10 . For example, in a more preferred embodiment, the distance between the modulation grid  10  and the semiconductor detector line array ranges from 10 mm to 15 mm. 
     Still referring to  FIG.  9   , a plurality of application-specific integrated circuits  22  and a master-control-and-interface unit  23  are provided inside the base portion  212  of the housing  21 . The plurality of application-specific integrated circuits  22  and the master-control-and-interface unit  23  may be multiple layers spaced and alternatively arranged, or may be integrated in the same layer. 
     As shown in  FIG.  10   , in another preferred embodiment, the neutral atom imager  30  further includes a fixed enclosure  31 . At least one imaging probe  20  is provided in the fixed enclosure  31  in the form of an integral member formed by the housing  21 . Preferably, the imaging probes  20  are spaced and at an angle in the fixed enclosure  31 . In a more preferred embodiment, the neutral atom imager  20  in the middle is vertically arranged in the fixed enclosure  31 . 
     In the preferred embodiment shown in  FIG.  10   , the neutral atom imager  30  includes three imaging probes  20 . The imaging probe in the middle is vertically arranged in the fixed enclosure  31 , and the imaging probes  20  on both sides are arranged at intervals in the fixed enclosure  31  and are at an angle to the imaging probe in the middle, respectively. The angle may range from 3° to 60°, for example, in this embodiment, the angle is 10°. 
     In the preferred embodiment shown in  FIG.  10   , the neutral atom imager  30  includes three imaging probes  20 , and each imaging probe includes a neutral atom imaging unit. As described in the more preferred embodiment of the Embodiment 1, each neutral atom imaging unit may include 10 sets of detection units, and each detection unit includes a 256 semiconductor detector line array and a modulation grid arranged in front of the 256 semiconductor detector line array. Therefore, the above-mentioned 10 sets of detection units may obtain modulation signals generated by the modulation grid in 10 different directions of the source area particles at the same time. The field of view of each neutral atom imaging unit is 10°×45°. The neutral atom imager of this embodiment includes 10×256=2560 semiconductor detectors. In the 256 line array SSD, the area of each semiconductor detector unit is about 0.08 cm 2 . Therefore, the area of 2560 SSDs of the neutral atom imager of this preferred embodiment is about 204.8 cm 2 . Therefore, the field of view of the neutral atom imaging system is a two-dimensional cone with an opening angle of 45°, and the angular resolution may reach about 2°. Therefore, the neutral atom imager, including nearly a thousand semiconductor detectors, is capable of measuring neutral atoms from all directions with high spatial resolution, such as 2°×2°. The energy of detected H ranges from 2 keV to 200 keV, and the energy of O ranges from 8 keV to 250 keV, with high energy resolution such as ΔE/E−1 keV. Further, the neutral atom imager has a high time resolution, such as 1 to 10 seconds. 
     Embodiment 4 
     This embodiment provides a neutral atom imaging method, which performs imaging by the neutral atom imaging system described in Embodiment 3. As shown in  FIG.  11   , the neutral atom imaging method includes the following operations: 
     obtaining neutral atoms; 
     performing Fourier transform on the neutral atoms; 
     detecting the neutral atoms transformed by Fourier transform, to generate an imaging signal. 
     In a preferred embodiment of this embodiment, the operation of obtaining neutral atoms further includes the following: 
     deflecting the charged particles, such that only neutral atoms are detected. 
     In a preferred embodiment of this embodiment, the neutral atom imaging method further includes the following operations: 
     amplifying the imaging signals; 
     processing, packing, and compressing the amplified imaging signal. 
     In another preferred embodiment of this embodiment, the operation of amplifying the imaging signals further includes the following: 
     providing an operation timing to the at least one preamplifier unit; 
     collecting and reading the imaging signal according to the operation timing; 
     preliminarily fusing and processing the imaging signal. 
     In another preferred embodiment of this embodiment, the operation of collecting and reading the imaging signals according to the operation timing further includes the following: 
     shaping the imaging signal to convert the imaging signal into an analog signal; 
     detecting and maintaining the peak value of the imaging signal until the peak value is read out. 
     In summary, the neutral atom imaging unit, the neutral atom imager, the neutral atom imaging method, and the space detection system provided by the foregoing embodiments of the present disclosure have the following technical effects: 
     1. In the present disclosure, the grid imaging technology is applied to the field of neutral atom detection, and the widths of the slit and slat of the modulation grid are adjusted to be adjustable. Therefore, the widths of the slit and slat of the modulation grid may be designed according to actual needs to adapt to the imaging of central atoms of different energies. The imaging efficiency of neutral atoms is greatly improved, the time required for imaging is shortened, and the counting rate of imaging detection of neutral atoms is improved. 
     2. The energy threshold of the silicon semiconductor detector used in the present disclosure for imaging neutral atoms is reduced from the traditional 30 keV to 2 keV, which can cover the energy range of most ring current particles that generate geomagnetic storms. 
     3. The neutral atom imager of the present disclosure may include nearly one thousand semiconductor detectors, with the detection area reaching 200 cm 2  and the geometrical factor reaching 13.3 cm 2 sr. Therefore, the neutral atom imager of the present disclosure has good spatial resolution, time resolution and energy resolution. 
     4. The neutral atom imaging method of the present disclosure would not be affected by the extreme ultraviolet/ultraviolet radiation in space, thus can ensure that neutral atoms with sufficient flux may participate in imaging, so as to obtain better imaging effects. 
     The above-mentioned embodiments are just used for exemplarily describing the principle and effects of the present disclosure instead of limiting the present disclosure. Various changes and variations may be made by the skilled in the art without departing the spirit and scope of the present disclosure. The above changes and variations fall within the scope as specified by the appended claims.