Preparation method of coded photocathode X-ray streak camera, compressed ultrafast imaging device and method

Abstract

The present invention relates to a method for preparing a coded photocathode X-ray streak camera, a compressed ultrafast imaging device and a method, in order to solve the technical problems of the current spatial coding method of the photocathode of the X-ray streak camera, poor stability of the external hardware setting under vacuum connection conditions, and difficulty in calibration. The preparation method comprises: 1. preparing an optical mask; 2. depositing a chromium layer on the cathode window; 3. engraving a random binary pattern; 4. depositing a palladium layer to obtain a coded photocathode; 5. sealing the coded photocathode with the tube body of the stripe image converter. The device comprises an X-ray source for emitting X-rays, and an X-ray streak camera, a charge coupled device and a computing processor are sequentially arranged along the signal transmission direction. The method comprises: the X-ray source emits an X-ray light pulse which is converted into a coded electrical signal through the coded photocathode, and then forms a coded light signal through the stripe image converter, which is converted by the charge coupled device and transmitted to the processor to obtain a time series image.

Description

Technical Field

[0001] The present invention relates to an imaging device and an imaging method of an X-ray streak camera, and in particular to a preparation method of a coded photocathode X-ray streak camera, and a compressed ultrafast imaging device and method. Background Art

[0002] The evolution of X-ray radiation generated by ICF implosion carries key information about the implosion. The diagnostic method of X-ray with high spatial and temporal resolution can be used to study the temporal and spatial behavior of the target during the entire implosion process, especially the energy transfer and transformation processes in different regions with large changes in density and temperature, such as the coronal region, ablation region and central implosion region outside the target. During the compression of the target pellet, parameters such as the motion law of the critical surface, interface instability, and uniformity of the radiation field are measured. Based on the measurement of this series of related parameters, problems such as the mixing degree of the ablation layer and the fuel, the implosion speed, and the compression shape of the hot spot that affect the success or failure of ignition can be effectively solved.

[0003] The ultra-high-speed spatiotemporal evolution characteristics of X-rays produced by laser plasma and laser fusion are the main difficulties in ICF physical experimental research. Picosecond or even femtosecond time-resolved diagnosis is the time resolution scale required in this field. X-ray diagnostic equipment with high time resolution mainly includes X-ray traveling wave gated framing cameras and X-ray streak cameras.

[0004] The X-ray traveling wave gated framing camera is the only two-dimensional ultrafast imaging device in ICF research, but it is limited by technical bottlenecks such as electron transition dispersion, microchannel plate aperture, and the close distance between the microchannel plate and the fluorescent screen, making it difficult to break through the time resolution limit of 60ps. However, during the implosion compression process, the observation time of the spontaneous luminescence of the implosion core and the non-uniformity of the hot spot is only 200ps, which requires that the time resolution of the imaging diagnostic equipment for the implosion target be within 10ps in order to achieve precise and effective diagnosis of the ICF implosion process. In addition, the number of discontinuous imaging frames of the framing camera is only 16 frames at most. At the same time, due to the fast transmission speed of the electric pulse on the microstrip line, the imaging time span of the framing camera is very small, so the framing camera technology cannot effectively reflect the evolution process of X-rays.

[0005] X-ray streak cameras (X-CUP) can meet the temporal resolution requirements of imaging diagnostic equipment for imploding target pellets. However, traditional visible light imaging CUP technology relies on spatial light modulators (DMD or optical masks) to achieve spatial encoding of dynamic scenes, while X-ray streak cameras need to maintain a vacuum connection with the target chamber when working in the target range. This can easily lead to poor stability in spatial encoding achieved by the X-CUP system through external hardware, and inconvenient system calibration. Summary of the invention

[0006] The purpose of the present invention is to solve the technical problems of the current spatial encoding method of the photocathode of an X-ray streak camera, poor stability of the external hardware setting under vacuum connection conditions, and difficulty in calibration, and to propose a preparation method for a coded photocathode X-ray streak camera, a compressed ultrafast imaging device and method.

[0007] The technical solution of the present invention is:

[0008] A method for preparing a coded photocathode X-ray streak camera, which is special in that it comprises the following steps:

[0009] S1. Using chromium to prepare an optical mask on the surface of a transparent solid material by optical coating; the optical mask comprises a plurality of chromium film regions and a plurality of light-transmitting regions;

[0010] S2, placing the cathode window in a cathode manufacturing chamber in a vacuum chamber of a transfer system, and depositing a chromium layer on the cathode window by electron beam evaporation, wherein the thickness of the chromium layer is 180-220 nm;

[0011] S3, using a photolithography machine to emit ultraviolet light through the light-transmitting area of ​​the optical mask of step S1, irradiating the chromium layer of step S2, and engraving the chromium layer into a random binary pattern;

[0012] S4, depositing a palladium layer on the surface of the random binary pattern by electron beam evaporation, wherein the palladium layer has a thickness of 10-20 nm, to obtain a coded photocathode;

[0013] S5. Transfer the coded photocathode from the cathode manufacturing chamber to the indium sealing chamber in a vacuum through a magnetic transfer device, and seal the coded photocathode and the stripe image converter tube body through thermal indium sealing to complete the transfer and manufacturing of the stripe image converter tube photocathode, and obtain an X-ray streak camera with a coded photocathode.

[0014] Further, in step S1, the optical mask includes multiple chrome film areas and multiple light-transmitting areas. Specifically, the spatial distribution of the chrome film areas and the light-transmitting areas is determined according to a random matrix generated by a computer; the random matrix includes two elements "0" and "1", wherein "0" indicates that the optical mask is plated with a chrome film at the spatial position corresponding to "0" to form a chrome film area, and "1" indicates that the optical mask is not plated with a chrome film at the spatial position corresponding to "1" to form a light-transmitting area.

[0015] Furthermore, in step S3, the etching accuracy of the photolithography machine is less than 10 um.

[0016] Furthermore, in step S1, the transparent solid material is quartz glass.

[0017] Furthermore, in step S2, the cathode window is a silicon substrate.

[0018] The present invention also provides a compressed ultrafast imaging device of a coded photocathode X-ray streak camera, which is special in that: an X-ray streak camera prepared by the above-mentioned method for preparing a coded photocathode X-ray streak camera;

[0019] It includes an X-ray source for emitting X-rays, and an X-ray streak camera, a charge coupled device and a computing processor are sequentially arranged along the signal transmission direction;

[0020] The X-ray streak camera and the X-ray source are both connected to a digital delay device, and the digital delay device is used to synchronize the scanning time of the X-ray streak camera with the X-ray emission time in the X-ray source;

[0021] The X-ray streak camera comprises a coding photocathode and a streak image converter arranged in sequence along the signal transmission direction; the streak image converter is connected to a digital delay device;

[0022] The computing processor comprises a compressed sensing reconstruction algorithm module, and the compressed sensing reconstruction algorithm module is used to reconstruct the collected signals into a two-dimensional sequence.

[0023] Furthermore, the fringe image converter is provided with a fluorescent screen and two parallel and opposite deflection plates;

[0024] The two deflection plates are arranged at the rear side of the coding photocathode, and are used to deflect the coded electrical signal generated after passing through the coding photocathode;

[0025] The fluorescent screen is connected to the digital delay device, and is used to receive the coded electrical signal deflected by the deflection plate and convert it into a coded optical signal.

[0026] Furthermore, the voltage applied to the two deflection plates is a ramp deflection voltage of 1000-2000V, and the deflection frequency is 1 Hz.

[0027] At the same time, the present invention also provides a compressed ultrafast imaging method of a coded light cathode X-ray streak camera, which is special in that the compressed ultrafast imaging device based on the above-mentioned coded light cathode X-ray streak camera includes the following steps:

[0028] A1. The X-ray source generates a triggering electrical signal, which triggers the X-ray streak camera to work through a digital delay device;

[0029] The X-ray source emits X-ray light pulses, wherein the X-ray light pulses have intensity information of the X-rays at different times and spaces;

[0030] A2. X-ray light pulses are imaged on the coded photocathode, and the spatial encoding of information is realized through the coded photocathode, which is converted into coded electrical signals. The coded electrical signals are imaged on the fluorescent screen through the fringe image converter to form coded optical signals.

[0031] A3. The coded light signal is converted into an electrical signal through a charge coupled device, and the electrical signal is output to a computing processor. The computing processor reconstructs the collected electrical signal into a two-dimensional sequence through a compressed sensing reconstruction algorithm module to obtain a time series image carrying information on the distribution of different spatiotemporal intensities of the X-ray light pulse.

[0032] Furthermore, in step A2, the coded electrical signal is imaged by a stripe image converter to form a coded optical signal, specifically:

[0033] A2.1. Apply a 1000-2000V ramp deflection voltage to the deflection plate;

[0034] A2.2. The coded electrical signal is scanned by the deflection voltage and superimposed on the fluorescent screen.

[0035] Beneficial effects of the present invention:

[0036] 1. The present invention can realize the integration of streak camera encoding and scanning imaging by encoding the photocathode of the X-ray streak camera, without building an external hardware encoding device, and realize the direct connection between the X-CUP system and the ICF target room.

[0037] 2. The coded photocathode makes the X-ray streak camera system more stable, avoiding the significant errors in the experiment caused by the jitter of the external coding hardware and enhancing the adaptability of the X-CUP system to the target room environment.

[0038] 3. The compressed ultrafast imaging method of the coded photocathode X-ray streak camera of the present invention reconstructs the coded signal formed by the X-ray streak camera with a coded photocathode into a two-dimensional sequence through a compressed sensing reconstruction algorithm to obtain a high-temporal-resolution time series image of the different spatiotemporal intensity distribution information of the X-ray pulse. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the cross-sectional structure of the coded photocathode in the present invention;

[0040] Figure 2 It is a schematic diagram of the principle structure of an embodiment of a compressed ultrafast imaging device of a coded photocathode X-ray streak camera of the present invention.

[0041] The reference numerals are as follows:

[0042] 1- cathode window, 2- chromium layer, 3- palladium layer, 4- X-ray source, 5- coded photocathode, 6- deflection plate, 7- phosphor screen, 8- charge coupled device, 9- computing processor, 10- digital delay device, 11- coded electrical signal, 12- coded optical signal. DETAILED DESCRIPTION

[0043] An embodiment of the present invention provides a method for preparing a coded photocathode X-ray streak camera, the method comprising the following steps:

[0044] S1. An optical mask is prepared on the surface of a transparent solid material by optical coating with chromium, wherein the transparent solid material is preferably quartz glass; the optical mask comprises a plurality of chrome film areas and a plurality of light-transmitting areas; specifically, the spatial distribution of the chrome film areas and the light-transmitting areas is determined according to a random matrix generated by a computer; the random matrix comprises two elements, "0" and "1", wherein "0" indicates that the optical mask is plated with chrome film at the spatial position corresponding to "0" to form a chrome film area, and "1" indicates that the optical mask is not plated with chrome film at the spatial position corresponding to "1" to form a light-transmitting area.

[0045] S2. Placing the cathode window 1 in the cathode manufacturing chamber in the vacuum chamber of the transfer system, and depositing a chromium layer 2 on the cathode window 1 by electron beam evaporation, wherein the deposition thickness of the chromium layer 2 is 180-220 nm; wherein the cathode window 1 adopts a silicon substrate.

[0046] S3, using a photolithography machine to emit ultraviolet light through the light-transmitting area of ​​the optical mask of step S1, irradiating the chromium layer 2 of step S2, and engraving the chromium layer 2 into a random binary pattern; the etching accuracy of the photolithography machine is less than 10um.

[0047] S4, depositing a palladium layer 3 on the surface of the random binary pattern by electron beam evaporation, the deposition thickness of the palladium layer 3 is 10-20nm, and obtaining a coded photocathode 5; see Figure 1 The coded photocathode 5 includes two types of regions, the first type of region includes a chromium layer 2 and a palladium layer 3 covering the chromium layer 2, and the second type of region only includes the palladium layer 3; wherein the chromium layer 2 is used to isolate electrons, and the palladium layer 3 is used for photoelectric conversion; therefore, when the light signal is transmitted to the first type of region of the coded photocathode 5, the light signal is isolated by the chromium layer 2 after the photoelectric conversion of the palladium layer 3, and signal transmission cannot be achieved; when the light signal is transmitted to the second type of region of the coded photocathode 5, the light signal is photoelectrically converted by the palladium layer 3, and there is no isolation of the chromium layer 2, so the transmission of the electrical signal is achieved; therefore, the light signal forms a coded electrical signal 11 after passing through the coded photocathode 5.

[0048] S5. Transfer the coded photocathode 5 from the cathode manufacturing chamber to the indium sealing chamber in a vacuum through a magnetic transfer device, and seal the coded photocathode 5 with the stripe image converter tube body through thermal indium sealing, thereby completing the transfer manufacturing of the stripe image converter tube photocathode and obtaining an X-ray streak camera with the coded photocathode 5.

[0049] See also Figure 2A compressed ultrafast imaging device comprising a coded photocathode X-ray streak camera prepared by the above preparation method, the device comprises an X-ray source 4 for emitting X-rays, and a coded photocathode 5, a deflection plate 6, a fluorescent screen 7, a charge coupled device 8 (CCD) and a computing processor 9 are arranged in sequence along the signal transmission direction; wherein the coded photocathode 5 is a binary randomly distributed code.

[0050] The X-ray streak camera and the X-ray source 4 are both connected to a digital delay 10 , and the digital delay 10 is used to synchronize the scanning time of the X-ray streak camera with the X-ray emission from the X-ray source 4 .

[0051] The X-ray streak camera comprises a coding photocathode 5 and a streak image converter which are sequentially arranged along the signal transmission direction, and two parallel and opposite deflection plates and a fluorescent screen are arranged in the streak image converter; the voltage applied to the two deflection plates is a 1000-2000V ramp voltage, and the deflection frequency is 1Hz; the deflection plate is arranged on the rear side of the coding photocathode 5, and is used to deflect the electrical signal generated after passing through the coding photocathode 5; the fluorescent screen is connected to the digital delay device 10, and is used to receive the encoded electrical signal and convert it into an optical signal.

[0052] The computing processor 9 includes a compressed sensing reconstruction algorithm module, which is used to reconstruct the collected information into a two-dimensional sequence.

[0053] The compressed ultrafast imaging process of the above-mentioned coded photocathode X-ray streak camera includes the following steps:

[0054] A1. The X-ray source 4 generates a triggering electrical signal, which triggers the X-ray streak camera to work through the digital delay device 10; the X-ray source 4 emits X-ray light pulses, which have the intensity information of the X-rays at different times.

[0055] A2. X-ray light pulses realize spatial encoding of information through the coded photocathode 5 and are converted into coded electrical signals 11. The coded electrical signals 11 are imaged on the fluorescent screen through the stripe image converter to form coded optical signals 12. The coded electrical signals 11 are converted into coded optical signals 12 specifically as follows: a 1500V ramp deflection voltage is applied to the deflection plate; the coded electrical signals 11 are scanned by the deflection voltage and superimposed and imaged on the fluorescent screen.

[0056] A3, the coded light signal 12 is converted into an electrical signal through a charge coupled device 8 (CCD), and the electrical signal is output to a computing processor 9, which performs a two-dimensional sequence reconstruction on the collected electrical signal through a compressed sensing reconstruction algorithm module to obtain a sequence image carrying information on the distribution of different spatiotemporal intensities of the X-ray light pulse.

Claims

1. A method for preparing a coded photocathode X-ray streak camera, It is characterized in that The following steps are involved: S1. Using chromium to prepare an optical mask on the surface of a transparent solid material by optical coating; the optical mask comprises a plurality of chromium film regions and a plurality of light-transmitting regions; S2, placing the cathode window (1) in a cathode production chamber in a vacuum chamber of a transfer system, and depositing a chromium layer (2) on the cathode window (1) by electron beam evaporation, wherein the thickness of the chromium layer (2) is 180-220 nm; S3, using a photolithography machine to emit ultraviolet light through the light-transmitting area of ​​the optical mask of step S1, irradiating the chromium layer (2) of step S2, and engraving the chromium layer (2) into a random binary pattern; S4, depositing a palladium layer (3) on the surface of the random binary pattern by electron beam evaporation, wherein the thickness of the palladium layer (3) is 10-20 nm, to obtain a coded photocathode (5); S5. The coded photocathode (5) is transferred from the cathode manufacturing chamber to the indium sealing chamber in a vacuum by means of a magnetic force transfer device, and the coded photocathode (5) and the tube body of the stripe image converter are sealed by means of thermal indium sealing, thereby completing the transfer manufacturing of the photocathode of the stripe image converter tube and obtaining an X-ray streak camera having the coded photocathode (5).

2. The method for preparing a coded photocathode X-ray streak camera according to claim 1, Features: In step S1, the optical mask includes a plurality of chrome film areas and a plurality of light-transmitting areas. Specifically, the spatial distribution of the chrome film areas and the light-transmitting areas is determined according to a random matrix generated by a computer; the random matrix includes two elements, "0" and "1", wherein "0" indicates that the optical mask is plated with a chrome film at the spatial position corresponding to "0" to form a chrome film area, and "1" indicates that the optical mask is not plated with a chrome film at the spatial position corresponding to "1" to form a light-transmitting area.

3. A method for preparing a coded photocathode X-ray streak camera according to claim 1 or 2, Features: In step S3, the etching accuracy of the photolithography machine is less than 10um.

4. The method for preparing a coded photocathode X-ray streak camera according to claim 3, Features: In step S1, the transparent solid material is quartz glass.

5. The method for preparing a coded photocathode X-ray streak camera according to claim 4, Features: In step S2, the cathode window (1) is a silicon substrate.

6. A compressed ultrafast imaging device for a coded photocathode X-ray streak camera, Features: An X-ray streak camera manufactured by the method for manufacturing a coded photocathode X-ray streak camera according to any one of claims 1 to 5; It comprises an X-ray source (4) for emitting X-rays, and an X-ray streak camera, a charge coupled device (8) and a computing processor (9) are sequentially arranged along a signal transmission direction; The X-ray streak camera and the X-ray source (4) are both connected to a digital delay device (10), and the digital delay device (10) is used to synchronize the scanning time of the X-ray streak camera with the X-ray emission time in the X-ray source (4); The X-ray streak camera comprises a coding photocathode (5) and a streak image converter tube which are arranged in sequence along the signal transmission direction; the streak image converter tube is connected to a digital delay device (10); The computing processor (9) comprises a compressed sensing reconstruction algorithm module, and the compressed sensing reconstruction algorithm module is used to reconstruct the collected signals into a two-dimensional sequence.

7. The compressed ultrafast imaging device of the coded photocathode X-ray streak camera according to claim 6, Features: The stripe image converter tube is provided with a fluorescent screen (7) and two parallel and opposite deflection plates (6); The two deflection plates (6) are arranged on the rear side of the coding photocathode (5) and are used to deflect the coded electrical signal generated after passing through the coding photocathode (5); The fluorescent screen (7) is connected to the digital delay device (10), and the fluorescent screen (7) is used to receive the coded electrical signal deflected by the deflection plate (6) and convert it into a coded optical signal.

8. The compressed ultrafast imaging device of the coded photocathode X-ray streak camera according to claim 7, Features: The voltage applied to the two deflection plates (6) is a slope deflection voltage of 1000-2000V, and the deflection frequency is 1 Hz.

9. A compressed ultrafast imaging method for a coded photocathode X-ray streak camera. It is characterized in that The compressed ultrafast imaging device of the coded photocathode X-ray streak camera according to any one of claims 7 to 8 comprises the following steps: A1, the X-ray source (4) generates a triggering electrical signal, which triggers the X-ray streak camera to work through the digital delay device (10); the X-ray source (4) emits X-ray light pulses, and the X-ray light pulses have intensity information of the X-rays at different times and spaces; A2, X-ray light pulses are imaged on the coding photocathode (5), and spatial encoding of information is realized through the coding photocathode (5), and converted into a coded electrical signal (11), and the coded electrical signal (11) is imaged by a stripe image converter to form a coded optical signal (12); A3. The coded optical signal (12) is converted into an electrical signal by a charge coupled device (8), and the electrical signal is output to a computing processor (9). The computing processor (9) performs a two-dimensional sequence reconstruction on the collected electrical signal through a compressed sensing reconstruction algorithm module to obtain a time series image carrying information on the distribution of different spatiotemporal intensities of the X-ray light pulse.

10. The compressed ultrafast imaging method of the coded photocathode X-ray streak camera according to claim 9, Features: In step A2, the coded electrical signal (11) is imaged by a stripe image converter to form a coded optical signal (12) as follows: A2.

1. Apply a 1000-2000V ramp deflection voltage to the deflection plate (6); A2.

2. The coded electrical signal (11) is scanned by the deflection voltage and superimposed on the fluorescent screen (7) to form an image.

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