System and method for obtaining radiation impulse response

Abstract

The invention particularly relates to a system and a method for obtaining radiation pulse response, and solves the technical problems that the accuracy is low when the radiation pulse response is calculated, the experiment time for actually measuring the radiation pulse response of a streak camera system is long, and parameters are difficult to accurately obtain in the prior art. Compared with the prior art, the system for obtaining the radiation pulse response has the advantages that the relative uncertainty of the obtained radiation pulse response is less than 100%, the experiment time of actually measuring the radiation pulse response of the streak camera system is greatly reduced, and the experiment time can be reduced by about 50% at most. The method provided by the invention can be used for estimating the radiation pulse response of the streak camera system, and the test result can be compared with the response obtained on the pulse radiation source for mutual reference, so that the reliability of the test result is improved.

Description

Technical Field

[0001] This invention specifically relates to a system and method for obtaining a radiation pulse response. Background Technology

[0002] A streak camera system comprises a scintillator, a mirror, an objective lens, and a streak camera arranged along the optical path. It is an ultrafast photoelectric recording device. The streak camera consists of a slit, a relay lens, a streak tube, an image intensifier, and a digital camera. During operation, the photocathode of the streak tube receives light incident from the slit through the relay lens and converts it into photoelectrons. These photoelectrons are accelerated within the streak tube by its electro-optical system and form an image on a fluorescent screen at the rear of the tube. As the photoelectrons travel from the photocathode to the fluorescent screen, they pass through deflection plates within the streak tube. A time-varying voltage is applied to these plates, causing photoelectrons passing through them at different times to be deflected to different positions on the fluorescent screen, thus converting temporal information into spatial information. Finally, the photoelectrons are converted into a visible light image by the fluorescent screen, enhanced by the image intensifier, and then recorded by the digital camera. When the streak camera system is working, a scintillator is placed on the object surface of the objective lens. Through the reflection of the mirror, the light collection of the objective lens, and the imaging of the streak camera, the change of the radiation power of the light emitted by the scintillator over time is recorded. This allows for tasks such as monitoring X-ray pulse intensity and studying the properties of scintillator materials.

[0003] The radiative pulse response of a streak camera system is the net gray value (unit: ADUs, Analog-to-Digital Units) of a pixel in the output light pulse image of the streak camera, divided by the radiative pulse power density (unit: W / cm²) of the incident scintillator. 2 The ratio of the values ​​taken at the corresponding moment of the pixel, where the radiation pulse power density is uniformly distributed on the incident surface of the scintillator. The radiation pulse response of the streak camera system is determined by several parameters, including the scintillator's energy deposition efficiency for radiation pulses, the scintillator's luminous efficiency, the objective lens efficiency, the streak camera's response to the scintillator's luminous emission, and the digital camera's sensitivity. However, it is difficult to obtain accurate results for these parameters through independent measurement or theoretical calculation.

[0004] Obtaining the radiation pulse response of the streak camera system before conducting experiments on a pulsed radiation source helps researchers estimate the expected output of the streak camera under pulsed radiation, allowing for advance adjustment of the incident pulse radiation intensity and obtaining a signal with a good signal-to-noise ratio. When the parameters of the streak camera system change, without the availability of a pulsed radiation source for testing, researchers find it difficult to quickly evaluate the response of the newly designed system. Comparing the response with the previously tested radiation pulse response of the streak camera system on a pulsed radiation source increases experimental time and reduces accuracy. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of low accuracy in calculating radiation impulse response and long experimental time and difficulty in accurately obtaining parameters of radiation impulse response of fringe camera systems in actual measurement. This invention provides a system and method for obtaining radiation impulse response.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A system for obtaining radiation impulse response, used for simulating and testing the radiation impulse response of a streak camera system, is characterized by comprising: a planar pulse light source, a mirror positioned on the light path of the planar pulse light source, a first objective lens sequentially positioned along the reflected light from the mirror, a streak camera of the streak camera system, a total reflection mirror positioned along the transmitted light from the mirror, a second objective lens sequentially positioned along the reflected light from the total reflection mirror, a photodetector, a signal source, and an oscilloscope; the signal source includes three output channels, with output channel A connected to the external trigger input terminal of the planar pulse light source, output channel B connected to the external trigger input terminal of the streak camera, and output channel C connected to the first input terminal of the oscilloscope; the second input terminal of the oscilloscope is connected to the output terminal of the photodetector;

[0008] A planar pulse light source is used to emit light pulses to simulate the scintillator of a streak camera system; a mirror splits the light pulses into two beams, a reflected beam and a transmitted beam. The reflected beam is incident on the first objective lens, and the transmitted beam is reflected by a total reflection mirror and then incident on the second objective lens; the first objective lens images the reflected beam onto the entrance slit of the streak camera; the streak camera records the incident and reflected beams and outputs the light pulse image; the second objective lens images the transmitted beam onto the photocathode surface of the photodetector; the photodetector converts the incident transmitted beam into an electrical pulse and transmits it to the oscilloscope; a signal source synchronously triggers the planar pulse light source, the streak camera, and the oscilloscope, so that the light pulses from the planar pulse light source are recorded by the streak camera and the electrical pulses converted by the photodetector are recorded by the oscilloscope.

[0009] Furthermore, the light-emitting surface of the planar pulse light source is planar, and the light emission uniformity is greater than 90%; the difference between the light emission center wavelength of the planar pulse light source and the light emission center wavelength of the scintillator of the streak camera system is less than 10 nm.

[0010] Furthermore, the center of the transmission spectrum of the first objective lens is the same as the wavelength of the scintillator emission center of the streak camera system; the object distance of the first objective lens is equal to the distance from the emitting surface of the planar pulse light source to the front surface of the incident lens of the first objective lens, and the image distance of the first objective lens is equal to the distance from the rear surface of the exit lens of the first objective lens to the slit of the streak camera.

[0011] Furthermore, the center of the transmission spectrum of the second objective lens is the same as the wavelength of the scintillator emission center of the streak camera system; the object distance of the second objective lens is equal to the distance from the emitting surface of the planar pulse light source to the front surface of the incident lens of the second objective lens, and the image distance of the second objective lens is equal to the distance from the rear surface of the exit lens of the second objective lens to the photocathode surface of the photodetector.

[0012] Furthermore, the spectral response range of the photodetector covers the scintillator emission spectrum of the streak camera system; the electrical signal timing settings of the three output channels of the signal source to the external trigger input terminal of the planar pulse light source, the external trigger input terminal of the streak camera, and the first input terminal of the oscilloscope are the same.

[0013] Furthermore, the transmission-to-reflection ratio of the transflector is (1:9) to (9:1), and the angle between its incident surface and the horizontal plane is 45 degrees; the center wavelength of the reflection spectrum of the total reflection mirror is the same as the center wavelength of the scintillator emission of the streak camera system, its reflectivity is greater than 95%, and the angle between its incident surface and the horizontal plane is 45 degrees.

[0014] Furthermore, this invention also provides a method for obtaining a radiation pulse response, which is characterized by:

[0015] 1. Construct the system described above for obtaining the radiation impulse response, and adjust the positions of each device in the system;

[0016] 2. Set the planar pulse light source, signal source, and oscilloscope to external trigger mode, and then set the delay of each output channel of the signal source; trigger the signal source to obtain the light pulse image recorded by the streak camera and the electrical pulse waveform output by the oscilloscope;

[0017] 3. Calculate the visible light pulse response R based on the light pulse image output by the streak camera and the electrical pulse waveform output by the oscilloscope. v ;

[0018] 4) Based on the visible light impulse response R v The radiation impulse response R is calculated using the following formula. γ :

[0019] R γ =R v ·k γ

[0020]

[0021] In the formula, k γ P is the radiative power conversion efficiency of the scintillator. v P is the power density of the light emitted by the scintillator. γ The power density of the radiation pulse incident on the scintillator.

[0022] Furthermore, in step 1], the positions of each device in the system are adjusted, specifically as follows:

[0023] 1.1 Make the emitting surface of the planar pulse light source coincide with the emitting surface of the scintillator in the streak camera system, and the difference between the emitting center wavelength of the planar pulse light source and the emitting center wavelength of the scintillator in the streak camera system is less than 10nm.

[0024] 1.2. The angle between the incident surface of the transparent mirror and the horizontal plane is 45 degrees, and the angle between the incident surface of the total reflection mirror and the horizontal plane is 45 degrees.

[0025] 1.3 Adjust the object distance of the first objective lens to the distance from the emitting surface of the planar pulsed light source to the front surface of the incident lens of the first objective lens, and adjust the image distance of the first objective lens to the distance from the rear surface of the exit lens of the first objective lens to the slit of the streak camera; adjust the object distance of the second objective lens to the distance from the emitting surface of the planar pulsed light source to the front surface of the incident lens of the second objective lens, and adjust the image distance of the second objective lens to the distance from the rear surface of the exit lens of the second objective lens to the photocathode surface of the photodetector.

[0026] Furthermore, step 2 specifically involves:

[0027] 2.1 Set the signal source to manual trigger mode, and set both the planar pulse light source and the oscilloscope to external trigger mode;

[0028] 2.2. Set the delay for each output channel of the signal source;

[0029] 2.2.1 Define the relaxation time of a photodetector as t. e1 The time taken for the electrical signal from the output of the photodetector to the second input of the oscilloscope is t. e2 ;

[0030] 2.2.2 Define the time required for the light pulse emitted from the output end of the planar pulse light source to reach the slit of the streak camera as t. c1 The time required for a light pulse emitted from the output of a planar pulsed light source to reach the photocathode of a photodetector is t. c2 , t c2 >t c1 The delay of a planar pulsed light source is the time difference between the starting point of receiving an external trigger signal and the starting point of emitting a light pulse.

[0031] 2.2.3 Set the electrical signal timing of the signal source's output channel A and the external trigger input terminal of the planar pulse light source, the output channel B and the external trigger input terminal of the streak camera, and the output channel C and the first input terminal of the oscilloscope to be the same:

[0032] If the delay of the planar pulsed light source is greater than or equal to the delay of the streak camera, then the delay of output channel A is set to 0, the delay of output channel B is set to the difference between the delay of the planar pulsed light source and the delay of the streak camera, and the delay of output channel C is set to the delay of the planar pulsed light source. c2 -t c1 Photodetector relaxation time t e1 The time t of the electrical signal from the output terminal of the photodetector to the second input terminal of the oscilloscope e2 sum;

[0033] If the delay of the planar pulsed light source is less than the delay of the streak camera, then the delay of output channel A is set to the difference between the delay of the streak camera and the delay of the planar pulsed light source, the delay of output channel B is set to 0, and the delay of output channel C is set to the delay of the planar pulsed light source. c2 -t c1 Photodetector relaxation time t e1 The time t of the electrical signal from the output terminal of the photodetector to the second input terminal of the oscilloscope e2 sum;

[0034] 2.3 Manually trigger the signal source to obtain the light pulse image recorded by the stripe camera and the electrical pulse waveform output by the oscilloscope.

[0035] Furthermore, step 3 specifically involves:

[0036] 3.1. Based on the electrical pulse waveform V(t) output by the oscilloscope, obtain the change in optical power density p of the planar pulsed light source output over time. ρ (t) is:

[0037]

[0038] In the formula, Ω is the input impedance of the oscilloscope (9); r oe Sensitivity of the photodetector, unit: A / W; s oe The photocathode area of ​​the photodetector, in cm². 2 η oe denoted as η, where η is the efficiency of the second objective lens; k is the ratio of the transmittance to the reflectance of the mirror.

[0039] 3.2. Based on the change in light pulse image output by the streak camera and the change in light power density output by the planar pulse light source over time, the visible light pulse response R is calculated using the following formula. v :

[0040]

[0041] In the formula, C s(m,n) represents the net grayscale value of the pixel in the m-th row and n-th column of the light pulse image output by the streak camera; Δt=T / N is the time interval corresponding to each column, T is the recording time length of the streak camera, and N is the total number of columns in the light pulse image output by the streak camera; t0 is the time when the electrical pulse at the first input terminal of the oscilloscope reaches its peak value, indicating the start time when the streak camera begins recording the light pulse.

[0042] The beneficial effects of this invention are:

[0043] 1. Compared with the prior art, the relative uncertainty of the radiation pulse response obtained by the system of the present invention is less than 100%, which greatly reduces the experimental time of the radiation pulse response of the measured fringe camera system, and can reduce its experimental time by up to about 50%.

[0044] 2. The system of the present invention can be used to compare the relative sensitivity of different streak camera systems. Without pulse radiation source testing, the radiation pulse response of several streak camera systems with different settings can be obtained.

[0045] 3. The method of this invention establishes a quantifiable visible light pulse to simulate a scintillator light pulse, so as to obtain the radiation pulse response of the streak camera system on the pulse radiation source, and provides a reference for the parameter setting of the streak camera system in the first pulse radiation source experiment.

[0046] 4. The method of the present invention can be used to estimate the radiation pulse response of a streak camera system. The test results can be compared with the response obtained on the pulse radiation source and used as a reference, which increases the reliability of the test results.

[0047] 5. The method of the present invention enables experimenters to quickly evaluate the response of a newly designed system and compare it with the radiation pulse response of a streak camera system that has been tested on a pulse radiation source. This reduces the pressure of conducting experiments on a pulse radiation source, accelerates the system design iteration speed, and can also serve as a reference supplement to the radiation pulse response results of a streak camera system measured on a pulse radiation source, so as to avoid the errors that may be caused by using only one method. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0049] Figure 2 This is a schematic diagram of obtaining the electrical pulse (blue) of the signal source output channel C and the electrical pulse (red) of the photodetector on an oscilloscope in an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of reading the net grayscale value of the pixel in the 200th row and 700th column of the light pulse image output by the stripe camera, which is 2130 ADUs, in an embodiment of the present invention.

[0051] Explanation of reference numerals in the attached figures:

[0052] 1-Planar pulse light source, 2-Transparent mirror, 3-First objective lens, 4-Stripe camera, 5-Total reflection mirror, 6-Second objective lens, 7-Photodetector, 8-Signal source, 9-Oscilloscope. Detailed Implementation

[0053] like Figure 1 As shown, a system for obtaining radiation pulse response, used for simulating and testing the radiation pulse response of a streak camera system, includes a planar pulse light source 1, a mirror 2 positioned on the optical pulse path of the planar pulse light source 1, a first objective lens 3 sequentially positioned along the reflected light from the mirror 2, a streak camera 4 of the streak camera system, a total reflection mirror 5 positioned along the transmitted light from the mirror 2, a second objective lens 6 sequentially positioned along the reflected light from the total reflection mirror 5, a photodetector 7, a signal source 8, and an oscilloscope 9. The signal source 8 includes three independently adjustable output channels. Output channel A is connected to the external trigger input terminal of the planar pulse light source 1, output channel B is connected to the external trigger input terminal of the streak camera 4, and output channel C is connected to the first input terminal of the oscilloscope 9, used to record the electrical pulse output by signal channel C of the signal source 8, which characterizes the moment when the streak camera 4 starts working. The second input terminal of the oscilloscope 9 is connected to the output terminal of the photodetector 7, used to record the electrical pulse output from the photodetector 7, which represents the light power density (unit: W / cm²) emitted by the planar pulse light source 1. 2 Changes over time.

[0054] Planar pulse light source 1 is used to emit light pulses to simulate the scintillator of the streak camera system; the emission center wavelength of the planar pulse light source 1 is similar to that of the scintillator, with a difference of less than 10 nm; the transmission mirror 2 is used to split the light pulse into two beams, namely reflected light and transmitted light, the reflected light is incident on the first objective lens 3, and the transmitted light is incident on the second objective lens 6 after being reflected by the total reflection mirror 5; the first objective lens 3 is used to image the reflected light at the entrance slit of the streak camera 4; the streak camera 4 is used to record the incident reflected light and output the light pulse image; the second objective lens 6 is used to image the transmitted light on the photocathode surface of the photodetector 7; the photodetector 7 is used to convert the incident transmitted light into electrical pulses and transmit them to the oscilloscope 9; the signal source 8 is used to synchronously trigger the planar pulse light source 1, the streak camera 4, and the oscilloscope 9, so that the light pulse of the planar pulse light source 1 is recorded by the streak camera 4 and the electrical pulse converted by the photodetector 7 is recorded by the oscilloscope 9.

[0055] The planar pulse light source 1 in the system of this invention has an external triggering function. After receiving an external triggering signal, it can emit light pulses. The delay of the planar pulse light source 1 is known. Its delay is the time difference between the starting point of the planar pulse light source 1 receiving the external triggering signal and the starting point of the emitted light pulse. The starting point is the moment closest to 1 / 10 of the pulse peak value in the pulse moment before the pulse peak value. The emitting surface of the planar pulse light source 1 coincides with the emitting surface of the scintillator in the streak camera system. The emitting surface of the planar pulse light source 1 is planar, and the emitting uniformity is greater than 90%. The emitting center wavelength of the planar pulse light source 1 is similar to the emitting center wavelength of the scintillator, and the difference between the two is less than 10 nm.

[0056] The transmission-reflection ratio of the transflector 2 varies with the incident light spectrum and is obtained through calibration. The transmission-reflection ratio at the center wavelength of the scintillator can be read from the calibration results. The transmission-reflection ratio of the transflector 2 is generally between (1:9) and (9:1). The incident surface of the transflector 2 faces the output surface of the planar pulse light source 1 and is rotated 45 degrees in the horizontal plane.

[0057] The transmission spectrum center of the first objective lens 3 has the same wavelength as the luminous center of the scintillator; the first objective lens 3 is placed in a suitable position in the system such that the object distance of the first objective lens 3 is equal to the distance from the luminous surface of the planar pulse light source 1 to the front surface of the incident lens of the first objective lens 3, and the image distance of the first objective lens 3 is equal to the distance from the rear surface of the exit lens of the first objective lens 3 to the slit of the streak camera 4.

[0058] The stripe camera 4 operates in an externally triggered state; the slit width of the stripe camera 4 is the same as that in the experiment on the pulse radiation source; the delay of the stripe camera 4 is known; the scan range of the stripe camera 4 is known, and thus the time width Δt corresponding to each column of pixels on the output light pulse image of the stripe camera 4 is obtained by dividing the scan range by the number of image columns.

[0059] The center wavelength of the reflection spectrum of the total reflection mirror 5 is the same as the center wavelength of the scintillator's emission, and the reflectivity is greater than 95%. The incident surface of the total reflection mirror 5 faces the output surface of the planar pulse light source 1 and is rotated 45 degrees in the horizontal plane.

[0060] The transmission spectrum center of the second objective lens 6 has the same wavelength as the luminous center of the scintillator; the second objective lens 6 is placed in a suitable position in the system such that the object distance of the second objective lens 6 is equal to the distance from the luminous surface of the planar pulse light source 1 to the front surface of the incident lens of the second objective lens 6, and the image distance of the second objective lens 6 is equal to the distance from the rear surface of the exit lens of the second objective lens 6 to the photocathode surface of the photodetector 7.

[0061] The output terminal of photodetector 7 is connected to the second input terminal of oscilloscope 9 via a cable. The relaxation time of photodetector 7 is known; it is the time interval t between the moment the light pulse is incident on the photocathode of photodetector 7 and the moment when photodetector 7 begins to output an electrical pulse. e1The time taken for the electrical signal from the output of photodetector 7 to the second input of oscilloscope 9 is t. e2 The spectral response range of photodetector 7 should cover the scintillator emission spectrum of the streak camera system; the sensitivity of photodetector 7 at the center wavelength of the scintillator is known; the photocathode area of ​​photodetector 7 is known.

[0062] The time required for the light pulse emitted from the output of the planar pulse light source 1 to reach the slit of the stripe camera 4 is t. c1 The time required for the light pulse emitted from the output end of the planar pulse light source 1 to reach the photocathode of the photodetector 7 is t. c2 , t c2 >t c1 .

[0063] The electrical signal timing settings of the output channel A of signal source 8 and the external trigger input terminal of planar pulse light source 1 are the same as those of the output channel B and the external trigger input terminal of streak camera 4, and the first input terminal of output channel C and oscilloscope 9.

[0064] If the delay of the planar pulse light source 1 is greater than or equal to the delay of the streak camera 4, then the delay of output channel A is set to 0, the delay of output channel B is set to the difference between the delay of the planar pulse light source 1 and the delay of the streak camera 4, and output channel C is used to mark the start time of recording by the streak camera 4 on the oscilloscope 9. Therefore, the delay of output channel C is set to the delay of the planar pulse light source 1. c2 -t c1 7. Relaxation time t of the photodetector e1 The time t of the electrical signal from the output terminal of photodetector 7 to the second input terminal of oscilloscope 9 e2 sum.

[0065] If the delay of the planar pulse light source 1 is less than the delay of the streak camera 4, then the delay of output channel A is set to the difference between the delay of the streak camera 4 and the delay of the planar pulse light source 1, the delay of output channel B is set to 0, and output channel C is used to mark the start time of the streak camera 4 recording on the oscilloscope 9. Therefore, the delay of output channel C is set to the delay of the planar pulse light source 1. c2 -t c1 7. Relaxation time t of the photodetector e1 The time t of the electrical signal from the output terminal of photodetector 7 to the second input terminal of oscilloscope 9 e2 sum.

[0066] The first input terminal of the oscilloscope 9 is connected to the output channel C of the signal source 8. The electrical pulse input to this channel represents the moment when the stripe camera 4 starts working. The second input terminal is connected to the output terminal of the photodetector 7 and is used to record the electrical pulse output from the photodetector 7. This electrical pulse is the light pulse emitted by the planar pulse light source 1, which is converted by the photodetector 7 and then output by the oscilloscope 9 as the electrical pulse waveform V(t), representing the form of the change of the light power density emitted by the planar pulse light source 1 with time.

[0067] The working principle of the system that obtains the radiation impulse response is as follows:

[0068] The output light pulse image of the streak camera 4 is oriented along the time axis (rows) and the spatial axis (columns). The output light pulse image of the streak camera 4 is defined as consisting of M rows and N columns of pixels, and the net grayscale values ​​of all pixels are represented by an M row and N column array C. s In other words, C s (m,n) represents the net gray value of the pixel in the m-th row and n-th column of the light pulse image output by the stripe camera 4, where 1≤m≤M and 1≤n≤N. The number of pixels in the light pulse image output by the stripe camera 4 is determined by the number of pixels of the digital camera configured with the stripe camera 4. For example, if the number of pixels of the digital camera is 1024×768, then M=1024 and N=768. If the number of pixels of the digital camera is 4096×4096, then M=4096 and N=4096.

[0069] Let T be the recording time length of the streak camera 4. Then, the time interval Δt = TN corresponds to each column. The time of the first column is the starting point of the recording length, the time of the second column is Δt, the time of the third column is 2Δt, and so on until the time of the Nth column is (N-1)Δt. Let R be the visible light pulse response. v Then, the net gray value C of the pixel in the m-th row and n-th column of the output light pulse image of the stripe camera 4 is... s (Unit: ADUs) and the light power density p on the emitting surface of the planar pulsed light source 1 at the corresponding moment of the pixel. ρ (Unit: W / cm) 2 The ratio of (unit: ADUs·cm) 2 / W), that is, the visible light pulse response is R v :

[0070]

[0071] The system of this invention uses a photodetector 7 with known sensitivity to measure the optical power density p output by the planar pulsed light source 1. ρ A stripe camera 4 records the light pulses from a planar pulse light source 1, and the net grayscale value C of the pixels in the light pulse image output by the stripe camera 4 is read. s (m,n), and thus the visible light pulse response R of the streak camera 4 is obtained. v .

[0072] The electrical pulse output of photodetector 7, recorded on oscilloscope 9, varies with time. The electrical pulse waveform is V(t) (unit: volts, V). Based on the electrical pulse waveform V(t), the output optical power density p of planar pulse light source 1 can be obtained. ρ The change of p over time ρ (t) is:

[0073]

[0074] In the formula, Ω is the impedance of the channel between the output terminal of the photodetector 7 and the oscilloscope 9; r oe The sensitivity of photodetector 7, in A / W, represents the output current r of photodetector 7 when the incident light power of the photocathode is 1W. oe Ampere; s oe The photocathode area of ​​photodetector 7, in cm². 2 η oe The efficiency of the second objective lens 6 is the ratio of the light power density on its image surface to the light power density on its object surface; k is the ratio of the transmittance to the reflectance of the transmission mirror 2 (i.e., the transmittance-reflectance ratio), and the reflectance of the transmission mirror 2 is... transmittance

[0075] The electrical pulse at the first input terminal of oscilloscope 9 is output from channel C of signal source 8, with a start time of t0. According to the settings of channel C of signal source 8, t0 represents the start time when the streak camera 4 begins recording the light pulse. Therefore, the visible light pulse response R... v The net gray value C of any row of pixels in the nth column of the light pulse image output by the stripe camera 4. s (m,n) and the corresponding optical power density p ρ The ratio yields:

[0076]

[0077] Let the scintillator's radiative power conversion efficiency be k. γ Its power density P is emitted by the scintillator. v With incident radiation pulse power density P γ The ratio is:

[0078]

[0079] The radiation impulse response R of the streak camera system can then be obtained using the following formula. γ :

[0080] R γ =R v ·k γ .

[0082] The system of this invention can be used to estimate the radiation pulse response of a streak camera system, providing a reference for determining the appropriate settings for the first pulsed radiation source experiment. It can compare the relative sensitivity of the streak camera system under different settings, obtain the radiation pulse response of the streak camera system without pulsed radiation source testing, and compare the test results with the response obtained on the pulsed radiation source, thus increasing the reliability of the test results.

[0083] The present invention also provides a method for obtaining a radiation impulse response, comprising the following steps:

[0084] 1. Construct the system described above for obtaining the radiation impulse response, and adjust the positions of each device in the system;

[0085] 1.1 Make the emitting surface of the planar pulse light source 1 coincide with the emitting surface of the scintillator in the streak camera system, and make the difference between the emitting center wavelength of the planar pulse light source 1 and the emitting center wavelength of the scintillator in the streak camera system less than 10nm.

[0086] 1.2. Make the angle between the incident surface of the transparent mirror 2 and the horizontal plane 45 degrees, and the angle between the incident surface of the total reflection mirror 5 and the horizontal plane 45 degrees.

[0087] 1.3 Adjust the object distance of the first objective lens 3 to the distance from the emitting surface of the planar pulse light source 1 to the front surface of the incident lens of the first objective lens 3, and adjust the image distance of the first objective lens 3 to the distance from the rear surface of the exit lens of the first objective lens 3 to the slit of the streak camera 4; adjust the object distance of the second objective lens 6 to the distance from the emitting surface of the planar pulse light source 1 to the front surface of the incident lens of the second objective lens 6, and adjust the image distance of the second objective lens 6 to the distance from the rear surface of the exit lens of the second objective lens 6 to the photocathode surface of the photodetector 7;

[0088] 2】Set the planar pulse light source 1, signal source 8, and oscilloscope 9 to external trigger mode respectively, and then set the delay of each output channel of signal source 8; trigger signal source 8 to obtain the light pulse image recorded by stripe camera 4 and the electrical pulse waveform output by oscilloscope 9;

[0089] 2.1 Set signal source 8 to manual trigger mode, and set both planar pulse light source 1 and oscilloscope 9 to external trigger mode;

[0090] 2.2. Set the delay of each output channel of signal source 8;

[0091] 2.2.1 Define the relaxation time of photodetector 7 as t. e1 The time taken for the electrical signal from the output of photodetector 7 to the second input of oscilloscope 9 is t. e2 ;

[0092] 2.2.2 Define the time t required for the light pulse emitted from the output end of the planar pulse light source 1 to reach the slit of the streak camera 4. c1 The time required for the light pulse emitted from the output end of the planar pulse light source 1 to reach the photocathode of the photodetector 7 is t. c2 , t c2 >t c1 The delay of the planar pulse light source 1 is the time difference between the starting point of receiving the external trigger signal and the starting point of emitting the light pulse.

[0093] 2.2.3 Set the electrical signal timing of the output channel A of signal source 8 and the external trigger input terminal of planar pulse light source 1, the output channel B of signal source 8 and the external trigger input terminal of streak camera 4, and the output channel C of signal source 8 and the first input terminal of oscilloscope 9 to be the same:

[0094] If the delay of the planar pulse light source 1 is greater than or equal to the delay of the streak camera 4, then the delay of output channel A is set to 0, the delay of output channel B is set to the difference between the delay of the planar pulse light source 1 and the delay of the streak camera 4, and the delay of output channel C is set to the delay of the planar pulse light source 1. c2 -t c1 7. Relaxation time t of the photodetector e1 The time t of the electrical signal from the output terminal of photodetector 7 to the second input terminal of oscilloscope 9 e2 sum.

[0095] If the delay of the planar pulse light source 1 is less than the delay of the streak camera 4, then the delay of output channel A is set to the difference between the delay of the streak camera 4 and the delay of the planar pulse light source 1, the delay of output channel B is set to 0, and the delay of output channel C is set to the delay of the planar pulse light source 1. c2 -t c1 7. Relaxation time t of the photodetector e1 The time t of the electrical signal from the output terminal of photodetector 7 to the second input terminal of oscilloscope 9 e2 sum.

[0096] 2.3 Manually trigger signal source 8 to obtain the light pulse image recorded by stripe camera 4 and the electrical pulse waveform output by oscilloscope 9.

[0097] 3】Calculate the visible light pulse response based on the light pulse image output by the stripe camera 4 and the electrical pulse waveform output by the oscilloscope 9;

[0098] 3.1. Based on the electrical pulse waveform V(t) output by oscilloscope 9, obtain the change in optical power density p of the planar pulse light source 1 over time. ρ (t) is:

[0099]

[0100] In the formula, Ω is the input impedance of oscilloscope 9; r oe The sensitivity of photodetector 7 is expressed in A / W; s. oe The photocathode area of ​​photodetector 7, in cm². 2 η oe denoted as η, where η is the efficiency of the second objective lens 6; and η is the ratio of the transmittance to the reflectance of the mirror 2.

[0101] 3.2. Based on the output light pulse image of the streak camera 4 and the change in output light power density of the planar pulse light source 1 over time, the visible light pulse response R is calculated using the following formula. v :

[0102]

[0103] In the formula, C s (m,n) represents the net grayscale value of the pixel in the m-th row and n-th column of the light pulse image output by the stripe camera 4; Δt=T / N is the time interval corresponding to each column, T is the recording time length of the stripe camera 4, and N is the total number of columns in the light pulse image output by the stripe camera 4; time t0 represents the start time when the stripe camera 4 begins recording the light pulse.

[0104] 4) Based on the visible light impulse response R v The radiation impulse response R is calculated using the following formula. γ :

[0105] R γ =R v ·k γ

[0106]

[0107] In the formula, k γ P is the radiative power conversion efficiency of the scintillator. v P is the power density of the light emitted by the scintillator. γ The power density of the radiation pulse incident on the scintillator.

[0108] In this embodiment, the scintillator used in the streak camera system is a 5mm BC408 with an emission range of 390-450nm; the radiation pulse is an X-ray pulse with an average energy of 0.3MeV for the radiated photons; and the radiative power conversion efficiency k of the 5mm BC408 scintillator for the X-ray pulse is... γ It is 7.1×10 -4 .

[0109] The planar pulsed light source 1 uses a pulsed xenon lamp. The output of the pulsed xenon lamp is modulated by a filter with a center wavelength of 420 nm and a transmission half-width of 30 nm. The output light of the pulsed xenon lamp is similar to that of a scintillator. After passing through a homogenizer, it is reflected multiple times on the inner wall of the homogenizer before exiting from the output port. Its uniformity is >95%, and the diameter of the output port of the pulsed xenon lamp is 10 cm. The transmission-to-reflection ratio of the transmission mirror 2 is 1:1; the reflectivity of the total reflection mirror 5 is greater than 95%; the object distance of the first objective lens 3 is 55 cm, the image distance is 5 cm, and the efficiency is 0.02; the object distance of the second objective lens 6 is 95 cm, the image distance is 5 cm, and the efficiency is 0.01. The scan path of the streak camera 4 is 483 ns. The streak camera 4 outputs a total of 1280 columns of light pulse images, so each column represents a time length Δt = 0.377 ns.

[0110] The delay of the stripe camera 4 is 100ns, the delay of the pulsed xenon lamp is 5000ns, the relaxation time of the photodetector 7 is 50ns, and the electrical signal between the output terminal of the photodetector 7 and the second input terminal of the oscilloscope 9 is 10ns. According to the method of the present invention, the delay of each output channel of the signal source 8 is set, the delay of output channel A is set to 0ns, the delay of output channel B is set to 4900ns, the delay of output channel C is set to 5061.4ns, the output amplitude of output channel C is 3V, and the pulse width is 10ns.

[0111] Turn on all devices and manually trigger signal source 8 to obtain the light pulse image output by stripe camera 4. For example... Figure 2 As shown, the electrical pulse (blue) of the output channel C of the signal source 8 and the electrical pulse (red) of the photodetector 7 are obtained on the oscilloscope 9. The starting time of the electrical pulse of the output channel C corresponds to t0 = 0.5ns.

[0112] The oscilloscope 9 has an input impedance of 50 ohms, and the photocathode area of ​​the photodetector 7 is 1 cm². 2 The efficiency of the second objective lens 6 is 0.01, and the sensitivity of the photodetector 7 is 3 × 10⁻⁶. 5 A / W, the optical power density p at the output surface of the planar pulsed light source 1 can be obtained by calculation. ρ (t):

[0113]

[0114] like Figure 3 As shown, based on the light pulse image output by the streak camera 4, the net grayscale value of the pixel in row 200 and column 700 is read as 2130 ADUs. Therefore, the visible light pulse response is R. v for:

[0115]

[0116] The radiation impulse response R of the streak camera system is obtained from the visible light response.γ :

[0117] R γ =R v ·k γ

[0118] =7.38×10 5 ×7.1×10 -4

[0119] =5.24×10 2 ADUscm 2 / W。

Claims

1. A system for obtaining radiation impulse response, used for simulating and testing the radiation impulse response of a streak camera system, characterized in that: The system includes a planar pulse light source (1), a transflector (2) disposed on the light path of the planar pulse light source (1), a first objective lens (3) disposed sequentially along the reflected light of the transflector (2), a streak camera (4) of a streak camera system, a total reflection mirror (5) disposed along the transmitted light of the transflector (2), a second objective lens (6) disposed sequentially along the reflected light of the total reflection mirror (5), a photodetector (7), a signal source (8), and an oscilloscope (9). The signal source (8) includes three output channels. Output channel A is connected to the external trigger input terminal of the planar pulse light source (1), output channel B is connected to the external trigger input terminal of the stripe camera (4), and output channel C is connected to the first input terminal of the oscilloscope (9). The second input terminal of the oscilloscope (9) is connected to the output terminal of the photodetector (7). The planar pulse light source (1) is used to emit light pulses to simulate the scintillator of the streak camera system; the reflective mirror (2) is used to split the light pulse into two beams, namely reflected light and transmitted light, the reflected light is incident on the first objective lens (3), and the transmitted light is incident on the second objective lens (6) after being reflected by the total reflection mirror (5); the first objective lens (3) is used to image the reflected light at the entrance slit of the streak camera (4); the streak camera (4) is used to record the incident reflected light and output the light pulse image; the second objective lens (6) is used to image the transmitted light on the photocathode surface of the photodetector (7); the photodetector (7) is used to convert the incident transmitted light into electrical pulses and transmit them to the oscilloscope (9); the signal source (8) is used to synchronously trigger the planar pulse light source (1), the streak camera (4), and the oscilloscope (9), so that the light pulse of the planar pulse light source (1) is recorded by the streak camera (4) and the electrical pulse converted by the photodetector (7) is recorded by the oscilloscope (9).

2. The system for obtaining a radiation impulse response according to claim 1, characterized in that: The planar pulse light source (1) has a planar light-emitting surface and a light emission uniformity greater than 90%; the difference between the light emission center wavelength of the planar pulse light source (1) and the light emission center wavelength of the scintillator of the stripe camera system is less than 10 nm.

3. The system for obtaining a radiation impulse response according to claim 1, characterized in that: The transmission spectrum center of the first objective lens (3) is the same as the wavelength of the scintillator emission center of the streak camera system; the object distance of the first objective lens (3) is equal to the distance from the emitting surface of the planar pulse light source (1) to the front surface of the incident lens of the first objective lens (3); the image distance of the first objective lens (3) is equal to the distance from the rear surface of the exit lens of the first objective lens (3) to the slit of the streak camera (4).

4. The system for obtaining a radiation impulse response according to claim 1, characterized in that: The transmission spectrum center of the second objective (6) is the same as the wavelength of the scintillator emission center of the streak camera system; the object distance of the second objective (6) is equal to the distance from the emitting surface of the planar pulse light source (1) to the front surface of the incident lens of the second objective (6); the image distance of the second objective (6) is equal to the distance from the rear surface of the exit lens of the second objective (6) to the photocathode surface of the photodetector (7).

5. The system for obtaining a radiation impulse response according to claim 1, characterized in that: The spectral response range of the photodetector (7) covers the scintillator emission spectrum of the streak camera system; The electrical signal timing settings of the three output channels of the signal source (8) to the external trigger input terminal of the planar pulse light source (1), the external trigger input terminal of the stripe camera (4), and the first input terminal of the oscilloscope (9) are the same.

6. The system for obtaining a radiation impulse response according to any one of claims 1 to 5, characterized in that: The transmission-to-reflection ratio of the mirror (2) is (1:9) to (9:1), and the angle between its incident surface and the horizontal plane is 45 degrees. The center wavelength of the reflection spectrum of the total reflection mirror (5) is the same as the center wavelength of the scintillator emission of the streak camera system, its reflectivity is greater than 95%, and the angle between the incident surface and the horizontal plane is 45 degrees.

7. A method for obtaining a radiation impulse response, characterized in that:

1. Construct a system for obtaining a radiation pulse response as described in any one of claims 1 to 6, and adjust the positions of each device in the system; 2】Set the planar pulse light source (1), signal source (8), and oscilloscope (9) to external trigger mode respectively, and then set the delay of each output channel of the signal source (8); Trigger signal source (8) to obtain the light pulse image recorded by stripe camera (4) and the electrical pulse waveform output by oscilloscope (9); 3】Calculate the visible light pulse response R based on the light pulse image output by the streak camera (4) and the electrical pulse waveform output by the oscilloscope (9). v ; 4) Based on the visible light impulse response R v The radiation impulse response R is calculated using the following formula. γ : R γ =R v ·k γ In the formula, k γ P is the radiative power conversion efficiency of the scintillator. v P is the power density of the light emitted by the scintillator. γ The power density of the radiation pulse incident on the scintillator.

8. The method for obtaining a radiation impulse response according to claim 7, characterized in that, Step 1】 refers to adjusting the positions of each device in the system, specifically as follows: 1.1 Make the emitting surface of the planar pulse light source (1) coincide with the emitting surface of the scintillator in the streak camera system, and the difference between the emitting center wavelength of the planar pulse light source (1) and the emitting center wavelength of the scintillator in the streak camera system is less than 10nm. 1.2 Make the angle between the incident surface of the transparent mirror (2) and the horizontal plane 45 degrees, and the angle between the incident surface of the total reflection mirror (5) and the horizontal plane 45 degrees. 1.3 Adjust the object distance of the first objective lens (3) to the distance from the emitting surface of the planar pulse light source (1) to the front surface of the incident lens of the first objective lens (3), and adjust the image distance of the first objective lens (3) to the distance from the rear surface of the exit lens of the first objective lens (3) to the slit of the streak camera (4); adjust the object distance of the second objective lens (6) to the distance from the emitting surface of the planar pulse light source (1) to the front surface of the incident lens of the second objective lens (6), and adjust the image distance of the second objective lens (6) to the distance from the rear surface of the exit lens of the second objective lens (6) to the photocathode surface of the photodetector (7).

9. The method for obtaining a radiation impulse response according to claim 8, characterized in that, Step 2 is as follows: 2.1 Set the signal source (8) to manual trigger mode, and set the planar pulse light source (1) and oscilloscope (9) to external trigger mode; 2.

2. Set the delay of each output channel of the signal source (8); 2.2.1 Define the relaxation time of the photodetector (7) as t e1 The time taken for the electrical signal from the output of the photodetector (7) to the second input of the oscilloscope (9) is t. e2 ; 2.2.

2. Define the time required for the light pulse emitted from the output end of the planar pulse light source (1) to reach the slit of the streak camera (4) as t. c1 The time required for the light pulse emitted from the output end of the planar pulse light source (1) to reach the photocathode of the photodetector (7) is t. c2 , t c2 >t c1 The delay of the planar pulse light source (1) is the time difference between the starting point of the planar pulse light source (1) from the starting point of receiving the external trigger signal to the starting point of emitting the light pulse; 2.2.3 Set the electrical signal timing of the output channel A of the signal source (8), the external trigger input terminal of the planar pulse light source (1), the output channel B of the signal source (8), the external trigger input terminal of the streak camera (4), the output channel C of the signal source (4), and the first input terminal of the oscilloscope (9) to be the same: If the delay of the planar pulse light source (1) is greater than or equal to the delay of the streak camera (4), then the delay of output channel A is set to 0, the delay of output channel B is set to the difference between the delay of the planar pulse light source (1) and the delay of the streak camera (4), and the delay of output channel C is set to the delay of the planar pulse light source (1) and t. c2 -t c1 , Photodetector (7) relaxation time t e1 The electrical signal time t from the output terminal of the photodetector (7) to the second input terminal of the oscilloscope (9) e2 sum; If the delay of the planar pulse light source (1) is less than the delay of the streak camera (4), then the delay of output channel A is set to the difference between the delay of the streak camera (4) and the delay of the planar pulse light source (1), the delay of output channel B is set to 0, and the delay of output channel C is set to the delay of the planar pulse light source (1) and t. c2 -t c1 , Photodetector (7) relaxation time t e1 The electrical signal time t from the output terminal of the photodetector (7) to the second input terminal of the oscilloscope (9) e2 sum; 2.3 Manually trigger the signal source (8) to obtain the light pulse image recorded by the stripe camera (4) and the electrical pulse waveform output by the oscilloscope (9).

10. The method for obtaining a radiation impulse response according to claim 9, characterized in that, Step 3】Specifically: 3.

1. Based on the electrical pulse waveform V(t) output by the oscilloscope (9), obtain the change in optical power density p of the planar pulse light source (1) over time. ρ (t) is: In the formula, Ω is the input impedance of the oscilloscope (9); r oe Sensitivity of photodetector (7), unit: A / W; s oe The photocathode area of ​​the photodetector (7), in cm². 2 ; η oe is the efficiency of the second objective lens (6); k is the ratio of the transmittance to the reflectance of the mirror (2); 3.

2. Based on the output light pulse image of the streak camera (4) and the change in output light power density of the planar pulse light source (1) over time, the visible light pulse response R is calculated using the following formula. v : In the formula, C s (m,n) is the net gray value of the pixel in the m-th row and n-th column of the light pulse image output by the stripe camera (4); Δt=T / N is the time interval corresponding to each column, T is the recording time length of the stripe camera (4), and N is the total number of columns of the light pulse image output by the stripe camera (4); t0 is the time when the electrical pulse at the first input terminal of the oscilloscope (9) reaches its peak value, indicating the start time when the stripe camera (4) begins to record the light pulse.

Images