A photodetector with ultra-high time resolution and method of using the same

Abstract

The present invention relates to a photoelectric detector with ultra-high time resolution and a method for its use, aiming to address the current technical issues of high noise and electrical breakdown in streak tubes when achieving high time resolution detection requirements. The photoelectric detector comprises a streak tube unit, a high- and low-voltage power supply system, a gated acceleration pulse generator, a scanning deflection signal generating circuit, a pulse feed circuit, a trigger system, and a beam splitter. The method comprises: 1. Activating the high- and low-voltage power supply system to provide a DC voltage to the streak tube unit; 2. Enabling the voltage of the photocathode to be higher than that of the acceleration system, and cutting off the streak tube unit; 3. The beam splitter receives a superluminal pulse signal to be measured, and the photocathode generates a photoelectron image; 4. Enabling the streak tube unit, the photoelectron image is sequentially transmitted and then enters a scanning deflection system; 5. The scanning deflection system scans the photoelectron image and outputs the photoelectron image to a fluorescent screen, thereby detecting the superluminal pulse signal to be measured.

Description

Technical Field

[0001] The present invention relates to a photoelectric detector, and in particular to a photoelectric detector with ultra-high time resolution and a method for using the same. Background Art

[0002] Currently, the field of high-energy-density physics faces numerous challenges, including the study of inertial confinement fusion implosion dynamics, plasma formation, plasma fusion, the development of plasma instabilities, the physical mechanisms of energy transport in plasmas, transient diagnostics of high-energy-density materials, and the properties of warm, dense matter. These research challenges have a significant impact on understanding fundamental physical laws and future energy and weapons research. As we approach extreme physical states where our understanding is limited, we need high-time-resolution photodetectors to detect microscopic and ultrafast processes under these extreme conditions.

[0003] Streak cameras are currently the only high-temporal-resolution diagnostic tool for ultrafast phenomena, playing an irreplaceable role in ultrafast research with ultrahigh temporal resolution. This is particularly true for the diagnosis of optical pulses in the picosecond to sub-femtosecond range, where streak tubes with sub-femtosecond temporal resolution can better meet the detection needs of these areas.

[0004] The temporal resolution of a streak tube is generally improved by increasing the electric field strength near the photocathode. A strong electric field near the photocathode can reduce physical time dispersion. Furthermore, the high energy provided by the strong field shortens the travel time of the photoelectron pulse in the streak tube, increasing the average travel speed and reducing dynamic scanning time dispersion.

[0005] However, the above-mentioned scheme for achieving high temporal resolution has the following disadvantages: continuous DC high voltage will increase the conduction current and thus increase the noise of the streak tube, and even cause serious consequences such as high-voltage electrical breakdown; due to the limitation of electrical breakdown, the field strength near the photocathode is no higher than 10MV / m. Summary of the Invention

[0006] The purpose of the present invention is to solve the technical problems of high noise and easy electrical breakdown of streak tubes when achieving high time resolution detection requirements, and to propose an ultra-high time resolution photoelectric detector and a method for using it.

[0007] The technical solution provided by the present invention is:

[0008] A photoelectric detector with ultra-high time resolution, which is special in that it includes a streak tube unit, a high and low voltage power supply system, a gate acceleration pulse generator, a scanning deflection signal generation circuit, a pulse feeding circuit, a trigger system and a beam splitter;

[0009] The streak tube unit is arranged in a vacuum chamber and includes a photocathode, an acceleration system, a focusing system, an anode system, a scanning deflection system, and a fluorescent screen, which are arranged in sequence along the electron transmission direction; the photocathode is used to generate a photoelectron image that is completely consistent in time and space with the ultra-light pulse signal to be measured; the acceleration system is used to provide a DC acceleration voltage for the photoelectrons in the photoelectron image generated by the photocathode; the focusing system is used to focus the photoelectrons in time and space; the anode system is used to correct the distribution of the photoelectrons in the photoelectron image in the time direction and provide the acceleration voltage; the scanning deflection system is used to provide a high-slope spatiotemporal scanning signal to convert the time information of the photoelectron image into spatial information; and the fluorescent screen is used to convert the photoelectron image into an optical image.

[0010] The beam splitter is used to receive the super-optical pulse signal to be measured and split it into a first super-optical pulse signal and a second super-optical pulse signal; the second super-optical pulse signal enters the trigger system, and the first super-optical pulse signal enters the photocathode; one output end of the trigger system is connected to the gate acceleration pulse generator, and the other output end is connected to the scanning deflection signal generating circuit; the gate acceleration pulse generator is used to generate a gate pulse acceleration voltage signal, and the scanning deflection signal generating circuit is used to generate a ramp scanning signal; the output end of the gate acceleration pulse generator is connected to the pulse feeding circuit, and the output end of the pulse feeding circuit is connected to the input end of the photocathode; the output end of the scanning deflection signal generating circuit is connected to the scanning deflection system;

[0011] The output ends of the high and low voltage power supply systems are respectively connected to the photocathode, the acceleration system, the focusing system, the anode system, the scanning deflection system and the fluorescent screen in the streak tube unit.

[0012] Furthermore, the waveform of the gate pulse acceleration voltage signal generated by the gate acceleration pulse generator is a sine wave or a shrunk sine wave.

[0013] Furthermore, the photocathode is a planar photocathode;

[0014] The acceleration system is a planar acceleration system.

[0015] Furthermore, the photocathode is an S20 visible light cathode;

[0016] The acceleration system is a slit-type acceleration system.

[0017] Furthermore, the focusing system is an electrostatic focusing system, a magnetic focusing system or an anisotropic focusing system.

[0018] Furthermore, the output end of the anode system has a slit, and the width of the slit is 10 μm to 100 μm.

[0019] Furthermore, the scanning deflection system is a parallel plate deflector, a traveling wave deflector or a flat folded plate deflector.

[0020] Furthermore, the high and low voltage power supply system is a push-pull power supply system or a resistance voltage divider power supply system.

[0021] The present invention also provides a method for using the above-mentioned ultra-high time-resolution photodetector, which is special in that it includes the following steps:

[0022] S1. Start the high and low voltage power supply system to supply power to the photocathode, acceleration system, focusing system, anode system, scanning deflection system and fluorescent screen, and provide a stable DC voltage value for the photocathode, acceleration system, focusing system, anode system, scanning deflection system and fluorescent screen, and the voltage V c Higher than the acceleration system voltage V m ;

[0023] The voltage difference between the photocathode and the acceleration system is V c-m , and the streak tube unit is in the cut-off state;

[0024] S2, the beam splitter receives the super optical pulse signal to be measured and splits it into a first super optical pulse signal and a second super optical pulse signal;

[0025] The first ultra-light pulse signal is directly transmitted to the photocathode;

[0026] The second super optical pulse signal is input into the trigger system, which triggers the strobe acceleration pulse generator to generate a strobe pulse acceleration voltage signal V g (t), and triggering the scanning deflection signal generating circuit to generate a ramp scanning signal;

[0027] Strobe pulse acceleration voltage signal V g (t) is applied to the photocathode through the pulse feeding circuit, forming the actual voltage value V of the photocathode g (t)+V c , the actual voltage value V g (t)+V c Under the action of the first beam of ultra-light pulse signal to be measured, the photocathode generates a photoelectron image that is completely consistent with the ultra-light pulse signal to be measured in time and space;

[0028] S3, the strobe pulse acceleration voltage signal V g (t) under the action of the acceleration system voltage V m ≥V g (t)+V c , the streak tube unit is in the gated acceleration state;

[0029] The photoelectrons of the photoelectron image generated by the photocathode move to the acceleration system, and then are focused in time and space by the focusing system. After being accelerated and corrected in time by the anode system, they enter the scanning deflection system.

[0030] S4. The scanning deflection system generates a ramp scanning signal in response to triggering of the scanning deflection signal generating circuit, and scans the photoelectron image at a scanning speed greater than 2c, where c is the speed of light, to convert the temporal information in the photoelectron image into spatial information.

[0031] S5. The scanning deflection system transmits the photoelectron image to the fluorescent screen, which converts the electronic image into an optical image to detect the ultra-light pulse signal to be measured.

[0032] Furthermore, in step S3, the strobe pulse acceleration voltage signal V g The peak voltage of (t) is V c-m +10V~V c-m +50kV;

[0033] The slope of the ramp scanning signal is higher than 10 V / ps.

[0034] Beneficial effects of the present invention:

[0035] 1. In the method for using the ultra-high time-resolution photoelectric detector provided by the present invention, when there is no light signal to be measured in the outside world, the voltage of the photocathode is higher than the voltage of the acceleration system, and the ultra-high time-resolution photoelectric detector is in a cut-off state; when the light signal to be measured triggers the gated acceleration pulse generator, a gated pulse acceleration voltage signal is generated and applied between the photocathode and the acceleration system through a pulse feed circuit. The photocathode voltage is a DC voltage superimposed on the gated pulse acceleration voltage signal, which can avoid high-voltage vacuum breakdown between the photocathode and the acceleration system, and the DC voltage of the photocathode is lower than the voltage of the acceleration system, so that the ultra-high time-resolution photoelectric detector can realize high-time-resolution diagnosis of ultrafast processes.

[0036] 2. In the present invention, the DC voltage of the photocathode is combined with the instantaneous gate pulse acceleration voltage signal, and the streak tube unit can obtain an acceleration voltage higher than 50kV / mm. At the same time, when an S20 photocathode with smaller time dispersion is used, the physical time dispersion of the streak tube unit can be reduced to below 20fs.

[0037] 3. In the present invention, the slit-type anode system can modulate the width and distribution of the photoelectron pulse along the scanning direction. Combined with the high scanning speed, the time dispersion of the streak tube unit can be reduced to below 30 fs.

[0038] 4. The use of a gated acceleration pulse generator can increase the energy of photoelectrons to at least 50 keV, which can significantly shorten the transit time of photoelectrons in the streak tube, increase the average speed of photoelectron pulses in the streak tube, and reduce the dynamic scanning time dispersion of the streak tube to below 10 fs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic structural diagram of an embodiment of a photodetector with ultra-high time resolution according to the present invention;

[0040] Figure 2 Schematic diagram of the structure of an electrostatic focusing streak tube photoelectric detector according to an embodiment of the present invention;

[0041] Figure 3 Schematic diagram of a sine waveform of a strobe pulse acceleration voltage signal in an embodiment of the present invention;

[0042] Figure 4 Schematic diagram of a sine waveform with a contracted top for a strobe pulse acceleration voltage signal in an embodiment of the present invention.

[0043] The attached marks are as follows:

[0044] 1-Photocathode, 2-Acceleration system, 3-Focusing system, 4-Anode system, 5-Scanning deflection system, 6-Fluorescent screen, 7-High and low voltage power supply system, 8-Gated acceleration pulse generator, 9-Scanning deflection signal generating circuit, 10-Pulse feeding circuit, 11-Trigger system, 12-Beam splitter. DETAILED DESCRIPTION

[0045] See also Figure 1 A photodetector with ultra-high time resolution includes a streak tube unit, a high and low voltage power supply system 7, a gate acceleration pulse generator 8, a scanning deflection signal generating circuit 9, a pulse feeding circuit 10, a trigger system 11 and a beam splitter 12; the streak tube unit is arranged in a vacuum chamber and includes a photocathode 1, an acceleration system 2, a focusing system 3, an anode system 4, a scanning deflection system 5 and a fluorescent screen 6 arranged in sequence along the electron transmission direction.

[0046] The photocathode 1 is a planar photocathode, employing an S20 visible light cathode in this embodiment. It is used to generate a photoelectron image that is completely consistent in time and space with the ultra-light pulse signal to be measured. The acceleration system 2 is a planar acceleration system, employing a planar slit-grid acceleration system in this embodiment, but a planar grid-type acceleration system could also be employed. It is used to provide a DC accelerating voltage to the photoelectrons in the photoelectron image generated by the photocathode 1. The outer radius of the acceleration system 2 is equal to that of the photocathode 1. The focusing system 3 is an electrostatic focusing system, a magnetic focusing system, or an anisotropic focusing system, used to focus the photoelectrons in time and space. The anode system 4 is a slit-type anode system, with a rectangular slit at its output end, along the direction of electron transmission, measuring 8 mm long by 10 μm wide. This slit is used to provide the accelerating voltage and correct the temporal distribution of the photoelectrons. The scanning deflection system 5 is a parallel plate deflector, a traveling wave deflector, or a flat plate deflector, used to provide a high-slope spatiotemporal scanning signal, converting temporal information into spatial information to obtain the electron image. The fluorescent screen 6 is used to convert the electronic image into an optical image.

[0047] The beam splitter 12 is used to receive the super-optical pulse signal to be measured and split it into a first super-optical pulse signal and a second super-optical pulse signal; the second super-optical pulse signal enters the trigger system 11, and the first super-optical pulse signal enters the photocathode 1; one output end of the trigger system 11 is connected to the gate acceleration pulse generator 8, and the other output end is connected to the scanning deflection signal generating circuit 9; the gate acceleration pulse generator 8 is used to generate a gate pulse acceleration voltage signal, see Figure 3 and Figure 4 The waveform of the gate pulse acceleration voltage signal is a sine wave or a truncated sine wave. The scanning deflection signal generating circuit 9 is used to generate a ramp scanning signal. The output of the gate acceleration pulse generator 8 is connected to a pulse feed circuit 10, and the output of the pulse feed circuit 10 is connected to another input of the photocathode 1. The output of the scanning deflection signal generating circuit 9 is connected to the scanning deflection system 5. The pulse feed circuit 10 can be a separate electronic component or circuit system.

[0048] The output ends of the high and low voltage power supply system 7 are respectively connected to the photocathode 1, acceleration system 2, focusing system 3, anode system 4, scanning deflection system 5 and fluorescent screen 6 in the streak tube unit. Specifically, the high and low voltage power supply system 7 is a push-pull power supply system or a resistive voltage divider power supply system, which can generate 5-8 high and low voltages.

[0049] The ultra-high time-resolution photodetector of the present invention has a time resolution better than 50 fs and a dynamic spatial resolution higher than 30 lp / mm within a cathode effective detection range of 6 mm×10 μm.

[0050] The method for using the ultra-high time-resolution photodetector comprises the following steps:

[0051] S1, start the high and low voltage power supply system 7, supply power to the photocathode 1, acceleration system 2, focusing system 3, anode system 4, scanning deflection system 5 and phosphor screen 6, and provide a stable DC voltage value for the photocathode 1, acceleration system 2, focusing system 3, anode system 4, scanning deflection system 5 and phosphor screen 6, and the voltage V c Higher than the acceleration system voltage V m ;

[0052] The DC voltage difference between the photocathode 1 and the acceleration system 2 is V c-m , and the streak tube unit is in the cut-off state;

[0053] S2, the beam splitter 12 receives the ultra-light pulse signal to be measured and splits it into a first ultra-light pulse signal and a second ultra-light pulse signal;

[0054] The first ultra-light pulse signal is directly transmitted to the photocathode 1;

[0055] The second ultra-light pulse signal is input to the trigger system 11, and the trigger system 11 triggers the gate acceleration pulse generator 8 to generate the gate pulse acceleration voltage signal V g (t), and triggers the scanning deflection signal generating circuit 9 to generate a ramp scanning signal; the gate pulse acceleration voltage signal V g The peak voltage of (t) is V c-m +10V~V c-m +50kV, the slope of the ramp sweep signal is higher than 10V / ps;

[0056] Strobe pulse acceleration voltage signal V g (t) The pulse is applied to the photocathode 1 through the pulse feeding circuit 10, forming the actual voltage value V of the photocathode 1 g (t)+V c , the actual voltage value V g (t)+V c Under the action of the first super optical pulse signal, the photocathode 1 generates a photoelectron image that is completely consistent with the super optical pulse signal to be measured in time and space according to the first super optical pulse signal; g Under the action of (t), the energy of the electrons emitted by the photocathode (1) increases rapidly to 20keV-50keV, which can reduce the physical time dispersion of the electrons near the photocathode on the one hand; on the other hand, it can shorten the transit time of the photoelectrons and reduce the time dispersion caused by the space charge effect; in addition, since the voltage value of the gate pulse acceleration voltage signal is much greater than the DC voltage V of the photocathode 1 c , which can greatly reduce the physical time dispersion near the photocathode 1 and avoid vacuum breakdown caused by DC high voltage.

[0057] S3, the strobe pulse acceleration voltage signal V g (t) under the action of the acceleration system 2, when the voltage V m ≥V g (t)+V c , the streak tube unit is in a gated acceleration state; the photoelectrons of the photoelectron image generated by the photocathode 1 move to the acceleration system 2, are then focused in time and space by the focusing system 3, and are accelerated and corrected in time by the anode system 4 before entering the scanning deflection system 5; the slit-type anode system can modulate the width and distribution of the photoelectrons of the photoelectron image along the scanning direction. Combined with the high scanning speed, the technical time dispersion of the streak tube can be reduced to below 30 fs; the gated acceleration pulse generator 8 can increase the energy of the photoelectrons to at least 50 keV, which can significantly shorten the transit time of the photoelectrons in the streak tube, increase the average speed of the photoelectron pulses in the streak tube, and reduce the dynamic scanning time dispersion of the streak tube to below 10 fs.

[0058] S4. The scanning deflection system 5 generates a ramp scanning signal according to the triggering of the scanning deflection signal generating circuit 9, and scans the photoelectron image at a scanning speed greater than 2c, where c is the speed of light, thereby converting the temporal information in the photoelectron image into spatial information and obtaining an electronic image.

[0059] S5. The scanning deflection system 5 outputs the photoelectron image to the fluorescent screen 6. The fluorescent screen 6 converts the electron image into an optical image to detect the ultra-light pulse signal to be measured.

[0060] The following is a detailed description of the electrostatic focusing streak tube ultrafast light detector as an example. Figure 2 As shown in the figure, the high voltage electrodes of each component of the streak tube are powered by resistor voltage division to ensure the normal operation of the streak tube. The voltage of the photocathode 1 is V c , the voltage of acceleration system 2 is V m , the voltages of the single lens electrostatic focusing system are V F1 , V F2 , V F3 , where V F1 =V F3 =0V; the voltage of the anode system 4 is V A , the pre-bias voltages of the scanning deflection system 5 are V P1 and V P2 When the optical pulse signal to be measured is radiated to the trigger system 11, the gate acceleration pulse generator 8 generates a gate pulse type acceleration voltage signal V g (t) and triggers the scanning deflection signal generating circuit 9 to generate a ramp scanning signal, V g (t) is input to the photocathode 1 through the pulse feeding circuit 10, and the original DC working voltage V cTogether they form a new operating voltage V g (t)+V c .

Claims

1. A photodetector with ultra-high time resolution, characterized by: It comprises a streak tube unit, a high and low voltage power supply system (7), a gate acceleration pulse generator (8), a scanning deflection signal generating circuit (9), a pulse feeding circuit (10), a trigger system (11) and a beam splitter (12); The streak tube unit is arranged in a vacuum chamber and comprises a photocathode (1), an acceleration system (2), a focusing system (3), an anode system (4), a scanning deflection system (5), and a fluorescent screen (6) arranged in sequence along the electron transmission direction; the photocathode (1) is used to generate a photoelectron image that is completely consistent in time and space with the ultra-light pulse signal to be measured; The acceleration system (2) is used to provide a DC acceleration voltage for the photoelectrons in the photoelectron image generated by the photocathode (1); the focusing system (3) is used to focus the photoelectrons in time and space directions; The anode system (4) is used to correct the distribution of photoelectrons in the photoelectron image in the time direction and provide an accelerating voltage; the scanning deflection system (5) is used to provide a high-slope spatiotemporal scanning signal to convert the time information of the photoelectron image into spatial information; the fluorescent screen (6) is used to convert the photoelectron image into an optical image; The beam splitter (12) is used to receive the super-optical pulse signal to be measured and split it into a first super-optical pulse signal and a second super-optical pulse signal; the second super-optical pulse signal enters the trigger system (11), and the first super-optical pulse signal enters the photocathode (1); one output end of the trigger system (11) is connected to the gate acceleration pulse generator (8), and the other output end is connected to the scanning deflection signal generating circuit (9); the gate acceleration pulse generator (8) is used to generate a gate pulse acceleration voltage signal, and the scanning deflection signal generating circuit (9) is used to generate a ramp scanning signal; the output end of the gate acceleration pulse generator (8) is connected to the pulse feeding circuit (10), and the output end of the pulse feeding circuit (10) is connected to the input end of the photocathode (1); the output end of the scanning deflection signal generating circuit (9) is connected to the scanning deflection system (5); The output ends of the high and low voltage power supply systems (7) are respectively connected to the photocathode (1), the acceleration system (2), the focusing system (3), the anode system (4), the scanning deflection system (5) and the fluorescent screen (6) in the streak tube unit.

2. The ultra-high time-resolution photodetector according to claim 1, characterized in that: The waveform of the gate pulse acceleration voltage signal generated by the gate acceleration pulse generator (8) is a sine wave.

3. The ultra-high time-resolution photodetector according to claim 2, characterized in that: The photocathode (1) is a planar photocathode; The acceleration system (2) is a planar acceleration system.

4. The ultra-high time-resolution photodetector according to claim 3, characterized in that: The photocathode (1) is an S20 visible light cathode; The acceleration system (2) is a slit-type acceleration system.

5. The ultra-high time-resolution photodetector according to claim 4, characterized in that: The focusing system (3) is an electrostatic focusing system, a magnetic focusing system or an anisotropic focusing system.

6. The ultra-high time-resolution photodetector according to claim 5, characterized in that: The output end of the anode system (4) has a slit, and the width of the slit is 10 μm to 100 μm.

7. The ultra-high time-resolution photodetector according to claim 6, characterized in that: The scanning deflection system (5) is a parallel plate deflector, a traveling wave deflector or a flat folding plate deflector.

8. The ultra-high time-resolution photodetector according to claim 7, characterized in that: The high and low voltage power supply system (7) is a push-pull power supply system or a resistance voltage division power supply system.

9. A method for using the ultra-high time-resolution photodetector according to claim 1, characterized in that: The following steps are involved: S1, start the high and low voltage power supply system (7), supply power to the photocathode (1), the acceleration system (2), the focusing system (3), the anode system (4), the scanning deflection system (5) and the fluorescent screen (6), and provide a stable DC voltage to the photocathode (1), the acceleration system (2), the focusing system (3), the anode system (4), the scanning deflection system (5) and the fluorescent screen (6), and the voltage V c Higher than the acceleration system voltage V m ; The voltage difference between the photocathode (1) and the acceleration system (2) is V c-m , and the streak tube unit is in the cut-off state; S2, a beam splitter (12) receives the super-optical pulse signal to be measured and splits it into a first super-optical pulse signal and a second super-optical pulse signal; The first ultra-light pulse signal is directly transmitted to the photocathode (1); The second super-light pulse signal is input into the trigger system (11), and the trigger system (11) triggers the gate acceleration pulse generator (8) to generate a gate pulse acceleration voltage signal V g (t), and triggering the scanning deflection signal generating circuit (9) to generate a ramp scanning signal; Strobe pulse acceleration voltage signal V g (t) is applied to the photocathode (1) through the pulse feeding circuit (10), forming the actual voltage value V of the photocathode (1) g (t)+V c , the actual voltage value V g (t)+V c Under the action of the first beam of ultra-light pulse signal to be measured, the photocathode (1) generates a photoelectron image that is completely consistent with the ultra-light pulse signal to be measured in time and space; S3, the strobe pulse acceleration voltage signal V g (t), when the voltage V of the acceleration system (2) m ≥V g (t)+V c , the streak tube unit is in the gated acceleration state; The photoelectrons of the photoelectron image generated by the photocathode (1) move to the acceleration system (2), are focused in time and space by the focusing system (3), are accelerated and corrected in time by the anode system (4), and then enter the scanning deflection system (5); S4, the scanning deflection system (5) generates a ramp scanning signal according to the triggering scanning deflection signal generating circuit (9), scans the photoelectron image at a scanning speed greater than 2c, where c is the speed of light, and converts the time information in the photoelectron image into spatial information; S5. The scanning deflection system (5) transmits the photoelectron image to the fluorescent screen (6). The fluorescent screen (6) converts the electronic image into an optical image to realize the detection of the ultra-light pulse signal to be measured.

10. The method for using the ultra-high time-resolution photodetector according to claim 9, characterized in that: In step S3, the strobe pulse acceleration voltage signal V g The peak voltage of (t) is V c-m +10V~V c-m +50kV; The slope of the ramp scanning signal is higher than 10 V / ps.

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