WO2022077875A1 - Electron beam oscilloscope having improved temporal resolution, and measurement system thereof - Google Patents

Abstract

An electron beam oscilloscope having improved temporal resolution, and a measurement system thereof. The oscilloscope has a high-voltage pulse generator (105) having a positive output end connected to a microstrip cathode (101). A negative output end of the high-voltage pulse generator (105) is connected to an MCP image intensifier tube (104). An anode mesh (102) is grounded. The microstrip cathode (101), the anode mesh (102), the MCP image intensifier tube (104), and a CCD are sequentially arranged, and the microstrip cathode (101), the anode mesh (102), the MCP image intensifier tube (104), and the CCD are coaxially arranged. A magnetic focusing lens (103) is located between the anode mesh (102) and the MCP image intensifier tube (104). The CCD is used to display a measurement light spot image, and analyzes and processes the measurement light spot image to obtain a detection waveform. The electron beam oscilloscope having improved temporal resolution uses a pulse voltage to cause electron energy dispersion, and the energy dispersion improves the temporal resolution of electron beams. The magnetic focusing lens (103) is utilized to generate a Gauss magnetic field, and the magnetic field forms images of the photoelectrons on the microstrip cathode (101) at the MCP image intensifier tube (104), thereby improving the imaging quality of the oscilloscope while enabling the measurement of electrical pulse waveforms.

Description

An electron beam time amplification oscilloscope and its measurement system technical field

The invention relates to the field of oscilloscopes, and more particularly, to an electron beam time amplification oscilloscope and a measurement system thereof.

Background technique

Inertial confinement fusion (ICF) has an extremely short duration of only 1-2 ns, and requires ultrafast diagnostic techniques to measure plasma temperature, density, and their time-dependent changes. The microchannel plate (MCP) gated X-ray framing camera is an ultrafast diagnostic device with two-dimensional spatial resolution and one-dimensional time resolution. With the deepening of ICF research, it is required to use a framing camera with a time resolution better than 30ps to measure the spatiotemporal evolution of plasma. However, the time resolution of the current practical framing camera is generally 60-100ps, which cannot meet the above-mentioned experimental measurement requirements.

In recent years, a new type of framing camera has been developed at home and abroad that uses magnetic focusing imaging electron beam time magnification. For example, the Lawrence Livermore National Laboratory (LLNL) in the United States proposed to use electron beam time magnification technology to improve the time resolution, and successfully obtained an X-ray framing camera with a time resolution of 5ps. The framing camera first uses the electron pulse time amplification technology to expand the time width of the electron beam cluster, and then uses the traditional MCP image tube to measure the time-amplified electron beam cluster, so as to obtain high time resolution. At the same time, after research, it is found that the framing camera can be used as an oscilloscope to measure the waveform of electrical pulses.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide an electron beam time amplification oscilloscope and a measurement system thereof, aiming at the existing electron beam time amplification technology and applying it to the field of oscilloscope.

The technical solution adopted by the present invention to solve the technical problem is: constructing an electron beam time amplification oscilloscope, which includes a microstrip cathode, an anode grid, a magnetic focusing lens, an MCP image tube, a CCD and a high-voltage pulse generator. The positive output terminal of the pulse generator is connected to the microstrip cathode, the negative output terminal of the high-voltage pulse generator is connected to the MCP video tube, and the anode grid is grounded; the microstrip cathode and the anode grid are connected to the ground. , the MCP image tube and the CCD are arranged in sequence, and the microstrip cathode, the anode grid, the MCP image tube and the CCD are placed coaxially; the magnetic focusing lens is located at the anode between the grid and the MCP image tube;

The microstrip cathode generates photoelectrons under the irradiation of incident light, a negative DC bias voltage is applied to the microstrip cathode and a high voltage ramp pulse is superimposed, and the optical pulse is synchronized on the rising edge of the high voltage ramp pulse; the generated photoelectrons pass through the anode After the grid, it enters the drift region between the anode grid and the MCP image tube, and the electron beam formed by the expansion of the photoelectrons under the action of the magnetic field of the magnetic focusing lens is imaged on the MCP image tube. The CCD records the visible light output by the MCP image changing tube, and then obtains the detection waveform by analyzing and processing the light spot image.

Further, in the electron beam time amplification oscilloscope of the present invention, the microstrip cathode includes a quartz glass plate and three gold cathode microstrip lines evaporated on the quartz glass plate, each of the gold cathode microstrips The thickness of the line is 80 nm and the width is 8 mm; the three gold cathode microstrip lines are arranged in parallel, and the interval between the adjacent gold cathode microstrip lines is 2.8 mm.

Further, in the electron beam time magnification oscilloscope of the present invention, the magnetic focusing lens includes soft iron and 1200 turns of copper coil, the outer diameter of the magnetic focusing lens is 256mm, and the inner diameter of the magnetic focusing lens is 160mm, The length of the magnetic focusing lens in the axial direction is 100 mm; the inner side of the circular ring of the magnetic focusing lens has a circle with a width of 4 mm.

Further, in the electron beam time-amplifying oscilloscope of the present invention, the MCP picture tube includes an impedance gradient line, a microchannel plate, three microstrip lines evaporated on the microchannel plate, and a phosphor screen fabricated on the fiber optic panel. , the microstrip line faces the anode grid side, the fluorescent screen is located between the microchannel plate and the CCD; the negative output end of the high voltage pulse generator is connected to the microstrip through the impedance gradient line with line;

The outer diameter of the microchannel plate is 56mm, the thickness is 0.5mm, the channel diameter is 12μm, and the chamfer angle is 6°; the width of the microstrip line is 8mm, and the three microstrip lines are arranged in parallel and adjacent to each other. The interval between the two microstrip lines is 2.8mm; the microchannel plate and the phosphor screen are placed in parallel, and the distance between the microchannel plate and the phosphor screen is 0.5mm.

Further, in the electron beam time amplification oscilloscope of the present invention, the high-voltage pulse generator includes an avalanche triode circuit and a diode pulse circuit, and the high-voltage ramp pulse generated by the avalanche triode circuit is divided into two parts, and one part passes through the impedance gradient line. Input to the microstrip cathode, and the other part is used to drive the diode pulse circuit to generate the MCP strobe.

Further, in the electron beam time amplification oscilloscope of the present invention, the microstrip cathode is connected to a first attenuator, and the first attenuator absorbs the high-voltage ramp pulse after passing through the microstrip cathode; the MCP becomes The microstrip line of the tube is connected to a second attenuator, and the second attenuator absorbs the MCP strobe pulse after passing through the microstrip line;

Further, in the electron beam time amplification oscilloscope of the present invention, the microstrip cathode generates photoelectrons after receiving incident light, and the photoelectrons fly to the MCP image tube under the confinement of the magnetic field of the magnetic focusing lens; The moment when the photoelectron with time t _i reaches the MCP picture tube is:

Wherein, L is the length of the drift region, e is the photoelectron charge, e=1.6×10 ^-19 C; m is the photoelectron mass, m=9.1×10 ^-31 kg;

is the voltage difference between the microstrip cathode and the anode grid, _VB is the cathode bias voltage, and _VP (t) is the voltage value of the cathode pulse synchronized with the light pulse at time t;

The electron beam time magnification M can be expressed as:

Then the technical time resolution of the electron beam time amplification oscilloscope is:

Wherein, T _MCP is the time resolution of the MCP imaging tube;

The time resolution of the electron beam time amplification oscilloscope is:

T _phys is the physical time resolution, which depends on the electron transit time dispersion between the microstrip cathode and the anode grid:

E=[-V _B -V _P (t)]/L _pa (6)

The unit of T _phys is ps, where δε is the initial energy distribution of photoelectrons, and the unit is eV. Under the irradiation of ultraviolet laser with a wavelength of 260 nm, the initial energy distribution of photoelectrons generated by the microstrip cathode is 0.5 eV; E is the The electric field strength between the microstrip cathode and the anode grid, in kV/mm; _Lpa is the distance between the microstrip cathode and the anode grid.

In addition, the present invention also provides an electron beam time amplification oscilloscope measurement system, including the above electron beam time amplification oscilloscope, the system further includes a laser light source, a photodetector, a delay circuit, an optical fiber bundle and a collimator, so The optical fiber bundle includes a plurality of optical fibers, and the lengths of the plurality of optical fibers are distributed in an arithmetic progression;

The laser light source includes a first output end for outputting laser light of a first wavelength and a second output end for outputting laser light of a second wavelength, and the laser light emitted by the first output end enters the parallel light through the fiber bundle After being transmitted by the parallel light tube, it is incident on the microstrip cathode of the electron beam time amplification oscilloscope; the laser light emitted by the second output end is input to the photodetector, and the generated electrical signal is passed through the delay circuit Input the input terminal of the high voltage pulse generator of the electron beam time amplification oscilloscope after the delay.

Further, in the electron beam time amplification oscilloscope measurement system of the present invention, the optical fiber bundle includes 30 multimode optical fibers, and the 30 multimode optical fibers are arranged in a rectangle adjacent to each other, and the rectangle includes 3 rows of multimode optical fibers, and each row There are 10 multimode fibers; the lengths of 30 multimode fibers increase in arithmetic progression according to the arrangement order, and the tolerance of arithmetic progression is 2mm.

Further, in the electron beam time amplification oscilloscope measurement system of the present invention, the first wavelength laser is a 266 nm laser, and the second wavelength laser is an 800 nm laser.

An electron beam time magnifying oscilloscope and its measurement system implemented in the present invention have the following beneficial effects: the electron beam time magnifying oscilloscope of the present invention uses pulse voltage to generate electron energy dispersion, the energy dispersion obtains electron beam time magnification, and uses a magnetic focusing lens to generate Gaussian-shaped magnetic field, the magnetic field images the photoelectrons on the microstrip cathode on the microchannel plate, which improves the imaging quality of the oscilloscope, and can measure the electrical pulse waveform at the same time.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

1 is a schematic structural diagram of an electron beam time amplification oscilloscope provided by an embodiment;

2 is a schematic structural diagram of a high-voltage pulse generator provided by an embodiment;

3 is a schematic structural diagram of an electron beam time amplification oscilloscope measurement system provided by an embodiment;

4 is a schematic structural diagram of an optical fiber bundle provided by an embodiment;

Figure 5(a) is a dynamic image when only a DC voltage is applied to the microstrip cathode provided by an embodiment;

Figure 5(b) is a static image of a 10ps interval optical fiber provided by an embodiment;

Fig. 6 is the time resolution T _MCP measurement result of the MCP image tube when the microstrip cathode provided by one embodiment is not pulsed;

FIG. 7 is a schematic diagram of synchronizing the optical pulses sequentially with the ramps of the microstrip cathode pulses at different points according to an embodiment;

8 is a dynamic image at t 1 , t 2 , t 3 . . . t ₁₁ , t ₁₂ when the light pulse is synchronized with the cathode pulses t ₁ , t ₂ , t ₃ . . . , provided by an embodiment;

9 is a measurement result of the time resolution T(t ₁ ) of the time amplification oscilloscope when the optical pulse is synchronized at the cathode pulse t ₁ point according to an embodiment;

10 is a relationship between the time resolution corresponding to each point of the microstrip cathode pulse ramp and the ramp synchronization position provided by an embodiment;

11 is a measurement result of a microstrip cathode pulse waveform provided by an embodiment;

FIG. 12 shows the relationship between the limit time resolution, the theoretical value of the maximum bandwidth and the voltage between cathode and gate provided by an embodiment.

Detailed ways

In order to have a clearer understanding of the technical features, objects and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Example 1

Referring to FIG. 1 , the electron beam time amplification oscilloscope of the present embodiment includes a microstrip cathode 101 , an anode grid 102 , a magnetic focusing lens 103 , an MCP picture tube 104 , a CCD and a high-voltage pulse generator 105 , and the positive electrode of the high-voltage pulse generator 105 The output terminal is connected to the microstrip cathode 101, the negative output terminal of the high-voltage pulse generator 105 is connected to the MCP imaging tube 104, and the anode grid 102 is grounded; the microstrip cathode 101, the anode grid 102, the MCP imaging tube 104 and the CCD are arranged in sequence, And the microstrip cathode 101 , the anode grid 102 , the MCP picture tube 104 and the CCD are placed coaxially; the magnetic focusing lens 103 is located between the anode grid 102 and the MCP picture tube 104 .

The microstrip cathode 101 generates photoelectrons under the irradiation of incident light, and a negative DC bias voltage is applied to the microstrip cathode 101 and a high voltage ramp pulse is superimposed. Gain more energy, thereby making the electrons in front faster. The generated photoelectrons pass through the anode grid 102 and then enter the drift region between the anode grid 102 and the MCP image tube 104, and the electron beam formed by the photoelectrons expanded under the action of the magnetic field of the magnetic focusing lens 103 is imaged on the MCP image tube 104, and the CCD The visible light output by the MCP picture tube 104 is recorded. That is, the time width of the electron beam is widened to realize the time amplification of the electron beam. Due to the large transmission distance of the drift region, the electron beam will diverge in space. In order to improve the spatial resolution, a magnetic focusing lens 103 is used to image the broadened electron beam on a microstrip line corresponding to the input surface of the MCP image tube 104 . When the strobe pulse is transmitted on the MCP along the microstrip line 1043, the electron beam is gated and enhanced by the MCP, and hits the phosphor screen 1044 to form a visible light image, and the output visible light image is recorded and processed by a CCD. Since the electron beam is temporally broadened, a very high system temporal resolution can be obtained by using a lower temporal resolution MCP picture tube.

Alternatively, the microstrip cathode 101 in the electron beam time amplification oscilloscope of this embodiment includes a quartz glass plate and three gold cathode microstrip lines evaporated on the quartz glass plate, and the positive output end of the high-voltage pulse generator 105 passes through the impedance gradient line 1041 are respectively connected to three gold cathode microstrip lines. The thickness of each gold cathode microstrip line is 80nm and the width is 8mm; three gold cathode microstrip lines are arranged in parallel, and the interval between adjacent gold cathode microstrip lines is 2.8mm. The microstrip cathode has two functions: one is the function of photocathode, which converts incident light into photoelectrons; the other is the function of microstrip line, which transmits high-voltage ramp pulses, so that there is a gap between the microstrip cathode 101 and the anode grid 102. The time-varying electric field realizes the time amplification of the electron beam.

Alternatively, in the electron beam time magnification oscilloscope of this embodiment, the magnetic focusing lens 103 includes soft iron and 1200 turns of copper coils, the outer diameter of the magnetic focusing lens 103 is 256 mm, the inner diameter of the magnetic focusing lens 103 is 160 mm, and the magnetic focusing lens The axial length of 103 is 100mm; the inner side of the ring of the magnetic focusing lens 103 has a circle with a width of 4mm, and the magnetic field enters the drift region through the 4mm slit. The magnetic focusing lens 103 images the photoelectrons on the cathode surface of the microstrip on the input surface of the MCP, and the imaging magnification is 1:1.

Alternatively, the MCP image tube 104 in the electron beam time amplification oscilloscope of this embodiment includes an impedance gradient line 1041, a microchannel plate 1042, three microstrip lines 1043 evaporated on the microchannel plate 1042, and a The fluorescent screen 1044, the microstrip line 1043 faces the anode grid 102 side, and the fluorescent screen 1044 is located between the microchannel plate 1042 and the CCD; The outer diameter of the microchannel plate 1042 is 56mm, the thickness is 0.5mm, the channel diameter is 12μm, and the chamfer angle is 6°; the width of the microstrip line 1043 is 8mm, and the three microstrip lines 1043 are arranged in parallel, and two adjacent microstrip lines 1043 are arranged in parallel. The interval between the strip lines 1043 is 2.8 mm; the microchannel plate 1042 and the phosphor screen 1044 are placed in parallel, and the distance between the microchannel plate 1042 and the phosphor screen 1044 is 0.5 mm.

Alternatively, in the electron beam time amplification oscilloscope of this embodiment, the microstrip cathode 101 is connected to the first attenuator 1061, and the first attenuator 1061 absorbs the high-voltage ramp pulse after passing through the microstrip cathode 101; The strip line 1043 is connected to the second attenuator 1062 , and the second attenuator 1062 absorbs the MCP gate pulse after passing through the microstrip line 1043 .

Referring to FIG. 2 , the high-voltage pulse generator 105 in the electron beam time-amplified oscilloscope of the present embodiment includes an avalanche triode circuit 1051 and a diode pulse circuit 1052 . Input to the microstrip cathode 101, the other part is used to drive the diode pulse circuit 1052 to generate the MCP strobe.

The oscillometric principle of the electron beam time amplification oscilloscope:

The time resolution of the electron beam time amplification oscilloscope in this embodiment mainly depends on the following four aspects: cathode bias voltage, cathode pulse slope, drift region length and time resolution of the MCP picture tube. The microstrip cathode 101 generates photoelectrons after receiving the incident light, and the photoelectrons are imaged to the MCP picture tube 104 under the action of the magnetic field of the magnetic focusing lens 103 . Ignoring the distance of 1.8 mm between the cathode grids and the photoelectron emission energy distribution, the photoelectron emission time t _i arrives at the MCP image tube 104 at the moment:

Among them, L is the length of the drift region, e is the photoelectron charge, e=1.6×10 ^-19 C; m is the photoelectron mass, m=9.1×10 ^-31 kg;

is the voltage difference between the microstrip cathode 101 and the anode grid 102, _VB is the cathode bias voltage, and _VP (t) is the voltage value of the cathode pulse synchronized with the optical pulse at time t;

The electron beam time magnification M can be expressed as:

Then the technical time resolution of the electron beam time amplification oscilloscope is:

Wherein, T _MCP is the time resolution of the MCP imaging tube 104;

The time resolution of the electron beam time amplification oscilloscope is:

T _phys is the physical time resolution, which depends on the electron transit time dispersion between the microstrip cathode 101 and the anode grid 102:

E=[-V _B -V _P (t)]/L _pa (6)

The unit of T _phys is ps, where δε is the initial energy distribution of photoelectrons, and the unit is eV. Under the irradiation of ultraviolet laser with a wavelength of 260 nm, the initial energy distribution of photoelectrons generated by the microstrip cathode 101 is 0.5 eV; E is the microstrip cathode. The electric field strength between 101 and the anode grid 102 is in kV/mm; L _pa is the distance between the microstrip cathode 101 and the anode grid 102 .

First, the time resolution T _MCP of the MCP camera tube 104 is experimentally measured.

Next, change the time when the cathode pulse reaches the microstrip cathode 101, so that the photoelectrons are synchronized at different slope positions of the cathode pulse, that is, change the cathode pulse voltage value _VP (t) acting on the photoelectrons when the optical pulse is synchronized with the cathode pulse.

The optoelectronic synchronization sequentially increases Δt at the ramp position of the cathode pulse. Each synchronization is at a certain position of the cathode pulse slope, and the time resolution T of the electron beam time amplification oscilloscope at this time is measured, and the T of different synchronization positions t ₁ , t ₂ , t ₃ . . . can be obtained in turn. In the above formula (2), L, e, m are constants,

V _B is the set cathode bias voltage, which is a known quantity. The unknown quantities in the above formula (2) are _VP (t) and _VP '(t), and _VP (t) and _VP '(t) have the following relationship:

_T in the above formula (4) can be measured experimentally, then the unknowns in formulas (2)-(6) are only VP (t) and _VP '(t). The relationship between _VP (t) and _VP '(t) can be given by equation (7), so _VP (t) can be obtained from equations (4) and (7). _VP (t) is the difference between time t and The voltage value of the cathode pulse synchronized by the optical pulse, that is, the voltage value of the cathode pulse at different times can be obtained by using the electron beam time amplification oscilloscope, thereby obtaining the cathode pulse waveform and realizing the oscilloscope function of the oscilloscope.

To sum up, the difference between the electron beam time magnifying oscilloscope of this embodiment and the American time stretching framing camera is that the United States uses a solenoid long magnetic focusing lens to generate a uniform magnetic field, and the magnetic field converts the photoelectrons on the microstrip cathode into a reduced image. MCP, the imaging magnification is 3:1, and the spatial resolution of the acquired camera is 510 μm. In this embodiment, a large-diameter short magnetic focusing lens is used to generate an axisymmetric non-uniform magnetic field with Gaussian distribution, and the magnetic field converts the photoelectrons on the microstrip cathode into an equal-sized image on the MCP, and the imaging magnification is 1:1. Short magnetic focusing lenses are often used in electron microscopes or streak cameras to improve the imaging quality of the system. The second difference is that the American camera uses four magnetic coils with a diameter of 40 cm, each of which is 8 cm long in the axial direction, and the distance between two adjacent magnetic coils is 15 cm; the oscilloscope in this embodiment uses a A short magnetic focusing lens with a direction length of 10 cm. In terms of volume and weight, the oscilloscope of this embodiment is smaller than the American camera, so it is more convenient to send it into the ICF target chamber to diagnose the plasma. There are also differences in the measurement method of time resolution. In the United States, the time resolution of the camera is obtained from six dynamic images. Due to the trigger shaking in the experiment, there is a measurement error in this method. In this embodiment, the fiber bundle method is used, and one measurement can be Obtain the time resolution of the oscilloscope and avoid measurement errors caused by trigger shake.

Example 2

Referring to FIG. 1 and FIG. 3 , the electron beam time magnification oscilloscope measurement system of this embodiment includes an electron beam time magnification oscilloscope, and the electron beam time magnification oscilloscope includes a microstrip cathode 101, an anode grid 102, a magnetic focusing lens 103, and an MCP image. Tube 104, CCD and high voltage pulse generator 105, the positive output end of the high voltage pulse generator 105 is connected to the microstrip cathode 101, the negative output end of the high voltage pulse generator 105 is connected to the MCP image tube 104, and the anode grid 102 is grounded; The cathode 101, the anode grid 102, the MCP image tube 104 and the CCD are arranged in sequence, and the microstrip cathode 101, the anode grid 102, the MCP image tube 104 and the CCD are placed coaxially; the magnetic focusing lens 103 is located between the anode grid 102 and the CCD. Between the MCP image tubes 104 .

The microstrip cathode 101 generates photoelectrons under the irradiation of incident light, and a negative DC bias voltage is applied to the microstrip cathode 101 and a high voltage ramp pulse is superimposed. Gain more energy, thereby making the electrons in front faster. The generated photoelectrons pass through the anode grid 102 and then enter the drift region between the anode grid 102 and the MCP image tube 104, and the electron beam formed by the photoelectrons expanded under the action of the magnetic field of the magnetic focusing lens 103 is imaged on the MCP image tube 104, and the CCD The visible light output by the MCP picture tube 104 is recorded. That is, the time width of the electron beam is widened to realize the time amplification of the electron beam. Due to the large transmission distance of the drift region, the electron beam will diverge in space. In order to improve the spatial resolution, a magnetic focusing lens 103 is used to image the broadened electron beam on a microstrip line corresponding to the input surface of the MCP image tube 104 . When the strobe pulse is transmitted on the MCP along the microstrip line 1043, the electron beam is gated and enhanced by the MCP, and hits the phosphor screen 1044 to form a visible light image, and the output visible light image is recorded and processed by a CCD. Since the electron beam is temporally broadened, by using a lower temporal resolution MCP picture tube 104, a very high oscilloscope temporal resolution can be obtained.

Further, the electron beam time amplification oscilloscope measurement system also includes a laser light source 201, a photodetector 202, a delay circuit 203, an optical fiber bundle 204 and a collimator light pipe 205. The optical fiber bundle 204 includes a plurality of optical fibers, and the lengths of the plurality of optical fibers are equal to each other. Difference series distribution. Collimator 205 includes lens L ₁ and lens L ₂ . The laser light source 201 includes a first output end for outputting the first wavelength laser light and a second output end for outputting the second wavelength laser light. The laser light emitted by the first output end enters the collimator light pipe 205 through the fiber bundle 204, After transmission, the tube 205 is incident on the microstrip cathode 101 of the electron beam time amplification oscilloscope; the laser light emitted by the second output end is input to the photodetector 202, and the generated electrical signal is delayed by the delay circuit 203 and then input to the high voltage of the electron beam time amplification oscilloscope. The input of the pulse generator 105. Alternatively, the first output end adjusts the optical path through the mirror M2, so that the first wavelength laser light can smoothly enter the input end of the fiber bundle 204, and the second output end adjusts the optical path through the reflector M1, so that the second wavelength laser light can smoothly enter the photodetector the input of the device 202.

Referring to FIG. 4 , the fiber bundle 204 in the electron beam time amplification oscilloscope measurement system of the present embodiment includes 30 multimode fibers, and the 30 multimode fibers are arranged in a rectangular shape, and the rectangle contains 3 rows of multimode fibers, and each row has more than 10 multimode fibers. Mode fiber; the length of 30 multimode fibers increases in arithmetic progression according to the arrangement order, and the tolerance of arithmetic progression is 2mm. The numbers of the 30 multimode fibers in Figure 4 are 1, 2... The transmission time is increased by 10ps, so that the arrival times of these 30 light spots increase uniformly.

Alternatively, in the electron beam time amplification oscilloscope measurement system of this embodiment, the first wavelength laser is a 266 nm laser, and the second wavelength laser is an 800 nm laser.

The electron beam time magnification oscilloscope measurement system of this embodiment is used to detect the parameters of the electron beam time magnification oscilloscope. The electron beam time magnification oscilloscope uses a magnetic focusing lens to generate a Gaussian magnetic field, and the magnetic field images the photoelectrons on the microstrip cathode on the microchannel plate. Improve the imaging quality of the oscilloscope, while being able to measure the electrical pulse waveform.

Example 3

On the basis of Example 2, in the experiment, DC voltage was first applied to the microstrip cathode 101 and the MCP image tube 104 to measure the static image of the optical fiber, and then the static distribution of the incident light was obtained. The light pulse with a wavelength of 266 nm and a width of 130 fs outputted by the first output end of the laser light source 201 uniformly illuminates the input surface of the optical fiber beam transmission after being delayed, and the ultraviolet light is transmitted through the optical fiber bundle 204 to form 30 adjacent time intervals of 10 ps. The light spots are imaged on the microstrip line 1043 of the MCP picture tube 104 after passing through the collimator 205 . The second output end of the laser light source 201 outputs a light pulse with a wavelength of 800 nm and sends it to the photodetector 202 to generate a trigger pulse for triggering the high-voltage pulse generator. When measuring the time resolution T _MCP of the MCP camcorder tube 104, only DC voltage is applied to the microstrip cathode 101, the MCP camcorder tube 104 is loaded with a strobe pulse, and the optical pulse and the MCP strobe pulse are synchronized to obtain a time amplification without electron beams dynamic images. The dynamic image is normalized, and the normalized dynamic image light intensity spatial distribution is converted into a time distribution according to the time delay difference of the light spots in the optical fiber bundle 204, and Gaussian fitting is performed on it, and the fitting curve FWHM is T _MCP . When measuring the time resolution T of the electron beam time amplification oscilloscope, the microstrip cathode 101 and the MCP picture tube 104 are both loaded with pulse voltage, and the optical pulse, cathode pulse and MCP strobe pulse are synchronized to obtain a dynamic image after the electron beam time is broadened , normalize the dynamic image, convert the normalized dynamic image light intensity spatial distribution into time distribution, and perform Gaussian fitting on it, and the fitting curve FWHM is T.

Measurement result:

(1) The time resolution T _MCP experimental measurement results of the MCP variable image tube

The microstrip cathode 101 only applies -3kV DC voltage, and the MCP is loaded with -300V DC bias voltage and a gate pulse with an amplitude of -1.8kV and a width of 225ps, and the delay of the delay circuit is adjusted to make the electronic pulse and the gate pulse reach the MCP. The time synchronization of the microstrip line 1043 of the tube 104 produces a dynamic image, as shown in FIG. 5(a). After normalizing the dynamic image and the static image (5(b)), the normalized dynamic image light intensity spatial distribution is converted into a time distribution, the result is shown in Figure 6, the FWHM of the Gaussian fitting curve in the figure is 78ps, which is the time resolution of the oscilloscope without electron beam time amplification, that is, the time resolution T _MCP of the MCP picture tube.

(2) The experimental measurement results of the time resolution T of the electron beam time amplification oscilloscope

Synchronize the light pulse at _t1 point about 200ps after the start of the cathode pulse (as shown in Figure 7), load the pulse voltage on both the microstrip cathode 101 and the MCP picture tube 104, and synchronize the light pulse, cathode pulse and MCP strobe pulse , a dynamic image of the time-stretched electron beam is obtained, as shown in Fig. 8(a). After normalizing the dynamic image 8(a) and the static image (Fig. 5(b)), the normalized dynamic image light intensity spatial distribution is converted into a temporal distribution. The result is shown in Fig. 9, in which the Gaussian The FWHM of the fitted curve is 39ps, which is the time resolution of the electron beam time amplification oscilloscope corresponding to the cathode pulse ramp _t1 .

Adjusting the circuit delay, the optical pulses are synchronized sequentially at t ₂ at about 262.5ps, t ₃ at 325ps... t ₁₁ at 825ps after the start of the cathode pulse ramp, and the time interval between each adjacent two points Δt=62.5ps , the dynamic images corresponding to the cathode pulse slopes t ₂ , t ₃ ...... t ₁₁ points are obtained as shown in Fig. 8(b)-(k), respectively. When the optical pulse is synchronized at t ₁₂ about 1200 ps after the onset of the cathode pulse, the dynamic image is shown in Fig. 8(l). From the above dynamic images, the time resolution of the electron beam time amplification oscilloscope corresponding to the cathode pulse slopes t ₂ , t ₃ . . . t ₁₂ can be obtained. The relationship between the time resolution corresponding to each point of the cathode pulse ramp and the ramp synchronization position is shown in Figure 10.

During the experiment, set the cathode bias voltage _VB to be -3kV. In this embodiment, a short magnetic focusing lens is used to image the electron beam, and a certain magnetic lens current can only make the photoelectrons with a certain energy clearly image on the MCP. The voltage value VP (t ₁ ) of the cathode pulse synchronized with the optical pulse is 120V at point t ₁ about 200 _ps after the onset of the cathode pulse is obtained from the magnetic lens current. Then it can be obtained from formulas (2)-(6), V _P '(t ₁ )=0.37V/ps.

From VP (t ₁ ), _T (t2), T _MCP , equations (4) and (7), VP (t ₂ ) and _VP ′(t ₂ ) are 199 V and 1.26 V/ _ps , respectively . From this, the _VP (t) and _VP '(t) of each ramp position of the cathode pulse can be obtained in turn, as shown in Table 1.

Table 1 _VP (t) and _VP '(t) of each ramp synchronization position of cathode pulse

It can be seen from Table 1 that the electron beam time amplification oscilloscope is used to measure, and the waveform of the obtained cathode pulse from point t1 to point t12 is shown as "x" in Figure 11. The cathode pulse waveform obtained by high-speed oscilloscope measurement is shown in the "△" part of Figure 11. It can be seen from Fig. 11 that the cathode pulse waveforms obtained by the measurement of the two devices are almost identical between the points t1 and t12, and the difference between the two is within 6%.

The limit time resolution of the electron beam time amplification oscilloscope depends on the physical time resolution T _phys . When the distance between the microstrip cathode 101 and the anode grid 102 is 1.8mm, the limit time resolution of the oscilloscope is related to the voltage of the microstrip cathode 101 and the anode grid 102 The relationship between (voltage between cathode and grid) is shown in the red curve in Figure 12. The higher the voltage between the microstrip cathode 101 and the anode grid 102, the smaller the electron transit time dispersion and the higher the limit time resolution. The relationship between the maximum theoretical bandwidth of the electron beam time amplification oscilloscope and the voltage between the microstrip cathode 101 and the anode grid 102 is shown in the curve in Figure 12. The greater the voltage between the cathode grids, the higher the oscilloscope bandwidth. When the voltage between cathode and gate is greater than 3.4kV, the theoretical bandwidth is higher than 1000GHz.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. As for the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

Professionals may further realize that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in this embodiment can be implemented by electronic hardware, computer software or a combination of the two, in order to clearly illustrate the hardware and software In the above description, the components and steps of each example have been generally described according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Skilled artisans may use different methods of implementing the described functionality for each particular application, but such implementations should not be considered beyond the scope of the present invention.

The steps of the method or algorithm described in conjunction with the embodiments disclosed in this embodiment may be directly implemented by hardware, a software module executed by a processor, or a combination of the two. A software module can be placed in random access memory (RAM), internal memory, read only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other in the technical field. in any other known form of storage medium.

The above embodiments are only intended to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement accordingly, and cannot limit the protection scope of the present invention. All equivalent changes and modifications made with the scope of the claims of the present invention shall fall within the scope of the claims of the present invention.

Claims (10)

1. An electron beam time amplification oscilloscope, characterized in that it comprises a microstrip cathode (101), an anode grid (102), a magnetic focusing lens (103), an MCP picture tube (104), a CCD and a high-voltage pulse generator (105) ), the positive output terminal of the high-voltage pulse generator (105) is connected to the microstrip cathode (101), and the negative output terminal of the high-voltage pulse generator (105) is connected to the MCP image tube (104), so The anode grid (102) is grounded; the microstrip cathode (101), the anode grid (102), the MCP picture tube (104) and the CCD are arranged in sequence, and the microstrip cathode (102) 101), the anode grid (102), the MCP picture tube (104) and the CCD are coaxially disposed; the magnetic focusing lens (103) is located on the anode grid (102) and the MCP between the image changing tubes (104);

   The microstrip cathode (101) generates photoelectrons under the irradiation of incident light, a negative DC bias voltage is applied to the microstrip cathode (101) and a high-voltage ramp pulse is superimposed, and the optical pulse is synchronized on the rising edge of the high-voltage ramp pulse; The photoelectrons pass through the anode grid (102) and enter the drift region between the anode grid (102) and the MCP image tube (104), and the photoelectrons are in the magnetic field of the magnetic focusing lens (103) The electron beam formed by the expansion under the action is imaged on the MCP image tube (104), the CCD records the visible light output by the MCP image tube (104), and then obtains the detection waveform by analyzing and processing the light spot image.
2. The electron beam time amplification oscilloscope according to claim 1, wherein the microstrip cathode (101) comprises a quartz glass plate and three gold cathode microstrip lines evaporated on the quartz glass plate, each of which is The thickness of the gold cathode microstrip line is 80nm and the width is 8mm; the three gold cathode microstrip lines are arranged in parallel, and the interval between the adjacent gold cathode microstrip lines is 2.8mm.
3. The electron beam time magnification oscilloscope according to claim 1, characterized in that, the magnetic focusing lens (103) comprises soft iron and 1200-turn copper coils, the outer diameter of the magnetic focusing lens (103) is 256 mm, and the The inner diameter of the magnetic focusing lens (103) is 160 mm, and the axial length of the magnetic focusing lens (103) is 100 mm; the inner ring of the magnetic focusing lens (103) has a gap with a width of 4 mm.
4. The electron beam time amplification oscilloscope according to claim 1, characterized in that, the MCP picture tube (104) comprises an impedance gradient line (1041), a microchannel plate (1042), and is vapor-deposited on the microchannel plate (1042) three microstrip lines (1043) on the optical fiber panel and a fluorescent screen (1044) made on the optical fiber panel, the microstrip lines (1043) face the anode grid (102) side, and the fluorescent screen (1044) is located on the microstrip (1044) side. between the channel plate (1042) and the CCD; the negative output end of the high-voltage pulse generator (105) is connected to the microstrip line (1043) through the impedance gradient line (1041);

   The outer diameter of the microchannel plate (1042) is 56mm, the thickness is 0.5mm, the channel diameter is 12μm, and the chamfer angle is 6°; the width of the microstrip line (1043) is 8mm, and the three microstrip lines are (1043) are arranged in parallel, and the interval between two adjacent microstrip lines (1043) is 2.8 mm; the microchannel plate (1042) and the phosphor screen (1044) are placed in parallel, and the microchannel plate (1042) ) and the phosphor screen (1044) at a distance of 0.5 mm.
5. The electron beam time amplification oscilloscope according to claim 1, wherein the high-voltage pulse generator (105) comprises an avalanche triode circuit (1051) and a diode pulse circuit (1052), and the avalanche triode circuit (1051) generates The high voltage ramp pulse is divided into two parts, one part is input to the microstrip cathode (101) through the impedance gradient line (1041), and the other part is used to drive the diode pulse circuit (1052) to generate the MCP strobe pulse.
6. The electron beam time amplification oscilloscope according to claim 1, characterized in that, the microstrip cathode (101) is connected to a first attenuator (1061), and the first attenuator (1061) absorbs the passing through the microstrip The high voltage ramp pulse after the cathode (101); the microstrip line (1043) of the MCP picture tube (104) is connected to the second attenuator (1062), and the second attenuator (1062) absorbs the MCP strobe after strip line (1043).
7. The electron beam time amplification oscilloscope according to claim 1, characterized in that, the microstrip cathode (101) generates photoelectrons after receiving incident light, and the photoelectrons fly to the limit of the magnetic field of the magnetic focusing lens (103). The MCP image changing tube (104); the moment when the photoelectrons whose emission time is t _i arrives at the MCP image changing tube (104) is:

   

   Wherein, L is the length of the drift region, e is the photoelectron charge, e=1.6×10 ^-19 C; m is the photoelectron mass, m=9.1×10 ^-31 kg;

   

   is the voltage difference between the microstrip cathode (101) and the anode grid (102), _VB is the cathode bias voltage, and _VP (t) is the voltage value of the cathode pulse synchronized with the light pulse at time t ;

   The electron beam time magnification M can be expressed as:

   

   Then the technical time resolution of the electron beam time amplification oscilloscope is:

   

   Wherein, T _MCP is the time resolution of the MCP picture tube (104);

   The time resolution of the electron beam time amplification oscilloscope is:

   

   T _phys is the physical time resolution, which depends on the electron transit time dispersion between the microstrip cathode (101) and the anode grid (102):

   

   E=[-V _B -V _P (t)]/L _pa (6)

   The unit of T _phys is ps, where δε is the initial energy distribution of photoelectrons, and the unit is eV. Under the irradiation of ultraviolet laser with a wavelength of 260 nm, the initial energy distribution of photoelectrons generated by the microstrip cathode (101) is 0.5 eV; E is the electric field strength between the microstrip cathode (101) and the anode grid (102), in kV/mm; Lpa is the difference between the microstrip cathode (101) and the anode grid (102) distance between.
8. An electron beam time amplification oscilloscope measurement system, characterized in that it comprises the electron beam time amplification oscilloscope according to any one of claims 1 to 7, and the system further comprises a laser light source (201), a photodetector (202) , a delay circuit (203), an optical fiber bundle (204) and a parallel light pipe (205), the optical fiber bundle (204) includes a plurality of optical fibers, and the lengths of the multiple optical fibers are distributed in an arithmetic progression;

   The laser light source (201) includes a first output end for outputting a first wavelength laser light and a second output end for outputting a second wavelength laser light, and the laser light emitted by the first output end passes through the fiber bundle (204) ) is incident on the collimator (205), and after being transmitted by the collimator (205), it is incident on the microstrip cathode (101) of the electron beam time amplification oscilloscope; the laser emitted by the second output end is input to the The photodetector (202), the generated electrical signal is delayed by the delay circuit (203) and then input to the input end of the high-voltage pulse generator (105) of the electron beam time amplification oscilloscope.
9. The electron beam time amplification oscilloscope measurement system according to claim 8, wherein the optical fiber bundle (204) comprises 30 multimode optical fibers, and the 30 multimode optical fibers are arranged in a rectangle adjacent to each other, and the rectangle includes three rows of more than 30 multimode optical fibers. Mode fiber, there are 10 multimode fibers in each row; the length of 30 multimode fibers increases in arithmetic progression according to the arrangement order, and the tolerance of arithmetic progression is 2mm.
10. The electron beam time amplification oscilloscope measurement system according to claim 8, wherein the first wavelength laser is a 266 nm laser, and the second wavelength laser is an 800 nm laser.

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