CN109374595B - Ultrafast pulse radiolysis detection system - Google Patents
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- CN109374595B CN109374595B CN201811520171.1A CN201811520171A CN109374595B CN 109374595 B CN109374595 B CN 109374595B CN 201811520171 A CN201811520171 A CN 201811520171A CN 109374595 B CN109374595 B CN 109374595B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/66—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
- G01N2021/0106—General arrangement of respective parts
- G01N2021/0112—Apparatus in one mechanical, optical or electronic block
Abstract
According to the detection system for ultrafast pulse radiolysis, provided by the invention, the electron gun is used for generating the electron beam group with large charge amount, and then the acceleration device is used for accelerating and phase compression, so that the beam group length compression is effectively carried out on the electron beam group with large charge amount, the pulse width can reach the femtosecond magnitude, and the ultrafast pulse radiolysis is effectively realized. Meanwhile, the electron beam group has the characteristic of short beam group and large charge quantity, and the length of the beam group is equivalent to the terahertz wavelength, so that coherent radiation can be realized in the terahertz wavelength range, the terahertz radiation power is greatly improved, and the detection efficiency is improved. Furthermore, since the second electron bunch for pumping and the terahertz light for detection are based on a homologous electron beam, fully synchronized and precisely time-adjusted pumping detection can be achieved.
Description
Technical Field
The invention relates to the technical fields of radiochemistry, electron accelerators and terahertz, in particular to a detection system for ultrafast pulse radiolysis.
Background
The pulse radiolysis technology integrates an electron beam excitation method and a time-resolved detection method, is an important technical means for researching a radiation chemistry basic process, and has wide application in the fields of physics, chemistry, biology and the like. In order to study chemical mechanisms in ultra-short time scales or reaction processes of more complex reaction systems, pulse radiolysis systems with higher time resolution and more advanced detection technologies need to be designed.
Disclosure of Invention
In view of the above, to solve the above problems, the present invention provides a detection system for ultrafast pulse radiolysis, and the technical scheme is as follows:
a detection system for ultrafast pulse radiolysis, the detection system comprising: the device comprises a laser source, a time-delay beam splitting device, an electron gun, an accelerating device, a transverse focusing structure, a radiation medium, a power source subsystem, a control subsystem, a focusing and turning structure with a transmission hole and a first time-delay light path;
wherein the electron gun and the accelerating device are positioned inside the transverse focusing structure, and the electron gun, the accelerating device and the transverse focusing structure are coaxially arranged;
the laser source is used for emitting laser pulses to the time-delay beam splitting device;
the time delay beam splitting device is used for converting the laser pulse into a first laser pulse and a second laser pulse;
the electron gun is used for converting the first laser pulse and the second laser pulse into a first electron beam group and a second electron beam group;
the acceleration device is used for performing phase compression and energy boosting on the first electron beam group and the second electron beam group;
the transverse focusing structure is used for transversely focusing the first electron beam group and the second electron beam group;
the radiation medium is used for deflecting the track of the first electron beam group and generating terahertz light, and the terahertz light is incident to the surface of the sample through the first time-delay light path;
the radiation medium is also used for transmitting the second electron beam group along a straight line and enabling the second electron beam group to be incident to the surface of the sample through the transmission hole of the focusing and direction changing structure;
the power source subsystem is used for providing microwave power for the electron gun and the accelerating device;
the control subsystem is used for controlling the working states of the laser source, the power source subsystem and the radiation medium.
Preferably, the time-delay beam splitting device includes: the half-wave plate, the polarization beam splitter, the second time delay light path and the polarization beam combiner;
the half-wave plate is used for adjusting the polarization direction of the laser pulse;
the polarization beam splitter is used for splitting the laser pulse processed by the half-wave plate into a first path of laser pulse and a second path of laser pulse;
the first path of laser pulse directly enters the polarization beam combiner, and the second path of laser pulse passes through the second delay light path and then enters the polarization beam combiner, and is converged at the polarization beam combiner to form a laser pulse pair, namely, a first laser pulse and a second laser pulse.
Preferably, the time-delay beam splitting device further includes: a plurality of mirrors;
the mirror is used for changing the optical paths of the laser pulse, the first laser pulse and the second laser pulse.
Preferably, the acceleration device includes: a compression section traveling wave accelerating tube and an energy increasing section traveling wave accelerating tube;
the electron gun, the compression section traveling wave accelerating tube and the energy increasing section traveling wave accelerating tube are sequentially arranged on the axis.
Preferably, the distance between the electron gun and the compression section traveling wave accelerating tube is 1.0m-1.7 m;
the distance between the compression section traveling wave accelerating tube and the energy rising section traveling wave accelerating tube is 0.1m-1.0 m;
the length of the compression section traveling wave accelerating tube is 1.1m-1.2 m;
the length of the energy-increasing section traveling wave accelerating tube is 1.5m-3 m.
Preferably, the lateral focusing structure includes: a first section, a second section, a third section, and a fourth section;
the first part surrounds the electron gun, the second part surrounds one end, adjacent to the electron gun, of the compression section traveling wave accelerating tube, the third part surrounds one end, adjacent to the energy rising section traveling wave accelerating tube, of the compression section traveling wave accelerating tube, and the fourth part surrounds one end, adjacent to the compression section traveling wave accelerating tube, of the energy rising section traveling wave accelerating tube.
Preferably, the lateral focusing structure is a solenoid coil.
Preferably, the focusing and direction-changing structure is an off-axis parabolic mirror.
Compared with the prior art, the invention has the following beneficial effects:
according to the detection system for ultrafast pulse radiolysis, provided by the invention, the electron gun is used for generating the electron beam group with large charge amount, and then the acceleration device is used for accelerating and phase compression, so that the beam group length compression is effectively carried out on the electron beam group with large charge amount, the pulse width can reach the femtosecond magnitude, and the ultrafast pulse radiolysis is effectively realized.
Meanwhile, the electron beam group has the characteristic of short beam group and large charge quantity, and the length of the beam group is equivalent to the terahertz wavelength, so that coherent radiation can be realized in the terahertz wavelength range, the terahertz radiation power is greatly improved, and the detection efficiency is improved.
Furthermore, since the second electron bunch for pumping and the terahertz light for detection are based on a homologous electron beam, fully synchronized and precisely time-adjusted pumping detection can be achieved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a detection system for ultrafast pulse radiolysis according to an embodiment of the present invention;
fig. 2 is a schematic diagram of electric field gradient distribution at different longitudinal positions set during detection by the ultrafast pulse radiolysis detection system according to the embodiment of the present invention;
fig. 3 is a schematic diagram of magnetic induction intensity distribution at different longitudinal positions set when the ultrafast pulse radiolysis detection system provided by the embodiment of the present invention performs detection;
fig. 4 is a schematic diagram illustrating electron beam distributions at different longitudinal positions during detection by the ultrafast pulse radiolysis detection system according to the embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating the variation of the rms pulse length of an electron beam at different longitudinal positions when the ultrafast pulse radiolysis detection system provided by the embodiment of the present invention performs detection;
fig. 6 is a schematic diagram of the current intensity distribution of an electron beam group when the detection system for ultrafast pulse radiolysis according to the embodiment of the present invention detects;
FIG. 7 is a schematic diagram of the current intensity distribution of an electron beam group during detection by an ultrafast pulse radiolysis detection system according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a cluster factor distribution of electron beams passing through a radiation medium and a radiation power spectrum of terahertz light generated by the detection system for ultrafast pulse radiolysis according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a clustering factor distribution of electron beams passing through a radiation medium and a radiation power spectrum of terahertz light generated by the detection system for ultrafast pulse radiolysis according to the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Based on the description of the background art, the pulse radiolysis technology integrates the electron beam excitation and the time-resolved detection method, is an important technical means for the research of the radiation chemistry basic process, and has wide application in the fields of physics, chemistry, biology and the like. In order to study chemical mechanisms in ultra-short time scales or reaction processes of more complex reaction systems, pulse radiolysis systems with higher time resolution and more advanced detection technologies need to be designed.
The resolution of the pulse radiolysis system is limited by factors such as pulse widths of the electron beam and the detection light and synchronous time jitter between the electron beam and the detection light, and the current technology reaches picosecond magnitude. To further improve the time resolution, the reduction of the pulse width of the electron beam is a key issue.
With the development of the electron accelerator technology, the new generation accelerator can meet the requirement of pulse radiolysis, the femtosecond pulse radiolysis technology is a research means based on femtosecond electron beams and a high-resolution detection system, and the system has higher resolution. Therefore, development of a technique for generating ultra-short electron beams with a large charge amount is required, and is of great significance in fields such as radiochemical research.
At present, the ultrafast pulse radiolysis system adopts a pulse probe detection technology, most of detection wavelengths are located in an ultraviolet-near infrared band, and the penetrating power is weak. The terahertz wave is an electromagnetic wave with the frequency of 0.1THz-10.0THz, has strong penetrating power and low photon energy, and is suitable for various systems of various materials. If the time-resolved terahertz spectrum detection technology is applied to an ultrafast pulse radiolysis system, the detection spectrum frequency band and the research system of the ultrafast pulse radiolysis are greatly expanded.
Based on the above, the invention provides an ultrafast pulse radiolysis detection system, which utilizes an electron gun and an accelerating device to generate a large-charge-amount ultrashort beam group electron beam for ultrafast pulse radiolysis and utilizes synchronous homologous high-power terahertz light for detection.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a detection system for ultrafast pulse radiolysis according to an embodiment of the present invention, where the detection system includes: the device comprises a laser source 10, a time-delay beam splitting device 11, an electron gun 12, an accelerating device 13, a transverse focusing structure 14, a radiation medium 15, a power source subsystem 16, a control subsystem 17, a focusing and direction-changing structure 18 with a transmission hole and a first time-delay light path 19;
wherein the electron gun 12 and the accelerating device 13 are located inside the transverse focusing structure 14, and the electron gun 12, the accelerating device 13 and the transverse focusing structure 14 are coaxially arranged;
the laser source 10 is configured to emit a laser pulse to the delayed beam splitting device 11;
the delayed beam splitting device 11 is used for converting the laser pulse into a first laser pulse and a second laser pulse;
the electron gun 12 is configured to convert the first laser pulse and the second laser pulse into a first electron beam bunch and a second electron beam bunch;
the acceleration device 13 is used for performing phase compression and energy boosting on the first electron beam group and the second electron beam group;
the transverse focusing structure 14 is used for transversely focusing the first electron beam bunch and the second electron beam bunch;
the radiation medium 15 is configured to deflect the trajectory of the first electron bunch and generate terahertz light, where the terahertz light is incident on the surface of the sample 20 through the first time-delay optical path 19;
the radiation medium 15 is further used for transmitting the second electron beam group along a straight line and is incident on the surface of the sample 20 through the transmission hole of the focusing and redirecting structure 18;
the power source subsystem 16 is used for providing microwave power for the electron gun 12 and the accelerating device 13;
the control subsystem 17 is used to control the operating states of the laser source 10, the power source subsystem 16 and the radiation medium 15.
In this embodiment, the electron beam bunch with large charge amount is generated by the electron gun 12, and then accelerated and phase-compressed by the accelerating device 13, so as to effectively compress the beam bunch length of the electron beam bunch with large charge amount, and the pulse width can reach femtosecond level, thereby effectively realizing ultrafast pulse radiolysis.
Meanwhile, the electron beam group has the characteristic of short beam group and large charge quantity, and the length of the beam group is equivalent to the terahertz wavelength, so that coherent radiation can be realized in the terahertz wavelength range, the terahertz radiation power is greatly improved, and the detection efficiency is improved.
Furthermore, since the second electron bunch for pumping and the terahertz light for detection are based on a homologous electron beam, fully synchronized and precisely time-adjusted pumping detection can be achieved.
Optionally, the electron gun 12 includes, but is not limited to, a photocathode microwave electron gun, and is not limited in the embodiment of the present invention.
In this embodiment, the electron gun 12 is further configured to accelerate the first and second electron cluster beams.
Further, as shown in fig. 1, the delay beam splitting device 11 includes: a half-wave plate 111, a polarization beam splitter 112, a second delay optical path 113 and a polarization beam combiner 114;
the half-wave plate 111 is used for adjusting the polarization direction of the laser pulse;
the polarization beam splitter 112 is configured to split the laser pulse processed by the half-wave plate 111 into a first laser pulse and a second laser pulse;
the first laser pulse is directly incident to the polarization beam combiner 114, and the second laser pulse is incident to the polarization beam combiner 114 through the second delay optical path 113, and is converged at the polarization beam combiner 114 to form a laser pulse pair, that is, a first laser pulse and a second laser pulse.
In this embodiment, the half-wave plate 111 and the polarization beam splitter 112 divide the laser pulse emitted by the laser source into two paths, the transmission direction and the polarization direction of the two paths of laser pulses are perpendicular to each other, wherein one path of laser pulse passes through the second delay optical path 113 and then joins with the other path of laser pulse that does not pass through the second delay optical path 113 at the polarization beam splitter 114 to form a laser pulse pair, that is, a first laser pulse and a second laser pulse, and two pulses of the laser pulse pair have a certain time interval therebetween.
Further, as shown in fig. 1, the delay beam splitting device 11 further includes: a plurality of mirrors 115;
the mirror 115 is used to change the optical paths of the laser pulses, the first laser pulses and the second laser pulses.
In this embodiment, the mirror 115 is used to change the optical paths of the laser pulse, the first laser pulse and the second laser pulse, so that the first laser pulse and the second laser pulse are finally incident on the cathode surface of the electron gun in a nearly perpendicular manner.
It should be noted that the number of the reflecting mirrors 115 is not limited in the embodiment of the present invention, and the reflecting mirrors may be specifically arranged according to the installation position of the detection system, and the reflecting mirrors may also be flexibly arranged at other positions of the detection system.
Further, as shown in fig. 1, the acceleration device 13 includes: a compression section traveling wave accelerating tube 131 and an energy-raising section traveling wave accelerating tube 132;
the electron gun 12, the compression section traveling wave accelerating tube 131, and the energy boost section traveling wave accelerating tube 132 are arranged in this order on the axis.
In this embodiment, the compression-stage traveling wave acceleration tube 131 is used for performing phase compression on the first electron beam group and the second electron beam group;
the energy-increasing section traveling wave accelerating tube 132 is used for performing capacity improvement on the first electron beam group and the second electron beam group.
Further, the distance between the electron gun 12 and the compression section traveling wave accelerating tube 131 is 1.0m to 1.7 m.
Specifically, when the distance between the electron gun 12 and the compression-stage traveling wave acceleration tube 131 is too far or too close, the final effect of the lateral focusing of the first electron beam group and the second electron beam group is affected, and therefore, in the embodiment of the present invention, the distance between the electron gun 12 and the compression-stage traveling wave acceleration tube 131 is optionally 1.4 m.
Further, the distance between the compression section traveling wave accelerating tube 131 and the energy-raising section traveling wave accelerating tube 132 is 0.1m-1.0 m.
In this embodiment, a suitable beam measuring element is placed between the compression-stage traveling-wave accelerating tube 131 and the energy-raising-stage traveling-wave accelerating tube 132, the beam measuring element cannot be placed when the distance is too close, and the structure of the detection system is not compact enough when the distance is too far, so in this embodiment of the present invention, optionally, the distance between the compression-stage traveling-wave accelerating tube 131 and the energy-raising-stage traveling-wave accelerating tube 132 is 0.14 m.
Further, the length of the compression section traveling wave accelerating tube 131 is 1.1m to 1.2m, including end point values; the length of the energy-rising section traveling wave accelerating tube 132 is 1.5m-3 m.
In this embodiment, the length of the energy boost section traveling wave acceleration tube 132 needs to be set according to the energy of the first electron beam group and the second electron beam group, when high energy is needed, the length of the energy boost section traveling wave acceleration tube 132 is lengthened, and when low energy is needed, the length of the energy boost section traveling wave acceleration tube 132 is shortened, therefore, in this embodiment of the present invention, the length of the energy boost section traveling wave acceleration tube 132 is 1.6m, and the energy of the first electron beam group and the second electron beam group is about 30 MeV.
Further, as shown in fig. 1, the lateral focusing structure 14 includes: a first portion 141, a second portion 142, a third portion 143, and a fourth portion 144;
the first portion 141 surrounds the electron gun 12, the second portion 142 surrounds an end of the compression-stage traveling-wave acceleration tube 131 adjacent to the electron gun 12, the third portion 143 surrounds an end of the compression-stage traveling-wave acceleration tube 131 adjacent to the energy-rising-stage traveling-wave acceleration tube 132, and the fourth portion 144 surrounds an end of the energy-rising-stage traveling-wave acceleration tube 132 adjacent to the compression-stage traveling-wave acceleration tube 131.
In this embodiment, the first portion 141 surrounds the electron gun 12 for instantaneously suppressing the increase in beam emittance.
The second part 142 and the third part 143 are disposed at two ends of the traveling wave accelerating tube 13 in the compression section, and the transverse focusing structure 14 is not disposed in the middle part, because the transverse focusing constraint is properly released during the longitudinal compression of the beam, so that the beam can be effectively compensated for emittance and transversely focused, and can also be effectively longitudinally compressed.
Further, the lateral focusing structure 14 includes, but is not limited to, a solenoid coil.
In this embodiment, the lateral focusing structure 14 may also be a four-pole iron, for example, but in a low-energy electron accelerator, the use of a solenoid coil can be installed outside the accelerating device, and has better emittance compensation and focusing effects for lower-energy electron beams.
Further, the radiation medium 15 includes, but is not limited to, a strip electrode, and the focus redirecting structure 18 includes, but is not limited to, an off-axis parabolic mirror.
Further, as shown in fig. 1, the power source subsystem 16 includes a power source 161 and a power divider 162.
In this embodiment, the power source 161 provides microwave power to the electron gun 12 and the accelerating device 13 through the power divider 162 according to a specific ratio, and the amplitude and phase of the microwave electric field in the accelerating device 13 can be adjusted through a phase-shift attenuator to meet the requirements of length compression and energy boost of the first electron beam bunch and the second electron beam bunch.
Based on all the above embodiments of the present invention, the principle thereof will be specifically explained below.
The control subsystem 17 controls the laser source 10 to emit a laser pulse, the laser pulse is converted into a first laser pulse and a second laser pulse through the delay beam splitting device 11, the first laser pulse and the second laser pulse are incident on the cathode surface of the photocathode microwave electron gun 12 to generate a first electron beam group and a second electron beam group, the first electron beam group and the second electron beam group are accelerated under the acceleration action of a microwave electric field of the photocathode microwave electron gun 12, enter the accelerating device 13 to be subjected to phase compression and energy promotion, and are transversely focused under the action of the transverse focusing structure 14, so that the first electron beam group and the second electron beam group with the improved charge quantity and the shorter pulse width are obtained.
The first electron beam group and the second electron beam group enter a radiation medium 15, the track of the first electron beam group deflects and generates high-power terahertz light under the control of a control subsystem 17, the second electron beam group is transmitted along a straight line and is incident to the surface of a sample through a transmission hole of a focusing and turning structure 18, the high-power terahertz light is focused by an off-axis parabolic mirror in the focusing and turning structure 18 and then is incident to a region of the sample 20 through a first delay light path 19, the second electron beam group of the sample 20 and the high-power terahertz light can be completely synchronized by adjusting the first delay light path 19, and the purpose that the sample is detected by the same-source synchronous terahertz light after the electron beam group pumps the sample is further achieved.
Furthermore, the control subsystem 17 functions as a clock control in addition to controlling the radiation medium 15 to apply a pulsed voltage only when the first electron beam bunch passes. Wherein the clock signal is provided by the laser source 10 and the control subsystem 17 provides multiple paths of timing signals with independently adjustable delays.
Referring to fig. 2, fig. 2 is a schematic diagram of electric field gradient distribution set at different longitudinal positions when the detection system for ultrafast pulse radiolysis according to the embodiment of the present invention performs detection.
Wherein, the electric field gradient distribution in the photocathode microwave electron gun 12, the compression section traveling wave accelerating tube 131 and the energy increasing section traveling wave accelerating tube 132 respectively corresponds to the left to the right.
The microwave phase of the photocathode microwave electron gun 12 is set to a phase value at which the energy dispersion and emittance of the electron beam at the outlet are small, the compression-stage traveling-wave accelerating tube 131 is set to a deceleration phase, and the energy-boost-stage traveling-wave accelerating tube 132 is set to a maximum energization phase.
Referring to fig. 3, fig. 3 is a schematic view of magnetic induction intensity distribution at different longitudinal positions set during detection by the ultrafast pulse radiolysis detection system according to the embodiment of the present invention.
The four wave packets from left to right respectively correspond to the magnetic induction intensity distribution of the first portion 141, the second portion 142, the third portion 143 and the fourth portion 144 in the transverse focusing structure.
Referring to fig. 4, fig. 4 is a schematic diagram of electron beam distributions at different longitudinal positions during detection by the ultrafast pulse radiolysis detection system according to the embodiment of the present invention.
The first electron beam bunch and the second electron beam bunch respectively have the charge amount of 1nC, and it can be seen that the kinetic energy of the electron beam is increased from 0 to about 4MeV after passing through the electron gun, and the final kinetic energy of the electron beam is about 30MeV after passing through the accelerating device.
Referring to fig. 5, fig. 5 is a schematic diagram illustrating variation of rms pulse length of an electron beam at different longitudinal positions when the ultrafast pulse radiolysis detection system provided in the embodiment of the present invention performs detection.
The first electron beam group and the second electron beam group respectively contain 1nC of electric charge, the beam groups are subjected to deceleration phase beam group length compression in the compression section traveling wave accelerating tube, and the rms pulse length of the compressed electron beam is 220fs, as shown in fig. 6 specifically.
When the first and second electron bunches have a charge of 0.5nC, respectively, the optimized electron beam rms pulse length is 110fs, as shown in fig. 7.
According to the requirements of the pulse radiolysis process on the radiolysis dose and the pulse length, different charge quantity modes can be selected. After the electric charge quantity is changed, the electric field gradient and the microwave phase of the corresponding compression section traveling wave accelerating tube and the magnetic field intensity of the transverse focusing structure need to be optimized correspondingly. The magnitude of the charge amount can be controlled by adjusting the laser pulse energy, and the charge amount distribution of two electron bunches in one electron bunch pair can be controlled by adjusting the distribution of the laser energy through a half-wave plate.
Referring to fig. 8, fig. 8 is a schematic diagram of a cluster factor distribution of electron beams passing through a radiation medium and a radiation power spectrum of terahertz light generated by the detection system for ultrafast pulse radiolysis according to the embodiment of the present invention.
The electric charge quantity of the electron beam is 1nC, the length of the radiation medium which is a strip electrode is about 50cm, the radiation mechanism is coherent synchronous radiation, the terahertz frequency spectrum covers 0THz-2THz, and the peak power is about 0.65 MW.
Referring to fig. 9, fig. 9 is a schematic diagram of a clustering factor distribution of electron beams passing through a radiation medium and a radiation power spectrum of terahertz light generated by the detection system for ultrafast pulse radiolysis according to the embodiment of the present invention.
The charge quantity of the electron beam is reduced to 0.5nC, and because the pulse length of the electron beam is shorter, the radiation power spectrum is greatly widened and covers 0THz-10THz, and meanwhile, the peak power is obviously improved.
If the femtosecond pulse radiolysis with larger charge amount and the terahertz detection technology with wider spectrum and high power are needed to be realized simultaneously, the charge amount of a first electron beam group with 0.5nC and the charge amount of a second electron beam group with 1nC of an electron beam group pair can be enabled by adjusting the setting of laser energy and a half-wave plate, and simultaneously, the phase and the electric field gradient of the electron beam group pair entering a microwave field are respectively set, so that the first electron beam group generates terahertz light with higher power and wider spectrum for detection, and the second electron beam group has larger charge amount for the femtosecond pulse radiolysis, thereby optimizing the time resolution of the ultrafast pulse radiolysis.
The ultrafast pulse radiolysis detection system provided by the invention is described in detail, a specific example is applied in the description to explain the principle and the implementation mode of the invention, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include or include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. A detection system for ultrafast pulse radiolysis, the detection system comprising: the device comprises a laser source, a time-delay beam splitting device, an electron gun, an accelerating device, a transverse focusing structure, a radiation medium, a power source subsystem, a control subsystem, a focusing and turning structure with a transmission hole and a first time-delay light path;
wherein the electron gun and the accelerating device are positioned inside the transverse focusing structure, and the electron gun, the accelerating device and the transverse focusing structure are coaxially arranged;
the laser source is used for emitting laser pulses to the time-delay beam splitting device;
the time delay beam splitting device is used for converting the laser pulse into a first laser pulse and a second laser pulse;
the electron gun is used for converting the first laser pulse and the second laser pulse into a first electron beam group and a second electron beam group;
the acceleration device is used for performing phase compression and energy boosting on the first electron beam group and the second electron beam group;
the transverse focusing structure is used for transversely focusing the first electron beam group and the second electron beam group;
the radiation medium is used for deflecting the track of the first electron beam group and generating terahertz light, and the terahertz light is incident to the surface of the sample through the first time-delay light path;
the radiation medium is also used for transmitting the second electron beam group along a straight line and enabling the second electron beam group to be incident to the surface of the sample through the transmission hole of the focusing and direction changing structure;
the power source subsystem is used for providing microwave power for the electron gun and the accelerating device;
the control subsystem is used for controlling the working states of the laser source, the power source subsystem and the radiation medium.
2. The detection system of claim 1, wherein the time-delay beam splitting means comprises: the half-wave plate, the polarization beam splitter, the second time delay light path and the polarization beam combiner;
the half-wave plate is used for adjusting the polarization direction of the laser pulse;
the polarization beam splitter is used for splitting the laser pulse processed by the half-wave plate into a first path of laser pulse and a second path of laser pulse;
the first path of laser pulse directly enters the polarization beam combiner, and the second path of laser pulse passes through the second delay light path and then enters the polarization beam combiner, and is converged at the polarization beam combiner to form a laser pulse pair, namely, a first laser pulse and a second laser pulse.
3. The detection system of claim 2, wherein the time-delay beam splitting apparatus further comprises: a plurality of mirrors;
the mirror is used for changing the optical paths of the laser pulse, the first laser pulse and the second laser pulse.
4. The detection system according to claim 1, wherein the acceleration device comprises: a compression section traveling wave accelerating tube and an energy increasing section traveling wave accelerating tube;
the electron gun, the compression section traveling wave accelerating tube and the energy increasing section traveling wave accelerating tube are sequentially arranged on the axis.
5. The detection system according to claim 4, wherein the distance between the electron gun and the compression section traveling wave accelerating tube is 1.0m-1.7 m;
the distance between the compression section traveling wave accelerating tube and the energy rising section traveling wave accelerating tube is 0.1m-1.0 m;
the length of the compression section traveling wave accelerating tube is 1.1m-1.2 m;
the length of the energy-increasing section traveling wave accelerating tube is 1.5m-3 m.
6. The detection system of claim 4, wherein the lateral focusing arrangement comprises: a first section, a second section, a third section, and a fourth section;
the first part surrounds the electron gun, the second part surrounds one end, adjacent to the electron gun, of the compression section traveling wave accelerating tube, the third part surrounds one end, adjacent to the energy rising section traveling wave accelerating tube, of the compression section traveling wave accelerating tube, and the fourth part surrounds one end, adjacent to the compression section traveling wave accelerating tube, of the energy rising section traveling wave accelerating tube.
7. The detection system of claim 1, wherein the lateral focusing structure is a solenoid coil.
8. The detection system of claim 1, wherein the focus redirecting structure is an off-axis parabolic mirror.
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