Negative hydrogen accelerator beam measurement device and method based on laser lift-off

Abstract

The invention discloses a negative hydrogen accelerator beam measurement device and measurement method based on laser lift-off, a laser module of the measurement device is used for outputting laser, the laser scans a beam output by an accelerator along a first direction, the laser and the beam interact in a vacuum cavity, the beam is lift-off to form an H0 sub-beam cluster, and lift-off electrons are generated; the stripping electron collection module is used for collecting stripping electrons and generating stripping electron signals; the neutral hydrogen detection module is used for detecting neutral hydrogen beamlet clusters and generating beamlet cluster angle distribution signals; the at least one processor is used for obtaining a beam profile based on the interaction position of the laser and the beam and the stripping electronic signal; the beam phase space distribution acquisition module is also used for acquiring beam phase space distribution based on the interaction position of the laser and the beam and the beamlet group angle distribution signal; and the system is also used for determining the root-mean-square emittance of the beam by adopting a self-adaptive ellipse exclusion method according to the phase space distribution of the beam and determining the emittance of the beam by adopting the ellipse exclusion method, so that the beam profile with high time resolution and the real-time measurement of the emittance can be realized.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of particle accelerators, and in particular to a negative hydrogen accelerator beam measurement device and measurement method based on laser stripping. Background Art

[0002] Negative hydrogen linear accelerator is one of the important components driving modern high-intensity proton accelerators. In order to achieve efficient acceleration and high-quality injection of the bunch, it is necessary to control the beam quality, emittance and beam distribution of the negative hydrogen beam, and minimize the beam loss along the accelerator to reduce the residual dose after accelerator element activation and accelerator shutdown. Therefore, the beam transverse profile and emittance measurement have been the research hotspots in the direction of beam diagnosis of high-intensity linear accelerators in recent years.

[0003] Among them, beam emittance refers to the phase space area occupied by the beam in the beam phase space composed of the position coordinate x and momentum px of the particle in the beam. The emittance is proportional to the beam size and the angle of flare, and the unit is generally millimeter.mrad (mm.mrad). When measuring the emittance in practice, it can also be calculated using the phase space composed of the position coordinate x and the divergence angle x'. According to the given phase space distribution, the emittance can be calculated by statistical methods, and the calculated emittance is the RMS emittance (root mean square emittance).

[0004] In order to accurately evaluate the beam quality of the negative hydrogen linear accelerator and ensure the stable operation of the accelerator, a special beam diagnostic device must be used to accurately characterize the lateral distribution and emittance of the beam. For negative hydrogen beams, the traditional profile measurement methods mainly include wire scanning, multi-wire method and fluorescent screen imaging method, and the emittance measurement methods mainly include single slit scanning, multi-slit method and pepper pot method. These methods are based on the principle of direct interaction between the beam and the solid medium (wire or slit), and have strict requirements on the beam parameters and solid medium performance. For example, in order to ensure that the local temperature rise caused by the beam energy deposition in the solid medium is lower than the melting point and sublimation temperature of the material, the beam size, flow intensity and pulse must be within a reasonable range (generally evaluated through thermal analysis simulation or experiment, and retaining a certain margin).

[0005] When the above-mentioned traditional target method is used to measure beam profile and emittance, most of the beam is lost on the target, making it impossible to simultaneously take into account the normal beam supply and detection of the accelerator. Therefore, it is impossible to accurately evaluate the beam quality of the accelerator and ensure the stable operation of the accelerator. Summary of the invention

[0006] The present invention provides a negative hydrogen accelerator beam measurement device and measurement method based on laser stripping. The device adopts a novel laser stripping technology. Under the condition of not using a solid medium, the beam profile is measured by using a focused laser filament and a stripping electron collection module, and the emittance is measured by using a laser filament and a neutral hydrogen detection module. The beam quality of the accelerator can be accurately evaluated and the stable operation of the accelerator can be ensured.

[0007] In a first aspect, the present invention provides a negative hydrogen accelerator beam current measurement device based on laser stripping, comprising:

[0008] A laser module is used to output a laser, wherein the laser scans the beam output by the accelerator along a first direction, wherein the laser interacts with the beam in the vacuum chamber to strip the neutral hydrogen H from the beam. 0 Sub-bunches are formed and stripped electrons are generated; wherein the first direction is parallel to the beam forward tangent plane, and the first direction includes a vertical direction and a horizontal direction;

[0009] A stripping electron collection module, used for collecting the stripping electrons and generating a stripping electron signal;

[0010] A neutral hydrogen detection module is used to detect the neutral hydrogen H 0 sub-bunch and generate a sub-bunch angular distribution signal;

[0011] At least one processor is used to obtain a beam profile based on an interaction position between the laser and the beam and the stripping electron signal; to obtain a beam phase space distribution based on an interaction position between the laser and the beam and the sub-beam bunch angle distribution signal; and to determine the root mean square emittance of the beam using an adaptive ellipse exclusion method and the emittance of the beam using an ellipse exclusion method according to the beam phase space distribution.

[0012] Optionally, the laser module includes a laser, a laser transmission line and a scanning drive unit;

[0013] The processor is used to control the scanning driving unit to scan the laser beam along the first direction, and is also used to control the scanning range, scanning speed and scanning step length of the laser.

[0014] Optionally, the scanning driving unit includes a switching reflector, a scanning reflector and a focusing mirror; the scanning reflector includes a vertical scanning reflector and a horizontal scanning reflector; the focusing mirror includes a vertical focusing mirror and a horizontal focusing mirror;

[0015] The vertical scanning reflector and the vertical focusing mirror are located on the vertical optical path, and the horizontal scanning reflector and the horizontal focusing mirror are located on the horizontal optical path;

[0016] The switching reflector is used to switch the laser to be transmitted along a horizontal optical path or a vertical optical path.

[0017] Optionally, the stripping electron collection module includes a sector-shaped deflection magnet and a stripping electron collector, and the stripping electron collector includes a power supply, a Faraday cup, a signal amplifier and a data acquisition unit;

[0018] The power supply is used to supply power to the sector-shaped deflection magnet; the Faraday cup is used to collect stripping electrons and generate stripping electron signals; the signal amplifier is connected to the Faraday cup and the data acquisition unit respectively, and the data acquisition unit is connected to the processor.

[0019] Optionally, the beam includes neutral hydrogen, and the neutral hydrogen detection module includes a separation magnet, H 0 detector, the signal amplifier and the data acquisition unit; the H 0 The detector is used to collect neutral hydrogen and generate an electrical signal. The signal amplifier is also used to 0 Detector connections.

[0020] Optionally, the laser and beam interaction position is to the H 0 The preset distance L of the detector satisfies the H 0 The size of the sub-bunch on the detector detection screen is larger than the laser focusing spot size.

[0021] In a second aspect, an embodiment of the present invention provides a method for measuring a negative hydrogen accelerator beam based on laser stripping, wherein the negative hydrogen accelerator beam measuring device based on laser stripping provided in the first aspect is used to perform online beam measurement, and the measurement method includes:

[0022] The processor controls the laser module to output laser light, and controls the laser light to scan the beam output by the accelerator along a first direction. The laser light interacts with the beam light in the vacuum chamber to strip the neutral hydrogen H from the beam light. 0 sub-bunches and produces stripped electrons; wherein the first direction is parallel to the beam forward tangent plane; the first direction includes a vertical direction and a horizontal direction;

[0023] The processor controls the stripping electron collection module to collect the stripping electrons and generate a stripping electron signal, and obtains a beam profile based on the interaction position between the laser and the beam and the stripping electron signal;

[0024] The processor controls the neutral hydrogen detection module to detect the neutral hydrogen H 0 sub-bunches and generating a sub-bunch angle distribution signal, and obtaining a beam phase space distribution based on the interaction position between the laser and the beam and the sub-bunch angle distribution signal;

[0025] The processor determines the root mean square emittance of the beam by using an adaptive ellipse exclusion method according to the phase space distribution of the beam, and determines the emittance of the beam by using an ellipse exclusion method.

[0026] Optionally, the laser module includes a laser, a laser transmission line and a scanning drive unit; the scanning drive unit includes a switching reflector, a scanning reflector and a focusing mirror; before controlling the laser module to output laser, it also includes:

[0027] Initialize the laser module, stripping electron collection module, and neutral hydrogen detection module;

[0028] The processor controls the scanning range, scanning step length and moving speed of the scanning reflector;

[0029] The processor controls the scanning reflector to move along the first direction so that the focal point of the laser is located at the center of the beam, and adjusts the focusing mirror along the optical axis direction of the laser; controls the electron collection module to record the stripping electron signal intensity collected at different focusing positions, and sets the focusing mirror to the focusing position corresponding to the maximum stripping electron signal intensity.

[0030] Optionally, the stripping electron collection module includes a sector-shaped deflection magnet and a stripping electron collector; and the step of obtaining the beam profile includes:

[0031] The processor controls the scanning reflector to move to each scanning position in sequence along the first direction according to a preset scanning step length, controls the stripping electron collector to obtain the stripping electron signal, and draws the beam profile with each scanning position as the horizontal coordinate and the stripping electron signal intensity as the vertical coordinate.

[0032] Optionally, the neutral hydrogen detection module includes H 0 The steps of obtaining the beam phase space distribution include:

[0033] The processor controls the H 0 The detector collects the neutral hydrogen H after drifting a preset distance. 0 The sub-bunch generates the sub-bunch angle distribution signal according to H 0 The projection distribution of the sub-bunch in the first direction is determined based on the size of the sub-bunch angular distribution signal collected by the detector;

[0034] The processor calculates the divergence angle distribution corresponding to the position where the laser interacts with the beam according to the linear beam transmission theory, and establishes a transformation relationship between the sub-beam bunch and the corresponding divergence angle distribution;

[0035] The processor controls the scanning reflector 5 to move to each scanning position in sequence along the first direction according to a preset scanning step length, obtains the divergence angle distribution corresponding to each scanning position, and establishes the beam phase space distribution.

[0036] In summary, the negative hydrogen accelerator beam measurement device based on laser stripping provided by the present invention adopts a new laser stripping technology. Without using a solid medium, it uses a focused laser filament and a stripping electron collection module to perform real-time online measurement of the beam profile, and uses a laser filament and a neutral hydrogen detection module to perform real-time online measurement of the emittance. It can take into account the normal beam supply and detection of the accelerator at the same time, and can accurately evaluate the beam quality of the accelerator and ensure the stable operation of the accelerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of a negative hydrogen accelerator beam current measurement device based on laser stripping provided by the present invention;

[0038] Figure 2 It is a schematic diagram of another negative hydrogen accelerator beam current measurement device based on laser stripping provided by the present invention;

[0039] Figure 3 It is a schematic diagram of a laser module in a negative hydrogen accelerator beam measurement device provided by the present invention;

[0040] Figure 4 It is a schematic diagram of a stripping electron collection module in a negative hydrogen accelerator beam current measurement device provided by the present invention;

[0041] Figure 5 It is a schematic diagram of a neutral hydrogen detection module of a negative hydrogen accelerator beam current measurement device provided by the present invention;

[0042] Figure 6 It is a schematic diagram of a negative hydrogen accelerator beam measurement method based on laser stripping provided by the present invention. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0044] In the prior art, there are many problems with the traditional profile measurement method and emittance measurement method for negative hydrogen beam, as follows:

[0045] 1. The slit target (or wire target) needs to be inserted into the beam channel to interact directly with the beam, which will have a certain interception effect on the beam. It is impossible to perform real-time beam measurement when the particle accelerator is in operation. The particle accelerator device must be terminated and enter the debugging mode before the relevant beam parameter measurements can be performed.

[0046] 2. When the beam passes through the slit target (wire target), part of the beam energy is deposited in the material, resulting in local temperature rise and sputtering, shedding or sublimation of surface materials, which can easily cause surface contamination of key components such as superconducting acceleration cavity and radio frequency acceleration cavity, affecting the stable operation of the particle accelerator.

[0047] 3. During the interaction between the beam and the slit or wire, the charged particles lose some energy or their trajectory changes (scattering) under the action of the Coulomb field of the electrons and atomic nuclei stripped outside the nucleus of the solid material, causing local beam loss downstream of the detector, which can easily lead to radiation safety issues such as instantaneous dose exceeding the standard and material activation.

[0048] 4. The slit target material and wire material must have excellent thermal stability and high temperature resistance. For high-current negative hydrogen beam, carbon materials such as graphite, carbon fiber, and carbon nanotube wire are usually selected. However, these materials have large pores and poor vacuum compatibility, and require strict heat treatment before and after equipment installation. The operation process is complicated and requires a special vacuum pretreatment device.

[0049] In view of one or more of the above-mentioned problems existing in the prior art, the present invention proposes a negative hydrogen accelerator beam measurement device based on laser stripping in order to improve the measurement accuracy of beam profile and emittance while taking into account the normal beam supply and detection of the accelerator. Figure 1 is a schematic diagram of a negative hydrogen accelerator beam current measurement device based on laser stripping provided by the present invention, Figure 2 Schematic diagram of another negative hydrogen accelerator beam current measurement device based on laser stripping provided by the present invention. The negative hydrogen accelerator beam current measurement device based on laser stripping provided in the embodiment of the present application can realize online monitoring of negative hydrogen beam profile and emittance. Figure 1 and Figure 2 As shown, the negative hydrogen accelerator beam current measurement device includes a laser module 10, a stripping electron collection module 20, a neutral hydrogen detection module 30 and at least one processor ( Figure 1 and Figure 2 not shown).

[0050] refer to Figure 1 and Figure 2The processor may be a microprocessor, such as a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The processor may be disposed in the laser module 10, and connected to the stripping electron collection module 20 and the neutral hydrogen detection module 30, respectively, to control the laser module 10, the stripping electron collection module 20 and the neutral hydrogen detection module 30, and to receive and process signals fed back by the laser module 10, the stripping electron collection module 20 and the neutral hydrogen detection module 30, etc.

[0051] The laser module 10 is used to output laser S, and the laser S scans the beam H output by the accelerator along a first direction. - , laser S and beam H - interaction, the beam H - Stripping H 0 The sub-bunch generates stripped electrons e - Among them, the first direction is related to the beam H - The advancing tangent planes are parallel, and the first direction at least includes a horizontal direction X and a vertical direction Y.

[0052] It should be noted that the first direction may be in the direction of the beam H - In any direction parallel to the advancing tangent plane, the embodiment of the present application mainly takes scanning the beam advancing tangent plane along the horizontal direction X and the vertical direction Y as an exemplary illustration, and the beam can also be scanned in more directions to achieve more complete and omnidirectional online measurement of beam profile and emittance.

[0053] For example, the present application adopts a non-intercepting beam detection method. The processor controls the laser module 10 to output laser S. The laser S can be a pulsed laser, such as a nanosecond laser or a picosecond laser. The laser is in a pulsed form. After being focused, the area of ​​action with the beam is small, and it can appear as a laser filament near the beam waist. The embodiment of the present application adopts laser beam detection, which can be observed through the vacuum observation window ( Figure 1 and Figure 2 The laser S can be introduced into the vacuum chamber for beam detection. Specifically:

[0054] The processor 1 can switch the laser light path by controlling the scanning drive system in the laser module 10, so that the laser S scans the beam H in the vacuum chamber along the horizontal direction X or the vertical direction Y.- , the laser S acts on the beam forward tangent plane. - The laser lift-off reaction occurs at the interaction site, and the beam H - Stripping out neutral hydrogen H 0 The sub-bunch generates stripped electrons e - Among them, laser stripping reaction refers to the laser and H - When the energy of the laser photon exceeds the electron affinity of the hydrogen atom, an electron of the negative hydrogen atom is stripped away, resulting in stripped electron emission.

[0055] The stripping electron collection module 20 is located on the transmission path of the sub-bunch and is used to collect the stripping electrons e - The stripping electron signal is generated and transmitted to the processor. The processor is based on the laser S and the beam H. - The beam profile is obtained from the interaction position and stripped electron signal.

[0056] Specifically, the present application measures the stripping electron e - And generate the stripping electron signal, plot the laser S and beam H - The beam profile can be obtained by plotting the two-dimensional relationship between the interaction position of the laser and the stripped electron signal obtained at that position. It should be noted that the interaction time between the laser and the beam during the measurement is extremely short, only in the order of picoseconds or nanoseconds, and the effect of the detection equipment on the beam itself is almost negligible. Therefore, this method can realize real-time online monitoring of the accelerator beam profile without interfering with the stability of the beam or the normal operation of the accelerator.

[0057] The neutral hydrogen detection module 30 is located on the transmission path of the sub-bunch and is used to detect H 0 The sub-beam bunch generates a sub-beam bunch angle distribution signal, and transmits the sub-beam bunch angle distribution signal to the processor, and the processor obtains the beam phase space distribution based on the interaction position of the laser and the beam and the sub-beam bunch angle distribution signal. The processor is also used to determine the root mean square emittance of the beam using the adaptive ellipse exclusion method according to the beam phase space distribution, and determine the emittance of the beam using the ellipse exclusion method.

[0058] The phase space distribution of a beam is a physical concept that describes the joint distribution characteristics of the position and momentum (or velocity) of a charged particle beam in phase space. It is a core parameter for evaluating beam quality in the fields of accelerator physics and high-energy physics. Phase space is a multidimensional mathematical space, and each dimension corresponds to a degree of freedom of a particle.

[0059] The embodiment of the present invention utilizes a novel laser stripping technology. Without using a solid medium, the beam profile is measured using a focused laser filament and a stripping electron collection module, and the emittance is measured using a laser filament and a neutral hydrogen detection module. This can accurately evaluate the beam quality of the accelerator and ensure the stable operation of the accelerator.

[0060] Based on the above embodiments, Figure 3 Schematic diagram of the stripping electron collection module in the negative hydrogen accelerator beam current measurement device provided by the present invention. Based on the above embodiment, continue to refer to Figure 1 and Figure 2 The laser module 10 includes a scanning driving unit 2, a laser transmission line 3' and a laser 3. The processor 1 is connected to the laser 3 and the scanning driving unit 2 respectively; the processor 1 is used to control the scanning driving unit 3 to scan the laser S along the first direction, and is also used to control the scanning range, scanning speed and scanning step of the laser.

[0061] For example, the laser 3 can be a 1064nm nanosecond laser, and it is also necessary to ensure that the laser stripping has a large reaction cross section, for example, the maximum reaction cross section corresponds to a laser wavelength of 830nm. By adjusting the laser single pulse energy>100mJ, the laser focus size is less than 1 / 5RMS beam size, and the Rayleigh length is greater than 3 times the RMS beam size, the negative hydrogen H in the laser and beam interaction area - The stripping probability can also reach more than 90%. The laser transmission line 3' can be transmitted by a reflector atmosphere or by an optical fiber.

[0062] The Rayleigh length represents the range in which the Gaussian beam maintains approximately collimated propagation near the beam waist. Within this range, the wavefront curvature of the beam is small and can be regarded as parallel light propagation.

[0063] It should be noted that in order to ensure that the laser beam can be stably and efficiently transmitted to the target position, the laser transmission efficiency must be maintained at a high level as much as possible, and the interaction position between the laser and the beam must be kept stable. The present invention uses a high-reflection mirror to precisely adjust the laser transmission path, thereby effectively reducing the loss during laser transmission. The angle and position of the reflector are precisely controlled by the scanning drive unit 2 to ensure that the target position jitter is less than 1 / 5RMS spot size during laser beam transmission, ensuring high-precision alignment of the laser beam and the beam.

[0064] Exemplarily, a high-precision stepping motor ( Figure 1 and Figure 2 (not shown) to achieve laser beam scanning along the horizontal direction X and the vertical direction Y. Figure 3The scanning drive unit 2 may include a switching reflector 4, a scanning reflector 5 and a focusing mirror 6. The scanning reflector 5 includes a vertical reflector 51 and a horizontal scanning reflector 52. The focusing mirror 6 includes a vertical focusing mirror 61 and a horizontal focusing mirror 62. The vertical scanning reflector 51 and the vertical focusing mirror 61 are located on the vertical Y optical path, and the horizontal scanning reflector 52 and the horizontal focusing mirror 62 are located on the horizontal X optical path. The switching reflector 4 is used to switch the laser transmission along the horizontal optical path or the vertical optical path. The vertical Y optical path refers to the laser acting on the beam along the Y direction, and the horizontal X optical path refers to the laser acting on the beam along the X direction.

[0065] It should be noted that the function of the focusing mirror 6 is to reduce the thickness of the laser along the scanning direction to achieve a higher resolution.

[0066] Specifically, refer to Figure 3 When the processor controls the switching reflector 4 to switch the laser S along the vertical direction Y optical path, the switching reflector 4 moves out of the laser S and X direction path, the laser S is reflected by the vertical scanning reflector 51, and is focused by the vertical focusing mirror 61 before acting on the beam cross section. When the processor controls the switching reflector 4 to switch the laser S along the horizontal direction X optical path, the laser S is reflected by the reflector 4, reflected by the horizontal scanning reflector 52, and is focused by the horizontal focusing mirror 62 before acting on the beam cross section.

[0067] The processor 1 controls the high-precision stepper motor of the scanning drive unit 2 to drive the vertical scanning reflector 51 to move along the X direction to scan the beam in the horizontal direction, and drives the horizontal scanning reflector 52 to move along the Y direction to scan the beam in the S vertical direction. The high-precision stepper motor provided in the embodiment of the present application is matched with a high-precision grating ruler to ensure that the displacement accuracy of the scanning reflector can meet the detection requirements. In particular, the scanning drive unit 2 can also include a high-stability displacement stage, and the repeatability positioning accuracy of the displacement stage is required to be one order of magnitude lower than the laser focusing spot, and the repeatability positioning accuracy is usually ≤20 microns, so that the accurate adjustment of the relative position of the laser and the beam can be guaranteed.

[0068] Figure 4 Schematic diagram of the stripping electron collection module in the negative hydrogen accelerator beam current measurement device provided by the present invention. Figure 1 , Figure 2 and Figure 4 As shown, the stripping electron collection module 20 includes a sector-shaped deflection magnet 7 and a stripping electron collector 7 b , and the stripping electron collector 7 b includes a power supply 8 , a Faraday cage 9 , a signal amplifier 10 and a data acquisition unit 11 .

[0069] The power supply 8 is used to supply power to the sector deflection magnet 7 , the Faraday cage 9 is used to collect stripping electrons and generate stripping electron signals, the signal amplifier 10 is respectively connected to the Faraday cage 9 and the data acquisition unit 11 , and the data acquisition unit 11 is connected to the processor 1 .

[0070] It should be noted that the design of the sector-shaped deflection magnet 7 in the present invention can effectively deflect the stripping electron beam generated after laser stripping to the Faraday cage 9 collector, while avoiding excessive impact on the beam itself.

[0071] Specifically, the stripping electrons enter the stripping electron collection module 20, are deflected by the fan-shaped deflection magnet 7, and are collected by the Faraday cage 9, generating a stripping electron signal, which is then amplified by the signal amplifier 10, and transmitted to the processor 1 after being collected by the first data acquisition unit 11. The processor 1 analyzes and processes the stripping electron signal, and draws the horizontal profile of the beam and / or the vertical profile of the beam in combination with the position of the scanning mirror 5. Among them, there is a corresponding relationship between the interaction position of the laser and the beam and the position of the scanning mirror 5. The processor 1 of the embodiment of the present application pre-tests and stores the position of the scanning mirror 5 and its corresponding interaction position of the laser and the beam.

[0072] Figure 5 is a schematic diagram of the structure of the neutral hydrogen detection module of the negative hydrogen accelerator beam measurement device provided by the present invention. Figure 1 , Figure 2 and Figure 5 The neutral hydrogen detection module 30 includes a separation magnet 13, H 0 The detector 12, the signal amplifier 10 and the data acquisition unit 11. The separation magnet 13 is used to separate the negative hydrogen H - 、Neutral hydrogen H 0 、orthohydrogen H + Separate and transmit in different directions. 0 The material of the detector 12 can be diamond, silicon carbide or low-gain avalanche silicon. 0 The detector 12 is used to collect neutral hydrogen and generate an electrical signal. The signal amplifier 10 is also used to 0 Detector 12 is connected.

[0073] It should be noted that the laser pulse duration (half-maximum width) in the exemplary embodiment of the present invention can be of the order of 10 nanoseconds, and its repetition frequency can be adjusted, ranging from 1 Hz to 10 Hz. In order to achieve the temporal overlap of the laser and the negative hydrogen bunch, it is required to precisely control the laser arrival time, for example, to control the arrival time jitter to <1 ns, so as to ensure that the stripped electrons and H 0 Signal stability.

[0074] Specifically, refer to Figure 5 , neutral hydrogen H 0 The sub-bunches are separated by the separation magnet 13 and H 0 The detector 12 collects and generates electrical signals, which are then amplified by the signal amplifier 10 and collected by the data acquisition unit 11 before being transmitted to the processor 1. The processor 1 analyzes and processes the electrical signals, and plots the horizontal phase space distribution of the beam and / or the vertical phase space distribution of the beam in combination with the position of the scanning mirror 5.

[0075] The stripping electron collection module 20 and the neutral hydrogen detection module 30 may share a signal amplifier 10 and a data acquisition unit 11 .

[0076] Based on the same inventive concept, an embodiment of the present invention further provides a method for measuring a negative hydrogen accelerator beam current based on laser stripping, and uses the negative hydrogen accelerator beam current measuring device based on laser stripping provided in the above embodiment to perform online beam current measurement. Figure 5 This is a schematic diagram of a negative hydrogen accelerator beam current measurement method based on laser stripping provided by the present invention, with reference to Figure 1-Figure 3 As shown, the negative hydrogen accelerator beam current measurement method based on laser stripping includes the following specific steps:

[0077] S101, the processor controls the laser module to output laser, and controls the laser to scan the beam output by the accelerator along the first direction, and the laser and the beam interact in the vacuum chamber to strip the beam from H 0 The electrons are clustered and stripped.

[0078] Specifically, the processor controls the laser module 10 to output a laser beam S to scan the beam H in the vacuum chamber in a horizontal or vertical direction. - , laser S and beam H - The interaction undergoes a laser stripping reaction, generating stripping electrons e - , stripping electrons - With the beam current H - The forward direction enters the stripping electron collection module 20 .

[0079] S102, the processor controls the stripping electron collection module to collect stripping electrons and generate stripping electron signals, and obtains the beam profile based on the interaction position between the laser and the beam and the stripping electron signals.

[0080] Specifically, refer to Figure 2 The processor controls the scanning drive system of the laser module 10 so that the laser S scans the beam H in the vacuum chamber along the horizontal direction X or the vertical direction Y. - , laser S and beam H - The laser stripping reaction produces stripping electrons e -At each laser scanning position, the processor controls the stripping electron collection module 20 to collect the stripping electrons e - , and based on the stripping of electrons - Generate electrical signal output, establish laser S and beam H - The mapping relationship between the interaction position and the stripping electron signal intensity is transmitted to the processor 1. The processor 1 calculates the mapping relationship between the laser S and the beam H. - The mapping relationship between the interaction position and the intensity of the stripped electron signal is used to draw the horizontal profile of the beam and / or the vertical profile of the beam, so as to realize the online real-time measurement of the beam profile. The interaction time between the laser and the beam is extremely short, only in the order of picoseconds to nanoseconds, and the influence of the detection equipment on the beam itself is almost negligible. Therefore, this method can realize the real-time online monitoring of the accelerator beam without interfering with the stability of the beam or the normal operation of the accelerator.

[0081] S103, the processor controls the neutral hydrogen detection module to detect neutral hydrogen H 0 The sub-bunch is formed and a sub-bunch angle distribution signal is generated, and the beam phase space distribution is obtained based on the interaction position between the laser and the beam and the sub-bunch angle distribution signal.

[0082] Specifically, the neutral hydrogen detection module 30 is arranged at the rear end of the laser stripping reaction. At each laser scanning position, the processor controls the neutral hydrogen detection module 30 to collect neutral hydrogen H 0 The neutral hydrogen detection module 30 is based on the neutral hydrogen H 0 The sub-bunches generate the sub-bunch angle distribution signal, and the laser S and beam current H are established by combining the sub-bunch drift length information. - The mapping relationship between the interaction position and the beamlet angular distribution is transmitted to the processor, and the processor calculates the mapping relationship based on the laser S and the beam current H. - The mapping relationship between the interaction position and the beamlet angular distribution is used to obtain the horizontal phase space distribution of the beam and / or the vertical phase space distribution of the beam.

[0083] S104. The processor determines the root mean square emittance of the beam by using an adaptive ellipse exclusion method according to the phase space distribution of the beam, and determines the emittance of the beam by using an ellipse exclusion method.

[0084] It should be noted that the processor can use an adaptive ellipse exclusion method to determine the root mean square emittance of the beam. Specifically, an ellipse with the same eccentricity and slope and an area from small to large can be set, and the distribution inside the ellipse after deducting the mean value of the distribution outside the ellipse is taken to calculate the emittance. When the area of ​​the ellipse increases to a size close to the boundary between the useful signal and the noise interference signal, the rate of change of the emittance with the area of ​​the ellipse approaches zero, and the emittance at this time is taken as the root mean square emittance of the beam. The ellipse exclusion method can also be used to analyze the valid data of the signal provided in the above embodiment after noise processing, and an ellipse with the same eccentricity and slope can be set. If the measured particles contained in the ellipse at this time account for 95%, the 95% emittance can be calculated at this time.

[0085] The advantages of the negative hydrogen accelerator beam measurement method based on laser stripping provided in the embodiment of the present application are:

[0086] 1. The embodiment of the present application adopts a non-intercepting beam detection method. The beam detection process does not require any material medium. The laser directly interacts with the beam in a vacuum environment, which fundamentally avoids phenomena such as sputtering, shedding or melting of the target material that may occur in traditional intercepting beam measurements, effectively eliminates the risk of vacuum environment contamination, and ensures the cleanliness and long-term reliability of the accelerator vacuum system.

[0087] 2. The laser beam detection technology is used in the embodiment of the present application. The laser can be introduced into the vacuum chamber through the vacuum observation window for beam detection, without the need to install complex mechanical components in the vacuum chamber. This design simplifies the equipment structure, reduces the difficulty of installation and maintenance, and effectively reduces the risk of system failure caused by mechanical devices.

[0088] 3. In the embodiment of the present application, a pulsed laser, such as a nanosecond laser, is used. The interaction time between the laser and the beam is extremely short, only a few nanoseconds, and the effect of the detection device on the beam itself is almost negligible. Therefore, this method can realize real-time online monitoring of the accelerator beam without interfering with the stability of the beam or the normal operation of the accelerator.

[0089] 4. In the embodiment of the present application, by controlling the time when the laser acts on the bunch, the profile and emittance of the bunch at different longitudinal positions (nanosecond resolution) can be detected, thereby realizing the detection of the dynamic evolution of the beam distribution within the pulse.

[0090] Based on the above embodiment, the laser-beam interaction position to H 0 The distance L of the detector 12 satisfies H 0 The size of the sub-beam bunch on the detection screen of the detector 12 is larger than the size of the laser focus spot.

[0091] It should be noted that the laser beam interaction position to H 0The distance L between the semiconductor strips of the detector 12 satisfies that the size of the sub-bunch on the screen is much larger than the size of the laser focus spot. Such a design can accurately reconstruct the distribution of the divergence angle of the sub-bunch.

[0092] Furthermore, H 0 Detector 12 is a semiconductor strip detector. Downstream neutral hydrogen sub-bunch observation adopts semiconductor detector imaging. In order to improve imaging resolution and larger field of view, the beam is incident perpendicular to the detection screen, that is, the semiconductor detection screen is set to be perpendicular to the direction of the beam, and the semiconductor detection screen should be resistant to radiation.

[0093] Based on the above embodiments, Figure 2 , Figure 3 , Figure 4 The embodiment of the present application adopts the negative hydrogen accelerator beam measurement device based on laser stripping provided in the above embodiment to perform online beam profile measurement, and the specific steps are as follows:

[0094] S11, initialize the laser module, stripping electron collection module and neutral hydrogen detection module.

[0095] Specifically, refer to Figure 2 Initialize the laser trigger program in the laser module 10, the driver program for the reflector scanning in the scanning drive unit 2 and the data acquisition program of the processor 1, start the driving power supply 8 of the sector deflection magnet 7. Initialize the Faraday cup 9, the signal amplifier 10 and the data acquisition unit 11 in the stripping electron collection module 20, initialize the H in the neutral hydrogen detection module 30. 0 Detector 12.

[0096] S12. The processor controls the scanning range, scanning step length and moving speed of the scanning reflector.

[0097] Specifically, refer to Figure 3 The processor 1 pre-sets the scanning range ((Δx min ,Δx max ), scanning step length d x and moving speed, the processor pre-sets the scanning range (Δy min ,Δy max ), scanning step length dy) and moving speed. Among them, (Δx min , is the scanning starting position of the vertical scanning reflector 51 along the horizontal direction X, Δx max is the scanning cut-off position of the vertical scanning reflector 51 along the horizontal direction X, Δy min is the scanning starting position of the horizontal scanning mirror 52 along the vertical direction Y, Δy max is the scanning cut-off position of the horizontal scanning mirror 52 along the vertical direction Y, dx is the preset scanning step length of the horizontal scanning reflection mirror 51 along the horizontal direction X. dy) is the preset scanning step length of the horizontal scanning reflection mirror 52 along the vertical direction Y.

[0098] It should be noted that the present invention uses a high-precision scanning mirror to precisely adjust the laser transmission path and the position of the laser scanning mirror, which can effectively reduce the loss during laser transmission. By precisely controlling the angle and position of the mirror, it is ensured that the target position jitter is less than 1 / 5RMS spot size during laser beam transmission, and high-precision alignment of the laser beam and the beam is achieved. The laser beam can be incident from the vertical direction Y and the horizontal direction X to meet different experimental requirements. Through this design, the profile and emittance of the laser beam in the horizontal direction X or the vertical direction Y can be measured respectively.

[0099] S13, the processor controls the scanning reflector to move along the first direction so that the focal point of the laser is located at the center of the beam, adjusts the focusing mirror along the optical axis direction of the laser, records the intensity of the stripping electron signal collected at different focusing positions, and sets the focusing mirror to the focusing position corresponding to the maximum intensity of the stripping electron signal.

[0100] S14, controlling the scanning reflector to move to each scanning position in sequence along the first direction according to a preset scanning step length, using a stripping electron collector to obtain a stripping electron signal, and plotting a beam profile using each scanning position as the horizontal coordinate and the stripping electron signal intensity as the vertical coordinate.

[0101] Specifically, refer to Figure 2-Figure 4 The processor 1 controls the high-precision stepper motor to move the position of the reflector 4 to switch the laser to vertical transmission, and at the same time controls the high-precision stepper motor to move the vertical scanning reflector 51 to make the laser focus point to the center of the beam, adjust the position of the vertical focusing mirror 61 along the laser optical axis, record the intensity of the electron signal collected at different focusing positions, and keep the focusing position of the beam vertical focusing mirror 61 at the position where the number of electrons after stripping is the largest.

[0102] The scanning positions of the vertical scanning reflector 51 along the horizontal direction X are Δx i (i=2,3,4,...M),M=(Δx max -Δx min ) / dx,Δx 2 It refers to the first scanning position of the vertical scanning reflector 51 along the horizontal direction X. i≥2, M is a positive integer.

[0103] Furthermore, the processor controls the high-precision stepper motor to move the vertical scanning mirror 51 to each scanning position Δx i (i=2,3,4,...M), obtain the electron signal from the stripping electron collector 7b, and scan at each position Δxi (i=2,3,4,...M) is the horizontal coordinate, and each scanning position Δx i The stripping electron signal intensity corresponding to (i=2,3,4,...M) is used as the ordinate, and the horizontal profile of the beam is plotted.

[0104] Furthermore, the processor controls the high-precision stepper motor to move the position of the reflector 4 to switch the laser to horizontal transmission. At the same time, the high-precision stepper motor is controlled to move the horizontal scanning reflector 52 to make the laser focus point to the center of the beam, adjust the position of the horizontal focusing mirror 62 along the laser optical axis, and record the intensity of the electron signal collected at different focusing positions, and keep the focusing position of the beam horizontal focusing mirror 62 at the position where the number of electrons after stripping is the largest.

[0105] The scanning positions of the horizontal scanning mirror 52 along the vertical direction Y are Δy j (j=2,3,4,...N), N=(Δy max -Δy min ) / dy,ΔY 2 It refers to the first scanning position of the horizontal scanning reflector 52 along the vertical direction Y. j≥2, N is a positive integer.

[0106] Furthermore, the processor controls the high-precision stepper motor to move the horizontal scanning mirror 52 to each scanning position Δy j (j=2,3,4,...N), obtain the electron signal from the stripping electron collector 7b, and scan at each position Δy j (j=2,3,4,...N) is the horizontal coordinate, and each scanning position Δy j The electron signal intensity corresponding to (j=2,3,4,...N) is used as the ordinate, and the vertical profile of the beam is plotted.

[0107] Based on the above embodiments, Figure 2 , Figure 3 , Figure 5 The embodiment of the present application adopts the negative hydrogen accelerator beam measurement device based on laser stripping provided in the above embodiment to perform online beam divergence measurement, and the specific steps are as follows:

[0108] S21, initializing the laser module, the stripping electron collection module and the neutral hydrogen detection module.

[0109] Specifically, refer to Figure 2-Figure 5Initialize the laser trigger program in the laser module 10, the driver program for the reflector scanning in the scanning drive unit 2 and the data acquisition program of the processor 1, start the driving power supply 8 of the sector deflection magnet 7. Initialize the Faraday cup 9, the signal amplifier 10 and the data acquisition unit 11 in the stripping electron collection module 20, initialize the H in the neutral hydrogen detection module 30. 0 Detector 12, H 0 The detector 12 is moved to the center of the beam vacuum pipe, and the power supply 8 is turned on to respectively move the fan-shaped deflection magnets 7 and H 0 The detector 12 is powered.

[0110] S22. The processor controls the scanning range, scanning step length and moving speed of the scanning reflector.

[0111] In the present application, the first direction at least includes a horizontal direction X and a vertical direction Y, taking the acquisition of the phase space distribution of the beam in the horizontal direction and the phase space distribution of the beam in the vertical direction as an example.

[0112] Specifically, refer to Figure 2 and Figure 3 The above embodiment of the processor 1 provides a method for setting the scanning range, scanning step and moving speed of the laser, which will not be repeated here.

[0113] S23, the processor controls the switching position of the reflector 4 to switch the laser light path to a horizontal light path.

[0114] Specifically, refer to Figure 2-Figure 3 The processor 1 controls the high-precision stepper motor to move the position of the reflector 4 to switch the laser to the vertical direction for transmission. After the laser S passes through the reflector 4, it is reflected by the vertical scanning reflector 51 and focused into a beam by the vertical focusing mirror 61.

[0115] S24, the processor controls the vertical scanning reflector 51 to move in the horizontal direction so that the focal point of the laser is located at the center of the beam, adjusts the vertical focusing mirror 61 along the optical axis direction of the laser, records the stripping electron signal intensity collected at different focusing positions, and sets the vertical focusing mirror 61 to the position corresponding to the maximum stripping electron signal intensity.

[0116] S25, the processor controls the high-precision stepping motor to move the vertical scanning reflector 51 to the scanning position Δx i .

[0117] S26, processor control H 0 The detector collects neutral hydrogen H after drifting a preset distance L 0 The sub-bunch is generated and the sub-bunch angle distribution signal is generated according to H 0 The size of the beamlet angular distribution signal collected by the detector determines the projection distribution of the beamlet in the horizontal direction δ(Δx i).

[0118] Specifically, the bunch drifts a preset distance L and then bombards H 0 Detector, processor according to H 0 The signal size of the semiconductor strip in the detector determines the projection distribution δ(Δx i ).

[0119] Where, the laser-beam interaction position to H 0 The preset distance L of the detector semiconductor strips satisfies that the size of the sub-bunch on the screen is much larger than the size of the laser focus spot, so as to accurately reconstruct the divergence angle distribution of the sub-bunch.

[0120] S27. The processor calculates the divergence angle distribution corresponding to the position where the laser interacts with the beam according to the linear beam transmission theory, and establishes the transformation relationship between the sub-beam and the corresponding divergence angle distribution: ρ(Δx i )=δ(Δx i ) / L.

[0121] Specifically, the processor calculates the vertical scanning mirror 51 at the scanning position Δx according to the linear beam transmission theory. i Under the optical path condition, the divergence angle distribution corresponding to the position where the laser interacts with the beam, and the scanning position Δx is recorded i The transformation relationship between the obtained sub-bunch and the corresponding divergence angle distribution is: ρ(Δx i )=δ(Δx i ) / L.

[0122] S28, the processor controls the vertical scanning reflector 51 to scan along the horizontal direction X according to the preset scanning step length d x Move to each scanning position Δx in sequence i , and obtain each scanning position Δx i The corresponding divergence angle distribution is used to establish the horizontal phase space distribution of the beam I(Δx, x′).

[0123] Specifically, the processor 1 controls the high-precision stepping motor to move the vertical direction reflector 51 to each scanning position Δx i (i=2,3,4,...M), repeat steps S24 to S28 to obtain multiple scanning positions Δx i The corresponding divergence angle distribution is based on the vertical direction of the reflector 51 at each scanning position Δx i is the horizontal axis, and its various scanning positions Δx i The corresponding divergence angle distribution is the ordinate, and the horizontal phase space distribution of the beam I(x, x′) is obtained by plotting it.

[0124] S29, the processor controls the switching position of the reflector 4 to switch the laser light path to a vertical direction light path.

[0125] Specifically, refer to Figure 2-Figure 3 The processor 1 controls the high-precision stepper motor to move the position of the reflector 4 to switch the laser to horizontal transmission. The laser S is reflected by the reflector 4 and the horizontal scanning reflector 52 in turn, and is focused into a beam by the horizontal focusing mirror 62.

[0126] S210, the processor controls the horizontal scanning reflector 52 to move in the vertical direction so that the focal point of the laser is located at the center of the beam, adjusts the horizontal focusing mirror 62 along the optical axis direction of the laser, records the stripping electron signal intensity collected at different focusing positions, and sets the horizontal focusing mirror 62 at the position corresponding to the maximum stripping electron signal intensity.

[0127] S211, the processor controls the high-precision stepping motor to move the horizontal scanning reflector 52 to the scanning position Δy i .

[0128] S212, processor control H 0 The detector collects neutral hydrogen H after drifting a preset distance L 0 The sub-bunch is generated and the sub-bunch angle distribution signal is generated according to H 0 The size of the beamlet angular distribution signal collected by the detector determines the vertical projection distribution δ(Δy j ).

[0129] Specifically, the bunch drifts a preset distance L and then bombards H 0 Detector, processor according to H 0 The signal size of the semiconductor strip in the detector determines the projection distribution δ(Δy j ).

[0130] Where, the laser-beam interaction position to H 0 The preset distance L of the detector semiconductor strips satisfies that the size of the sub-bunch on the screen is much larger than the size of the laser focus spot, so as to accurately reconstruct the divergence angle distribution of the sub-bunch.

[0131] S213, the processor calculates the divergence angle distribution corresponding to the position where the laser interacts with the beam according to the linear beam transmission theory, and establishes the transformation relationship between the sub-beam and the corresponding divergence angle distribution: ρ(Δy j )=δ(Δy j ) / L.

[0132] Specifically, the processor calculates the horizontal scanning mirror 52 at the scanning position Δy according to the linear beam transmission theory. i Under the optical path condition, the divergence angle distribution corresponding to the position where the laser interacts with the beam, and the scanning position Δy is recorded i The transformation relationship between the obtained sub-bunch and the corresponding divergence angle distribution is: ρ(Δyj )=δ(Δy j ) / L.

[0133] S214, the processor controls the scanning horizontal scanning reflector 52 to scan along the vertical direction according to the preset scanning step length d y Move to each scanning position Δy in sequence i , obtain each scanning position Δy i The corresponding divergence angle distribution is used to establish the horizontal phase space distribution of the beam I(y, y′).

[0134] Specifically, the processor 1 controls the high-precision stepper motor to move the horizontal scanning reflector 52 to each scanning position Δy j (j=2, 3, 4, ... N), repeat steps S29 to S214 to obtain multiple scanning positions Δy i The corresponding divergence angle distribution is based on the horizontal scanning mirror 52 at each scanning position Δy i is the horizontal axis, and each scanning position Δy i The corresponding divergence angle distribution is the ordinate, and the vertical phase space distribution of the beam I(y, y′) is obtained by plotting.

[0135] S215. The processor determines the root mean square emittance of the beam using the adaptive ellipse elimination method based on the obtained horizontal phase space distribution I(x, x′) and vertical phase space distribution I(y, y′) of the beam. Set ellipses with the same eccentricity and slope and areas from small to large, and calculate the emittance by taking the distribution inside the ellipse after deducting the mean value of the distribution outside the ellipse. When the area of ​​the ellipse increases to the size close to the boundary between the useful signal and the noise interference signal, the rate of change of the emittance with the area of ​​the ellipse approaches zero, and the emittance at this time is taken as the root mean square emittance of the beam.

[0136] S216. The processor analyzes the valid data after noise processing using the ellipse elimination method based on the acquired horizontal phase space distribution I(x, x′) and vertical phase space distribution I(y, y′) of the beam, sets an ellipse with the same eccentricity and slope, and the ellipse contains 95% of the measured particles. At this time, the 95% emittance can be calculated.

[0137] In summary, the above embodiment provides a negative hydrogen accelerator beam measurement method based on laser stripping, which adopts a new laser stripping technology. Without using a solid medium, the focused laser filament and the stripping electron collection module are used to perform real-time online measurement of the beam profile, and the laser filament and the neutral hydrogen detection module are used to perform real-time online measurement of the emittance. It can take into account the normal beam supply and detection of the accelerator at the same time, and can accurately evaluate the beam quality of the accelerator and ensure the stable operation of the accelerator.

[0138] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A negative hydrogen accelerator beam current measurement device based on laser stripping, characterized in that: include: A laser module is used to output a laser, wherein the laser scans the beam output by the accelerator along a first direction, wherein the laser interacts with the beam in the vacuum chamber to strip the neutral hydrogen H from the beam. 0 Sub-bunches are formed and stripped electrons are generated; wherein the first direction is parallel to the beam forward tangent plane, and the first direction includes a vertical direction and a horizontal direction; A stripping electron collection module, used for collecting the stripping electrons and generating a stripping electron signal; A neutral hydrogen detection module is used to detect the neutral hydrogen H 0 sub-bunch and generate a sub-bunch angular distribution signal; At least one processor is used to obtain a beam profile based on an interaction position between the laser and the beam and the stripping electron signal; to obtain a beam phase space distribution based on an interaction position between the laser and the beam and the sub-beam bunch angle distribution signal; and to determine the root mean square emittance of the beam using an adaptive ellipse exclusion method and the emittance of the beam using an ellipse exclusion method according to the beam phase space distribution.

2. The negative hydrogen accelerator beam current measurement device according to claim 1, characterized in that: The laser module includes a laser, a laser transmission line and a scanning drive unit; The processor is used to control the scanning driving unit to scan the laser beam along the first direction, and is also used to control the scanning range, scanning speed and scanning step length of the laser.

3. The negative hydrogen accelerator beam current measurement device according to claim 2, characterized in that: The scanning driving unit includes a switching reflector, a scanning reflector and a focusing mirror; the scanning reflector includes a vertical scanning reflector and a horizontal scanning reflector; the focusing mirror includes a vertical focusing mirror and a horizontal focusing mirror; The vertical scanning reflector and the vertical focusing mirror are located on the vertical optical path, and the horizontal scanning reflector and the horizontal focusing mirror are located on the horizontal optical path; The switching reflector is used to switch the laser to be transmitted along a horizontal optical path or a vertical optical path.

4. The negative hydrogen accelerator beam current measurement device according to claim 1, characterized in that: The stripping electron collection module includes a sector-shaped deflection magnet and a stripping electron collector, and the stripping electron collector includes a power supply, a Faraday cup, a signal amplifier and a data acquisition unit; The power supply is used to supply power to the sector-shaped deflection magnet; the Faraday cup is used to collect stripping electrons and generate stripping electron signals; the signal amplifier is connected to the Faraday cup and the data acquisition unit respectively, and the data acquisition unit is connected to the processor.

5. The negative hydrogen accelerator beam current measurement device according to claim 4, characterized in that: The beam includes neutral hydrogen, and the neutral hydrogen detection module includes a separation magnet, H 0 detector, the signal amplifier and the data acquisition unit; the H 0 The detector is used to collect neutral hydrogen and generate an electrical signal. The signal amplifier is also used to 0 Detector connections.

6. The negative hydrogen accelerator beam current measurement device according to claim 5, characterized in that: The laser and beam interaction position to the H 0 The preset distance L of the detector 12 satisfies the H 0 The size of the sub-bunch on the detector detection screen is larger than the laser focusing spot size.

7. A method for measuring the beam current of a negative hydrogen accelerator based on laser stripping, using the negative hydrogen accelerator beam current measurement device based on laser stripping according to any one of claims 1 to 6 to perform online beam current measurement, characterized in that: The measuring method comprises: The processor controls the laser module to output laser light, and controls the laser light to scan the beam output by the accelerator along a first direction. The laser light interacts with the beam light in the vacuum chamber to strip the H out of the beam light. 0 sub-bunches and produces stripped electrons; wherein the first direction is parallel to the beam forward tangent plane; the first direction includes a vertical direction and a horizontal direction; The processor controls the stripping electron collection module to collect the stripping electrons and generate a stripping electron signal, and obtains a beam profile based on the interaction position between the laser and the beam and the stripping electron signal; The processor controls the neutral hydrogen detection module to detect the neutral hydrogen H 0 sub-bunches and generating a sub-bunch angle distribution signal, and obtaining a beam phase space distribution based on the interaction position between the laser and the beam and the sub-bunch angle distribution signal; The processor determines the root mean square emittance of the beam by using an adaptive ellipse exclusion method according to the phase space distribution of the beam, and determines the emittance of the beam by using an ellipse exclusion method.

8. The method for measuring the negative hydrogen accelerator beam according to claim 7, characterized in that: The laser module includes a laser, a laser transmission line and a scanning drive unit; the scanning drive unit includes a switching reflector, a scanning reflector and a focusing mirror; before controlling the laser module to output laser, it also includes: Initialize the laser module, stripping electron collection module, and neutral hydrogen detection module; The processor controls the scanning range, scanning step length and moving speed of the scanning reflector; The processor controls the scanning reflector to move along the first direction so that the focal point of the laser is located at the center of the beam, and adjusts the focusing mirror along the optical axis direction of the laser; controls the electron collection module to record the stripping electron signal intensity collected at different focusing positions, and sets the focusing mirror to the focusing position corresponding to the maximum stripping electron signal intensity.

9. The method for measuring the negative hydrogen accelerator beam according to claim 7, characterized in that: The stripping electron collection module includes a sector-shaped deflection magnet and a stripping electron collector; the step of obtaining a beam profile includes: The processor controls the scanning mirror to move to each scanning position in sequence along the first direction according to a preset scanning step length, controls the stripping electron collector to obtain the stripping electron signal, and draws the beam profile with each scanning position as the horizontal coordinate and the stripping electron signal intensity as the vertical coordinate.

10. The method for measuring the negative hydrogen accelerator beam according to claim 9, characterized in that: The neutral hydrogen detection module includes H 0 The steps of obtaining the beam phase space distribution include: The processor controls the H 0 The detector collects the neutral hydrogen H after drifting a preset distance. 0 The sub-bunch generates the sub-bunch angle distribution signal according to H 0 The projection distribution of the sub-bunch in the first direction is determined based on the size of the sub-bunch angular distribution signal collected by the detector; The processor calculates the divergence angle distribution corresponding to the position where the laser interacts with the beam according to the linear beam transmission theory, and establishes a transformation relationship between the sub-beam bunch and the corresponding divergence angle distribution; The processor controls the scanning reflector 5 to move to each scanning position in sequence along the first direction according to a preset scanning step length, obtains the divergence angle distribution corresponding to each scanning position, and establishes the beam phase space distribution.

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