A longitudinal bunch measurement device and method based on residual gas ionization

Abstract

The application relates to a longitudinal bunch measurement device and method based on residual gas ionization, which comprises the following parts: a high-voltage electrostatic field part for providing a uniform high-voltage electrostatic field for moving signal particles to a detection end; a micro-channel plate (MCP) arranged at the front end of a microstrip line PCB board and a coaxial tapered cone respectively, for carrying out avalanche amplification on the collected signal particles; the microstrip line PCB board is used for collecting signal particles of a first bandwidth; the coaxial tapered cone is used for collecting signal particles of a second bandwidth; the first bandwidth is higher than the second bandwidth; the microstrip line PCB board and the coaxial tapered cone are located at opposite ends of the high-voltage electrostatic field part; an oscilloscope is connected with the microstrip line PCB board and the coaxial tapered cone respectively, and is used for processing and displaying the signal particles collected by the microstrip line PCB board and the coaxial tapered cone. The application has the characteristics of non-interception measurement and belongs to the particle detection mechanism, and can realize the measurement of a bunch length of tens of picoseconds, so as to meet the measurement of a high dynamic range bunch length of a high-power accelerator.

Description

Technical Field

[0001] This invention relates to a longitudinal bundle measurement device and method based on residual gas ionization, belonging to the field of heavy ion accelerator beam diagnostic technology. Background Technology

[0002] With the development trend of high-power ion accelerators, physicists urgently need to monitor various beam parameters in real time, such as energy, flux, emittance, transverse profile, and bundle length. In the medium-energy transport line (MEBT) of a superconducting linear accelerator, accurate measurement of the bundle length is crucial for the functional evaluation and monitoring of the upstream beam gatherer, as well as for longitudinal matching of the beam entering the superconducting cavity and reducing beam loss. In ring synchrotrons and storage rings, real-time monitoring of the bundle length is significant for high-frequency trapping, energy ramping, and harmonic acceleration within the ring. In summary, accurate measurement of the longitudinal bundle length helps optimize lattice parameters and reduce beam loss, ensures the safe and stable operation of the accelerator, and meets potential future machine upgrade needs.

[0003] Bundle length probes can also be categorized into blocking measurement types, such as the Fast Faraday Cylinder (FFC) based on coaxial transmission line structure and high-frequency matching design, and the Bundle Shape Probe (BSM) based on filament-excited secondary electrons and high-frequency deflector structure. Both can achieve extremely high bandwidths, especially the BSM detector, which can achieve ultra-high resolution on the order of approximately ten picoseconds. However, the blocking measurement method limits its application in high-power machines. Non-blocking measurement devices include the commercial magnetic ring product (FCT) from the French company BERGOZ. This product has a bandwidth that is about 1.5 GHz lower than the two probes mentioned above, and it is subject to import embargo risks and is relatively expensive. There is also a wall current detector (WCM) based on the mirror current mechanism. One WCM probe was developed and applied on the cooling storage ring of the Lanzhou Heavy Ion Accelerator (HIRFL-CSR). Its bandwidth is slightly lower, covering only 1.2 kHz to 550 MHz. This is mainly due to the high permeability of the magnetic ring material and the stringent sealing and shielding design, which limit its performance upper limit.

[0004] Both of the above-mentioned non-interceptive bunch length probes (FCT and WCM) can be used for high-power beam measurement, but they share the following characteristics: (1) They are both electromagnetic field induction type (pick-up) probes. When the speed of the proton and heavy ion beams is not close to the speed of light, their electromagnetic field is not a standard transverse electromagnetic wave (TE) mode, but has a significantly leading longitudinal component. This field component will arrive at the probe position ahead of the bunch, resulting in the measured bunch length being broadened. (2) From the simplified circuit analysis of signal processing, the probe can be equivalent to a series and parallel circuit of resistor R, capacitor C and inductor L. It has a certain lower cutoff operating frequency, that is, it cannot measure longer bunch structures. In particular, when the beam passes through a multi-turn injection synchrotron accelerator, its bunch structure will gradually lengthen to form a so-called "coasting beam". This type of pick-up probe is difficult to meet the measurement requirements of coasting beams or longer bunches. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a longitudinal bundle measurement device and method based on residual gas ionization. This device features non-interception measurement and is a particle detection mechanism with no lower cutoff frequency limitation. It has an extremely wide bandwidth operating range of DC-10GHz and can achieve bundle length measurement on the order of tens of picoseconds, thus meeting the high dynamic range bundle length measurement requirements of high-power accelerators.

[0006] To achieve the above objectives, the present invention proposes the following technical solution: a longitudinal bundle measurement device based on residual gas ionization, comprising: a high-voltage electrostatic field section, a microchannel plate (MCP), a microstrip line PCB, a coaxial tapered cone, and an oscilloscope; the high-voltage electrostatic field section is used to provide a uniform high-voltage electrostatic field that causes signal particles to move towards the detection end; the MCP is respectively disposed at the front ends of the microstrip line PCB and the coaxial tapered cone, and is used to avalanche amplify the acquired signal particles; the microstrip line PCB is used to acquire signal particles with a first bandwidth; the coaxial tapered cone is used to acquire signal particles with a second bandwidth; the first bandwidth is higher than the second bandwidth; the microstrip line PCB and the coaxial tapered cone are located at opposite ends of the high-voltage electrostatic field section; the oscilloscope is respectively connected to the microstrip line PCB and the coaxial tapered cone, and is used to process and display the signal particles acquired by the microstrip line PCB and the coaxial tapered cone.

[0007] Furthermore, the signal particles are the ionization products of the charged particles in the beam and the residual gas in the vacuum. The amount of ionization products generated after the beam passes through the residual gas medium is obtained by calculating the average energy loss ΔE of a single particle incident on the residual gas; multiplying the average energy loss ΔE by the longitudinal length L of the observation area, then multiplying it by the average current intensity I0 of the beam, and then dividing it by the average energy consumption W for generating gas ions and electron pairs.

[0008] Furthermore, the formula for calculating the average energy loss ΔE of a single particle incident on the residual gas is as follows:

[0009]

[0010] Where E is the energy of the signal electron, x is the coordinate of the direction of motion of the signal electron, and N... A It is Avogadro's constant, r e It is the classical radius of the electron, m e Let c be the electron's rest mass; c is the speed of light in vacuum; z is the speed of light in vacuum. c For the charge state of the incident particle, ρ t It is the density of the gas medium, Z t A is the atomic number of the medium; t δ is the atomic mass of the medium; β is the ratio of the incident particle velocity to the speed of light; γ is the Lorentz factor; I is the average ionization and excitation energy of the gas; δ / 2 is a density correction factor; and C / Z is the medium shell correction factor.

[0011] Furthermore, the ratio of the impedance in the coaxial tapered cone to the inner and outer diameters of the coaxial structure satisfies the following formula:

[0012]

[0013] Where Z is the characteristic impedance, μ0 is the permeability of the insulating medium between the inner and outer conductors, and ε0 is the dielectric constant of the insulating medium. Since this structure will be used in a target chamber with extremely low pressure in this invention, the insulating medium material is approximated by vacuum parameters, R... s R is the radius of the outer conductor (shielding layer). C It is the radius of the inner conductor (signal layer).

[0014] Furthermore, the high-voltage electrostatic field unit includes a high-voltage supply module, a vertical high-voltage plate, a horizontal high-voltage plate, a supporting ceramic, and a hollow frame. The high-voltage supply module is used to provide a high-voltage signal for the high-voltage electrostatic field. The high-voltage supply module is connected to the vertical high-voltage plate and the horizontal high-voltage plate. The vertical high-voltage plate is perpendicular to the direction of particle motion, and the horizontal high-voltage plate is parallel to the direction of particle motion. The vertical high-voltage plate and the horizontal high-voltage plate are fixed to the hollow frame through the supporting ceramic.

[0015] Furthermore, the two ends of the microchannel plate MCP are connected to the high-voltage supply module. The microchannel plate MCP has a double-layer structure, and high voltage is applied only to the top microchannel plate MCP.

[0016] Furthermore, the measuring device also includes a first signal cable, which comprises a signal cable for a microstrip PCB board and a signal cable for a coaxial tapered cone. One end of the signal cable for the microstrip PCB board is connected to the output end of the microstrip PCB board; the other end of the signal cable for the microstrip PCB board is fixed to a knife-edge flange and connected to a signal feedthrough; one end of the signal cable for the coaxial tapered cone is connected to the inner core of the coaxial tapered cone, and the other end of the signal cable for the coaxial tapered cone is fixed to a knife-edge flange and connected to a signal feedthrough.

[0017] Furthermore, the signal feedthrough is connected to a second signal cable via an SMA adapter, the second signal cable is connected to a power amplifier or attenuator, and the power amplifier or attenuator is connected to the oscilloscope via the second signal cable.

[0018] Furthermore, the measuring device also includes a high-voltage conductor bar, one end of which is connected to a vertical high-voltage plate, a horizontal high-voltage plate, and a microchannel plate. The other end of the high-voltage conductor bar is fixed to a knife-edge flange and connected to a high-voltage feeder, which is connected to a high-voltage supply module.

[0019] This invention also discloses a longitudinal bundle measurement method based on residual gas ionization, which employs the longitudinal bundle measurement device based on residual gas ionization described in any of the above-mentioned methods, comprising the following steps: setting the voltages of the vertical high-voltage plate and the horizontal high-voltage plate, with the high-voltage supply module feeding in the corresponding voltages; if the absolute values ​​of the voltages of the vertical high-voltage plate and the horizontal high-voltage plate are inversely proportional to their distances from the microstrip PCB board, then the ionization products move towards the coaxial tapered cone end and are eventually collected by the coaxial tapered cone end; if the absolute values ​​of the voltages of the vertical high-voltage plate and the horizontal high-voltage plate are directly proportional to their distances from the microstrip PCB board, then the ionization products move towards the microchannel plate (MCP) and are eventually collected by the microchannel plate (MCP).

[0020] The present invention has the following advantages due to the adoption of the above technical solutions:

[0021] 1. This invention features non-interception measurement and belongs to the particle detection mechanism. It has no lower cutoff frequency limitation and has an extremely wide bandwidth operating range of DC-10GHz. It can achieve bundle length measurement on the order of tens of picoseconds to meet the high dynamic range bundle length measurement requirements of high-power accelerators.

[0022] 2. The present invention has a compact structure and two signal collection and detection structures. By changing the direction of the high voltage electric field, either suitable structure can be selected for signal collection. Attached Figure Description

[0023] Figure 1This is a schematic diagram of the principle of a longitudinal bundle measurement device based on residual gas ionization in one embodiment of the present invention. Figure 1 The direction of the middle arrow indicates the direction of electron movement;

[0024] Figure 2 This is a schematic diagram of the longitudinal bundle measurement device based on residual gas ionization in one embodiment of the present invention;

[0025] Figure 3 This is a right view of a longitudinal bundle measurement device based on residual gas ionization in one embodiment of the present invention;

[0026] Figure 4 This is a left view of a longitudinal bundle measurement device based on residual gas ionization in one embodiment of the present invention;

[0027] Figure 5 This is a schematic diagram of a knife-edge flange and its high-voltage feeder and signal feeder in one embodiment of the present invention;

[0028] Figure 6 This is a cross-sectional view of an SMA type adapter structure according to an embodiment of the present invention;

[0029] Figure 7 This is a schematic diagram of the structure of a microstrip PCB board according to an embodiment of the present invention. Figure 7 (a) is a structural diagram of the microstrip PCB board. Figure 7 (b) is a structural diagram of the insulating substrate of the microstrip PCB board;

[0030] Figure 8 This is a graph showing the bandwidth test results of a microstrip line structure PCB board in one embodiment of the present invention.

[0031] Figure label:

[0032] 1-High voltage electrostatic field section; 11-High voltage supply module; 12-Vertical high voltage electrode plate; 13-Horizontal high voltage electrode plate; 14-Support ceramic; 15-High voltage feedthrough; 2-Microchannel plate (MCP); 3-Microstrip PCB board; 4-Coaxial tapered cone; 5-First signal cable; 51-Signal cable of microstrip PCB board; 52-Signal cable of coaxial tapered high voltage supply module with tapered collection cone; 6-Knife-edge flange; 7-Signal feedthrough; 8-SMA type adapter; 9-Second signal cable; 10-High voltage conductor. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in detail through specific embodiments. However, it should be understood that the specific embodiments are provided only for a better understanding of the present invention and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terminology used is for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] To address the problem in existing technologies where the beam structure gradually elongates to form a so-called "coasting beam" after passing through multiple injection loops of a synchrotron accelerator, making it difficult for pick-up probes to meet the measurement requirements of coasting beams or longer beams, this invention aims to provide a longitudinal beam measurement device and method based on residual gas ionization. When charged particles in the beam move or accelerate within the accelerator's vacuum tube, they undergo Coulomb collisions with residual gas, ionizing the gas molecules. Electrons in the ionization products, deflected by a high-voltage electrostatic field, move towards a microchannel plate (MCP) perpendicular to the beam's direction of motion. Signal particles, driven by the electric field, move towards a microstrip PCB. Passing through tiny apertures covered with a special coating on the MCP, they undergo avalanche amplification, and the multiplied electrons are then collected by the extremely high-bandwidth MCP. Signal particles, driven by the electric field, move towards a coaxial graded cone, and after being amplified by the MCP, are collected by the high-bandwidth coaxial graded cone. It features non-interception measurement characteristics and belongs to the particle detection mechanism. It has no lower cutoff frequency limitation and boasts an extremely wide operating bandwidth of DC-10GHz, enabling bundle length measurements on the order of tens of picoseconds to meet the high dynamic range bundle length measurement requirements of high-power accelerators. The invention will now be described in detail below with reference to the accompanying drawings and embodiments.

[0035] Example 1

[0036] This embodiment discloses a longitudinal bundle measurement device based on residual gas ionization, such as... Figure 1 As shown, it includes: a high-voltage electrostatic field section 1, a microchannel plate MCP 2, a microstrip PCB 3, a coaxial tapered cone 4, and an oscilloscope;

[0037] High-voltage electrostatic field unit 1 is configured and installed in the vacuum target chamber to provide a uniform high-voltage electrostatic field that causes signal particles to move toward the detection end;

[0038] The microchannel board MCP2 is respectively set at the front end of the microstrip PCB board 3 and the coaxial tapered cone 4, as shown below. Figure 1As shown, when charged particles in the beam move or accelerate within the accelerator's vacuum tube, they undergo Coulomb collisions with the residual gas, ionizing the gas molecules. Electrons in the ionization products, deflected by a high-voltage electrostatic field, move towards the microchannel plate MCP2, perpendicular to the beam's direction of motion. The microchannel plate MCP2 is used for avalanche amplification of the acquired signal particles. Signal particles are avalanche amplified when they pass through tiny pores covered with a special coating on the microchannel plate MCP2.

[0039] The microstrip PCB board 3 is configured and installed in the vacuum target chamber to collect signal particles with a first bandwidth. In this embodiment, the microstrip PCB board 3 is designed with a 50-ohm characteristic impedance and has an extremely high bandwidth range of DC-10GHz to collect signal electrons multiplied by the microchannel board MCP2.

[0040] A coaxial tapered cone 4 is configured and installed within the vacuum target chamber to collect signal particles with a second bandwidth. In this embodiment, the coaxial tapered cone 4 is designed with a 50-ohm characteristic impedance and a high bandwidth range of DC-5GHz to collect multiplied electrons after passing through the microchannel plate MCP2.

[0041] The first bandwidth is higher than the second bandwidth; the microstrip PCB board 3 and the coaxial gradient cone 4 are located at opposite ends of the high-voltage electrostatic field section 1; in this embodiment, the first bandwidth is an extremely high bandwidth, and the second bandwidth is a relatively high bandwidth. The extremely high bandwidth is approximately 10 GHz, and the relatively high bandwidth is approximately 5 GHz.

[0042] The oscilloscope is connected to the microstrip PCB board 3 and the coaxial tapered cone 4 respectively, and is used to process and display the signal particles collected by the microstrip PCB board 3 and the coaxial tapered cone 4.

[0043] The high-voltage electrostatic field unit 1 includes a high-voltage supply module 11, a vertical high-voltage plate 12, a horizontal high-voltage plate 13, a supporting ceramic 14, and a hollow frame. The high-voltage supply module 11 is used to provide a high-voltage signal for the high-voltage electrostatic field. The high-voltage supply module 11 is connected to the vertical high-voltage plate 12 and the horizontal high-voltage plate 13. The vertical high-voltage plate 12 is perpendicular to the direction of particle motion, and the horizontal high-voltage plate 13 is parallel to the direction of particle motion. The vertical high-voltage plate 12 and the horizontal high-voltage plate 13 are fixed to the hollow frame through the supporting ceramic 14.

[0044] The microchannel board MCP2 is connected to the high-voltage supply module 11 at both ends. The microchannel board MCP2 has a double-layer structure. Due to its compact design with extremely narrow gaps, high voltage is applied only to the top microchannel board MCP2. The rated gain of the double-layer microchannel board MCP2 is approximately 1E6.

[0045] In this embodiment, there will still be a certain amount of residual gas in the accelerator vacuum pipe, which can be estimated using the Clapeyron equation for ideal gases. Taking the cooling storage ring (HIRFL-CSR) of the Lanzhou Heavy Ion Accelerator as an example, let the pressure inside the ring be 5*10-10 Pa; the temperature be 20℃; in the following formula, P is the pressure in Pa; V is the volume in m3; n is the amount of substance; M is the molar mass in g / mol; T is the Kelvin temperature, i.e., Celsius +273.15; and the gas constant R = 8.314*106 Pa·cm3 / (mol·K). After baking inside the ring, the main type of residual gas is hydrogen. Substituting the parameters, the density of the residual gas is calculated to be approximately 4.14E-19 g / cm3. 3 .

[0046]

[0047] The Coulomb collisions between charged particles in the beam and the residual gas ionize the gas. The ionization products are gas ions and electron pairs, and the yield is related to the energy loss during the collision process. It can be approximated by the Bethe formula. Considering the low density of the residual gas inside the accelerator, the last two terms in the formula related to density and shell can be ignored, leaving only the velocity correction term in the second term. For example, at a Pa of 5 × 10⁻¹⁰, a temperature of 20 °C, and a single proton particle incident at 48 MeV, the Bethe formula calculates the energy loss as 1.150E⁻¹⁷ MeV / cm, which is consistent with the 1.136E⁻¹⁷ MeV / cm calculated by the SRIM energy loss program. The formula for calculating the average energy loss ΔE of a single particle incident on the residual gas is:

[0048]

[0049] Where E is the energy of the signal electron, x is the coordinate of the direction of motion of the signal electron, and N... A It is Avogadro's constant, which is 6.022 × 10⁻⁶. 23 r e It is the classical radius of the electron, m e Let c be the rest mass of the electron; c is the speed of light in vacuum, which is 2.998 × 10⁻⁶. 8 m / s, z c For the charge state of the incident particle, ρ t It is a gaseous medium, Z t A represents the atomic number of the gaseous medium; t γ is the atomic mass; β is the ratio of the incident particle velocity to the speed of light; γ is the Lorentz factor; I is the average ionization and excitation energy of the gas; δ / 2 is the density correction factor; and C / Z is the shell correction factor.

[0050] The signal particles are the ionization products of the charged particles in the beam and the residual gas in the vacuum. The amount of ionization products generated after the beam passes through the residual gas medium is obtained by calculating the average energy loss ΔE of a single particle incident on the residual gas; multiplying the average energy loss ΔE by the longitudinal length L of the observation area, then by the average beam intensity I0, and then dividing by the average energy consumption W for generating gas ions and electron pairs.

[0051] like Figure 2 , Figure 3 , Figure 4 As shown, the measuring device also includes a first signal cable 5. The first signal cable 5, according to its connection terminals, may include a signal cable 51 for a microstrip PCB board and a signal cable 52 for a coaxial tapered cone, such as... Figure 5 As shown, one end of the signal cable 51 of the microstrip PCB board is connected to the output end of the microstrip PCB board 3; the other end of the signal cable 51 is fixed to the knife-edge flange 6 and connected to the signal feedthrough 7; one end of the coaxial tapered cone signal cable 52 is connected to the inner core of the coaxial tapered cone 4, and the other end of the coaxial tapered cone signal cable 52 is fixed to the knife-edge flange 6 and connected to the signal feedthrough 7. In this embodiment, the first signal cable 5 is preferably a semi-rigid coaxial cable with a characteristic impedance of approximately 50 ohms and a measured usable bandwidth far exceeding 10 GHz. However, the above features are only illustrative and are not intended to limit the scope.

[0052] The knife-edge flange 6 is configured for vacuum sealing. The outer side of the knife-edge flange 6 is used to isolate the vacuum inside and outside the detector and to carry and support the detector. The exposed knife edge on the inner side of the knife-edge flange 6 can be used to connect to the observation window flange or vacuum silicon flange, etc., so as to observe or monitor the vacuum level.

[0053] The signal feedthrough 7 connects to the second signal cable 9 via an SMA adapter 8. The second signal cable 9 connects to a power amplifier or attenuator, and the power amplifier or attenuator connects to an oscilloscope via the second signal cable 9. In this embodiment, the second signal cable 9 is preferably a semi-rigid coaxial cable with a characteristic impedance of approximately 50 ohms and a measured usable bandwidth far exceeding 10 GHz. However, the above characteristics are for illustrative purposes only and are not intended to be limiting.

[0054] The measuring device also includes a high-voltage conductor 10. One end of the high-voltage conductor 10 is connected to the vertical high-voltage plate 12, the horizontal high-voltage plate 13, and the microchannel plate MCP2. The other end of the high-voltage conductor 10 is fixed to the knife-edge flange 6 and connected to the high-voltage feeder 15. The high-voltage feeder 15 is connected to the high-voltage supply module 11 via an SHV-type high-voltage long cable outside the vacuum. In this embodiment, the high-voltage supply module 11 includes multiple external multi-channel high-voltage power supplies to achieve controllable and precise high-voltage supply to each high-voltage component. In this embodiment, the high-voltage conductor 10 adopts a short-circuit bifurcated type, which merges the high-voltage conductors 10 of the two plates and then combines them into one line to transmit to the high-voltage feeder 15.

[0055] Both the vertical high-voltage plate 12 and the horizontal high-voltage plate 13 are made of metal, preferably stainless steel prepared in an ultra-high vacuum and clean environment in this embodiment. The vertical high-voltage plate 12 is typically a square inscribed plate, configured to establish a high-voltage electrostatic field. Figure 2 As can be seen, there are two vertical high-voltage plates 12. One vertical high-voltage plate 12 is close to the microstrip PCB board 3, and the other vertical high-voltage plate 12 is close to the coaxial gradient cone 4. Several horizontal high-voltage plates 13 are arranged between the two vertical high-voltage plates 12. In this embodiment, the horizontal high-voltage plates 13 are preferably strip-shaped voltage-dividing plates. In this embodiment, four pairs of horizontal high-voltage plates 13 are arranged. Each pair of horizontal high-voltage plates 13 is symmetrically arranged vertically, and the two plates use equal potentials. To save space and cost, they are configured for electrostatic field uniformity and plasticity.

[0056] like Figure 6 As shown, one of the key components of this invention, the coaxial tapered cone 4, needs to meet a characteristic impedance design of close to 50 ohms to achieve high-frequency signal transmission without reflection. The impedance is related to the ratio of the inner and outer diameters of the coaxial structure, which can be evaluated using the following formula: when the vacuum internal impedance is 50 ohms, it is approximately Rc / Rs = 1 / 2.3. The ratio of the impedance in the coaxial tapered cone 4 to the inner and outer diameters of the coaxial structure satisfies the following formula:

[0057]

[0058] Where Z is the characteristic impedance, μ0 is the free permeability, ε0 ​​is the free permittivity, and R is the characteristic impedance. s R is the radius of the outer conductor. C It is the radius of the inner conductor.

[0059] In this embodiment, in order to adapt to the size of the microchannel board MCP2 and maximize the signal collection area, the initial inner core diameter of the coaxial collection cone is preferably designed to be 5mm and the initial outer shell diameter is 11.5mm. Since the higher-order mode TE11 in the coaxial structure is only generated at frequencies higher than 2.998E8 / (2πRs+2πRc), in order to avoid higher-order mode interference, it is calculated that the usable bandwidth frequency of this structure design is approximately 5.78GHz.

[0060] like Figure 7 As shown, the microstrip PCB board 3 also requires a characteristic impedance design of close to 50 ohms, and its impedance Z is related to the dielectric constant ε of the insulating substrate. r The impedance values ​​are related to the dielectric layer thickness H, the metal plating layer thickness T, the plating layer width W, and the frequency f. Furthermore, a key design consideration is ensuring that the impedance value does not vary significantly or deviate too much from 50 ohms within a large bandwidth range f. In this embodiment, Kapton material is preferably used as the insulating substrate, as it possesses strong high and low temperature performance and radiation resistance, and has a relatively low dielectric constant of approximately 3.5. The dielectric thickness is 1.25 mm. The conductor metal is selected as copper-based gold plating, with a thickness of 0.05 mm and a maximum width of 2.8 mm. The impedance calculation results at different frequencies are shown in Table 1.

[0061] Table 1. Impedance calculation results of Kapton material at different frequencies.

[0062] f 0.5GHz 5GHz 10GHz Z 49.58Ω 49.78Ω 50.88Ω

[0063] Example 2

[0064] Based on the same inventive concept, this embodiment also discloses a longitudinal bundle measurement method based on residual gas ionization, which employs any of the longitudinal bundle measurement devices based on residual gas ionization described above, and includes the following steps:

[0065] S1 sets the voltage of the vertical high-voltage plate 12 and the horizontal high-voltage plate 13, and the high-voltage supply module 11 feeds in the corresponding voltage.

[0066] S2 If the absolute values ​​of the voltages of the vertical high-voltage plate 12 and the horizontal high-voltage plate 13 are inversely proportional to their distances from the microstrip PCB board 3, then the ionization products move toward the end of the coaxial tapered cone 4 and are eventually collected by the end of the coaxial tapered cone 4.

[0067] Let the vertical high voltage plate 12 closest to the microstrip PCB board 3 be the first plate, the horizontal high voltage plate 13 closest to the second plate, the horizontal high voltage plate 13 next closest to the third plate, the horizontal high voltage plate 13 third closest to the fourth plate, the horizontal high voltage plate 13 furthest from the fifth plate, and the vertical high voltage plate 12 furthest from the sixth plate.

[0068] In this embodiment, the high voltage source of the high voltage supply module 11 feeds -8kV to the first electrode plate, -7kV to the second electrode plate, -6kV to the third electrode plate, -5kV to the fourth electrode plate, -4kV to the fifth electrode plate, and -3kV to the sixth electrode plate. The high voltage source of the high voltage supply module 11 also feeds -2kV to the upper layer of the microchannel plate MCP2 at the coaxial tapered cone 4 end.

[0069] In this configuration, the electric field direction is from right to left, causing the ionized product electrons to move to the right and eventually be collected at end 4 of the coaxial graded cone. The coaxial graded cone 4 collection structure in this embodiment is well-suited for synchrotrons or storage rings with extremely high vacuum (extremely weak signal) but slightly long bundle lengths (slightly low bandwidth), and can meet bundle length measurements ranging from DC to several nanoseconds.

[0070] If the absolute values ​​of the voltages of the vertical high-voltage plate 12 and the horizontal high-voltage plate 13 are proportional to their distances from the microstrip PCB board 3, then the ionization products move toward the microchannel plate MCP2 and are eventually collected by the microchannel plate MCP2.

[0071] In this embodiment, the high voltage supply module 11 feeds -3kV to the first plate, -4kV to the second plate, -5kV to the third plate, -6kV to the fourth plate, -7kV to the fifth plate, and -8kV to the sixth plate. The high voltage supply module 11 also feeds -2kV to the upper layer of the microchannel board MCP2 at the 3 end of the microstrip PCB board.

[0072] With this setup, the electric field direction is from left to right, causing the ionization product electrons to move to the left and eventually be collected by the microstrip PCB board 3. The microstrip PCB board 3 collection structure in this embodiment is very suitable for high-current linear accelerators with slightly lower vacuum requirements (slightly stronger signal) but shorter bundle lengths (higher bandwidth), and can meet the bundle length measurement requirements from DC to tens of ps.

[0073] The test results of the microstrip PCB board 3 in this embodiment are as follows: Figure 8 As shown, after feeding in an extremely short pulse signal on the order of tens of ps, the microstrip PCB board 3 can measure a pulse signal with a rising edge of about 32 ps, which translates to a bandwidth of about 10.9 GHz. Moreover, the measured waveform matches the source pulse very well, and the physical test meets the design specifications.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific embodiments of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention. The above content is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A longitudinal bundle measurement device based on residual gas ionization, characterized in that, include: High voltage electrostatic field section, microchannel plate MCP, microstrip PCB, coaxial tapered cone and oscilloscope; The high-voltage electrostatic field section is used to provide a uniform high-voltage electrostatic field that causes signal particles to move toward the detection end; The microchannel plate (MCP) is respectively disposed at the front end of the microstrip PCB and the coaxial tapered cone, and is used to avalanche amplify the acquired signal particles. The microstrip PCB board is used to collect signal particles with a first bandwidth. The coaxial tapered cone is used to collect signal particles with a second bandwidth. The first bandwidth is higher than the second bandwidth; the microstrip PCB board and the coaxial gradient cone are located at opposite ends of the high-voltage electrostatic field section; The oscilloscope is connected to the microstrip PCB board and the coaxial tapered cone respectively, and is used to process and display the signal particles collected by the microstrip PCB board and the coaxial tapered cone; The ratio of the impedance in the coaxial tapered cone to the inner and outer diameters of the coaxial structure satisfies the following formula: in, It is characteristic impedance. It is the vacuum permeability. It is the vacuum permittivity. It is the radius of the outer conductor. It is the radius of the inner conductor.

2. The longitudinal bundle measurement device based on residual gas ionization as described in claim 1, characterized in that, The signal particles are the ionization products of charged particles from the beam and residual vacuum gas. The average energy loss of a single particle incident on the residual gas is calculated. E; the average energy loss Multiply E by the longitudinal length L of the observation area, then multiply by the average beam current I0, and then divide by the average energy consumption W for generating gas ions and electron pairs to obtain the amount of ionization products generated after the beam passes through the residual gas medium.

3. The longitudinal bundle measurement device based on residual gas ionization as described in claim 2, characterized in that, The average energy loss of a single particle incident residual gas The formula for calculating E is: in, It is the energy of the signal electrons. x These are the coordinates of the direction of motion of the signal electrons. It is Avogadro's constant. r e It is the classical radius of the electron. m e The rest mass of an electron; c It is the speed of light in a vacuum. z c The charge state of the incident particle, It is the density of the gas medium. Z t The atomic number of the medium; A t The atomic mass of the medium; It is the ratio of the velocity of the incident particle to the speed of light; γ is the Lorentz factor; I is the average ionization and excitation energy of the gas; It is a density correction term. It is a shell correction term 。 4. The longitudinal bundle measurement device based on residual gas ionization as described in claim 1, characterized in that, The high-voltage electrostatic field unit includes a high-voltage supply module, a vertical high-voltage plate, a horizontal high-voltage plate, a supporting ceramic, and a hollow frame. The high-voltage supply module is used to provide a high-voltage signal for the high-voltage electrostatic field. The high-voltage supply module is connected to the vertical high-voltage plate and the horizontal high-voltage plate. The vertical high-voltage plate is perpendicular to the direction of particle motion, and the horizontal high-voltage plate is parallel to the direction of particle motion. The vertical high-voltage plate and the horizontal high-voltage plate are fixed to the hollow frame through the supporting ceramic.

5. The longitudinal bundle measurement device based on residual gas ionization as described in claim 4, characterized in that, The microchannel plate (MCP) is connected to the high-voltage supply module at both ends. The MCP has a double-layer structure, and high voltage is applied only to the top microchannel plate (MCP).

6. The longitudinal bundle measurement device based on residual gas ionization as described in claim 4, characterized in that, The measuring device further includes a first signal cable, which comprises a signal cable for a microstrip PCB board and a signal cable for a coaxial tapered cone. One end of the signal cable for the microstrip PCB board is connected to the output end of the microstrip PCB board; the other end of the signal cable for the microstrip PCB board is fixed to a knife-edge flange and connected to a signal feedthrough; one end of the signal cable for the coaxial tapered cone is connected to the inner core of the coaxial tapered cone, and the other end of the signal cable for the coaxial tapered cone is fixed to a knife-edge flange and connected to a signal feedthrough.

7. The longitudinal bundle measurement device based on residual gas ionization as described in claim 6, characterized in that, The signal feedthrough is connected to a second signal cable via an SMA adapter. The second signal cable is connected to a power amplifier or attenuator, and the power amplifier or attenuator is connected to the oscilloscope via the second signal cable.

8. The longitudinal bundle measurement device based on residual gas ionization as described in claim 4, characterized in that, The measuring device also includes a high-voltage conductor. One end of the high-voltage conductor is connected to a vertical high-voltage plate, a horizontal high-voltage plate, and a microchannel plate. The other end of the high-voltage conductor is fixed to a knife-edge flange and connected to a high-voltage feeder, which is connected to a high-voltage supply module.

9. A method for measuring longitudinal bundles based on residual gas ionization, characterized in that, The longitudinal bundle measurement device based on residual gas ionization as described in any one of claims 1-8 includes the following steps: The voltages of the vertical high-voltage plate and the horizontal high-voltage plate are set, and the corresponding voltages are fed into the high-voltage supply module. If the absolute values ​​of the voltages of the vertical and horizontal high-voltage plates are inversely proportional to their distances from the microstrip PCB board, then the ionization products move toward the coaxial tapered cone end and are eventually collected by the coaxial tapered cone end. If the absolute values ​​of the voltages of the vertical and horizontal high-voltage plates are proportional to their distances from the microstrip PCB, then the ionization products move toward the microchannel plate (MCP) and are eventually collected by the MCP.

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