An integrated probe for air-induced ultraviolet fluorescence detection

Abstract

This invention discloses an integrated probe for air-induced ultraviolet fluorescence detection. A detachable snap-in filter (1) is installed at the light inlet of the front end of the cylindrical metal shield shell. A photomultiplier tube (2) is installed close to the back of the filter. A photomultiplier tube base (3) is set at the bottom of the photomultiplier tube (2). A photomultiplier tube base fixing plate (4) is set at the bottom of the photomultiplier tube base (3). The photomultiplier tube base fixing plate (4), the high voltage divider plate (7), the signal processing readout and power supply board (8), and the hollow fixing plate (9) are connected by support columns (6) and fixed with support column fixing screws (5) on both sides. This invention solves the technical problem that existing photon counting detection equipment is difficult to balance low cost, low noise, and compact structure in the application scenario of ultraviolet fluorescence remote sensing induced by radioactive nuclides in the air.

Description

Technical Field

[0001] This invention belongs to the field of air-induced ultraviolet fluorescence remote sensing, specifically relating to an integrated probe for air-induced ultraviolet fluorescence detection. Background Technology

[0002] In the field of ultraviolet fluorescence remote sensing induced by radioactive nuclides in air (primarily nitrogen as the light source), the target signal intensity is often as low as several hundred photons per second or even lower, falling within the typical photon counting range. Existing high-end detection equipment, such as EMCCDs or superconducting nanowire single-photon detectors, while exhibiting excellent performance, is expensive and bulky, hindering widespread adoption. Low-cost solutions often employ silicon photomultiplier tubes (SiPMs), which offer high dark count rates and are temperature-sensitive. Furthermore, existing devices often suffer from deficiencies in electromagnetic shielding design under photon pulse mode, making it difficult to achieve low detection limits under uncooled, low-hardware-cost conditions. Therefore, developing a technical solution that optimizes charge-sensitive preamplifier and electromagnetic shielding structures to achieve high-gain, low-noise, and high-linearity detection at low cost has significant application value.

[0003] Currently, the closest to this invention is the highly integrated commercial photon counting module in the industry (represented by the typical Hamamatsu H10682 series photon counting head). According to publicly available technical information on this type of prior art, it typically encapsulates a metal-packaged photomultiplier tube, a high-speed photon counting circuit, and a high-voltage power supply circuit in a compact metal box. This solution emphasizes "plug and play," with the threshold levels of its high-voltage power supply and internal discriminator preset according to the manufacturer's optimal values. Users only need to connect a +5V power supply to directly obtain the digital signal of the photon count. In addition, some high-end models also have an excessive incident light detection function, which can output an alarm signal when the output count decreases due to excessive incident light to help determine whether the measurement data is normal. However, this highly commercially integrated solution has significant research limitations and physical defects. First, it directly performs threshold discrimination and outputs digital pulses internally, which means that the analog amplitude information of single photons is lost. Secondly, in order to achieve high-speed photon counting and overload detection, complex high-speed amplification and logic judgment circuits must be built inside, which not only significantly increases the hardware cost, but also the inherent thermal noise of broadband high-speed circuits is often relatively large.

[0004] In the current field of single-photon level extremely weak light detection, several traditional detection schemes are mainly relied upon, but all of them have significant physical or engineering defects.

[0005] Firstly, there are high-end EMCCD (electron multiplier charge-coupled device) or superconducting single-photon detector solutions. While these devices have extremely high detection limits, they are extremely expensive and large in size, typically requiring complex deep cooling systems.

[0006] Secondly, there is the SiPM (Silicon Photomultiplier Tube) solution, which has been widely used in recent years. As a low-cost semiconductor device, SiPM is extremely small and operates at low voltage, but its biggest technical bottleneck lies in its extremely high dark count rate and its extreme sensitivity to temperature changes. Under uncooled conditions at room temperature, the huge thermally excited dark count noise of SiPM will directly overwhelm the extremely weak light signal of the target, resulting in a very poor signal-to-noise ratio, making it unsuitable for fluorescence measurement in extremely weak light environments.

[0007] To address the numerous shortcomings of existing technologies, this invention aims to provide a compact, low-noise integrated probe for air-induced ultraviolet fluorescence detection. The core objective of this invention is to achieve high gain, high signal-to-noise ratio extraction, and interference protection for weak single-photon level signals at a lower hardware cost, based on traditional photomultiplier tubes and amplifier circuits, without relying on expensive cooling equipment. This is achieved through extreme selection of key component parameters (feedback resistors and capacitors), an innovative back-to-back stacked structure of dual circular circuit boards, and the use of a "flexible flying wire" direct connection technology that completely eliminates parasitic capacitance. This addresses both the physical structure and circuit characteristics from the perspectives of physical structure and circuit characteristics.

[0008] This invention addresses the technical challenges of achieving low cost, low noise floor, and compact structure in applications involving radioactively induced ultraviolet fluorescence telemetry (several hundred photons per second). In such extremely weak light environments as air-induced ultraviolet fluorescence telemetry, the single-photon charge output by the photomultiplier tube (PMT) is extremely small (typically at the pC level). Traditional amplification circuits are highly susceptible to having their weak single-photon signals completely drowned out by the inherent resistance thermal noise or chip noise floor. Furthermore, within the confined cylindrical internal space of portable devices, improper layout of the high-voltage divider circuit and signal processing circuitry, or the use of traditional rigid pin connections, can introduce fatal parasitic capacitances leading to signal shunting, generate spatial crosstalk, and even cause arcing damage to the signal terminals due to high voltage. Moreover, extremely weak ultraviolet fluorescence detection is highly susceptible to the influence of ambient visible light, necessitating a physical integration solution that can effectively filter out visible stray light such as sunlight at the front end of a compact structure. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention proposes an integrated probe for air-induced ultraviolet fluorescence detection, which solves the technical problem that existing photon counting detection devices struggle to achieve low cost, low noise floor, and compact structure in the application scenario of ultraviolet fluorescence remote sensing induced by radioactive nuclides in the air.

[0010] The technical solution of the present invention is as follows:

[0011] An integrated probe for air-induced ultraviolet fluorescence detection includes a filter, a photomultiplier tube, a photomultiplier tube base, a photomultiplier tube base fixing plate, a support column fixing screw, a support column, a high voltage divider plate, a signal processing readout and power supply board, a hollow fixing plate, a BNC signal output plug, a PMT high voltage power supply plug, and a signal processing readout and power supply board plug.

[0012] A removable snap-in filter is installed at the front light inlet of the cylindrical metal shielding shell. A photomultiplier tube is installed behind the filter. A photomultiplier tube base is located at the bottom of the photomultiplier tube, and a photomultiplier tube base fixing plate is located at the bottom of the base. The photomultiplier tube base fixing plate, high-voltage divider board, signal processing readout and power supply board, and hollow fixing plate are connected by support columns on both sides and fixed with support column fixing screws. The hollow fixing plate and BNC signal output plug are also connected by support columns on both sides and fixed with support column fixing screws. The rear end of the cylindrical metal shielding shell has three openings for inserting external plug modules: a BNC signal output plug, a PMT high-voltage power plug, and a signal processing readout and power supply board plug. The photomultiplier tube base and high-voltage divider board are connected by a flying wire, and are installed back-to-back parallel to each other, connected by a flying wire in the middle.

[0013] Preferably, the filter is used to block interference from ambient stray light and background light at the physical source, precisely defining the wavelength range of the detected photons.

[0014] Preferably, the photomultiplier tube is the N2013 from North Night Vision, whose spectral response peak covers the 300nm-400nm air-induced ultraviolet fluorescence band, enabling the highest quantum efficiency conversion of target ultraviolet photons, and is responsible for converting photons into weak charge pulses at the picocoulomb level.

[0015] Preferably, the high-voltage divider board includes a high-voltage divider circuit and a high-voltage divider circuit power supply circuit; the high-voltage divider circuit and the high-voltage divider circuit power supply circuit are connected.

[0016] Preferably, the high-voltage divider circuit includes resistors and capacitors; one end of the first-stage voltage divider resistor R1 is grounded and connected to the cathode lead-out terminal K1, which is connected to the cathode of the photomultiplier tube via a wire; the other end of resistor R1 is connected to one end of the second-stage voltage divider resistor R2, and their common connection point serves as the first dynode lead-out terminal DY1, which is connected to the first dynode of the photomultiplier tube via a wire; one end of the second-stage voltage divider resistor R2 is connected to the first dynode lead-out terminal DY1, and the other end of the second-stage voltage divider resistor R2 is connected to the second dynode lead-out terminal DY2; one end of the third-stage voltage divider resistor R3 is connected to the first dynode lead-out terminal DY1. Y2, the other end of the third voltage divider resistor R3 is connected to the third dynamo terminal DY3, one end of the fourth voltage divider resistor R4 is connected to the third dynamo terminal DY3, and the other end of the fourth voltage divider resistor R4 is connected to the fourth dynamo terminal DY4, one end of the fifth voltage divider resistor R5 is connected to the fourth dynamo terminal DY4, and the other end of the fifth voltage divider resistor R5 is connected to the fifth dynamo terminal DY5, one end of the sixth voltage divider resistor R6 is connected to the fifth dynamo terminal DY5, and the other end of the sixth voltage divider resistor R6 is connected to the sixth dynamo terminal DY6, one end of the seventh voltage divider resistor R7 is connected to the sixth dynamo terminal DY6. The other end of the seventh voltage divider resistor R7 is connected to the seventh dynamo terminal DY7. One end of the eighth voltage divider resistor R8 is connected to the seventh dynamo terminal DY7, and the other end of the eighth voltage divider resistor R8 is connected to the eighth dynamo terminal DY8. One end of the ninth voltage divider resistor R9 is connected to the eighth dynamo terminal DY8, and the other end of the ninth voltage divider resistor R9 is connected to the ninth dynamo terminal DY9, the tenth voltage divider resistor R10, and one end of the capacitor C1. The other end of the tenth voltage divider resistor R10 is connected to the tenth dynamo terminal DY10, the eleventh voltage divider resistor R11, and one end of the capacitor C2. The eleventh voltage divider resistor... The other end of R11 is connected to the eleventh dynamo electrode DY11, the twelfth voltage divider resistor R12, and one end of capacitor C3. The other end of the twelfth voltage divider resistor R12 is connected to one end of the anode load resistor R13 and has a lead-out terminal HV. The other end of resistor R13 is connected to one end of DC blocking capacitor C4. The common connection point of the two is used as the anode lead-out terminal A1, which is connected to the anode of the photomultiplier tube through a wire. The other end of DC blocking capacitor C4 is connected to the signal lead-out terminal PMT_SIGNAL as a signal output, which is used to transmit the weak single-photon pulse generated by the photomultiplier tube after DC blocking to the subsequent signal processing and readout circuit.

[0017] The ninth dynamo terminal DY9, the tenth dynamo terminal DY10, and the eleventh dynamo terminal DY11 are respectively compensated by capacitors C1, C2, and C3 for charge compensation. In order to suppress the interstage voltage drop caused by instantaneous inrush current, charge compensation capacitors are connected in parallel at the last few dynamo terminals.

[0018] Preferably, the signal processing readout and power supply board includes a signal processing readout circuit, a signal processing readout circuit power supply circuit, and a high-voltage divider circuit power supply circuit; the signal processing readout circuit is connected to the signal processing readout circuit power supply circuit.

[0019] Preferably, the signal processing readout circuit includes a TPH2502-SR chip, resistors, and capacitors;

[0020] Pin 1 of the TPH2502-SR chip is connected to one end of resistor RF and one end of capacitor CF, one end of resistor R16 and one end of capacitor C7, respectively; Pin 2 of the TPH2502-SR chip is connected to the other end of capacitor CF and the other end of resistor RF, and has a lead-out terminal PMT_SIGNAL connected to the signal lead-out terminal PMT_SIGNAL via a wire; Pin 3 of the TPH2502-SR chip is connected to ground; Pin 4 of the TPH2502-SR chip is connected to ground capacitor C9 and ground... Capacitor C8 and resistor are connected together with a network label -1.8V; pin 5 of chip TPH2502-SR is connected to the other end of resistor R16, the other end of capacitor C7 and ground resistor R17; pin 6 of chip TPH2502-SR is connected to pin 7 of chip TPH2502-SR and one end of resistor R18; the other end of resistor R18 is connected to the external output; pin 8 of chip TPH2502-SR is connected to ground capacitor C14 and ground capacitor C13, and is connected with a network label +1.8V.

[0021] Preferably, the power supply circuit for the signal processing readout circuit includes a chip SPX3819M5-L-1-8, a chip SGM2209-ADJ, resistors, and capacitors;

[0022] Pins 1 and 3 of chip SPX3819M5-L-1-8 are connected to ground capacitors C15 and C16 and a +6V power supply; pin 2 of chip SPX3819M5-L-1-8 is grounded; pin 4 of chip SPX3819M5-L-1-8 is connected to ground capacitor C17; pin 5 of chip SPX3819M5-L-1-8 is connected to ground capacitor C18 and one end of resistor R19; the other end of resistor R19 is connected to the +1.8V network tag of the signal processing readout circuit of claim 6 through the network tag +1.8V. Pin 1 of chip SGM2209-ADJ is connected to ground; pins 2 and 3 of chip SGM2209-ADJ are both connected to grounding capacitor C10, grounding capacitor C11 and -6V power supply; pin 4 of chip SGM2209-ADJ is connected to one end of resistor R21 and grounding resistor R22 respectively; pin 5 of chip SGM2209-ADJ is connected to grounding capacitor C12, the other end of resistor R21 and one end of resistor R20; the other end of resistor R20 is connected to the network tag -1.8V of the signal processing readout circuit through the network tag -1.8V.

[0023] Preferably, the high-voltage divider circuit power supply circuit includes resistors and capacitors; one end of capacitor C5 is connected to one end of capacitor C6 and ground HV-GND respectively, and the other end of capacitor C5 is connected to one end of resistor R14 and one end of resistor R15 respectively; the other end of resistor R15 is connected to lead-out terminal HV, which is connected to lead-out terminal HV of claim 5 through a wire; the other end of resistor R14 is connected to high-voltage lead-out terminal +HV, and the high-voltage lead-out terminal is connected to high-voltage power supply through a wire.

[0024] The beneficial effects of the integrated probe for air-induced ultraviolet fluorescence detection of this invention are as follows:

[0025] 1. This invention employs an innovative dual-board coaxial stacking structure to achieve extreme compactness and strong high-voltage isolation: This invention abandons the traditional single-board mixed wiring or pin-type multi-board structure, innovatively adopting a "dual circular PCB back-to-back coaxial stacking" design. This structure not only maximizes the use of the narrow cylindrical tubular space, but also physically isolates the thousands of volts of high-voltage electric field from the millivolt-level weak signals to the greatest extent, fundamentally eliminating the risk of high-voltage crosstalk and arcing.

[0026] 2. A pioneering "flexible flying wire" design combined with extreme parameters completely overcomes the bottlenecks of low noise and parasitic capacitance: This invention avoids blindly piling on expensive noise reduction hardware. Instead, it innovatively uses zero-cost "flexible flying wires" to directly connect to high-impedance sensitive nodes, completely cutting off parasitic capacitance and surface leakage interference caused by traditional mechanical pin headers, while also eliminating mechanical stress during assembly in confined spaces. Combined with the extreme parameter combination of a 100MΩ ultra-large feedback resistor and a 5pF micro-feedback capacitor in the first-stage charge-sensitive amplifier, the circuit's own thermal noise current is effectively reduced. Ultimately, the maximum noise amplitude at the signal output is only about 2mVpp.

[0027] 3. This invention balances high-fidelity analog signal extraction and high-speed pulse recovery: Unlike highly integrated commercial photon counting modules that directly output digital pulses and thus lose single-photon analog amplitude information, this invention fully preserves the true high signal-to-noise ratio analog waveform. Simultaneously, through a three-stage circuit—charge-sensitive preamplifier, pole-zero cancellation circuit, and voltage follower circuit—the tailing is reduced to approximately 5μs, significantly improving the system's photon resolution and counting capabilities in extremely low-light environments.

[0028] 4. The invention boasts extremely high research cost-effectiveness and excellent room-temperature uncooled performance: This invention eliminates the need for the hundreds of thousands of yuan hardware investment required for EMCCD equipment and the fragile deep cooling system. Simultaneously, it reverts to the physical characteristics of a dual-alkali cathode PMT, suppressing the dark count rate to the tens of hertz level at room temperature, perfectly avoiding the fatal flaw of SiPM devices where extremely high dark counts at room temperature render them unusable. In actual physical testing at a 1000V operating high voltage, this compact probe successfully and stably captured single-photon event pulses with an average amplitude of 400mV, corresponding to approximately 2pC of real, weak charge, without peak clipping or baseline drift, fully meeting the research needs of modern portable, compact telemetry missions. Attached Figure Description

[0029] To more clearly illustrate the purpose, design concept, and innovation of the integrated probe for air-induced ultraviolet fluorescence detection proposed in this invention, the invention will be described in detail below with reference to the accompanying drawings and tables.

[0030] Figure 1 This is an illustrative diagram illustrating the probe components of the present invention.

[0031] Figure 2 This is a diagram of the high voltage divider board and the signal processing readout and power supply board of the present invention.

[0032] Figure 3 This is a waveform diagram of the OUTPUT output signal of the signal processing readout circuit of the present invention.

[0033] Figure 4 This is the filter pattern in the three-dimensional view of the present invention.

[0034] Figure 5 This is a perspective view of the present invention showing the direction of the insertion hole.

[0035] Figure reference numerals: 1-Filter, 2-Photomultiplier tube, 3-Photomultiplier tube base, 4-Photomultiplier tube base fixing plate, 5-Support column fixing screw, 6-Support column, 7-High voltage divider plate, 8-Signal processing readout and power supply board, 9-Hollow fixing plate, 10-BNC signal output plug, 11-PMT high voltage power plug, 12-Signal processing readout and power supply board plug. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0038] like Figure 1 , Figure 2 , Figure 4 and Figure 5 As shown, an integrated probe for air-induced ultraviolet fluorescence detection includes a filter 1, a photomultiplier tube 2, a photomultiplier tube base 3, a photomultiplier tube base fixing plate 4, a support column fixing screw 5, a support column 6, a high voltage divider plate 7, a signal processing readout and power supply board 8, a hollow fixing plate 9, a BNC signal output plug 10, a PMT high voltage power plug 11, and a signal processing readout and power supply board plug 12.

[0039] A removable snap-in filter 1 is installed at the light inlet of the front end of the cylindrical metal shielding shell. A photomultiplier tube 2 is installed close to the back of the filter. A photomultiplier tube base 3 is set at the bottom of the photomultiplier tube 2. A photomultiplier tube base fixing plate 4 is set at the bottom of the photomultiplier tube base 3. The photomultiplier tube base fixing plate 4, the high voltage divider plate 7, the signal processing readout and power supply board 8, and the hollow fixing plate 9 are connected by support columns 6 on both sides and fixed with support column fixing screws 5. The hollow fixing plate 9 and the BNC signal output plug 10 are connected by support columns on both sides and fixed with support column fixing screws. The rear end of the cylindrical metal shielding shell has three openings for inserting external plug modules, namely the BNC signal output plug 10, the PMT high voltage power plug 11, and the signal processing readout and power supply board plug 12. The photomultiplier tube base 3 and the high voltage divider plate 7 are connected by a flying wire. The photomultiplier tube base 3 and the high voltage divider plate 7 are installed back to back and parallel to each other, connected by a flying wire in the middle.

[0040] The filter 1 in this embodiment is used to block the interference of ambient stray light and background light from the physical source, and accurately limit the wavelength range of the detected photons.

[0041] The photomultiplier tube 2 in this implementation scheme is the N2013 from North Night Vision. Its spectral response peak covers the air-induced ultraviolet fluorescence band of 300nm-400nm, which can achieve the highest quantum efficiency conversion of target ultraviolet photons and is responsible for converting photons into weak charge pulses at the picocoulomb level.

[0042] The high-voltage divider board 7 in this embodiment includes a high-voltage divider circuit and a high-voltage divider circuit power supply circuit; the high-voltage divider circuit is connected to the voltage divider circuit power supply circuit.

[0043] A high-voltage divider circuit includes resistors and capacitors;

[0044] One end of the first-stage voltage divider resistor R1 is grounded and connected to the cathode lead-out terminal K1. The cathode lead-out terminal is connected to the cathode of the photomultiplier tube via a wire. The other end of resistor R1 is connected to one end of the second-stage voltage divider resistor R2. Their common connection point serves as the first dynamo lead-out terminal DY1, which is connected to the first dynamo of the photomultiplier tube via a wire. One end of the second-stage voltage divider resistor R2 is connected to the first dynamo lead-out terminal DY1, and the other end is connected to the second dynamo lead-out terminal DY2. One end of the third-stage voltage divider resistor R3 is connected to the first dynamo lead-out terminal DY2, and the third voltage divider resistor R3... The other end is connected to the third dynamo lead DY3. One end of the fourth voltage divider resistor R4 is connected to the third dynamo lead DY3, and the other end of the fourth voltage divider resistor R4 is connected to the fourth dynamo lead DY4. One end of the fifth voltage divider resistor R5 is connected to the fourth dynamo lead DY4, and the other end of the fifth voltage divider resistor R5 is connected to the fifth dynamo lead DY5. One end of the sixth voltage divider resistor R6 is connected to the fifth dynamo lead DY5, and the other end of the sixth voltage divider resistor R6 is connected to the sixth dynamo lead DY6. One end of the seventh voltage divider resistor R7 is connected to the sixth dynamo lead DY6, and the seventh voltage divider resistor R7 is connected to the sixth dynamo lead DY6. The other end of R7 is connected to the seventh dynamo terminal DY7. One end of the eighth voltage divider resistor R8 is connected to the seventh dynamo terminal DY7, and the other end of the eighth voltage divider resistor R8 is connected to the eighth dynamo terminal DY8. One end of the ninth voltage divider resistor R9 is connected to the eighth dynamo terminal DY8, and the other end of the ninth voltage divider resistor R9 is connected to the ninth dynamo terminal DY9, the tenth voltage divider resistor R10, and one end of capacitor C1. The other end of the tenth voltage divider resistor R10 is connected to the tenth dynamo terminal DY10, the eleventh voltage divider resistor R11, and one end of capacitor C2. The other end of the eleventh voltage divider resistor R11... One end is connected to the eleventh dynamo electrode DY11, the twelfth voltage divider resistor R12, and one end of capacitor C3. The other end of the twelfth voltage divider resistor R12 is connected to one end of the anode load resistor R13 and has a lead-out terminal HV. The other end of resistor R13 is connected to one end of DC blocking capacitor C4. The common connection point of the two is used as the anode lead-out terminal A1, which is connected to the anode of the photomultiplier tube through a wire. The other end of DC blocking capacitor C4 is connected to the signal lead-out terminal PMT_SIGNAL as a signal output, which is used to transmit the weak single-photon pulse generated by the photomultiplier tube after DC blocking to the subsequent signal processing and readout circuit.

[0045] The ninth dynamo terminal DY9, the tenth dynamo terminal DY10, and the eleventh dynamo terminal DY11 are respectively compensated by capacitors C1, C2, and C3 for charge compensation. In order to suppress the interstage voltage drop caused by instantaneous inrush current, charge compensation capacitors are connected in parallel at the last few dynamo terminals.

[0046] The signal processing readout and power supply board 8 of this embodiment includes a signal processing readout circuit, a signal processing readout circuit power supply circuit, and a high voltage divider circuit power supply circuit; the signal processing readout circuit is connected to the signal processing readout circuit power supply circuit.

[0047] The signal processing readout circuit of this embodiment includes a chip TPH2502-SR, resistors, and capacitors;

[0048] Pin 1 of the TPH2502-SR chip is connected to one end of resistor RF and one end of capacitor CF, one end of resistor R16 and one end of capacitor C7, respectively; Pin 2 of the TPH2502-SR chip is connected to the other end of capacitor CF and the other end of resistor RF, and has a lead-out terminal PMT_SIGNAL connected to the signal lead-out terminal PMT_SIGNAL via a wire; Pin 3 of the TPH2502-SR chip is connected to ground; Pin 4 of the TPH2502-SR chip is connected to ground capacitor C9, ground capacitor C8 and resistor, and has a network tag -1.8V connected to it; Pin 5 of the TPH2502-SR chip is connected to the other end of resistor R16, the other end of capacitor C7 and ground resistor R17; Pin 6 of the TPH2502-SR chip is connected to Pin 7 of the TPH2502-SR chip and one end of resistor R18; the other end of resistor R18 is connected to an external output, and the external output signal is as follows. Figure 3 As shown; pin 8 of the TPH2502-SR chip is connected to ground capacitor C14 and ground capacitor C13 respectively, and is connected to a network tag +1.8V.

[0049] The power supply circuit for the signal processing readout circuit in this embodiment includes chip SPX3819M5-L-1-8, chip SGM2209-ADJ, resistors, and capacitors;

[0050] Pins 1 and 3 of the SPX3819M5-L-1-8 chip are connected to ground capacitors C15 and C16 and the +6V power supply; pin 2 of the SPX3819M5-L-1-8 chip is grounded; pin 4 of the SPX3819M5-L-1-8 chip is connected to ground capacitor C17; pin 5 of the SPX3819M5-L-1-8 chip is connected to ground capacitor C18 and one end of resistor R19; the other end of resistor R19 is connected to the +1.8V network tag of the signal processing readout circuit through the network tag. Pin 1 of the SGM2209-ADJ is connected to ground; pins 2 and 3 of the SGM2209-ADJ are both connected to grounding capacitor C10, grounding capacitor C11, and the -6V power supply; pin 4 of the SGM2209-ADJ is connected to one end of resistor R21 and grounding resistor R22; pin 5 of the SGM2209-ADJ is connected to grounding capacitor C12, the other end of resistor R21, and one end of resistor R20; the other end of resistor R20 is connected to the network tag -1.8V of the signal processing readout circuit through the network tag -1.8V.

[0051] The high-voltage divider circuit power supply circuit of this implementation scheme includes resistors and capacitors; one end of capacitor C5 is connected to one end of capacitor C6 and ground HV-GND respectively, and the other end of capacitor C5 is connected to one end of resistor R14 and one end of resistor R15 respectively; the other end of resistor R15 is connected to lead-out terminal HV, which is connected to lead-out terminal HV through a wire; the other end of resistor R14 is connected to high-voltage lead-out terminal +HV, which is connected to high-voltage power supply through a wire.

[0052] In this implementation scheme, the probe of the present invention is encapsulated in a grounded cylindrical metal shielding shell, and from front to back, it integrates an optical filtering module, a photon detection unit, a high voltage divider circuit, a signal processing readout circuit, a power supply circuit, and an external plug module in sequence through a connecting and fixing module.

[0053] For the cylindrical metal shielding housing, to prevent external electromagnetic interference from affecting the output signal of the photon detector unit, the joints of the threaded cover, filter cover, sleeve, plug top cover, and top threaded cover are all low-resistance conductive contacts, and are connected to the ground as a whole to form electromagnetic shielding. Furthermore, to prevent light leakage, black fluororubber rings are used for sealing at the contact points between the filter cover and the filter, between the filter cover and the sleeve, and between the plug top cover and the sleeve. The threaded cover, plug top cover, and filter cover also employ an interlocking design to prevent light leakage.

[0054] In terms of overall physical structure and front-end optical design, the various parts inside the probe are connected and fixed by connection modules. Specifically, the rear end of the cylindrical metal shielding shell has three openings for inserting external plug modules: a BNC signal output plug 10, a PMT high-voltage power plug 11, and a signal processing readout circuit power plug 12. A detachable, snap-in ultraviolet bandpass optical filter 1 (such as a solar-blind ultraviolet filter matching a specific band of nitrogen fluorescence) is installed at the front light inlet of the cylindrical metal shielding shell as an optical filtering module. This filter blocks interference from ambient stray light and background light at the physical source, precisely limiting the wavelength range of the detected photons. Right behind the filter, a linear focusing photomultiplier tube 2 with a dual-alkali photocathode is installed as a photon detection unit. The selected model here is the N2013 from North Night Vision. Its spectral response peak covers the 300nm-400nm air (nitrogen) induced ultraviolet fluorescence band, which can achieve the highest quantum efficiency conversion of target ultraviolet photons and is responsible for converting photons into weak charge pulses at the picocoulomb level.

[0055] In terms of internal physical architecture, this invention abandons the traditional single-board hybrid wiring or pin-type multi-board structure, and innovatively adopts an internal stacking design of "double circular boards back-to-back with flexible flying wires". The system consists of two circular printed circuit boards of the same diameter. The first board is the "high voltage divider board 7", and the second board is the "signal processing readout and power supply board 8". The photomultiplier tube base 3 and the high voltage divider board 7 are connected by flying wires; the two boards are installed back-to-back in parallel, connected in the middle by flying wires, and fixed by support columns in the connection and fixing module. This design not only maximizes the use of the tubular internal space, but also isolates the high voltage field of thousands of volts from the weak signal of millivolts to the greatest extent in physical space. Furthermore, a very short flying wire is directly used for soldering, realizing the shortest transmission path for high impedance sensitive nodes, reducing parasitic capacitance to an extremely low level to reduce interference with the feedback capacitor CF, and eliminating mechanical stress during assembly in a confined space, which greatly improves the reliability of the probe in a vibration environment.

[0056] In terms of circuit system design, the present invention is divided into a high voltage divider circuit for nanosecond-level transient pulses, a signal processing and readout circuit, and a power supply module, which are carried on the "high voltage divider board" and the "signal processing, readout and power supply board".

[0057] The high-voltage divider board features a high-voltage divider circuit with a series of voltage divider resistors arranged in a compact ring around the PMT socket. The resistance values ​​are set as follows:

[0058] R1=470KΩ, R2=R3=R4=R5=R6=R7=R8=R9=R10=R11=R12=R=220kΩ

[0059] To provide steady-state DC bias and ensure the average load capacity of the system. For the transient inrush current with a duration of only nanoseconds (such as about 5ns for N2013) generated by single-photon events, this scheme connects a large charge compensation capacitor in parallel at the final stage electrode, with a capacitance of C1 = C2 = C3 = 10nF, to suppress the interstage voltage drop caused by the transient inrush current and ensure that the energy linearity deviation of the pulse measurement is strictly controlled within ±1%.

[0060] The signal processing readout and power supply board is equipped with a low-noise signal readout processing circuit optimized for extreme parameters and a power supply circuit for the high-voltage divider circuit and the signal processing circuit. First, a bipolar high-speed diode is connected in reverse parallel between the signal input terminal and ground, which forms a high-voltage clamping protection network to effectively protect the subsequent circuits.

[0061] For the signal readout processing circuit, the TPH2502-SR is a dual operational amplifier chip. Pins 1, 2, and 3 correspond to the output, inverting, and non-inverting inputs of operational amplifier 1, respectively. Pins 5, 6, and 7 correspond to the non-inverting, inverting, and output inputs of operational amplifier 2, respectively. Pins 4 and 8 correspond to the negative and positive voltage point source inputs. The first-stage charge-sensitive preamplifier employs extreme parameter configurations: a small 5pF feedback capacitor CF is used to convert a weak charge of approximately 2pC into a high signal-to-noise ratio voltage signal of several hundred millivolts within the operational amplifier's safe power supply rail; simultaneously, a 100MΩ-level feedback resistor RF is used to reduce the circuit's own thermal noise current, solving the problem of excessive noise floor in traditional low-impedance circuits. Since the first-stage output signal has a tail of approximately 500μs, this solution improves the tail to approximately 5μs through the 5pF coupling capacitor C7, the 100MΩ parallel resistor R16, and the 1MΩ grounding resistor R17 in the second-stage pole-zero cancellation circuit. The narrow pulse output impedance after being shaped by the pre-stage zero-phase cancellation network is extremely high. If directly connected to external measuring equipment, it will cause severe signal voltage attenuation. Therefore, a voltage follower is cascaded at the end to transmit the original amplitude of the single-photon voltage pulse to the back-end measuring instrument without loss through the 50Ω matching resistor R18 at the output end and the external coaxial cable.

[0062] For the power supply circuits of the high-voltage divider circuit and the signal processing circuit, the SPX3819 and SGM2209 provide ±1.8 V power to the operational amplifier TPH2502, respectively. Both the SPX3819 and SGM2209 have extremely low output voltage noise, typically 40 μVRMS and 130 μVRMS, respectively, significantly reducing the noise introduced into the photon detector output signal loop. Ultimately, the maximum noise amplitude at the signal output is only about 2 mVpp.

[0063] The core protection points of the claims proposed in this invention are:

[0064] This invention encompasses three levels: physical structure, circuit design, and selection of electronic components. At the physical structure level, it requires a structure that protects a cylindrical metal shielding shell, a combined architecture of an ultraviolet bandpass filter at the front end for filtering visible light and a dual-alkali photocathode PMT, and a back-to-back coaxial stacked structure of the probe's dual circular PCBs.

[0065] At the circuit level, protection is required for a specific combination circuit design for extremely weak light pulses, namely: selection of signal readout processing circuit and power supply circuit chips, circuit design of high voltage divider circuit and selection of electronic components, and the first-stage charge sensitive amplifier and pole-zero cancellation circuit composed of 100MΩ high impedance and 5pF small feedback capacitor of signal readout processing circuit.

[0066] This probe is not only suitable for detecting air-induced ultraviolet fluorescence, but also for detecting extremely weak fluorescence in other gases.

Claims

1. An integrated probe for air-induced ultraviolet fluorescence detection, characterized in that, Includes filter (1), photomultiplier tube (2), photomultiplier tube base (3), photomultiplier tube base fixing plate (4), support column fixing screw (5), support column (6), high voltage divider plate (7), signal processing readout and power supply board (8), hollow fixing plate (9), BNC signal output plug (10), PMT high voltage power plug (11), and signal processing readout and power supply board plug (12). A removable snap-fit ​​filter (1) is installed at the light inlet of the front end of the cylindrical metal shielding shell. A photomultiplier tube (2) is installed close to the back of the filter. A photomultiplier tube base (3) is set at the bottom of the photomultiplier tube (2). A photomultiplier tube base fixing plate (4) is set at the bottom of the photomultiplier tube base (3). The photomultiplier tube base fixing plate (4), the high voltage divider plate (7), the signal processing readout and power supply board (8), and the hollow fixing plate (9) are connected by support columns (6) and fixed with support column fixing screws (5) on both sides. The hollow fixing plate (9) and the BNC signal output plug (10) are connected by support columns on both sides and fixed with support column fixing screws. The cylindrical metal shielding shell has three openings at the rear end for inserting external plug modules, namely the BNC signal output plug (10), the PMT high voltage power plug (11), and the signal processing readout and power supply board plug (12). The photomultiplier tube base (3) and the high voltage divider plate (7) are connected by flying wires. The photomultiplier tube base (3) and the high voltage divider plate (7) are installed back to back in parallel and connected in the middle by flying wires.

2. The integrated probe for air-induced ultraviolet fluorescence detection according to claim 1, characterized in that, The filter (1) is used to block the interference of ambient stray light and background light from the physical source, and accurately limits the wavelength range of the detected photons.

3. The integrated probe for air-induced ultraviolet fluorescence detection according to claim 1, characterized in that, The photomultiplier tube (2) is model N2013 from North Night Vision. Its spectral response peak covers the air-induced ultraviolet fluorescence band of 300nm-400nm, which can achieve the highest quantum efficiency conversion of target ultraviolet photons and is responsible for converting photons into weak charge pulses at the picocoulomb level.

4. The integrated probe for air-induced ultraviolet fluorescence detection according to claim 1, characterized in that, The high-voltage divider board (7) includes a high-voltage divider circuit.

5. The integrated probe for air-induced ultraviolet fluorescence detection according to claim 4, characterized in that, The high-voltage divider circuit includes resistors and capacitors; One end of the first-stage voltage divider resistor R1 is grounded and connected to the cathode lead-out terminal K1. The cathode lead-out terminal is connected to the cathode of the photomultiplier tube via a wire. The other end of resistor R1 is connected to one end of the second-stage voltage divider resistor R2. The common connection point of the two resistors serves as the first dynamo lead-out terminal DY1, which is connected to the first dynamo of the photomultiplier tube via a wire. One end of the second-stage voltage divider resistor R2 is connected to the first dynamo lead-out terminal DY1, and the other end is connected to the second dynamo lead-out terminal DY2. One end of the third-stage voltage divider resistor R3 is connected to the first dynamo lead-out terminal DY2, and the other end is connected to the first dynamo lead-out terminal DY2. One end of the fourth voltage divider resistor R4 is connected to the third voltage divider lead DY3, and the other end of the fourth voltage divider resistor R4 is connected to the fourth voltage divider lead DY4. One end of the fifth voltage divider resistor R5 is connected to the fourth voltage divider lead DY4, and the other end of the fifth voltage divider resistor R5 is connected to the fifth voltage divider lead DY5. One end of the sixth voltage divider resistor R6 is connected to the fifth voltage divider lead DY5, and the other end of the sixth voltage divider resistor R6 is connected to the sixth voltage divider lead DY6. One end of the seventh voltage divider resistor R7 is connected to the sixth voltage divider lead DY6, and the other end of the seventh voltage divider resistor R7 is connected to the sixth voltage divider lead DY6. The other end is connected to the seventh dynamo terminal DY7. One end of the eighth voltage divider resistor R8 is connected to the seventh dynamo terminal DY7, and the other end of the eighth voltage divider resistor R8 is connected to the eighth dynamo terminal DY8. One end of the ninth voltage divider resistor R9 is connected to the eighth dynamo terminal DY8, and the other end of the ninth voltage divider resistor R9 is connected to the ninth dynamo terminal DY9, the tenth voltage divider resistor R10, and one end of capacitor C1. The other end of the tenth voltage divider resistor R10 is connected to the tenth dynamo terminal DY10, the eleventh voltage divider resistor R11, and one end of capacitor C2. The eleventh voltage divider resistor R11... The other end is connected to one end of the eleventh dynamo electrode DY11, the twelfth voltage divider resistor R12, and capacitor C3, respectively. The other end of the twelfth voltage divider resistor R12 is connected to one end of the anode load resistor R13 and has a lead-out terminal HV. The other end of resistor R13 is connected to one end of DC blocking capacitor C4. The common connection point of the two is used as the anode lead-out terminal A1, which is connected to the anode of the photomultiplier tube through a wire. The other end of DC blocking capacitor C4 is connected to the signal lead-out terminal PMT_SIGNAL as a signal output, which is used to transmit the weak single-photon pulse generated by the photomultiplier tube after DC blocking to the subsequent signal processing and readout circuit. The ninth dynamo terminal DY9, the tenth dynamo terminal DY10, and the eleventh dynamo terminal DY11 are respectively compensated by capacitors C1, C2, and C3 for charge compensation. In order to suppress the interstage voltage drop caused by instantaneous inrush current, charge compensation capacitors are connected in parallel at the last few dynamo terminals.

6. The integrated probe for air-induced ultraviolet fluorescence detection according to claim 1, characterized in that, The signal processing readout and power supply board (8) includes a signal processing readout circuit, a signal processing readout circuit power supply circuit, and a high voltage divider circuit power supply circuit; the signal processing readout circuit is connected to the signal processing readout circuit power supply circuit.

7. The integrated probe for air-induced ultraviolet fluorescence detection according to claim 6, characterized in that, The signal processing readout circuit includes a chip TPH2502-SR, resistors, and capacitors; Pin 1 of the TPH2502-SR chip is connected to one end of resistor RF and one end of capacitor CF, one end of resistor R16 and one end of capacitor C7, respectively; pin 2 of the TPH2502-SR chip is connected to the other end of capacitor CF and the other end of resistor RF, and has a lead-out terminal PMT_SIGNAL connected to the signal lead-out terminal PMT_SIGNAL via a wire; pin 3 of the TPH2502-SR chip is connected to ground; pin 4 of the TPH2502-SR chip is connected to ground capacitor C9 and ground... Capacitor C8 and resistor are connected to a network tag -1.8V; pin 5 of the TPH2502-SR chip is connected to the other end of resistor R16, the other end of capacitor C7, and ground resistor R17; pin 6 of the TPH2502-SR chip is connected to pin 7 of the TPH2502-SR chip and one end of resistor R18; the other end of resistor R18 is connected to the external output; pin 8 of the TPH2502-SR chip is connected to ground capacitor C14 and ground capacitor C13, and is connected to a network tag +1.8V.

8. The integrated probe for air-induced ultraviolet fluorescence detection according to claim 6, characterized in that, The power supply circuit for the signal processing readout circuit includes chip SPX3819M5-L-1-8, chip SGM2209-ADJ, resistors, and capacitors. Pins 1 and 3 of the SPX3819M5-L-1-8 chip are connected to ground capacitors C15 and C16 and a +6V power supply; pin 2 of the SPX3819M5-L-1-8 chip is grounded; pin 4 of the SPX3819M5-L-1-8 chip is connected to ground capacitor C17; pin 5 of the SPX3819M5-L-1-8 chip is connected to ground capacitor C18 and one end of resistor R19; the other end of resistor R19 is connected to the +1.8V network tag of the signal processing readout circuit of claim 6 via a network tag. Pin 1 of the SGM2209-ADJ chip is connected to ground; pins 2 and 3 of the SGM2209-ADJ chip are both connected to grounding capacitor C10, grounding capacitor C11, and a -6V power supply; pin 4 of the SGM2209-ADJ chip is connected to one end of resistor R21 and grounding resistor R22; pin 5 of the SGM2209-ADJ chip is connected to grounding capacitor C12, the other end of resistor R21, and one end of resistor R20; the other end of resistor R20 is connected to the network tag -1.8V of the signal processing readout circuit through the network tag -1.8V.

9. The integrated probe for air-induced ultraviolet fluorescence detection according to claim 6, characterized in that, The high-voltage divider circuit power supply circuit includes resistors and capacitors; one end of capacitor C5 is connected to one end of capacitor C6 and ground HV-GND respectively, and the other end of capacitor C5 is connected to one end of resistor R14 and one end of resistor R15 respectively; the other end of resistor R15 is connected to lead-out terminal HV, which is connected to lead-out terminal HV through a wire; the other end of resistor R14 is connected to high-voltage lead-out terminal +HV, which is connected to high-voltage power supply through a wire.

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