CN219625363U - Boric acid detection Raman spectrometer based on multiple small array SPAD detectors - Google Patents

Abstract

The utility model discloses a boric acid detection Raman spectrometer based on a plurality of small array SPAD detectors, which comprises a laser, a sample focusing system, a sample Raman signal acquisition system and a data processing system. The utility model uses a laser as a laser source, uses a plurality of small array SPAD detectors as a sample Raman signal collecting device, records time domain information of Raman spectrum through a time-to-digital converter integrated on the detector, performs signal collection and processing on the small array SPAD detectors by a field programmable gate array control circuit, and finally compares the sample Raman spectrum obtained after algorithm processing on a computer with standard Raman spectrum of boric acid and water to realize the purpose of detecting boric acid content in the sample. The utility model adopts a plurality of small array SPAD detectors to replace a single large array detector, can accurately realize the detection of boric acid while reducing the cost, and has good use value and application prospect.

Description

Boric acid detection Raman spectrometer based on multiple small array SPAD detectors

Technical Field

The utility model relates to the technical field of Raman spectrometers, in particular to a Raman spectrometer for detecting and identifying boric acid in a solution by utilizing a plurality of small array SPAD detectors.

Background

The most commonly used detection method of the compound is high performance liquid chromatography or gas chromatography separation combined with ultraviolet light or mass spectrometer detection, but has the defects of long detection period, high analysis difficulty and high sample preparation cost, and cannot realize high-throughput screening. Raman spectroscopy is an emerging method for rapid, specific, ultrasensitive, high throughput detection of chemical species in samples, capable of rapidly providing highly specific information in a non-destructive manner for analysis of compounds. Raman-active species exhibit spectra with distinct peaks and provide "fingerprint" information about intramolecular vibrational transitions by uniquely characterizing the overall sample volume. In addition, a portable raman detection system is provided, wherein the signal can be remotely analyzed by optical fiber long-distance transmission, and compared with a high performance liquid chromatograph-mass spectrometer, the portable raman detection system enables on-site detection.

Boric acid is a neutron chemical poison of the primary loop coolant of a nuclear power plant to compensate for the control of the reactivity of the nuclear reactor by the control rods. Boric acid is weak acid, and has little corrosion effect on stainless steel equipment in a loop environment, and the corrosion effect on the equipment is mainly that the boric acid leaks, and water is evaporated, concentrated and crystallized. Since the pH value of the saturated boric acid solution at 95 ℃ is less than 3, the corrosion is very strong, and the dissolution corrosion of carbon steel and low alloy steel equipment is caused. The low raman cross section of water allows analysis of aqueous solutions that are not suitable for infrared absorption techniques. Almost any sample, whether solid, liquid or gas, can be analyzed without modification. Because of the fewer spectral bands in the raman spectrum, there is less likelihood of loss of resolution due to spectral band overlap in the mixture spectrum, and the raman spectrum has higher spectral resolution and narrower bandwidth than other spectrum-based methods (such as fluorescence and infrared spectra), quantitative analysis of analytes can be achieved based on the proportional relationship between raman signal intensity and analyte concentration.

Single Photon Avalanche Diodes (SPADs) are solid state sensors based on reverse biased p-n junctions, SPAD arrays have the advantages of high sensitivity, limited power consumption, large scale miniaturized chip format, no need for cooling in a wide temperature range, sub-nanosecond time gating, etc., the accumulation of avalanche current is perceived by front-end electronics by absorbing electron-hole pairs generated by a single photon, one digital pulse is output, the reverse voltage is switched from slightly below the breakdown voltage to above the breakdown voltage, and the synchronization signal from the laser is used to bias all SPADs under the grating to geiger mode (in which SPADs can detect a single photon) before raman photons reach the sample, with ease of time gating switching. The use of a laser in combination with a SPAD gated detector allows exploiting the emission time difference between raman scattering and fluorescence to collect only photons synchronized with the pulses, thus substantially removing the latter from the recorded spectrum.

The current method for improving the raman detection efficiency is to adopt a plurality of different lasers to emit different laser beams to irradiate different positions of a sample respectively, and the method can obviously improve the raman scanning imaging speed on the basis of keeping the advantage of high spatial resolution, but has the defects that each laser needs to be provided with a grating and a detector, and the plurality of lasers, the grating and the detector obviously greatly improve the construction cost of a raman detection system and are not suitable for popularization in a large range.

The current method for inhibiting fluorescence interference is a multi-wavelength frequency shift excitation differential Raman spectrum method, namely, two original Raman spectrums are obtained by respectively exciting a sample by using two lasers with small wavelength difference, the two original Raman spectrums are subtracted to obtain a differential spectrum, and the positions of Raman peaks are obviously changed due to the fact that the fluorescence spectrums do not move along with the tiny change of the wavelengths, so that the differential spectrum has no fluorescence interference, the original Raman spectrums can be recovered from the differential spectrum through algorithm processing, but the multi-wavelength excitation needs a plurality of stable lasers, even a tunable laser needs an additional device to ensure the stability of output wavelengths, the cost is high, the time and the labor are consumed, and the algorithm processing part is extremely complex, so that the method is also not suitable for large-scale popularization of a Raman detection system.

Disclosure of Invention

The utility model discloses a boric acid detection Raman spectrometer based on a plurality of small array SPAD detectors, which is characterized in that the small array SPAD detectors are placed at different positions after gratings are placed through characteristic wavelengths of boric acid and water, a laser is used for irradiating a sample solution from a nuclear power station, the small array SPAD detectors are matched for collecting Raman signals, and a computer is used for carrying out algorithm processing on the Raman spectrum of the sample solution, so that staff can conveniently analyze the boric acid content in the sample solution of the nuclear power station.

The utility model is realized by the following technical scheme: the boric acid detection Raman spectrometer consists of a laser (1), a neutral density filter (2), a laser collimating lens (3), a dichroic mirror (4), a focusing objective lens (5), a sample solution (6), a long-pass filter (7), a focusing lens (8), a slit (9), a cylindrical lens (10), a collimating lens (11), a diffraction grating (12), a focusing reflecting mirror (13), a first small array SPAD detector (14), a second small array SPAD detector (15), a Field Programmable Gate Array (FPGA) control circuit (16) and a computer (17); the method is characterized in that: the laser (1) emits laser to the laser collimating lens (3) after light intensity attenuation is carried out on the laser by the neutral density filter (2), then the laser reaches the sample solution (6) through the dichroic mirror (4) and the focusing objective lens (5), scattered photons from the sample solution (6) pass through the dichroic mirror (4), the long-pass filter (7), the focusing lens (8), the slit (9), the cylindrical lens (10) and the collimating lens (11) and then reach the diffraction grating (12), the scattered photons are dispersed by the diffraction grating (12), the raman light from the diffraction grating (12) is focused on the first small array SPAD detector (14) and the second small array SPAD detector (15) respectively by the focusing mirror (13), the signal acquisition and the processing are carried out on the small array SPAD detectors by the Field Programmable Gate Array (FPGA) control circuit (16), the raman spectrum of the sample solution (6) is obtained by carrying out algorithm processing on received data, the raman spectrum of the sample solution (17) is compared with the standard raman spectrum of boric acid and water, so that staff can analyze the boric acid content in the sample solution, the raman spectrum is conveniently, and the problem of a single large array detector is solved by using a plurality of small array detectors instead of large array detectors.

The neutral density filter (2) is used for attenuating the laser beam emitted by the laser to a power level suitable for the sample solution so as to reduce the damage of the excitation light to the sample solution.

The laser collimating lens (3) is used for collimating laser beams emitted by the laser, so that the interference of stray light is reduced.

The focusing objective (5) focuses the laser light from the dichroic mirror (4) onto the sample solution (6) and collects raman and fluorescence scattered by the sample solution (6) at 180 °, as well as rayleigh scattered excitation light.

The dichroic mirror (4) is used for transmitting stokes, raman and fluorescence and reflecting a large part of the excitation light.

The long-pass filter (7) is used for providing a Rayleigh/Raman high rejection ratio, and Rayleigh lines can be almost completely filtered out.

The first small array SPAD detector (14) and the second small array SPAD detector (15) are integrated with a time-to-digital converter (TDC) for measuring the arrival time of the backscattered raman photons (reflection configuration of zero source-to-detector distance).

The two cylindrical lenses (10) and the collimating lens (11) with different curvature radiuses replace the traditional spherical collimating lens to collimate the light passing through the slit in the meridian direction and the sagittal direction respectively, so that the condition of broadband correction astigmatism is satisfied.

The purpose of the diffraction grating (12) to diverge scattered photons is to position the first small array SPAD detector (14) and the second small array SPAD detector (15) to correspond to the standard raman spectral wavenumber ranges of boric acid and water, such that the first small array SPAD detector (14) and the second small array SPAD detector (15) perform targeted raman spectral measurements of the sample solution (6).

The Field Programmable Gate Array (FPGA) control circuit (16) is used for completing control of the small array SPAD detectors and reading data from the small array SPAD detectors, so that communication between the computer and the small array SPAD detectors is realized.

Boric acid detection Raman spectrometer based on multiple small array SPAD detectors

Compared with the prior art, the utility model has the advantages that: the small array SPAD detectors replace a single large array detector, and are respectively arranged at positions which can receive Raman peak signals of boric acid and water after being arranged on the grating, so as to detect whether the sample solution contains boric acid or not, and the boric acid in the sample solution is quantitatively analyzed through the Raman peak intensity of the boric acid in the sample solution by combining data processing of a computer. The method is beneficial to systematically managing the equipment corrosion state of the nuclear power station while reducing the development cost of the Raman spectrometer, achieves the purposes of improving the safe operation capacity of the nuclear power station and saving the cost, has very strong innovation and practical value, and has wide application prospect.

Drawings

Fig. 1 is a schematic structural diagram of a boric acid detection raman spectrometer based on a plurality of small array SPAD detectors.

Fig. 2 is a standard raman spectrum of boric acid and water.

Detailed Description

As shown in fig. 1, the boric acid detection raman spectrometer based on a plurality of small array SPAD detectors emits laser light through a laser (1), light intensity attenuates through a neutral density filter (2), then the laser light enters a laser collimating lens (3), then the laser light passes through a dichroic mirror (4) and a focusing objective lens (5) to reach a sample solution, scattered photons from the sample solution pass through the dichroic mirror (4), and the same dichroic mirror (4) can transmit stokes, raman and fluorescence in back scattered light from the sample solution (6) and reflect most of excitation light. The collected light passes through a long-pass filter (7) to remove the excitation light (the filter only transmits the wavelength longer than the laser wavelength), and passes through an incidence slit (9) with a good slit width after being focused by a focusing lens (8), the light enters a cylindrical lens (10) after passing through the slit (9), the light is collimated on a sagittal plane, and then enters a collimating lens (11), and the light is collimated on a meridian plane. The fully collimated light is incident to a diffraction grating (12), the light with different wavelengths is separated by angle under the action of the light splitting of the grating, and finally the light is imaged on a first small array SPAD detector (14) and a second small array SPAD detector (15) through a focusing reflector (13). The SPAD detector has integrated thereon a digital time converter TDC (one channel per spectral point) for measuring the arrival time of backscattered raman photons. A Field Programmable Gate Array (FPGA) control circuit (16) collects and processes signals of a plurality of small array SPAD detectors, and a computer (17) performs algorithm processing on the received data to obtain Raman spectra of a sample solution.

As shown in FIG. 2, the standard Raman spectra of boric acid and water obtained by irradiating a boric acid solution with a boric acid concentration of 6000ppm with 532nm pulse laser for 35s and 10 times, wherein the Raman peaks of boric acid and water are respectively 878cm ^-1 (558 nm) and 1635cm ^-1 (583 nm) the boric acid content of the sample solution can be detected and analysed by comparing the raman spectrum of the sample solution with the standard raman spectra of boric acid and water.

Claims (4)

1. Boric acid detection raman spectrometer based on a plurality of array SPAD detectors comprises a laser (1), a neutral density filter (2), a laser collimating lens (3), a dichroic mirror (4), a focusing objective lens (5), a sample solution (6), a long-pass filter (7), a focusing lens (8), a slit (9), a cylindrical lens (10), a collimating lens (11), a diffraction grating (12), a focusing reflecting mirror (13), a first array SPAD detector (14), a second array SPAD detector (15), a Field Programmable Gate Array (FPGA) control circuit (16) and a computer (17), and is characterized in that: and selecting a first small array SPAD detector and a second small array SPAD detector to perform targeted Raman spectrum measurement on the sample solution, and reading out signals to a computer through a field programmable gate array control circuit.

2. The boric acid detection raman spectrometer according to claim 1, wherein: the plurality of small array SPAD detectors are used for replacing a single large array detector, so that the development cost of the Raman spectrometer can be obviously reduced.

3. The boric acid detection raman spectrometer according to claim 1, wherein: the positions of the first small array SPAD detector and the second small array SPAD detector correspond to the characteristic peak wave number positions of boric acid and water respectively, and the boric acid content in the sample solution can be accurately detected according to the strength of the Raman signal.

4. The boric acid detection raman spectrometer according to claim 1, wherein: the two cylindrical lenses and the collimating lens with different curvature radiuses replace the traditional spherical collimating lens to respectively collimate the light passing through the slit in the meridian direction and the sagittal direction, thereby meeting the condition of broadband correction astigmatism.