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Uranium content measurement is very important to nuclear material accounting and product quality control in nuclear bulk facilities. It needs high accuracy and precision. In this work, 3 different measurement steps from 2 analytical standards GB 11841—1989 and ASTM C1267-17, which were uranium content test methods by iron(Ⅱ) reduction followed by chromium(Ⅵ) titration, were discussed by simulated experiments and following uncertainty evaluation. The results show that, the total uncertainties of the 3 steps are all lower than 0.1%, which is the international target value of uranium content measurement by redox potential titration method. The step for 2.3 g sample of GB 11841—1989 is more suitable to sign value measurement in reference material production, because of its lowest uncertainty. In routine testing works, the step for 0.20-0.25 g sample of GB 11841—1989 is better in sample weighting, the step of ASTM C1267-17 is better in titration and potassium dichromate solution preparation.

Thermal ionization mass spectrometry (TIMS) is a well-established instrumental technique for accurately analyzing isotopes of elements with low first ionization potential. However, the measurement accuracy is affected due to the existence of the mass fractionation effect. Generally, applying the external standard method or total evaporation method is the most common way to correct the mass fractionation effect. Total evaporation (TE） technology is the most conventional method for uranium major isotope ratio measurement (235U/238U) using TIMS. However, due to the strong peak tailing of the major isotopes and other factors, the measurement precision and accuracy of minor isotope ratios (234U/238U and 236U/238U) are relatively low. In this study, the modified total evaporation (MTE) method for highly precise measurement of uranium isotopes ratios by TIMS was developed based on the research of dynamic heating procedures, dynamic and static receiving procedures, peak tailing correction, efficiency calibration of collectors and mass discrimination calibration. The accuracy and reliability of the MTE method were verified with different reference materials. The experiment results showed that the yield of uranium oxide should be monitored and the related parameters should be precisely controlled to reduce the yield of uranium oxidation during measurement. This action could guarantee the effectiveness of the MTE measurement and improve the uranium samples utilization. The initial strength of 187Re+ played an important role in the ionization efficiency of uranium and the yield of uranium oxide. The optimal signal of 187Re+ should be set in the range of 0.17-0.22 V. When uranium samples with 2% 235U isotopic abundance were measured by the MTE method using TIMS, the measurement precisions of 235U/238U, 234U/238U and 236U/238U were 0.024%, 0.06%, and 0.19%, and the bias between the measured value and reference value were 0.025%, 0.19%, and 0.38%, respectively. Compared to the TE method, the MTE method showed the same precision for the 235U/238U ratio measurement. As for the MTE measurement of 234U/238U and 236U/238U ratios, the major uranium isotopes (235U and 238U) were used as an internal standard to overcome the mass fractionation effect. When the tailing effects were eliminated, the measurement precisions of 234U/238U and 236U/238U ratios were improved by 5 to 10 times. As for sample amount, the TE method generally requires the uranium amount of less than 1 μg, while 5 μg is required for the MTE method.

For temperature drift in hypervelocity photoelectric modulation interferometer, a control model of temperature compensation is presented including voltage and phase compensation. First, according to the similar and modeling theory, an equivalent circuit model of mechanical properties of hypervelocity photoelectric modulation interferometer was established, the impact of temperature drift on its resonance frequency was analyzed, a mathematical model was set up, which contains drive voltage, frequency and resonance frequency, and the control method was determined for high optical path difference to get steady. Then, a digital method including voltage and phase compensation is given for optical path difference deviation control, which merges the DPLL and program of voltage and phase compensation. Finally, the control method was tested through experiment system. A test between drive control system including voltage and phase compensation and traditional drive control system was executed, using a laser doppler vibrometer to record the amount of change in optical path difference within 3 hours. Results show that the optical path difference deviation caused by temperature drift in long term is reduced by about 50%.

In the Fourier transform infrared spectrometers the interferograms are usually sampled by the means of the single-side beyond zero path difference and the interferograms are asymmetric. These phase-corrected technologies are researched and improved in the present paper. In the Mertz method which requires apodization to be higher, the interferograms are apodized by these asymmetric windows so that the width of the main lobe increases and spectral resolution reduced. In order to solve these problems, a method which combines the Mertz and Forman methods is presented in the paper. In the method a double-side interferogram is constructed by the mirrored processing of the single-side interferogram beyond zero path difference, followed by the symmetric apodization, fast Fourier transform (FFT) to rebuild spectrum. And in the method high resolution phase spectrum is computed by the symmetrization of double-side interfergram to improve the phase-correction accuracy. In the experiment, these asymmetric window functions have the lower resolution compared with these symmetric window functions. And the spectrum which is acquired by the improved phase corrected method is compared with the spectra which are acquired by the Mertz and Forman methods, and the improved method has less error than Mertz, less computation than Forman, and the spectral resolution achieved 2 cm(-1).

A non-dispersed infrared (NDIR) methane gas sensors system based on infrared absorption spectrum theory was designed according to single light beam and double wavelengths technology. In the system, an infrared LED IRL715 serving as the light power, a absorptive gas cell with the function of dust-proof and damp-proof and a pyroelectric detector LIM-262 are composed of optical probe. Signal condition uses active filter circuit and differential amplifier, and binomial expression fits the relation curve between methane concentration and voltage, which realizes accurate detection of gas concentration. Experiment approved that the sensor system with good consistency and applicability can detect the range of 5% methane reliably and have 0.5% of the sensitivity, possessing the conditions for industrial applications initially.

This paper introduced the application of support vector machines (SVM) regression method based on kernel function optimized by the rough set in the infrared spectrum quantitative calculation. According to kernel function with the rough set classification's method, the spectrum data (characteristic wavelength section) is optimized. The kernel function leads support vector machines, and the SVM project the two-dimensional room to the multi-dimensional room, and calculate the concentration of every kind of gas in multi-component pollution gas. By using two kinds of typical spectrum data processing algorithm to make the contrast, the comparison of five kinds of gaseous mixture various proximate analysis is carried out, and when the spectrum separable rate is high, the predicted values of the three methods approach the normal value, and the average error is smaller than 0.13; but when the spectrum separable rate is low, the RS-SVM predicted value is more precise than the first two kinds. Experimental data show that the consequence is better when there are more testing types, and the precision and operation of this method is of more remarkable superiority.

Methane explosion accidents occur frequently, and accurate and real-time detection and early warning of methane concentration are the effective means of preventing these accidents. The research was based on the spectrum absorption properties of methane, and a near-infrared tunable DFB laser diode of 1.65 microm wave band was used. With the mode-hopping features of laser diode, a differential absorption of double-wavelength and single-fiber optical sensor network was designed. Sixteen methane sensors were multiplexed in this system with space division multiple access technology and optical switch, and the key technologies of anti-dust in gas absorption cell were researched. All signals were gathered by the PCI data acquisition card, and information of each way was analyzed and displayed with virtual instrument. The results of experiment show that the method can reach the sensitivity of 0.05% even without using a phase-locked amplifier and the absorption light path is only 10 centimeters. Long-time accuracy and stability of all sensors could meet the practical demands, and the response time of each sensor was less than 1 seconds. With the replacement of lasers, the network can be used for the real-time detection of other gases.

Unlike the Brillouin scattering, the anti-Stokes Raman scattering i n optic fiber is unrelated with the strain, but isonly the function of the absolute temperature. The frequency shift caused by Raman scattering is about 13.95 Thz. So the Raman scattering is easier to be picked up than Brillouin scattering. It has certain advantage while being used as the signal of the distributed optic-fiber temperature sensor. But it is weaker than the Brillouin scattering, the peak photocurrent produced in APD is of the order of nA, near or even lower than the noise current of the APD. The N/S after being photo-electric transformed is usually lower than 1. The means of Fourier transform and wavelet transform is not effective in dealing with such kind of signal. Through analyzing the feature of the anti-Stokes Raman scattering signal and using the wavelet, the anti-Stokes Raman scattering signal after being cumulated & averaged was picked up. The supersensitive detecting below the "noise current" of the APD was carried out with the senstivity: 0.104 nA x K(-1), lower than the "noise current" of the APD 2 classes.

A miniature static Fourier transform spectrometer (MSFTS) as the component of coherent discriminating laser warning receiver (CDLWR) was designed in the present study by using a modified wedge interfering etalon (MWIE), a linear charge couple device (CCD) and a fast digital signal processor (DSP). The MSFTS possesses some advantages such as small volume, low cost, high speed, stable performance and good signal to noise ratio. MSFTS can detect the spectrum of HIPL, the short pulse width of laser is about 10 ns, and the spectrum scope is from 400 to 1 100 nm. The key element of MSFTS is MWIE which is composed of two triangle prisms, one of which is a right angle prism with two equal acute angles of 45 degrees, another prism has no right angle, one of the acute angles is 45 degrees, and another is slightly smaller than 45 degrees. The long sides of the two prisms were bonded by transparent glass glue, and the adhesive surface is plated with special material which serves as a beam splitter (BS). The incident laser will be split into two equal strength beams with continuously changing optical path difference, the two beams will interfere and form interferogram which will be focused by a cylinder as a line and transformed as s electronic signal by CCD. The electronic signal was processed by using a DSP, and finally we obtained the spectrum of the incident hostile laser by applying fast Fourier transform (FFT). We have established the experiment system of MSFTS, and used the system and the spectrometer Q8344A made by Advantest Company in Japan to measure the spectra of the seven lasers with different central wavelengths: 635, 650, 670, 780, 808, 850 and 980 nm. The measurement result shows that the worst wavelength resolution is 8. 845 nm at 1 100 nm, the best wavelength resolution is 1.170 nm at 400 nm, the relative average error of central wavelength is 0.269 nm, the absolute average error is 0.919 nm and signal-to-noise ratio of our experiment system is better than that of Q8344A.

In order to countermeasure increasingly serious threat from hostile laser in modern war, it is urgent to do research on laser warning technology and system, and the sensitivity and signal to noise ratio (SNR) are two important performance parameters in laser warning system. In the present paper, based on the signal statistical detection theory, a method for calculation of the sensitivity and SNR in coherent detection laser warning receiver (LWR) has been proposed. Firstly, the probabilities of the laser signal and receiver noise were analyzed. Secondly, based on the threshold detection theory and Neyman-Pearson criteria, the signal current equation was established by introducing detection probability factor and false alarm rate factor, then, the mathematical expressions of sensitivity and SNR were deduced. Finally, by using method, the sensitivity and SNR of the sinusoidal grating laser warning receiver developed by our group were analyzed, and the theoretic calculation and experimental results indicate that the SNR analysis method is feasible, and can be used in performance analysis of LWR.

It is the key content of laser warning to reliably and real-time detect the type and characteristic parameters of incident laser. Coherent detection technology detects the information based on the coherence of laser, and is a kind of effective detection technology. In order to detect the incident laser's spectrum, a kind of device for laser detecting and real time spectrum measurement was designed, which measures the laser spectrum on the bases of coherent detecting technology, Fourier optics and optical signal processing. Using compact and static Mach-Zehnder interferometer as the coherent detection components, it can restrain the background light efficiently. The non-scanning mechanical parts allow fast spectrum detection, and narrow laser pulse can be detected. The real-time signal processing is realized by DSP and multi-channel frame subtraction technology to wipe off the background light, detect the laser and measure its spectrum. The result indicates that, using Mach-Zehnder interferometer and multi-channel frame subtraction technology can realize the laser pulse detection, and improve the measuring precision efficiently; 10 ns laser pulse can be detected and the wavelength measuring error is less than 10 nm.

Twelve camphor (cinnamomum camphora) tree bark samples were collected from Hiroshima and Kyoto, and the matrix element composition and morphology of the outer surface of these camphor tree bark samples were studied by EDXS and SEM respectively. After a dry decomposition, DOWEX 1-X8 anion exchange resin was used to separate uranium from matrix elements in these camphor tree bark samples. Finally, 235U/238 U isotope ratios in purified uranium solutions were determined by MC-ICP-MS. It was demonstrated that the outer surface of these camphor tree bark samples is porous and rough, with Al, Ca, Fe, K, Mg, Si, C, O and S as its matrix element composition. Uranium in these camphor tree bark samples can be efficiently separated and quantitatively recovered from the matrix element composition. Compared with those collected from Kyoto, the camphor tree bark samples collected from Hiroshima have significantly higher uranium contents, which may be due to the increased aerosol mass concentration during the city reconstruction. Moreover, the 235 U/23.U isotope ratios in a few camphor tree bark samples collected from Hiroshima are slightly higher than 0.007 25.