Direct detection and precise isotope analysis of individual particles in suspension by single particle mode MC-ICP-MS.

In this work, plutonium aerosol generated from a plutonium reprocessing facility is filtered by a six-stage High Efficiency Particulate Air (HEPA) filter system and analyzed in laboratory within a week. Through on-line monitoring of number concentration of particles above 10 nm by a commercial condensation particle counter and off-line monitoring of 239Pu activity concentration by 242Pu isotope dilution Inductively-Coupled Plasma Mass Spectrometry (ICP-MS), it is confirmed that the HEPA filter system works properly during the field operation. Direct determination of plutonium aerosol by two types of ICP-MS, Finnigan ELEMENT ICP-MS and Nu MC-ICP-MS, has been conducted. The results show that the detection limits of ELEMENT and Nu for plutonium concentration are 5.0 × 10−3 Bq/m3 and 5.5 × 10−4 Bq/m3, respectively. Plutonium concentrations in the filtered gas samples are on the order of 2.0 × 10−2 Bq/m3 while the blank value is 5.7 × 10−3 Bq/m3. It's discovered that some plutonium nanoparticles have penetrated the six-stage HEPA filter system. This phenomenon is also observed in the repeated works of last two years. The size of the penetrated plutonium nanoparticles is investigated by ELEMENT in single particle mode. The preliminary results indicate that the penetrated plutonium nanoparticles are smaller than 10 nm and assume the form of 239PuO2.

A technique for direction introduction and on-line quantitative analysis of aerosol particle by ICP-MS has been developed. Fast determination of Pu-239 concentration in aerosols based on Pu-242 aerosol particle addition calibration method and sampled by steel cylinders samplers from nuclear environment has been conducted. Results show that detection limit for Pu-239 concentration is 1.4 x 10(-3) Bq/m(3). The concentrations in these aerosol samples are between 3.1 x 10(-3) and 1.2 x 10(-2) Bq/m(3), all of which are at least one order of magnitude lower than the statutory tolerance.

为满足环境气溶胶在线进样的要求,改善电感耦合等离子体质谱计(Inductively coupled Plasma Mass spectrometry,ICP-MS)对粒子中待测核素的探测限,研制出一套具有低流量、低压降特点的狭缝虚拟撞击器,可作为气溶胶在线富集进样系统的关键部件与ICP-MS联用.本文介绍了该狭缝虚拟撞击器的研制情况:首先由ICP-MS的进样条件,根据经验公式完成了理论设计,确定进样流量为11 L/min,强流与弱流的流量比为10,喷射狭缝宽度为1 mm,长宽比为10;然后用计算流体动力学软件Fluent 对上述结构内部的流场和粒子运动径迹进行了数值模拟,考察了喷射狭缝与收集狭缝的间距G、收集狭缝的宽度Wc及其进口曲率半径的加工偏差对收集效率的影响,得到了较优化的取值范围:G取1.0～1.2mm,Wc取1.4～1.6 mm,此时的切割粒径D50约2.5μm;加工出狭缝虚拟撞击器的原型装置,对其分别用室内空气气溶胶和荧光素钠标记的单分散油酸粒子进行富集性能测量.实测结果表明:空气动力学等效直径在2.5～5μm范围内的粒子浓度得到了明显富集,5μm的粒子的富集因子达到极大值7.

When more than two elements on the filament of a thermal ionization mass spectrometer(TIMS) are vaporized,the element ratios in the vapor depend on the filament temperature.The ion current ratios of different mass numbers vary with the temperature,which is dominated by the filament current.With the presence of isobaric interference,the method of isotopic analysis by TIMS is established in the present paper and applied to determine the natural lutetium abundance in the solutions,in which ytterbium and lutetium are mixed by ratio of 1 000∶1.The measured isotope ratio of lutetium is in good agreement with the standard value.Likewise,the concentrations of 173Lu and 174Lu in the real samples produced through bombardment of ytterbium target by proton beam are determined by ID-TIMS.The relative uncertainties of concentrations are 0.45% and 1.1%,respectively.

The influences of some relevant parameters on resonance ionization efficiency in the recent laser pulse time-delayed scheme were analyzed with the framework of time-dependent Schrdinger equation.As a versatile example,the feasibility of this scheme applied to lutetium isotopic analysis by Laser Resonance ionization Spectrometry(LRIMS) was discussed.The results show that this scheme is infeasible for isotopic analysis utilizing broad-band lasers by LRIMS because the Rabi frequency between transition levels can not match well in the presence of hyperfine structures.On the base of theoretical analysis,the method combined this new scheme with narrow-band lasers excitation was presented in order that accurate isotopic ratio could be measured by LRIMS.

Technique of lutetium isotopic analysis by laser resonance ionization mass spectrometry(LRIMS) was developed in the presence of isobaric interference. In the case of real sample, the elemental selectivity was better than 8×105, and the detection efficiency was 8.3×10-5. The technique of wavelength scanning method was set up in order that the accurate isotopic ratio could be determined. And the numerical computational method was provided to calculate the correct factor of isotopic ratio. Using this technique, the isotopic ratio measured by LRIMS is in good agreement with standard value measured by TIMS.

An equation has been established for the transmission of optical parameters in a two-lens system using the Gaussian optical theory, and in the light of the structural features of NINT3000 laser resonance ionization mass spectrometer, an optical system and a laser path adjustment device were then designed using the above equation to achieve precise location and focusing of laser beam in the ion source cavity. The radius of the laser focal spot is 160 μm, and the adjusting precision being 10 μm. The system has now been installed in the laser resonance ionization mass spectrometer, and the homochromatic two-photon resonance ionizations of lutetium has been realized.

介绍了激光共振电离质谱学实验中的两台YAG激光器的结构原理及其能量转换机制,并结合实际使用情况对影响其输出特性的因素进行了分析,其输出特性包括:激光器的阈值;激光器的输出能量、效率和最佳透过率;激光器输出光束的稳定性、光谱特性、偏振特性和方向性等.激光器调试结果达到了设计指标.

The dependences of laser-induced isotopic discrimination effect on some of laser parameters were studied by the experimental and theoretical methods. This effect mainly stems from the discrepancy of the second-step transition probability between different isotopes. The method by which this effect is lessened or eliminated is given. The isotopic ratios of nature lutetium sample are determined by this method. The experimental results present that the degree of the laser induced isotopic discrimination of lutetium isotope can be lessened by this method.

本文在速率方程基础上通过数值模拟方法,对镥的激光共振电离通道:5d6s22D3/2(573.655nm)→5d6s6p4F3/2(642.518 nm)→6s6p24P1/2(643.548 nm)→Autoionization state的激光诱导同位素选择性进行了研究.在实际实验条件下用这一方法计算得到的激光波长对激光诱导同位素选择性的关系与实验结果相符合.探讨了在偏振激光作用的情况下各种激光参数(波长、带宽和激光强度)对激光诱导同位素选择性的影响,并提出了在一定实验条件下激光共振电离质谱计较为准确地测定同位素比值的方法.这一理论方法,同样适用于研究其它元素的激光共振电离同位素选择性和选择激光同位素分离电离通道.

激光共振电离光谱是一种十分适合于高能量区重元素复杂原子结构研究的技术.为寻找铈原子最佳的共振电离通道,利用这一技术对铈原子奇宇称高激发态进行了研究.在32 042～34 575 cm-1范围内,用两步共振激发和非共振电离方法,首次观察到了83条铈原子奇宇称高激发态能级,测量了这些新能级的能量和给出了可能的总角动量J值.

A number of light beam combination methods are described, such as sheet glass, right-angle prismwith unfilled corner, small-angle total-reflection prism, filter, prism polarization beam splitter, flat plate polar-ization beam splitter, multi-facet reflector, iceland-spar OE crystal with double windows. Each has its advantages,disadvantages, and its particular usable conditions. The best one is identified for our particular purpose.