An EBIS for charge state breeding in the SPES project

The ‘charge state breeder’, BRIC (breeding ion charge) is in construction at the INFN section of Bari (Italy). It is based on EBIS scheme and it is designed to accept radioactive ion beam (RIB) with charge state +1 in a slow injection mode. This experiment can be considered as a first step towards the design and construction of a charge breeder for the SPES project. The new feature of BRIC, with respect to the classical EBIS, is given by the insertion, in the ion chamber, of a rf-quadrupole aiming at filtering the unwanted masses and then making a more efficient containment of the wanted ions. In this paper, the breeder design, the simulation results of the electron and ion beam propagation and the construction problems of the device will be reported.     

Performance of YSZ oxygen sensors protected by electrochemical filters

The performance of nernstian Yttria Stabilized Zirconia (YSZ) oxygen sensors can be seriously affected when in contact with some aggressive industrial furnace atmospheres. Longer life time can be obtained for sensors protected with electrochemical filters. The most relevant parameters determining the protected sensor performance are the ratio between the sensor and the filter oxygen electrochemical permeabilities, and the volume of the electrode protection chamber. The ratio between materials electrochemical permeabilities determines the sensor oxygen activity applicability domain and the deviation between the effective (steady state) and desirable (theoretical) sensor reading. The protected chamber volume will influence the time response behavior. Theoretical predictions on sensor performance are compared with experimental data obtained for protected YSZ sensors conceived for moderately oxidizing atmospheres (1 Pa<Po₂<21 kPa). Two different cases are studied including one single phase and one composite (ionic + electronic conductor) electrochemical filter. Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11–18 Sept. 1994.     

激光加速度传感器的理论研究

提出了一种新型加速度传感器的设计理论。该传感器设计以角锥棱镜作为惯性摆，利用光学干涉原理，可以实现对运动物体的二维加速度测量。对该传感器进行了系统的理论研究，给出了二维加速度激光传感器设计参量选取的一般规律，并给出了实验的初步结果。     

Design and operation of a double-fiber displacement sensor

Design and operation of a double-fiber sensor for displacement measurements are reported in this study. In this arrangement, one fiber transmits the laser light to the target and the second one receives the light reflected off the target and transmits to a photodetector. Utilizing inexpensive plastic optical fibers offers advantages such as higher reflexability and more robustness at a reasonable cost, which are required for some applications. The novelties of the reported design are compactness of the fiber probe, flexibility, long dynamic range (22 mm), and it is possible to use the source and the detector at the same side. The displacement of the target causes the intensity modulation and such a power variation is the base of sensor operation. Measurements for the metallic and non-metallic surfaces are performed and the results for aluminum, copper, and bronze sheets are presented here. Our results indicate that the sensitivity is highest for the plane mirror (288.8 mV/mm), high for the shiny metallic surfaces (230.6 mV/mm), but it can be used for other surfaces with a reasonable sensitivity. Important parameters of the sensor such as reproducibility (1.0%) and hysteresis effect (1.8%) are also investigated for this device. The theoretical formulation of the sensor operation is also developed and the computed results are compared with the experimental ones. The obtained experimental respond curve agrees well with the theoretical one, which verifies the successful operation of the proposed sensor system for precise displacement measurements.     

A closer look at the Debye-Hückel theory and its modification in the SiS model of electrolyte solutions

So far, it has rarely been acknowledged that the initial version of the Debye-Hückel theory provided for different mean distances of closest approach to different ions, but the final formulation of the theory was presented with a single geometric parameter for all the ions in a solution. Here the initial design is recalled by deriving the Debye-Hückel equation for the mean activity coefficient in binary solutions with two geometric parameters for the two ion species present and, in the course of this, looking critically at details of the derivations. The equation is compared with the SiS model of electrolyte solutions (Mol. Phys. 108, 1435 (2010)) both in theoretical aspects and as regards their abilities to reproduce experimental data. It is found that the SiS model, as distinct from the original theory, is thermodynamically inconsistent in that it derives the mean activity coefficient from chemical potentials of ions, which do not represent partial derivatives of a single free-energy function of the solution. In addition, arguments are set forth that the geometric parameters in both equations cannot be interpreted in terms of a realistic structural chemistry. The results of comparing the two equations with experiment are found to bear out this view.     

Study on the simplified phase-shifting digital holographic microscopy

In this paper, a new simplified technique for effectively eliminating the zero order and the conjugate virtual image in digital holographic microcopy, which makes use of two-step phase-shifting method of just recording two holograms and an intensity image of object wave, is proposed. Meanwhile, combined with the principle of making full use of spatial bandwidth of the CCD sensor by in-line lens-less Fourier holographic recording geometry, the theory and experimental methods to increase the resolution of the reconstructed image in digital holography by using phase-shifting technique are detailedly analyzed. At end, the validity and availability of this technique has been demonstrated through the off-axis and in-line Fourier transform recording geometry. The study provides some theoretical and experimental guidance for the design and operation of a digital holographic microscopy system.     

Influence of the size,geometry and temporal response of the finite piezoelectric sensor on the photoacoustic signal: the case of the point-like source

Most photoacoustic (PA) work assumes a point-like detection of generated pressure waves; this assumption results in important differences between predicted and experimental signals, as shown in this paper. We used the geometry of a real sensor in the theoretical signal generation through the discretization of the sensing surface, considering each element as a point-like sensor. We modeled the interaction between the wavefront and the real sensor, starting from a well-known PA pressure relation for a point-like source and punctual detection. We obtained the electrical response of the real sensor experimentally and modeled it as a summation of Gaussian functions. The impulse response was convolved with the total PA pressure to obtain the theoretical PA signal. We analyzed the dependence of the source-sensor distance on the discretization size. Then the predicted signal and experimental data were compared for two different frequency response transducers. We found differences in shape and temporal width of simulated PA signals for point-like-source/punctual-detection model and for point-like-source/finite-sensor model.     

Contrôle thermique de parois de chambre de combustion. Banc d'essai du laboratoire aquitain de recherche en aérothermique

Thermal control of combustion chamber walls. LARA's test bench. Convective heat transfer along the wall of a combustion chamber is a major source of concern for a gas turbine engine manufacturer like Turboméca. This topic led to a joint research project with the University of Pau : to this end, a specific test bench with up-to-date means of measurement (IR thermography, laser doppler velocimetry) was created. An initial literature study had shown that multi-hole cooling had not been previously studied with a geometry design close to the real case. The present test facility provides and controls the dynamic and thermal parameters of a combustion chamber and the multi-hole cooling was set up on a flat plate simulating the wall chamber. This plate is submitted on one side to the hot gases resulting from combustion and on the other side to the cooling air flow. Dynamic and thermal entry conditions of the hot and cold flows were carefully controlled and are now presented. The wide possibilities of the testing facility have been explored offering scopes for other experimental studies.     

Development and investigation of a metal ion source for accelerators

The design and operation of a new spray-type metal ion source are described. The source is built around a plasma emitter containing metal ions and using a two-step glow discharge with double plasma compression. The necessary temperature of electrons in a discharge chamber is reached by distributing the discharge power without heating. The design of the discharge chamber is optimized. The first set of experimental data for the mass-and-charge composition of a beam generated by this source is presented.     

Near-infrared methane sensor based on a distributed feedback laser

In this article, a near-infrared methane detection system using tunable diode laser absorption spectroscopy technology was designed and implemented. The distributed feedback laser was driven by a self-developed temperature and current controller to allow scanning the selected absorption wavelength at 1654?nm. Laser temperature fluctuation was lower than 0.01%, and the output emission wavelength was linear and stable. The emitted beam passed a reflective gas chamber and was received by the Indium Gallium Arsenide photodiode detector. Through a data acquisition card, a digital lock-in amplifier was developed to extract the second harmonics with real-time monitoring and adjustment. Based on Allan deviation analysis, the limit of detection was about 48?ppm with a path length of 30?cm, at an integration time of 6?s. The experimental results revealed a maximum detection error of less than 3% at a gas concentration higher than 100?ppm. The fluctuations rates in long-term (9?hr) stability measurements for 1?×?10³?ppm and 1?×?10⁴?ppm methane samples were 0.8% and 0.48%, respectively, indicating good stability for the sensor. In the control module design, compared with previous reports on methane detection systems, the current system uses a self-developed temperature controller, a current driver and a signal processor, to allow real-time display and adjustments. The potential for adjustable wavelength scanning is available for multi-gas detection based on a single detection system.     

Surface enhancement of molecular ion H_2~+ yield in a 2.45-GHz electron–cyclotron resonance ion source

High current hydrogen molecular ion beam is obtained with a specially designed stainless steel liner permanent magnet2.45-GHz electron–cyclotron resonance(ECR) ion source(PMECR II) at Peking University(PKU). To further understand the physics of the hydrogen generation process inside a plasma chamber, theoretical and experimental investigations on the liner material of the plasma chamber in different running conditions are carried out. Several kinds of materials, stainless steel(SS), tantalum(Ta), quartz, and aluminum(Al) are selected in our study. Experimental results show that stainless steel and tantalum are much better than others in H~+_2 generation. During the experiment, an increasing trend in H~+_2 fraction is observed with stainless steel liner after O_2 discharge inside the ion source. Surface analyses show that the roughness change on the surface after O_2 discharge may be responsible for this phenomenon. After these studies, the pure current of H~+_2 ions can reach 42.3 mA with a fraction of 52.9%. More details are presented in this paper.     

Cavity-enhanced absorption spectroscopy for shocktubes: Design and optimization

Cavity-enhanced absorption spectroscopy (CEAS) has generated much interest in shocktube kinetics studies because of its recent success in achieving improved sensitivity and high time resolution with robust optical alignment. While recent progress demonstrated experimental schemes including off-axis scanned-wavelength approach and on-axis ps-pulsed laser approach, that both successfully suppressed the laser-cavity coupling noise, this paper develops a theoretical model to predict the CEAS sensor performance that can be used as a design tool applicable to more generalized cases. The method models the optical field in the cavity based on the decentered Gaussian beam model, from which the cavity transmission spectrum and the laser-cavity coupling noise can be numerically calculated. The simulation results predict sensor performance for different cavity configurations and laser characteristics, including various degrees of laser-cavity mode-matching, laser linewidths, scanning rates, and cavity filling conditions. Simulation with example wavelengths in the ultraviolet, near-infrared, and mid-infrared showed increasing mode-matched beam waist size for increasing wavelengths. An off-axis alignment scheme was found to be capable of suppressing the coupling noise by two orders-of-magnitude at a moderate laser linewidth of 1?GHz. Coupling noise level on the order of 1e-5 for scanned-wavelength off-axis alignment case with a narrowband mid-infrared laser was obtained by model calculation and agreed with experimental results within acceptable uncertainty range. The developed method can serve to guide future design and optimization of CEAS system in shocktube studies.     

Application of surface and normal ultrasonic waves for measuring the parameters of technical fluids: II. Density measurements

The effect of a fluid on the surface waves moving in a waveguide along its boundary with the fluid is considered. The effect of the shear and volume viscosities of the fluid on the damping coefficient of such a surface wave is estimated. It is shown that the effect of fluids may be neglected at a measurement accuracy of about 10^?3 if their shear viscosities are lower than 0.1 Pa s. At a higher viscosity, corrections that take into account the contribution of viscous losses to the measured damping coefficient of a surface wave should be introduced. A technique for calibrating a density sensor for low-viscosity fluids is described, and the densities of NaCl and saccharose solutions in distilled water are measured. The experimental results agree qualitatively with the theoretical estimates. It is noted that this method of measuring the longitudinal impedance of a fluid can use the same apparatus design in both the principle (pulsed) and the frequency range (1?C10 MHz) for measuring the density, both viscosities, the velocity, and the sound absorption coefficient of a fluid. This design almost coincides with the apparatus used in the means of nondestructive quality control of materials and articles.     

电磁监测试验卫星阻滞势分析器探测技术

依据电磁监测试验卫星的任务要求,自主研发了等离子体分析仪,首次实现电离层等离子体原位探测.作为等离子体分析仪的重要组成部分,阻滞势分析器主要用于探测电离层等离子体的密度、沿轨道方向漂移速度、温度以及成分等参数.阻滞势分析器传感器栅网材料选用铍铜,表面镀金处理,并通过仿真验证了多层栅网总透过率与理论计算的一致性.依据技术指标,详细设计了阻滞势分析器传感器的窗口半径、收集极半径、有效高度及扫描电压等参数.在电子学电路设计时通过前放电路三个可调量程的设计,保证了电路测量精度.在此基础上,借助意大利国家天体物理研究院行星际物理研究所的地面等离子体环境,完成了阻滞势分析器的等离子体环境测试.测试结果表明,该阻滞势分析器的性能指标满足设计要求,能够实现电磁监测试验卫星的任务需求.     

Ion source with electron ionization for a portable mass spectrometer

An ion source with electron ionization is considered. The charged-particle flow at the exit from this source has a cross section of ∼0.1 × 0.1 mm, an angle spread of 2° × 2°, a relative energy spread of <0.5%, and an energy range of 0.5–3.0 keV. This ion source is intended for systems where an ion beam is focused in two mutually perpendicular directions. The ion source design makes it possible to ionize a sample locally (in a volume of ∼10 mm³), where the concentration of the particles under study exceeds the concentration averaged over the volume of the vacuum chamber of the mass spectrometer by two to three orders of magnitude. The ion-optical properties of the source are numerically simulated, and the optimum parameters of the source are chosen. Examples of the application of the ion source are given for the mass-spectrometric determination of metal salts in aqueous solutions and of gases and volatile compounds in samples in various phase states.     

Dithiane Based Boronic Acid as a Carbohydrate Sensor in an Aqueous Solution at pH 7.5: Theoretical and Experimental Approach

Carbohydrate sensing in an aqueous solution remains a very challenging area of interest. Using the idea of covalent reversible interaction between boronic acids and the diol groups in carbohydrates enable us to design a carbohydrate sensor 1-thianthrenylboronic acid (1T), which has high selectivity towards fructose. To elucidate the sensing and binding properties of 1T with sugars, we have incorporated theoretical (DFT and TD-DFT) and spectroscopic techniques. For an optimized geometry, the complete vibrational assignments were done with FT-IR and FT-Raman spectra. Physiochemical parameters were obtained by implementing frontier molecular orbital (FMO) analysis. Further, excited state properties were determined by performing TD-DFT calculations in solvent and these properties were in good agreement with the experiment. The steady state fluorescence measurements with varying concentration of sugars, revealed that the fluorescence intensity of boronic acid is enhanced by studied sugars due to the structural modification. We also noticed remarkable changes in fluorescence lifetimes and quantum yield after adding sugars. The article also reports influence of pH on boronic acid’s fluorescence intensity with and without sugars. The fluorescence of boronic acid increases with the increase in pH. These changes are due to acid–base equilibrium of boronic acid and led us to estimate the pKa value of 7.6. All the theoretical and experimental evidences suggested that 1T can be used as a possible fluorescent sensor for fructose. In addition, 1T showed very good affinity for Cu²⁺ ion with K_a?=?150?×?10² M^?1, which suggests that 1T can also be used as a chemosensor for Cu²⁺ ions.

     

Brownian relaxation of magnetic nanoparticles in fluid: the effect of the solvent

A simple, environmentally friendly hydrothermal stripping route for synthesizing highly size-controlled spherical ferric oxide nanoparticles was developed that involved stripping ferric ion from iron-loaded organic phase. The particle size was found to be influenced by the initial concentration of iron in organic phase, stripping temperature and time, and a mathematical model about the size was established based on the experimental results and theoretical analysis. The model suggests that the process apparent activation energy of stripping iron from organic phase is 97.3? kJ·mol^?1, the energy of crystal growth is 51.6? kJ·mol^?1, and the synthesis of Fe₂O₃ is controlled by the crystal growth of embryo at low temperature (T < 590?K). The sizes calculated by the model comparatively accord with the experimental data and this provides a method for controlling the sizes.     

Optimizing and assessing the performance of an algorithm that cross-correlates acquired acoustic emissions from internally feeding larvae to count infested wheat kernels in grain samples

An algorithm was developed with optimizable parameters to match sounds from individual insects in grain by cross-correlating signals from an acoustic sensor array. The algorithm was optimized in a series of trials conducted in the sample chamber of an Acoustic Location ‘Fingerprinting’ Insect Detector (ALFID). The sample chamber was filled with uninfested wheat, except for a single kernel, which was infested with an immature rice weevil. This kernel was placed at a known location in the sample chamber. With analysis parameters optimized, the algorithm successfully detected the single insect in 100% of the trials. The algorithm's capability to count multiple insects was assessed by combining signals in data files collected from single insects into a set that represented sounds from a pair of insects. In these analyses, the algorithm correctly detected the two insects in 100% of combinations three sensor spacings apart, 100% of combinations two sensor spacings apart, and 70% of combinations one sensor spacing apart. Based on these results and the dimensions of the ALFID sampling chamber, the algorithm has a 90% probability of identifying two randomly located insects producing sounds in a wheat sample.     

Single-ended mid-infrared laser-absorption sensor for time-resolved measurements of water concentration and temperature within the annulus of a rotating detonation engine

A novel single-ended mid-infrared laser-absorption sensor for time-resolved measurements of water mole fraction and temperature was developed and deployed within the annulus of a hydrogen/air-fed rotating detonation engine (RDE). The sensor transmitted two laser beams targeting mid-infrared water transitions through a single optical port on the outer wall of the cylindrical RDE annulus and measured the backscattered radiation from the RDE inner surface using a photodetector for a round-trip path of 1.52?cm. Optimizing the sensor's optical arrangement using numerical ray tracing to minimize interference from optical emission, beam steering, and scattered laser light from window surfaces was essential to sensor performance. Scanned-wavelength-modulation spectroscopy with second-harmonic detection and first-harmonic normalization was implemented to allow for frequency-domain multiplexing of the two lasers and to suppress non-absorbing interference sources such as beam-steering and emission. Tunable diode lasers near 2551 and 2482?nm were modulated at 100 and 122?kHz, respectively, and sinusoidally scanned across the peaks of their respective water transitions at 10?kHz to provide a measurement rate of 20?kHz and detection limit of 0.5% water by mole. Experimentally derived spectroscopic parameters enabled water and temperature sensing with respective uncertainties of 7.3% and 5.3% relative to the measured values. Time-resolved and time-averaged sensor measurements of gas temperature and water vapor mole fraction allow quantitative evaluation of the combustion progress at the measurement location and thus provide a design tool for RDE optimization. Broadly, this single-ended laser sensor should find applications in other combustion systems where optical access is limited.     

兰州320kV高压平台低能核天体物理实验研究进展(英文)

在低温核天体物理环境下,如静态核稳定燃烧阶段的核反应都发生较低的能区,其伽莫夫窗口内的核反应截面非常小,这就需要加速器提供较强束流才能完成核反应截面的直接测量。最近在中国科学院近代物理的320 kV高压平台上建立了低能核天体物理实验室以及相应的研究平台。驱动该平台的是一个14.5 GHz的永磁铁型ECR离子源,它能够提供非常强的束流离子。对于质子和氦离子,离子源出口的最大流强可以达到100 eμA,在实验终端上可以获得大约30 eμA的流强。基于此强流加速器装置,我们建立了核天体物理实验测量装置,包括靶室以及带电粒子和伽玛射线探测器等设备。利用已知的核反应对探测器性能和实验方法进行了一系列测试。同时,展示了近年来取得的一些主要实验结果。最后,对该平台上开展工作的前景进行了展望,并指出基于该地面装置的低能核反应研究所积累的技术及经验对于我国锦屏深地核天体物理JUNA项目的重要意义。For the hydrostatic stable burning in stars, the Gamow window is well below the Coulomb barriers for the charged-particle-induced nuclear reaction involved. Such nuclear reaction occurs through the quantum-mechanics tunneling effect, and its cross section drops rapidly approaching the Gamow window. An accelerator which can provide intense beam current is thus required to directly measure the reactions at low energies. An experimental setup for low-energy nuclear astrophysics studies has been recently established at a 320 kV high-voltage platform of the Institute of Modern Physics (IMP), Lanzhou, China. The driver machine of this platform is a very strong ECR ion source employing all-permanent magnets, which can typically supply up to about 100 eμA proton, alpha and many other heavy ions, and ultimately about 30 eμA currents can be achieved at the experimental terminal. The experimental setup includes a target chamber, and the charged-particle and γ-ray HPGe detectors. This work describes the setup established, characteristics of detectors, methodologies, and test results of several reactions with known cross sections. Furthermore, some important results published are shown briefly. We believe that the experimental technologies developed and experiences accumulated at this above-ground platform will be extremely helpful for the Jinping Underground Nuclear Astrophysics laboratory (JUNA) project in China.