Ma Xinwen

A Semi-Quantitative Analysis of Essential Micronutrient in Folium Lycii Using Laser-Induced Breakdown Spectroscopy Technique

In this paper, the capabilities of laser-induced break down spectroscopy (LIBS) for rapid analysis to multi-component plant are illustrated using a 1064 nm laser focused onto the surface of folium lycii. Based on homogeneous plasma assumption, nine of essential micronutrients in folium lycii are identified. Using Saha equation and Boltzmann plot method electron density and plasma temperature are obtained, and the irrelative concentration (Ca, Mg, Al, Si, Ti, Na, K, Li, and Sr) are obtained employing a semi-quantitative method.

Influence of Laser Wavelength on Laser-induced Breakdown Spectroscopy Applied to Semi-Quantitative Analysis of Trace-Elements in a Plant Sample

Laser-induced breakdown spectroscopy (LIBS) as a powerful analytical technique is applied to analyze trace-elements in fresh plant samples. We investigate the LIBS spectra of fresh holly leaves and observe more than 430 lines emitted from 25 elements and molecules in the region 230?438 nm. The influence of laser wavelength on LIBS applied to semi-quantitative analysis of trace-element contents in plant samples is studied. The results show that the UV laser has lower relative standard deviations and better repeatability for semi-quantitative analysis of trace-element contents in plant samples. This work may be helpful for improving the quantitative analysis power of LIBS applied to plant samples.

Influence of Ambient Gas on Laser-Induced Breakdown Spectroscopy of Uranium Metal

Laser-induced breakdown spectroscopy (LIBS) is regarded as a suitable method for the remote analysis of materials in any phase, even in an environment with high radiation levels. In the present work we used the third harmonic pulse of a Nd:YAG laser for ablation of uranium metal and measured the plasma emission with a fiber-optic spectrometer. The LIBS spectra of uranium metal and their features in different ambient gases (i.e., argon, neon, oxygen, and nitrogen) at atmospheric pressure were studied. Strong continuum spectrum and several hundreds of emission lines from UI and UII were observed. It is found that the continuum spectrum observed in uranium not only comes from bremsstrahlung emission but is also due to the complex spectrum of uranium. The influence of ambient gas and the gas flow rate for ablation of uranium metal was investigated. The experimental results indicate that the intensity of the uranium lines was enhanced in argon and nitrogen. However, the intensity of uranium lines was decreased in oxygen due to the generation of UO and other oxides. The results also showed that the highest intensity of uranium lines were obtained in argon gas with a gas flow rate above 2.5 L/min. The enhanced mechanism in ambient gas and the influence of the gas flow rate were analyzed in this work.

Simulation and measurement of the resonant Schottky pickup

A resonant Schottky pickup with high sensitivity, built by GSI, will be used for nuclear mass and lifetime measurement at CSRe. The basic concepts of Schottky noise signals, a brief introduction of the geometry of the detector, the transient response of the detector, and MAFIA simulated and perturbation measured results of characteristics are presented in this paper. The resonant frequency of the pickup is about 243 MHz and can be slightly changed at a range of 3 MHz. The unloaded quality factor is about 1072 and the shunt impedance is 76 kΩ. The measured results of the characteristics are in agreement with the MAFIA simulations.

Longitudinal Schottky spectra of a bunched Ne10+ ion beam at the CSRe

The longitudinal Schottky spectra of a radio-frequency (RF) bunched and electron cooled 22Ne10+ ion beam at 70 MeV/u have been studied by a newly installed resonant Schottky pick-up at the experimental cooler storage ring (CSRe), at IMP. For an RF-bunched ion beam, a longitudinal momentum spread of Δp/p = 1.6 × 10−5 has been reached with less than 107 stored ions. The reduction of momentum spread compared with a coasting ion beam was observed from Schottky noise signal of the bunched ion beam. In order to prepare the future laser cooling experiment at the CSRe, the RF-bunching power was modulated at 25th,50th and 75th harmonic of the revolution frequency, effective bunching amplitudes were extracted from the Schottky spectrum analysis. Applications of Schottky noise for measuring beam lifetime with ultra-low intensity of ion beams are presented, and it is relevant to upcoming experiments on laser cooling of relativistic heavy ion beams and nuclear physics at the CSRe.

Research on the detuning system of a cooling electron beam for the dielectronic recombination experiment at CSRm

A storage ring equipped with an electron cooler is an ideal platform for dielectronic recombination (DR) experiments. In order to fulfill the requirement of DR measurements at the main Cooler Storage Ring, a detuning system for the precision control of the relative energy between the ion beam and the electron beam has been installed on the electron cooler device. The test run using 7.0 MeV/u C6+ beam was performed with recording the Schottky spectra and the ion beam currents. The influence of pulse heights and widths of the detuning voltage on the ion beam was analyzed. For the small pulse height, the experimental results from the Schottky spectra were in good agreement with the theoretical results. The frequency shift in the Schottky spectra was significantly reduced for the short pulse width. For the large pulse height, an oscillation phenomenon was observed and some effective ways to reduce the oscillation were pointed out. The detailed description of the phenomenon and the theoretical model based on the plasma oscillation is discussed in this paper. The overall results show that the new detuning system works properly, and could fulfill the requirements of future DR experiments.

State-Selective Electron Capture for keV He2+ Ions on Helium Collisions Studied by Recoil Momentum Spectroscopy

State-selective single electron capture cross sections are measured by recoil ion momentum spectroscopy technique for He2+ on He at 30 keV incident energy. The cross sections for capture into ground and excited states are obtained and compared to classical model calculations as well as to the quantum mechanical calculations. The experimental results are in good agreement with quantum mechanical results.

Low-Energy Rate Enhancement in Recombination Processes of Electrons into Bare Uranium Ions

Based on the Dirac–Fork–Slater method combined with the multichannel quantum defect theory, the recombination processes of electrons into bare uranium ions (U92+) are investigated in the relative energy range close to zero, and the x-ray spectrum emitted in the direct radiative recombination and cascades processes are simulated. Compared with the recent measurement, it is found that the rate enhancement comes from the additional populations on high Rydberg states. These additional populations may be produced by other recombination mechanisms, such as the external electric-magnetic effects and the many-body correlation effects, which still remains an open problem.

Average Energy Loss Measured in Single and Double Electron Capture Collisions of He2+ on Ar at Low Velocities

Employing the recoil ion momentum spectroscopy we investigate the collision between He2+ and argon atoms. By measuring the recoil longitudinal momentum the energy losses of projectile are deduced for capture reaction channels. It is found that in most cases for single- and double-electron capture, the inner electron in the target atom is removed, the recoil ion is in singly or multiply excited states (hollow ion is formed), which indicates that electron correlation plays an important role in the process. The captured electrons prefer the ground states of the projectile. It is experimentally demonstrated that the average energy losses are directly related to charge transfer and electronic configuration

Ionization Spectroscopic Measurement of nP Rydberg Levels of 87Rb Cold Atoms

We created an ultracold plasma via the spontaneous ionization of cold dense Rydberg atoms of 87Rb in a magneto-optical trap (MOT), and measured the nS1/2 (n = 50–80), nP1/2 (n = 16–23), nP3/2 (n = 16–98), and nD5/2 (n = 49–96) Rydberg levels by detecting the electrons in the ultracold plasma. By fitting the energy levels of Rydberg states, the first ionization potential of 33690.950(11) cm−1 and the quantum defects of S, P, and D orbitals were obtained. The absolute transition energies of nS1/2 (n = 66–80), nP1/2 (n = 16–23), nP3/2 (n = 16–98), and nD5/2 (n = 58–96) states of 87Rb, as well as the quantum defects for p1/2 and p3/2 series, are given for the first time.