·70·2017 3-15 4.2∼18.2keV Ar2+Subquent Radiative Decay of Electron Capture from50∼200MeV/u Bare Xe54+Ions in Collisions with
Krypton and Xenon Gaous Targets∗
Yang Bian,Yu Deyang,Cai Xiaohong,Xue Yingli,Shao Caojie,Wang Wei,Liu Junliang,Zhang Mingwu,bark是什么意思
Song Zhangyong,Wu Yehong,Lu Rongchun and Ruan Fangfang
铜版纸英文In collisions between energetic highly charged ions and atoms,the ions could remove the electrons of the target atoms,or be excited into high-level states.In thefirst ca,the target electrons not only be captured into ground and excited states of the projectile ions,but also be ionized to free.Non-radiative capture(NRC)and radiative electron capture(REC)are two competing mechanisms in fast collisions[1].NRC means electron transfer from a bound state of the target to a bound states of the projectile without the emission of radiation;REC is produced with simultaneous the emission of photon for satisfying energy and momentum conrvation laws.The physical esnce is the competition between the“electron-nucleus”interaction and the“electron-vacuum”interaction.NRC is dominant in collisions of high-Z ions with heavy target atoms at moderate energies.REC entirely determine the electron capture channel for high collision velocities and light targets[1].Measuring the relative strength
怎样才能化好妆of the projectile x-ray emission associated with electron capture could determine state-lective population,angular distribution of single capture Lyα1or double capture Kα1and Kα2,would provide new detailed information on the dynamics of ion-atom collisions and atomic structure studies[1].
The experiment was carried out at the internal jet target[2]of the heavy-ion cooling storage ring HIRFL-CSRe[3] at Lanzhou.The vacuum for the CSRe was better than10−12mb.The continuous electron cooling compensated the beam loss caud by the interaction of the ions with the gaous target ud at area density of1012atom/cm2. Therefore,the experiment was single-collision,large luminance and ultra-low background.Projectile X-ray spectra were recorded in collisions of50∼20MeV/u bare Xe ions with Kr and Xe gaous targets by germanium and silicon detectors at different obrvation angles35◦,60◦,90◦,120◦,and145◦.
The X-ray spectra with Doppler correction in the emitter frame for197MeV/u Xe54+ions collision with Kr and Xe are displayed in Fig.1,and the main transitions for H-like and He-like Xe ions are marked.The analysis of X-ray spectra are bad on Gaussian-Amplitude function peakfitting procedure,paration of target-projectile mixed spec-tra and determination of the characteristic transition intensities.The experimental intensity ratios of single electron capture np→1s to2p→1s(n=3,4,5)and double electron1sn′p→1s2to n′p→1s(n′=2,3,4)were obtained.The
Fig.1(color online)X-ray energy spectra after Doppler correction,for197MeV/u Xe54+ions colliding with Kr and Xe gas atoms as obrved by the germanium at35◦(a),60◦(b),90◦(c),120◦(e)and silicon detectors at90◦(d),145◦(f) relative to the direction of the ion beam.
∗Foundation item:National Natural Science Foundation of China(11604345,U1332206)
2017·71·
anisotropy parameterβ20could be extracted by the angular distribution of the Lyα1/Lyα2intensity ratio.Also,the population of the excited states for H-and He-like xenon ions can be derived fromβ20combined with the transition rates for the cascade decay of the excited states calculated by GRASP code[4].cornwall
learningenglish
gaga是什么意思References
downton abbey[1]J.Eichler,T.Stohlker,Phys.Rep.,439(2007)1.
英语台词[2] D.Y.Yu,Y.L.Xue,C.J.Shao,et al.,Nucl.Instr.Meth.B,269(2011)692.
[3]J.W.Xia,W.L.Zhan,B.W.Wei,et al.,Nucl.Instr.Meth.A,488(2002)11.
[4]P.Jonsson,X.He,C.Fore Fischer,et al.,Comput.Phys.Commun.,177(2007)59.
3-16Momentum Computed Tomography:the Reconstruction
Framework and the Experiment Data
Zhang Yuezhao and Yu Deyang
雅思基础英语书信万能开头结尾带翻译
When energetic heavy ions interact with atoms,molecules,clusters or solid targets,various condary particles are generated.We propod a novel imaging spectrometer,the Momentum Computed Tomography(MCT)[1].In brief,a ries of two-dimensional position spectrums of the charged particles afterflying through specific static elec-tromagneticfields arefirstly obtained,which corresponds to a t of line-integral measurements of their momentum distributions;then the entire-solid-angle momentum distributions are reconstructed with the projections.Due to this working theory,no TOF is introduced in the measurement and the counting rate capability is only limited by the position nsitive detector.Thus,it combines the advantages of the modern imaging spectrometers that can image the entire-solid-angle momentum distribution,and the classical spectrometers that are suitable to inten reaction measurement if a proper detector is employed.
With the theoretical considerations in mind,we constructed a data-process framework,the Iterative Reconstruc-tion Framework of Momentum Computed Tomography(MCTIRF),which is ud in the numerical measurement and the experimental data process.The MCTIRF is coded in C++and consists of three groups of class and a graphical ur interface(GUI).Thefirst class group(CG1)defines the1d-,2d-and3d-histogram class that can fully describe the physical he position spectrum and the momentum distribution.Various momen-tum distributions,
both in histogram form and in scatter form,can be generated for further numerical studies,and standalone interface functions are coded to deliver the generated data to other program facilities.An experiment interface is also designed in CG1to read the experimental data into memory and to carry out primary data background subtraction.In the cond class group(CG2),the measurement simulation is accomplished. After a spectrometer and measurement initialization,the CG2starts to run the simulated measurement,calculating the particle tracks in the MCTfield for a given scatter momentum distribution t and giving the ur a ries of two-dimensional position spectrums.It is also convenient to compute the integral curves corresponding to different projection points,which is of much help for designing the sampling scheme.The reconstruction is accomplished in the third class group(CG3).Onefirstly construct a projection object and calculate the projection matrix in CG3. With the projection matrix and the simulated or experimentally measured he projections,which can continue to carry out the reconstruction,in the iterative methodology.An exclusive matrix template class is inte-grated into CG3,which adopts parallel calculation techniques as much as possible to fulfill the heavy computation requirement of the reconstruction procedure.
A spectrometer was built according to the simulation results of MCTIRF in our group,which was meant to test the MCT theory via measuring the momentum distribution of the sputtered positive ions
from a solid target surface at the bombarding of energetic heavy ions.The experiment is carried out at the Electron Beam Ion Source(EBIS) Ultralow-Energy Heavy Ions Laboratory of Institute of Modern Physics Chine Academy of Sciences(IMPCAS). The projectile ion is15keV Ar+,the target is highly oriented pyrolytic graphite(HOPG)with a freshly cleaved surface,the incident angle is60◦,which is defined as the angle between the ion beam and the target normal,and the vacuum is better than2×10−8mb during the measurement.The incident ion beam is collimated to a diameter of0.5mm and is tuned so that the Ar+ions will impact on the target surface right at the target center if a free MCT electricfield is assumed,and the beam deviation due to the MCT working voltage is considered in the off-line data processing.The measured position spectrums,defined to be the projections,corresponding to a ries of MCT working voltages U mct are obtained,which are shown in Fig.1.Some qualitative properties of the sputtered ions can be inferred directly from the projections.Firstly,the background events contribute significantly to all the measured
