Absolute dielectronic recombination rate coefficients of highly charged ions at the storage ring CSRm and CSRe

Dielectronic recombination(DR)is one of the dominant electron-ion recombination mechanisms for most highly charged ions(HCIs)in cosmic plasmas,and thus,it determines the charge state distribution and ionization balance therein.To reliably interpret spectra from cosmic sources and model the astrophysical plasmas,precise DR rate coefficients are required to build up an accurate understanding of the ionization balance of the sources.The main cooler storage ring(CSRm)and the experimental cooler storage ring(CSRe)at the Heavy-Ion Research Facility in Lanzhou(HIRFL)are both equipped with electron cooling devices,which provide an excellent experimental platform for electron-ion collision studies for HCIs.Here,the status of the DR experiments at the HIRFL-CSR is outlined,and the DR measurements with Na-like Kr25^(+)ions at the CSRm and CSRe are taken as examples.In addition,the plasma recombination rate coefficients for Ar12^(+),14^(+),Ca14^(+),16^(+),17^(+),Ni19^(+),and Kr25^(+)ions obtained at the HIRFL-CSR are provided.All the data presented in this paper are openly available at https://doi.org/10.57760/sciencedb.j00113.00092.

The KLL dielectronic recombination processes for highly charged krypton,iodine and barium ions

The KLL dielectronic recombination （DR） processes of ions from highly charged helium-like to oxygen-like krypton, iodine and barium ions are studied systematically in the relativistic distorted-wave approximation with configuration interaction. The KLL DR resonant energies, the corresponding resonant strengths and the theoretical spectra for each highly charged ion species are obtained. The results accord well with other available values. The behaviour of KLL resonant strengths for He-like ions with atomic number Z is analysed.

Dielectronic recombination and resonant transfer excitation processes for helium-like krypton

The relativistic configuration interaction method is employed to calculate the dielectronic recombination（DR） cross sections of helium-like krypton via the 1s2lnl ＇（n = 2,3,...,15） resonances.Then,the resonant transfer excitation（RTE） processes of Kr 34＋ colliding with H,He,H 2,and CH x（x = 0-4） targets are investigated under the impulse approximation.The needed Compton profiles of targets are obtained from the Hartree-Fock wave functions.The RTE cross sections are strongly dependent on DR resonant energies and strengths,and the electron momentum distributions of the target.For H 2 and H targets,the ratio of their RTE cross sections changes from 1.85 for the 1s2l2l ＇ to 1.88 for other resonances,which demonstrates the weak molecular effects on the Compton profiles of H 2.For CH x（x = 0-4） targets,the main contribution to the RTE cross section comes from the carbon atom since carbon carries 6 electrons;as the number of hydrogen increases in CH x,the RTE cross section almost increases by the same value,displaying the strong separate atom character for the hydrogen.However,further comparison of the individual orbital contributions of C（2p,2s,1s） and CH 4（1t 2,2a 1,1a 1） to the RTE cross sections shows that the molecular effects induce differences of about 25.1%,19.9%,and 0.2% between 2p-1t 2,2s-2a 1,and 1s-1a 1 orbitals,respectively.

Investigations of the dielectronic recombination of phosphorus-like tin at CSRm

The electron–ion recombination for phosphorus-like^（112） Sn^（35＋）has been measured at the main cooler storage ring of the Heavy Ion Research Facility in Lanzhou, China, employing an electron–ion merged-beams technique. The absolute total recombination rate coefficients for electron–ion collision energies from 0 e V–14 e V are presented. Theoretical calculations of recombination rate coefficients were performed using the Flexible Atomic Code to compare with the experimental results. The contributions of dielectronic recombination and trielectronic recombination on the experimental rate coefficients have been identified with the help of the theoretical calculation. The present results show that the trielectronic recombination has a substantial contribution to the measured electron–ion recombination spectrum of^（112）Sn^（35＋）. Although a reasonable agreement is found between the experimental and theoretical results the precise calculation of the electron–ion recombination rate coefficients for M-shell ions is still challengeable for the current theory.

The effect of configuration complex on dielectronic recombination process in highly ionized plasmas

This paper analyses the effect of configuration complex on dielectronic recombination （DR） process in highly ionized plasmas （Xe^26＋, Dy^38＋, W^46＋） by using the multiconfiguration relativistic Hartree-Fock method. Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cascades are included. Collisional transitions following electron capture are neglected. The remarkable difference between the isoelectronic trend of the rate coefficients for DR through 3d^94l4l′ and through 3d^94l5l′ is emphasized. The trend of DR through 3d^94l4l′ shows irregularities at relatively low temperature due to the progressive closing of DR channels as atomic number Z increases.

Dielectronic recombination of Co-like tantalum

Ab initio calculation of the total dielectronic recombination （DR） rate coefficient from the ground state of Co-like tantalum is performed using the relativistic distorted-wave approximation with configuration interaction. The contributions to the total DR rate coefficients are explicitly calculated from the complexes of Ni-like tantalum：3s^23p^63d3/2^33d5/2^6n′l′,3s^23p^53d^10n′l′,3s3p^63d^10n′l′,3s^23p^63d^84ln′l′,3s^23p^53d^94ln′l′ and 3s3p^63d^94ln′l′ with n′≤25, and 3s^23p^63d^85ln′l′ with n′≤9.The l′and n′ dependences of partial DR rate coefficients are investigated. The contributions from higher n^complexes are evaluated by a level-by-level extrapolation method. The total DR rate coefficients mainly come from the complex series 3s^23p^63d^84ln′l′,3s^23p^53d^94ln′l′and are fitted to an empirical formula with high accuracy. Comparison of the present results with those of other works shows that the previously published data underestimate significantly the DR rates of Co-like tantalum.

KLL dielectronic recombination process of He-like to O-like xenon ions

In this work, the KLL dielectronic recombination （DR） processes of highly charged He-like to O-like xenon ions are studied systematically by using a DR program, which is based on the multi-configuration Dirac-Fock （MCDF） method. The KLL DR resonant energies and the corresponding resonant strengths are calculated, emphasizing especially the effect of the Breit interaction on the DR strengths. The theoretical KLL DR spectra are obtained and compared with the latest experimental results obtained in the Shanghai Electron Beam Ion Trap.

Dielectronic Recombination of Br-Like Tungsten Ions

Accurate data for dielectronic recombination of tungsten ions are essential in the modeling of tungsten impurity transport and radiative power loss in International Thermonuclear Experimental Reactor （ITER）. Theoretical calculations have been made for dielectronic recombi- nation （DR） rate coefficients of Br-like tungsten ions using a flexible relativistic atomic code （FAC） from i eV to 50 keV. Level-by-level calculations are carried out for evaluating the contributions to DR through all the relevant Kr-like tungsten ions autoionizing inner-shell excited configuration complexes： （3s23p63d10）-14s24p5nlntl＇ （n = 4-5, n＇ = 4-100,l＇ = 0-8）, （4s24pS）-lnln＇l＇ （n = 4-6, n＇ = 4-100, l＇ = 0-12）. Comparison of the rate coefficients for 3s, 3p, 3d, 4s and 4p subshell excitations shows that the 4p subshell excitation dominates over the whole temperature region, 4s subshell excitation at low temperature and 3p, 3d subshell excitations at high temperature can not be neglected. In order to facilitate simple applications, the total DR rate coefficient, △n = 0,1 and 2 core excitations DR rate coefficients are fitted to an empirical formula.

K-shell excitation dielectronic recombination resonance strengths of highly charged Helike to O-like Xe ions

Dielectronic recombination is an important process in high temperature plasmas. In the present work, the KLn （n=L, M, N and O） DR resonance strengths of He-like to O-like xenon ions are measured at the Shanghai electron beam ion trap using a fast electron beam energy scanning method. The experiment uncertainty reaches about 6% with significant improvement of statistics. A relativistic configuration interaction calculation is also made. Theoretical results agree with the experiment results within 15% in most cases.

Effect of dielectronic recombination on charge-state distribution in laser-produced plasma based on steady-state collisional-radiative models

Armed with four different steady-state collisional-radiative(CR) models,we investigated the effect of dielectronic recombination(DR) on the charge-state distribution in laser-produced silicon plasma. To assess this effect,we performed a series of temporally resolved spectra of highly charged Si ions in the extreme ultraviolet region.Ab initio calculations of the DR rate coefficients were done for Si^(6+)–Si^(4+) ions. We also analyzed the evolution of the collisional ionization, radiative recombination, three-body recombination, photo-ionization, and DR rate coefficients as a function of electron temperature. The electron temperature and electron density for different delay times were obtained by comparing the normalized experimental and simulated spectra. The ion fraction and average charge state from the four different CR models were also obtained. The results indicate that the DR process has a greater influence in the stage of plasma evolution that cannot be neglected in plasma diagnoses.

4-5 Dielectronic Recombination of Li-like Argon Ions at the CSRm

The main cooler storage ring (CSRm) equipped with an electron-cooler creates an ideal platform for dielectronicrecombination (DR) experiments. In order to fully understand our DR experimental setup and especially the electronenergy detuning system, we have performed a DR calibration experiment using the Li-like argon ions at theCSRm. The Ar15+ has a simple electronic structure so the DR spectrum can be calculated with an ultra-highprecision and compared with the existing experimental data. The experiment was carried out at the relative energyfrom 0 to 32 eV that includes all DR resonances associated with 2s1=2 ! 2p1=2 and most of the 2s1=2 ! 2p3=2excitations.

4-1 Dielectronic Recombination of 36Ar15+ and 112Sn34+ at the CSRm

The total recombination rate coefficients of lithium-like 36Ar15+ ions have been measured by employing the electron-ion merged-beams technique at the heavy ion storage ring CSRm at IMP[1]. Fig. 1 (a) shows the DR spectrum for electron energy from 0 to 35 eV in the center-of-mass (c.m.) frame involving all the DR resonances associated with 2s1=2!2p1=2 and 2s1=2!2p3=2 excitations.

The influence from high-n dielectronic satellites to Kα resonance line in helium-like aluminium

Based on the multi-configuration Dirac-Fock method, this paper has made theoretical calculations for the dielectronic recombination cross-sections and the high-n dielectronic satellites to Kα resonance line in helium-like aluminium ions. It is found that high-n dielectronic satellites are seriously mixed with resonance line, which leads to a significant increase in both the apparent width and the intensity of Kα resonance line. They also induce a positional shift of Kα resonance line.

为像氦的克的 Dielectronic 再结合和反响的转移刺激过程

The relativistic configuration interaction method is employed to calculate the dielectronic recombination(DR) cross sections of helium-like krypton via the 1s2lnl ’(n = 2,3,...,15) resonances.Then,the resonant transfer excitation(RTE) processes of Kr 34+ colliding with H,He,H 2,and CH x(x = 0-4) targets are investigated under the impulse approximation.The needed Compton profiles of targets are obtained from the Hartree-Fock wave functions.The RTE cross sections are strongly dependent on DR resonant energies and strengths,and the electron momentum distributions of the target.For H 2 and H targets,the ratio of their RTE cross sections changes from 1.85 for the 1s2l2l ’ to 1.88 for other resonances,which demonstrates the weak molecular effects on the Compton profiles of H 2.For CH x(x = 0-4) targets,the main contribution to the RTE cross section comes from the carbon atom since carbon carries 6 electrons;as the number of hydrogen increases in CH x,the RTE cross section almost increases by the same value,displaying the strong separate atom character for the hydrogen.However,further comparison of the individual orbital contributions of C(2p,2s,1s) and CH 4(1t 2,2a 1,1a 1) to the RTE cross sections shows that the molecular effects induce differences of about 25.1%,19.9%,and 0.2% between 2p-1t 2,2s-2a 1,and 1s-1a 1 orbitals,respectively.

重离子储存环CSRe上类钠Kr^(25+)离子的双电子复合精密谱学实验研究

高电荷态离子的双电子复合精密谱学实验研究,不仅对天体等离子体和聚变等离子体的研究具有重要意义,而且可以作为一种新的精密谱学工具,用来检验强场量子电动力学效应、测量同位素移动及提取原子核电荷半径等.在兰州重离子储存环CSRe上,安装了专门用于电子-离子复合精密谱学实验的电子束能量调制系统,质心系下电子-离子碰撞能量的调制范围达到0—1 keV.在CSRe电子冷却器下游安装了自主研制的塑料闪烁体探测器和多丝正比探测器,用于探测复合离子.在此基础上,使用Kr^(25+)离子在CSRe上进行了首次双电子复合测试实验,实验测量了质心系能量0—70 eV的双电子复合速率系数.为了更好地理解实验测量结果,利用FAC(flexible atomic code)程序计算了Kr^(25+)离子的双电子复合速率系数,并与实验做了细致对比,整体符合很好,而且发现3s→41(△n=1)的共振跃迁对实验谱线有很大的贡献.实验结果表明,CSRe双电子复合实验平台具有非常好的稳定性和可重复性,能够为下一步开展更高电荷态离子的双电子复合精密谱学实验、检验强场量子电动力学效应以及原子核性质精密测量等前沿实验提供支持.

Dielectronic recombination rate coefficients of Cu-like Ta ion

The knowledge of accurate ionization and recombination rates of heavy ions is crucial for the study of X-ray lasers and inertia confine fusion ( ICF).The dielectronic recombination rates of Cu-like Ta44+ (1s22s22p63s23p63d104s1) ion through the (3d1041n’1’n’=4,5) configurations are given.The remarkable difference between the isoelectronic trends of the rate coefficients for dielectronic recombination through 3d104141’ and 3d104151’ is emphasized.

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

The 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 was discussed in this paper. The overall results show that the new detuning system works properly, and could fulfill the requirements of future DR experiment.

A Numerical Study for Dielectronic Recombination Processes in He-Like Argon

Ab initio calculations of dielectronic recombination(DR)processes from the ground state 1s 2 of He-like argon ion through doubly excited states 1s2snl,1s2pnl(n=2 to 9)of Li-like argon ions are performed using the multi-configuration HatreeFock method with relativistic correction.The theoretical method and its corresponding computation will be outlined.For higher doubly excited states with n>9,the scaling law is used to extrapolate the Auger and radiative transition rates.The total and stateto-state cross sections with corresponding rate coefficients in the temperature from 102 eV to 106 eV are presented,as well as the DR strengths for all the separate resonances.Moreover,peculiarities of the DR from doubly excited 1s2s3l′configurations are analyzed and the contributions of two-electron-one-photo(TEOP)radiative transitions to the DR cross sections are also investigated,such as 1s2s^(2)→1s^(2)2p,due to the strong configuration interactions.Our theoretical results appear to be in excellent agreement with the previous and recent experimental measurements.

High-precision high-voltage detuning system for HIAF-SRing electron target

The development of a detuning system for the precision control of electron energy is a major challenge when electron targets are used in ion-storage rings.Thus,a high-precision,high-voltage,detuning system was developed for the electron target of a high-intensity heavy-ion accelerator facility-spectrometer ring(HIAF-SRing)to produce accurate electron-ion relative energies during experiments.The system consists of auxiliary,and high-voltage detuning power supplies.The front stage of the auxiliary power supply adopts an LCC resonant converter operating in the soft-switching state and an LC filter for a sinusoidal waveform output in the post-stage.The detuning power supply is a high-voltage pulse amplifier(HVPA)connected with a high-voltage DC(HVDC)module in series.In this paper,the design and development of the detuning system are described in detail,and the test bench is presented.The test results demonstrated that the detuning system conforms to the technical specifications of the dielectronic recombination(DR)experiment.Finally,a Fe15+DR spectrum was measured using the detuning system.The experimental data demonstrated a good experimental resolution and verified the reliability and feasibility of the design.