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The detuning-voltage scan modes of electron voltage detuning system. (a) Unipolar scan mode: only positive or negative detuning voltage was employed in the experiment. (b) Bipolar scan mode: both positive and negative voltages were employed in the experiment. The detuning timing schemes at every single detuning voltage are shown in the panel of each figures.
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The main cooler storage ring (CSRm) of the HIRFL facility in Lanzhou, China is equipped with an electron-cooler and denotes an ideal platform for dielectronic recombination (DR) experiments. In order to fully understand our DR experimental setup and especially the electron energy detuning system, we have performed a DR calibration experiment using...
Citations
... In recent decades, several storage rings, including the TSR at MPIK in Heidelberg, [16] ESR at GSI in Darmstadt, [17] and CRYRING at MSL in Stockholm [18] have been dedicated to DR measurements. Rate coefficients for various ranges of HCIs have been determined by employing the merged-beam technique (see Refs. [1,16,19] [20][21][22][23][24][25][26][27][28][29] have been accomplished at the CSRm in the past few years, and the first calibration experiment with Na-like Kr 25+ ions has been successfully performed at the CSRe. [30] In this paper, the recent progress on DR experiments at the HIRFL-CSRm and CSRe is overviewed. ...
... Since the first calibration DR experiment with Lilike Ar 15+ ions at the CSRm in 2015, [20] DR rate coefficients of a series of HCIs, including 40 Ar 12+,13+,14+ , [21][22][23] 40 Ca 14+,16+,17+ , [24][25][26] 58 Ni 19+ , [28] 112 Sn 35+ , [ The schematic view of the HIRFL-CSR facility combined with the DR experimental setup at the CSRm and the CSRe. The moveable particle detectors are installed downstream of the electron cooler. ...
... Before data recording, the stored ion beam was cooled for about several seconds by merging with the velocity matched (β ion = β e ) electron beam over an effective interaction length of L = 4.0 m, achieving a longitudinal momentum spread of about ∆p/p ≈ 2.0 × 10 −4 . The electron beam emitted from the cathode of the cooler was adiabatically expanded from the magnetic field of 125 mT at the gun section to 39mT at the guiding section, with which the perpendicular electron beam temperature was reduced to k B T ⊥ ≈ 30 meV. [20] The longitudinal electron beam temper-073401-3 ature of k B T ≈ 0.8 meV was achieved by accelerating the beam energy to the cooling point. [20] The electron beam at the straight section was confined to a diameter of ∼ 52 mm with a typical spatial density of 9.62 × 10 6 cm −3 . ...
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 storage rings CSRm and 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 Kr ²⁵⁺ ions at the CSRm and CSRe are taken as examples. In addition, the plasma recombination rate coefficients for Ar 12+, 14+ , Ca 14+, 16+, 17+ , Ni ¹⁹⁺ , and Kr ²⁵⁺ ions obtained at the HIRFL-CSR are provided. All the data presented in this paper are openly available at https://www.scidb.cn/anonymous/UUpuSWZx.
... Therefore, the MWPC was also used to optimize the status of the ion beam in the storage ring. In the whole measurement, the counts of the recombined ions, the ion current, the electron current, and the time sequences of the detuning voltages were recorded to derive the recombination rate coefficients [52]. ...
... γ i would not be substantially changed during the measurement because of the sufficient electron cooling. The space charge effect of the electron beam was carefully corrected [52,53] for equation (3). Note that the recorded counts consist of the signals of the DR, RR, and collision with the residual gas. ...
Dielectronic recombination (DR) rate coefficients for carbon-like Kr30+ have been measured over the collision energy of 0-60 eV using the heavy-ion storage ring CSRe at the Institute of Modern Physics in Lanzhou, China. The present DR spectrum covers the resonances associated with the 2s^22p^2[3P0] → 2s^22p^2[3P1,2], 2s2p^3 and 2p^4 (∆N = 0) core excitations. The corresponding DR resonance energies and strengths have been calculated by using the flexible atomic code (FAC) to understand the measured results. An overall agreement has been obtained between the experiment and theory, except for the data at the collision energies below 7 eV and in 35-38 eV, where the electronic correlation effect is strong. In particular, the resonances from the trielectronic recombination due to 2s^22p^2 + e- → 2p^4[1D2]6l have been identified with the help of the FAC calculation. Temperature-dependent plasma recombination rate coefficients were derived from the measured DR rate coefficients for the temperature range 10^3 − 10^7 K and compared with our FAC calculations as well as the previous AUTOSTRUCTURE calculations by Zatsarinny et al: (2004 Astronomy & Astrophysics 417 1173-1181. The FAC and AUTOSTRUCTURE calculations are in good agreement with the presently derived plasma rate coefficients. The present work provides the benchmark data for astrophysical and laboratory plasma modelling.
... Laboratory (MSL) in Stockholm [11] (in 2013 relocated to GSI in Darmstadt [7]), and the Experimental Storage Ring (ESR) at GSI [12,13]. More recently, the experimental approach was also implemented at the ion-storage rings HIRFL-CSRm and CSRe at the Institute of Modern Physics (IMP), Chinese Academy of Sciences, and already delivered results on electron-ion recombination of a number of ion species [14][15][16]. Here it is used for a precise determination of the 2s 2 2p 5 2 P 3/2 → 2s 2p 6 2 S 1/2 transition energy in F-like Ni 19+ ions. ...
... The experiment was performed by employing the electronion merged-beams technique at the heavy-ion storage ring CSRm at the Institute of Modern Physics in Lanzhou, China. Several DR measurements related to astrophysical and plasma applications were carried out successfully at the CSRm [14][15][16] since the calibration experiment with lithiumlike Ar 15+ in 2015 [14]. Recombination rate-coefficients of fluorine-like nickel were already published previously in Ref. [16], which also contains a detailed description of the experimental setup and procedures. ...
... The experiment was performed by employing the electronion merged-beams technique at the heavy-ion storage ring CSRm at the Institute of Modern Physics in Lanzhou, China. Several DR measurements related to astrophysical and plasma applications were carried out successfully at the CSRm [14][15][16] since the calibration experiment with lithiumlike Ar 15+ in 2015 [14]. Recombination rate-coefficients of fluorine-like nickel were already published previously in Ref. [16], which also contains a detailed description of the experimental setup and procedures. ...
High-precision spectroscopy of the low-lying dielectronic resonances in fluorine-like Ni19+ ions was studied by employing the electron-ion merged-beams method at the heavy-ion storage ring CSRm. The measured dielectronic-recombination (DR) resonances are identified by comparison with relativistic calculations utilizing the flexible atomic code. The lowest-energy resonance at about 86 meV is due to DR via the (2s2p6[2S1/2]6s)J=1 intermediate state. The position of this resonance could be determined within an experimental uncertainty of as low as ±4meV. The binding energy of the 6s Rydberg electron in the resonance state was calculated using two different approaches, the multiconfigurational Dirac-Hartree-Fock (MCDHF) method and the stabilization method (SM). The sum of the experimental (2s2p6[2S1/2]6s)J=1 resonance energy and the theoretical 6s binding energies from the MCDHF and SM calculations yields the following values for the 2s22p52P3/2→2s2p62S1/2 transition energy: 149.056(4)exp(20)theo and 149.032(4)exp(6)theo, respectively. The theoretical calculations reveal that second-order QED and third-order correlation effects contribute together about 0.1 eV to the total transition energy. The present precision DR spectroscopic measurement builds a bridge which enables comparisons between different theories.
... The DR experimental method at the CSRm has been already described in detail elsewhere. [38][39][40] In order to perform DR experiments with high-Z HCIs, the electron cooler (EC-300) at the CSRe has been upgraded with an embedded electron energy fast detuning system for the merged-beams electron-ion collision experiments. A plastic scintillation detector (PSD) and a multiwire proportional chamber (MWPC) detector have been developed and installed downstream of the electron cooler to detect the recombined and ionized ions in the electron-ion collision experiments at the CSRe. ...
The research progresses on the investigations of atomic structure and collision dynamics with highly charged ions based on the heavy ion storage rings and electron ion beam traps in recent 20 years are reviewed. The structure part covers test of quantum electrodynamics and electron correlation in strong Coulomb field studied through dielectronic recombination spectroscopy and VUV/x-ray spectroscopy. The collision dynamics part includes charge exchange dynamics in ion-atom collisions mainly in Bohr velocity region, ion induced fragmentation mechanisms of molecules, hydrogen-bound and van de Waals bound clusters, interference and phase information observed in ion-atom/molecule collisions. With this achievements, two aspects of theoretical studies related to low energy and relativistic energy collisions are presented. The applications of data relevant to key atomic processes like dielectronic recombination and charge exchanges involving highly charged ions are discussed. At end of this review, some future prospects of research related to highly charged ions are proposed.
... Abundant rate coefficients involving HCIs relevant to astrophysics have been measured at TSR and CRYRING while ESR has been dedicated to the precision studies with heavy HCIs. More recently, HIRFL-CSRm and CSRe at the Institute of Modern Physics (IMP), Chinese Academy of Sciences started contributing to the community [19][20][21][22][23][24][25]. With the low-temperature electron target and the merged-beam technique, the experimental resolution could be improved prominently, in particular for the low-lying resonances above the threshold [9,14]. ...
... The experiment was performed by employing the merged-beam technique at the heavy-ion storage ring CSRm at the Institute of Modern Physics in Lanzhou, China. Several DR measurements related to astrophysical and plasma applications have been carried out successfully at the CSRm [20][21][22][23][24][42][43][44][45][46] since the calibration experiment with lithium-like Ar 15+ in 2015 [19]. Recombination rate coefficients of fluorine-like nickel have also been published previously [22]. ...
High precision spectroscopy of the low-lying dielectronic resonances in fluorine-like nickel ions were determined by employing the merged electron-ion beam at the heavy-ion storage ring CSRm. The measured dielectronic resonances are identified by comparing with the most recent relativistic calculation utilizing the FAC code. The first resonance at about 86 meV due to the dielectronic recombination via (2s2p6[2S1/2]6s)J=1 intermediate state was recognized. The experimental determination of the resonance position at 86 meV reaches an uncertainty of 4 meV, which allows precise determination of the 2s22p5[2P3/2] - 2s2p6[2S1/2] transition energy. The Rydberg binding energy of the 6s electron in the (2s2p6[2S1/2]6s)J=1 state is calculated by the multi-configurational Dirac-HartreeFock and stabilization methods. The determined transition energies are 149.056(4)exp(10)theo and 149.032(4)exp(6)theo, respectively. Moreover, the transition energy has also been calculated by fully relativistic and ab initio approaches. Individual theoretical contributions are evaluated by employing the core-Hartree and Kohn-Sham screening potentials, respectively. High-order QED and correlation effects contribute prominently to the total transition energy. The present DR precision spectroscopy study at the CSRm paves the way for future precision measurements of atomic energy levels with heavier highly charged ions.
... Similarly, the DR experiments of HCIs using electron-ion merged beams method have been also performed at other heavy ion storage rings i.e., ESR at GSI in Darmstadt [34] and CRYRING at MSL in Stockholm, Sweden (currently installed at the ESR, GSI) [35]. To date, many DR experiments have been carried out for astrophysically relevant Li-like ions by utilizing the different heavy ion storage rings e.g., C 3+ [5,36], N 4+ [37,38], O 5+ [39,40], Ne 7+ [37,41,42], Na 8+ [43], Si 11+ [44,45], Ar 15+ [46,47], Ni 25+ [48]. The DR experiments on other astrophysically relevant ions with different charge states at the heavy ion storage rings can be found in the review papers [11,49,50] and references therein. ...
The rate coefficients for dielectronic recombination (DR) of lithium-like 40Ca17+ ions with ∆n = 0 core excitations are derived from electron-ion recombination spectra measured with merged-beams method at the heavy-ion storage ring CSRm. The experimental DR spectrum, in the electron-ion collision energy range of 0 to 42 eV in the center-of-mass frame, comprises of all DR resonance peaks belong to the 2s 2S1/2 → 2p 2P1/2, 3/2 core excitations. The resonant energies and strengths for the resolved resonances in 2pjnl series are determined by fitting of the measured DR peaks. The further interpretation of the measured DR rate coefficients has been performed by calculating the DR rate coefficients with relativistic configuration-interaction method implemented in Flexible Atomic Code (FAC) and compared with the experimental results. The experimental results and FAC calculations are found to be in a good agreement within the experimental uncertainties. Moreover, temperature dependent plasma rate coefficients were constructed from 4×103 to 1×107 K energy region by convoluting experimental and theoretical DR rate coefficients with the Maxwellian energy distribution function and then compared with previously available data. The plasma DR rate coefficient is found to be significantly underestimated by the early theoretical data calculated by Jacobs et al., and Mazotta et al in the low temperature. In contrast, a very good agreement has been found between the theoretical DR data of Gu and Colgan et al and the presently measured results at the low temperature region. Therefore, the results in this work composed of a bench-mark data set for plasma modeling at the photoionized temperature range. We have also provided a fit to our measured and theoretical plasma rate coefficients for low temperature plasma modeling.
... A storage ring equipped with an electron cooler provides a uniquely effective technique to determine accurate and absolute DR rate coefficients, especially at the low energy electron-ion collisions. A series of DR experiments with highly charged ions have been carried out at the storage rings, i.e., TSR at MPIK in Heidelberg [17], ESR at GSI in Darmstadt [18], CRYRING at MSL in Stockholm [19], and CSRm at the Institute of Modern Physics (IMP) in Lanzhou [20]. More details about DR experiments at the storage rings can be found in recent reviews [4,17,21], and the references therein. ...
... Generally, a measurement cycle covers a series of different detuning voltages with an equidistant minimum step of 1 volt in the laboratory system. The detuning timing sequence is set for energy detuning for 10 ms and for electron cooling for 190 ms for each single detuning voltage [20]. This provided nonzero relative energies between electron and ion beams in the center-of-mass frame. ...
... Energy dependent DR rate coefficients of Kr 25+ were investigated in the energy range up to 70 eV, constituting all n = 0 DR resonances up to the 3s 1/2 → 3p 1/2 and 3s 1/2 → 3p 3/2 series limit. The systematic corrections for space charge effects were processed in the usual manner [20,49]. The predominant uncertainty of the rate coefficients measured in this work is estimated to be about 30% at a 1σ confidence level, including a 1% uncertainty for statistics, a 10% uncertainty for the electron and ion beam current and the electron-ion interaction length, an uncertainty of 15% due to the background subtraction and an uncertainty of 25% for the electron density in the cooler section and the position of the ion beam in this profile. ...
The absolute rate coefficients for dielectronic recombination (DR) of sodiumlike krypton ions were measured by employing the electron-ion merged-beam technique at the heavy-ion storage ring CSRm at the Institute of Modern Physics in Lanzhou, China. The measured DR spectrum covers the electron-ion collision energy range of 0–70 eV, encompassing all of the DR resonances due to 3s→3p and part of the DR resonances from 3s→3d(Δn=0) and 3s→4l(Δn=1) core excitations. A series of peaks associated with DR processes have been identified by the Rydberg formula. The experimental DR results are compared with the theoretical calculations using a relativistic configuration interaction flexible atomic code and the distorted-wave collision package autostructure. A very good agreement has been achieved between the experimental results and the theoretical calculations by considering the strong mixing among the low-energy resonances in both calculations. The experimentally derived DR spectrum is then convolved with a Maxwellian-Boltzmann distribution to obtain the temperature dependent plasma recombination rate coefficients and compared with previously available results from the literature. The present experimental result yields a precise plasma rate coefficients at the low temperature range up to ∼1×106K and the calculated data by Altun et al. [Z. Altun, A. Yumak, N. R. Badnell, S. D. Loch, and M. S. Pindzola, Astron. Astrophys. 447, 1165 (2006)] provide reliable plasma rate coefficients at high temperature range above 2×106K.
... The experiment was performed by the ion-electron beams merging technique on the main cooler storage ring (CSRm) at the Institute of Modern Physics (IMP) in Lanzhou, China. The procedures for DR measurements at the CSRm have already been described in detail elsewhere (Huang et al. 2015;Khan et al. 2018;Wang et al. 2018). Several electron-ion recombination experiments related to astrophysical and fusion plasmas have been investigated very recently Wang et al. 2019). ...
... meV and k B T P =0.33(1) meV, respectively, which are consistent with the temperatures obtained in the DR experiment of B-like Ar 13+ at the CSRm ), but differ from the machine design parameters (Huang et al. 2015). Since the electron density distribution along the beam radius can be varied by adding a special control electrode to the conventional gun at the electron cooler of the CSRm (Bocharov et al. 2004), the investigation of the electron temperature will be carried out systematically by more DR experiments as well as by simulations in further studies. ...
... The center-of-mass collision energies between electrons and ions were calculated using the added detuning voltage at the electron cooler. The space-charge effect and drag force were taken into account to deduce accurate collision energies (Huang et al. 2015). For the DR experiment of Ca 14+ , the high voltage added on the cathode is 3.456 kV at the cooling point. ...
Dielectronic recombination (DR) rate coefficients for carbon-like 40Ca14+ forming nitrogen-like 40Ca13+ have been measured using the electron–ion merged-beam technique at the heavy-ion storage ring CSRm at the Institute of Modern Physics in Lanzhou, China. The measured DR rate coefficients in the energy range from 0 to 92 eV cover most of the DR resonances associated with 2s 22p 2 → 2s 22p 2 and 2s 22p 2 → 2s2p 3 core transitions (ΔN = 0). Theoretical calculations of the DR cross sections were carried out by using two different state-of-the-art atomic theoretical techniques, multiconfiguration Breit–Pauli (MCBP) code AUTOSTRUCTURE and relativistic configuration interaction code FAC, to compare with the experimental rate coefficients. The theoretical calculations agree with the experimental results at collision energy higher than 10 eV. However, significant discrepancies of resonance energies and strengths can be found at collision energy below 8 eV. Temperature-dependent plasma recombination rate coefficients were derived from the measured DR rate coefficients in the energy range from 0.1 to 1000 eV and compared with the recommended atomic data from the literature. The theoretical data of Gu et al. and Zatsarinny et al. are 30% lower than the experimental results at the temperatures of photoionized plasmas, but have a very good agreement at the temperatures of collisionally ionized plasmas. Other previously published theoretical data of Jacobs et al. and Mazzotta et al. by using Burgess formula and LS-coupling calculations significantly underestimate the plasma rate coefficients in the low temperature range. The present results comprise a set of benchmark data suitable for astrophysical modeling.
... The most reliable experimental technique for measuring DR spectrum at low energies is the electron-ion merged beams technique at heavy ion storage rings, which have been developed for more than two decades [13][14][15]. A rather new facility comprising main cooler storage ring (CSRm) equipped with electron coolers has been developed at Lanzhou, China, and it provides an ideal research platform for electron-ion recombination studies of highly charged ions [16]. The recent reviews about DR experiments at storage rings have been given by [13][14][15]. ...
... For the electron-ion recombination experiments on argon ions by employing storage rings, only few experimental results are available, i.e. Ar 7+ [22,23], Ar 13+ [24][25][26], Ar 14+ [27], Ar 15+ [16,28], Ar 16+ [29]. In addition to the measurements of electron-ion recombination of argon ions at storage rings, the argon ions of Ar 16+ , Ar 17+ , and Ar 18+ have been investigated by using electron beam ion source [30,31] and electron beam ion trap [29,32], respectively. ...
... The recombination measurement was performed at the electron cooler of main cooler storage ring (CSRm) at the Institute of Modern Physics in Lanzhou, China. The details of the experimental technique and setup have been given elsewhere [16,33,34]. Here, most relevant aspects of electron-ion recombination experiment of C-like 40 Ar 12+ are described. ...
Electron-ion recombination of carbon-like Ar¹²⁺ forming Ar¹¹⁺ has been investigated for the first time by using the cooler storage ring CSRm at the Institute of Modern Physics in Lanzhou, China. The absolute recombination rate coefficients are derived from the measurement in the electron-ion collision energy range of 0–50 eV, covering dielectronic recombination (DR) resonances associated with 2s²2p² and 2s2p³ (Δn = 0) core excitations. Theoretical results are obtained by employing FAC code and compared with the experimental recombination spectrum. An overall agreement is found in resonance energy positions between merged-beam and calculated spectra. Temperature dependent rate coefficients are derived from the measured DR spectrum by convoluting it with a Maxwell–Boltzmann energy distribution and compared with the calculations from the literature. In the presented temperature range 10³–10⁷ K, the experimentally derived rate coefficients agree with the theoretical results of Gu (2003 Astrophys. J. 590 1131) within the experimental uncertainties. The calculation by Zatsarinny et al (2004 Astron. Astrophys. 417 1173) underestimates the rate coefficients in the temperature range 10³–5 × 10⁴ K. The combination of the experimental results and theoretical calculation provides a benckmark for Ar¹²⁺ recombination data used in astrophysical modeling.
... The most reliable experimental technique for measuring DR spectrum at low energies is the electron-ion merged beams technique at heavy ion storage rings, which have been developed for more than two decades [13][14][15]. A rather new facility comprising main cooler storage ring (CSRm) equipped with electron coolers has been developed at Lanzhou, China, and it provides an ideal research platform for electron-ion recombination studies of highly charged ions [16]. The recent reviews about DR experiments at storage rings have been given by [13][14][15]. ...
... For the electron-ion recombination experiments on argon ions by employing storage rings, only few experimental results are available, i.e. Ar 7+ [22,23], Ar 13+ [24][25][26], Ar 14+ [27], Ar 15+ [16,28], Ar 16+ [29]. In addition to the measurements of electron-ion recombination of argon ions at storage rings, the argon ions of Ar 16+ , Ar 17+ , and Ar 18+ have been investigated by using electron beam ion source [30,31] and electron beam ion trap [29,32], respectively. ...
... The recombination measurement was performed at the electron cooler of main cooler storage ring (CSRm) at the Institute of Modern Physics in Lanzhou, China. The details of the experimental technique and setup have been given elsewhere [16,33,34]. Here, most relevant aspects of electron-ion recombination experiment of C-like 40 Ar 12+ are described. ...
