Recombination of Ar^(14+), Ar^(15+), Ca^(16+), and Ni^(19+) ions with electrons has been investigated at low energy range based on the merged-beam method at the main cooler storage ring CSRm in the Institute of Modern...Recombination of Ar^(14+), Ar^(15+), Ca^(16+), and Ni^(19+) ions with electrons has been investigated at low energy range based on the merged-beam method at the main cooler storage ring CSRm in the Institute of Modern Physics, Lanzhou,China. For each ion, the absolute recombination rate coefficients have been measured with electron–ion collision energies from 0 meV to 1000 meV which include the radiative recombination(RR) and also dielectronic recombination(DR)processes. In order to interpret the measured results, RR cross sections were obtained from a modified version of the semiclassical Bethe and Salpeter formula for hydrogenic ions. DR cross sections were calculated by a relativistic configuration interaction method using the flexible atomic code(FAC) and AUTOSTRUCTURE code in this energy range. The calculated RR + DR rate coefficients show a good agreement with the measured value at the collision energy above 100 meV.However, large discrepancies have been found at low energy range especially below 10 meV, and the experimental results show a strong enhancement relative to the theoretical RR rate coefficients. For the electron–ion collision energy below 1 meV, it was found that the experimentally observed recombination rates are higher than the theoretically predicted and fitted rates by a factor of 1.5 to 3.9. The strong dependence of RR rate coefficient enhancement on the charge state of the ions has been found with the scaling rule of q^(3.0), reproducing the low-energy recombination enhancement effects found in other previous experiments.展开更多
近年来,基于重离子冷却储存环气体内靶,在逆运动学下,发展出了开展轻粒子诱发直接核反应的新实验技术.该技术弥补了常规实验的一些缺陷,具有低动量灵敏、高探测效率和低本底的特点,适合于开展物理化学性质易变材料和放射性同位素的研究...近年来,基于重离子冷却储存环气体内靶,在逆运动学下,发展出了开展轻粒子诱发直接核反应的新实验技术.该技术弥补了常规实验的一些缺陷,具有低动量灵敏、高探测效率和低本底的特点,适合于开展物理化学性质易变材料和放射性同位素的研究.本文介绍了国际上该类研究的现状,阐述了2016年以来中国科学院近代物理研究所依托大科学装置兰州重离子冷却储存环(cooler-storage ring at the heavy ion research facility in Lanzhou,HIRFLCSR)开展气体内靶核反应研究取得的进展,着重描述了储存环气体内靶核反应谱仪关键探测单元的研发和利用谱仪开展的首次质子在^(58)Ni上的低动量转移弹性散射实验.最后,介绍了开展碱金属^(133)Cs核物质密度分布半径测量的意义,以及未来HIRFL-CSR气体内靶核反应谱仪的研究方向.展开更多
The concept of isochronous mass spectrometry （IMS） applying two time-of-flight （TOF） detectors originated many years ago at GSI. However, the corresponding method for data analysis has never been discussed in deta...The concept of isochronous mass spectrometry （IMS） applying two time-of-flight （TOF） detectors originated many years ago at GSI. However, the corresponding method for data analysis has never been discussed in detail. Recently, two TOF detectors have been installed at CSRe and the new working mode of the ring is under test. In this paper, a data analysis method for this mode is introduced and tested with a series of simulations. The results show that the new IMS method can significantly improve mass resolving power via the additional velocity information of stored ions. This improvement is especially important for nuclides with Lorentz factor γ-value far away from the transition point yt of the storage ring CSRe.展开更多
The accuracy of dielectronic recombination （DR） data for astrophysics related ions plays a key role in astrophysical plasma modeling. The absolute DR rate coefficient of Fe^17＋ ions was measured at the main cooler ...The accuracy of dielectronic recombination （DR） data for astrophysics related ions plays a key role in astrophysical plasma modeling. The absolute DR rate coefficient of Fe^17＋ ions was measured at the main cooler storage ring at the Institute of Modern Physics, Lanzhou, China. The experimental electron-ion collision energy range covers the first Rydberg series up to n = 24 for the DR resonances associated with the 2p1/2 →^2 p3/2△n= 0 core excitations. A theoretical calculation was performed by using FAC code and compared with the measured DR rate coefficient. Overall reasonable agreement was found between the experimental results and calculations. Moreover, the plasma rate coefficient was deduced from the experimental DR rate coefficient and compared with the available results from the literature. At the low energy range, significant discrepancies were found, and the measured resonances challenge state-of-the-art theory at low collision energies.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0402300)the National Natural Science Foundation of China(Grant Nos.U1932207,11904371,and U1732133)。
文摘Recombination of Ar^(14+), Ar^(15+), Ca^(16+), and Ni^(19+) ions with electrons has been investigated at low energy range based on the merged-beam method at the main cooler storage ring CSRm in the Institute of Modern Physics, Lanzhou,China. For each ion, the absolute recombination rate coefficients have been measured with electron–ion collision energies from 0 meV to 1000 meV which include the radiative recombination(RR) and also dielectronic recombination(DR)processes. In order to interpret the measured results, RR cross sections were obtained from a modified version of the semiclassical Bethe and Salpeter formula for hydrogenic ions. DR cross sections were calculated by a relativistic configuration interaction method using the flexible atomic code(FAC) and AUTOSTRUCTURE code in this energy range. The calculated RR + DR rate coefficients show a good agreement with the measured value at the collision energy above 100 meV.However, large discrepancies have been found at low energy range especially below 10 meV, and the experimental results show a strong enhancement relative to the theoretical RR rate coefficients. For the electron–ion collision energy below 1 meV, it was found that the experimentally observed recombination rates are higher than the theoretically predicted and fitted rates by a factor of 1.5 to 3.9. The strong dependence of RR rate coefficient enhancement on the charge state of the ions has been found with the scaling rule of q^(3.0), reproducing the low-energy recombination enhancement effects found in other previous experiments.
文摘近年来,基于重离子冷却储存环气体内靶,在逆运动学下,发展出了开展轻粒子诱发直接核反应的新实验技术.该技术弥补了常规实验的一些缺陷,具有低动量灵敏、高探测效率和低本底的特点,适合于开展物理化学性质易变材料和放射性同位素的研究.本文介绍了国际上该类研究的现状,阐述了2016年以来中国科学院近代物理研究所依托大科学装置兰州重离子冷却储存环(cooler-storage ring at the heavy ion research facility in Lanzhou,HIRFLCSR)开展气体内靶核反应研究取得的进展,着重描述了储存环气体内靶核反应谱仪关键探测单元的研发和利用谱仪开展的首次质子在^(58)Ni上的低动量转移弹性散射实验.最后,介绍了开展碱金属^(133)Cs核物质密度分布半径测量的意义,以及未来HIRFL-CSR气体内靶核反应谱仪的研究方向.
基金Supported by the 973 Program of China(2013CB834401)National Nature Science Foundation of China(U1232208,U1432125,11205205,11035007)the Helmholtz-CAS Joint Research Group(Group No.HCJRG-108)
文摘The concept of isochronous mass spectrometry （IMS） applying two time-of-flight （TOF） detectors originated many years ago at GSI. However, the corresponding method for data analysis has never been discussed in detail. Recently, two TOF detectors have been installed at CSRe and the new working mode of the ring is under test. In this paper, a data analysis method for this mode is introduced and tested with a series of simulations. The results show that the new IMS method can significantly improve mass resolving power via the additional velocity information of stored ions. This improvement is especially important for nuclides with Lorentz factor γ-value far away from the transition point yt of the storage ring CSRe.
基金Supported by the National Key R&D Program of China(2017YFA0402300)the National Natural Science Foundation of China through(11320101003,U1732133,11611530684)Key Research Program of Frontier Sciences,CAS(QYZDY-SSW-SLH006)
文摘The accuracy of dielectronic recombination （DR） data for astrophysics related ions plays a key role in astrophysical plasma modeling. The absolute DR rate coefficient of Fe^17＋ ions was measured at the main cooler storage ring at the Institute of Modern Physics, Lanzhou, China. The experimental electron-ion collision energy range covers the first Rydberg series up to n = 24 for the DR resonances associated with the 2p1/2 →^2 p3/2△n= 0 core excitations. A theoretical calculation was performed by using FAC code and compared with the measured DR rate coefficient. Overall reasonable agreement was found between the experimental results and calculations. Moreover, the plasma rate coefficient was deduced from the experimental DR rate coefficient and compared with the available results from the literature. At the low energy range, significant discrepancies were found, and the measured resonances challenge state-of-the-art theory at low collision energies.
