基于重离子储存环建立的等时性质谱术（IMS）是测量远离稳定线核素质量的有效工具。但是，采用常规IMS测量缺中子一侧的核素质量时，发现T z =-1/2和T z =-1核素的质量测量结果在宽时域范围内存在系统性偏差。本工作利用CSRe直线段上的双飞行时间（TOF）探测器，同时测量了循环离子的周期和速度。利用这些实验信息，对常规IMS质量测量中出现的系统性偏差进行了研究。发现系统偏差是由于储存的离子动量分布不对称以及储存环能量转变参数γ t 非恒定造成的。在离线数据处理时，发现通过限制动量接收度的大小，可以消除常规IMS质量测量中的系统偏差。这一结果对采用常规IMS进行质量测量具有重要参考价值和指导意义。

The penalized least squares (PLS) method with appropriate weights has proved to be a successful baseline estimation method for various spectral analyses. It can extract the baseline from the spectrum while retaining the signal peaks in the presence of random noise. The algorithm is implemented by iterating over the weights of the data points. In this study, we propose a new approach for assigning weights based on the Bayesian rule. The proposed method provides a self-consistent weighting formula and performs well, particularly for baselines with different curvature components. This method was applied to analyze Schottky spectra obtained in $$^{86}$$ Kr projectile fragmentation measurements in the experimental Cooler Storage Ring (CSRe) at Lanzhou. It provides an accurate and reliable storage lifetime with a smaller error bar than existing PLS methods. It is also a universal baseline-subtraction algorithm that can be used for spectrum-related experiments, such as precision nuclear mass and lifetime measurements in storage rings.

Isochronous mass spectrometry (IMS) of heavyion storage rings is a powerful tool for the mass measurements of short-lived nuclei. In IMS experiments, masses are determined through precision measurements of the revolution times of the ions stored in the ring. However, the revolution times cannot be resolved for particles with nearly the same mass-to-charge (m/q) ratios. To overcome this limitation and to extract the accurate revolution times for such pairs of ion species with very close m/q ratios, in our early work on particle identification, we analyzed the amplitudes of the timing signals from the detector based on the emission of secondary electrons. Here, the previous data analysis method is further improved by considering the signal amplitudes, detection efficiencies, and number of stored ions in the ring. A sensitive Z-dependent parameter is introduced in the data analysis, leading to a better resolution of ^34Ar^18+ and ^51Co^27+ with A/Z=17/9. The mean revolution times of ^34Ar^18+ and ^51Co^27+ are deduced, although their time difference is merely 1.8 ps. The uncorrected, overlapped peak of these ions has a full width at half maximum of 7.7 ps. The mass excess of ^51Co was determined to be -27332(41) keV, which is in agreement with the previous value of -27342(48) keV.

Isochronous mass spectrometry (IMS) of heavy-ion storage rings is a powerful tool for the mass measurements of short-lived nuclei. In IMS experiments, masses are determined through precision measurements of the revolution times of the ions stored in the ring. However, the revolution times cannot be resolved for particles with nearly the same mass-to-charge (m/q) ratios. To overcome this limitation and to extract the accurate revolution times for such pairs of ion species with very close m/q ratios, in our early work on particle identification, we analyzed the amplitudes of the timing signals from the detector based on the emission of secondary electrons. Here, the previous data analysis method is further improved by considering the signal amplitudes, detection efficiencies, and number of stored ions in the ring. A sensitive Z-dependent parameter is introduced in the data analysis, leading to a better resolution of $$^{34}$$ Ar $$^{18+}$$ and $$^{51}$$ Co $$^{27+}$$ with $$A/Z=17/9$$ . The mean revolution times of $$^{34}$$ Ar $$^{18+}$$ and $$^{51}$$ Co $$^{27+}$$ are deduced, although their time difference is merely 1.8 ps. The uncorrected, overlapped peak of these ions has a full width at half maximum of 7.7 ps. The mass excess of $$^{51}$$ Co was determined to be $$-27{,}332(41)$$ keV, which is in agreement with the previous value of $$-27{,}342(48)$$ keV.

根据几种常用放射性核素的寿命计算方法,通过模拟数据研究了直接拟合法、对数时间法、极大似然法、观测时间受限时的极大似然法等四种寿命计算方法的适用范围。当观测时间不受限时,研究了在不同计数下寿命计算方法的适用范围。当观测时间受限时,研究了在不同观测时间窗口下寿命计算方法的适用范围。模拟中选用全剥离离子 94m Ru 44+ 作为目标核素,得到了不同计数及不同观测时间窗口下的寿命及其误差,并给出了四种方法的适用范围。 94m Ru 44+ 寿命的模拟结果与在兰州等时性质量谱仪上获得的实验结果在一倍标准偏差范围内一致,从而进一步验证了寿命计算方法的适用范围及模拟数据的可靠性。该模拟结果可为寿命测量实验设计提供理论依据和参考。

A foil–microchannel plate (MCP) detector, which uses electrostatic lenses and possesses both good position and timing resolutions, has been designed and simulated for beam diagnostics and mass measurements at the next-generation heavy-ion-beam facility HIAF in China. Characterized by low energy loss and good performances of timing and position measurements, it would be located at focal planes in fragment separator HFRS for position monitoring, beam turning, $$B{\rho }$$ measurement, and trajectory reconstruction. Moreover, it will benefit the building-up of a magnetic-rigidity–energy-loss–time-of-flight ( $$B{\rho }{{-}}{\Delta }{E}{{-}}\mathrm{TOF}$$ ) method at HFRS for high-precision in-flight particle identification of radioactive isotope beams on an event-by-event basis. Most importantly, the detector can be utilized for in-ring TOF and position measurements, beam-line TOF measurements at two achromatic foci, and position measurements at a dispersive focus of HFRS, thus making it possible to use two complementary mass measurement methods [isochronous mass spectrometry at the storage ring SRing and magnetic-rigidity–time-of-flight ( $$B{\rho }{{-}}\mathrm{TOF}$$ ) at the beam-line HFRS] in one single experimental run.

Isochronous mass spectrometry has been applied to 112Sn projectile fragments at the HIRFL-CSR facility in Lanzhou. To produce short-lived nuclei of interest, we used projectile fragmentation of 112Sn35+ primary beams in a ～10 mm thick 9Be production target. The fragments were selected and analyzed by RIBLL2 and injected into the experimental storage ring(CSRe) every 25 s. To measure revolution times of stored ions,we used a Time-Of-Flight detector installed in CSRe. A new particle identification method was developed to distinguish ions on the measured revolution time spectrum for each injection. Based on this method, the shifts of the revolution time due to instable dipole magnet fields can be corrected and the ground and isomeric states of 101In have been well-resolved. The measured excitation energy is consistent with the theoretical value in the error range of 112 keV. The lifetime of the isomeric states of 101In is more than 200 μs.

Combining our newly measured masses of ground and (2(+)) isomeric states of Co-52 with previous measurements of Ni-52 beta decay, a remarkably different decay scheme of Ni-52 is constructed. In the new scheme, the proton group with the highest intensity corresponds to the decay from the 1(+) excited state in Co-52, and not from the J(pi) = 0(+); T = 2 isobaric analog state (IAS) as it was commonly assumed. This finding indicates that the degree of isospin impurity in the lowest T = 2 IAS in Co-52 is extremely small, thus leading to a negligibly weak proton emission from the IAS and a mistaken assignment. Effort to find an explanation for this phenomenon is highly called for.

The decay of the fully stripped ion 94mRu44+ in the order of one hundred microseconds has been studied for the first time by using the Isochronous Mass Spectrometry (IMS) at the HIRFL-CSR facility in Lanzhou.94mRu44+ waS produced via projectile fragmentation of a 112Sn primary beam bombarding on a 9Be production target.After the in-flight separation with RIBLL2,the ions were injected into the experimental ring (CSRe) and then stored there.The revolution times of the stored ions were measured by a Time-of-Flight (TOF) detector.Due to the mass change of a 94mRu44+ ion caused by its de-excitation to the ground state,hence the revolution time change,the decay process of 94mRu44+ could be directly observed in the CSRe.The sensitive window for detection of the decay events and the measurement precision of the decay time have been determined in this work.At the same time,we measured the mass of short-lived 94mRu44+ with the half-life about one hundred microseconds,which is the shortest among nuclides that have been studied by using storage-ring mass-spectrometry.

Recent results and progress of mass measurements of neutron-rich nuclei utilizing Isochronous Mass Spectrometry (IMS) based on the HIRFL-CSR complex at Lanzhou are reported. The nuclei of interest were produced through projectile fragmentation of primary 86Kr ions at a realistic energy of 460.65 MeV/u. After in-flight separation by the fragment separator RIBLL2, the fragments were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of their revolution times. The re-determined masses were compared and evaluated with other mass measurements, and the impact of these evaluated masses on the shell evolution study is discussed.

The combination of in-flight fragment separator and the isochronous mass spectrometry（IMS）in storage rings have been proven to be a powerful tool for the precision mass measurements of shortlived exotic nuclei. In IMS, the mass-over-charge ratio is only related to the revolution period of stored ions, and the relative mass resolution can reach up to the order of 10-6. However, the instability of the magnetic field of storage ring deteriorates the resolution of revolution period, making it very difficult to distinguish the ions with very close mass-over-charge ratio via their revolution periods. To improve the resolution of revolution periods, a new method of weighted shift correction（WSC） has been developed to accurately correct the influence of the magnetic field instabilities in the isochronous mass measurements of 58Ni projectile fragments. By using the new method, the influence of unstable magnetic fields can be greatly reduced, and the mass resolution can be improved by a factor up to 1.7. Moreover, for the ions that still cannot be distinguished after correcting the magnetic field instabilities, we developed a new method of pulse height analysis for particle identification. By analyzing the mean pulse amplitude of each ion from the timing detector, the stored ions with close mass-over-charge ratios but different charge states such as 34Ar and 51Co can be identified, and thus the mass of 51Co can be determined. The charge-resolved IMS may be helpful in the future experiments of isochronous mass measurement even for N = Z nuclei.

The isochronous Mass Spectrometry(IMS) is a powerful experimental instrument for measuring masses of short-lived nuclides. In the IMS, the nuclides of interest are produced via the projectile fragmentation reaction, then injected into the storage ring after the in-flight separation with beam line. The yields of the nuclides of interest are usually very small accompanying a huge amount of contaminant nuclides, aggravating the load of time-of-flight(TOF) detector. In the IMS nuclear mass measurement experiment conducted at the HIRFL-CSR, we developed a method of purifying the secondary beam fragments to ease the burden of the TOF detector, which is based on the differences of the ions′ velocities in the beam line and realized by adjusting the injection time of secondary fragments using the Kicker system of the HIRFL-CSR. We tested and verified the method in an online experiment, and its performance is discussed in this paper.

In this paper, we present direct mass measurements of neutron-rich86 Kr projectile fragments conducted at the HIRFL-CSR facility in Lanzhou by employing the Isochronous Mass Spectrometry(IMS) method. The new mass excesses of52-54 Sc nuclides are determined to be-40492(82),-38928(114),-34654(540) ke V, which show a significant increase of binding energy compared to the reported ones in the Atomic Mass Evaluation 2012(AME12).In particular,53 Sc and54Sc are more bound by 0.8 Me V and 1.0 Me V, respectively. The behavior of the two neutron separation energy with neutron numbers indicates a strong sub-shell closure at neutron number N =32 in Sc isotopes.

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 γ _t of the storage ring CSRe.

Masses of neutron-deficient Ni-58 projectile fragments have been measured at the HIRFL-CSR facility in Lanzhou, China employing the isochronous mass spectrometry technique. Masses of a series of short-lived T-z = -3/2 nuclides including the Cr-45 nucleus have been measured with a relative uncertainty of about 10(-6)-10(-7). The new Cr-45 mass turned out to be essential for modeling the astrophysical rp-process. In particular, we find that the formation of the predicted Ca-Sc cycle in X-ray bursts can be excluded.

In this paper, we report the synthesis of four diimine ligands incorporated with an electron donor/acceptor, as well as their corresponding Cu(I) complexes with bis(2-(diphenylphosphanyl)phenyl) ether as an ancillary ligand, resulting in four phosphorescent Cu(I) complexes. Their crystal structures as well as photophysical and thermal properties are discussed in detail. Experimental data and theoretical calculations confirm that electron donor moieties and limited conjugation system may self-restrict geometry relaxation in excited states, leading to narrowed and blue-shifted emission bands. On the other hand, electron acceptor moieties and large coplanar conjugation system are ineffective in restricting geometry relaxation, leading to broadened and red-shifted emission bands. However, the introduction of electron donors compromises thermal stability of Cu(I) complexes. We also explore one of the Cu(I) complexes as a dopant for electroluminescence application, and a maximum luminance of 680cd/m2 peaking at 620nm is achieved.