Control and data acquisition system for collinear laser spectroscopy experiments

Control and data acquisition system for collinear laser spectroscopy experiments 1 first-author https://orcid.org/http://orcid.org/0000-0001-9836-2808 1 corresp [ ] xiaofei.yang@pku.edu.cn [ ] xiaofei.yang@pku.edu.cn xiaofei.yang@pku.edu.cn https://orcid.org/http://orcid.org/0000-0002-1633-4000 1 https://orcid.org/http://orcid.org/0000-0002-6087-9788 1 1 1 1 1 1 1 1 1 2 1 https://orcid.org/http://orcid.org/0000-0001-8938-9152 1 2 School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China China Institute of Atomic Energy (CIAE), P.O. Box 275(10), Beijing 102413, China China Institute of Atomic Energy (CIAE), P.O. Box 275(10), Beijing 102413, China A control and data acquisition system was implemented for the recently-developed collinear laser spectroscopy setup. This system is dedicated to data recording, storage, processing, monitoring of the beam intensity and energy, and visualization of various spectra. In comparison to the conventional resonance nuclear reaction system, the key technique is the precise synchronization of the detected counts with the actual scanning voltage (or probing laser frequency). The functions of the system were tested by measuring the hyperfine structure spectra of stable calcium (e.g. 40 Ca + ) and radioactive potassium (e.g. 38 K) in the bunched and continuous modes, respectively. This system will be routinely applied and further improved in subsequent laser spectroscopy experiments on unstable isotopes at the Beijing Radioactive Ion-beam Facility (BRIF). Collinear laser spectroscopy Hyperfine structure Data acquisition system Voltage scanning Introduction 1 Nuclear properties, such as nuclear spins, electromagnetic moments, and charge radii, are essential for studying exotic structural phenomena that emerge in unstable isotopes [ 1 1 - 3 3 1-3 ] and for testing the present nuclear theoretical models [ 4 4 - 8 8 4-8 ]. Collinear laser spectroscopy (CLS) has proven to be a powerful experimental tool for investigating the nuclear properties of unstable nuclei based on probing the hyperfine structure (HFS) and isotope shifts of their atoms, ions, or molecules [ 9 9 , 10 10 ]. Thus, various CLS setups have been broadly used at radioactive ion beam (RIB) facilities worldwide [ 11 11 - 17 17 11-17 ]. Recently, a CLS setup was developed and commissioned [ 19 19 , 18 18 ] to study the nuclear structure of unstable nuclei at RIB facilities in China, such as the Beijing Radioactive Ion-beam Facility (BRIF) [ 20 20 ] and the High Intensity Heavy-ion Accelerator Facility (HIAF) [ 21 21 ]. In a typical CLS experiment, the HFS spectrum of the isotope of interest is measured by tuning the velocity of the ion or atom beam (also known as Doppler tuning) via voltage scanning [ 14 14 , 18 18 ] or by varying the frequency of the probing laser [ 17 17 ]. More specifically, in a configuration in which fast (tens of keV) ions or atom beams are anti-collinearly overlapped with a high-resolution probing laser beam at a fixed frequency ν 0 , the moving ions or atoms experience a Doppler-shift frequency according to <math display="block" id="M1"><mrow><mi>ν</mi><mo>=</mo><msub><mi>ν</mi><mn>0</mn></msub><mo>×</mo><msqrt><mrow><mfrac><mrow><mn>1</mn><mo>+</mo><mi>β</mi></mrow><mrow><mn>1</mn><mo>−</mo><mi>β</mi></mrow></mfrac></mrow></msqrt><mn>,</mn><mi>β</mi><mo>=</mo><msqrt><mrow><mn>1</mn><mo>−</mo><mfrac><mrow><msup><mi>m</mi><mn>2</mn></msup><msup><mi>c</mi><mn>4</mn></msup></mrow><mrow><msup><mrow><mo stretchy="false">(</mo><mi>E</mi><mo>+</mo><mi>m</mi><msup><mi>c</mi><mn>2</mn></msup><mo stretchy="false">)</mo></mrow><mn>2</mn></msup></mrow></mfrac></mrow></msqrt><mn>.</mn></mrow></math> Here, E and m are the total kinetic energy and mass of the ion and atom, respectively. In the case of voltage scanning, which is largely used in CLS experiments [ 11 11 - 16 16 11-16 ], the moving ion or atom with a variable energy ( E ) can be laser-resonantly excited to a higher state and subsequently de-excited by emitting fluorescent photons. These laser-induced fluorescence (LIF) photons, which are suddenly enhanced at the resonance energy, are detected by a photon detection system. The photons counted as a function of the beam energy (Doppler shift frequency) yield a physically meaningful HFS spectrum. To ensure the success of a CLS experiment using the Doppler tuning (voltage scanning) approach, a dedicated, robust, and user-friendly control and data acquisition (DAQ) system is indispensable. The system must accomplish various functions, such as controlling the scanning voltage, recording the energy of the ion beam, counting photons when scanning voltage, and recording the time of flight (TOF) of the beam in the bunched mode. We note here the major difference between the control and DAQ systems for the CLS system in comparison with the conventional resonance nuclear reaction system. In a resonance nuclear reaction experiment, the beam energy is normally fixed for one measurement (it can be changed for subsequent measurements), whereas the beam intensity (or luminosity) must be monitored and used for yield normalization [ 22 22 ]. In the CLS experiment, a fast energy-tuning (via voltage scanning) technique is employed to avoid the influence of the variation in beam intensity. Naturally, the key problem in a CLS experiment is the precise synchronization of the detected counts with the actual beam energy. This is also the most important issue in the present control and DAQ systems. In this study, we present the details of the control and DAQ systems that have been implemented for recently developed CLS setups [ 19 19 , 18 18 ]. The functions and performance of the system have been fully tested and validated by two independent experimental measurements of the optical spectrum using a calcium beam (e.g. 40 Ca + ) in bunched mode [ 18 18 ] and the HFS spectrum using an unstable potassium beam (e.g. 38 K) in continuous mode [ 19 19 ]. This system will be routinely used and further updated for future laser spectroscopy experiments of stable nuclei at the offline laboratory or of unstable nuclei at BRIF facility. System description 1 The upper part of Fig. 1 Fig. 1 shows a schematic of the CLS setup recently commissioned at the offline laboratory of Peking University [ 18 18 ] and at the BRIF RIB facility [ 19 19 ]. Details of this setup are available in Refs. [ 18 18 , 19 19 ]. The related hardware components and logic of the control and DAQ systems are presented in Fig. 1(a) and (b) Fig. 1(a) and (b) , respectively. A voltage scanning system (red shaded area) is used for tuning the ion beam energy before neutralization in the charge-exchange chamber. The DAQ system (green shaded area) is used to record, store, and process the photon or ion events detected by photomultiplier tubes (PMTs) or MagneTOF detectors, respectively. The timing TTL signal generated by the pulse generator provides the trigger reference (blue-shaded area) of the entire system. A software program written in Python is implemented to control all the hardware units involved, analyze the recorded data, and construct the HFS spectrum of the studied isotope. DAQ system 2 As shown in Fig. 1(a) Fig. 1(a) (green shaded area), the collection and processing of the signals from the PMTs and MagneTOF detector are realized through a series of NIM modules, such as a fast timing amplifier (ORTEC FTA 820A) and constant-fraction discriminator (CAEN N605). The bias voltages for the PMTs and MagneTOF detector are provided by high-voltage (HV) power suppliers (CAEN N1470). The signals processed by these NIM modules are further transformed into TTL signals before being sent to a time-to-digital converter (TDC: ChronoLogic TimeTagger4-2G) with a time resolution of 500 ps. The TDC has four independent input channels in addition to a trigger channel. The corresponding timing sequence for these channels is shown in Fig. 2 Fig. 2 . After receiving a trigger signal ( T 0 ; trigger frequency: e.g., 100 Hz), a user-defined time window (i.e., Δ T < 10 ms) is opened for each input channel of TDC. Event signals from detectors arriving within Δ T are recorded and stored in the buffer zone of TDC. For each recorded event signal, information on its arrival time (time tagging) relative to T 0 , input channel, and trigger number since the start of TDC are recorded and saved. The events that occurred outside Δ T are excluded. For a typical experiment in this work, where the ion beam is produced in bunched mode by an offline laser ablation ion source [ 18 18 ], the timing sequence for each involved device is shown in Fig. 3 Fig. 3 . A 532-nm Nd: YAG pulsed laser (Litron TRLi 250-100) with a repetition rate of 100Hz is used to drive the ablation ion source. This pulsed laser (named ablation laser) is externally triggered by a TTL signal from a Quantum Composers (QC9528) digital-delay pulse generator ( QC). The TDC is then triggered by a TTL signal that was t ’ μs later than the ablation laser pulse. At the beginning of a CLS experiment, t ’ must be adjusted such that the ion beam pulses (approximately 10 μs duration [ 18 18 ] in the present work) appear within the TDC time window (Δ T ), corresponding to the estimated time for the ion beam pulse passing in front of the PMTs. Thus, the sensitivity (or signal-to-noise ratio) of the CLS experiment can be significantly improved in comparison to that performed with a continuous ion beam [ 3 3 , 5 5 , 12 12 , 18 18 ]. This is because of the limited background events recorded within the narrow TDC time window Δ T (e.g., approximately 100 μs [ 18 18 ]), out of the average period of 10 ms between two pulses. The background events can be further suppressed by gating on the narrow TOF gate ( ∼ 10 μs) of the ion bunch, as detailed in Sect. 3.1. However, when an ion beam is delivered in continuous mode, such as that in Ref. [ 19 19 ], the TDC is triggered by a high-frequency TTL signal (e.g., 1 kHz). To avoid any event loss, the time window for TDC is set as Δ T =1 ms. Therefore, the measurement of the HFS spectrum with a continuous beam involves recording all signals coming from the detectors, including all background signals that may result from events such as the random scattering laser light, de-excitation after non-resonant collision excitation, and PMT dark current. Voltage scanning system 2 As mentioned above, in a CLS experiment, the HFS spectra of the isotope of interest can be measured by counting the LIF photons as a function of the probing laser frequency or scanning voltage. In the former case, the frequency of the laser can be tuned using a laser frequency control software and by a high-precision wavelength meter [ 17 17 ]. The program for the control and DAQ system must synchronize the probing laser frequency and the corresponding LIF photons to achieve HFS measurements. The scanning speed and step size of the probing laser frequency are often limited by the laser system and must be handled well. In fact, rapid tuning of the probing laser frequency with a large step size and a wide frequency range may cause loss of the lock of the laser cavity, which will strongly affect the laser stability and the measurement of the HFS spectrum. Nevertheless, these limitations can be overcome by using the following Doppler tuning approach. In this approach, the velocity of the ion beam is varied by changing the voltage applied to the voltage scanning electrode mounted upstream of the charge exchange cell, as shown in Fig. 1 Fig. 1 . The applied voltage is preliminarily provided by a USB device (USB-3106, Measurement Computing), which is remotely controlled by the control and DAQ system. The output voltage of the USB-3106 ranges from -10 V to 10 V with a typical slew rate of 1.2 v/μs and typical duration of 5 μs, allowing fast voltage scanning. The output signal of the USB device is then linearly amplified via a DC HV amplifier (Trek 623 B) with a gain of 1000, maximum voltage scanning range of ± 2 kV, and slew rate greater than 300 v/μs. The amplified voltage is then applied to the voltage-scanning electrode to change the velocity of the ions. The program also records the applied voltage in real time using a voltage divider (Ohm-labs, KV-10A) and digital multimeter (Keysight 34470A) [ 19 19 ], as shown in Fig. 1 Fig. 1 . Synchronization of voltage scanning with TDC events 2 An important application of the control and DAQ system is the measurement of the HFS spectrum using the voltage scanning technique, which involves recording LIF photons as a function of the scanning voltage. Because the latter is repeatedly varied in small steps, its precise synchronization with photon recording is crucial. Naturally, one would expect that a straightforward method would involve changing the voltage at an equal step size δ V after equal intervals of time δ T , as illustrated by Method 1” in Fig. 4(a) Fig. 4(a) . However, the time required for the program to execute each read” function, which reads the data from the buffer zone of the TDC, depends on the actual computational load and is not necessarily synchronized to the external trigger or each voltage step. Thus, this method ( Method 1”) can lead to a mismatch between the read data and each voltage step, as indicated by black diamonds in Fig. 4(a) Fig. 4(a) . This results in a measured spectrum that deviates from the real statistics. The Method 2” shown in Fig. 4(b) Fig. 4(b) was adopted to overcome this problem. In this method, the control and DAQ systems subjectively switch the voltage after executing a certain number of read” function ( n ×read” with n a fixed number). Each n × read” corresponds to a clearly fixed scan voltage, but not necessarily the same time period, as shown in Fig. 4(b) Fig. 4(b) . Thus, for each voltage step ( δ V ) or n × read” step, the counts must be normalized to the number of covered triggers (namely, counts/trigger or count rate) before being used to plot the HFS spectrum (further details are provided in Sect. 3.1). Operation of the control and DAQ system 1 The program for the control and DAQ system was developed based on the Python language, which allows us to satisfy the various requirements for CLS measurement. Figure 5 Figure 5 illustrates the graphical user interface (GUI) of the overall system. The major functions of this program are indicated by the windows on the left side of Fig. 5 Fig. 5 . Prior to starting a new measurement, we preset the scan parameters, for example, voltage scanning range, step size of the voltage, time duration, or number of read” for each step, and total number of scans, which are realized by using Scan Setting” window in the GUI ( Fig. 5 Fig. 5 ). The window Voltage Scanning” in Fig. 5 Fig. 5 allows us to start and stop a measurement and visualize the HFS and TOF spectra in real time according to the actual setting. All scan statuses for a measurement are also displayed in real time at the bottom of the GUI. In the CLS experiment, the accuracy and stability of the applied scanning voltage are ensured by calibrating the HV amplifier ( Fig. 1 Fig. 1 ) regularly using the function of “HV Calibration”. During a measurement, to monitor any unexpected variation, such as a sudden drop in the ion beam intensity, loss of the laser cavity, or failure of the HV power supply, the related parameters are displayed in a timely manner using the Real-time Plotting” function. The program and GUI were tested and validated in two independent experiments, as described below. HFS measurement using voltage scanning 2 The control and DAQ systems were first applied to the measurement of the optical spectrum of the stable 40 Ca + produced in the bunched mode by a laser ablation ion source. As shown at the top of Fig. 1(a) Fig. 1(a) , the bunched 40 Ca ions with varying velocity (scanning voltage) can be resonantly excited in the photon detection region because of the interaction with a continuous-wave probing laser at a fixed frequency. The scanning voltage in this measurement was set to a range of 25 V, with a step size and step duration of 0.25 V and 0.02 s, respectively. The LIF photons were detected by the PMTs and processed by the NIM electronics before being sent to the TDC ( Fig. 1(b) Fig. 1(b) ). As depicted in Fig. 3 Fig. 3 , only signals arriving within the TDC time window (100 μ s in this measurement) were recorded. Thus, the background signals that primarily arise from the scattered laser light and PMT dark counts, were significantly reduced. The TOF spectrum of the bunched beam was obtained by plotting the LIF photon counts as a function of their arrival time relative to the start of the TDC time window, as shown in Fig. 6(b) Fig. 6(b) ). The optical spectrum of 40 Ca was obtained by plotting the LIF photon counts arriving within the TOF gate ( indicated by the vertical red lines in Fig. 6(b) Fig. 6(b) ) as a function of the scanning voltage. Figure 6(a) Figure 6(a) presents the measured optical spectrum of 40 Ca + after Doppler correction and voltage-frequency conversion according to Eq. 1. It should be noted that the spectra in Fig. 6(a) Fig. 6(a) were measured using Method 1, as discussed in Sect. 2.3 and Fig. 4(a) Fig. 4(a) , indicating that the voltage was switched by an equal step size δ V after an equal time interval δ T . This may produce a mismatch between the triggers and voltage at the edge of every voltage step [see Sect. 2.3 and Fig. 4(a) Fig. 4(a) ]. However, this does not cause significant problems in the measured optical spectrum, as shown in Fig. 6(a) Fig. 6(a) owing to the relatively low count rate within the narrow TOF gate ( ∼ 10 μs) shown in Fig. 6(b) Fig. 6(b) , and hence a low computational load for the bunched ion mode. However, “Method 1” causes severe problems in the HFS spectrum of isotopes measured using continuous beams, for example, 38 K isotopes from BRIF [ 19 19 ], because hundreds or thousands of times more background events will be recorded by the TDC. To ensure the correct synchronization of photon events with the corresponding voltage step, the Method 2” in Fig. 4(b) Fig. 4(b) was adopted, which implies that the voltage change was initiated by the control and DAQ system after executing the read” function n times. An example of the recorded total number of triggers for each voltage step δ V is presented in Fig 7(a) Fig 7(a) , that shows the variation in the reading time for executing the same number of read” functions. This produces a large fluctuation in the total counts for each voltage step (converted into the relative frequency in Fig 7(b) Fig 7(b) ) owing to the reading time variation. In this case, only the normalized counts per trigger (or count rate) for each voltage step were meaningful. These were used to plot the HFS spectrum of the 38 K isotope ( Fig 7(c) Fig 7(c) ). For each scan, we calculated the counts per trigger (or count rate), for example, M i . The corresponding error in the counts per trigger (or count rate) M i should be handled based on <math display="block" id="M4"><mrow><mi>Δ</mi><msub><mi>M</mi><mi>i</mi></msub><mo>=</mo><mfrac><mrow><mi>Δ</mi><msub><mi>N</mi><mi>i</mi></msub></mrow><mrow><msub><mi>K</mi><mi>i</mi></msub></mrow></mfrac><mo>=</mo><mfrac><mrow><msqrt><mrow><msub><mi>N</mi><mi>i</mi></msub></mrow></msqrt></mrow><mrow><msub><mi>K</mi><mi>i</mi></msub></mrow></mfrac><mo>=</mo><mfrac><mrow><msqrt><mrow><msub><mi>M</mi><mi>i</mi></msub><msub><mi>K</mi><mi>i</mi></msub></mrow></msqrt></mrow><mrow><msub><mi>K</mi><mi>i</mi></msub></mrow></mfrac><mo>=</mo><msqrt><mrow><mfrac><mrow><msub><mi>M</mi><mi>i</mi></msub></mrow><mrow><msub><mi>K</mi><mi>i</mi></msub></mrow></mfrac></mrow></msqrt><mo>,</mo></mrow></math> where N i and K i are the count and number of triggers (or measurement time), respectively, for i th scan. Notably, although no significant difference in the resonance peak of 40 Ca + is observed in Fig. 6(a) Fig. 6(a) owing to the use of a bunched beam, only the Method 2” is now routinely used for CLS experiments on ion beams in both bunched and continuous modes [ 18 18 , 19 19 , 23 23 ]. HV amplifier calibration 2 As mentioned above, the amplification coefficient of the HV amplifier needs to be calibrated regularly to ensure that the correct voltage is applied during voltage scanning. The online calibration of the amplification coefficient was performed using the function of the HV Calibration” as shown in Fig. 5 Fig. 5 . During calibration, the voltage applied to the voltage scanning electrode (namely, the measured voltage) was recorded as a function of the input voltage (namely, the scanning voltage) for the HV amplifier, which was provided by the USB device and controlled by the program of the control and DAQ system. Figure 8 Figure 8 shows a typical example of the measured voltage versus scanning voltage ranging from -1.9 V to 1.9 V. The scanning range, voltage step size, and switch time for each step can be set in the GUI ( HV calibration” in Fig. 5 Fig. 5 ). By fitting the plot linearly, the amplification coefficient of the HV amplifier was measured, and the corresponding uncertainty was assessed. The actual linearity is excellent (see inset of Fig. 8 Fig. 8 ). Monitor of the relative beam intensity 2 In general, the HFS spectrum is measured over a long scanning time to obtain sufficient statistics. Thus, monitoring the stability of different parameters (e.g., probing laser frequency, applied voltage, and beam intensity) in real-time is of particular importance. This is accomplished using the function of Real-time Plotting” in the GUI of Fig. 5 Fig. 5 . An example is presented in Fig. 9 Fig. 9 for the relative beam intensity, corresponding to the ion counts measured by the MagneTOF detector mounted at the end of the CLS beamline ( Fig. 1(a) Fig. 1(a) ) [ 18 18 , 19 19 ]. During the HFS spectrum measurement, the signals from this detector were recorded by one of the four channels of the TDC and plotted as a function of time. This counting is very sensitive to variations in beam intensity, as shown in Fig. 9 Fig. 9 . The overlap of the probing laser beam with the ion beam can also be optimized. For example, LIF photon counts measured at a fixed scanning voltage corresponding to the position of the HFS resonance peak can be optimized with respect to the ion beam or probing laser beam adjustment. Summary and outlook 1 In summary, a control and DAQ system was implemented to realize multiple functions for a CLS-experiment, such as data collection, storage and processing, monitoring of the beam intensity and energy, and visualization of the HFS and TOF spectra. The key technique here was the precise synchronization of LIF photon counts with the actual scanning voltage (or probing laser frequency). By measuring the HFS spectra of a stable 40 Ca + beam in bunched mode and an unstable 38 K beam in continuous mode, these functions were investigated and optimized, exhibiting an overall satisfactory performance. Further improvements to the system are ongoing, and will be integrated with the program of beam tuning, monitoring of the vacuum system, simulation of the HFS spectrum, and online analysis. This system is expected to play an indispensable role in subsequent laser spectroscopy experiments of unstable isotopes at the BRIF facility, as well as in the following commissioning experiments for the new collinear resonance ionization laser spectroscopy. References W. Nörtershäuser , D. Tiedemann , M. Žáková et al. , Nuclear charge radii of 7,9,10 Be and the one-neutron halo nucleus 11 Be . Phys. Rev. Lett. 102 , 062503 ( 2009 ). doi: 10.1103/PhysRevLett.102.062503 http://doi.org/10.1103/PhysRevLett.102.062503 Nuclear charge radii of 7,9,10Be and the one-neutron halo nucleus 11Be K.T. Flanagan , P. Vingerhoets , M. Avgoulea et al. , Nuclear spins and magnetic moments of 71,73,75 Cu: Inversion of π 2p 3/2 and π 1f 5/2 levels in 75 Cu . Phys. Rev. Lett. 103 , 142501 ( 2009 ). doi: 10.1103/PhysRevLett.103.142501 http://doi.org/10.1103/PhysRevLett.103.142501 Nuclear spins and magnetic moments of 71,73,75Cu: Inversion of π2p3/2 and π1f5/2 levels in 75Cu X.F. Yang , C. Wraith , L. Xie et al. , Isomer shift and magnetic moment of the long-lived 1/2 + isomer in <math id="M5"><mrow><msubsup><mrow/><mrow><mn>30</mn></mrow><mrow><mn>79</mn></mrow></msubsup><msub><mrow><mtext>Zn</mtext></mrow><mrow><mn>49</mn></mrow></msub></mrow></math> : Signature of shape coexistence near 78 Ni . Phys. Rev. Lett. 116 , 182502 ( 2016 ). doi: 10.1103/PhysRevLett.116.182502 http://doi.org/10.1103/PhysRevLett.116.182502 Isomer shift and magnetic moment of the long-lived 1/2+ isomer in 3079Zn49: Signature of shape coexistence near 78Ni R.F. Garcia Ruiz , M.L. Bissell , K. Blaum et al. , Unexpectedly large charge radii of neutron-rich calcium isotopes . Nat. Phys. 12 , 594 - 598 ( 2016 ). doi: 10.1038/nphys3645 http://doi.org/10.1038/nphys3645 Unexpectedly large charge radii of neutron-rich calcium isotopes Á. Koszorús , X.F. Yang , W.G. Jiang et al. , Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of N = 32 . Nat. Phys. 17 , 439 - 433 ( 2021 ) doi: 10.1038/s41567-020-01136-5 http://doi.org/10.1038/s41567-020-01136-5 Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of N = 32 R.P. de Groote , J. Billowes , C.L. Binnersley et al. , Measurement and microscopic description of odd-even staggering of charge radii of exotic copper isotopes . Nat. Phys. 16 , 620 - 624 ( 2020 ). doi: 10.1038/s41567-020-0868-y http://doi.org/10.1038/s41567-020-0868-y Measurement and microscopic description of odd-even staggering of charge radii of exotic copper isotopes S.W. Bai , Á. Koszorús , B.S. Hu et al. , Electromagnetic moments of scandium isotopes and N = 28 isotones in the distinctive 0 f 7/2 orbit . Phys. Lett. B 829 , 137064 ( 2022 ). doi: 10.1016/j.physletb.2022.137064 http://doi.org/10.1016/j.physletb.2022.137064 Electromagnetic moments of scandium isotopes and N= 28 isotones in the distinctive 0f7/2 orbit S. Malbrunot-Ettenauer , S. Kaufmann , S. Bacca et al. , Nuclear charge radii of the nickel isotopes 58-68,70 Ni . Phys. Rev. Lett 128 , 022502 ( 2022 ). doi: 10.1103/PhysRevLett.128.022502 http://doi.org/10.1103/PhysRevLett.128.022502 Nuclear charge radii of the nickel isotopes 58-68,70Ni P. Campbell , I.D. Moore , M.R. Pearson , Laser spectroscopy for nuclear structure physics . Prog. Part. Nucl. Phys. 86 , 127 ( 2016 ). https://www.sciencedirect.com/science/article/pii/S014664101500091510.1016/j.ppnp.2015.09.003 https://www.sciencedirect.com/science/article/pii/S014664101500091510.1016/j.ppnp.2015.09.003 Laser spectroscopy for nuclear structure physics X.F. Yang , S.J. Wang , S.G. Wilkins et al. , Laser spectroscopy for the study of exotic nuclei . Prog. Part. Nucl. Phys. 129 , 104005 ( 2023 ). doi: 10.1016/j.ppnp.2022.104005 http://doi.org/10.1016/j.ppnp.2022.104005 Laser spectroscopy for the study of exotic nuclei R. Neugart , J. Billowes , M.L. Bissell et al. , Collinear laser spectroscopy at ISOLDE: new methods and highlights . J. Phys. G Nucl. Part. Phys. 44 , 064002 ( 2017 ). doi: 10.1088/1361-6471/aa6642 http://doi.org/10.1088/1361-6471/aa6642 Collinear laser spectroscopy at ISOLDE: new methods and highlights R.P. de Groote , A. de Roubin , P. Campbell et al. , Upgrades to the collinear laser spectroscopy experiment at the IGISOL . Nucl. Instrum. Methods Phys. Res. Sect. B 463 , 437 - 440 ( 2020 ). doi: 10.1016/j.nimb.2019.04.028 http://doi.org/10.1016/j.nimb.2019.04.028 Upgrades to the collinear laser spectroscopy experiment at the IGISOL A. Voss , T.J. Procter , O. Shelbaya et al. , The collinear fast beam laser spectroscopy (CFBS) experiment at TRIUMF . Nucl. Instrum. Methods Phys. Res., Sect. A 811 , 57 ( 2016 ). https://www.sciencedirect.com/science/article/pii/S016890021501564810.1016/j.nima.2015.11.145 https://www.sciencedirect.com/science/article/pii/S016890021501564810.1016/j.nima.2015.11.145 The collinear fast beam laser spectroscopy (CFBS) experiment at TRIUMF K. Minamisono , P.F. Mantica , A. Klose et al. , Commissioning of the collinear laser spectroscopy system in the BECOLA facility at NSCL . Nucl. Instrum. Methods Phys. Res., Sect. A 709 , 85 ( 2013 ). https://www.sciencedirect.com/science/article/pii/S016890021300103410.1016/j.nima.2013.01.038 https://www.sciencedirect.com/science/article/pii/S016890021300103410.1016/j.nima.2013.01.038 Commissioning of the collinear laser spectroscopy system in the BECOLA facility at NSCL D.T. Yordanov , D. Atanasov , M.L. Bissell et al. , Instrumentation for high-resolution laser spectroscopy at the ALTO radioactive-beam facility . J. Instrum. 15 , P06004 - P06004 ( 2020 ). doi: 10.1088/1748-0221/15/06/p06004 http://doi.org/10.1088/1748-0221/15/06/p06004 Instrumentation for high-resolution laser spectroscopy at the ALTO radioactive-beam facility K. König , J. Krämer , C. Geppert et al. , A new Collinear Apparatus for Laser Spectroscopy and Applied Science (COALA) . Rev. Sci. Instrum. 91 , 081301 ( 2020 ). doi: 10.1063/5.0010903 http://doi.org/10.1063/5.0010903 A new Collinear Apparatus for Laser Spectroscopy and Applied Science (COALA) A.R. Vernon , R.P. de Groote , J. Billowes et al. , Optimising the Collinear Resonance Ionisation Spectroscopy (CRIS) experiment at CERN-ISOLDE . Nucl. Instrum. Methods Phys. Res., Sect. B 463 , 384 - 389 ( 2020 ). doi: 10.1016/j.nimb.2019.04.049 http://doi.org/10.1016/j.nimb.2019.04.049 Optimising the Collinear Resonance Ionisation Spectroscopy (CRIS) experiment at CERN-ISOLDE S.W. Bai , X.F. Yang , S.J. Wang et al. , Commissioning of a high-resolution collinear laser spectroscopy apparatus with a laser ablation ion source . Nucl. Sci. Tech. 33 , 9 ( 2022 ). doi: 10.1007/s41365-022-00992-5 http://doi.org/10.1007/s41365-022-00992-5 Commissioning of a high-resolution collinear laser spectroscopy apparatus with a laser ablation ion source S.J. Wang , X.F. Yang , S.W. Bai et al. , Construction and commissioning of the collinear laser spectroscopy system at BRIF . Nucl. Instrum. Methods Phys. Res., Sect. A 1032 , 166622 ( 2022 ). doi: 10.1016/j.nima.2022.166622 http://doi.org/10.1016/j.nima.2022.166622 Construction and commissioning of the collinear laser spectroscopy system at BRIF W. Nan , B. Guo , C.J. Lin et al. , First proof-of-principle experiment with the post-accelerated isotope separator on-line beam at BRIF: measurement of the angular distribution of 23 Na + 40 Ca elastic scattering . Nucl. Sci. Tech. 32 , 53 ( 2021 ). doi: 10.1007/s41365-021-00889-9 http://doi.org/10.1007/s41365-021-00889-9 First proof-of-principle experiment with the post-accelerated isotope separator on-line beam at BRIF: measurement of the angular distribution of 23Na + 40Ca elastic scattering Y. Yang , L.T. Sun , Y.H. Zhai et al. , Heavy ion accelerator facility front end design and commissioning . Phys. Rev. Accel. Beams. 22 , 110101 ( 2019 ). doi: 10.1103/PhysRevAccelBeams.22.110101 http://doi.org/10.1103/PhysRevAccelBeams.22.110101 Heavy ion accelerator facility front end design and commissioning G.R. Stachler , Introduction to nuclear reactions . ( Springer , London , 2019 ). doi: 10.1007/978-1-349-20531-8 http://doi.org/10.1007/978-1-349-20531-8 Introduction to nuclear reactions P. Zhang , Y.S. Liu , S.W. Bai et al. , Progress in the development of a collinear laser spectroscopy setup for the study of unstable nuclei . Chin. Sci. Bull. ( 2022 ). doi: 10.1360/TB-2022-1116 http://doi.org/10.1360/TB-2022-1116 Progress in the development of a collinear laser spectroscopy setup for the study of unstable nuclei All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Yong-Chao Liu, Xiao-Fei Yang, Shi-Wei Bai, Shu-Jing Wang, Peng Zhang, Yin-Shen Liu, Han-Rui Hu, Yang-Fan Guo, Zhou Yan, Ze-Yu Du, Wen-Cong Mei, Zhe-Yang Lin, Hong-Wei Li, Yan-Lin Ye, Qi-Te Li and Chuang-Ye He. The first draft of the manuscript was written by Yong-Chao Liu and Xiao-Fei Yang and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. 10.1007/s41365-023-01197-0 This work was supported by the National Natural Science Foundation of China (Nos. 12027809, U1967201, 11875073, 11875074 and 11961141003), National Key R&D Program of China (No. 2018YFA0404403), and the State Key Laboratory of Nuclear Physics and Technology, Peking University (Nos. NPT2019ZZ02, NPT2020KFY17). 2023-01-05 2023-01-30 2023-02-14 2023-03-23 2023-04-20 © China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, ChineseNuclear Society and Springer Nature Singapore Pte Ltd. 2023 This is a post-peer-review, pre-copyedit version of an article published in Nuclear Science and Techniques. The final authenticated version is available online at: http://dx.doi.org/10.1007/s41365-023-01197-0 http://dx.doi.org/10.1007/s41365-023-01197-0 . Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law. 2023 The data that support the findings of this study are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.07659 and https://cstr.cn/31253.11.sciencedb.07659. Data availability Nuclear Science and Techniques 3 34