Heavy Ion Research Facility In Lanzhou Research Articles

A miniature prototype of Time Projection Chambers for CSR External-Target Experiment

A miniature prototype of time projection chamber for the cooling storage ring external-target experiment (CEE) at the Heavy Ion Research Facility in Lanzhou (HIRFL) was designed for three-dimensional tracking of charged particles produced in heavy-ion collisions at the target region and for particle identification. The prototype consists of a TPC detector chamber with active volume of 9 cm (height), 10 cm (length) and 10 cm (width), gas electron multiplier (GEM) detector readout and SAMPA-based electronics. This work describes design, track reconstruction method and performance of the prototype. The energy resolution is 11.03% sigma using a 55Fe x-ray source. Using heavy-ion beam of 150 MeV/u Fe, the test results show that the two-dimensional position resolution and drift time resolution of the prototype are better than 400 μm and 20 ns, respectively.

Exploration of the ground state properties of neutron-rich sodium isotopes using the deformed relativistic mean field theory in complex momentumrepresentations with BCS pairings* *Partly supported by the National Natural Science Foundation of China (11935001, 11575001), the Natural Science Foundation of Anhui Province (2008085MA26), Anhui project (Z010118169), the Heavy Ion Research Facility in Lanzhou (HIRFL) (HIR2021PY007), and the project of Key Laboratory of High Precision Nuclear Spectroscopy conducted in Chinese Academy of Sciences

This study explores the ground-state characteristics of neutron-rich sodium isotopes, encompassing two-neutron separation energies, root-mean-square radii, quadrupole moments of proton and neutron distributions, single-particle levels of bound and resonant states, and neutron density distributions and shapes. Simultaneously, special attention is paid to the distinctive physical phenomena associated with these isotopes. The deformed relativistic mean field theory in complex momentum representations with BCS pairings (DRMF-CMR-BCS) employed in our research provides resonant states with real physics, offering insights into deformed halo nuclei. Four effective interactions (NL3, NL3*, PK1, and NLSH) were considered to assess the influence of continuum and deformation effects on halo structures. Calculations for odd-even nuclei 35–43Na revealed the dependence on the chosen effective interaction and number of considered resonant states. Neutron occupation patterns near the Fermi surface, particularly in orbitals and , were determined to be crucial in halo formation. The study provided detailed insights into the density distributions, shape evolution, and structure of neutron-rich sodium isotopes, contributing valuably to the field of nuclear physics.

Beam test result of the sealed MRPC prototype for CEE-eTOF

We report the beam test and result of the sealed Multigap Resistive Plate Chambers (MRPC) for the external Time of Flight (eTOF) wall of the Cooler-strorage-ring External-target Experiment (CEE). The test stand detects the secondary charged particles produced from heavy ion collisions in the Heavy Ion Research Facility in Lanzhou (HIRFL), and it serves as a joint evaluation of the future CEE system, including the detectors, readout electronics, data acquisition, trigger system, etc. The collision is achieved by a Fe beam and a Fe target, with an estimated beam energy of 300 MeV/u. The sealed MRPC prototypes work stably during the test with a 20 sccm low gas flow. The whole test system is triggered from the channel multiplicity provided by the TOF detectors. A tracking method is implemented to the analysis in order to resolve the events with multiple tracks on the detectors. The result shows that the detectors reach 98% efficiency at their working point. With proper corrections, the time resolution is evaluated to be 60 ps, which fulfills the requirement to the eTOF wall.

Development of a gating grid driver of TPC for exotic beam experiments

The Multi-purpose Time Projection Chamber (TPC) for nuclear AsTrophysical and Exotic beam experiments (MATE) is being upgraded for the decay and active target experiments at the Heavy Ion Research Facility in Lanzhou (HIRFL). We have developed a gating grid driver to control the transitions between the closed and open states of the gating grid of the MATE-TPC to detect interesting rare decay events from a large amount of implanted ions. The gating grid driver is mainly composed of a digital control unit and a high-voltage switch unit. The digital control unit responds to the external trigger and generates control signals for the operation of the high-voltage control part based on the presetting instruction. The high-voltage switch unit is connected to two negative high voltages with different values and changes the voltages of neighboring wires of the gating grid based on the request for closing or opening the gate. A 500 ns switching time of the gating grid driver has been achieved from the closed to open state. The duration of the open state can be adjusted from 1 µs to 99 ms based on the experimental requirements. This gating grid driver can be used in a particle detector with a high voltage bias of up to ± 3000 V.

A Full-Waveform Digitizer for the Readout of Plastic Scintillator Detectors at HIRFL and HIAF

Being among the world’s leading heavy-ion scientific facilities, the heavy ion research facility in Lanzhou (HIRFL) and the high-intensity heavy-ion accelerator facility (HIAF) are constructed to study nuclear physics, atomic physics, nuclide chart, and heavy-ion related applications. Plastic scintillator detectors (PSD) are highly desirable and are used in large amounts for performing the experiments at HIRFL and HIAF. The PSDs are coupled with a photomultiplier tube (PMT) or silicon photomultiplier (SiPM) for converting the photons into electric signals. In this work, we develop a 16-channel full waveform digitizer (FWD) as a standard readout unit for the PSDs at HIRFL and HIAF. The FWD is based on two DRS4 chips. The design of these chips is based on the principle of a switched capacitor array (SCA), which can sample the analog signals at the GHz scale with low power consumption. In addition, the proposed FWD is designed with a general-purpose technique to reduce the development time, production cost, and maintenance difficulties. The laboratory test results show that the proposed FWD is relatively less nonlinear, i.e., about 0.6%. Its time precision is better than 15 ps. The cascade of multiple channels successfully realizes a sampling depth of 2048 cells. The joint test results of PSD show that an excellent performance in terms of measuring the cosmic rays is achieved. This paper presents the design and performance of the proposed FWD.

Design of an SHA-Less Pipeline ADC With Op-Amp Sharing Techniques for MAPS

As the leading research platform of heavy-ion science in China, the heavy-ion physics and applications at the Heavy Ion Research Facility in Lanzhou (HIRFL) and the High-Intensity heavy-ion Accelerator Facility (HIAF) drive the development of new detector technology. A monolithic active pixel sensor (MAPS) has been designed in a 130-nm CMOS process for HIRLF and HIAF. This MAPS can measure the energy deposition and position of the particle hit. As the critical component of this MAPS, a regional 12-bit 40-Msps pipeline ADC has been designed to convert the analog signals from the pixels into digital data. Due to the strict limitation on power and area, this ADC adopts the SHA-less architecture and stepwise capacitance reduction. Also, the op-amp sharing technology is used in the 1.5-bit stages. This ADC has a power consumption of 60 mW and occupies <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$874\times 550\,\,\mu \text{m}$ </tex-math></inline-formula> . Simulation results indicate that it achieves an ENOB of 11.77 bits and a SINAD of 72.57 dB at the tt corner with an input frequency of 3.291 MHz. The figure of merits (FOM) value is 507 fJ/step.

Accurate Low Current Measurement Electronics With Self-Calibration Function for Ionization Chamber of Slow Extraction in HIAF

The new wide-range readout electronics with a self-calibration function are designed for ionization chambers (ICs) in the slow extraction of high-intensity heavy-ion accelerator facility (HIAF), booster ring (BRing). These electronics consist of a programmable trans-impedance amplifier (TIA), a self-calibration circuit, an 18-bit analog-to-digital converter (ADC), and a ZYNQ-7015 field-programmable gate array (FPGA). It is capable of monitoring weak current signals of 40 pA–4 mA with a sampling rate of 5 MHz. The ZYNQ-7015 FPGA manages the operation mode of the analog front-end (AFE) and the gain of the TIA. It also performs digital signal processing algorithms and data communication with the host computer. The self-calibration circuit uses a combination of a Schmitt trigger and voltage-to-current (V–I) converters to generate two square wave current signals with different peaks ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \mu \text{A}$ </tex-math></inline-formula> and 2 mA). During offline tests, the effective number of bits (ENOB) is 12.98 bits, and the nonlinearity is less than 0.075% for a full scale. Finally, the readout electronics are deployed for ICs’ slow extraction measurements at the extraction line of the cooling storage ring of the heavy-ion research facility in Lanzhou (HIRFL). With the help of a commercial dc-transformer in the cooling storage ring project of heavy ion research facility in Lanzhou (HIRFL-CSR), these electronics not only execute an accurate current measurement, but also can monitor the extraction efficiency reliably. In a word, these electronics play an important role in the fields of extremely weak and high dynamic current signal measurements.

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.

&lt;i&gt;In situ&lt;/i&gt; study of light emission from SiO&lt;sub&gt;2&lt;/sub&gt; irradiated by 645 MeV Xe&lt;sup&gt;35+&lt;/sup&gt; ions

Silicon dioxide (SiO&lt;sub&gt;2&lt;/sub&gt;) is an important component of nuclear reactor optical fiber and is also a candidate material for wast solidification. Owing to its special physical and chemical characteristics, it is used in many different technology fields like optics, electronics, energy orspace. Swift heavy ion irradiation can modify the crystal structure and optical property of optical material SiO&lt;sub&gt;2&lt;/sub&gt;. Swift heavy ions deposit their energy mainly by inelastic interaction. Highly ionized lattice atoms may be formed along the trajectory, and a fraction of their electrical energy can be converted directly into the kinetic energy of the ions. The irradiation experiment is performed with Xe&lt;sup&gt;q+&lt;/sup&gt; ions at the irradiation terminal of the sector-focused cyclotron at heavy-ion research facility in Lanzhou (HIRFL). The on-line spectral measurement experiment is carried out during irradiation. In the darkroom, the UV-visible light emission from the target is focused into optical fiber by a collimating lens, and then is analyzed with the Sp-2558 spectrometer equipped with a 1200 g/mm optical grating blazed at 500 nm. In the present work, SiO&lt;sub&gt;2&lt;/sub&gt; single crystals are irradiated with 93–609 MeV Xe&lt;sup&gt;q+&lt;/sup&gt; ions with a dose in a range of 1×10&lt;sup&gt;11&lt;/sup&gt;–3×10&lt;sup&gt;11&lt;/sup&gt; ions/cm&lt;sup&gt;2&lt;/sup&gt;. During irradiation, the emission spectra, in a range of 200–800 nm, from SiO&lt;sub&gt;2&lt;/sub&gt; irradiated by 93, 245, 425 and 609 MeV Xe&lt;sup&gt;q+&lt;/sup&gt; ions, are obtained. Two emission bands centered at 461 and 631 nm are observed. These emission bands are produced by Frenkel exciton radiation de-excitation and their intensities are closely related to the irradiated ion energy and radiation dose. The results show that the light intensity increases with the electron energy loss index increasing. And owing to crystal damage caused by ion irradiation, the intensity of emission spectrum decreases with the augment of irradiation dose. Ion loses its energy throughout the ion track via Sn and Se interacting with target atoms and electrons respectively, and the energy lost by the ion is estimated by using SRIM code. The SRIM simulated ion ranges and recoil atom distribution, target ionization (energy loss to target electrons), damage production in SiO&lt;sub&gt;2&lt;/sub&gt; are presented. Based on the energy deposition process, the emission bands related to the crystal structure itself are discussed. It indicates that electron energy loss plays a leading role in the process of light emission. In-situ measurement of the optical emission is of great significance in studying the irradiation modification and can help to understand the process of crystal damage caused by ion irradiation.

Beam position measurement system at HIRFL-CSRm

Beam position measurement system can not only provide the beam position monitoring, but also be used for global orbit correction to reduce beam loss risk and maximize acceptance. The Beam Position Monitors (BPM) are installed along the synchrotron to acquire beam position with the front-end electronics and data acquisition system (DAQ). To realize high precision orbit measurement in the main heavy ion synchrotron and cooling storage ring of heavy-ion research facility in Lanzhou (HIRFL-CSRm), a series of alignment and calibration work has been implemented on the BPM and its DAQ system. This paper analyzed the tests performed in the laboratory as well as with beam based on the developed algorithms and hardware. Several filtering algorithms were designed and implemented on the acquired BPM raw data, then the beam position and resolution were calculated and analyzed. The results show that the position precision was significantly improved from more than 100 μm to about 50 μm by implementing the new designed filtering algorithm. According to the analyzation of the measurement results and upcoming physical requirements, further upgrade scheme for the BPM DAQ system of CSRm based on field programmable gate array (FPGA) technology was proposed and discussed.

High-voltage detuning power system of HIRFL-CSRm electron cooler for Dielectronic-Recombination experiments

Dielectronic-Recombination (DR) experiments of highly charged ions are performed in the main Cooler Storage Ring (CSRm) at Heavy Ion Research Facility in Lanzhou (HIRFL) accelerator complex. A new detuning power system of the electron cooler is developed to modulate the electron velocity from the cooling velocity and thus control the collision energy in the experiment. In this paper, the design and commissioning of the detuning power system are reported. The detuning power supply adopts the scheme of HVDC (high-voltage DC) and HVA (high-voltage amplifier) connected in series. A FPGA digital controller combined with a high-precision ADC/DAC board is used for multiple-linear voltage settings and feedback. The output maximum DC voltage is −5 kV and the detuning voltage is in the range of 0 to ±1 kV. The main features are the good output voltage stability of 10 ppm and the rapid voltage changing of 10 V/μs. The decoupling and protection of the detuning power supply under the high detuning pulse current are described as well. Finally, a DR spectrum of Ar15+ ions measured with the new detuning power system is presented. The experimental result shows a good resolution, verifying the reliability and feasibility of the design.

Readout Electronics of the Prototype Beam Monitor in the HIRFL-CSR External-Target Experiment

The External-target Experiment (CEE) at the Cooling Storage Ring of the Heavy-Ion Research Facility in Lanzhou (HIRFL-CSR) will be the first large-scale experiment in nuclear physics independently developed in China covering the GeV energy regime. The beam monitor located at the center front of the CEE accurately measures the position of the particles with a few tens of um accuracy in a non-interceptive way. This unique advantage significantly improves the accuracy of the particle track reconstructions. This beam monitor’s readout electronics consist of the Front-end module (FEM), Readout Control Module (RCM), and Clock Synchronization module (CSM). Twhe novel Topmetal series pixel sensors directly collect the ionized charge along the track of the ion beam while it passes through the gas in the beam monitor. Lab test proves that the readout electronics have an INL of less than 1%. In addition, the prototype beam monitor can measure the position of the 40Ar beam of 320 MeV/u with a resolution of ~6.9 μm. This paper will discuss the design, characterization, and test of the readout electronics.

Isotopic production cross sections of fragmentation residues produced by 18O ions on a carbon target near 260 MeV/nucleon* *Supported in part by the National Natural Science Foundation of China (11905260, 12005314), the Western Light Project of Chinese Academy of Sciences, the Heavy Ion Research Facility in Lanzhou (HIRFL), and the open research project of CAS large research infrastructures

The isotopic cross sections of residual nuclei produced in fragmentation reactions of 18O projectiles impinging on a carbon target at energies near 260 MeV/nucleon were measured at the HIRFL facility in Lanzhou (China). A full identification of atomic and mass numbers of fragments was achieved from the determination of their magnetic rigidity, energy loss, and time of flight. The production cross sections for a dozen of nitrogen, carbon, and boron isotopes were determined with uncertainties below 30% for most of the cases. The obtained cross sections for N and B isotopes show a rather good agreement with previous experimental data obtained with different projectile energies. The cross sections for some C isotopes seem to exhibit a dependence on the projectile energy. A comparison of the data and several theoretical model calculations are presented.

Elastic scattering investigation of radioactive B13 and O13 projectiles on a Pb208 target at intermediate energies

Elastic scattering measurements were performed for the proton drip-line nucleus $^{13}\mathrm{O}$ (with ${S}_{p}=1.512$ MeV) and its partner mirror nucleus $^{13}\mathrm{B}$ (with ${S}_{n}=4.878$ MeV) projectiles on a $^{208}\mathrm{Pb}$ target at intermediate energies, namely ${E}_{\mathrm{lab}}=413$ and 254 MeV, respectively. These secondary radioactive ion beams were produced at the Radioactive Ion Beam Line in Lanzhou (RIBLL), Heavy-Ion Research Facility in Lanzhou (HIRFL). The elastic scattering angular distributions for these projectiles show a typical Fresnel diffraction peak at forward angles. Optical model analyses of the angular distributions, using double-folding and global potentials, were performed and different densities for these projectiles were probed.

β-Delayed γ Emissions of 26P and Its Mirror Asymmetry

The study of the origin of asymmetries in mirror β decay is extremely important to understand the fundamental nuclear force and the nuclear structure. The experiment was performed at the National Laboratory of Heavy Ion Research Facility in Lanzhou (HIRFL) to measure the β-delayed γ rays of 26P by silicon array and Clover-type high-purity Germanium (HPGe) detectors. Combining with results from the β decay of 26P and its mirror nucleus 26Na, the mirror asymmetry parameter δ ( ≡ft+/ft−− 1) was determined to be 46(13)% for the transition feeding the first excited state in the daughter nucleus. Our independent results support the conclusion that the large mirror asymmetry is close to the proton halo structure in 26P.

Fragmentation of stable and neutron-rich 12-16C into boron fragments at approximately 240 MeV/nucleon * *Supported by the National Natural Science Foundation of China (U1732134, U1832205), the Heavy Ion Research Facility in Lanzhou (HIRFL), and the open research project of CAS large research infrastructures

The elemental fragmentation cross sections of boron fragments produced by stable and neutron-rich 12-16C beams with a carbon target were systematically measured at an incident beam energy of approximately 240 MeV/nucleon. The measured cross sections were found to increase as the projectile mass number increases. The observed feature is explained qualitatively based on the abrasion-ablation two-stage reaction model and is compared quantitatively with predictions from various reaction models, including empirical and statistical models. All models agree with the measured cross sections within a factor of 2.

Influence of different fields of mesons on the pseudospin symmetry in single-neutron resonant states * *Supported by the National Natural Science Foundation of China (11935001, 11805004), the Key Research Foundation of Education Ministry of Anhui Province (KJ2018A0028), the Natural Science Foundation of Anhui Province (2008085MA26) and Heavy Ion Research Facility in Lanzhou (HIRFL)

In the framework of the relativistic mean field theory combined with the complex momentum representation method, we elucidate the pseudospin symmetry in the single-neutron resonant states and its dependence on the , , and meson fields. Compared with the effect of the field, the and fields provide the main contributions to the pseudospin energy and width splitting of the resonant pseudospin doublets. Especially, we compare quantitatively the pseudospin wave functions' splittings in resonant doublets, and investigate their dependencies on different fields of mesons, which is consistent with that of energy and width splittings. Current research is helpful to understand the mechanism and properties of pseudospin symmetry for resonant states.

Readout Electronics Prototype of TOF Detectors in CEE of HIRFL

In the Cooling storage ring External-target Experiment (CEE) in heavy ion research facility in Lanzhou (HIRFL), multigap resistive plate chambers (MRPCs) detectors are used for high-precision time-of-flight (TOF) measurement to identify the scattered particles after the ion beam hits the target. Regarding the external TOF (eTOF) and 2/3 internal TOF (iTOF) detectors, a ~25-ps rms time precision is required for the readout electronics, whereas for the other 1/3 iTOF detectors, a ~10-ps rms precision is required. A readout electronics prototype was designed, including the front-end electronics (FEE) based on analog signal amplification, discrimination, and the time-to-digital module (TDM), based on field-programmable gate array (FPGA) time-to-digital converter (TDC), to achieve high-precision time measurement. PreAmplifier-DIscriminator (PADI) is used in the design of the FEE, while an FPGA TDC, based on tapped delay line (TDL) structure, with a time precision performance better than 5-ps rms, is implemented in the TDM, as well as the trigger matching circuit and other control logic. The performance of the whole system was tested under different input signal charges and the results indicated that the time precision is better than 10-ps rms, which satisfies the application requirements.

Microstructure evolution of T91 steel after heavy ion irradiation at 550 °C* *Project supported by Guangdong Major Project of Basic and Applied Basic Research (Grant No. 2019B030302011), the National Natural Science Foundation of China (Grant Nos. U2032143, 11902370, and 52005523), the International Science and Technology Cooperation Program of Guangdong Province, China (Grant No. 2019A050510022), the China Postdoctoral Science Foundation (Grant Nos. 2019M653173 and 2019TQ0374), and the Heavy Ion Research Facility of Lanzhou (HIRFL).

Fe-Cr ferritic/martensitic (F/M) steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies. In this study, a widely-used ferritic/martensitic steel, T91 steel, was irradiated by 196-MeV Kr+ ions at 550 °C. To reveal the irradiation mechanism, the microstructure evolution of irradiated T91 steel was studied in details by transmission electron microscope (TEM). With increasing dose, the defects gradually changed from black dots to dislocation loops, and further to form dislocation walls near grain boundaries due to the production of a large number of dislocations. When many dislocation loops of primary a 0/2〈 111 〉 type with high migration interacted with other defects or carbon atoms, it led to the production of dislocation segments and other dislocation loops of a 0 〈 100 〉 type. Lots of defects accumulated near grain boundaries in the irradiated area, especially in the high-dose area. The grain boundaries of martensite laths acted as important sinks of irradiation defects in T91. Elevated temperature facilitated the migration of defects, leading to the accumulation of defects near the grain boundaries of martensite laths.

Introduction of the Heavy Ion Research Facility in Lanzhou (HIRFL)

The Heavy Ion Research Facility in Lanzhou (HIRFL) is a multi-disciplinary research facility that provides heavy ion beams for physical, biomedical and material sciences. It is a major academic facility of China and one of the world's important centers in nuclear physics and accelerators. The facility was built step by step at Institute of Modern Physics (IMP) over a half century. The first cyclotron was built with great assistance from the former Soviet Union in 1960s, and the newest linear accelerator was tested successfully in 2019. The HIRFL accelerator can provide beams from proton to Uranium with energies of hundreds MeV/u, and hence diverse fundamental sciences and applied researches were carried out at IMP. In this paper, an introduction of the HIRFL accelerator complex was presented. Details of the HIRFL components including ion sources, cyclotrons, synchrotrons, linac and experimental terminals were described. The current operation status and upgrade plans were reported.