Ion Research Facility In Lanzhou Research Articles

Design of multi-channel electronic prototype for 101Sn energy level lifetime measurement

In this study, a 32-channel front-end data acquisition unit (DAQU) with high temporal resolution and count rate was developed at the Heavy Ion Research Facility in Lanzhou (HIRFL), China, to measure the lifetime of 101Sn on the Spectrometer for Heavy Atoms and Nuclear Structure. The DAQU data analysis module uses a field programmable gate array (FPGA) to implement and time stamp extraction through an FPGA-based tapped delay line (TDL) time-to-digital converter. The energy measurements were implemented using a trapezoidal algorithm and a sliding baseline averaging method. The DAQU was tested and calibrated using a pulse generator and cosmic rays. The results show that the system had a dead time of less than 500 ns, a dynamic range of “0” to “500” mV, and an energy resolution of better than 4.8‰ (full width at the half-maximum, FWHM). In addition, the single-channel temporal resolution under multi-channel settings surpasses 111.2 ps (FWHM), satisfying the experiment's requirements for the electronics system.

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

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.

Design and performance testing of a T0 detector for the CSR External-target Experiment

The Cooling Storage Ring External-target Experiment at the Heavy Ion Research Facility in Lanzhou, China, is a multi-purpose nuclear physics experimental device to operate in the Giga electron-volt (GeV) energy range. The time-of-flight (TOF) system is critical for identifying charged particles in the GeV energy range. In the Experiment spectrometer, the TOF system consists of three parts: T0, internal TOF, and external TOF. The T0 detector provides a high-precision start time for the TOF system by measuring the crossing time of the heavy ion beam. This study details the design, performance simulation, and performance testing of the T0 detector. The simulation results and heavy-ion beam test show that the T0 detector prototype has an excellent time resolution, which is better than 30 ps, and fulfills the requirements of the CEE.

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.

Design of a Modular High-Accuracy, High-Voltage Charging Power Supply Prototype

In order to realize the upgrade of the Kicker system for the Heavy Ion Research Facility in Lanzhou, the design of a modular high-accuracy, high-voltage charging power supply based on a full-bridge LC series resonant topology was proposed. More specifically, the parametric design of one of the modules, including the main circuit and transformer design, was introduced, and the realization principle of high precision was proposed. After simulation verification, a 35 kW/80 kV charging power supply prototype was developed. The experimental result shows that the power supply’s output voltage can be adjusted between 0~80 kV, and the output accuracy is better than 1‰.

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.

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.

Investigation of negative-parity states in 16C via deuteron inelastic scattering * *Supported by the National Key R & D Program of China (2018YFA0404403), the National Natural Science Foundation of China (11775004, U1867214, 11875074, 11961141003), the funding from the State Key Laboratory of Nuclear Physics and Technology, Peking University (NPT2021ZZ01), and the funding from Heavy Ion Research Facility in Lanzhou (HIR2021PY002)

Two low-lying unbound states in 16C are investigated by deuteron inelastic scattering in inverse kinematics. Besides the 2 state at 5.45 MeV previously measured in a 1n knockout reaction, a new resonant state at 6.89 MeV is observed for the first time. The inelastic scattering angular distributions of these two states are well reproduced by the distorted-wave Born approximation (DWBA) calculation with an l = 1 excitation. In addition, the spin-parities of the unbound states are discussed and tentatively assigned based on shell model calculations using the modified YSOX interaction.

Experimental and Simulation Study on Shielding Performance of Developed Hydrogenous Composites

Space radiation has been well-known as the main health hazard to crews involved in manned space explorations. Two kinds of hydrogenous-rich composites are developed through compressing molding under high-temperature processing techniques for shielding space radiation. Beams of 80~400 MeV/n 12 C of the Heavy Ion Research Facility in Lanzhou are used to test the shielding properties of the new composites. Experimental results show that the composite with more hydrogen content has higher shielding ability for 80 and 400 MeV/n 12 C particles. Meanwhile, the addition of boron has no obvious effect on improving the shielding performance of the composite. Monte Carlo radiation transport codes were used to assess the shielding performance of composite in real space radiation. The simulation results show that hydrogenous-rich composite has significant advantage in space radiation shielding compared with traditional aluminum.

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.

An improved method of bunch-by-bunch beam position calculation in a heavy-ion synchrotron

The beam position monitor (BPM) system is a key element of the orbit correction system of a heavy-ion synchrotron. The bunch-by-bunch beam position calculation algorithm is one of the important parts of the BPM system, which determines the processing speed, accuracy and resolution of the beam position measurement. In this paper, a total least squares (TLS) algorithm based on an Exponentially Weighted Moving Average (EWMA) filter called EWMA TLS method is proposed, which applies to evaluate the beam position. A numerically simulated BPM signal, the signal from a test bench, as well as the real beam signal tested at the main Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou (HIRFL-CSRm) are analyzed using the new approach. The results demonstrate an improved accuracy of the position calculation of the bunches, and the method is much more robust against noise than previous methods, especially under the condition of a low signal-to-noise ratio (SNR), e.g. due to low beam intensities.

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.

&amp;beta;-decay and isospin symmetry breaking

<p indent=0mm>The elegant concept of isospin symmetry is of fundamental importance in nuclear and elementary particle physics. As a β-decay process changes an up quark to a down quark or <italic>vice versa</italic>, studies of nuclei with exchanged numbers of neutrons and protons, known as mirror nuclei, can be a powerful means to probe isospin symmetry breaking. A series of β-decay experiments of sd-shell nuclei near the proton drip line produced by projectile fragmentation were performed at the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou (HIRFL-RIBLL1) using a silicon array with a high detection efficiency and a low detection threshold. The secondary ions were identified by the combination of Δ<italic>E</italic>-TOF and magnetic rigidity (<italic>Bρ</italic>) in which the time of flight (TOF) was measured by two plastic scintillators at the second and fourth focal planes of the RIBLL1 and the energy loss (Δ<italic>E</italic>) was measured by two silicon detectors in the front of the silicon array. Double-sided silicon strip detectors (DSSDs) in the center of the array served to measure the residual energies of secondary ions on an event-by-event basis and study their decay properties with an implantation-decay correlation. Several quadrant silicon detectors (QSDs) placed behind DSSDs were used for anticoincidences of the penetrating fragments and light particles coming along with the beam, and measurements of β particles and high-energy protons. The β-delayed proton peaks with known energies and their corresponding absolute intensities were used for the energy and detection efficiency calibrations of the DSSDs. The system allows us to measure protons with energies down to about <sc>200 keV</sc> without obvious β background in the proton spectrum and was successful to measure the energies, time, and positions of implanted ions and decay protons efficiently, supporting researchers to study the decay properties of nuclei towards the proton drip line. The β-decay data, together with the large-scale shell-model calculations, allows detailed investigations on the mirror-nuclei systems resulting in the systematic study of isospin symmetry breaking in the sd-shell nuclear region. It was found that the mirror asymmetry parameters become larger due to the smaller separation energies while approaching the proton drip line for the extremely proton-rich sulfur nuclei ^27,28,29S and the Coulomb forces and other isospin-symmetry nonconserving forces acting between protons would lead to extended proton wave functions and cause mirror asymmetries. The properties of ²²Si β-decay for the transitions to the low-lying states of ²²Al were measured, and the reduced transition probabilities were determined. Comparing with the data on the β-decay of the mirror nucleus ²²O, we found a mirror asymmetry of <italic>δ</italic>=209(96)% in the transition to the first 1⁺ excited state of the respective daughters. This is by far the largest value of <italic>δ</italic> observed in the low-lying states. Shell-model calculations with isospin-nonconserving forces, including the <italic>T</italic>=1,<italic> J</italic>=2, 3 interactions related to the s_1/2 orbit that introduces explicitly the isospin-symmetry breaking force and describes the loosely bound nature of the wave functions of the s_1/2 orbit, can reproduce the observed data well and demonstrate that this dramatically large mirror asymmetry is attributed to the significant proton occupation and loosely bound nature of the wave functions of the s_1/2 orbit, which suggests that ²²Al is a proton-halo nucleus.