Inverse-kinematics charge-exchange experiments with radioactive ion beams require compact detector systems with good particle identification capability and high energy resolution for recoil charged particles emitted at large angles. In a recently developed TPC-CsI(Tl) Delta E-E telescope for the inverse-kinematics (He-3, t) reaction, the performance of long CsI(Tl) scintillator bars is limited by light collection non-uniformity (LCNU) caused by scintillation-photon attenuation. In this work, a dual-end readout scheme for CsI(Tl) bars is proposed and investigated. Geant4-based Monte Carlo simulations are performed to study photon transport and collection in single-end and dual-end readout configurations, showing that the LCNU is reduced from 18.19% to 4.30% with improved light-collection efficiency. Experimental tests using cosmic ray muons further confirm the effectiveness of the dual-end readout, achieving LCNU below 6% for most crystals. These results demonstrate that dual-end readout provides a practical and effective solution to mitigate intrinsic non-uniformity in long CsI(Tl) bars and significantly improve the energy resolution and overall performance of CsI(Tl)-based detector systems.

Short-range correlation (SRC) in nuclei refers to nucleons forming temporally correlated pairs in close proximity, giving rise to the high momentum of the nucleons beyond the Fermi surface. It has been reported that bremsstrahlung gamma production from the neutron-proton process in heavy-ion reactions provides a potential probe to the SRC abundance in nuclei. In this paper, we present in detail the precision measurement of bremsstrahlung gamma rays in 124Sn + 124Sn reactions at 25 MeV/nucleon using the Compact Spectrometer for Heavy IoN Experiment (CSHINE). A comprehensive experimental and analysis framework is established to ensure the reliability and robustness of the extracted results. Background contributions are evaluated and subtracted using independent methods, and the consistency of the analysis is systematically validated. By comparing the experimental gamma spectrum with isospin-dependent Boltzmann-Uehling-Uhlenbeck simulations, the high momentum tail (HMT) fraction of RHMT = (20 +/- 3)% is derived in 124Sn nuclei. This work provides a detailed and validated experimental framework for extracting SRC information from bremsstrahlung gamma-ray emission and demonstrates the feasibility of studying nucleon SRCs with high precision in low-energy heavy-ion collisions.

A beam particle monitor (BPM), which is designed to locate the position of each beam particle, is a part of the cooler-storage-ring external-target experiment at the heavy-ion research facility in Lanzhou (HIRFL) of China. A novel front-end application-specific integrated circuit (ASIC) integrating charge sensors and readout circuitry on a single silicon chip is used to sense and read out the charge for the BPM. The ASIC operates within a gaseous ionization detector to detect drifting charges. The area of the ASIC is about 3 X 19 mm. It features 180 channels with a pitch of 100 mu m and an event-driven zero-suppression readout scheme. Each channel is composed of a charge collection electrode (CCE), a charge-sensitive amplifier, a discriminator, an amplitude measurement with the time-over-threshold method, and an arrival-time measurement with the time-to-digital converter method. The CCE is an exposed top-most metal with a size of 1 mm X 89 mu m. Three selectable gain modes are designed in the charge-sensitive amplifier, in order to increase the input dynamic range. The decay time of the charge-sensitive amplifier and the threshold of the discriminator in each channel can be adjusted independently by local digital-to-analog converters, hence reducing the inconsistency between channels. Detailed tests have been performed. The equivalent noise charge (ENC) ranges from 344 to 378 e(-) and the fixed pattern noise is approximately 97 e(-) after the threshold adjustment. The minimum shaping time is about 500 ns. The arrival time resolution is from 9 to 13 ns depending on the drifting distance. The variations of the noise and the threshold during long-term running are less than +/- 1.5% and +/- 0.3%, respectively. The total ionization dose test, laser beam, and heavy-ion beam tests have also been carried out.

The High-Rigidity Radioactive Ion Beam Line (HIRIBL) is a projectile fragmentation-type secondary beam facility that works at relativistic energies. As an important part of the High-Intensity Heavy-Ion Accelerator Facility (HIAF), it is known for its high beam intensity, high energy, and ability to produce complex particles. The beamline uses a TOF-rho-Delta E method to identify secondary beam particles. This process presents major challenges for the dynamic range, counting rate, and long-term stability of the particle identification detectors. To solve these problems, a new Micro-Pin Array Detector (MIPA) has been developed. This detector works over a large dynamic range, from the ionization region to the proportional region. In a gas mixture of Ar and CH4 (10%, known as P10), the MIPA achieved a gain of 4 & times; 104 and operated stably for fifteen days. When set up as a parallel-plate ionization chamber, the MIPA showed energy resolutions of 4.19% for 239Pu, 3.57% for 241Am, and 3.07% for Cm-244, using a triple-alpha source. These results prove that the MIPA Detector has a large dynamic range and very good stability, making it suitable for advanced nuclear detection applications.

Chirality lies at the heart of low-energy QCD, governing the symmetry structure that shapes hadron masses and strong interaction dynamics. Among the most compelling open questions tied to chiral dynamics and spontaneous chiral symmetry breaking is the longstanding Λ polarization puzzle, in which Λ hyperons produced in unpolarized hadronic collisions exhibit a surprisingly large transverse polarization that remains theoretically unexplained. This whitepaper presents the proposal for the Hyperon-Nucleon Spectrometer (H-NS) at the High-Intensity heavy-ion Accelerator Facility (HIAF). Leveraging the high energy and high intensity of HIAF's proton and heavy-ion beams, the H-NS experiment will perform systematic studies of hyperon polarization phenomena and their underlying mechanisms in proton-proton (pp), proton-nucleus (pA), and nucleus-nucleus (AA) collisions in the fixed target mode. A wide-range beam energy scan, including proton beams from 3 GeV up to 9.3 GeV (HIAF) and up to 32 GeV (upgraded HIAF), will be conducted to examine the dependence of polarization on collision energy. The spectrometer is designed with specialized detectors capable of high-precision reconstruction of final-state baryon polarizations. Among its many interesting and important measurements, H-NS will simultaneously measure hyperon and proton spin observables to explore the polarization mechanism in hadronic interactions and the spin structure of baryons. Furthermore, the use of pA and AA collisions will enable detailed investigations of cold and hot nuclear matter effects on spin polarization. Its physics program and detector development will significantly benefit the future Electron-ion Collider in China.

Abstract This study reports on the design, simulation, construction, and testing of a full-size prototype of the multi-wire drift chamber for the CSR external-target experiment. The multi-wire drift chamber array incorporates drift cells of three different sizes: 8 $$\times $$ × 8 mm $$^{\textrm{2}}$$ 2 , 10 $$\times $$ × 10 mm $$^{\textrm{2}}$$ 2 , and 15 $$\times $$ × 15 mm $$^{\textrm{2}}$$ 2 . Simulation studies were carried out to compare their electron drift time spectra, R-T relations, and position resolution. The prototype was constructed based on the design of the multi-wire drift chamber closest to the target. Since the beam passes through the center region of the multi-wire drift chamber, the prototype features a special beam avoidance design. The design ensures that the detector is sensitive to reaction products while remaining unresponsive to heavy ion beams. The size of the prototype is 930 $$\times $$ × 1660 mm $$^{\textrm{2}}$$ 2 , comprising 960 drift cells. Testing was conducted with dedicated electronics. An energy resolution of 22% was achieved for the $$^{\textrm{55}}$$ 55 Fe source; the track residuals were approximately 300 $$\upmu $$ μ m for the cosmic rays; the detection efficiency of each layer exceeds 96% for the cosmic rays.

Searching for the neutrinoless double beta decay ( 0νββ ) is crucial for studying the properties of neutrinos. Time projection chamber (TPC), with good energy resolution and track information, is an available technique. In NνDEx experiment, we proposed a TPC with high pressure ^82SeF_6 to search for 0νββ of ^82Se , which will be deployed in China Jinping Underground Laboratory. To achieve best energy resolution as possible, the readout plane consisting of about 10k custom-designed Topmetal-S chips are being developed for direct charge collection. The effective noise charge of the current generation Topmetal-S chip is presented, depending on the operational point and test condition. Understanding the gas properties is important for NνDEx experiment. With laser beam and a small TPC, we observed the minority and majority charge carriers in structurally similar SF_6 gas with electric fields from 735 to 1351 V/cm and pressures from 377 to 750 Torr, which paves the way for future study of the SeF_6 gas.

The cooler storage ring (CSR) external-target experiment (CEE) is a large-scale fixed-target heavy-ion collision experiment under development at the heavy-ion research facility in Lanzhou (HIRFL). A critical subsystem for beam monitoring and primary vertex reconstruction is the beam-particle monitor (BPM). This detector comprises two micro-TPCs integrated within a common gas chamber to simultaneously measure the transverse positions and timing information of individual beam particles. To meet stringent performance requirements, specialized pixel charge sensors and readout electronics were custom-developed for this application. Following assembly, the BPM was successfully validated through laser and Sn-ion beam tests at HIRFL. This paper describes the detector architecture and presents the results from these tests, demonstrating the system’s functionality and the achieved spatial and time resolutions.

Heavy-ion collisions(HICs)is a unique experimental tool for investigating the properties of nuclear matter under extreme conditions in the laboratory.At HIRFL-CSR energies,HICs can create nuclear matter with 2-3 times the saturation density(ρ0).The HIRFL-CSR external-target experiment(CEE)is a large-acceptance spectrometer designed to explore frontier top-ics in high-energy nuclear physics,such as the QCD phase structure and nuclear matter equation of states.In this letter,we introduce simulation and analysis software for the CEE experiment(CeeROOT).Based on the CEE conceptual design and CeeROOT software,the configurations of its subdetectors were optimized by considering foreseeable physical constraints.The final detector layout of the CEE spectrometer and its acceptances were validated through simulations of U+U collisions at 500 MeV/u and pp collisions at 2.8 GeV,which demonstrated that the CEE experiment will serve as a detector with wide acceptance and multi-particle identification capabilities for studying high-energy nuclear physics topics at HIRFL-CSR energies with pp,pA,and AA collisions.

The cross section for the J(pi) (T) = 3( +)(0) state was measured to be enhanced in an isolated "Li nucleus compared to the same reduced state in a "Li cluster. This difference demonstrates a nuclear medium modification of the tensor force, which is sensitively probed by the T = 0 channel. In contrast, the J(pi) (T) = 0 (+) (1) state (T=1) was found to have approximately equal excitation strength in both Li-6 systems. We interpret this tensor force modification as a consequence of density saturation within a many-body interaction framework.

Experimental and theoretical investigation of the fragmentation reaction in the Fermi-energy domain is currently of particular importance for not only nuclear physics but also some interdisciplinary fields.In the present study,neutron-rich 14C and 16C ion beams at 27.5 MeV/nucleon were used to bombard carbon and polyethylene(CD2)n targets.Energy and angular distributions of the produced fragments were measured.Background events ori-ginating from the carbon content in(CD2)n target were efficiently excluded using an extended E-P plot method.Ex-perimental results are systematically analyzed using the HIPSE-SIMON dynamic model.The comparison reveals that,for the carbon target,the HIPSE-SIMON calculation overestimates the yields of the beam-velocity component for fragments near the projectile and also the energy phase space for fragments far away from the projectile,suggest-ing that fine tuning of the overall interaction profile adopted in the model is required.In contrast,for reactions with the deuteron target,the model calculation can reasonably reproduce the experimental data.The implication of the fragmentation mechanism on the validity of the invariant mass method,as frequently used to reconstruct the cluster-ing resonant structures in light nuclei,is also discussed.

The semicylindrical time projection chamber (scTPC) is designed to measure the angular distribution of the cross section for intermediate-energy (3He,t) charge-exchange reactions in inverse kinematics. The scTPC prototype comprises a cathode, field cage, drift region, amplification structure based on a multilayer thick gas electron multiplier (THGEM), and a readout plane with 886 zigzag-shaped pads. The gain uniformity of the THGEM and the drift velocity of electrons were calibrated. Track recognition based on the Hough transform was then developed to reconstruct cosmic ray tracks and determine their position resolution. The position resolution of secondary particle tracks resulting from collisions between the heavy-ion beam and the 3He target was measured, yielding an x-resolution of 0.71 mm and a z-resolution of 0.73 mm. The scTPC demonstrates sufficient energy and spatial resolution to support charge-exchange reaction experiments in inverse kinematics.

A gaseous beam monitor utilizing gas electron multiplier (GEM) and pixel sensors is being developed for the Cooling Storage Ring (CSR) External-target Experiment (CEE) at Heavy Ion Research Facility in Lanzhou (HIRFL). The beam monitor is mainly used to track each beam particle, providing an accurate reconstruction of the primary vertex of the collision. Two generations of the pixel sensors (named Topmetal-CEE) were produced, with the second generation's performance improving over the first one. The design and performance of the prototype are described in the paper. Characterization of the prototype with heavy-ion beams and laser beams are presented, showing a spatial resolution better than 50 μm and a time resolution better than 15 ns.

The neutron-neutron (nn) correlation function has been measured in 25  MeV/u ^{124}Sn+^{124}Sn reactions. Using the Lednický-Lyuboshitz approach, the nn scattering length and effective range (f_{0}^{nn}, d_{0}^{nn}), as well as the reduced space-time size R^{(0)} of the neutron emission source are simultaneously extracted as (18.9_{-1.2}^{+1.3}  fm, 1.9_{-1.0}^{+1.3}  fm) and 4.12±0.12  fm, respectively. The measured nn scattering length is consistent with the results obtained in the low-energy scattering ^{2}H(π^{-},γ)2n, indicating heavy-ion collisions can serve as an effective approach for measuring nn interactions and further investigating the charge symmetry breaking of nuclear force. The space-time size extracted from momentum-gated correlation functions exhibits clear dependence on the pair momentum, with R^{(0)}=2.8±0.1  fm and 4.9±0.2  fm being determined for the high and low momentum neutrons, respectively.

The Time Projection Chamber (TPC) serves as the central detector of the Cooling Storage Ring External-target Experiment (CEE) spectrometer, designed to precisely measure dE/dx, momentum information, and charged particle trajectories of large-angle reaction products in nuclear experiments conducted at the Heavy Ion Research Facility in Lanzhou (HIRFL). To achieve accurate tracking of charged particles in the large-angle region and enable particle identification in conjunction with other detectors, real-time monitoring and control of the detector system are essential. For this purpose, a Slow Control System (SCS) was developed and implemented using the Experimental Physics and Industrial Control System (EPICS) software toolkit. This system monitors and controls the TPC's operational parameters, including gas flow, laser system performance, front-end electronics, and environmental conditions, while also overseeing auxiliary devices in real time. Such comprehensive monitoring ensures high-precision position and time measurements with the detector. This paper presents the design, components, commissioning, operation, and performance evaluation of the TPC SCS.

The cooling storage ring external-target experiment is a large-scale nuclear physics experiment, which aims to study the physics of heavy-ion collisions at low temperatures and high baryon densities. A beam monitor (BM) is placed in the beam line to monitor the beam status and to improve the reconstruction resolution of the primary vertices. The radiation dose and particle fluence stemming from the beam interactions with gases and detector materials affect the performance of the sensors and electronics of BM. This paper uses FLUKA Monte Carlo code to simulate the radiation environment of BM detector. Radiation quantities including the total ionizing dose, 1 MeV neutron equivalent fluence, high-energy hadron flux, thermal neutron flux, and nuclear fragment flux are presented. Results of alternative simulation setups, including adding shielding layers inside the BM, are also investigated.

Integrated circuits (ICs) are widely used in spacecraft and are concerned with the probability of single-event effects (SEEs). To accurately locate the SEE-sensitive area of ICs, we have designed Hi'Beam-SEE for the SEE experiment terminal at heavy-ion facilities. The Hi'Beam-SEE consists of three subsystems: the heavy-ion positioning system (HIP) is responsible for locating the position of each particle in the beam, the single-event detection (SED) system detects the SEEs that occurred in the device under test (DUT), and the online tracking algorithm extracts and reconstructs the position of each particle that triggers SEEs. The beam test with Kr-84(18+) particles demonstrates that the HIP can achieve a spatial resolution of 4 mu m in measuring every single particle's position. Also, the SED system can identify SEEs correctly and issue triggers with good timing accuracy. The online tracking algorithm can process 172 frames that contain tracks per second and extract the positions with an accuracy of 3.2 mu m . In addition, it attains a rejection factor of 93.6% while keeping the signal efficiency of 99%. This article will discuss the design and performance characterization of the Hi'Beam-SEE.

A half-size prototype of the multi wire drift chamber for the cooling storage ring external-target experiment (CEE) was assembled and tested in the 350 MeV/u Kr + Fe reactions at the heavy-ion research facility in Lanzhou. The prototype consists of six sense layers, where the sense wires are stretched in three directions X, U, and V; meeting 0^∘ , 30^∘ , and -30^∘ , respectively, with respect to the vertical axis. The sensitive area of the prototype is 76 cm× 76 cm . The amplified and shaped signals from the anode wires were digitized in a serial capacity array. When operating at a high voltage of 1500 V on the anode wires, the efficiency for each layer is greater than 95 301 ± 2 μm . This performance satisfies the requirements of CEE.

In the NνDEx collaboration, a high-pressure gas TPC is being developed to search for the neutrinoless double beta decay. The use of electronegative 82SeF6 gas mandates an ion-TPC. The reconstruction of the z coordinate is to be realized by exploiting the feature of multiple species of charge carriers. As the initial stage of the development, we studied the properties of the SF6 gas, which is non-toxic and has a similar molecular structure to SeF6. In the paper, we present the measurement of drift velocities and mobilities of the majority and minority negative charge carriers found in SF6 at a pressure of 750 Torr, slightly higher than the local atmospheric pressure. The reduced fields range between 3.0 and 5.5 Td. This was performed using a laser beam to ionize the gas inside a small TPC, with a drift length of 3.7 cm. A customized charge-sensitive amplifier was developed to read out the anode signals induced by the slowly drifting ions. The closure test of the reconstruction of the z coordinate using the difference in the velocities of the two carriers was also demonstrated.

The emission of neutrons from heavy ion reactions is an important observable for studying the asymmetric nuclear equation of state and the reaction dynamics. A 20-unit neutron array has been developed and mounted on the compact spectrometer for heavy ion experiments (CSHINE) to measure the neutron spectra, neutron- neutron and neutron-proton correlation functions. Each unit consists of a 15 x 15 x 15 cm3 plastic scintillator coupled to a cent = 52 mm photomultiplier. The Geant4 simulation with optical process is performed to investigate the time resolution and the neutron detection efficiency. The inherent time resolution of 212 ps is obtained by cosmic ray coincidence test. The n-y discrimination and time-of-flight performance are given by 252 Cf radioactive source test and beam test. The neutron energy spectra have been obtained in the angular range 30 degrees <= B lab <= 51 degrees in the beam experiment of 124 Sn + 124 Sn at 25 MeV/u with CSHINE.