Plasma-based acceleration (PBA) has emerged as a promising approach to achieve ultra-high gradient particle acceleration. While extensive PBA studies have been conducted using laser, electron, and proton drivers, significant challenges remain in achieving high efficiency, high-energy gain, and high beam quality. In contrast, due to the high beam charge density, large particle mass, and high kinetic energy, heavy ion beam drivers represent an interesting direction in PBA research. This paper presents the first investigation of plasma wakefield acceleration driven by a heavy ion beam. Using high-intensity and high-energy heavy ion beams provided by the high-intensity heavy-ion accelerator facility, our simulations show that heavy ions can excite plasma wakefields up to 6 GV/m and accelerate electrons from an initial 16-675 MeV, with an energy spread of 1.5%. These results indicate that heavy ion-driven plasma wakefield acceleration could become a promising approach for generating high energy, high-intensity bunches in single acceleration stage for future applications.

The dynamic vacuum effect is the primary limitation of beam intensity in high-intensity heavy-ion synchrotrons. Although the dynamic vacuum effect in the arc section is mitigated effectively by the beam collimators, the gas desorption induced by injection beam loss occurring in the injection electrostatic septum (ESi) is still an unresolved issue. In addition, the gas desorption is enhanced due to some special mechanisms, including the ultrafast beam loss process, multiple traversals of wire surfaces, and high-voltage breakdown. Mitigating the dynamic vacuum effect in the ESi is a critical approach to achieve a higher beam intensity. Therefore, a novel ES collimator is proposed to reduce beam deposition on the septum. Dynamic simulation of the dual-plane painting injection of BRing reveals the excellent performance of this scheme by a tenfold reduction in beam loss. The features associated with collimation efficiency and structure optimization are analyzed in detail.

We propose an innovative dipole magnet vacuum chamber design to minimize eddy currents based on a thin-wall stainless steel outer envelope supported by a titanium alloy ring structure. The internal surface of the chamber is coated with a thin layer of Ti-Zr-V non-evaporable getter (NEG) film to decrease the pressure gradient. The present study characterizes the ultimate pressure, the pumping speed, and the adsorption capacity of Ti-Zr-V both at room temperature and at liquid nitrogen temperature (LN2), and likewise for Ti film. Monte Carlo draws were used to obtain an accurate getter film sticking probability, and the results indicate that in the NEGcoated chamber saw a significant decrease in pressure from 5.8 x 10- 9 Pa at 295 K to 9.28 x 10- 10 Pa at 80 K. Furthermore, the maximum sticking probabilities of H2 for Ti-Zr-V film at 295 K and 80 K were 0.002 and 0.006, respectively. Thus, the Ti-Zr-V film has a measurable adsorption capacity at low temperature. The initial pumping rate of the Ti film for H2 at 80 K was higher than that of the Ti-Zr-V film, but the Ti film saturated faster. Finally, the average calculated static pressure in the arc section of the HIAF-BRing vacuum system with an NEGcoated titanium alloy-lined thin-wall chamber was found to be less than 3.2 x 10- 10 Pa at low temperature.

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.

The construction of the first phase of the High energy FRagment Separator (HFRS Phase-I) has already been completed and it is anticipated to start beam commissioning in autumn 2025. This paper presents the first order and higher order beam optics calculations for the HFRS Phase-I, based on measured magnet data, and evaluates its experimental performance in preparation for beam commissioning. The first order optics of HFRS is calculated based on the sliced magnetic fields and the higher order aberrations are corrected using a self-compiled program. Monte Carlo particle tracking is employed to analyze the beam phase spaces on the focal planes, and a thorough examination of these phase spaces demonstrates that the higher order aberrations have been well corrected. Moreover, simulations of the HFRS are performed based on the corrected higher order optics, yielding satisfactory results: the secondary beams of interest can be well separated and exhibit high transmission efficiency. This work provides valuable insights for the upcoming beam commissioning of HFRS Phase-I. The effective correction of higher order aberrations and optimized magnet settings lay a solid foundation for future experiments.

The dynamic vacuum effect is the primary constraint on beam intensity in high-intensity heavy-ion syn chrotrons. The dynamic vacuum effect induced by the charge exchange beam loss significantly limits the ion intensity and beam lifetime in the booster ring (BRing) of the HIAF. The collimator is a critical and indis pensable component for mitigating the dynamic vacuum effect in high-intensity heavy-ion circular accelerators. A dedicated collimation system was designed for BRing to decrease ion-induced gas desorption and suppress the dynamic vacuum effect. Nevertheless, this intercepting structure may introduce longitudinal and transverse beam coupling impedances in BRing. In this study, comprehensive investigations were conducted to charac terize the beam-coupling impedance of a movable collimator. Furthermore, we systematically describe the results of the single- and two-wire bench transmission measurements and numerical simulations. Satisfactory agreement was obtained between the numerical simulations and wire transmission bench measurements. The heat deposition power on each part of the collimator due to the longitudinal impedance was evaluated. The 24 movable collimators were processed and entered the online installation stage of the Booster Ring.

The Space Environment Simulation and Research Infrastructure (SESRI) was proposed in China to support space science research in material physics, biophysics, and interdisciplinary studies. A compact radiofrequency quadrupole (RFQ) accelerator with low longitudinal emittance has been designed and constructed as one of the key components of the SESRI. This RFQ, operating at 108.48 MHz, accelerates heavy ions with mass-to-charge ratios of 2 ∼ 6.53 from 4 keV/u to 300 keV/u. Two innovative beam dynamics strategies, including the adiabatic capture design and the equal separatrix-area technique, were employed to effectively tackle critical challenges in longitudinal emittance control and cavity length reduction. The adiabatic capture design ensures that the rate of change of the separatrix area is significantly smaller than the synchrotron angular frequency, ωs, thereby mitigating emittance dilution and reducing the output longitudinal emittance. The equal separatrix-area technique maintains a constant normalized separatrix area, minimizing the length of the buncher section. Furthermore, the transverse acceptance at the intersection between the buncher section and the accelerator section was optimized to ensure high transmission efficiency during practical operation. The results of error analysis indicate that this design provides enough margin for actual operation.

The Second generation heavy Ion Medical Machine (SIMM) can deliver carbon ion beams with a maximum energy of 400 MeV/u and maximum current intensity of 5 ×108 pps for cancer treatment. Radiation shielding is the most effective protection measure against the prompt radiation generated by accelerators. The FLUKA program was used to perform the radiation shielding calculations and design for SIMM. Firstly, the prompt radiation field was simulated, which indicates that the secondary neutrons are the determining factor for shielding thickness. Then, the shielding effects of different combinations were compared, and the combination of iron and concrete is selected for local shielding. Finally, the radiation shielding design was completed according to the layout of the building, the beam loss parameters and the related design standards, as well as the radiation dose rates at 58 points of interest outside the shielding met the prescribed safety criteria. The radiation shielding scheme given in this study can provide a reliable guarantee of radiation safety for SIMM.

Heavy ion beam drivers, due to their high kinetic energy, offer the potential for transferring a large amount of energy to the witness beam. Limited by the relatively low velocity of heavy ion, the dephasing length is short leading to a low energy gain of the witness beam. The conventional method that linearly increasing the plasma density is ineffective because the mismatch between the RMS beam radius and plasma skin depth will make the wakefield degrade or even disappear. In this paper, we propose a method that periodically increases and decreases the plasma density to switch the witness beam between different accelerating phases, allowing it to shift between adjacent accelerating cavities. Using this method, electrons can be accelerated up to 1.34 GeV in a distance of 1.17 m, with an energy spread of 1.1%. This method helps maintain the structure of wakefield and increase the energy transfer efficiency. It provides a potential route for generating high energy, high intensity electron beams and offers a feasible path for future heavy ion driven plasma wakefield acceleration experiments.

Plasma-Based Acceleration (PBA) has been demonstrated using laser, electron, and proton drivers. However, significant challenges remain in achieving high efficiency, stable acceleration, and scalable energy gain. Heavy ion beam drivers, with their high kinetic energy, offer the potential for greater energy transfer to the witness beam. Unfortunately, limited by the relatively low velocity of heavy ion, the dephasing length is really short leading to a low energy gain of the witness beam. Conventional method that increase plasma density linearly is ineffective in this context because the mismatch between the RMS beam radius and plasma wavelength will make the wakefield degrade or even disappear. In this paper, we propose a method that periodically switches the witness beam between different accelerating phase, allowing it to shift between adjacent accelerating cavities. Therefore, the plasma density does not only strictly increase, but also decrease. This will help maintain the structure of wakefield and increase the energy gain of the witness beam.

Dielectronic recombination (DR) experiments of highly charged ions not only provide essential atomic benchmark data for astrophysical and fusion plasma research but also serve as a stringent test for strong-field quantum electrodynamics (QED) effects, relativistic effects, and electron correlation effects. High-intensity heavy-ion accelerator facility (HIAF), currently under construction at Huizhou, China, will have a high- precision spectrometer ring (SRing) equipped with a 450 kV electron-cooler and an 80 kV ultracold electron- target. This advanced setup facilitates precise measurements of the DR process for highly charged ions in a broad range of center-of-mass energy, from meV to tens of keV. In this work, we carry out the molecular dynamics simulation of the electron beam temperature distribution of the ultracold electron-target at the SRing. The simulation results indicate that after treatment by the designed adiabatic magnetic field and acceleration field, the transverse and longitudinal electron beam temperature generated by the thermionic electron gun can be reduced from 100 meV to below 5 meV and 0.1 meV, respectively. Furthermore, we analyze the influence of this ultracold electron beam temperature on the resonance peak and energy resolution in DR experiment. The resolution gain at the SRing electron-target is particularly pronounced at small electron-ion collision energy, which provides unique experimental conditions for the DR experiments. Taking lithium-like (129)(54)Xe(51+ )and U-238(92)89+ ions for example, we simulate the DR resonance spectra at the SRing and compare them with the simulated results from the experimental cooler storage ring CSRe. The results reveal that the SRing experiments can resolve fine DR resonance structures with ultra-high energy resolution compared with those from the CSRe. This work lays a solid foundation for precise DR spectroscopy of highly charged ions at the SRing to stringent test of strong field QED effect and extraction nuclear structure information. [GRAPHICS] .

All equipment for the High Intensity heavy ion Accelerator Facility (HIAF) has been installed and beam commissioning is currently underway. This paper presents a further study on the high-precision optics, namely slice optics, of the Booster Ring (BRing) at HIAF based on measured magnetic fields, focusing on two aspects: closed-orbit distortion and optical parameter variations caused by errors, and dynamic aperture. A detailed study is conducted on the closed-orbit distortion and changes in optical parameters caused by magnet alignment errors and dipole magnet field errors. Meanwhile, A detailed study is also conducted on the dynamic aperture of BRing. The results show that the sliced optics and the original optics are comparable in terms of the impact of these errors on the closed-orbit and optical parameters. Without chromaticity correction, the dynamic aperture of the sliced optics is superior to that of the original optics; after chromaticity correction, the sliced optics is also comparable to the original optics. This study provides valuable insights for accelerator tuning and optimization.

The construction of the High Intensity heavy ion Accelerator Facility (HIAF) has been completed, with current efforts focused on subsystem commissioning. Beam commissioning is scheduled for autumn 2025, marking a critical milestone in the HIAF project. This paper presents high-precision optics calculations for the Booster Ring (BRing) of HIAF, a key component for achieving stable heavy-ion beam acceleration. Leveraging high-precision magnetic field data, each magnet is divided into hundreds of slices, thus establishing a high-precision sliced optics model for BRing. Detailed calculations of BRing's optics are presented in this work. Critical parameters including tunes and betatron functions of the lattice based on the measured magnetic fields and those of the ideal lattice have been compared. The results highlight the impact of realistic magnetic field on beam dynamics and provide essential insights for accelerator tuning and optimization. These findings serve as a fundamental reference for beam commissioning and long-term operation, ensuring beam stability and performance reproducibility in HIAF.

The muon collider has the potential to be a powerful tool for the exploration of frontiers in particle physics. In order to reach high luminosity, the 6D emittance of the muon beam needs to be reduced by several orders of magnitude. The cooling process for a muon collider involves two parts: initial six-dimensional cooling and final transverse cooling. This paper focuses on the former and proposes a conceptual design of the rectilinear cooling channel with additional dipole magnets. We first introduce a general method for designing the rectilinear cooling channel. Subsequently, we apply this method to develop two rectilinear cooling channels before and after a bunch merge system. Furthermore, we investigate the impact on cooling performance of employing π-mode rf cavities and the effect of errors in the magnetic and rf fields.

The generation of high-current MeV carbon ions from plasma by using two sequential laser pulses has been investigated with the help of three-dimensional particle-in-cell simulations. When the first laser pulse drives the expansion of the target, target-normal sheath acceleration happens, and the accelerated ions are momentum-chirped. The second laser pulse drives an additional target-normal sheath field, which has a monotonically decreasing front. The field moves together with a group of the chirped ions and dechirps them, thereby making them quasi-monoenergetic. Simulations show that, by using two laser pulses with the total laser energy of 8.5 J, a carbon ion beam with energy spectrum peaked at 1.1 MeV/u, an ion number up to 4×1011/MeV, and a divergence angle about 5° can be produced. These ions can be utilized for applications requiring high current low-energy ions with narrow energy width, especially as an injection source in traditional RF accelerators for carbon ion FLASH radiotherapy.

The stability and dependability of the cryostat will be impacted by its thermal expansion and contraction. We first examined the heat transfer, alignment, and monitoring technique in a cryo-environment from a theoretical perspective to supply the appropriate quantity of pre-compensation and guarantee alignment of the cryostat with bottom-supported at 2 K in the HighIntensity heavy-ion Accelerator Facility (HIAF). The continuous monitoring of cryo-deformation based on a Wire Position Monitor (WPM) and Micro-Alignment Telescope (MAT) was taken out respectively. We have shown by comparing the results that both WPM and MAT monitoring are accurate. At 2 K, the bottom-supported cryostat exhibited less vertical low-temperature deformation than the top-suspended one. The pre-compensation of cryo-deformation under operating conditions, such as mechanical and thermal loads on the cryostat, will benefit from the analytical results. An optimization for the design of future cryostats will also benefit from the data.

Intermolecular Coulombic decay (ICD) is considered a general phenomenon that plays a key role in many fundamental and applied fields related to biological environments. In many cases, however, the mechanisms and efficiency of ICD have yet to be uncovered. A prominent example is heavy-ion cancer therapy. Here, we report the first detection of a damaging intermolecular relaxation cascade initiated by heavy-ion bombardment of hydrated pyrimidine clusters. The process can significantly contribute to the high biological effectiveness of heavy-ion irradiation and thus might play an essential role in many radiotherapy techniques. Inner-valence ionization of the cluster initiates ICD and triggers proton transfer between water molecules, producing destructive low-energy electrons, HO^{•} radicals, and hydrated protons. Notably, the efficiency of ICD was found to increase dramatically with the number of water molecules, making ICD the dominant decay mechanism after inner-valence ionization. These findings indicate that the biological damage, caused by ICD in aqueous environments, is much more severe than was previously recognized.