Heavy Ion Accelerator Research Articles

New Architecture Design of Magnetic Field Monitoring System Based on HIAF

The High-Intensity Heavy Ion Accelerator Facility (HIAF) is one of China's major scientific and technological infrastructure projects, aimed at providing an internationally leading research platform for nuclear physics, nuclear astrophysics, nuclear energy development, nuclear safety, and materials science. During the operation of HIAF, the high-precision measurement and control of magnetic fields are crucial for the stable operation of core equipment. To meet the high demands of HIAF for precision, real-time performance, and system autonomy in magnetic field measurement, this research designs and implements a high-precision magnetic field measurement system based on the LACCS (Large-scale Accelerator Cluster Control System) architecture. The system integrates advanced hardware and software designs, enabling it to efficiently and accurately complete distributed magnetic field measurement tasks, thus providing technical support for the smooth operation of HIAF.

Design of a time to digital converter for LGAD detector at HIAF complex

The High-Intensity Heavy-ion Accelerator Facility (HIAF) is a leading platform for heavy-ion scientific research in China with advanced beam current indicators. In these experiments, Low-Gain Avalanche Detectors (LGAD) have become the detector of choice, and the readout circuit of LGAD requires time-to-digital converters (TDC) to convert the time measurement results into digital signals. Since a smaller pixel area is conducive to improving positional resolution and spatial resolution, a TDC using calibration modules instead of delay-locked loops (DLLs) is proposed to achieve lower power consumption and area. The proposed TDC is a 3-stage architecture, reaching an extensive dynamic range and a high resolution. In addition, calibration modules are used to measure the relationship between two adjacent stages of resolution. Thus, the resolution of the TDC could be confirmed under the influence of process, voltage, temperture (PVT) variation. Compared with the TDCs using DLLs, the proposed TDC reduces the power consumption and area. The resolution of the proposed TDC is about 5.13 ps, and the dynamic range is 25.2 ns. The integral nonlinearity (INL) and the differential nonlinearity (DNL) are both less than 0.3 least significant bit (LSB). Including two TDCs, which measure the time of arrival (TOA) and the time of threshold (TOT), respectively, the layout area is 931 μm × 447 μm

Precision spectroscopy of dielectronic recombination experiments for highly charged ions at large facility HIAF: a simulation study

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, has 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 across a broad range of center-of-mass energies, from meV to tens of keV. In this study, we employ molecular dynamics methods to simulate the electron beam temperature distribution of the ultracold electron-target at the SRing. The simulation results indicate that, following the designed adiabatic magnetic field and acceleration field treatment, the transverse and longitudinal electron beam temperature from the thermionic electron gun can be reduced from 100 meV to below 5 meV and 0.1 meV, respectively. Furthermore, we analyze the impact of this ultracold electron beam temperature on the resonance peaks and energy resolution in DR experiments. The resolution gain at the SRing electron-target is particularly pronounced at small electron-ion collision energies, which provides unique experimental conditions for the DR experiments. Using lithium-like ${ }_{54}^{129} \mathrm{Xe}^{51+}$ and ${ }_{92}^{238} U^{89+}$ ions as examples, we simulate the DR resonance spectrum 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 to those from the CSRe. This work lays the foundation for precise DR spectroscopy of highly charged ions at the SRing to stringent test of the strong-field QED effects and extract nuclear structure information.

Beam dynamics design and optimization of a standalone radio frequency quadrupole accelerator for swift heavy ions

Abstract A standalone high energy, 352 MHz radio frequency quadrupole (RFQ) design is presented, resulting into targeted energy gain of 1.8 MeV/u with a beam current of 1 mA for mass to charge (A/q) ratio ≤ 4. It avoids many separate stages of transverse and longitudinal matching of beams compared to a standard RFQ + DTL accelerator combination due to automatic adiabatic bunching, focusing and acceleration of the beam and thus prevent many beam diagnostic and vacuum components. It is compact (only 4.63 meters) comparatively to other accelerator of equivalent energy gain and operation is quite easy in terms of beam tuning. The beam dynamics and vane designs are presented in details using PARMTEQ and Poisson/Superfish code. Such an accelerator promises to be a good candidate for establishing compact and more efficient nuclear physics research facilities compared to electrostatic Pelletron accelerators.

Utilization strategies of beam dumps for High energy FRagment Separator (HFRS) at HIAF

The construction of the High Intensity heavy-ion Accelerator Facility (HIAF) is currently underway, with the High Energy FRagment Separator (HFRS) serving as a critical component. The HFRS, a next-generation in-flight radioactive separator, is designed to produce, separate, and purify rare isotopes with a maximum magnetic rigidity of 25 Tm, facilitating experimental studies on very short-lived and neutron-rich isotopes. To protect the environment and equipment, beam dumps are essential for intercepting high-intensity primary beams with different charge states post-target. Utilizing the beam optics of the HFRS and beam parameters after the target, Geant4 ion tracking simulations were employed to determine the ion trajectories of both primary beam and secondary beam. The interception efficiency for the primary beam and the transmission efficiency for the secondary beam were calculated, providing strategies and movement range for beam dump utilization. These findings are expected to contribute to the future operation of the HFRS.

Lebt of the Heavy Ion Linear Accelerator

At the NRC “Kurchatov Institute” (Kurchatov Complex for Theoretical and Experimental Physics), the pulsed linear resonant heavy ion accelerator is being developed. The Low Energy Beam Transport (LEBT) channel transports the beam from a laser-plasma source of multi-charged ions with an A/Z ratio from 4 to 8 (up to Bi27+) to the RFQ. This paper shares the results of the beam dynamics simulation of the LEBT, which ensures the separation of the working fraction of the ion beam and its matching with the RFQ.

Development of the injector for the RAON heavy-ion accelerator

Development of the injector for the RAON heavy-ion accelerator

Status of the RAON heavy-ion accelerator

Status of the RAON heavy-ion accelerator

Variable-energy cocktail beam technology for investigating synergistic damage in nuclear materials on LEAF platform

This study addresses the critical issue of synergistic radiation damage in structural materials of fusion reactors, focusing on the interaction between the displacement defects and transmutation-produced hydrogen and helium. These effects are simulated and investigated by employing the advanced multi-beam ion implantation capabilities of the LEAF (Low Energy high intensity highly charged ion Accelerator Facility) platform. Firstly, high-intensity cocktail beams, such as “4He+ and 56Fe14+" and “4He+ and 58Ni15+", are generated and characterized successfully. Then, a complex radiation environment is mimicked within the fusion reactors by applying variable-energy irradiation. Secondly, similar penetration depths for different ions, which are crucial for studying synergistic effects, are obtained by precisely controlling the energy of the cocktail beams through the innovative energy modulation system of the LEAF platform. Finally, the post-irradiation analyses, performed by using the transmission electron microscopy (TEM) and nanoindentation, revealed distinct microstructural changes and alterations in material properties, providing insights into the degradation mechanisms under irradiation. This work not only generates diverse and high-intensity “cocktail” ion beams but also achieves rapid energy switching of the beams. Further, the work is expected to pave the way for the implementation of a novel multi-beam irradiation technique in advanced heavy-ion linear accelerators, and also to provide innovative experimental methods and technical support for studying the synergistic effects of nuclear materials.

In-situ observation of heavy ion beam-induced luminescence of Al2O3 (Cr3+) in a 0 - 10 T magnetic field background.

High energy density physics driven by intense heavy ion beams will be an important new project for the high intensity heavy-ion accelerator facility and the Dongjiang Laboratory. This paper presents an experimental investigation of ion beam-induced luminescence in a strong magnetic field background at HIRFL. The experiment utilizes a 430 MeV/u 84Kr26+ ion beam with a pulse duration of 300 ns to bombard an Al2O3 (Cr3+) solid target. The results show that the characteristic emission spectrum of the Cr3+ ion's 2E→4A2 transition is observed, and spectrum parameters significantly change with the magnetic field of the background. We present the experimental data on the shifts of the peak center (Δσave) and the broadening of full width at half maximum (WG). The changes in parameters related to the intensity of the magnetic field are discussed using atomic models. This work demonstrates the potential application of diagnosing magnetic fields by measuring characteristic spectra.

Design and development of the machine protection system for HIAF

ABSTRACT The High Intensity Heavy-ion Accelerator Facility (HIAF), currently under construction, is a complex machine that couples a Continuous Wave (CW) superconducting ion Linear accelerator (iLinac) with a high-energy synchrotron to produce various stable and radioactive intense beams with energies from MeV/u to GeV/u. The machine has a versatile operation mode which requires a high flexibility and reliability to the Machine Protection System (MPS). A customized and robust MPS is designed and developed to give the readiness of the machine for operation, to mitigate and analyze faults related to the relative damage potential. To get a high speed and have a high level of reliability, all interlock signal processing is processed on radiation-tolerant Field-Programmable Gate Arrays (FPGA) with triple or dual redundancy, as well as with a fail-safe design. By implementing a multiprocessing platform system-on-chip FPGA, the HIAF MPS can be tightly integrated with other systems to maximize availability pinpoint failures for operations, and give the postmortem analysis. This paper will describe the architecture of the interlocks linking the protection systems, the strategies to manage the complexity, the detailed components, and the interlock logic of the customized HIAF MPS, as well as the test and verification of the prototype.

Design and commissioning of a two-harmonic pre-buncher for extended bunch spacing at LEAF

The Low Energy Heavy Ion Accelerator Facility (LEAF) is a low-energy, high-intensity heavy-ion linear accelerator facility at Institute of Modern Physics (IMP) for multidiscipline research. The beam bunch repetition rate coincides with the LINAC frequency of 81.25 MHz, resulting in a 12.3 ns period. However, in the context of certain nuclear physics experiments, a longer bunch spacing is deemed essential for the precise detection of experimental products. To address this need, a strategy to extend the bunch spacing to 98 ns has been proposed by integrating a pre-buncher operating at a fundamental frequency of 10.156 MHz before the radio-frequency quadrupole (RFQ) in conjunction with a fast chopper in the medium energy beam transport (MEBT) system. The pre-buncher is a pivotal component in enabling a greater beam current at the target, surpassing the capability of employing a chopper alone. To enhance the bunching efficiency, the pre-buncher operates with two frequencies: the fundamental frequency of 10.156 MHz and its first sub-harmonic of 20.3125 MHz, each of which is produced by a coaxial resonator. This paper describes the design, manufacture, off-line testing, and beam commissioning of the pre-buncher.

Demonstration of high-efficiency microwave heating producing record highly charged xenon ion beams with superconducting electron cyclotron resonance ion sources

Intense highly charged ion beam production is essential for high-power heavy ion accelerators. A novel movable Vlasov launcher for superconducting high charge state electron cyclotron resonance ion source has been devised that can affect the microwave power effectiveness by a factor of about 4 in terms of highly charged ion beam production. This approach based on a dedicated microwave launching system instead of the traditional coupling scheme has led to new insight on microwave-plasma interaction. With this new understanding, the world record highly charged xenon ion beam currents have been enhanced by up to a factor of 2, which could directly and significantly enhance the performance of heavy ion accelerators and provide many new research opportunities in nuclear physics, atomic physics, and other disciplines. Published by the American Physical Society 2024

Space radiation research with heavy ions at HIMAC

The HIMAC (Heavy Ion Medical Accelerator in Chiba) was originally designed principally for carbon ion therapy, but heavy ion research projects in medicine, physics, chemistry and biology have been conducted under a collaborative research framework since 1994. One major application is space radiation research. The radiation in space of greatest interest for human space exploration consists of energetic protons and heavy ions which can affect the health of space crew and lead to the failure of electronic devices. Ground-based experiments at heavy ion accelerators are crucial for ensuring mission crew safety and for understanding the biological effects of long-term exposure to space radiation. HIMAC provides a range of linear energy transfer (LET) beams from protons to Xe ions at energies up to 800 MeV/u, representing the most biologically-significant components of the space radiation field. At HIMAC a variety of radiation detectors and instruments are characterized and calibrated for dosimetry using specific mono-energetic heavy ion beams, the performance of shielding materials for mitigating space radiation dose is evaluated, radiation hardness of electronic devices is tested to ensure their safe operation in space, and the radiobiological studies are conducted to understand biological effects in humans during long-term space activities. HIMAC is an indispensable simulator of space radiation for the new decade of space exploration.

Study on Single Event Effects of Enhanced GaN HEMT Devices under Various Conditions.

GaN HEMT devices are sensitive to the single event effect (SEE) caused by heavy ions, and their reliability affects the safe use of space equipment. In this work, a Ge ion (LET = 37 MeV·cm2/mg) and Bi ion (LET = 98 MeV·cm2/mg) were used to irradiate Cascode GaN power devices by heavy ion accelerator experimental device. The differences of SEE under three conditions: pre-applied electrical stress, different LET values, and gate voltages are studied, and the related damage mechanism is discussed. The experimental results show that the pre-application of electrical stress before radiation leads to an electron de-trapping effect, generating defects within the GaN device. These defects will assist in charge collection so that the drain leakage current of the device will be enhanced. The higher the LET value, the more electron-hole pairs are ionized. Therefore, the charge collected by the drain increases, and the burn-out voltage advances. In the off state, the more negative the gate voltage, the higher the drain voltage of the GaN HEMT device, and the more serious the back-channel effect. This study provides an important theoretical basis for the reliability of GaN power devices in radiation environments.

Design of a Facility for Simultaneous Irradiation with Two Ion Beams based on the HIPR Accelerator for Simulations Neutron Influence

Ion accelerator facility is a powerful tool to simulate neutron irradiation effects in reactor materials. Defects in the crystal lattice arise and the accumulation of transmutation products (helium and hydrogen) occurs in the structure of the material under the action of neutrons in the structural materials of nuclear installations. At Kurchatov Complex for Theoretical and Experimental Physics the heavy ion accelerator HIPr (heavy ion prototype) is used to simulate radiation damage in steels and alloys using a 5.6 MeV Fe2+ ion beam. The second beam line is designed at the HIPr facility to simultaneously implant helium (or hydrogen) into the region of defects. The second beam line provides a beam of helium ions with energy up to 300 keV. The report presents a description of second beam line design and a status of construction the second beam line.

Management and Operator Control System based on Microservice Architecture and Application on the HIPr Accelerator

The paper describes the basic principles of developing a distributed control system (DCS) and a GARNET operator control system based on a microservice architecture as part of a high-availability cluster. The application of the operator’s control system as a DCS component is described. The main elements of software components of operator control and DCS are presented and described. The process of conveyor assembly and publication of software tools into a working product environment, which implements the principle of continuous integration, is described. The mechanism of interaction of key components among themselves is presented. The mechanism for hosting management services using the Docker containerization system and Kubernetes container orchestration is demonstrated. Examples of services for interaction with users in the environment of the GARNET operator control system being developed, separation of users by roles and access rights, integration of the data visualization service using Grafana are shown. The vector of further development of DCS and operator control tools is described, in particular, the possibility of using the practice of developing user web interfaces using the micro frontend approach. The components and results of the operation of a prototype system designed to interact with the measurement infrastructure of the linear heavy ion accelerator HIPR are presented.

The design of an integrated beam dynamics framework and its application in a heavy-ion accelerator facility

The design of an integrated beam dynamics framework and its application in a heavy-ion accelerator facility

Development of a non-intercepting weak beam current measurement electronics for Heavy Ion Accelerator Facility in Lanzhou.

Non-destructive measurements of low-intensity charged particle beams are particularly challenging for beam diagnostics. At the Heavy Ion Accelerator Facility in Lanzhou (HIRFL), beams with weak currents below 1 µA are often provided for experiments. The detection of such low beam current is below the threshold of typical standard beam current transformers. Therefore, a low-intensity monitoring system is developed by using a sensitive capacitive pick-up (PU) and low-noise electronics. This device measures beam currents by digitally analyzing the amplitude of the PU signals using a homodyne detection scheme. During lab tests, the amplitude nonlinearity is <0.5% in the operational range of 1 nA-45 µA and the amplitude resolution is 0.94 nA. At present, four measurement systems for low beam currents are installed at HIRFL for the monitoring of standard operating conditions with low beam currents below 1 µA. After an absolute calibration with a Faraday cup, it can be used for accurate beam intensity measurement with a current resolution of about 1 nA.

Ion beam stability prediction of ECR ion source based on TCN-DTW network

The Electron Cyclotron Resonance (ECR) ion source is an irreplaceable apparatus for producing high-intensity, highly charged heavy ion beams, representing a critical component for heavy ion accelerators. The operation of the ECR ion source is inherently influenced by various factors, leading to fluctuations in beam intensity. Such instability not only diminishes the efficacy of accelerator operations but also introduces distortions in terminal experimental data. Addressing these challenges, this study proposes the application of a Temporal Convolutional Network (TCN) based on a Dynamic Time Warping (DTW) loss function (TCN-DTW) for predicting the stability of the ion beams. Prior to constructing the prediction network, raw data undergoes preprocessing through an Interquartile Range (IQR) anomaly detection mechanism and the Savitzky-Golay (SG) filtering algorithm with an adaptive window. Experimental results demonstrate a substantial enhancement in prediction performance when employing the TCN network with the DTW loss function compared to traditional alternatives. This approach facilitates effective forecasting of the ion source beam current trend, offering a basis for the control and correction of long-term stability. Consequently, it provides valuable insights for optimizing the ECR ion source and enhancing overall accelerator operational performance.