Ion Linear Accelerator Research Articles

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.

Errors in the field reconstruction using CR-39 proton radiographs with high fluence variation.

CR-39 proton radiography is an experimental charged-particle backlighter platform fielded and used at OMEGA and the NIF to image electric and magnetic fields in a subject plasma. Processing a piece of CR-39 involves etching it in hot NaOH, and the etch time can greatly impact the background-to-signal ratio (BSR) in low-fluence (≲4 × 104cm-2) regions and detection efficiency in high-fluence regions (≳7 × 105cm-2). For CR-39 data with high fluence variation, these effects mean that any single etch time will result in ≳15% error in the measured signal in either the high- or low-fluence regions. This study aims to quantify the impact of the etch time on the BSR and efficiency losses and how these affect the field reconstruction. Experiments at the MIT Linear Electrostatic Ion Accelerator provided empirical values of the BSR and efficiency losses as a function of the fluence and etch time for fluences ranging from 3 × 103 to 7 × 105cm-2. Synthetic radiographs were generated with known fields and modulated based on empirical values of BSR and efficiency losses. The fields were reconstructed using a Monge-Ampère code with the modulated radiographs as input. The results indicate that combining short and long etches allows for more accurate analysis of radiographs with high fluence variation, with the mean squared error of the reconstructed fields decreasing by factors of 1.2-7 compared to the reconstructions using only one etch time.

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.

Image plate multi-scan response to fusion protons in the range of 1-14 MeV.

Image plates (IPs) are a quickly recoverable and reusable radiation detector often used to measure proton and x-ray fluence in laser-driven experiments. Recently, IPs have been used in a proton radiography detector stack on the OMEGA laser, a diagnostic historically implemented with CR-39, or radiochromic film. The IPs used in this and other diagnostics detect charged particles, neutrons, and x-rays indiscriminately. IPs detect radiation using a photo-stimulated luminescence (PSL) material, often phosphor, in which electrons are excited to metastable states by ionizing radiation. Protons at MeV energies deposit energy deeper into the IP compared with x rays below ∼20keV due to the Bragg peak present for protons. This property is exploited to discriminate between radiation types. Doses of mono-energetic protons between 1.7 and 14MeV are applied to IPs using the MIT linear electrostatic ion accelerator. This paper presents the results from consecutive scans of IPs irradiated with different proton energies. The PSL ratios between subsequent scans are shown to depend on proton energy, with higher energy protons having lower PSL ratios for each scan. This finding is separate from the known energy dependence in the absolute sensitivity of IPs. The results can be compared to complimentary work on x rays, showing a difference between protons and x rays, forging a path to discriminate between proton and x-ray fluence in mixed radiation environments.

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.

ISOLATION OF ELECTRONS BY THE MAGNETIC FIELD OF A CUSP FOR HIGH-DENSITY ION BEAM ACCELERATION

2.5D numerical simulation was carried out of the process of ions isolation from electrons of a compensated ion beam by the cusp magnetic field of the before entering the accelerating gap located in the region of zero magnetic field of the cusp, followed by the compensation of the accelerated ion beam with new electrons and transportation of the compensated ion beam to the next section of the linear induction ion accelerator. In contrast to the previously simulated compensated high-current ion beam with an energy of 250 keV (now non-existent), the equivalent plasma flow of a traditional coaxial plasma gun with real parameters: density 1010…1012 cm-3 and velocity 107 cm/s was considered as an injected compensated ion beam.

HIGH-VOLTAGE MODULATOR FOR ION LINAC INJECTOR WITH SMOOTH PULSE DURATION CONTROL

The ion linear accelerators stable operation essentially depends on the ion injector. To ensure maximum capture of the ion beam injected into the accelerating structure, the injector must be able to adjust the beam parameters. The paper describes the developed new injector power supply system, built on modern assemblies, which allows smoothly changing the modulator pulse duration in the range of 300…2000 µs. The analysis was carried out and the shortcomings of the previous systems were eliminated. The expected increase in the accelerated ion beam current is 15…20%. Related results include a decrease in the parasitic load capacitances of pulsed devices, a reduction in size, and the rejection of high-voltage isolation transformers, which increases the reliability of the accelerator.

Example Radiation Oncology Policy for Managing Patients With Implanted Electronic Devices Other Than Implantable Cardiac Pacemakers or Defibrillators

This article describes a community-based hospital's policy for the management of patients with medical implanted electronic devices other than pacemakers or implanted cardiac defibrillators (ICDs). The policy may be adapted as needed for other radiation oncology groups requiring a practical solution for managing the care of patients with implanted devices, noting the need for changes for departments offering proton, neutron, heavy ion, or magnetic resonance-guided linear accelerator (MR-linac) treatment modalities. The policy was developed using a risk-based approach, with each patient's risk level determined based on the patient's dependence on the device, the anticipated dose to the device, and the type of treatment used. A similar approach is used for patients with pacemakers or ICDs, but this policy was designed to accommodate patients with other types of devices with care managed outside the department. Such devices include, but are not limited to, hepatic pumps, intrathecal pain pumps, neurostimulators, cochlear implants, and loop recorders. The resulting definitions, guidelines, and proposed workflow were presented at the institution's multidisciplinary radiation oncology quality assurance committee monthly meeting and adopted as department policy in 2022. Recommendations incorporated in the policy include levels of patient monitoring and timing of device interrogation to minimize the risk of device malfunction. The policy was written to guide the management of treatment of patients with a range of medical implanted electronic devices. This policy is currently in operation at a community-based hospital.

DYNAMION—A Powerful Beam Dynamics Software Package for the Development of Ion Linear Accelerators and Decelerators

Numerous ambitious particle accelerator facilities, based on proton and ion linear accelerators, have recently been in development for fundamental research, as well as for industrial applications. The advanced design of such new machines, as well as the upgrade and optimization of existing linacs, requires adequate, precise and reliable tools to simulate beam dynamics. The software package DYNAMION, created about 30 years ago, is undergoing systematic improvement and further development in order to characterize modern ion linacs and to provide solutions for its intrinsic complex problems. The DYNAMION code features Front to End beam dynamics simulations under space charge conditions in a linac system, comprising an arbitrary sequence of accelerating-focusing structures and beam transport lines. The evolution of a macroparticle ensemble could be analyzed at a high level of specification. A 3D distribution of the external electrical field (RFQ, DTL) is modeled using integrated internal solvers. Optionally, a 3D electromagnetic field mapping, supplied by specialized external codes, could be used. The recent status of the DYNAMION software package is presented in this paper. Furthermore, the performance of the code is demonstrated on the basis of its application for various linear accelerator/decelerator projects.

Low beta superconducting cavity system design for HIAF iLinac

A superconducting ion-Linac (iLinac), which is supposed to work as the injector in the High Intensity heavy-ion Accelerator Facility project, is under development at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. The iLinac is a superconducting heavy ion linear accelerator approximately 100 meters long and contains 96 superconducting cavities in two types of 17 cyromodules. Two types of superconducting resonators (quarter-wave resonators with a frequency of 81.25 MHz and an optimal beta β = v/c = 0.07 called QWR007 and half-wave resonators with a frequency of 162.5 MHz and an optimal beta β = 0.15 called HWR015) have been investigated. The cavity design included extensive multi-parameter electromagnetic simulations and mechanical analysis，and its results are described in details. The fundamental power coupler and cavity dynamic tuner designs are also presented in this article. The prototypes are under manufacturing and expected to be ready in 2023.

Extremum Seeking-Based Control System for Particle Accelerator Beam Loss Minimization

Particle accelerators throughout the world vary widely in terms of age and availability of advanced noninvasive diagnostics that provide varying levels of detail about the accelerated beams. Beam loss measurements and current monitors are ubiquitous in the accelerator community, they are noninvasive, and they are some of the most important metrics in terms of preventing damage or irradiation of beam pipes and equipment for high-energy machines. However, beam loss and current measurements are difficult to use for feedback tuning because of a lack of a known analytic relationship between scalar loss measurements throughout an accelerator and the hundreds of thousands of parameters that influence the beam and time variation of the beam source itself. In this work, we present a model-independent extremum seeking (ES) controller, which has been implemented for automated tuning and optimization of the Los Alamos Neutron Science Center (LANSCE) linear ion accelerator based only on scalar quantities, such as beam loss or flux measurements. We demonstrate the approach on various accelerator subsystems, including groups of radio frequency (RF) accelerating cavities, quadrupole magnets, bending magnets, and steering magnets. This tool is now available as a use graphical user interface (GUI) in the LANSCE control room, allowing beam physicists to choose arbitrary groups of parameters and beam loss or current monitors for adaptive tuning.

Beam power scale-up in micro-electromechanical systems based multi-beam ion accelerators.

We report on the development of multi-beam radio frequency (RF) linear ion accelerators that are formed from stacks of low cost wafers and describe the status of beam power scale-up using an array of 112 beams. The total argon ion current extracted from the 112-beamlet extraction column was 0.5 mA. The measured energy gain in each RF gap reached as high as 7.25 keV. We present a path toward using this technology to achieve ion currents >1 mA and ion energies >100 keV for applications in material processing.

RF Power Generating System for the Linear Ion Accelerator

RF Power Generating System for the Linear Ion Accelerator

Laser ion source in injection facility of NICA project

In the framework of the NICA project for the development of an accelerator collider facility at the LHEP JINR, Dubna, the design and commissioning of two injectors are under way. The Heavy Ion Linear accelerator (HILAC) is intended to inject the gold ions into the superconducting synchrotron Booster and designed to accelerate particles with a charge-mass ratio Z/A ≥ 0.16 up to an energy of 3.2 MeV u−1. HILAC in 2015 installed in the workplace in the hall of the injection facility. In 2018, a series of tests on HILAC commissioning had been done to measure the energy and estimate transmission of accelerated beams of the carbon ions from the laser ion source. The Light Ion Linear accelerator (LILAC) is intended for injection into the superconducting synchrotron Nuclotron the polarized deuterons and protons, as well as the light ions from LIS and is in the design stage for accelerating particles with a charge-mass ratio of Z/A ≥ 0.33 to 7 MeV/u. The stable beam intensity from LIS is strongly desirable for the tasks listed above. The article describes the use of the beams from a laser ion source based on an Nd:YAG laser in the injection facility and presents a method for solving the problem of beam instability due to uncontrolled emission caused by reflected radiation.

Quench Analysis of an LTS Quadrupole Triplet Magnet System for the IBS RAON In-Flight Fragment Separator

In this paper we present quench analysis results of a Low-Temperature Superconducting (LTS) quadrupole triplet magnet system, a part of the In-flight Fragment (IF) separator of a heavy ion linear accelerator complex, named RAON, currently being constructed by the Institute of Basic Science (IBS). This magnet system is composed of three quadrupole magnets: a triplet, surrounded by iron yokes and embedding hexapole/octupole LTS coils for field correction. The magnet will be operated at 4.2 K in liquid helium. For reliable and safe operation of this complex superconducting system, quench and protection analysis with possible failure scenarios must be performed. In this paper, we first discuss probable quench scenarios and then present results of the quench propagation analysis on: 1) coil currents and voltages by multi-coil model circuit analysis; and 2) simulated temperature distribution inside each coil. Our quench analysis results show that the maximum voltage and temperature in each coil are below safety limits, 2000 V and 150 K, respectively, and confirm that this quadruple triplet magnet system is self-protecting.

ION BEAM PROPAGATION STABILITY IN A LINAC ACCELERATING CHANNEL BASED ON COMBINED RF-FOCUSING

The issue of simultaneous longitudinal and transverse particle propagation stability in a linear ion accelerator channel based on combined RF-focusing is investigated. Values for RFQ field gradient to provide transverse propagation stability for all the particles in an acceleration mode are calculated. It is also shown that electrical strength of the electrodes influences the gradient value. Much attention is given to modeling of an accelerating-focusing channel which provides the minimal growth in beam emittance.

Advances of the FRIB project

The Facility for Rare Isotope Beams (FRIB) Project has entered the phase of beam commissioning starting from the room-temperature front end and the superconducting linac segment of first 15 cryomodules. With the newly commissioned helium refrigeration system supplying 4.5[Formula: see text]K liquid helium to the quarter-wave resonators and solenoids, the FRIB accelerator team achieved the sectional key performance parameters as designed ahead of schedule accelerating heavy ion beams above 20[Formula: see text]MeV/u energy. Thus, FRIB accelerator becomes world’s highest-energy heavy ion linear accelerator. We also validated machine protection and personnel protection systems that will be crucial to the next phase of commissioning. FRIB is on track towards a national user facility at the power frontier with a beam power two orders of magnitude higher than operating heavy-ion facilities. This paper summarizes the status of accelerator design, technology development, construction, commissioning as well as path to operations and upgrades.

Use of MeV energy ion accelerators to simulate the neutron damage in fusion reactor materials

This paper describes experimental techniques for irradiation of fusion reactor materials with MeV energy ions. The studies were conducted at the NRC “Kurchatov Institute” – ITEP. Two MeV-range linear ion accelerators were used for sample irradiation: the Heavy Ion Prototype (HIPr) accelerator with heavy ions and I-2 accelerator with protons. Target chambers of HIPr accelerator were modified to provide the simultaneous irradiation of four 10 × 10 mm2 samples at controlled elevated temperatures. Damage rates and profiles were calculated using the SRIM code. HIPr accelerator provided the damage of tungsten samples with 5.6 MeV Fe2+ ions at a rate of 0.05 dpa/h. I-2 accelerator was used to irradiate tungsten samples with 22 MeV protons to create a uniform damage profile at a depth of 0–400 μm with a rate of 5 × 10−7 dpa/h. Irradiation of tungsten samples with high energy protons causes generation of 183Re and 184Re with a half-life period of 70 and 38 days, respectively. Thus, the samples irradiated with a proton fluence of up to 1020 protons/m2 are subject to one year aging before manual handling.

Heavy ion linear accelerator for radiation damage studies of materials.

A new eXtreme MATerial (XMAT) research facility is being proposed at Argonne National Laboratory to enable rapid in situ mesoscale bulk analysis of ion radiation damage in advanced materials and nuclear fuels. This facility combines a new heavy-ion accelerator with the existing high-energy X-ray analysis capability of the Argonne Advanced Photon Source. The heavy-ion accelerator and target complex will enable experimenters to emulate the environment of a nuclear reactor making possible the study of fission fragment damage in materials. Material scientists will be able to use the measured material parameters to validate computer simulation codes and extrapolate the response of the material in a nuclear reactor environment. Utilizing a new heavy-ion accelerator will provide the appropriate energies and intensities to study these effects with beam intensities which allow experiments to run over hours or days instead of years. The XMAT facility will use a CW heavy-ion accelerator capable of providing beams of any stable isotope with adjustable energy up to 1.2 MeV/u for 238U50+ and 1.7 MeV for protons. This energy is crucial to the design since it well mimics fission fragments that provide the major portion of the damage in nuclear fuels. The energy also allows damage to be created far from the surface of the material allowing bulk radiation damage effects to be investigated. The XMAT ion linac includes an electron cyclotron resonance ion source, a normal-conducting radio-frequency quadrupole and four normal-conducting multi-gap quarter-wave resonators operating at 60.625 MHz. This paper presents the 3D multi-physics design and analysis of the accelerating structures and beam dynamics studies of the linac.

Piezoelectric actuator based phase locking system to improve the dynamics of the control scheme for a heavy ion superconducting linac

The superconducting heavy ion linear accelerator at Inter-University Accelerator Centre Delhi has been in operation since 2007. Initially, the superconducting niobium Quarter Wave Resonators (QWRs) in the linac were phase locked using a combination of electronic and mechanical controls which operated in fast (~10μsec) and slow (~sec) time scales respectively. In this scheme, fast control was achieved through dynamic phase control whereas slow control of the frequency was done through the niobium tuner bellows installed at the drift tube end of the resonator and flexed using helium gas to change the resonance frequency. In order to improve the dynamics of this control system, an alternate scheme using piezoelectric actuator, instead of helium gas, to flex the same niobium bellows, has been implemented in the QWRs of the second and third accelerating modules of the linac. The piezoelectric actuator is used in closed loop along with the fast dynamic phase control scheme. The feedback loop of the piezoelectric control includes a dual control scheme - an integral control loop to arrest the slow drift, and the positive position feedback (PPF) based control loop to damp the microphonics. This control scheme has been found to arrest slow drifts in the resonator frequency more tightly along with damping of low frequency microphonics (~few tens of Hz) picked up by the resonator from its surrounding environment. This has substantially eased the load from the fast electronic control, resulting in the reduction of the radio frequency (RF) power requirement during operation. In addition, it has improved the stability of phase and amplitude of the QWRs. The details of the new scheme along with results obtained during the online run of the linac for beam acceleration are presented.