Superconducting Electron Cyclotron Resonance Research Articles

ASTERICS, a new 28 GHz electron cyclotron resonance ion source for the SPIRAL2 accelerator

A new A/Q=7 injector is under development for the SPIRAL2 accelerator at Caen, France (NEWGAIN project). A new 28 GHz superconducting electron cyclotron resonance ion source named ASTERICS is under design for this project. The source features a modern cryostat and a large plasma chamber (91 mm radius and 600 mm length). The physical and technical motivations for a larger plasma volume are detailed and estimates of expected beam intensities enhancement are discussed. The source will mainly produce metallic ion beams: the concept of a temperature-controlled liner (up to 900°C) to stabilize high vapor pressure metal re-evaporation in the source is presented. The preliminary design of the ion source and its superconducting magnet are described.

Producing intense uranium ion beam for RIKEN RI beam factory

Intense highly charged uranium (U) ion beams were produced using RIKEN 28 GHz superconducting electron cyclotron resonance (ECR) ion source in a high-temperature oven (HTO). We used a double-oven system to ensure ample vapor supply. Moreover, we optimized the vapor delivery into the plasma at a constant microwave power input. Consequently, we achieved intense U-ion beams, specifically 250 eμA for U35+, 36 eμA for U46+, and 10 eμA for U54+, at an injected microwave power of approximately 3000 W. This achievement stems from recent advancements, notably the optimization of the material consumption rates aimed at maximizing beam intensity, which we briefly review here.

Shell-Based Support Structure for the 45 GHz ECR Ion Source MARS-D

Superconducting electron cyclotron resonance ion sources (ECRISs) using NbTi coils and optimized for 28 GHz resonant heating have been successfully operated for almost two decades. Moving to higher heating frequencies requires increased magnetic fields, but traditional racetrack-and-solenoid ECRIS structures are at their limit using NbTi. Rather than moving to a superconductor untested in this field, the Mixed Axial and Radial field System (MARS) being developed at Lawrence Berkeley National Laboratory employs a novel closed-loop-coil design that more efficiently utilizes conductor fields and will allow the use of NbTi in a next-generation, 45 GHz ECRIS. This article presents the design of the shell-based support structure central to the MARS-D magnet design, as well as structural analysis of its components and optimization of pre-load parameters that will guarantee its successful operation.

Production of intense pulsed beams of highly charged ions from a superconducting electron cyclotron resonance ion source

An experimental study of the afterglow mode was performed with a third generation electron cyclotron resonance ion source, SECRAL-II (Superconducting ECR ion source with Advanced design in Lanzhou No. II), under double frequency heating. The experimental results show that intense pulsed beams of highly charged ions (e.g., $266\text{ }\text{ }\mathrm{e}\ensuremath{\mu}\mathrm{A}$ of ${^{129}\mathrm{Xe}}^{34+}$ and $169\text{ }\text{ }\mathrm{e}\ensuremath{\mu}\mathrm{A}$ of ${^{129}\mathrm{Xe}}^{38+}$) could be produced at high frequency ($24+18\text{ }\text{ }\mathrm{GHz}$) and high power ($\ensuremath{\sim}8\text{ }\text{ }\mathrm{kW}$), even compared with the beam intensity records of SECRAL-II obtained in continuous wave (cw) mode at higher microwave frequency ($28+18\text{ }\text{ }\mathrm{GHz}$) and higher power ($\ensuremath{\sim}10\text{ }\text{ }\mathrm{kW}$), the gain factor is also up to $\ensuremath{\sim}3$. Meanwhile, it is found that the afterglow decay time in our study is much longer than that obtained with the second generation ECR ion sources typically operating at 10--18 GHz, and the corresponding peak duration is greater than 2 ms. This study provides a viable solution for heavy ion synchrotron accelerator complex such as High Intensity Heavy Ion Accelerator Facility project that requires intense pulsed beams of highly charged ions with long peak duration.

Superconducting Linac Booster for Super-Heavy Element Experiments at RIKEN Radioactive Isotope Beam Factory

The Rikagaku Kenkyūjo (RIKEN) heavy-ion linac was upgraded by introducing a new super-conducting linac-booster to advance the super-heavy elements synthesis program beyond nihonium at the RIKEN Radioactive Isotope Beam Factory (RIBF). The total acceleration voltage was upgraded from 25 MV with 12 room temperature drift-tube-linacs (DTLs) to 39 MV by introducing a superconducting linac booster, SRILAC. The upgrade of the beam intensity is realized by a newly constructed superconducting electron-cyclotron resonance ion source (SC-ECRIS). The construction of SRILAC and the SC-ECRIS started in FY2017. After the hardware installation and commissioning, the first beam acceleration test was successfully conducted at the end of FY2019, and user beam service was started in FY2020. This article provides an overview of the upgrade and its present performance.

A few ECRIS developments at LBNL

In addition to the ongoing investigation of bremsstrahlung radiation produced by energetic electrons in the superconducting Electron Cyclotron Resonance (ECR) ion source VENUS, the LBNL ion source group has pursued several other research topics since 2015 to explore potential advancements of ECR ion sources. Three of these activities are investigations into the benefits of non-cylindrical plasma chambers, the development of new high-temperature ovens that will efficiently produce the intense, metallic ion beams necessary for super heavy element production at the 88-Inch Cyclotron facility, and the finalization of the conceptual and engineering design of the superconducting NbTi magnet structure for the 4th generation, 45 GHz ECR ion source MARS-D. This article summarizes and briefly discusses the highlights of these ECRIS developments.

Development and status of the FRIB 28 GHz SC ECRIS

T o meet a beam power requirement of 400 kW for heavy ions, a high intensity 28 GHz superconducting Electron Cyclotron Resonance (ECR) ion source is under development at the Facility for Rare Isotope Beams (FRIB) in collaboration with Lawrence Berkeley National Laboratory (LBNL). The magnet was built and tested at LBNL and integrated into the ion source cryostat on the FRIB high voltage platform. Magnet cooldown to 4.2K was completed successfully in December of 2020. The static heat load at 4.2K has been measured to be around 1.2 W, in good agreement with the design value. The heat load is managed through 2 Gifford-McMahon/Joule-Thomson (GM-JT) cryocoolers that have been in operation for several months. Magnet energization is scheduled in November of 2021. Warm components preparation and assembly test are ongoing in parallel. The ion source commissioning with 18 GHz Klystron shall start in December of 2021. Details of the ion source development, status, and commissioning plan will be presented in the paper.

Cryostat for HECRAL Superconducting Magnet

In order to support the normal operation of HECRAL (Hybrid superconducting Electron Cyclotron Resonance ion source with Advance in Lanzhou) superconducting magnet, a cryostat in the form of immersed in liquid helium was designed, which integrated two two-stage GM (Gifford-McMahon) cryocoolers, helium vessel, thermal shield, outer Dewar, suspension structures, service turret, binary current leads, corresponding monitoring and diagnosis system. The 1st cold head of the two-stage cryocoolers were used to cool the thermal shield and HTS (High Temperature Superconducting) current leads. Enough cooling capacity in the temperature region of 4.2K was supplied by the 2nd cold head to condense the saturated helium vapor evaporated by heat load (including static heat load and dynamic heat load), to realize the “0” liquid helium evaporation operation of the superconducting magnet. The corresponding heat load of the designed cryostat was analyzed, and the WST (Western Superconducting Technologies Co., Ltd.) was commissioned to install the cryostat and carried out cryogenic excitation test. The cryostat is now operated in IMP (Institute of Modern Physics, Chinese Academy of Sciences) and all parts of the magnet and cryostat are working normally, which ensures proper operation of the ion source.

Characterization of O+ Ion‐implanted Glassy Carbon Using the Superconducting Electron Cyclotron Resonance Ion Source and Selective Dopamine Detection

AbstractThe O and N gas ions (O3+, O+, N2+, and N4+) were implanted on the glassy carbon surface employing the electron cyclotron resonance ion source, which were characterized using electrochemical and surface analysis methods. The modified electrode was examined for the catalytic oxidation of bioorganic molecules including dopamine, where the O+ ion implanted GC revealed the best catalytic performance. The XPS and Raman results represented that the ion implantation made enrichment in graphite nanocrystalline structure with edge plane, showing the enhanced electrochemical activity. It showed excellent performance for dopamine detection without significant interferences between 50.0 nM and 400.0 μM with the detection limit of 10.0±2.5 nM (95 % confidence level). The reliability of proposed electrode was evaluated by the real urine sample analysis.

Production of metallic ion beams by electron cyclotron resonance ion sources equipped with inductive heating ovens at the Institute of Modern Physics.

A high-temperature oven based on the inductive heating technology was developed successfully at the Institute of Modern Physics in 2019. This oven features a durable operation temperature of over 2000 °C inside the tantalum susceptor. By carefully designing the oven structure, the material compatibility issue at high temperature has been successfully solved, which enables the production and routine operation of refractory metal ions with SECRAL-II (Superconducting Electron Cyclotron Resonance ion source with Advanced design in Lanzhou No. 2). To further apply this type of oven to the room temperature ECR ion sources LECR4 and LECR5 (Lanzhou Electron Cyclotron Resonance ion source No. 4 and 5), a mini-inductive heating oven has been fabricated and tested in 2020. By directly evaporating calcium oxide, some high charge state calcium beams have been produced successfully, such as 52 euA of 40Ca16+, 30 euA of 40Ca17+, and 12 euA of 40Ca18+. The detailed design and testing results will be presented and discussed.

Control system for the new RIKEN 28-GHz superconducting electron cyclotron resonance ion source for SRILAC.

A new RIKEN 28-GHz superconducting electron cyclotron resonance ion source (SC-ECRIS) has been installed for the superconducting RIKEN linear accelerator (SRILAC). The new SC-ECRIS control system mainly consists of programmable logic controllers (PLCs) embedded with the Experimental Physics and Industrial Control System. To improve the reliability as compared with previous control systems, two types of PLC central processing units, sequential and Linux, have been installed in the same unit. Past experience has shown that new types of designs that can rapidly respond to system scalability are key. By connecting PLC stations using star-topology field buses, their rapid and cost-effective response to system changes is realized for the new devices. Furthermore, a unique data acquisition system employing a 920-MHz-band radio was developed to measure analog data such as the temperature at the high-voltage stage.

Mechanical Study of a Superconducting 28-GHz Ion Source Magnet for FRIB

The superconducting electron cyclotron resonance (ECR) source magnet for the facility for rare isotope beams at Michigan State University was designed and built by the Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) in 2017. The 28 GHz NbTi ion source magnet features a sextupole-in-solenoids configuration which is comparable to the VENUS ECR magnet operated at LBNL. However, the mechanical design of this magnet utilizes a shell-based support structure which allows fine adjustments to the sextupole preload and reversibility of the magnet assembly process. The magnet has been assembled and tested to operational currents at LBNL. This paper describes the mechanical analyses performed to estimate the sextupole's and solenoids' preloads. We will report on the 3-D finite element analysis during room temperature assembly, cool-down, and magnet excitation, and then describe the magnet preload operations. Finally, we will describe the performance of the support structure during the quench training.

A 45-GHz/20-kW Gyrotron-Based Microwave Setup for the Fourth-Generation ECR Ion Sources

A 45-GHz gyrotron-based microwave oscillator setup has been purposefully developed for powering of a superconducting electron cyclotron resonance (ECR) ion source. The setup provides a smoothly regulated output power in the 0.1–20-kW range (up to 26 kW in manual mode) with an efficiency of up to 50% and collector depression in both continuous wave (CW) and pulse modes. Pulse mode specifications: duration 5–200 ms, leading edge less than ${2}~\mu \text{s}$ , trailing edge less than ${1}~\mu \text{s}$ , repetition rate 1–10 Hz, and triggered operation using an external reference oscillator. The set of high-voltage power supplies (HVPSs) is equipped with a fast electronic protective system to ensure trouble-free operation of the gyrotron. The functional structure of the setup corresponds to the general design method for feedback-controlled microwave sources. The feedback loop consists of a power meter (or a detector unit, to the user’s choice), a control system, and an anode HVPS, the regulated voltage of which controls the output power of the gyrotron. The feedback characteristic time is less than 1 s. Feedback control is provided for both CW and pulse modes. The setup includes a unique quasi-optical line that transmits the microwave beam through a 2-m air gap, as well as a synthesized mode converter from the Gaussian beam to the TE01 or TE11 mode (to the user’s choice) installed on a 300-kV platform. During the tests, the developed setup proved to be a reliable and user-friendly tool applicable for long-term powering of the fourth-generation ECR ion sources.

Control System for Superconducting Electron Cyclotron Resonance Ion Source with Advanced Design in Lanzhou II

The newly built SECRAL II (Superconducting Electron Cyclotron Resonance ion source with Advanced design in Lanzhou II) is a multi-purpose intense highly charged ion source and is of great significance at Institute of Modern Physics (IMP). The control system is an important subsystem of SECRAL II. In this paper, we implement a control system for SECRAL II. In order to achieve high quality control, we have presented and followed some useful control concepts. The control system can perform control and monitor of all devices. Besides, it can also complete data store, alarms, interlocks and human safety. In all, the control system effectively supports the operation for SECRAL II. The control system was completed and put into operation in June 2016. The control system has successfully worked for about 11000 hours. During this process, the hardware works normally and without trouble. The control software has a low failure rate (5.5×10-4/hour) and its MTTR (Mean Time to Repair) is less than 30 minutes. Since then, SECRAL II has set many world records in the field of ECR ion source.

Lattice design and beam dynamics simulation for the simultaneous operation of stable ion beam and rare isotope beam in the RAON accelerator

The Rare Isotope Accelerator of Newness (RAON) accelerator is under construction to generate and accelerate the stable ion beams and the rare isotope beams for various kinds of experiment programs. Especially, the post accelerator section was designed to be able to separately accelerate and transport the stable ion beams created by the superconducting electron cyclotron resonance ion source (ECR-IS) and the rare isotope beams created by the Isotope Separation On-Line (ISOL) system. However, recently, the research of the simultaneous operation of the stable ion beams and the rare isotope beams has been conducted to more efficiently satisfy the a wide range of beam requirements of the experimental halls. For the operation, we has modified the lattice of the post low energy beam transport (LEBT) section for the injection of the rare isotope beam and the next lattice after the low energy superconducting linac (SCL3) section for the extraction of the accelerated beam in the post accelerator section of the RAON accelerator. In this paper, the new lattice designs of the injection and extraction parts will be presented and we will describe the results of the beam dynamics simulations for the simultaneous operation of the two kinds of beams.

Intense highly charged ion beam production and operation with a superconducting electron cyclotron resonance ion source

Author(s): Zhao, HW; Sun, LT; Guo, JW; Lu, W; Xie, DZ; Hitz, D; Zhang, XZ; Yang, Y | Abstract: The superconducting electron cyclotron resonance ion source with advanced design in Lanzhou (SECRAL) is a superconducting-magnet-based electron cyclotron resonance ion source (ECRIS) for the production of intense highly charged heavy ion beams. It is one of the best performing ECRISs worldwide and the first superconducting ECRIS built with an innovative magnet to generate a high strength minimum-B field for operation with heating microwaves up to 24-28 GHz. Since its commissioning in 2005, SECRAL has so far produced a good number of continuous wave intensity records of highly charged ion beams, in which recently the beam intensities of Ar4012+ and Xe12926+ have, for the first time, exceeded 1 emA produced by an ion source. Routine operations commenced in 2007 with the Heavy Ion accelerator Research Facility in Lanzhou (HIRFL), China. Up to June 2017, SECRAL has been providing more than 28,000 hours of highly charged heavy ion beams to the accelerator demonstrating its great capability and reliability. The great achievement of SECRAL is accumulation of numerous technical advancements, such as an innovative magnetic system and an efficient double-frequency (24+18 GHz) heating with improved plasma stability. This article reviews the development of SECRAL and production of intense highly charged ion beams by SECRAL focusing on its unique magnet design, source commissioning, performance studies and enhancements, beam quality and long-term operation. SECRAL development and its performance studies representatively reflect the achievements and status of the present ECR ion source, as well as the ECRIS impacts on HIRFL.

Upgraded control system designed for SECRAL

To improve the accuracy and usability of the superconducting electron cyclotron resonance ion source with advanced design in Lanzhou (SECRAL), an upgraded version of the control system was designed and tested. This paper details the architecture of the optimized control system and presents the results of its use in the long-term operation of the accelerator. The control system software, based on Visual C++, was developed following the model-view-controller architecture design pattern. The data acquisition system was based on a field-programmable gate array integrated circuit. In addition, control strategies were optimized for higher operational stability. The upgraded control system was tested with a U33+ ion beam at SECRAL, where it provided a data acquisition time of less than 1 ms. The fast reaction time and high-precision data processing during beam tuning verified the stability and maintainability of the control system.

Designing of the low energy beam lines with achromatic condition in the RAON accelerator

The RAON accelerator has been built to create and accelerate stable heavy-ion beams and rare isotope beams. The stable heavy-ion beams are generated by the superconducting electron cyclotron resonance ion source and accelerated by the low energy superconducting linac SCL1. The beams accelerated by the SCL1 are re-accelerated by the high energy superconducting linac SCL2 for the generation of rare isotope beams by using the in-flight fragmentation system or are put to use in the low energy experimental halls, which include the neutron science facility and the KOrea Broad acceptance Recoil spectrometer and Apparatus after having passed through the low energy beam lines which have long deflecting sections. At the end of each beam line in the low energy experimental halls, the beams should meet the targets of the two facilities with the specific requirements satisfied. Namely, if the beam is to be sent safely and accurately to the targets and simultaneously, satisfy the requirements, an achromatic lattice design needs to be applied in each beam line. In this paper, we will present the lattice design of the low energy beam lines and describe the results of the beam dynamics simulations. In addition, the correction of the beam orbit, which is distorted by machine imperfections, will be discussed.

Mechanical Analysis and Measurements of a Multicomponent NbTi/Cu Superconducting Magnets Structure for the Fully Superconducting Electron Cyclotron Resonance Ion Source**Supported by the National Natural Science Foundation of China under Grant No 11302225, and the China Postdoctoral Science Foundation under Grant Nos 2014M560820 and 2015T81071.

A fully superconducting electron cyclotron resonance (ECR) ion source (SECRAL II) is currently being built in the Institute of Modern Physics, Chinese Academy of Sciences. Its key components are three superconducting solenoids (Nb-Ti/Cu) and six superconducting sextupoles (Nb-Ti/Cu). Different from the conventional superconducting ECR magnetic structure, the SECRAL II includes three superconducting solenoid coils that are located inside the superconducting sextupoles. The SECRAL II can significantly reduce the interaction forces between the sextupole and the solenoids, and the magnets can also be more compact in size. For this multi-component SECRAL II generating its self field of ~8 T and being often exposed to the high self field, the mechanical analysis has become the main issue to keep their stress at < 200 MPa on coils. The analytical and experimental results in mechanics are presented in the SECRAL II structure. To improve the accuracy and efficiency of analysis, according to the composite rule of micromechanics, the equivalent uniform windings are used to simulate the epoxy-impregnated Nb-Ti/Cu coils. In addition, using low temperature strain gauges and a wireless fast strain acquisition system, a fundamental experiment on the strains developments of a sextupole is reported. Finally, based on our analysis, the stresses and deformations for its assembly of each SECRAL II coil will be further optimized.

New development of laser ion source for highly charged ion beam production at Institute of Modern Physics (invited)

A laser ion source based on Nd:YAG laser has been being studied at the Institute of Modern Physics for the production of high intensity high charge state heavy ion beams in the past ten years, for possible applications both in a future accelerator complex and in heavy ion cancer therapy facilities. Based on the previous results for the production of multiple-charged ions from a wide range of heavy elements with a 3 J/8 ns Nd:YAG laser [Zhao et al., Rev. Sci. Instrum. 85, 02B910 (2014)], higher laser energy and intensity in the focal spot are necessary for the production of highly charged ions from the elements heavier than aluminum. Therefore, the laser ion source was upgraded with a new Nd:YAG laser, the maximum energy of which is 8 J and the pulse duration can be adjusted from 8 to 18 ns. Since then, the charge state distributions of ions from various elements generated by the 8 J Nd:YAG laser were investigated for different experimental conditions, such as laser energy, pulse duration, power density in the focal spot, and incidence angle. It was shown that the incidence angle is one of the most important parameters for the production of highly charged ions. The capability of producing highly charged ions from the elements lighter than silver was demonstrated with the incidence angle of 10° and laser power density of 8 × 10(13) W cm(-2) in the focal spot, which makes a laser ion source complementary to the superconducting electron cyclotron resonance ion source for the future accelerator complex especially in terms of the ion beam production from some refractory elements. Nevertheless, great efforts with regard to the extraction of intense ion beams, modification of the ion beam pulse duration, and reliability of the ion source still need to be made for practical applications.