Rare Isotope Accelerator Research Articles

Simple and Scalable Streaming: The GRETA Data Pipeline

The Gamma Ray Energy Tracking Array (GRETA) is a state of the art gamma-ray spectrometer being built at Lawrence Berkeley National Laboratory to be first sited at the Facility for Rare Isotope Beams (FRIB) at Michigan State University. A key design requirement for the spectrometer is to perform gamma-ray tracking in near real time. To meet this requirement we have used an inline, streaming approach to signal processing in the GRETA data acquisition system, using a GPU-equipped computing cluster. The data stream will reach 480 thousand events per second at an aggregate data rate of 4 gigabytes per second at full design capacity. We have been able to simplify the architecture of the streaming system greatly by interfacing the FPGA-based detector electronics with the computing cluster using standard network technology. A set of highperformance software components to implement queuing, flow control, event processing and event building have been developed, all in a streaming environment which matches detector performance. Prototypes of all high-performance components have been completed and meet design specifications.

Heavy ion beam physics at Facility for Rare Isotope Beams

The Facility for Rare Isotope Beams (FRIB) will be the world's premier rare-isotope beam facility. Experiments with the majority (∼80%) of the isotope predicted to exist will become available. The FRIB facility is based on a superconducting (SC) heavy ion linac with output energy above 200 MeV/u for any ions at beam power of 400 kW. FRIB includes a target facility for in-flight production of rare isotopes. A three-stage fragment separator will be used to prepare fast rare isotope beams with high-purity for nuclear physics experiments. The installation work of the accelerator and experimental systems is approaching completion and multi-stage beam commissioning activities started in summer 2017 with expected project completion in early 2022. The commencement of operation for users' experiments is planned immediately following the project completion.

RF deflecting cavity for fast radioactive ion beams

The Facility for Rare Isotope Beams (FRIB) will be a new scientific user facility that produces rare-isotope beams for experiments from the fragmentation of heavy ions at energies of 100–200 MeV/u. During the projectile fragmentation, the rare isotope of interest is produced along with many contaminants that need to be removed before the beam reaches detectors. At FRIB, this is accomplished with a magnetic projectile fragment separator. However, to achieve higher beam purity, in particular for proton-rich rare isotopes, additional purification is necessary. RadiaBeam in collaboration with Michigan State University (MSU) has designed a 20.125 MHz radiofrequency (RF) fragment separator capable of producing a 4 MV kick with 18 cm aperture in order to remove contaminant isotopes based on their time of flight. In this paper, we will discuss the RF and engineering design considerations of this separator cavity.

RIB studies for explosive scenarios and future opportunities at FRIB

An accreting compact star in a binary system can generate periodic thermonuclear runaways on its surface. In the case of a white dwarf star, the result is a classical nova, which enriches the interstellar medium with newly synthesized nuclides. In the case of a neutron star, a detectable burst of X-rays is emitted. Nucleosynthesis and energy generation in these events depends on resonant thermonuclear reaction rates, which are especially challenging to measure directly in the laboratory when they involve radioactive reactants. Fortunately, the resonances can be discovered and their relevant properties can be constructed using nuclear structure experiments. We will describe a program of beta decay experiments the National Superconducting Cyclotron Laboratory to this end. In particular, the Gaseous Detector with Germanium Tagging (GADGET) system, developed to measure very weak low-energy beta delayed proton emission branches and gamma rays, is now operational. Recent results and future opportunities at the Facility for Rare Isotope Beams will be discussed.

Beam dynamics simulation and beam commissioning preparation in the RAON accelerator

The RAON (Rare Isotope Accelerator complex for ON-line experiments) accelerator that can accelerate various kinds of beams from proton to uranium using superconducting radio-frequency (RF) cavities is currently under construction with the goal of completion in 2021 by the Rare Isotope Science Project in Daejeon, Korea. At Sindong site in Daejeon, the accelerator equipment of the low energy linac section consisting of the quarter-wave resonator (QWR) and half-wave resonator (HWR) cavities is being installed in 2020, and the installation of accelerator equipment including single-spoke resonators (SSR1 and SSR2) cavities in the high energy linac section will be completed by the end of 2021. According to the installation schedule, we are preparing the beam commissioning to verify the performance of the accelerator equipment and to achieve the desired beam parameters. For the successful beam commissioning, several physics application tools to be used at the beam commissioning are being developed, and the beam dynamics studies have been also continued. Here we will present ongoing beam dynamics studies and beam commissioning scenarios under planning. In addition, we will introduce the application tools being developed for successful beam commissioning in the RAON accelerator.

Mapping the frontiers of the nuclear mass surface

Nuclear masses play a central role in nuclear astrophysics, significantly impacting the origin of the elements and observables used to constrain ultradense matter. A variety of techniques are available to meet this need, varying in their emphasis on precision and reach from stability. Here I briefly summarize the status of and near-future for the time-of-flight magnetic-rigidity (TOF-Bρ) mass measurement technique, emphasizing the complementary and interconnectedness with higher-precision mass measurement methods. This includes of recent examples from TOF-Bρ mass measurements that map the evolution of nuclear structure across the nuclear landscape and significantly impact the results and interpretation of astrophysical model calculations. I also forecast expected expansion in the known nuclear mass surface from future measurement at the Facility for Rare Isotope Beams.

Commissioning Status of the Linac for the Facility for Rare Isotope Beams

The Facility for Rare Isotope Beams will be completed in late 2021. We report here on the current efforts to commission the first stages of the 200-MeV/u superconducting, continuous wave heavy-ion linac. The statuses of the cryogenic plant and its distribution system, the accelerator cryomodule commissioning and operations, the ion source and front end transport development, the radio-frequency quadrupole commissioning, and thenbeam dynamics development to support high-power operation are reviewed. Plans for commissioning the remainder of the linac systems are presented.

Constraints on the neutron drip line with the newly observed Na39

The recently observed weakly-bound 39Na provides a stringent theoretical constraint on the neutron drip-line. We studied the properties of drip-line nuclei around 39Na with the Hartree-Fock-Bogoliubov method and various Skyrme interactions. We adopted the extended SkM*-ext1 parameterization which can properly describe two-neutron separation energies of oxygen and fluorine isotopes and deformations at the center of the "island of inversion". Systematic calculations of drip lines of O, F, Ne, Na, Mg, and Al isotopes have been performed. We infer that 42Mg is weakly bound and 45Al is less weakly bound. 44Mg and 47Al could be barely existed. We also demonstrated the deformed halo properties of 39Na. Our studies could be valuable for experimental explorations of drip-line nuclei in the forthcoming FRIB and other rare-isotope beam facilities .

Timing System Development for RAON Operation

The Rare Isotope Accelerator complex for ON-line experiments (RAON) is a heavy-ion accelerator experiment facility under construction in Korea. This facility aims at a beam energy of 200 MeV/u and a maximum beam power of 400 kW and is expected to be completed by 2021. A large-scaled experiment facility like RAON requires a timing system for precise-synchronized operation. For this purpose, domestic accelerator facilities mainly use timing systems that are foreign products. The accelerator engineering team of RAON has successfully developed the RAON timing system in cooperation with a domestic company. The signals from the RAON timing system synchronized with an radio frequency (RF) reference clock and a global positioning system (GPS) are distributed throughout the RAON site via the dedicated timing network (3.25 Gbps). The time accuracy of the timing system is 12.3 ns synchronized with the RF reference clock (81.25 MHz). All signals (triggers, pulse delayed clock, and external signals) of the timing system developed using the Experimental Physics and Industrial Control System (EPICS) software module are configurable on a software. In addition, the RAON timing system supports the more flexible system for the various beam operation mode and improves the performance of the control system. This paper describes the results of the design and development of the RAON specific timing system.

SRF Test Facility Signal Archiving System for the RAON

The Rare Isotope Science Project (RISP) of the Institute for Basic Science (IBS) has been developing a heavy-ion accelerator, called the Rare isotope Accelerator complex for ON-line experiments (RAON). For accelerator operation, The RISP control system adopts the Experimental Physics and Industrial Control System (EPICS) to control and monitor all accelerator software and hardware [1]. The signal archiving system is a core system for accelerator operation, and research for improving reliability and integrity is important. Signal archiver method using the EPICS framework has three significant modes of operation. First is the classic channel archiver using the file base method, and the second is the Relational DataBase (RDB) archiver using a relational database. But classic channel archiver has the problem that the index file contains information on a data block corresponding to PV data mismatch with real data. Also, the RDB archiver has a problem in the performance of file I/O. The RAON control group has built a signal archiving system using an archive appliance that solves the current problems from several archiving methods. This paper describes the result of the Superconducting Radio Frequency (SRF) archiving system based on the archiver appliance.

Evolution of shell structure in exotic nuclei

The next generation of rare-isotope beam facilities will enable access to key regions of the nuclear chart, where the measured properties of short-lived isotopes will challenge our current theoretical picture and help develop a comprehensive model of the atomic nucleus. This article reviews the mechanisms driving the evolution of shell structure in exotic nuclei that impact nuclear physics and nuclear astrophysics research.

Diversifying beam species through decay and recapture ion trapping: a demonstrative experiment at TITAN-EBIT

Recapturing the recoiling daughters from radioactive decay can be a simple way to diversify beam availability at rare isotope beam facilities. In the decay and recapture ion trapping (DRIT) technique, a parent species is stored in an ion trap and left to decay, and the daughter ions are recaptured by the trap and become available for use. We successfully demonstrated the technique using the electron beam ion trap (EBIT) at the TITAN facility. A pure cloud of 30Mg ions was stored in the EBIT for about one half-life and sent to a Penning trap mass spectrometer, which confirmed the production of 30Al daughter ions. Systematic measurements and simulations suggest high recapture efficiencies of the recoil ion and little influence of the recoiling energy in the observed losses. With the secondary beam, we also performed precision mass measurements of the parent 30Mg8+ and the daughter 30Al11+ ions. Our results agree with the literature and improve its precision. The success of this experiment shows that EBITs can produce high-quality beams through the DRIT technique.

FRIB cryogenic system status

The Facility for Rare Isotope Beams (FRIB) cryogenic plant has been successfully commissioned, including compressor system, 4.5 K cold box system, sub-atmospheric (2 K) cold box system, and the distribution system for two of the three linear accelerator (Linacs) segments. This plant uses the Ganni-Floating pressure process, allowing the compressor discharge and 4.5 K cold box supply pressure to automatically vary from 6 to 21 bar, without introducing additional exergetic losses to reduce the capacity (e.g., throttling turbine inlet valves, load heaters, etc.). The 2 K (31 mbar) load is supported using five stages of centrifugal compressors, housed within the sub-atmospheric cold box, which recompress the helium to 1.15 bar (and around 30 K). In 2012, FRIB assumed the responsibility, in collaboration with JLab to design and procure the sub-systems after the decision to move away from an industry supplied turn-key system. FRIB was responsible for procurement of all systems, all onsite activities, including the installation and integration of all the subsystems, development of the control systems, as well as, the integration, commissioning, and testing of each sub-system. At present this has culminated in the production of the first beam through the first Linac segment. An overview of the planning and execution of the project will be presented, which allowed meeting of scheduled goals and anticipated performance, and prevented the need to store or ‘double-handle’ any equipment.

Cryogenic design of FRIB cryomodule and distribution system and the present status

The Michigan State University (MSU) Facility for Rare Isotope Beams (FRIB) accelerator utilizes six types of cryo-modules that are being installed in three Linac segments in the FRIB tunnel. The cryomodules contain both superconducting RF cavities and solenoid magnets with 2 K and 4.5 K refrigeration loads (respectively), magnet lead flow loads and 35-55 K shield loads and power coupler intercept loads. The first Linac segment (LS-1) with fifteen cryomodules was commissioned at 4.5 K and at 2 K. Commissioning experiences and some salient features of the cryogenic design of the cryomodules and the helium distribution systems will be discussed.

Preface

The 2019 Joint Cryogenic Engineering and International Cryogenic Materials Conferences were held from July 21 through July 25 at the Connecticut Convention Center in Hartford, Connecticut. As at past conferences, the international scope of these meetings was strongly maintained with 24 countries being represented by 613 attendees who gathered to enjoy the joint technical programs, industrial exhibits, and special events.The program for the joint conferences included a total of 410 presentations in the plenary, oral, and poster sessions. Four plenary talks gave interesting in-depth overviews and discussions on the topics of the growing field of commercial application of hydrogen fuel-cells for specialized applications and large-scale semi-truck transportation, and recent 5x increase of liquid hydrogen production in the U.S.; Siemens’ perspectives on evolving hybrid-electric propulsion technologies for large commercial aircraft; the world-leading research opportunities with rare isotopes in nuclear physics, nuclear chemistry, and the application of rare isotopes for society that the Facility for Rare Isotope Beams (FIRB) at Michigan State University will soon provide; and the impressive progress designing the next-gen SPARC fusion reactor 1st-ever utilizing 2nd-generation high-temperature-superconducting (HTS) wire. The attendees also convened for two Special Joint CEC-ICMC Symposia on i) Transportation, and ii) Quantum Computing, and seven Special-or-Focus Sessions were included in the programming emphasizing high-quality invited talks. Contributed papers covered a wide range of topics including many aspects in advances in cryogenics and superconductors, along with their applications. Both CEC and ICMC boards are encouraging student participation and career growth and provided registration support for 36 student applicants. In total, 207 papers were submitted for publication of which 190 are published in these conference proceedings.Full Preface information is available in the pdf.

FRIB helium refrigeration system commissioning and performance test results

At its maximum capacity condition, the 4.5 K refrigerator system for the Facility for Rare Isotope Beams (FRIB) accelerator supports a 180 g/s 30 K 1.16 bar cold compressor return flow, a 14 g/s 4.5 K liquefaction load, a 4 kW 4.5 K refrigeration load, and a 20 kW 35-55 K shield load. Five additional design conditions, ranging from liquefaction to refrigeration and a stand-by/reduced load state, were specified for the sizing and selection of its components. The cold box system is comprised of a 300-60 K vertical cold box that incorporates a liquid nitrogen pre-cooler and a 60-4.5 K horizontal cold box housing seven turbines that are configured in four expansion stages including one Joule-Thompson expander. This cold box system, operates using the Ganni-Floating pressure process, automatically adjusting to the linear accelerator (Linac) load with the cold box supply (and compressor discharge) pressure varying from 6 to 21 bar, without introducing additional (artificial) loads or throttling turbine inlet valves (or other exergy loss mechanisms), and with minimal liquid nitrogen usage. This paper will briefly review the salient 4.5 K system design features and discuss the recent commissioning results.

FRIB cryogenic control system

The cryogenic system at the Facility for Rare Isotope Beams (FRIB) supports loads for 2 K refrigeration, 4.5 K refrigeration and liquefaction, and a 35-55 K thermal shield for the linear accelerator consisting of 46 cryomodules, 4 superconducting dipoles and 14 superconducting magnets for the experimental system. The controls system for cryogenics was designed, installed, and commissioned with the goal of high availability, ease of maintenance, and simplicity of operation. The personnel protection system (PPS) is a separate system which monitors for oxygen deficiency hazards (ODH) throughout the cryo-plant and around the cryogenic loads. The system consists of Allen-Bradley programmable logic controllers (PLCs) with local human machine interfaces (HMIs) along with the Experimental Physics and Industrial Controls System (EPICS) for normal operations and data acquisition. Two separate networks are utilized in the cryogenic facility. One is a network cluster that houses EPICS. It is designed with high redundancy and is completely separate from the network used for the rest of the particle accelerator. The second network only includes PLCs and HMIs for faster data transfer between PLCs, increased flexibility for changing operating conditions, and complete system operation in the case of an EPICS network failure. This paper reports on the design choices selected and experiences in integrating and commissioning the FRIB cryogenic control system.

Preface

The 2019 Joint Cryogenic Engineering and International Cryogenic Materials Conferences were held from July 21 through July 25 at the Connecticut Convention Center in Hartford, Connecticut. As at past conferences, the international scope of these meetings was strongly maintained with 24 countries being represented by 613 attendees who gathered to enjoy the joint technical programs, industrial exhibits, and special events.The program for the joint conferences included a total of 410 presentations in the plenary, oral, and poster sessions. Four plenary talks gave interesting in-depth overviews and discussions on the topics of the growing field of commercial application of hydrogen fuel-cells for specialized applications and large-scale semi-truck transportation, and recent 5x increase of liquid hydrogen production in the U.S.; Siemens’ perspectives on evolving hybrid-electric propulsion technologies for large commercial aircraft; the world-leading research opportunities with rare isotopes in nuclear physics, nuclear chemistry, and the application of rare isotopes for society that the Facility for Rare Isotope Beams (FIRB) at Michigan State University will soon provide; and the impressive progress designing the nextgen SPARC fusion reactor 1st-ever utilizing 2nd-generation high-temperature-superconducting (HTS) wire. The attendees also convened for two Special Joint CEC-ICMC Symposia on i) Transportation, and ii) Quantum Computing, and seven Special-or-Focus Sessions were included in the programming emphasizing high-quality invited talks. Contributed papers covered a wide range of topics including many aspects in advances in cryogenics and superconductors, along with their applications. Both CEC and ICMC boards are encouraging student participation and career growth and provided registration support for 36 student applicants. In total, 207 papers were submitted for publication of which 190 are published in these conference proceedings.Full Preface information is available in the pdf.

An isotope harvesting beam blocker for the National Superconducting Cyclotron Laboratory

Harvesting isotopes from beam stops and other activated materials at accelerator facilities is a promising source of environmentally, scientifically and socially important radionuclides. At the Facility for Rare Isotope Beams (FRIB), a multitude of short- and long-lived radionuclides will be collected in a synergistic manner by dumping unused beams into a flowing-water beam stop. Ongoing exploratory research at the National Superconducting Cyclotron Laboratory (NSCL) with an analogous beam blocker aims towards obtaining the necessary radiochemical expertise for this endeavor.Herein we present a beam blocker and an isotope harvesting system which allows collection of a wide variety of aqueous and gaseous radionuclides. The water which flows through the beam blocker functions as an isotope production target and concurrently transports the newly formed radionuclides to collection sites. The system includes analytical instruments for online measurements of conductivity, dissolved oxygen, temperature, pressure and for detection of radiolytic products. To limit the levels of radiolytically produced hydrogen peroxide, a stainless-steel based degradation system was designed and implemented. The suitability of the constructed system for the anticipated radionuclide harvesting project was demonstrated by offline tests and under irradiation with 140 MeV/u 48Ca20＋ ions at the NSCL Coupled Cyclotron Facility.

Radiolysis and radionuclide production in a flowing-water target during fast 40Ca20+ irradiation.

A flowing-water target was irradiated with a 140 MeV/u, 8 nA 40Ca20+ beam to test the feasibility of isotope harvesting at the upcoming Facility for Rare Isotope Beams. Among other radionuclides, 2.6(2)E-6 48Cr and 5.6(5)E-6 28 Mg nuclei were formed for every impingent 40Ca and were collected through ion exchange. Radiolysis-induced molecular hydrogen evolved from the target at an initial rate of 0.91(9) H2 molecules per 100 eV of beam energy deposited. No radiation-accelerated corrosion of the target material was observed.