Intense Heavy Ion Beams Research Articles

Sputtering of targets in high-intensity heavy-ion beam experiments

Based on available models and experimental data, the sputtering of target atoms in long-term experiments with intense heavy ion (HI) beams has been considered. The experiments on the synthesis of superheavy nuclei (SHN), which are carried out in laboratories around the world, are examples of such experiments encountering the target atoms sputtering in specific conditions. Rotating wheels with a relatively large target annulus area are used in these experiments to reduce the temperature and radiation loads on the target. Large areas of rotating targets allow one to reduce the sputtering yields of target atoms significantly. The question arises about the reliability of these yields in experiments on the synthesis of SHN with Z>118. These nuclei can be produced with extremely low cross sections, requiring HI beam doses exceeding 10 20 particles passed through the target to observe several decay events of the thus synthesized SHN. Estimates based on approximations and simulations considered in this work are presented and compared with some data on actinide target sputtering obtained in experiments performed on the synthesis of SHN.

Diamond ∆E-E telescope with an ultra-thin ∆E-diamond detector

The limits of mechanical polishing and RIE/ICP etching process were investigated to reduce the thickness of detector-grade ultra-thin below 10 μm, preserving the high quality of starting single crystal diamond (SCD) material. Free standing electronic grade SCD films with sizes up 4.5 × 4.5 mm2 and thickness down to 5 μm with overall thickness uniformity of ±0.35 μm were fabricated. The ultra-thin films were flat demonstrating the low internal stress.Diamond ∆E − E telescope was made from 5 μm thick ΔE-detector and 500 μm thick E-detector. The telescope was installed at the MARS spectrometer (Cyclotron Institute, TAMU) and tested with 241Am and 228Th alpha sources and 20Ne ion-beam, demonstrating the good spectral resolution around 100 keV. Simulations with the LISE++ program indicate that the telescope will be suitable to measure low energy heavy ion beams at energies as low as 2–3 MeV/nu for Au and U heavy ions, and even lower energies for lighter ions. The diamond telescope will be superior to common Si radiation telescopes having a low life-time in intense heavy ion-beams.

Actinide targets for the synthesis of superheavy nuclei

The use of heavy actinide targets, including 243Am, 240,242,244Pu, 245,248Cm, 249Bk, and 249Cf, irradiated by intense heavy ion beams of 48Ca has resulted in a significant expansion of the periodic table since 2000, including the discovery of five new heaviest elements and more than 50 new isotopes. These actinide materials can only be produced by intense neutron irradiation in very high flux reactors followed by chemical processing and purification in specialized hot cell facilities available in only a few locations worldwide. This paper reviews the reactor production of heavy actinides, the recovery and chemical separation of actinide materials, and the preparation of actinide targets for superheavy element experiments. The focus is on 248Cm, 249Bk, mixed 249−251Cf, and 254Es, including current availabilities and new production processes. The impacts of new facilities, including the Superheavy Element Factory at Dubna, accelerator and separator upgrades at RIKEN, and proposed upgrades to the High Flux Isotope Reactor at Oak Ridge are also described. Examples of recent superheavy element research are discussed as well as future opportunities for superheavy research using actinide targets.

Status update of the Charge Stripper Rings project

The RIKEN RI (radioactive isotope) Beam Factory (RIBF) provides the world's most intense heavy ion beams exceeding 345 MeV/u and is the primary facility for in-flight RI beam generation. The RIBF has steadily improved its performance. In particular, the intensity of the uranium beam, which is critical for producing in-flight fission RI beams, has been dramatically increased by a factor of 240 compared to 2008. To further increase the intensity of the uranium beam, a new acceleration scheme using charge stripper rings (CSRs) has been proposed as a cost-effective way to increase charge stripping efficiency. In this paper, we discuss the key design issues of CSR and required upgrades of existing ring cyclotrons with the introduction of CSR and space-charge effects.

Production of diamond using intense heavy ion beams at the FAIR facility and application to planetary physics

Diamonds are supposedly abundantly present in different objects in the Universe including meteorites, carbon-rich stars as well as carbon-rich extrasolar planets. Moreover, the prediction that in deep layers of Uranus and Neptune, methane may undergo a process of phase separation into diamond and hydrogen, has been experimentally verified. In particular, high power lasers have been used to study this problem. It is therefore important from the point of view of astrophysics and planetary physics, to further study the production processes of diamond in the laboratory. In the present paper, we present numerical simulations of implosion of a solid carbon sample using an intense uranium beam that is to be delivered by the heavy ion synchrotron, SIS100, that is under construction at the Facility for Antiprotons and Ion Research (FAIR), at Darmstadt. These calculations show that using our proposed experimental scheme, one can generate the extreme pressure and temperature conditions, necessary to produce diamonds of mm3 dimensions.

Experimental setup for interaction between highly charged ions and laser-produced plasma near Bohr velocity energy region

Ion energy loss in the interaction between highly charged ions and dense plasma near Bohr velocity energy region is one of the important physical problems in the field of high-energy density physics driven by intense heavy ion beams. Based on the 320 kV experimental platform at the Institute of Modern Physics, Chinese Academy of Sciences, a new experimental setup was built for the research of interaction between ions and laser-produced plasma near the Bohr velocity, where the ion energy loss and charge state distribution can be experimentally investigated. In this paper we introduce the new setup in detail, including the generation and controlling of pulsed ion beam ( ≥ 200 ns); the preparation of high-density laser plasma target (10<sup>17</sup>—10<sup>21</sup> cm<sup>–3</sup>); the diagnostics of plasma and the developed high energy resolution ion measurement system (< 1%). In the experiment, the charge distribution of Xe<sup>15+</sup> ions with 4 MeV penetrating through the laser-produced Al plasma target is measured. The charge-state analysis device observes different results without and with the plasma, in which the outgoing Xe ion charge-state changes correspondingly from the 15+ to 10+, thus the electron capture process is believed to be dominant. In addition, the proton energy loss is also measured by using the magnetic spectrometer, showing that the experimental energy loss is about 2.0 keV, 30% higher than those theoretical predictions , which can be attributed to the fact that in the near Bohr velocity energy regime, the first-order Born approximation condition is not valid, thus the Bethe model and SSM model are inapplicable to the experimental results. In future, a systematic study will be performed based on our ions-plasma ineteraction setup, and the energy loss and charge state data will be introduced.

Target polarization effect on energy loss of O<sup>5+</sup> ions near Bohr velocity in low density hydrogen plasma

Energy loss of ions near the Bohr velocity in plasma is one of the important topics in intense heavy ion beam driven high energy density physics and inertial confinement fusion. Based on the ions-plasma interaction experimental platform at HIRFL, this work shows the new experimental energy loss results of 1.07 MeV (~66.9 keV/u) O<sup>5+</sup> ions penetrating through a low-density partially ionized hydrogen plasma target (radio frequency plasma). The decrease of energy loss with free electron density increasing is found, which is very different from our previous result. The new experimental results are discussed by considering the theoretical models which involves the charge screening of projectiles in the partially ionized plasma and the target polarization effect-Barkas correction term. For the charge screening , the comparison between the momentum transfer under the Coulomb potential and that under the Debye potential is given, but due to the low ionization degree, the plasma screening effect seems not to be the main reason for the decrease of energy loss. For the target polarization effect , in the Bohr velocity regime, the Barkas correction term can play a key role in the ion-atom collisions. Modeling the Barkas correction term based on the proposed classical energy loss formula, the experimental data of ions in the gas target can be well fitted by the calculated values. In the partially ionized plasma, the frequent thermal electron collisions can give rise to the atomic excitation of plasma target, correspondingly the Barkas correction term changes: it decreases with the fraction of excited atoms increasing. As a result, the energy loss decreases in our experiment. In the stopping of highly charged ions in a partially ionized low-density plasma, the collisions between ions and free electrons can produce an enhanced energy loss according to previous studies. However, the target polarization effect, especially the atomic excitations, can significantly reduce the energy loss, which is observed in our experiment. Therefore, the interaction between ions and partially ionized plasma should be further studied, and the Barkas correction can be a very important term.

Advancements in the fabrication and characterization of actinide targets for superheavy element production

The heaviest elements can exclusively be produced in actinide-target based nuclear fusion reactions with intense heavy-ion beams. Ever more powerful accelerators deliver beams of continuously increasing intensity, which brings targets of current technology to their limits and beyond. We motivate efforts to produce targets with improved properties, which calls for a better understanding of targets produced by molecular plating, the current standard method. Complementary analytical methods will help shedding more light on their chemical and physical changes in the beam. Special emphasis is devoted to the aspect of the optimum target thickness and the choice of the backing material.

Design aspects of the feed boxes of the Super-FRS Local Cryogenics System

The Super-FRS is an electromagnetic separator and spectrometer designed for the production and selection of highly energetic and intense exotic heavy-ion beams. It is part of the Facility for Antiproton and Ion Research (FAIR) particle accelerator currently under construction at GSI, Darmstadt, Germany. The Super-FRS will feature in total 63 superconducting magnet cryostats: 27 dipoles, 35 multiplets (7 short and 28 long), and the GLAD experiment magnet. The Super-FRS Local Cryogenics will distribute and feed cold helium from the central cryogenic plant “CRYO2” to the magnet cryostats. Daisy-chain like arrays of feed and end boxes are connected via transfer line pieces. Each single magnet cryostat is supplied by one feed box via a jumper connection. The dipole, short- and long multiplets require different helium mass streams at different operation modes. Moreover, the Local Cryogenics system must follow the Super-FRS curvature and irregular pattern of cryostat locations. In order to simplify the production process, lower the risk of technical mistakes, and increase the flexibility of the installation sequence during the conceptual design project phase an effort was made to develop a uniform construction of the feed boxes for all cryostat types. The paper provides the description of the Super-FRS Local Cryogenics system and the process requirements for all cryostat types in all possible operation modes. The Super-FRS feed box flow scheme and features that allow for unification of its design for all cryostat types are also presented.

Optimization design and test of the Booster Ring dipole magnet in HIAF

The High-Intensity Heavy Ion Accelerator Facility (HIAF), proposed by the Institute of Modern Physics, Chinese Academy of Sciences (IMP), is being designed to provide primary and radioactive intense beams for nuclear and related research. As an important part of HIAF, the Booster Ring (BRing) is a fast ramping synchrotron and is used to obtain high intensity (238U35+, 1 × 1011 ppp) and high energy (0.835 GeV/u) heavy-ion beam. Moreover, the beam rigidity of the Booster Ring varies widely from 1 Tm to 34 Tm. These require the dipole of Booster Ring to have a large-good field region, a high magnetic field homogeneity, and a wide range of magnetic field variation from 0.047 T to 1.58 T. Aiming at the properties of the dipole magnet, we adopt some new methods to improve magnetic field precision and optimize efficiency. Double symmetrical air holes in the magnet pole are used to guarantee the magnetic field homogeneity under a wide magnetic field range. At the same time, the linear programming algorithm is adopted to optimize the integral magnetic field uniformity of the iron-dominated dipole magnet, which improves the integral magnetic field precision and optimization efficiency. So far, the prototype dipole magnet has been fabricated and tested. Through magnetic field optimization, measurement, and secondary trimming, the measurement results satisfy the physical requirements.

Chemical conversions in lead thin films induced by heavy-ion beams at Coulomb barrier energies

Superheavy elements are produced via fusion reactions, by bombarding thin target foils with intense beams of energetic ions with energies around the Coulomb barrier. Currently, production of targets of rare isotopes relies mainly on the molecular plating (MP) method, which yields thin films of the desired target material on a backing foil. Intense heavy-ion beams are known to modify the film structure, which leads to deterioration of the targets over irradiation time. To gain a better understanding of the processes at a microscopic scale, comparative tests were carried out using Coulomb barrier heavy-ion beams provided from the UNILAC accelerator at GSI Darmstadt, Germany. For this purpose, targets of lead were prepared using MP and Drop-on-Demand inkjet-printing. Lead targets were baked-in and analysed by digital optical microscopy, scanning electron microscopy and confocal Raman spectroscopy.

Effects of beam wobbling and target rotation on the target temperature in experiments with intense heavy ion beams

Effects of beam wobbling and target rotation on reducing target temperature are quantitatively considered with simulations and calculations. These manipulations with the beam and target reduce sharpness in the beam-density distribution, making it quasiuniform on the target surface. A uniform beam density is essential in prolonged experiments on the synthesis of superheavy nuclei using intense heavy-ion beams and actinide targets. The heavy-ion beam energy partially absorbed by the target and target backing heats them and transfers warmth to the surrounding by different means. The target temperature was initially considered for a stationary target using notions of heat transfer due to the thermal conductivity, radiation emission, and heat removal to dilute gas surrounding the target. The effects of the beam width, the amplitude of the wobbler, and the rotating target velocity on the beam-density distribution across the target surface and, consequently, on its temperature are further estimated with the same notions.

Using an RFQ to Transport Intense Heavy Ion Beams from an ECR Ion Source

Using an RFQ to Transport Intense Heavy Ion Beams from an ECR Ion Source

Progress of intense heavy ion beam driven high energy density physics

Intense ion beams can quasi-isometrically heat any high-density sample and generate warm dense matter (WDM) with large scale, uniform state distribution without any shock wave inside. This kind of driver provides a new opportunity for the laboratory high energy density physics (HEDP) research. The typical intense ion beam accelerators around the world, as well as their critical parameters and research plans of HEDP study are introduced.The progress of ion driven WDM generation and evolution using PIC and hydrodynamic simulations is shown. The high energy electron beam radiography technique with high spatial resolution, high temporal evolution, and high penetrating ability is also introduced. The collisional and charge transfer processes of the interaction between low-to-medium energy ion and plasma are analyzed. The nonlinear effect during the intense ion beam stopping and transportation process are presented.

LINAC developments for heavy ion operation at GSI and FAIR

The first cavity of a standalone superconducting (sc) continuous wave (cw) heavy ion Linac as a demonstration of the capability of 217 MHz multi gap Crossbar H-mode structures (CH) has been already commissioned at high acceleration gain. The worldwide first beam test with a superconducting multi gap CH-cavity was a milestone of the R&D work of HIM and GSI in collaboration with Goethe University Frankfurt (GUF) in preparation of the sc cw heavy ion Linac project, substituting GSI-UNILAC as a heavy ion high duty factor Linac. Recently the first two of four fully equipped cw-Linac cryomodules are in procurement. To meet the future FAIR science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. In the last years ion source developments, in particular for the high current Vacuum Arc Ion Sources (VARIS), were concentrated on heavy elements, as Bi and Pb, aiming for stable routine ion source operation at a sufficient rep. rate and high production efficiency. Stripping is a key technology for all heavy ion accelerators. After upgrade of the supersonic N2-gas jet implementation of high current foil stripping, recently a new H2gas cell, using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An enhanced stripper gas density as well as a simultaneously reduced gas load results in an increased stripping efficiency, while the beam emittance remains the same. A new record beam intensity (11.1 emA) for238U28+beams at 1.4 MeV/u has been achieved, applying the pulsed high density H2-stripper target to a high intensity238U4+beam from the VARIS ion source. Further ion source developments have been accomplished recently providing for sufficient heavy ion beam intensities at the High Current Injector Linac. A machine investigation program has been performed in 2020. The focus was to optimize the entire FAIR injector chain for high intensity heavy ion beam after the successful implementation of different upgrade measures. Besides a dedicated operation mode applying UNILAC, as a heavy ion Linac, at a synchronous phase significantly lower than 30 degrees for high intensity proton beam, could be established. Thus, UNILAC is able to deliver a sufficient proton beam intensity for the FAIR commissioning phase, when the FAIR-proton Linac is not yet available.

Research program of superheavy elements and nuclides based on HIAF

Atomic nuclei are many-body quantum systems composed of protons and neutrons. The nuclides, whose existence is attributed to the nuclear shell effects, are referred to as superheavy nuclides. The exploration of the limit to the existence of nuclides with regard to the proton and mass numbers is at the frontier of nuclear physics research. So far, superheavy elements with an atomic number of up to 118 and hundreds of superheavy nuclides have been experimentally synthesized and identified in various laboratories, resulting in the completion of the seventh period of the periodic table of elements. The High Intensity heavy-ion Accelerator Facility (HIAF) is now under construction and is scheduled to be commissioned in 2025. The study on superheavy elements and nuclei is one of the main research goals of HIAF. Intense heavy-ion beams can be extracted from around the middle point of linac, and the beam energies can be finely adjusted around the Coulomb barriers of nuclear reactions. Therefore, HIAF will provide great opportunities for the synthesis of new superheavy elements and to explore the superheavy island of stability, which was theoretically predicted long ago via fusion and multi-nucleon transfer reactions, respectively. This paper presents the research program of superheavy elements and nuclides based on HIAF, provides an overview of the research on superheavy nuclei, and describes the electromagnetic spectrometers and experimental measurement systems associated with fusion and multi-nucleon transfer reactions. The HIAF physics goals, including the synthesis of new superheavy elements and nuclides, the study on the nuclear structure of superheavy nuclei, the reaction mechanism of producing superheavy nuclides, and the atomic structure and chemical properties of the heaviest elements, are illustrated in detail. Lastly, the future research plan for superheavy elements and nuclides is summarized.

SAFIIRA: A heavy-ion multi-purpose irradiation facility in Brazil

This work describes the new facility for applied nuclear physics at the University of Sao Paulo, mainly for irradiation of electronic devices. It is a setup composed of a quadrupole doublet for beam focusing/defocusing plus multiple scattering through gold foils to produce low intensity, large-area, and high-uniformity heavy-ion beams from 1H to 107Ag. Beam intensities can be easily adjusted from 102 particles cm2/s to hundreds of nA for an area as large as 2.0 cm2 and uniformity better than 90%. Its irradiation chamber has a high-precision motorized stage, and the system is controlled by a LabViewTM environment, allowing measurement automation. Design considerations and examples of use are presented.

Modification of Ti foils irradiated by intense heavy ion beams

ABSTRACT Modification of Ti foils irradiated by intense energetic heavy ion (HI) beams in long-term experiments has been considered. The experiments on the synthesis of superheavy nuclei, which are carried out in Dubna with a gas-filled recoil separator (DGFRS), determine the conditions of such experiments. High intensities of HIs passing through a relatively small area and thickness of the foils, as well as their heating by a beam, are inherent in such experiments. The ability of the foils to withstand radiation damages, sputtering, and evaporation of atoms becomes questionable. All the processes seem to be dependent on temperature, and none of them is independent of the others, but they can be considered separately. In this work, sputtering yields are estimated on the grounds of available models and experimental data and compared with the results of measurements carried out to verify the estimates. The foil temperature, in turn, can be estimated in the conditions of pulse heating followed by subsequent cooling with radiation emitted from their surfaces. These conditions correspond to the rotating Ti entrance window irradiated by a continuous HI beam in the DGFRS experiments.

FAIR: The Future European Facility for Antiproton And Ion Research

FAIR, the new international Facility for Antiproton and Ion Research at GSI, will cover a broad spectrum of hadronic, nuclear, and atomic physics research and appli- cation. A system of synchrotrons will provide intense proton and heavy ion beams of intermediate energy with the option to produce secondary beams of radioactive nuclei and antiprotons. NUSTAR, NUclear STructure, Astrophysics and Reactions, will play a premier role within the FAIR research program. Nuclei at the limits of binding will become accessible and new probes for reaction studies with unstable nuclei become available.

Studies of equation of state properties of high-energy-density matter generated by intense ion beams at the facility for antiprotons and ion research.

The work presented in this paper shows with the help of two-dimensional hydrodynamic simulations that intense heavy-ion beams are a very efficient tool to induce high energy density (HED) states in solid matter. These simulations have been carried out using a computer code BIG2 that is based on a Godunov-type numerical algorithm. This code includes ion beam energy deposition using the cold stopping model, which is a valid approximation for the temperature range accessed in these simulations. Different phases of matter achieved due to the beam heating are treated using a semiempirical equation-of-state (EOS) model. To take care of the solid material properties, the Prandl-Reuss model is used. The high specific power deposited by the projectile particles in the target leads to phase transitions on a timescale of the order of tens of nanosecond, which means that the sample material achieves thermodynamic equilibrium during the heating process. In these calculations we use Pb as the sample material that is irradiated by an intense uranium beam. The beam parameters including particle energy, focal spot size, bunch length, and bunch intensity are considered to be the same as the design parameters of the ion beam to be generated by the SIS100 heavy-ion synchrotron at the Facility for Antiprotons and Ion Research (FAIR), at Darmstadt. The purpose of this work is to propose experiments to measure the EOS properties of HED matter including studies of the processes of phase transitions at the FAIR facility. Our simulations have shown that depending on the specific energy deposition, solid lead will undergo phase transitions leading to an expanded hot liquid state, two-phase liquid-gas state, or the critical parameter regime. In a similar manner, other materials can be studied in such experiments, which will be a very useful addition to the knowledge in this important field of research.