On-line Separator Research Articles

The IGISOL technique—three decades of developments

The Ion Guide Isotope Separator On-Line (IGISOL) technique, conceived in the early 1980s as a novel variation to the helium-jet method, has been used to provide radioactive ion beams of short-lived exotic nuclei for fundamental nuclear structure research and applications for three decades. This direct on-line mass separation of primary recoil ions from nuclear reactions has achieved similar extraction efficiencies for both volatile and non-volatile elements throughout the periodic table. The evolution of the ion guide has been driven by the pursuit of physics research on both sides of the valley of beta stability. The gradual improvement in the primary beam intensities of light ions, as well as the ever increasing availability of a range of heavy ions has been matched with the development of novel ion manipulation techniques in order to maximise the output of the IGISOL facility. In this article we describe the continual development of the facility to match the needs of the scientific programme, a relationship which has proceeded hand-in-hand over the years. We will show that this strategy has been and continues to be very important for the huge success of the ion guide method for radioactive ion beam production.

Neutron-rich isotope production using a uranium carbide - carbon nanotubes SPES target prototype

The SPES (Selective Production of Exotic Species) project, under development at the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro (INFN-LNL), is a new-generation Isotope Separation On-Line (ISOL) facility for the production of radioactive ion beams by means of the proton-induced fission of uranium. In the framework of the research on the SPES target, seven uranium carbide discs, obtained by reacting uranium oxide with graphite and carbon nanotubes, were irradiated with protons at the Holifield Radioactive Ion Beam Facility (HRIBF) of Oak Ridge National Laboratory (ORNL). In the following, the yields of several fission products obtained during the experiment are presented and discussed. The experimental results are then compared to those obtained using a standard uranium carbide target. The reported data highlights the capability of the new type of SPES target to produce and release isotopes of interest for the nuclear physics community.

Production of 62Zn radioactive nuclear beam and on-line PAC investigation of quadrupole interaction in nano-magnetic material Fe73.5Cu1Nb3Si13.5B9

An Isotope Separator On-Line (ISOL), dedicated to on-line perturbed angular correlation (PAC) and positron annihilation spectroscopy (PAS), has been constructed at CIAE based on the HI-13 tandem accelerator, and a 30 keV radioactive beam of 62Zn with intensity of 2 ×107/s produced by it. Using the 62Zn radioactive beam the investigation of the nano-crystalline soft magnetic Fe73.5Cu1Nb3Si13.5B9 materials has been fulfiled for the first time by the on-line time differential PAC technique. Two quadrupole interaction frequencies ω01 ( = 440 Mrad/s) and ω02 ( = 90 Mrad/s) were gained, indicating there are two implantation sites of 62Zn. The frequency ω02 shows a fluctuation of the crystal lattice constants and proves the characteristic distribution model of nano-crystalline grain boundary. The frequency ω01 demonstrates that the implanted 62Zn occupies the site of the ordered grain core. The fractions of ω01 and ω02 are f01 = 38 % and f02 = 62 %, respectively.

The Miniball spectrometer

The Miniball germanium detector array has been operational at the REX (Radioactive ion beam EXperiment) post accelerator at the Isotope Separator On-Line facility ISOLDE at CERN since 2001. During the last decade, a series of successful Coulomb excitation and transfer reaction studies have been performed with this array, utilizing the unique and high-quality radioactive ion beams which are available at ISOLDE. In this article, an overview is given of the technical details of the full Miniball setup, including a description of the \(\gamma\)-ray and particle detectors, beam monitoring devices and methods to deal with beam contamination. The specific timing properties of the REX-ISOLDE facility are highlighted to indicate the sensitivity that can be achieved with the full Miniball setup. The article is finalized with a summary of some physics highlights at REX-ISOLDE and the utilization of the Miniball germanium detectors at other facilities.

First on-line results from the CRIS (Collinear Resonant Ionisation Spectroscopy) beam line at ISOLDE

The CRIS (Collinear Resonant Ionisation Spectroscopy) experiment at the on-line isotope separator facility, ISOLDE, CERN, has been constructed for high-sensitivity laser spectroscopy measurements on radioactive isotopes. The technique determines the magnetic dipole and electric quadrupole moments, nuclear spin and changes in mean-square charge radii of exotic nuclei via measurement of their hyperfine structures and isotope shifts. In November 2011 the first on-line run was performed using the CRIS beam line, when the hyperfine structure of 207Fr was successfully measured. This paper will describe the technique and experimental setup of CRIS and present the results from the first on-line experiment.

First successful ionization of Lr (Z = 103) by a surface-ionization technique

We have developed a surface ionization ion-source as part of the JAEA-ISOL (Isotope Separator On-Line) setup, which is coupled to a He/CdI2 gas-jet transport system to determine the first ionization potential of the heaviest actinide lawrencium (Lr, Z = 103). The new ion-source is an improved version of the previous source that provided good ionization efficiencies for lanthanides. An additional filament was newly installed to give better control over its operation. We report, here, on the development of the new gas-jet coupled surface ion-source and on the first successful ionization and mass separation of 27-s (256)Lr produced in the (249)Cf + (11)B reaction.

A test stand for off-line laser ion source development at TRIUMF

A test stand for ion source development and laser resonance ionization spectroscopy was built and commissioned at TRIUMF. The test stand is needed to develop efficient ion sources that can function reliably in the hostile, high temperature, high radiation environment of TRIUMF's isotope separator on-line (ISOL) production target ion source. In addition, it enables laser resonance ionization spectroscopy to develop laser excitation schemes suitable for the solid-state laser systems used with TRIUMF's resonant ionization laser ion source . Also, it allows for possible improvement of current ion sources and validation of new designs. The test stand employs a copy of the ion optics used on-line, so that results can be transferred directly to radioactive ion beam production. Due to space restrictions and the need for rapid mass scans, a quadrupole mass spectrometer is used as a mass separator. One of the first experiments conducted on the laser ion source test stand (LIS STAND) was resonant ionization spectroscopy of gallium to improve on the ionization scheme previously used on-line, so that low yield isotopes (e.g., (62)Ga) become available for experiments. Different Rydberg series in gallium were observed and autoionizing states were searched for. The overall LIS STAND system performance, characteristics, and the first resonant ionization spectroscopy are described.

Experimental Investigation of the Wet Gas Measurement Based on Triple Differential Pressures Method

In order to meter the wet gas without separation online, a novel measurement device composed of a long throat Venturi tube and a V-cone is proposed and a new metering method based on triple differential pressures. In this method, the ratios of the differential pressures are vital parameters used to establish the measurement correlations. The comparison of these correlations is also presented. In laboratory test, the measurement accuracy of the gas and liquid are 2.13% and 6.68% respectively.

Optimization studies of the CERN-ISOLDE neutron converter and fission target system

The ISOLDE facility at CERN has been one of the leading isotope separator on-line (ISOL) facilities worldwide since it became operative in 1967. More than 1000 isotopes are available at ISOLDE, produced after the bombardment of various primary targets with a pulsed proton beam of energy 1.4 GeV and an average intensity of 2 μA. A tungsten solid neutron converter has been used for ten years to produce neutron-rich fission fragments in UCx targets. In this work, the Monte Carlo code FLUKA and the cross-section codes TALYS and ABRABLA were used to study the current layout of the neutron converter and fission target system of the ISOLDE facility. An optimized target system layout is proposed, which maximizes the production of neutron-rich isotopes and reduces the contamination by undesired neutron-deficient isobars. The studies here reported can already be applied to ISOLDE and will be of special relevance for the future facilities HIE-ISOLDE and EURISOL.

Overview of the KoRIA Facility for Rare Isotope Beams

The Korea Rare Isotope Accelerator, currently referred to as KoRIA, is briefly presented. The KoRIA facility is aimed to enable cutting-edge sciences in a wide range of fields. It consists of a 70 kW isotope separator on-line (ISOL) facility driven by a 70 MeV, 1 mA proton cyclotron and a 400 kW in-flight fragmentation (IFF) facility. The ISOL facility uses a superconducting (SC) linac for post-acceleration of rare isotopes up to about 18 MeV/u, while the SC linac of IFF facility is capable of accelerating uranium beams up to 200 MeV/u, 8 pμA and proton beams up to 600 MeV, 660 μA. Overall features of the KoRIA facility are presented with a focus on the accelerator design.

Decays of T Z = − 3/2 nuclei 23Al, 31Cl, and 41Ti

This article gives an overview on the decay spectroscopy of T Z = –3/2 nuclei 23Al, 31Cl, and 41Ti performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility. The results of the IGISOL experiments are compared to the experimental results that have been published since. The isobaric multiplet mass equation (IMME) has been studied for the T = 3/2 quartets at A = 23 and A = 31. For 41Ti, a detailed comparison to the Gamow–Teller strengths obtained for the analog transitions via charge-exchange reactions has been done. Further improvements in the experimental instrumentation and methods and possible implementations for studying T Z = –3/2 nuclei at the new IGISOL facility are discussed.

Resonance laser ionization of atoms for nuclear physics

The applications of the laser resonance ionization method in nuclear research are reviewed. Investigation of radioactive isotopes using resonance ionization techniques provides a valuable combination of high selectivity, efficiency and spectral resolution. The majority of radioactive ion beams produced at on-line isotope separator facilities profit from the selectivity and universal applicability of laser ion sources. Numerous ultra-sensitive and high-resolution techniques of laser spectroscopy based on resonance ionization of atoms have been developed for the study of rare and radioactive isotopes. A summary of ionization schemes applied to radioactive isotopes is given in table form.

Isomer and decay studies for the rp process at IGISOL

This article reviews the decay studies of neutron-deficient nuclei within the mass region \(\ensuremath A=56\mbox{--}100\) performed at the Ion-Guide Isotope Separator On-Line (IGISOL) facility in the University of Jyväskylä over last 25 years. Development from He-jet measurements to on-line mass spectrometry, and eventually to atomic mass measurements and post-trap spectroscopy at IGISOL, has yielded studies of around 100 neutron-deficient nuclei over the years. The studies form a solid foundation to astrophysical rp -process path modelling. The focus is on isomers studied either via spectroscopy or via Penning-trap mass measurements. The review is complemented with recent results on the ground and isomeric states of 90Tc . The excitation energy of the low-spin isomer in 90Tc has been measured as \(\ensuremath E_x=144.1(17)\) keV with JYFLTRAP double Penning trap and the ground state of 90Tc has been confirmed to be the (8+) state with a half-life of \(\ensuremath T_{1/2}=49.2(4)\) s. Finally, the mass-excess results for the spin-gap isomers 53Com and 95Pdm and implications from the JYFLTRAP mass measurements for the (21+) isomer in 94Ag are discussed.

Upgrade of the resonance ionization laser ion source at ISOLDE on-line isotope separation facility: New lasers and new ion beams

The resonance ionization laser ion source (RILIS) produces beams for the majority of experiments at the ISOLDE on-line isotope separator. A substantial improvement in RILIS performance has been achieved through a series of upgrade steps: replacement of the copper vapor lasers by a Nd:YAG laser; replacement of the old homemade dye lasers by new commercial dye lasers; installation of a complementary Ti:Sapphire laser system. The combined dye and Ti:Sapphire laser system with harmonics is capable of generating beams at any wavelength in the range of 210-950 nm. In total, isotopes of 31 different elements have been selectively laser-ionized and separated at ISOLDE, including recently developed beams of samarium, praseodymium, polonium, and astatine.

Initial commissioning results with the NSCL Electron Beam Ion Trap

The ReA reaccelerator is being added to the National Superconducting Cyclotron Laboratory (NSCL) fragmentation facility in order to provide exotic rare-isotope beams, not available at the Isotope Separation On-Line facilities, in the several-MeV/u energy range. The first stage of the NSCL reaccelerator complex, consisting of an EBIT charge breeder, a room-temperature radiofrequency quadrupole (RFQ) accelerator, and superconducting linear accelerator modules, has been completed and is being put into operation. Commissioning of the EBIT has started by extracting charge-bred residual gas ions, ions created from a Ne gas jet directed across the EBIT's electron beam and ions captured from an external test ion source. Charge-bred ions from the Ne gas jet have been extracted as a pulse and accelerated through the RFQ and the two cryomodules.

Characteristics of rare isotope beams in the KoRIA facility

The Korea Rare Isotope Accelerator (KoRIA) facility plans to provide neutron-rich rare isotopes (RIs) and stable heavy ion beams for research in the fields of basic and applied sciences. In the facility, both the isotope separator on-line (ISOL) and the in-flight fragmentation (IFF) methods are employed for RI production by 238U fission, which is effective for producing neutron-rich RI beams. These ISOL and IFF systems are designed to obtain world-class RI beam intensity, which allows exotic nuclei near the neutron drip line in the nuclear chart, which have not yet been explored, to be studied. In this paper, the uniqueness of the KoRIA facility under consideration, compared to other facilities, is described, and we present the characteristics of the RI beams that will be available at KoRIA.

Improved measurement for volatile particles: Vapor-particle separator design and laboratory tests

Sampling and measurement of volatile particles is a challenging task. It has been hampered by lack of a reliable technique capable of accurately capturing the phase-partition process of the pollutants without generating bias and artifacts in the data. The objective of this research is to design a new vapor-particle separation technique for performing the phase separation on-line (the sampling aspect), which, simultaneously, enables characterization of the vapors and particles. The new vapor-particle separator (VPS) consists of a thin metallic microporous membrane for (1) extraction of vapor molecules that are thermally desorbed from the condensed particulate phases and (2) collection of the vapors for subsequent chemical analysis. We evaluated this new separator using synthetic particles made of nonvolatile and or semi-volatile chemicals, and reported the laboratory test results in this paper. The laboratory particle test results showed reasonably high particle transmission efficiency across all particle sizes. The thermal dynamics of nanoparticles was succinctly observed on-line. The results successfully demonstrated the ability of VPS to separate particles and vapors thus enabling a faithful observation of the thermal behavior. We believe the new technology will make a great contribution to the measurement of volatile particles.

A spectrometer for lifetime determination by β–γ–γ delayed coincidence technique at KUR-ISOL

Abstract A new spectrometer for measuring nuclear level lifetimes has been installed at the on-line isotope separator of the Kyoto University Reactor. The spectrometer consists of a LaBr 3 (Ce), Ge and a thin plastic scintillation detector, and the lifetimes are determined using a β – γ – γ delayed coincidence technique. In this study, the LaBr 3 detector was used to obtain time spectra, whereas the Ge detector was used to select a desired γ branch. The energy dependence of the time resolutions was measured down to a photon energy of 100 keV. The lifetimes measured for the excited levels in 93 Sr and 148 Ce agree well with their evaluated values. The lifetime of 8.5(5) ns was obtained for the first time for the 98.2 keV level in 148 Pr.

EURISOL Multimegawatt Target Unit—MAFF Configuration: Dosimetry and Activation Studies

The EURopean Isotope Separation On-Line Radioactive Ion Beam (EURISOL) project aims at building a facility to produce radioactive ion beams with intensities two to three orders of magnitude higher than those presently available. A 4-MW (1-GeV, 4-mA) proton beam hits a liquid mercury converter, generating, by spallation reactions, high neutron fluxes that induce fission in surrounding fissile targets. In this work, Monte Carlo calculations of dose rate and activation were carried out to identify the necessary shielding and access restrictions for each section of the facility, including maintenance, storage, and remote control spaces. These calculations allowed an optimization of the materials chosen for the assembly, based on the radioprotection issues, while taking into account the desired performance of the system. The results of the design studies indicate that the intended performance parameters (namely neutron fluxes, fission rates, and easy fission target manipulation) of the EURISOL multimegawatt target station are in reach. The safety analysis indicates that some regions of the facility need special attention from the safety and radioprotection points of view.

Nuclear structure studies of neutron-rich fission fragments performed at JYFLTRAP

The JYFLTRAP double Penning trap setup at the University of Jyvaskyla, Finland has been used to perform a wide range of studies related to neutron-rich fission fragments that can be produced with the Ion Guide Isotope Separator On-Line (IGISOL) method. Experimental results from high-precision mass measurements and decay-spectroscopy measurements have allowed us to investigate the nuclear structure of exotic neutron-rich nuclei.