[en] The present report gives a short summary of current work at the CPT mass spectrometer and provides a list of recent references for work published in the last few years.

[en] The Rare Isotope Accelerator (RIA) is a next generation radioactive beam facility designed to provide experimental access to large unexplored regions of the nuclear landscape. To do this, RIA makes use of standard ISOL and in-flight fragmentation technology together with novel approaches to handle high primary beam power and remove existing limitations in the extraction of short-lived isotopes. The use of a versatile primary accelerator allows various production and extraction schemes to be used to optimize production of specific isotopes. These isotopes are then available for studies at ion source energy or can be further accelerated by a superconducting linac whose novel injection system allows the efficient acceleration from ion source energy of singly-charged heavy ions with masses up to 240 amu. The high-intensity radioactive beams at RIA will be made available to experimental areas spanning the energy regime from ion source energy to primary beam energy

[en] The Californium Rare Ion Breeder Upgrade (CARIBU) project utilizes ²⁵²Cf to provide beams of neutron-rich nuclides with intensities not currently available at other facilities. The electroplated ²⁵²Cf source is positioned inside a large helium gas catcher, where the ejected fission fragments lose their energy and are slowed. Prior to entering this gas catcher, the ions first pass through a gold cover foil to contain self-sputtering recoil emissions and then through an aluminium degrader foil, where much of their residual energy is reduced. In the past due to production limitations, a less than ideal cylindrical shaped degrader was utilized. This resulted in non-uniform energy loss as the ions passed through the degrader. With the advent of 3D printing, a new hemispherical degrader was prepared to enable a more uniform energy loss. The design, production, and assembly will be discussed.

[en] We have undertaken studies to identify the stable beam backgrounds that cause ‘contamination’ of the ECR ion source charge-bred radioactive beams from CARIBU (Californium Rare Ion Breeder Upgrade). Charge breeding of the radioactive species is necessary step prior to the acceleration of the beams in the ATLAS linac. Ion species whose (m/q) ratio is within 0.2% of the desired radioactive species (m/q) ratio cannot be discriminated against by the present accelerator configuration. Although there are many (m/q) instances in which an intense stable beam is sufficiently degenerate with the species of interest that no discrimination is possible, we also find many cases in which the stable beam background is in an acceptable range of intensity and can be dealt with by the experiment detection system. Examples of such situations will be presented as well as some discussion of ideas for improving the discrimination against stable beam backgrounds. This work is supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract No. DE-AC02-06CH11357.

[en] The CARIBU facility uses a high-intensity gas catcher system to transform "2"5"2Cf fission fragments into a beam that can then be delivered to experiments at low-energy or at Coulomb barrier energy after post-acceleration through the ATLAS superconducting linac. The method is fast and universal, allowing unique beams of short-lived refractory and reactive isotopes to be extracted and delivered to experiments. The facility hosts an extensive suite of experimental equipment and measurements have been performed with over 100 different neutron-rich isotopes so far. The unique approach used for CARIBU will be described below, together with the present physics program and upcoming upgrades. (author)

[en] A proposed upgrade to the radioactive beam capability of the ATLAS facility has been proposed using 252Cf fission fragments thermalized and collected into a low-energy particle beam using a helium gas catcher. In order to reaccelerate these beams the ATLAS ECR-I will be reconfigured as a charge breeder source. A 1Ci 252Cf source is expected to provide sufficient yield to deliver beams of up to ∼103 far from stability ions per second on target. A brief facility description and the expected performance information are provided in this report

[en] Gas catchers provide a means to transform radioactive recoils from various production mechanisms into low-energy beams of good ion optical properties. Recent developments with large radio-frequency gas catchers have pushed back purity and space-charge limitations in this technology to the point that it can now be used reliably for producing radioactive beams intense enough for various secondary experiments to be possible. The basic technology available and the current demonstrated capabilities are presented in the following. A number of examples of such systems currently under commissioning/construction/design at ANL to produce beams from fusion-evaporation, fission, deep-inelastic and fragmentation reaction products will also be presented together with the specific challenges to each approach and the chosen solutions.

[en] Collinear laser spectroscopy (CLS) provides the opportunity to extract nuclear charge radii and magnetic dipole as well as electric quadrupole moments in a nuclear-model independent way. CLS utilizes the reduction of velocity spread via acceleration with a DC high-voltage potential of typically a few 10 kV. The isotopes of interest have to exhibit electronic transitions which are accessible with laser systems and sensitive to changes of nuclear charge radii. If these are not available from the ionic ground state, charge exchange can provide access to suitable atomic transitions. We present an updated design of a charge exchange cell for CLS, that can hold acceleration potentials up to 30 kV and operate at temperatures above 430 C to allow for charge exchange with magnesium vapor. The cell is developed in Darmstadt and will be used at Argonne National Laboratory (ANL), where the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) opens up new possibilities for in-flight laser spectroscopy of short lived isotopes, especially in the region beyond the sudden deformation at N=60 and Z>38.

[en] The Californium Rare Ion Breeder Upgrade (CARIBU) project was conceived to provide neutron rich beams originating from the 3% fission decay branch of a ²⁵²Cf source to be accelerated by the Argonne Tandem Linear Accelerator System (ATLAS). This 1Ci ²⁵²Cf source will be housed in a movable shielded cask, from which it can be directly transferred into a large helium gas stopper cell. Within the gas stopper, the CARIBU ²⁵²Cf source is positioned behind an aluminum degrader foil where the radioactive recoils of interest lose most of their energy before being stopped in the helium gas. To stop recoils over the full fission mass range effectively, three degraders of increasing thickness are required, one to cover the light fission peak and two for the isotopes in the heavy fission peak. The geometry of the source within the gas cell would ideally require a hemispherically shaped degrader foil for uniform energy loss of the fission products. The fabrication of a thin foil of such a shape proved to be exceedingly difficult and, therefore, a compromise 'top hat' arrangement was designed. In addition, the ultra-high vacuum (UHV) environment necessary for the gas cell to function properly prevented the use of any epoxy due to vacuum outgassing. Handling, assembling of the foils and mounting must be done under clean room conditions. Details of early attempts at producing these foils as well as handling and mounting will be discussed.

[en] Much of astrophysics is fueled by nuclear physics with observables, such as energy output and elements produced, that are heavily dependent on the masses of the nuclides. A mass precision of at least 50 keV/c${}^2$ for many rare nuclides is needed to adequately discriminate models that explain the observables. In recent decades, the development of new facilities and mass-measurement techniques has made available a wealth of precise and accurate mass data. The new data, in combination with novel codes and models, has greatly enhanced the understanding of astrophysical processes in the universe, but much is still to be learned.