B.J. Zabransky

Development and operation of gas catchers to thermalize fusion–evaporation and fragmentation products

Abstract A new approach to the production of low energy radioactive beams involves the stopping of fast beams produced by fragmentation, in-flight fission or fusion–evaporation reaction into a large gas catcher where the reaction products are thermalized in high-purity helium and extracted as singly charged ions for post-acceleration. This removes the limitation present in standard ISOL technique for species that are difficult to extract from the target/ion source assembly. This approach has been implemented at Argonne since 1998 to inject fusion–evaporation products in an ion trap system. Via a series of improvements since then, we now reach efficiencies for these devices of close to 50% with delay times below 10 ms. In preparation for the RIA project, a larger device for stopping fragmentation products is in preparation. The basic principles behind these devices together with results obtained and experience gained operating these devices will be presented. Preparation for a test of the large gas cell at the full RIA energy at GSI will also be presented.

Production of radioactive ion beams using the in-flight technique

Reactions with a heavy projectile incident on a light target can be used for the efficient in-flight production of secondary radioactive beams. An overview of this technique is given using data on 17F beams produced via the p(17O, 17F)n and d(16O, 17F)n reactions. With primary 16,17O beam currents of 100 pnA, intensities of up to 2×106 17F/s on target were achieved. Using this beam, the p(17F,α)14O reaction was measured.

Ultrathin foils for Coulomb-explosion experiments

We have examined the properties of very thin foils used for electron stripping of MeV molecular ions in Coulomb‐explosion experiments. Carbon foils with a nominal thickness of 0.2 μg/cm2 proved to be thicker than 1 μg/cm2. It was not possible to reduce their thickness by bombardment with 2‐MeV Kr+ or H2O+ ions or by heating to a red glow. We succeeded in producing Formvar films of about 0.5 μg/cm2, which are supported by a nickel mesh.

Mass measurements near the r-process path using the Canadian Penning Trap mass spectrometer

The masses of 40 neutron-rich nuclides from Z = 51 to 64 were measured at an average precision of

Diminished stopping power for fast nitrogen and oxygen diclusters in carbon

\delta m/m= 10^{-7}

A multiparticle 3d imaging technique to study the structure of molecular ions

using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a

Metastable Phases in Ferrous Chloride Hydrates

^{252}

Stopping Power for Fast Nitrogen and Oxygen Diclusters in Carbon

Cf spontaneous fission source in a helium gas catcher, approach the predicted path of the astrophysical

ISOL beams from fragmentation: the best of both worlds

r

A new type of multiparticle imaging detector

process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in