A.F. Levand

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.

First Results from the CARIBU Facility: Mass Measurements on the r-Process Path

The Canadian Penning Trap mass spectrometer has made mass measurements of 33 neutron-rich nuclides provided by the new Californium Rare Isotope Breeder Upgrade facility at Argonne National Laboratory. The studied region includes the 132Sn double shell closure and ranges in Z from In to Cs, with Sn isotopes measured out to A=135, and the typical measurement precision is at the 100 ppb level or better. The region encompasses a possible major waiting point of the astrophysical r process, and the impact of the masses on the r process is shown through a series of simulations. These first-ever simulations with direct mass information on this waiting point show significant increases in waiting time at Sn and Sb in comparison with commonly used mass models, demonstrating the inadequacy of existing models for accurate r-process calculations.

Double- β -decay Q values of Te 130 , Te 128 , and Te 120

The double-

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

\ensuremath{\beta}

Charge breeding results and future prospects with electron cyclotron resonance ion source and electron beam ion source (invited)a)

-decay

Performance of the Argonne National Laboratory electron cyclotron resonance charge breeder

Q

Development of electron beam ion source charge breeder for rare isotopes at Californium Rare Isotope Breeder Upgrade.

values of

The CARIBU Facility

^{130}\mathrm{Te}

Operational experience with the Argonne National Laboratory Californium Rare Ion Breeder Upgrade facility and electron cyclotron resonance charge breedera)

,

Radiation Simulations and Development of Concepts for High Power Beam Dumps, Catchers and Pre-Separator Area Layouts for the Fragment Separators for RIA

^{128}\mathrm{Te}