UTTAC, Tsukuba, Ibaraki, Japan
University of Notre Dame, Indiana, USA
MSU, East Lansing, Michigan, USA
ANL, Argonne, USA
Kanazawa University, Kanazawa, Japan
The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
The alpha-decaying 146Sm nuclide is used for chronology of the Solar System and silicate mantle differentiation in planets. We performed a new determination of 146Sm half-life by measuring 146Sm/147Sm alpha activity and atom ratios in 147Sm activated via (g,n), (n,2n) and (p,2n) reactions and obtained a value (68 Myr), smaller than that adopted so far (103 Myr), with important geochemical implications*. The experiment required determination of 146Sm/147Sm ratios by high-energy (6 MeV/u) accelerator mass spectrometry to discriminate 146Sm from isobaric 146Nd contaminant. Activated Sm targets were dissolved, chemically purified and reconverted to metallic Sm. Sputter cathodes, made by pressing the Sm metal into high-purity Al holders, were used to feed the Argonne ECR ion source. 146Sm22+, 147Sm22+ ions were alternately injected and accelerated with the ATLAS linac by proper scaling of ion source and accelerator components. A tightly-fitted quartz cylindrical liner was inserted in the ECR plasma chamber to reduce contamination from the walls. 146Sm ions were eventually counted in a gas-filled magnet and 147Sm ions either measured as charge current or counted after proper attenuation.
* N. Kinoshita et al., Science 334, 1614 (2012)
ANL, Argonne, USA
A project using Accelerator Mass Spectrometry (AMS) at the ATLAS facility to measure neutron capture rates on a wide range of actinides in a reactor environment is underway. This project will require the measurement of a large number of samples previously irradiated in the Advanced Test Reactor at Idaho National Laboratory. The AMS technique at ATLAS is based on production of highly-charged positive ions in an electron cyclotron resonance ion source (ECRIS) followed by acceleration in the ATLAS linac. The sample material is introduced into the plasma via laser ablation. This should limit the dependency of material feed rates upon the source material composition as well as minimize cross-talk between samples. A new multi-sample changer has been constructed allowing rapid changes between samples. The sample changer has 20 positions and is capable of moving from one sample to the next in one minute. Details of the sample changer design and operation will be presented.
ANL, Argonne, USA
GANIL, Caen, France
The Californium Rare Ion Breeder Upgrade (CARIBU) of the ATLAS superconducting linac facility aims at providing low-energy and reaccelerated neutron-rich radioactive beams to address key nuclear physics and astrophysics questions. These beams are obtained from fission fragments of a Cf-252 source, thermalized and collected into a low-energy particle beam by a helium gas catcher, mass analyzed by an isobar separator, and charge bred with an ECR ion source for acceleration in ATLAS. The charge breeding program had focused on optimizing beams in the mid-mass range, achieving high charge breeding efficiencies of both gaseous and solid species including 14.7% for the radioactive species 143Ba27+. In an effort to better understand the charge breeding mechanism, we recently focused on the low-mass species sodium and potassium which up to present have been difficult to charge breed efficiently. Charge breeding efficiencies of 10.1% for 23Na7+ and 17.9% for 39K10+ were obtained injecting stable Na+ and K+ beams from a surface ionization source. Details of these studies will be presented as well as simulations detailing the injection of the low charge state beams into the charge breeder.
ANL, Argonne, USA
University of Notre Dame, Indiana, USA
INL, Idaho Falls, Idaho, USA
ISU, Pocatello, Idaho, USA
The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
CEA Cadarache, Saint Paul Lez Durance, France
A project using accelerator mass spectrometry (AMS) is underway at the ATLAS facility to measure the atom densities of transmutation products present in samples irradiated in the Advanced Test Reactor at INL. These atom densities will be used to infer effective actinide neutron capture cross-sections ranging from Thorium to Califorium isotopes in different neutron spectra relevant to advanced fuel cycles. This project will require the measurement of many samples with high precision and accuracy. The AMS technique at ATLAS is based on production of highly-charged positive ions in an ECRIS followed by injection into a linear accelerator. We use a picosecond laser to ablate the actinide material into the ion source. We expect that the laser ablation technique will have higher efficiency and lower chamber contamination than sputtering or oven evaporation thus reducing 'cross talk' between samples. The results of off-line ablation tests and first results of an accelerate beam generated by the laser coupled to the ECR will be discussed as well as the overall project schedule.