Session MK: Applications II

Development and Implementation of 41Ca for Accelerator Mass Spectrometry Measurements

Ever since its discovery in the late 1930s, ⁴¹Ca has been recognized for its diverse range of applications and has recently become an interest in several fields of research including biomedical physics, nuclear forensics, and nuclear astrophysics. With its long half-life (t_1/2 = 9.94 x 10⁴ yrs), it is often impractical to detect ⁴¹Ca through typical decay counting techniques. However, utilizing the technique of accelerator mass spectrometry (AMS) available at the Nuclear Science Laboratory (NSL) at the University of Notre Dame, we are able to detect individual ions to attain an isotopic concentration of the material of interest. While developed and standardized at other labs around the world, developing and detecting ⁴¹Ca has never been performed at the NSL, therefore detection limits first need to be obtained. Four CaF standard samples of varying concentrations will be used to determine the sensitivity limits and get first results with our current AMS system. Detection and discrimination between ⁴¹Ca and its isobaric contaminant ⁴¹K will be performed and compared using both the time-of-flight and gas-filled magnet techniques. First results of measurements and sensitivity limits will be discussed along with planned future experiments.   

Development of 129I AMS at the NSL: Environmental Sampling in the Great Lakes Region

¹²⁹I in the environment primarily comes from releases by European nuclear fuel reprocessing centers.  Iodine moves easily through the environment as it is highly soluble, volatile, and easily incorporated into biological organisms, which causes releases of ¹²⁹I in Europe to affect concentrations globally.  This high mobility makes ¹²⁹I an excellent environmental tracer in fields such as geology and nuclear safeguards.  However, because of its long half-life of 15.7 Myr, detection of ¹²⁹I through decay counting methods is often unrealistic because of the sample size required.  Accelerator mass spectrometry (AMS), on the other hand, is well suited for the detection of ¹²⁹I as it can identify individual ions through isotopic and isobaric discrimination which, for ¹²⁹I, relies on the time-of-flight method.  Environmental sampling throughout the United States has been mostly limited to areas surrounding nuclear facilities, which inspired the AMS group of the Nuclear Science Laboratory at the University of Notre Dame to measure ¹²⁹I concentrations in the Great Lakes region to establish a baseline for measuring the change of these concentrations in the future.  Preliminary results of ¹²⁹I measurements and future plans will be discussed.   

Developments of time-of-flight detector for mass measurements with the Rare-RI Ring

Development of the storage ring "Rare-RI Ring (R3)" for mass measurement of the short-lived RI is in progress at the RI Beam Factory in RIKEN. The mass-to-charge ratio of exotic nuclei is determined by the velocity of the nuclei and the revolution time of those in the R3.
We are developing the time-of-flight (TOF) detector which measures both velocity and revolution time in the R3. In our TOF detector, MCPs are used for detecting secondary electrons emitted from a thin foil where the ions pass through.
We measured time resolution for this detector with the ⁸⁴Kr beams of 200 MeV/nucleons provided by Heavy Ion Accelerator in Chiba in National Institute of Radiological Sciences. In the conference, we will show the design of this detector and the result of the time resolution.   

Experimentally constrained $^{92}$Sr($n,\gamma$) reaction rate

Although fission was discovered 80 years ago, fundamental data for neutron-induced production and destruction of fission products is missing. This data deficiency leads to reaction-rate uncertainties up to several orders of magnitude. An area particularly deficient in neutron-induced cross section data is the A=95 fission fragment region. To address this need, an experiment to indirectly determine the neutron-capture cross section on a short-lived fission fragment, $^{92}$Sr, was recently performed at the NSCL utilizing a total absorption spectrometer to measure the emitted $\gamma$ rays from $^{93}$Sr following the decay of $^{93}$Rb. The $\beta$-Oslo method is used in the ongoing data analysis to extract to extract level density and $\gamma$-decay strength, two key ingredients for calculating ($n,\gamma$) reaction rates. Preliminary analysis of measured $\gamma$-ray spectra will be presented here. The results will also provide crucial tests for model input to infer the ($n,\gamma$)$^{95}$Sr reaction rate, which is a high-yield fission product.   

Bringing Nuclear Science Experiments to the Classroom

While basic concepts of nuclear science are part of many states' science curricula, few schools have the materials needed for students to conduct experiments in this area.  Using a small grant from the American Nuclear Society, a “lending library” of equipment has been assembled that allows teachers and their students to conduct several simple nuclear science experiments in their classrooms.  After attending one training session, teachers can check out kits containing Geiger counters, radioactive sources, and a variety of materials containing low levels of radioactivity.  Teachers are provided with a guidebook on nuclear science and instructions on how to lead their students in experiments to:  distinguish alpha, beta, and gamma radiations; measure the half life of a radioactive nucleus; observe radiation from materials that may be found in the home.  In this talk, issues involved in setting up programs of this kind will be discussed as well as feedback received from teachers.