|The 5MV St. ANA Accelerator -- 2011|
The new 5MV Stable beam Accelerator for Nuclear
Astrophysics (St. ANA) to be installed at the Nuclear Science
Laboratory at the University of Notre Dame represents a major
equipment upgrade. The accelerator will provide high intensity
heavy ion beams for experiments with the St. George recoil
separator, but it will also increase the intensities for proton and
alpha beams, necessary for studying some astrophysical
|The ND AMS Facility - Probing Galactic Radioactivity -- 2010|
Gamma-rays from radioactive by-products of nucleosynthesis ejecta provide a direct measurement of cosmic nucleosynthesis (i.e. the formation of nuclei in stellar environments) as the detection of the decay gamma-rays with satellite-borne telescopes provide direct isotopic constraints to the physics of nuclear burning regions inside stars.
|Preparation for a New 5MV Accelerator -- 2010|
The new 5 MV accelerator to be installed at the Nuclear Science Laboratory at the University of Notre Dame represents a major equipment upgrade. The accelerator will provide high intensity heavy ion beams for experiments at the St. George recoil separator, but it will also increase the intensities for proton and alpha beams.
|The cross section of the 14N(p,g)15O reaction in the CNO cycle -- 2009|
The experiments were performed at the low energy accelerators of the Notre Dame Nuclear Science Laboratory. The cross section was measured over a large energy range from about 0. 25 MeV to 3.5 MeV. Special attention was given to determine the angular distribution of the emitted g radiation. A special detector arrangement consisted of a Ge clover detector at 45° with 5 Ge detectors mounted at different angles. Both implanted 14N and TiN targets have been used for the experiments. The experiments were successfully completed and are presently being analyzed.
|Systematic Study of a-Optical Potentials for p-Process -- 2009|
To test the reliability
of the HF calculations and provide a systematic understanding of
the alpha optical potential at energies of astrophysical interest,
a series of precision alpha scattering measurements were carried
out at the Notre Dame FN tandem accelerator. Specifically, 106Cd,
118Sn, and 120,124,126,128,130Te were studied
at energies both below and above the Coulomb barrier: 17, 19, 22,
24.5, and 27 MeV.
|Test of extrapolating models for heavy ion fusion
reactions at extreme sub-barrier energies --- 2009
model or equivalent square-well optical model (Fowler model) are
used to fit the average cross section and predict the reaction cross
sections at the energies of astrophysical interest. Recently, a
new model, the hindrance model, was proposed to provide systematic
fits to fusion reaction data at extreme sub-barrier energies. The
goal of this project is to test the models by pushing the lowest
measured energies down towards the astrophysics relevant region.
|Experimental investigation of the reactions
25Mg(a,n)28Si, 26Mg(a,n)29Si and 18O(a,n)21Ne --- 2009
Recent results from meteoritic
grain measurements and stellar models indicate that an enhanced
experimental data set of the reactions 25Mg(a,n)28Si,
unveil a clearer picture on their role toward stellar nucleosynthesis.
The new reaction rates will be implemented into stellar models and
the resulting isotopic abundance patterns then compared to measured
isotopic abundance patterns in meteoritic inclusions.
|Understanding X-ray Bursts --- 2009|
X-ray bursts are some
of the most energetic events observed in the cosmos. It is thought
that X-ray bursts are the thermonuclear explosions occurring near
the surface of accreting neutron stars. The material accreted from
the companion star is funneled to the surface of the neutron stars.
The extreme density found near the surface of the neutron star provides
the environment for explosive Hydrogen and Helium burning.
|Neutron poisoning efficiency of 16O in the s-process -- 2009|
Most of the heavy elements
in the universe are produced by sequential neutron captures on lighter
nuclei during the helium burning stage of stellar evolution. The
efficiency of these processes depends on the abundance of neutron
sources, of seed nuclei for the buildup towards heavier elements
and so called neutron poisons, which remove neutrons from the stellar
|15N(p,g) Experiment and R-Matrix Analysis --- 2009|
The R-matrix analysis
code, AZURE, has been successfully used to fit the new data, and
extrapolate the calculation down to astrophysically relevant energies.
The results demonstrate the predictive power of Rmatrix techniques
in evaluating and extrapolating low energy reaction cross sections.
Reaction rate calculations have been performed and are significantly
reduced compared with current compilations.
|Fusion Reactions at the Limits of Stability --- 2009|
Nuclear reactions are at the heart of stellar structure, evolution and nucleosynthesis from main sequence, giants and super-giants to supernovae, white dwarfs and neutron stars. Depending on fuel, temperature, and density, stellar burning may involve many reactions of different nuclei, from light to heavy and stable to extremely neutron rich ones. The possibility of fusion reactions between low mass nuclei at low temperatures but extremely high densities occurs in the cores of white dwarfs and the crust of neutron stars. In white dwarf matter the 12C+12C fusion may trigger type I supernovae, in neutron star crusts fusion between very neutron rich nuclei may provide internal heating.
|A Jet-Gastarget for the St. George recoil mass separator -- 2009|
The recoil mass separator St. George at Notre Dame is primarily designed to study alpha capture reactions in inverse kinematics. Therefore a heavy ion beam is in combination with a 4He gas target. We designed a differentially pumped windowless jet-gas target to reduce beam straggling and back ground scattering and provide a point-like source for the recoil separator.
|a-Capture Measurements on p-Nuclei --- 2009|
for the p-nuclei involve an extended network of about 20,000 nuclear
reactions of almost 2000 nuclei with masses ranging from 12 to 210.
These associated photodissociation and capture rates are typically
calculated with the statistical Hauser Feshbach Model (HF-Model).
The (y,a) flow is critical for the processing of heavier elements
towards lower masses in the p-process flow.
|New Resonances in 24Mg((a,g)28Si and Stellar Carbon Burning -- 2008|
20Ne and 24Mg are important products of nucleosynthesis in stellar carbon burning. The 24Mg((a,g)28Si reaction is of significant importance for the possible subsequent depletion of 24Mg. The cross section in the stellar Gamow window for carbon burning between 1.0 MeV and 1.6 MeV is characterized by a number of resonances which are not well known.
|Direct Capture Strength in the 16O(a,g)20Ne Reaction --- 2008|
The 16O((a,g)20Ne reaction is of significant importance for stellar Helium burning. The reaction rate is low at temperatures of stellar helium burning and is therefoe identified as the "end-point" of the main reaction chain 4H(2(a,g)12C((a,g)16O((a,g)20Ne which is induced by the triple alpha process.
|The PIXE-PAN Outreach Program @ ISNAP --- 2007|
A successful new program in the tradition of the JINA PAN program at MSU has been introduced at Notre Dame. The PIXE-PAN program at Notre Dame uses the existing low energy accelerator facility to introduce high school teachers and students to a two week program in material analysis techniques with accelerators.
|Reaction flow and flow hindrance in the p-process --- 2007|
The p-nuclei are stable but very rare neutron deficient isotopes of the elements above Z=42. In our present interpretation they are produced by photodisintegration processes of heavy elements in high photon-flux environments. Such conditions are expected in the type II supernova shock front heating and compressing the outer layers of the star.
|The Origin of Fluorine --- 2007|
The origin of fluorine has been unknown and speculations ran from AGB star inter-shell burning during late stellar evolution to neutrino induced production in supernova type-II explosions. Recent spectroscopic observations of post AGB stars showed strong indications of fluorine abundance in the stellar spectrum.
|17th Century Indian-Colonial Trade in Indiana --- 2007|
In collaboration with the Department
of Anthropology a program was initiated at the Notre Dame accelerator
facilities to analyze the composition of copper samples of Western
Indiana native heritage. The goal is to determine the providence
of the material and provide information of 17th -18th
century cultural connections and trading patterns between Western
Indiana and the British and French Colonies.
|The Nuclear Trigger of Type I X-ray Bursts --- 2006|
Twenty years ago it was
predicted that the reaction rate is dominated by a single resonance
with 4.03 MeV excitation energy in 19Ne. Numerous research groups
have tried to measure the resonance and its strength and determine
the trigger temperature for X-ray bursts. We have performed the
first successful measurement of the á-decay of the 4.03 MeV state
using the Notre Dame TwinSol system.
|The Rhinoceros Gastarget at Notre Dame --- 2006|
gas-target systems are important instruments for low energy measurements
of relevance for nuclear astrophysics. The gas provides pure target
material conditions, and the beam energy loss is minimized so that
the measurements can be pursued towards very low energies. The Rhinoceros
gas-target from the University of Stuttgart has been installed at
the Notre Dame Nuclear Science laboratory for measuring the low
energy cross sections of alpha capture reactions in stellar helium