ISNAP Seminars - Abstracts 2014 Fall

Topic: The reactions 12C(α,γ)16O and 12C+12C in direct experiments – Present status and perspectives

Dr. Frank Strieder ( Ruhr-Universität Bochum, Germany ) / August 18, 2014

The capture reactions 12C(α,γ)16O takes place in the helium burning of Red Giants and the 12C+12C fusion reactions are the main processes in carbon burning of massive stars. These reactions determine not only the nucleosynthesis of elements up to the iron region but also the subsequent evolution of massive stars, the dynamics of a supernova, and the kind of remnant after a supernova explosion. For these reasons, the cross section at the relevant astrophysical energy should be known with a precision of at least 10% for reliable models of late stellar evolution.
In spite of tremendous experimental efforts in measuring this cross section over nearly 40 years, one is still far from this goal. The available experimental data of these two important nuclear processes will be reviewed and open problems, questions, and ambiguities will be discussed. Finally, the prospects for new experiments will be outlined, with particular emphasis on the potentials and challenges of measurements at a future underground accelerator facility.

Topic: Fundamental Symmetries and Quantum Chaos

Prof. Vladimir Zelevinsky ( NSCL, Michigan State University ) / September 8, 2014

The statement that the atomic nucleus is a natural laboratory for studying fundamental symmetries became a common place. It is especially important now when nuclear physics enters a new period of tempestuous development with new ideas and new powerful facilities. In the talk I will discuss two examples - parity non-conservation and the search for the electric dipole moment violating both parity and time-reversal invariance - from the viewpoint of nuclear many-body mechanisms which can enhance those effects. In the first example the main role is played by many-body quantum chaos which is confirmed by experiments (the ideas of quantum chaos will be briefly explained along the road). In the second example, we have no data but just ideas of promising nuclear structure mechanisms of considerable enhancement.

Topic: High-precision Penning trap mass spectrometry of stable and long-lived isotopes

Prof. Mathew Redshaw ( Central Michigan University ) / September 15, 2014

The mass of an atom is one of its most fundamental properties that, through Einstein’s relation E = mc2, provides direct information on the energy required to bind a particular nucleus together. The mass difference between the relevant parent and daughter atoms defines, for example, the Q-value for single and double β-decay and electron capture (εc). These quantities are important for experiments that aim to determine the absolute neutrino mass scale, for experimental searches for neutrino-less double β-decay and neutrino-less double electron capture, and for identifying candidates that could undergo weak decay processes, such as very low energy β-decays. Over the last few decades the Penning trap, which consists of a strong uniform magnetic field and a weaker quadrupole electric field, has become the tool of choice for performing precise and accurate atomic mass determinations. In this talk I will discuss β-decay Q-value measurements performed using Penning traps at Florida State University and Michigan State University, and will describe a new high-precision Penning trap for measurements with long-lived radioactive isotopes that is currently under development at Central Michigan University.

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Topic: Special Nuclear Seminar: New frontiers of high energy density science on the NIF laser

Dr. Bruce Remington ( Lawrence Livermore National Lab ) / September 23, 2014

Over the past 3 decades there has been an exponential increase in the newly emerging field of high energy density (HED) science. With the commissioning of the National Ignition Facility laser at LLNL, this field can now access new regimes of HED conditions in matter. I will describe a selection of examples of the HED science being pursued on NIF and on supporting facilities, drawing from inertial confinement fusion (ICF) and the ignition effort, applied HED science for the labs, and very recent progress in fundamental science on NIF. Areas of interest include probing the properties of matter in deep planetary interiors, stellar birth dynamics, supernova turbulent explosion dynamics, collisionless astrophysical shock formation and evolution, and nuclear reactions in dense HED plasma environments. In conclusion, I will describe the new Discovery Science program on NIF, with a look to the future.
* This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Topic: Science in a melting pot - TRIUMF's efforts to advance the field of isotope production

Dr. Paul Schaffer ( TRIUMF, Canada ) / September 29, 2014

With the imminent shutdown of some of the world's largest isotope production reactors and the number of small (<24 MeV) cyclotrons approaching 1000 machines in over 70 countries around the globe, the time is ripe to establish accelerators as a viable source of radionuclides. TRIUMF seeks to address looming shortages of important single photon- (SPECT) and positron emission- (PET) clinical isotopes such as Tc-99m and to demonstrate the production of promising new applications for isotopes including Zr-89, Ga-68, Y-86 and Sc-44 that are of increasing interest to chemists, biologists and medical researchers. Isotopes both for diagnostics of a variety of diseases and for the treatment of cancer are being studied.

Typically, Tc-99m is made available via a generator through the decay of Mo-99, which originates from nuclear reactors. Canada has played a pivotal role in the Mo-99 supply with a capacity of producing 80% of the world's demand from the (Chalk River) NRU reactor. This reactor is scheduled to cease isotope production activity in 2016 and an alternative production method is needed. TRIUMF, in collaboration with other Canadian institutions is leading the effort to produce Tc-99m directly on small cyclotrons via the Mo-100(p,2n) reaction. Recent successes have seen 10 Ci (370 GBq) of Tc-99m produced in a single 6 hr irradiation on a 300 µA TR19 cyclotron at the BC Cancer Agency, enough to supply a city similar in size and geography to Vancouver, British Columbia.

In addition to large-scale production of radiometallic isotopes using solid target materials, research at TRIUMF seeks to investigate the use of liquid targetsto produce research quantities of Zr-89, Ga-68, Sc-44 and Y-86 in order to increase their availability. With this new approach, we hope to open the door for the development of novel PET tracers and an accelerated investigation of the match of the physical half-life of an isotope and the pharmacokinetic profile of new targeting vectors to which it is attached. To date, mCi (MBq) quantities of Ga-68, Zr-89, Sc-44, Y-86, and Cu-61 have been demonstrated. Finally, a brief discussion will ensue on TRIUMF's efforts to apply our Isotope Separation On-Line (ISOL) for the isolation of radiotherapeutic isotopes at the ISAC facility at TRIUMF. Progress on the isolation of At-211 (via Rn-211 decay) and Ac-225 will be presented. Both At-211 and Ac-225 are alpha-emitting isotopes with the potential to treat micro-metastases and/or monocellular malignancies such as leukemia. TRIUMF seeks to demonstrate and enable clinical trials with these and many other potentially useful radiotherapeutic isotopes available through its existing science program.

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Topic: Underground nuclear astrophysics for the Sun, and for the Big Bang

Dr. Daniel Bemmerer ( Helmholtz-Zentrum Dresden-Rossendorf, Germany ) / November 10, 2014

After the resolution of the solar neutrino problem in 2002, the study of the Sun has now entered a precision era, and an entirely new dilemma has come up: New elemental abundance data from Fraunhofer line analyses are in contradiction with helioseismological observables. Observations of 13N and 15O neutrinos from the Sun may address this so-called solar abundance problem, but their interpretation will require precise nuclear reaction data. Due to the low cross sections involved, such data can only be provided by experiments in an underground low-background setting. Work at the world's only underground accelerator, the 0.4 MV LUNA machine in Gran Sasso (Italy), on solar fusion reactions and on the Big Bang production of lithium-6 and -7 will be reviewed. In addition, some surface-based data on radiative capture reactions on 12C, 14N, and 40Ca will be shown. The status and working program of the planned higher-energy underground accelerator at the Dresden Felsenkeller in Germany will be discussed.

Topic: The Electron-Beam Ion Trap (EBIT) chargebreeder of the ReA post-accelerator

Dr. Alain Lapierre ( NSCL, Michigan State University ) / November 24, 2014

An Electron-Beam Ion Trap (EBIT) charge breeder is being commissioned at the NationalSuperconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). The EBIT ispart of the ReA post-accelerator for reacceleration of rare isotopes, which are thermalized in aHe gas cell after production at high energy by projectile fragmentation. The ReA EBIT has adistinctive design; it features a high-current electron gun and a two-field superconductingmagnet to optimize the capture and charge breeding efficiency of "continuously" injected singlycharged ion beams. Following a brief overview of the reaccelerator and the ReA EBIT, this talkwill present the latest commissioning results, particularly, charge breeding efficiency studies,work on stretching the extracted pulses in time, ion beam contamination measurements, andreacceleration tests of highly charged rare isotope beams.

Topic: Charge-exchange reaction studies combined with gamma-ray spectroscopy for astrophysical applications

Dr. Shumpei Noji ( NSCL, Michigan State University ) / December 9, 2014

Charge-exchange reactions at intermediate energies are a powerful tool for studying the spin-isospin structure of nuclei. They become even more so when combined with high-resolution gamma-ray spectroscopy, allowing one to pin down specific excitations with precise energy determination or providing new spin-isospin selectivities that are not possible with conventional reaction probes. They are useful in particular for studying stellar electron captures, supernova nucleosynthesis, and a variety of other astrophysical phenomena. In this seminar, I will discuss some of these instances including recent results of the (t,3He+gamma) experiments with the germanium detector array GRETINA and the S800 spectrometer at NSCL/MSU. Further, I will describe an upcoming (6Li,6Li'[3.56 MeV]+gamma) experiment with a Clover germanium detector array CAGRA at the Grand Raiden spectrometer at RCNP, Osaka University.

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Topic: Ion Traps for Astrophysics

Dr. Jason Clark ( Argonne National Laboratory ) / December 15, 2014

The astrophysical r process is thought to be responsible for the creation of half of the elements heavier than iron. In an attempt to reproduce the observed distribution of element abundances in the universe, models are generated which inherently rely upon many nuclear physics inputs, including the masses of the nuclides involved and their beta-decay properties. However, the uncertainties in these nuclide properties are often too large and limit our understanding of heavy-element nucleosynthesis, yet more precise measurements of these properties are difficult to obtain since a large number of the nuclides involved in the astrophysical r process are often too challenging to produce at accelerator facilities. Recently the CARIBU facility, an upgrade to Argonne National Laboratory's ATLAS facility, has started to provide intense beams of a number of these previously elusive neutron-rich nuclei. A program of mass measurements at CARIBU is now underway with the Canadian Penning trap mass spectrometer. In addition, a specially designed ion trap is currently being developed to facilitate a new program of beta-decay spectroscopy using nuclides produced by CARIBU. This new technique of using ion traps to perform beta-decay studies could significantly advance the field, just as ion traps had done in the field of mass spectroscopy. The ion trapping techniques and the results/implications of some of the first measurements will be presented.

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