Nuclear astrophysicists strive to understand how the chemical elements that make up our bodies and the world around us were formed, and how stars generate energy.
Humans have been observing the sky above us for millennia, and a wealth of astronomical observations are now available. For their interpretation, however, the astronomical data require sophisticated models of the processes taking place in astronomical objects. These models cannot function without precise input data on the underlying nuclear and atomic processes.
The task of experimental nuclear astrophysicists is to study nuclear properties and reactions in the laboratory, to provide needed input for stellar modelers. The nuclear physics topics to be addressed in these experiments are selected in close collaboration with modelers and observers, making nuclear astrophysics a truly interdisciplinary enterprise.
Science agenda and available tools
The science agenda of HZDR nuclear astrophysics work is driven by the NuSTAR branch of FAIR. Consequently, experiments at GSI and detector development for FAIR are its pillars. In addition, several of the experimental facilities locally available at HZDR are being used for related work. Facilities used include:
- The NuSTAR branch of GSI, as preparation for the upcoming NuSTAR branch of FAIR.
- The 3MV Tandetron of the HZDR ion beam center, for in-beam gamma-spectrometry with a proton and an a-beam.
- The Felsenkeller low-level gamma-counting facility, for activation experiments.
- The world's only underground accelerator, the LUNA 400 kV machine in the Gran Sasso laboratory in Italy (review paper).
- The photoactivation facility of the ELBE 40 MeV superconducting electron linac, for activation experiments (external users only).
- The photon scattering setup at the ELBE 40 MeV superconducting electron linac, for studies of the photon strength function (now reoriented to transmutation-oriented experiments, nuclear astrophysics related experiments possible for external users).
Theoretical studies address the impact of selected nuclear reactions on astrophysics.
Recent results and ongoing projects
Topics recently addressed include:
- Nuclear fusion reactions in the Sun. HZDR scientists recently contributed to the study of three nuclear reactions that are important for our Sun, namely the 3He(α,γ)7Be (paper), 7Be(p,γ)8B (paper), and 14N(p,γ)15O (papers here, here, and here) reactions. The state of the art is summarized in the Reviews of Modern Physics, in a paper co-authored by HZDR scientists.
- Nucleosynthesis during the Big Bang, in the very first minutes of the universe. HZDR scientists studied the 2H(α,γ)6Li reaction important for Big Bang 6Li production by Coulomb dissociation at GSI Darmstadt (paper), and now address it in a direct experiment at LUNA.
- Nucleosynthesis in explosive environments. HZDR scientists participated in an experiment at the GSI Darmstadt radioactive ion beam facility on light-element nucleosynthesis in a neutron-rich environment. HZDR scientists study the production and destruction of the key supernova isotope 44Ti by direct in-beam experiments. HZDR plays a key role in the LUNA experiment on the 22Ne(p,γ)23Na reaction, important for hydrogen burning in an astrophysical nova.
- The series of in-house photoactivation experiments for the astrophysical p-process at HZDR (papers here, here, and here) has ended, and the photoactivation facility is now open to external users.
- A possible upgrade of the Felsenkeller underground facility in Dresden is presently under discussion. A feasibility study has shown that an ion accelerator in this low-background environment can produce uniquely precise data on astrophysically relevant cross sections (paper).
Collaborations, international recognition, and funding
All nuclear astrophysics related work at HZDR is done in close collaboration with the local university TU Dresden (group of Prof. Dr. Kai Zuber). HZDR is included in the two major European collaborations of the field, namely the NAVI Nuclear Astrophysics Virtual Institute funded by the Helmholtz Association (2011-2016, full partner) and the EuroGENESIS EuroCORES network (2011-2013, associated partner). HZDR is also involved in the ATHENA networking activity for nuclear astrophysics within the FP7-ENSAR project.
HZDR has recently organized or co-organized three widely recognized conferences in the field:
- In 2007, the third edition of the highly successful "Nuclear Physics in Astrophysics" series of Europhysics Conferences was organized by HZDR in Dresden. The sixth edition of this conference will take place in Lisbon/Portugal in May 2013.
- In 2010, the highly topical workshop on "Underground nuclear-reaction experiments for astrophysics and applications" co-organized by HZDR and TU Dresden helped shape the recommendations of the NuPECC long range plan for Nuclear Physics in Europe. It also started a series of meetings, the third edition will take place in Canfranc/Spain in March 2012.
- In 2012, the WE Heraeus seminar on "Astrophysics with modern small-scale accelerators" is co-organized by HZDR scientist D. Bemmerer.
The nuclear astrophysics work at HZDR is largely funded by external, peer-reviewed grants. Currently running grants are from DFG (Big Bang and supernova nucleosynthesis), HGF-NAVI (nuclear physics of the Sun), and BMBF (detector development for FAIR). Our collaborators at TU Dresden have closely related, additional running projects from GSI F&E (detector development for FAIR) and from NupNET (SiPM development for FAIR).
Possible topics for Bachelor's, Master's, and PhD theses
Possible nuclear astrophysics related topics for Bachelor's, Master's, and PhD theses can be found in all the research topics listed above. These topics include
- Experiments with light-ion beams at HZDR and at LUNA, on the nuclear physics of the Sun, or on nucleosynthesis in the Big Bang or in a supernova. More details here.
- Experiments with radioactive ion beams at the NuSTAR branch of GSI/FAIR, on the creation of chemical elements in the astrophysical r-process (rapid neutron capture process).
Also topics for HZDR summer students can be provided.