Exotic Nuclei - AG Nörtershäuser

Exotic Nuclei

Nuclear Chart with Laser Spectroscopy
Nuclear Chart with Laser Spectroscopy

The atomic spectrum contains information about the properties and structure of the nucleus. Resonances of different isotopes appear for example at slightly different frequencies due to redistribution of the nuclear charge, i.e. the protons, when additional neutrons are added. The charge radius of nuclei can be extracted from these shifts. Moreover, an additional splitting of resonance lines, – the hyperfine structure – allows the determination of the nucleus’ spin, its magnetic moments and about its deformation. Measuring these properties along a chain of isotopes allows us to understand the interactions among the constituents of the nucleus. Such experiments become very challenging when it comes to isotopes far away from the valley of β-stability, where nuclei can be produced only in minute quantities and their lifetime is reduced to only a few milliseconds. Collinear laser spectroscopy is an established tool to study these properties and several detection techniques have been adopted during the last decades to increase accuracy and sensitivity in order to explore more and more exotic regions of the nuclear chart. Currently we apply or plan collinear laser spectroscopy at the following facilities in cooperation with international partners.

COLLAPS @ ISOLDE (CERN)

COLLAPS Collaboration Meeting 2017
COLLAPS Collaboration Meeting 2017

ISOLDE is an isotope production facility at Europe’s largest accelerator laboratory CERN. It is one of the world’s leading facility in producing short-lived isotopes at low energies as they are required for collinear laser spectroscopy The COLLAPS setup, installed in the experimental hall at ISOLDE, is the “senior” of such experiments and, nevertheless, still one of the most productive’s of its kind. Operation is expected to start again soon, after the 1,5-years shutdown of ISOLDE, once the installation of our new laser laboratory is finished. Stay tuned to learn about new results from there ….
COLLAPS is a collaboration oft the MPIK in Heidelberg, the Johannes Gutenberg University in Mainz, the TU Darmstadt and the KU Leuven. The local team at CERN currently consists of the following persons: Dr. Hanne Heylen, Dr. Mark Bissel, Dr. Stephan Ettenauer, Dr. Magdalena Kowalska, Dr. Ronald Garcia-Ruiz and Dr. Xiaofei Yang.

TRIGA-LASER @ Mainz and LASPEC @ FAIR

TRIGA-SPEC at the Research Reactor TRIGA Mainz
TRIGA-SPEC at the Research Reactor TRIGA Mainz

The collinear laser spectroscopy setup TRIGA-LASER at the research reactor TRIGA Mainz is the development platform for the LASPEC Experiment at the upcoming FAIR facility of which the construction just started in Darmstadt. Here the super fragment separator (S-FRS) will produce worldwide unique beams of short lived isotopes. Until the FAIR facility is completed we are using the research reactor TRIGA Mainz at the institute for nuclear chemistry of the Johannes Gutenberg-University. By neutron induced fission of U-235 and Cf-249 we can access short lived isotopes for spectroscopy. The extraction of the short-lived isotopes from the reactor and the transport to the TRIGA-LASER and TRIGA-TRAP experiments is currently developed within the TRIGA-SPEC collaboration.
The TRIGA-LASER team in Mainz currently consists of Christian Gorges and Simon Kaufmann.

TRIUMF @ Vancouver

The laser spectroscopy beamline at TRIUMF (taken from http://www.triumf.ca/laser-spectroscopy)
The laser spectroscopy beamline at TRIUMF (taken from http://www.triumf.ca/laser-spectroscopy)

At TRIUMF in Vancouver we were able to determine for the first time the charge radius of the halo nucleus lithium-11. For this, we did not use collinear laser spectroscopy but a very dedicated technique that combined high-resolution Doppler-free two-photon spectroscopy and resonance ionization. In the future we will start to carry out collinear spectroscopy together with the local group at TRIUMF. We are looking for a doctoral student, committed to push this experiment and to stay for a significant part of his project time at the west coast of Canada.

Argonne National Laboratory @ Argonne

Expected production rates at CARIBU (taken from http://www.phy.anl.gov/atlas/caribu/ATLAS_Cf_upgrade.pdf)
Expected production rates at CARIBU (taken from http://www.phy.anl.gov/atlas/caribu/ATLAS_Cf_upgrade.pdf)

At the Argonne National Laboratory (ANL) we plan experiments at the ATLAS accelerator as well as at the new CARIBU facility. A new collinear laser spectroscopy beamline will be established in collaboration with the working group of Peter Müller in the Low Energy Group at ANL. The goal is to determine the nuclear charge radius of the proton-halo nucleus boron-8 at the ATLAS facility and to perform collinear laser spectroscopy on short-lived fission products of Californium-249 at CARIBU.
These projects have been initiated in the frame of the new Collaborative research Centre (Sonderforschungsbereich) SFB 1245 and are supported by DFG.

BECOLA @ NSCL

Im Rahmen des SFB 1245 engagieren wir uns auch am BECOLA Experiment (BEam COoler and LAser spectroscopy facility) am National Superconducting Cyclotron Laboratory. Hier gibt es bereits eine langjährige Zusammenarbeit, die in den kommenden Jahren intensiviert werden soll. So sind wir beispielsweise in den Aufbau eines neuen Fluoreszensnachweises an BECOLA involviert, mit dem die Nachweiseffizienz insbesondere bei der Spektroskopie an Ionen gesteigert werden soll. Ein erster Einsatz ist für den Sommer 2017 geplant.