The chemical composition of our universe shows some surprising peculiarities: The sun mainly consists of hydrogen and helium; iron is much more abundant on Earth compared to heavy elements like gold. Nucleosynthesis follows reaction paths involving fusion and capture processes, some of them yet mostly unexplained. Since nuclear fusion stops at iron, heavier elements are generated via proton or neutron capture under extreme conditions like in supernova explosions of stars or in hot environments like accretion discs around Black Holes or neutron stars.

Based on Einstein’s principle of mass-energy equivalence, at MPIK high-precision mass measurements of nuclides are used to determine nuclear binding energies which are crucial for reaction pathways in nucleosynthesis.

The direct determination of superheavy nuclide masses bridges the gap to the predicted island of stability by benchmarking theories. In addition, ion-trap or storage-ring mass spectrometers open the possibility to capture and identify new radionuclides. Penning-trap mass measurements led to the discovery of a new radon isotope, ²²⁹Rn. Further, highly precise mass values provide insight into exotic nuclides and reveal structural information like halos (loosely bound nucleons), deformation and shell closures.

Division Blaum

Precision Experiments in Penning Traps: Measurements on Single Ions (pdf)

At MPIK, unique combinations of powerful techniques are applied to control ions and to make them available for precision studies, mostly at very low temperatures.

Ions can be stored in traps by the superposition of electrical and magnetic fields in an extreme vacuum. Penning traps allow storage of a single ion that performs a characteristic oscillating circular motion in the trap. The ion’s mass and further properties can be deduced from the frequency if the charge state and the magnetic field strength are known, even in the case of exotic particles that live only for a few milliseconds. Penning-trap mass spectrometers are operated at MPIK and at radioactive beam facilities like GSI and CERN.

In an electron-beam ion trap (EBIT), highly charged ions are produced by impact of energetic electrons, then spatially confined, and electronically heated up to temperatures of millions of degrees. Both, stationary and mobile EBITs are used to prepare and study atomic matter under extreme conditions. A suite of accurate spectroscopic instrumentation attached to the EBITs collects precise data.

For the research with fast ion beams, the MPIK operates its own accelerator facilities, a part of which has been designed and constructed at the Institute. The MP tandem accelerator with the high-frequency linear postaccelerator as well as the high-current injector and a Van de Graaff generator are able to supply the heavy-ion storage ring TSR with ions of nearly all elements and small molecular ions. The TSR, a magnetic storage ring with 55 m circumference, provides cold ion beams by electron cooling. This enables well-defined preparation of the stored ions to perform precision experiments in atomic and molecular physics. Miscellaneous instruments can be integrated in the experimental section.

The electrostatic cryogenic storage ring, CSR, will allow investigating for the very first time cold molecular ions of any size as well as highly charged ions essentially without any influence of the environment. This is achieved by keeping the ring under extremely low pressure and temperature, a technology previously tested with the cryogenic electrostatic trap (CTF), which is now used as an experimental device to investigate e. g. cluster ions. The innovative mechanical concept of the CSR has been developed and realized in close cooperation with MPIK’s engineering design office and precision mechanics shop.

Division Blaum    Division Ullrich

Precision Experiments in Penning Traps: Measurements on Single Ions (pdf)
Stellar Furnace in the Freezer Box: Highly Charged Ions at 100 Millionen Degrees (pdf)
The TSR Heavy-Ion Storage Ring and the Accelerator Facilities (pdf)
The Cryogenic Storage Ring CSR (pdf)

The basis of modern physics is the theory of elementary particles and their interactions. In the language of quantum field theory electromagnetism is described as the exchange of so-called virtual photons between charged particles. Another consequence of this theory named quantum electrodynamics (QED) is the fact that there is no empty space, i. e. the vacuum is filled with virtual particles. Though their existence is only allowed for a very short time – given by quantum uncertainty – the presence of an average number of virtual particles can be detected by high-precision experiments. At the same time, QED is the to date best tested theory in physics at all.

The effects are most prominent in very strong fields such as inside highly charged ions and can be studied by measuring the binding energy of electrons as well as the lifetime of decaying excited electronic states with extreme precision. At MPIK experiments use trapped ions interacting with electron beams either in an EBIT or in a storage ring (TSR and the future CSR). High-order QED calculations with the emphasis on few-body effects are performed in the theory division in close collaboration with the experimental groups. Other QED effects show up in the magnetic properties of charged particles. Using single ions of light elements with only one electron in a Penning trap, it is possible to determine the magnetic moment of the bound electron very accurately. This allows not only to check precisely the QED predictions for bound states, but vice versa, also to precisely determine fundamental constants like the electron mass.

Division Keitel    Division Blaum    Division Ullrich

Laser-Modified Quantum Electrodynamics, Nuclear and High-Energy Processes (pdf)
Stellar Furnace in the Freezer Box: Highly Charged Ions at 100 Millionen Degrees (pdf)
Precision Experiments in Penning Traps: Measurements on Single Ions (pdf)