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Projects

MASSPASS — Academy Fellowship (PI), 2023–2027 #

Mass measurements of exotic N = Z nuclei up to ¹⁰⁰Sn and the vicinity for nuclear physics and nuclear astrophysics, at IGISOL and RIKEN. Research Council of Finland. Project page

Team: Z. Ge (PI); former postdoc Dr. B. Kootte; PhD student M. Winter.

Low-Q-value decays for neutrino-mass determination #

Penning-trap Q-value measurements at JYFLTRAP to find and verify ultra-low-Q β⁻ and electron-capture transitions.

Team: Z. Ge (spokesperson); former postdoc Dr. M. de Oliveira Ramalho (theory); PhD student M. Winter.

MR-TOF mass spectrometry #

Design, ion-optical simulation and analysis pipelines for multi-reflection time-of-flight spectrometers.

RFQ cooler-bunchers and beam preparation #

Ion-optical design of radiofrequency quadrupole coolers for cold, bunched radioactive beams.

Detectors for storage rings #

Timing and position-sensitive MCP detectors for the Rare-RI Ring (RIKEN) and concepts for HIAF.

Research software #

Penning-trap particle simulation, MR-TOF calibration and 2D MCP position calibration tools in Python.

Explore the research tools #

  • Mass measurements and low-Q decays: Open the nuclear chart and chain plots . Compare AME2020 with the available mass models; enter ME, total binding energy or atomic mass, inspect affected neighbours and compare residuals. Start with the clearly labelled synthetic example; entered values are not automatically certified experimental results.
  • MR-TOF and double-trap methods: Try the measurement games . Original, Advanced and Fancier tabs connect motion, calibration and simulated detector observations. These are teaching tools; their results do not validate laboratory hardware.
  • Follow up a calculation: Browse data sources , related publications and facility information . Each selected mass model links its source data and paper directly from the Lab controls.

Scientific context of the projects #

MASSPASS. Masses along the N = Z line give the two-proton and two-neutron separation energies and the pairing and Wigner contributions to the binding energy, and they test shell evolution towards ¹⁰⁰Sn. For the rp-process they provide the reaction Q-values that determine how far the Sn–Sb–Te cycle extends. The nuclei are produced with the IGISOL technique, mass-separated, cooled and bunched in an RFQ and measured with JYFLTRAP and the MR-TOF spectrometer.

Low-Q decays. The aim is a list of reliable candidates for future direct neutrino-mass experiments: for each transition the decay energy is measured with a precision of a few hundred eV or better, and excited-state energies are checked against nuclear-structure data.

MR-TOF spectrometry. Work covers ion-optical simulations (SIMION), the time-of-flight calibration with reference ions (m/q ∝ (t − t0)2), peak-shape fitting and the conversion of frequency or time ratios into atomic masses and mass excesses.

RFQ cooler-bunchers. In a radiofrequency quadrupole filled with helium, the RF field confines the ions radially while collisions cool them; a weak axial DC gradient guides them to a potential well from which short, low-emittance bunches are released for trap injection.

Detectors for storage rings. In isochronous mass spectrometry the revolution time of a stored ion depends on its mass-to-charge ratio; a ring operated at the transition energy cancels the first-order dependence on the velocity. Thin-foil timing detectors with micro-channel plates measure the revolution times with sub-nanosecond resolution.

Research software. Python codes integrate the equations of motion of ions in Penning traps including ion–ion Coulomb interaction, calibrate MR-TOF spectra with reference ions, and correct the position distortions of two-dimensional MCP detectors.