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Simulations of the image charge effect in high-precision Penning traps and the new IGISOL ion buncher


Schuh,  Marc
Division Prof. Dr. Klaus Blaum, MPI for Nuclear Physics, Max Planck Society;

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Schuh, M. (2019). Simulations of the image charge effect in high-precision Penning traps and the new IGISOL ion buncher. PhD Thesis, Ruprecht-Karls-Universität, Heidelberg.

Cite as: https://hdl.handle.net/21.11116/0000-0003-CC4E-1
Penning traps are currently the most precise mass measurement devices resulting from a
long development, which started around 1900. With a relative precision of up to 10-12, Penning
traps allow testing of various physical theories by means of mass measurements, such as
quantum electrodynamics (QED), the CPT (charge, parity and time) theorem and theory of
special relativity.
In order to achieve this precision, many devices have to be coordinated and measurements
have to be performed repeatedly. This work presents the basic structure of a newly-developed
Python based control system for the THe-Trap experiment at the Max-Planck-Institute for
Nuclear Physics in Heidelberg, Germany. During the development the focus was placed on
enabling the user to recognize the state of the experiment at just one glance. It is also possible
to control and automate the experiment with external scripts based on Python as well.
High-precision Penning trap experiments worldwide with the above-mentioned precision are
limited among other things by the so-called image charge effect. This effect is caused by the
image charges induced by the ion in the surrounding electrodes of the Penning trap. These
image charges generate an additional electric field, which systematically shifts the frequency
of the ion and thus the measurement result. This thesis presents a numerical calculation of
the image charge effect for various experiments using the finite element method in COMSOL
Multiphysics. The results of the simulation have an uncertainty of 1 % and agree with the
measurement results, which have an uncertainty of about 5 %.
Time-of-flight measurements show their strength in determining the mass of short-lived nuclides
with a half-life of less than 100 ms. Ions are reflected several times to extend the flight distance,
which has given the instruments the name multi-reflection time-of-flight mass spectrometer
(MR-ToF MS). They also serve as fast mass separators. However, MR-Tof MS require ion pulses
with a temporal width of about 100 ns or shorter. In this work, an ion buncher using SIMION
was developed, built, and tested for the IGISOL experiment in Jyväskylä, Finland. During the
test a pulse width of 107 ns could be achieved.