Ph. D. Thesis: The Penning trap mass spectrometer SMILETRAP II and evaporative cooling of highly-charged ions
by
Matthias Hobein(Stockholm University, Department of Physics)
→
Europe/Stockholm
FA32
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Description
Accurate mass values have wide-ranging applications in physics and metrology, allowing, for
example, to test quantum electrodynamics and fundamental symmetries, to determine fundamental
constants, and to establish weight standards.
This thesis describes the new high-precision double-Penning trap mass spectrometer
SMILETRAP II which aims at relative uncertainties in the mass determination of 10-10 and below.
SMILETRAP II exploits the merits of highly-charged ions as the relative precision in the mass
determination with Penning traps is directly proportional to the charge state of the ion. The
spectrometer was therefore connected to the electron beam ion trap S-EBIT which is designed to
produce bare ions of practically any element up to uranium.
Technical and experimental developments were realized to overcome limitations that restricted
the achievable precision at the former spectrometer SMILETRAP I. The technical developments
include, for example, an ion detection setup with close to 100% efficiency and an extremely
stable temperature-regulation system. Temperature fluctuations constitute a main limitation for the
attainable precision.
Cold ions are a prerequisite to reach high precision in experiments with Penning traps. This
makes cooling of the ions from the ion sources necessary. Ion temperature measurement and cooling
experiments were performed. The transverse temperature of the trapped ions was determined
via the emittance of extracted ions. A pepperpot emittance meter was designed to meet the
requirements of low-energy, low-intensity beams. To measure the axial temperature and assess
the ions’ longitudinal phase-space density, a coherent extraction method was developed. The
evaporative cooling technique was successfully implemented. In particular, evaporative cooling of
highly-charged ions in a Penning trap could be observed for the first time.