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MPINP:
Präzisionsexperimente - Abteilung Blaum
Abstract:
The Penning-trap mass spectrometer PENTATRAP aims for measurements of mass ratios
of single stable and long-lived highly-charged ions with a relative uncertainty on the order
of 10−11. For the mass-ratio measurement the cyclotron frequencies are measured for two
ion species inside the magnetic field of the Penning traps. The ions’ eigenfrequencies are
measured by means of a non-destructive detection of image currents. Essential part of each
detection circuit is a cryogenic high-quality (high-Q) resonator, realised as a superconducting
NbTi or copper coil in a copper housing. PENTATRAP incorporates detectors for the axial
and the modified cyclotron mode, which enable direct cooling and detection of these modes.
The tiny image currents induced by a single ion become detectable with the help of cryogenic
GaAs FET amplifiers. Due to a modification of the PENTATRAP setup, a new detection
system is needed. This detection system was developed in the framework of this thesis. The
new detection system features identical housings for the axial and the cyclotron resonators.
Both coil types were designed as toroidal coils. The previous amplifier circuit was adapted to
the new amplifier box. First tests of the resonators, with and without the cryogenic amplifier,
were conducted inside a cryocooler. For a 35Cl10+-ion the final resonators will lead to a dip
width of ~1.73 Hz for a dip detection measurement with the axial resonator at the correction
electrode. With the cyclotron resonator connected to one half of the correction electrode the
expected cooling time constant for this ion is ~36.6 s.
