Stuttgart 2012 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 6: Poster
MS 6.2: Poster
Dienstag, 13. März 2012, 16:30–19:00, Poster.IV
Magnetic Field stabilization in THe-Trap — •Sebastian Streubel1, Tommi Eronen1, Martin Höcker1, Jochen Ketter1, Robert S. Van Dyck Jr.2, and Klaus Blaum1 — 1Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany — 2Department of Physics, University of Washington, Seattle, WA 98195-1560, USA
THe-Trap is a Penning trap mass spectrometer dedicated to measure the 3H to 3He mass ratio aiming to a relative mass uncertainty better than 10−11. The most vital prerequisite for this measurement is a stable magnetic field: The relative temporal fluctuations during a measurement cycle of typically 1 hour, should be better than 10−11. The 5.26 T field is provided by a superconducting magnet. Unfortunately, the materials within the cryostat have a temperature-dependent susceptibility which necessitates a temperature stabilization. The stabilization is achieved by controlling the liquid helium level above the traps, and by keeping the pressure of the liquid helium constant. An important part of the system is the pressure reference, which is stable at a 0.04 Pa level.
In addition to the stabilization of the field fluctuations within the cryostat itself, a system to cancel external fluctuations is set up consisting of a passive coil with a shielding factor of up to 180 build into the cryostat. Furthermore, a Helmholtz coil pair is placed around the cryostat. The compensation signal is provided by a custom-built flux-gate magnetometer.
Technical details about the stabilization systems will be given.