Speaker
Dr
Jochen Krempel
(ETH Zürich)
Description
The measurement of the nEDM requires a magnetic field that is homogeneous in space and stable in time.
This presentation will focus on how to provide and maintain such a field.
Assuming a stable current source and a rigid coil, it is still necessary to have a stable temperature such that the mu-metal keeps its magnetisation.
Furthermore, careful relaxation (about once per day) of the mu-metal is necessary after each change of the orientation of the B-field.
Trim-coils are used to obtain a homogeneous field. Off-line mapping is done to find their optimal setting and to measure residual inhomogeneities in order to correct for systematic effects.
Before entering the mu-metal the neutrons need to be polarized, and then guided with a relatively strong magnetic field in order to keep the polarization. The transition into the weak field in the storage chamber is particularly difficult.
Around the mu-metal shield a surrounding field compensation system consisting of 6 large coils and 30 Fluxgate sensors is installed and suppresses external magnetic fluctuations.
Author
Dr
Jochen Krempel
(ETH Zürich)
Co-author
on behalf of the nEDM collaboration (PSI) -
