Speaker
Description
This work is part of the n2EDM experiment located at Paul Scherrer Institut (PSI) in Switzerland. The nEDM measurement principle is based on the use of two precession chambers, one above the other, and separated by a high voltage electrode. Mercury vapour is used as a comagnetometer in order to measure the average magnetic field in the same volume as ultra cold neutrons (UCN). By measuring the Larmor precession frequency of the two species, one can compute the frequency ratio $R=f_n/f_\text{Hg}$ corrected from magnetic field fluctuations.
In this talk, I will present the systematic effect on the $R$-ratio in the presence of a magnetic gradient. This effect is due to the difference in the energy spectra of mercury vapour and UCN. Indeed, since mercury vapour is at room temperature and neutrons are ultra cold, the two species have different height distributions in the chamber. The presence of a vertical magnetic gradient therefore affects the two species differently. The leading induced systematic effect is linear in gradient, but there is also a non linear contribution. I will focus on the use of the energy spectrum of UCN to compute non-linear corrections in the $R$-ratio.