The BeamEDM experiment and the measurement of the neutron incoherent scattering length of 199Hg

BeamEDM is a proof-of-principle apparatus to search for a neutron electric dipole moment using a cold neutron beam with a combined Ramsey and time-of-flight technique. Employing a time-of-flight is essential, as it allows to distinguish the v × E systematic effect from an electric dipole moment signal. To date, four beamtimes have been performed both at the Paul Scherrer Institute in Switzerland and at the Institute Laue-Langevin in France. The first part of this thesis presents the development of the apparatus and the measurements performed over the different beamtimes. The nEDM experiment at the Paul Scherrer Institute uses ultra-cold neutrons to measure an electric dipole moment. It requires the use of a mercury co-magnetometer to monitor the magnetic field that the ultra-cold neutrons are probing. Both species can interact with each other via the neutron incoherent scattering length of mercury. This interaction takes the form of a shift in the neutron precession frequency whose sign depends on the mercury atoms' polarization. As the sign of the incoherent scattering length is unknown, the induced shift could be the cause of a systematic effect in the case of a neutron electric dipole measurement. The second part of this thesis details the apparatus, measurement, analysis, and result that has determined the sign of the incoherent scattering length of 199 Hg

New Limit on Axion-Dark-Matter using Cold Neutrons

We report on a search for axion-like dark matter using a Ramsey-type apparatus for cold neutrons. A hypothetical axion-gluon-coupling would manifest in a neutron electric dipole moment signal oscillating in time. Twenty-four hours of data have been analyzed in a frequency range from 23 $\mu$Hz to 1 kHz, and no significant oscillating signal has been found. The usage of present axion and dark-matter models allowed excluding the coupling of axions to gluons in the mass range from $1.5 \times 10^{-20}$ to $6.6 \times 10^{-13}$ eV with a best sensitivity of $C_G / f_a m_a = (3.1 \pm 0.2) \times 10^{12}$ GeV$^{-2}$ (95% C.L.)

The pulsed neutron beam EDM experiment

We report on the Beam EDM experiment, which aims to employ a pulsed cold neutron beam to search for an electric dipole moment instead of the established use of storable ultracold neutrons. We present a brief overview of the basic measurement concept and the current status of our proof-of-principle Ramsey apparatus

New Limit on Axion-Like Dark Matter using Cold Neutrons

We report on a search for dark matter axion-like particles (ALPs) using a Ramsey-type apparatus for cold neutrons. A hypothetical ALP-gluon-coupling would manifest in a neutron electric dipole moment signal oscillating in time. Twenty-four hours of data have been analyzed in a frequency range from 23 $\mu$Hz to 1 kHz, and no significant oscillating signal has been found. The usage of present dark-matter models allows to constrain the coupling of ALPs to gluons in the mass range from $10^{-19}$ to $4 \times 10^{-12}$ eV. The best limit of $C_G$/$f_a m_a = 2.7 \times 10^{13}$ GeV$^{-2}$ (95% C.L.) is reached in the mass range from $2 \times 10^{-17}$ to $2 \times 10^{-14}$ eV

The very large n2EDM magnetically shielded room with an exceptional performance for fundamental physics measurements

We present the magnetically shielded room (MSR) for the n2EDM experiment at the Paul Scherrer Institute, which features an interior cubic volume with each side of length 2.92 m, thus providing an accessible space of 25 m3. The MSR has 87 openings of diameter up to 220 mm for operating the experimental apparatus inside and an intermediate space between the layers for housing sensitive signal processing electronics. The characterization measurements show a remanent magnetic field in the central 1 m3 below 100 pT and a field below 600 pT in the entire inner volume, up to 4 cm to the walls. The quasi-static shielding factor at 0.01 Hz measured with a sinusoidal 2 μT peak-to-peak signal is about 100 000 in all three spatial directions and increases rapidly with frequency to reach 108 above 1 Hz.ISSN:0034-6748ISSN:1089-762

Mapping of the magnetic field to correct systematic effects in a neutron electric dipole moment experiment

Experiments dedicated to the measurement of the electric dipole moment of the neutron require outstanding control of the magnetic-field uniformity. The neutron electric dipole moment (nEDM) experiment at the Paul Scherrer Institute uses a Hg199 co-magnetometer to precisely monitor temporal magnetic-field variations. This co-magnetometer, in the presence of field nonuniformity, is, however, responsible for the largest systematic effect of this measurement. To evaluate and correct that effect, offline measurements of the field nonuniformity were performed during mapping campaigns in 2013, 2014, and 2017. We present the results of these campaigns, and the improvement the correction of this effect brings to the neutron electric dipole moment measurement.ISSN:1094-1622ISSN:0556-2791ISSN:1050-294

Erratum to: Data blinding for the nEDM experiment at PSI

ISSN:1434-6001ISSN:1434-601