Dynamic stabilization of the magnetic field surrounding the neutron electric dipole moment spectrometer at the Paul Scherrer Institute

Abstract

33 pages, 18 figuresThe Surrounding Field Compensation (SFC) system described in this work is installed around the four-layer Mu-metal magnetic shield of the neutron electric dipole moment spectrometer located at the Paul Scherrer Institute. The SFC system reduces the DC component of the external magnetic field by a factor of about 20. Within a control volume of approximately 2.5m x 2.5m x 3m disturbances of the magnetic field are attenuated by factors of 5 to 50 at a bandwidth from $10^{-3}$ Hz up to 0.5 Hz, which corresponds to integration times longer than several hundreds of seconds and represent the important timescale for the nEDM measurement. These shielding factors apply to random environmental noise from arbitrary sources. This is achieved via a proportional-integral feedback stabilization system that includes a regularized pseudoinverse matrix of proportionality factors which correlates magnetic field changes at all sensor positions to current changes in the SFC coils

Dual atomic interferometer with a tunable point of minimum magnetic sensitivity

“…1. The pulse duration (τ ) determines the fractional population of atoms in the two photon (P = sin 2 [Ω p τ /2]) and clock (1 − P ) interferometers. The state after the preparation pulse is given by…”

“…Magnetic fluctuations are a common source of decoherence in quantum information applications [13,14]. The choice of the proper transition and the use of active feedback or magnetic shielding helps minimizing these noise contributions [2,15,16]. Atomic clocks, for example, use the so called clock transition that connects levels with no linear Zeeman effect.…”

“…Atoms can be configured as magnetometers that achieve sensitivity slightly better than other available technologies [1]. These sensors have been used to achieve magnetic noise free regions [2][3][4][5], to study biomagnetism [6,7], to generate squeezing in spin systems [8][9][10] or to look for physics beyond the Standard Model [11,12].…”

Active compensation of magnetic field distortions based on vector spherical harmonics field description

“…The first one is used in the neutron Electric Dipole Moment spectrometer installed at the Paul Scherrer Institute, Villigen, Switzerland 1,8 ). The system consists of three pairs of rectangular coils as shown in blue in Figure 6.…”

“…Active field compensation utilizing threedimensional Helmholtz-like coil systems were applied e.g. in MiniCLEAN, 6 LIPSION 7 and nEDM 8 experiments.…”