Abstract
This article is designed as a step-by-step guide to optically pumped magnetometers based on alkali atomic vapor cells. We begin with a general introduction to atomic magneto-optical ...response, as well as expected magnetometer performance merits and how they are affected by main sources of noise. This is followed by a brief comparison of different magnetometer realizations and an overview of current research, with the aim of helping readers to identify the most suitable magnetometer type for specific applications. Next, we discuss some practical considerations for experimental implementations, using the case of an
M
z
magnetometer as an example of the design process. Finally, an interactive workbook with real magnetometer data is provided to illustrate magnetometer-performance analysis.
While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of ...hypothetical neutron (n) to mirror-neutron (n′) transitions, it could not test all claimed signal regions at various mirror magnetic fields. Therefore, a new study of n−n′ oscillations using stored ultracold neutrons (UCNs) is underway at PSI, considerably expanding the reach in parameter space of mirror magnetic fields (B′) and oscillation time constants (τnn′). The new apparatus is designed to test for the anomalous loss of stored ultracold neutrons as a function of an applied magnetic field. The experiment is distinguished from its predecessors by its very large storage vessel (1.47 m3), enhancing its statistical sensitivity. In a test experiment in 2020 we have demonstrated the capabilities of our apparatus. However, the full analysis of our recent data is still pending. Based on already demonstrated performance, we will reach sensitivity to oscillation times τnn′/cos(β) well above a hundred seconds, with β being the angle between B′ and the applied magnetic field B. The scan of B will allow the finding or the comprehensive exclusion of potential signals reported in the analysis of previous experiments and suggested to be consistent with neutron to mirror-neutron oscillations.
We present a laser-based atomic magnetometer that allows inferring the modulus of a magnetic field from the free Larmor precession of spin-oriented Cs vapour atoms. The detection of free spin ...precession (FSP) is not subject to systematic readout errors that occur in phase feedback-controlled magnetometers in which the spin precession is actively driven by an oscillating field or a modulation of light parameters, such as frequency, amplitude, or polarization. We demonstrate that an FSP-magnetometer can achieve a ∼200 fT/√Hz sensitivity (<100 fT/√Hz in the shotnoise limit) and an absolute accuracy at the same level.
Graphical abstract
Zusammenfassung
Warum blieb nach dem Urknall nur Materie übrig? Dies ist eine der großen ungelösten Fragen der Physik. Eine mutmaßliche Ursache könnte eine starke Verletzung der sogenannten ...CP‐Symmetrie gewesen sein. Nach allgemeinen Prinzipien der Teilchenphysik müsste diese allerdings zu einem messbaren elektrischen Dipolmoment (EDM) von Elementarteilchen führen. Neutronen sind für die Suche nach EDMs besonders gut geeignet. Neue präzisere Daten lieferte jetzt das nEDM‐Experiment am Paul Scherrer Institut. Es senkte den Grenzwert für ein EDM von Neutronen erheblich. Der neue Messwert verschärft somit die Bedingungen für neue Theorien, die das Standardmodell erweitern. Der im Aufbau befindliche Nachfolger n2EDM soll 2022 in Betrieb gehen und als Ziel das Neutronen‐EDM zehnfach genauer bestimmen.
Warum blieb nach dem Urknall keine Antimaterie übrig? Dies ist eine der großen ungelösten Fragen der Physik. Eine mutmaßliche Ursache könnte eine starke Verletzung der sogenannten CP‐Symmetrie gewesen sein. Nach allgemeinen Prinzipien der Teilchenphysik müsste diese allerdings zu einem messbaren elektrischen Dipolmoment von Elementarteilchen führen. Neutronen sind für eine solche Messung besonders gut geeignet, erfordern aber hochempfindliche Präzisionsexperimente.
Zusammenfassung
Warum blieb nach dem Urknall nur Materie übrig? Dies ist eine der großen ungelösten Fragen der Physik. Eine mutmaßliche Ursache könnte eine starke Verletzung der sogenannten ...CP‐Symmetrie gewesen sein. Nach allgemeinen Prinzipien der Teilchenphysik müsste diese allerdings zu einem messbaren elektrischen Dipolmoment (EDM) von Elementarteilchen führen. Neutronen sind für die Suche nach EDMs besonders gut geeignet. Neue präzisere Daten lieferte jetzt das nEDM‐Experiment am Paul Scherrer Institut. Es senkte den Grenzwert für ein EDM von Neutronen erheblich. Der neue Messwert verschärft somit die Bedingungen für neue Theorien, die das Standardmodell erweitern. Der im Aufbau befindliche Nachfolger n2EDM soll 2022 in Betrieb gehen und als Ziel das Neutronen‐EDM zehnfach genauer bestimmen.
We demonstrate the use of a hybrid
3
He/
87
magnetometer to measure absolute magnetic fields in the pT range. The measurements were undertaken by probing time-dependent
3
He magnetisation using
87
Rb ...zero-field magnetometers. Measurements were taken to demonstrate the use of the magnetometer in cancelling residual fields within a magnetic shield. It was shown that the absolute field could be reduced to the 10 pT level by using field readings from the magnetometer. Furthermore, the hybrid magnetometer was shown to be applicable for the reduction of gradient fields by optimising the effective
3
He
T
2
time. This procedure represents a convenient and consistent way to provide a near zero magnetic field environment which can be potentially used as a base for generating desired magnetic field configurations for use in precision measurements.
Graphical abstract
We present a magnetic field confining coil with a sub-10 -3 field uniformity over a large fraction of the coil. The structure is entirely made out of printed circuit boards (PCBs). The PCB design ...allows the path of the wires to be tailored to fit the required geometry. We measure the field uniformity with cesium magnetometers in a field range from 1 to 10 μT. Our application uses such a coil for an atomic magnetometry-based current controller.
We describe a method for recording the Rabi nutation of nuclear spin polarized
3
He by optically pumped cesium magnetometers. The measurement is performed by detecting the time-dependent magnetic ...field produced by the
3
He magnetization. The observed signals are compared to theoretical models and the results are used to precisely trace the evolution of the magnetization. This procedure represents a convenient way to control and measure the Rabi flip angle and the degree of spin polarization in experiments using
3
He magnetometers. The method requires only very coarse knowledge of the applied magnetic field’s magnitude.
Graphical abstract
We report on extensive studies on the intrinsic sensitivity of a combined
3
He/Cs magnetometer. The magnetometer relies on the detection of the free spin precession of nuclear spin polarized
3
He by ...optically pumped cesium magnetometers. We characterize the relevant processes involved in the detection and quantify their impact on the total sensitivity of the magnetometer. An expression is derived that predicts the sensitivity of this magnetometer scheme and the results are compared to experiments. Excellent agreement is found between theory and experiments, and implications for an application of a
3
He/Cs magnetometer in an experiment searching for a permanent neutron electric dipole moment are discussed.
Graphical abstract
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