N. J. Ayres

ETH Zurich

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K. Kirch

Paul Scherrer Institute

P. Schmidt-Wellenburg

Paul Scherrer Institute

F. M. Piegsa

University of Bern

G. Bison

Paul Scherrer Institute

W. C. Griffith

University of Sussex

S. Roccia

Laboratoire de Physique Subatomique et de Cosmologie

J. Zejma

Jagiellonian University

K. Bodek

Institute of Physics

B. Lauss

Paul Scherrer Institute

D. Ries

Paul Scherrer Institute

Cooperative Institutions

Paul Scherrer Institute

110

ETH Zurich

Centre National de la Recherche Scientifique

École Nationale Supérieure d'Ingénieurs de Caen

Institut National de Physique Nucléaire et de Physique des Particules

KU Leuven

Laboratoire de Physique Corpusculaire de Caen

University of Sussex

Johannes Gutenberg University Mainz

Institut Laue-Langevin

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Improved search for neutron to mirror-neutron oscillations in the presence of mirror magnetic fields with a dedicated apparatus at the PSI UCN source

arXiv (Cornell University) (2021)

N. J. Ayres Zurab Berezhiani R. Biondi G. Bison K. Bodek

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 ($\tau_{nn'}$). 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\,m$^3$), 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 a sensitivity to oscillation times $\tau_{nn'}/\sqrt{\cos(\beta)}$ well above hundred seconds, with $\beta$ 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.

Ultracold neutrons

Oscillation (cell signaling)

10.48550/arxiv.2111.02794

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Observation of Gravitationally Induced Vertical Striation of Polarized Ultracold Neutrons by Spin-Echo Spectroscopy

Physical Review Letters (2015)

S. Afach N. J. Ayres G. Ban G. Bison K. Bodek

We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a $|B_0|=1~\text{\mu T}$ magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCN of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of $1.1~\text{pT/cm}$. This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime.

Ultracold neutrons

Larmor precession

Dephasing

Striation

10.1103/physrevlett.115.162502

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

Review of Scientific Instruments (2022)

N. J. Ayres G. Ban G. Bison K. Bodek В. М. Бондар

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 2.92m, thus providing an accessible space of 25m3. The MSR has 87 openings up to 220mm diameter to operate the experimental apparatus inside, and an intermediate space between the layers for sensitive signal processing electronics. The characterization measurements show a remanent magnetic field in the central 1m3 below 100pT, and a field below 600pT 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 2muT peak-to-peak signal is about 100,000 in all three spatial directions and rises fast with frequency to reach 10^8 above 1Hz.

Shielded cable

SIGNAL (programming language)

10.1063/5.0101391

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A large ‘Active Magnetic Shield’ for a high-precision experiment

The European Physical Journal C (2023)

C. Abel N. J. Ayres G. Ban G. Bison K. Bodek

We present a novel Active Magnetic Shield (AMS), designed and implemented for the n2EDM experiment at the Paul Scherrer Institute. The experiment will perform a high-sensitivity search for the electric dipole moment of the neutron. Magnetic-field stability and control is of key importance for n2EDM. A large, cubic, 5 m side length, magnetically shielded room (MSR) provides a passive, quasi-static shielding-factor of about 105 for its inner sensitive volume. The AMS consists of a system of eight complex, feedback-controlled compensation coils constructed on an irregular grid spanned on a volume of less than 1000 m3 around the MSR. The AMS is designed to provide a stable and uniform magnetic-field environment around the MSR, while being reasonably compact. The system can compensate static and variable magnetic fields up to ±50μT (homogeneous components) and ±5μT/m (first-order gradients), suppressing them to a few μT in the sub-Hertz frequency range. The presented design concept and implementation of the AMS fulfills the requirements of the n2EDM experiment and can be useful for other applications, where magnetically silent environments are important and spatial constraints inhibit simpler geometrical solutions.

Shielded cable

10.1140/epjc/s10052-023-12225-z

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Gravitational depolarization of ultracold neutrons: Comparison with data

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2015)

S. Afach N. J. Ayres C.A. Baker G. Ban G. Bison

We compare the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons to measurements carried out in a spin-precession chamber exposed to a variety of vertical magnetic-field gradients. In particular, we have investigated the dependence upon these field gradients of spin-depolarization rates and also of shifts in the measured neutron Larmor precession frequency. We find excellent qualitative agreement, with gravitationally enhanced depolarization accounting for several previously unexplained features in the data.Received 22 June 2015DOI:https://doi.org/10.1103/PhysRevD.92.052008© 2015 American Physical Society

Ultracold neutrons

Larmor precession

Precession

10.1103/physrevd.92.052008

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Measurement of the Permanent Electric Dipole Moment of the Neutron

Physical Review Letters (2020)

C. Abel S. Afach N. J. Ayres C.A. Baker G. Ban

We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons (UCN). Our measurement stands in the long history of EDM experiments probing physics violating time reversal invariance. The salient features of this experiment were the use of a Hg-199 co-magnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic field changes. The statistical analysis was performed on blinded datasets by two separate groups while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is $d_{\rm n} = (0.0\pm1.1_{\rm stat}\pm0.2_{\rm sys})\times10^{-26}e\,{\rm cm}$.

Ultracold neutrons

Neutron magnetic moment

10.1103/physrevlett.124.081803

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Spin-echo spectroscopy with ultracold neutrons

arXiv (Cornell University) (2015)

S. Afach N. J. Ayres G. Ban G. Bison K. Bodek

We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B_0 | = 1uT magnetic field. We demonstrate a gravity-dependent spin dephasing by applying small vertical magnetic field gradients. The method gives access to the energy spectrum of stored UCNs, which can be crucial for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron.

Ultracold neutrons

Dephasing

Neutron spin echo

Source

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nEDM experiment at PSI: Data-taking strategy and sensitivity of the dataset

EPJ Web of Conferences (2019)

C. Abel N. J. Ayres G. Ban G. Bison K. Bodek

We report on the strategy used to optimize the sensitivity of our search for a neutron electric dipole moment at the Paul Scherrer Institute. Measurements were made upon ultracold neutrons stored within a single chamber at the heart of our apparatus. A mercury cohabiting magnetometer together with an array of cesium magnetometers were used to monitor the magnetic field, which was controlled and shaped by a series of precision field coils. In addition to details of the setup itself, we describe the chosen path to realize an appropriate balance between achieving the highest statistical sensitivity alongside the necessary control on systematic effects. The resulting irreducible sensitivity is better than 1 × 10 −26 e cm. This contribution summarizes in a single coherent picture the results of the most recent publications of the collaboration.

Ultracold neutrons

10.1051/epjconf/201921902001

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The n2EDM experiment at the Paul Scherrer Institute

EPJ Web of Conferences (2019)

C. Abel N. J. Ayres G. Ban G. Bison K. Bodek

We present the new spectrometer for the neutron electric dipole moment (nEDM) search at the Paul Scherrer Institute (PSI), called n2EDM. The setup is at room temperature in vacuum using ultracold neutrons. n2EDM features a large UCN double storage chamber design with neutron transport adapted to the PSI UCN source. The design builds on experience gained from the previous apparatus operated at PSI until 2017. An order of magnitude increase in sensitivity is calculated for the new baseline setup based on scalable results from the previous apparatus, and the UCN source performance achieved in 2016.

Ultracold neutrons

10.1051/epjconf/201921902002

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Achieving ultra-low and -uniform residual magnetic fields in a very large magnetically shielded room for fundamental physics experiments

The European Physical Journal C (2024)

N. J. Ayres G. Ban G. Bison K. Bodek В. М. Бондар

Abstract High-precision searches for an electric dipole moment of the neutron (nEDM) require stable and uniform magnetic field environments. We present the recent achievements of degaussing and equilibrating the magnetically shielded room (MSR) for the n2EDM experiment at the Paul Scherrer Institute. We present the final degaussing configuration that will be used for n2EDM after numerous studies. The optimized procedure results in a residual magnetic field that has been reduced by a factor of two. The ultra-low field is achieved with the full magnetic-field-coil system, and a large vacuum vessel installed, both in the MSR. In the inner volume of $$\sim 1.4~\hbox {m}^3$$ ∼ 1.4 m 3 , the field is now more uniform and below 300 pT. In addition, the procedure is faster and dissipates less heat into the magnetic environment, which in turn, reduces its thermal relaxation time from $$12~\text {h}$$ 12 h down to $$1.5~\text {h}$$ 1.5 h .

10.1140/epjc/s10052-023-12351-8

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Citations (4)