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Université de Fribourg

Magnetic-field uniformity in neutron electric-dipole-moment experiments

Abel, C. ; Ayres, N. J. ; Baker, T. ; Ban, G. ; Bison, G. ; Bodek, K. ; Bondar, V. ; Crawford, C. B. ; Chiu, P.-J. ; Chanel, E. ; Chowdhuri, Z. ; Daum, M. ; Dechenaux, B. ; Emmenegger, S. ; Ferraris-Bouchez, L. ; Flaux, P. ; Geltenbort, P. ; Green, K. ; Griffith, W. C. ; Grinten, M. van der ; Harris, P. G. ; Henneck, R. ; Hild, N. ; Iaydjiev, P. ; Ivanov, S. N. ; Kasprzak, M. ; Kermaidic, Y. ; Kirch, K. ; Koch, H.-C. ; Komposch, S. ; Koss, P. A. ; Kozela, A. ; Krempel, J. ; Lauss, B. ; Lefort, T. ; Lemiere, Y. ; Leredde, A. ; Mohanmurthy, P. ; Pais, D. ; Piegsa, F. M. ; Pignol, G. ; Quéméner, G. ; Rawlik, M. ; Rebreyend, D. ; Ries, D. ; Roccia, S. ; Rozpedzik, D. ; Schmidt-Wellenburg, P. ; Schnabel, A. ; Severijns, N. ; Virot, R. ; Weis, Antoine ; Wursten, E. ; Wyszynski, G. ; Zejma, J. ; Zsigmond, G.

In: Physical Review A, 2019, vol. 99, no. 4, p. 042112

Magnetic-field uniformity is of the utmost importance in experiments to measure the electric dipole moment of the neutron. A general parametrization of the magnetic field in terms of harmonic polynomial modes is proposed, going beyond the linear- gradients approximation. We review the main undesirable effects of nonuniformities: depolarization of ultracold neutrons and Larmor frequency shifts...

Université de Fribourg

Characterization of the global network of optical magnetometers to search for exotic physics (GNOME)

Afach, S. ; Budker, D. ; Camp, G. De ; Dumont, V. ; Grujić, Zoran Dragan ; Guo, H. ; Jackson Kimball, D. F. ; Kornack, T. W. ; Lebedev, Victor ; Li, W. ; Masia-Roig, H. ; Nix, S. ; Padniuk, M. ; Palm, C. A. ; Pankow, C. ; Penaflor, A. ; Peng, X. ; Pustelny, Simon ; Scholtes, Theo ; Smiga, J. A. ; Stalnaker, J. E. ; Weis, Antoine ; Wickenbrock, A. ; Wurm, D.

In: Physics of the Dark Universe, 2018, vol. 22, p. 162–180

The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. The GNOME is sensitive to nuclear- and electron-spin couplings to exotic fields from astrophysical sources such as compact...

Université de Fribourg

Cesium alignment produced by pumping with unpolarized light

Shi, Yongqi ; Weis, Antoine

In: The European Physical Journal D, 2018, vol. 72, no. 4, p. 73

We demonstrate optical pumping on the four hyperfine components of the Cs D1 transition by unpolarized (UPL) resonant laser light. The evidence is based on the reduction of the absorption coefficients κ0 with increasing light power P in an uncoated Cs vapor cell with isotropic spin relaxation. For comparison we perform the same quantitative κ0(P) measurements with linearly-polarized light...

Université de Fribourg

Searching for axion stars and $Q$-balls with a terrestrial magnetometer network

Kimball, D. F. Jackson ; Budker, D. ; Eby, J. ; Pospelov, M. ; Pustelny, Szymon ; Scholtes, Theo ; Stadnik, Y. V. ; Weis, Antoine ; Wickenbrock, A.

In: Physical Review D, 2018, vol. 97, no. 4, p. 043002

Light (pseudo-)scalar fields are promising candidates to be the dark matter in the Universe. Under certain initial conditions in the early Universe and/or with certain types of self-interactions, they can form compact dark-matter objects such as axion stars or Q-balls. Direct encounters with such objects can be searched for by using a global network of atomic magnetometers. It is shown that...

Université de Fribourg

An arbitrary-function light power controller

Grujić, Zoran D. ; Piller, Jari ; Weis, Antoine

In: Review of Scientific Instruments, 2018, vol. 89, no. 2, p. 025114

We describe the design, applications, and performance of a simple light power controller. The device is built on a fiber-coupled electro-optic modulator with an active electronic feedback. It can be used to actively stabilize laser power or to impress an arbitrary waveform onto the power. The bandwidth of the device is ∼70 kHz.

Université de Fribourg

Quantitative study of optical pumping in the presence of spin-exchange relaxation

Shi, Yongqi ; Scholtes, Theo ; Grujić, Zoran D. ; Lebedev, Victor ; Dolgovskiy, Vladimir ; Weis, Antoine

In: Physical Review A, 2018, vol. 97, no. 1, p. 013419

We have performed quantitative measurements of the variation of the on-resonance absorption coefficients κ0 of the four hyperfine components of the Cs D1 transition as a function of laser power P, for pumping with linearly and with circularly polarized light. Sublevel populations derived from rate equations assuming isotropic population relaxation (at a rate γ1) yield algebraic κ0(P)...

Université de Fribourg

Study of ³He Rabi nutations by optically-pumped cesium magnetometers

Koch, Hans-Christian ; Bison, Georg ; Grujiæ, Zoran Dragan ; Heil, Werner ; Kasprzak, Malgorzata ; Knowles, Paul ; Kraft, Andreas ; Pazgalev, Anatoly ; Schnabel, Allard ; Voigt, Jens ; Weis, Antoine

In: The European Physical Journal D, 2017, vol. 71, no. 10, p. 262

We describe a method for recording the Rabi nutation of nuclear spin polarized ³He by optically pumped cesium magnetometers. The measurement is performed by detecting the time-dependent magnetic field produced by the 3He magnetization. The observed signals are compared to theoretical models and the results are used to precisely trace the evolution of the magnetization. This procedure...

Université de Fribourg

Search for axionlike dark matter through nuclear spin precession in electric and magnetic fields

Abel, C. ; Ayres, N.?J. ; Ban, G. ; Bison, G. ; Bodek, K. ; Bondar, V. ; Daum, M. ; Fairbairn, M. ; Flambaum, V.?V. ; Geltenbort, P. ; Green, K. ; Griffith, W.?C. ; Grinten, M. van der ; Grujiæ, Z.?D. ; Harris, P.?G. ; Hild, N. ; Iaydjiev, P. ; Ivanov, S.?N. ; Kasprzak, M. ; Kermaidic, Y. ; Kirch, K. ; Koch, H.-C. ; Komposch, S. ; Koss, P.?A. ; Kozela, A. ; Krempel, J. ; Lauss, B. ; Lefort, T. ; Lemi?re, Y. ; Marsh, D.?J.?E. ; Mohanmurthy, P. ; Mtchedlishvili, A. ; Musgrave, M. ; Piegsa, F.?M. ; Pignol, G. ; Rawlik, M. ; Rebreyend, D. ; Ries, D. ; Roccia, S. ; Rozpêdzik, D. ; Schmidt-Wellenburg, P. ; Severijns, N. ; Shiers, D. ; Stadnik, Y.?V. ; Weis, Antoine ; Wursten, E. ; Zejma, J. ; Zsigmond, G.

In: Physical Review X, 2017, vol. 7, no. 4, p. 041034

We report on a search for ultralow-mass axionlike dark matter by analyzing the ratio of the spin-precession frequencies of stored ultracold neutrons and 199Hg atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range 10−24≤ma≤10−17 eV. Our null result...

Université de Fribourg

Comment on: Magnetic field measurements in Rb vapor by splitting Hanle resonances under the presence of a perpendicular scanning magnetic field

Weis, Antoine ; Shi, Yongqi ; Grujić, Zoran D.

In: The European Physical Journal D, 2017, vol. 71, no. 4, p. 80

In a recent article in this journal Grewal and Pattabiraman reported on the splitting of ground state Hanle resonances (recorded with linearly polarized light) by a transverse field. They claimed a “linearly proportional” dependence on the transverse field strength and supported this observation with results from numerical simulations. In this comment we argue that the splitting occurs...