Magnetic field uniformity in neutron electric dipole moment experiments

C. Abel , N. Ayres , T. Baker , G. Ban (1) , G. Bison , K. Bodek , V. Bondar , C. Crawford , P.-J. Chiu , E. Chanel , Z. Chowdhuri , M. Daum , B. Dechenaux (1) , S. Emmenegger , L. Ferraris-Bouchez (2) , P. Flaux (1) , P. Geltenbort (3) , K. Green , W.C. Griffith , M. van Der Grinten , P.G. Harris , R. Henneck , N. Hild , P. Iaydjiev , S.N. Ivanov , M. Kasprzak , Y. Kermaidic (2) , K. Kirch , H.-C. Koch , S. Komposch , P.A. Koss , A. Kozela , J. Krempel , B. Lauss , T. Lefort (1) , Y. Lemiere (1) , A. Leredde (2) , P. Mohanmurthy , D. Pais , F.M. Piegsa , G. Pignol (2) , G. Quéméner (1) , M. Rawlik , D. Rebreyend (2) , D. Ries , S. Roccia (4) , D. Rozpedzik , P. Schmidt-Wellenburg , A. Schnabel , N. Severijns , R. Virot (2) , A. Weis , E. Wursten , G. Wyszynski , J. Zejma , G. Zsigmond

1 LPCC - Laboratoire de physique corpusculaire de Caen
2 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
3 ILL - Institut Laue-Langevin
4 CSNSM - Centre de Sciences Nucléaires et de Sciences de la Matière

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 of neutrons and mercury atoms. The theoretical predictions for these effects were verified by dedicated measurements with the single-chamber neutron electric-dipole-moment apparatus installed at the Paul Scherrer Institute.

Mots clés: Fundamental concepts; n: electric moment; magnetic field: parametrization; mercury: atom; n: depolarization; mathematical methods; measurement methods

Domaines: Instrumentations et Détecteurs [physics.ins-det]; Physique des Hautes Energies - Expérience [hep-ex]

C. Abel, N. Ayres, T. Baker, G. Ban, G. Bison, et al.. Magnetic field uniformity in neutron electric dipole moment experiments. Phys.Rev.A, 2019, 99 (4), pp.042112. ⟨10.1103/PhysRevA.99.042112⟩. ⟨hal-01952936⟩