Project

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Highly accurate vector gradiometers for a next-generation neutron EDM experiment

Applicant Bison Georg
Number 172626
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Particle Physics
Start/End 01.08.2017 - 31.07.2021
Approved amount 283'050.00
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All Disciplines (2)

Discipline
Particle Physics
Other disciplines of Physics

Keywords (3)

magnetic field homogenization; vector magnetometry; neutron electric dipole moment

Lay Summary (German)

Lead
In diesem Projekt werden spezielle Magnetfeldsensoren entwickelt die für ein Experiment zur Messung des elektrischen Dipolmoments des Neutrons am Paul Scherrer Institut benötigt werden. Die neuen Sensoren sollen 100-mal kleinere absolute Messunsicherheiten haben um das Magnetfeld im inneren des Experiments hochgenau zu überwachen. Nur so kann ein neues Experiment realisiert werden das empfindlicher als je zuvor nach dem Dipolmoment des Neutrons suchen wird. Die beteiligten Forscher hoffen diese Eigenschaft des Neutrons erstmals nachzuweisen die als Wegweiser gilt um die Entstehung der Materie kurz nach dem Urknall zu verstehen.
Lay summary

Das Paul Scherrer Institut plant ein neues Experiment um das elektrische Dipolmoment des Neutrons (nEDM) zu entdecken. Diese Teilcheneigenschaft, nach der seit über 60 Jahren gesucht wird, konnte bis jetzt nicht nachgewiesen werden gilt aber als einer der wichtigsten Wegweiser zum Verständnis der Materieentstehung kurz nach dem Urknall.Es ist seit langem bekannt das sich Neutronen in einem Magnetfeld ähnlich wie ein Kreisel mit einer charakteristischen Frequenz, der Larmorfrequenz, drehen (Präzession). Falls das nEDM existiert dann muss sich die Larmorfrequenz um einen winzigen Betrag ändern wenn ein elektrisches Feld angelegt wird. Das neue Experiment soll wesentlich grösser und empfindlicher werden als jemals zuvor um diese winzige Änderung der Larmorfrequenz zu messen. Eine wichtige Voraussetzung für das neue Experiment ist es ein sehr stabiles Magnetfeld. Magnetfelder die fluktuieren oder nicht ganz gleichförmig sind stören die Messung. Diese Störung kann kompensiert werden wenn das Magnetfeld an vielen Punkten im Experiment gemessen werden kann. Nur so ist es möglich die angestrebte Messgenauigkeit zu erreichen. In diesem Projekt werden spezielle Magnetfeldsensoren entwickelt mit denen die volle Empfindlichkeit des nEDM Experiments sichergestellt werden kann. Die Sensoren benutzen Atome die sich auch im Magnetfeld mit einer charakteristischen Larmorfrequenz drehen. Im Gegensatz zu den Neutronen kann die Drehung der Atome mit Laserlicht gemessen werden. So ist es möglich schon während dem Ablauf des Experiments Informationen über das Magnetfeld zu sammeln. Um die volle Messgenauigkeit des nEDM Experiments zu realisieren müssen die Magnetfeldsensoren etwa 100-mal kleinere absolute Messfehler haben als bevor. Die Realisierung dieses ehrgeizigen Ziels wird die zentrale Aufgabe dieses Projekts sein. Zusammen mit Partnern aus 12 Instituten tragen die am diesem Projekt beteiligten Wissenschaftler so dazu bei dass das EDM des Neutrons hoffentlich bald entdeckt wird.

Direct link to Lay Summary Last update: 12.07.2017

Responsible applicant and co-applicants

Employees

Publications

Publication
Optically pumped Cs magnetometers enabling a high-sensitivity search for the neutron electric dipole moment
Abel C., Afach S., Ayres N. J., Ban G., Bison G., Bodek K., Bondar V., Chanel E., Chiu P.-J., Crawford C. B., Chowdhuri Z., Daum M., Emmenegger S., Ferraris-Bouchez L., Fertl M., Franke B., Griffith W. C., Grujić Z. D., Hayen L., Hélaine V., Hild N., Kasprzak M., Kermaidic Y., Kirch K., et al. (2020), Optically pumped Cs magnetometers enabling a high-sensitivity search for the neutron electric dipole moment, in Physical Review A, 101(5), 053419-053419.
Measurement of the Permanent Electric Dipole Moment of the Neutron
Abel C., Afach S., Ayres N. J., Baker C. A., Ban G., Bison G., Bodek K., Bondar V., Burghoff M., Chanel E., Chowdhuri Z., Chiu P.-J., Clement B., Crawford C. B., Daum M., Emmenegger S., Ferraris-Bouchez L., Fertl M., Flaux P., Franke B., Fratangelo A., Geltenbort P., Green K., Griffith W. C., et al. (2020), Measurement of the Permanent Electric Dipole Moment of the Neutron, in Physical Review Letters, 124(8), 081803-081803.
PicoTesla absolute field readings with a hybrid 3He/87Rb magnetometer
Abel Christopher, Bison Georg, Griffith W. Clark, Heil Werner, Kirch Klaus, Koch Hans-Christian, Lauss Bernhard, Mtchedlishvili Alexander, Pototschnig Martin, Schmidt-Wellenburg Philipp, Schnabel Allard, Pais Duarte, Voigt Jens (2019), PicoTesla absolute field readings with a hybrid 3He/87Rb magnetometer, in The European Physical Journal D, 73(7), 150-150.
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., van der Grinten M., Harris P. G., Henneck R., Hild N., Iaydjiev P., et al. (2019), Magnetic-field uniformity in neutron electric-dipole-moment experiments, in Physical Review A, 99(4), 042112-042112.
Demonstration of sensitivity increase in mercury free-spin-precession magnetometers due to laser-based readout for neutron electric dipole moment searches
Ban G., Bison G., Bodek K., Daum M., Fertl M., Franke B., Grujić Z.D., Heil W., Horras M., Kasprzak M., Kermaidic Y., Kirch K., Koch H.-C., Komposch S., Kozela A., Krempel J., Lauss B., Lefort T., Mtchedlishvili A., Pignol G., Piegsa F.M., Prashanth P., Quéméner G., Rawlik M., et al. (2018), Demonstration of sensitivity increase in mercury free-spin-precession magnetometers due to laser-based readout for neutron electric dipole moment searches, in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detector, 896, 129-138.
Sensitive and stable vector magnetometer for operation in zero and finite fields
Bison G., Bondar V., Schmidt-Wellenburg P., Schnabel A., Voigt J. (2018), Sensitive and stable vector magnetometer for operation in zero and finite fields, in Optics Express, 26(13), 17350-17350.

Collaboration

Group / person Country
Types of collaboration
Niels Bohr Institut Kopenhagen Denmark (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
Physikalisch Technische Bundesanstalt Berlin Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
144257 Spatially resolved magneto-relaxation of in-vitro magnetic nanoparticles using atomic magnetometry 01.09.2012 Sinergia
149211 Measurement of the neutron electric dipole moment 01.11.2013 Project funding (Div. I-III)
139140 Passive magnetic shield for the new neutron electric dipole moment experiment n2EDM 01.01.2013 R'EQUIP
163988 New magnetometer array for the n2EDM project 01.07.2015 International short research visits
140421 Optical magnetometry for a new neutron EDM experiment 01.04.2012 Project funding (Div. I-III)
149813 Pushing the high intensity frontier with ultracold neutrons 01.11.2013 Project funding (Div. I-III)
186179 n2EDM: The next measurement of the neutron electric dipole moment 01.04.2019 FLARE
144473 Search for the neutron EDM at the high intensity ultracold neutron source at PSI with an upgraded high sensitivity spectrometer - Follow-up application 01.10.2012 Project funding (Div. I-III)
188700 A new search for an electric dipole moment of the neutron with increased sensitivity and an improved UCN source. 01.09.2020 Project funding (Div. I-III)

Abstract

Our collaboration, which consists of 15 institutions, uses a magnetic resonance experiment at PSI to search for the electric dipole moment of the neutron (nEDM). The existence of a finite neutron EDM dn, which is predicted by many theories beyond the standard model of particle physics (TBSM), has not yet been confirmed. The current best upper limit of dn < 3E-26 e·cm significantly restricts the parameter space of many TBSM. Since improved limits on dn or a discovery of a finite value would be a powerful guide in the development of a TBSM, the neutron EDM is deemed one of the most sensitive tests of physics beyond the standard model. As a consequence, several collaborations around the world currently compete to realize a next-generation nEDM experiment with planned sensitivities in the E-27 e·cm to E-28 e·cm range.One of the most important design criteria for an improved nEDM experiment is the realization of a stable and homogeneous main magnetic field B0. The level at which B0 can be controlled or measured is directly linked to the achievable nEDM sensitivity since uncompensated B0 fluctuations add noise to the extracted nEDM value and field inhomogeneities give rise to several systematic effects. The primary goal of this project is to realize a magnetic environment which is stable and homogeneous enough to reach the dn < E-27 e·cm level. Neutron EDM experiments must use a wide range of techniques to meet those increasing demands on B0 control. The work proposed here focusses on Cs magnetometers that are developed at PSI and in the nEDM collaboration since several years.Assuming typical experimental conditions, the uncompensated magnetic field fluctuations in each experimental cycle must be smaller than 10 fT in order to achieve a limit of dn < E-27 e·cm after two years of data taking. We propose to develop an nEDM analysis method that uses Cs magnetometers to measure the field fluctuations, which requires a corresponding stability of the sensors.In 2016 we confirmed a systematic error in nEDM measurements with a Hg co-magnetometer caused by cubic gradients. Due to the symmetry of the gradient field it cannot be detected with large-volume magnetometers. A spatially resolved mapping of the field with many accurate sensors is necessary to suppress the effect. The estimated requirements for sensor accuracy of 0.5 pT are significantly higher than previously assumed. For that reason we propose to investigate magnetometers based on atomic alignment and linearly polarized light, which suppress many systematic magnetometer errors. Our previous methods on vector magnetometry and free spin precession will be transferred to spin alignment.We demonstrated that a field homogenization based on Cs magnetometer readings significantly in- creases the sensitivity of our current nEDM experiment. The proposed work will enable field homogenization with an array of Cs vector magnetometers that can measure and compensate magnetic field gradients. We expect to achieve a level of performance that will permit a search for a nEDM with a sensitivity much better than E-27 e·cm. The project will have a significant impact on the sensitivity and the control of systematic errors of our next-generation neutron EDM experiment. It is a key ingredient in that experiment which could lead to the first discovery of an EDM in a non-degenerate system.
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