Entwicklung eines Mehrkammer-(Ko)Magnetometers mit 199Hg für eine neue Messung des Neutron EDM

• Applicant: Dr. Gerd Petzoldt
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2013 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 237445972

Precision magnetometry is a crucial part for a next-generation measurement of the neutron EDM with a sensitivity goal of 10-28 ecm. In this proposal, we describe a unique multi-chamber (co-)magnetometer setup which reads out the spin precession frequency of polarized 199Hg in a magnetic field optically. Its main features are a vertical stack of four large-volume magnetometer cells and a laser-based read-out and pumping scheme. The main goals of the project are to provide (i) online magnetic field measurements in-situ during nEDM measurement runs with the required sensitivity of < 10 fT for 250 s integration time per magnetometer cell and (ii) information about vertical gradients of the main magnetic field. It has been demonstrated in previous experiments that a sensitivity of 40 fT for one magnetometer cell is achievable using Hg discharge lamps. Using a laser as lightsource instead will provide significantly higher pumping power and stability, both of which will greatly increase the signal-to-noise ratio and allow us to extract the precession frequency of the Hg with higher precision. Since we have full control over all of the laser's properties, we also have unique possibilities to study systematic effects connected to the read-out light. The combination of data obtained from all four cells gives us access to not only the mean magnetic field but also to possible vertical gradients and distortions of the main magnetic field. Within this project we want to develop a system that meets both goals in three stages. Stage 1 is the optimization of laser performance and Hg cell properties using an existing test setup with one cell. Stage 2 consists of the installation of the magnetometer in a magnetically shielded environment and the expansion to multiple cells, as well as testing against other magnetometry systems and stage 3 is the implementation into the final experimental setup of the neutron EDM experiment and operation.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1491: Precision Experiments in Particle- and Astrophysics with Cold and Ultracold Neutrons
• Major Instrumentation: optical assembly components
• Instrumentation Group: 0160 Stromversorgungs- und Steuergeräte für Magnete: Zubehör