Abstract
We have developed a highly sensitive 3 He magnetometer for the accurate measurement of the magnetic field in an experiment searching for an electric dipole moment of the neutron. By measuring the Larmor frequency of nuclear spin polarized 3 He atoms a sensitivity on the femto-Tesla scale can be achieved. A 3 He/Cs-test facility was established at the Institute of Physics of the Johannes Gutenberg University in Mainz to investigate the readout of 3 He free induction decay with a lamp-pumped Cs magnetometer. For this we designed and built an ultra-compact and transportable polarizer unit which polarizes 3 He gas up to 55% by metastability exchange optical pumping. The polarized 3 He was successfully transfered from the polarizer into a glass cell mounted in a magnetic shield and the 3 He free induction decay was detected by a
Highlights
In 1950, Purcell and Ramsey [1] were the first to point out that the existence of an electric dipole moment (EDM) in an elementary particle with spin would violate the parity symmetry P
We describe the technical realization of a 3He magnetometer system that shall be implemented into the Paul Scherrer Institute (PSI) n2EDM experiment
A test facility for the recording of 3He free induction decay (FID) by a lamp-pumped CsOPM was installed at University of Mainz
Summary
In 1950, Purcell and Ramsey [1] were the first to point out that the existence of an electric dipole moment (EDM) in an elementary particle with spin would violate the parity symmetry P. The long coherence time of the 3He FID signal, which strongly depends on the absolute magnetic field gradients (∼ 20 pT/cm), the magnetometer cell material, the size of the magnetometer vessels as well as the 3He pressure (p ∼ mbar)[29], reaches the order of one hour under the typical operating conditions of the EDM apparatus. Assuming a typical Ramsey cycle time for the ultracold neutrons of ≈ 200 s, it is possible to run 2–3 Ramey cycles with a single 3He filling without significant decay of the 3He FID signal amplitude After these cycles the partly relaxed 3He will be pumped out, eventually recovered [30] and replaced by freshly polarized gas that has been prepared by the UCPU during the Ramsey cycles. A quasi-continuous operation of the 3He magnetometer will be possible
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