arXiv subjects

S. Groeger

Publications and source records attributed to S. Groeger.

3 recordsLinked to original sources

arXiv2005

A sound card based multi-channel frequency measurement system

For physical processes which express themselves as a frequency, for example magnetic field measurements using optically-pumped alkali-vapor magnetometers, the precise extraction of the frequency from the noisy signal is a classical problem. We describe herein a frequency measurement system based on an inexpensive commercially available computer sound card coupled with a software single-tone estimator which reaches Cramér--Rao limited performance, a feature which commercial frequency counters often lack. Characterization of the system and examples of its successful application to magnetometry are presented.

physics.ins-det↗

arXiv2004

Comparison of discharge lamp and laser pumped cesium magnetometers

We have performed a comparison of laser (LsOPM) and lamp (LpOPM) pumped cesium vapor magnetometers. Although the LsOPM operated 50% above its shot-noise limit we found an intrinsic sensitivity of 15 fT/\sqrt{Hz} and 25 fT/\sqrt{Hz} for the LsOPM and LpOPM respectively. Two modes of operation, viz.,the phase-stabilized and the self-oscillating mode were investigated and found to yield a similar performance. We have compared the performance of the LsOPM and the LpOPM directly by simultaneous measurements of field fluctuations of a 2 microtesla magnetic field inside a multilayer magnetic shield and have used one of the magnetometers for an active field stabilization. In the stabilized mode we found a gradient instability of 25 fT within an integration time of 100 s, which represents an upper limit of the long-term stability of the magnetometers.

physics.atom-ph↗

arXiv2004

A high-sensitivity laser-pumped $M_x$-magnetometer

We discuss the design and performance of a laser-pumped cesium vapor magnetometer in the $M_x$-configuration. The device will be implemented for the control and stabilization of fluctuating magnetic fields and gradients in a new experiment searching for a permanent electric dipole moment of the neutron. We have determined the intrinsic sensitivity of the device to be 21 fT with a 1 s integration time, limited by low frequency noise of the laser power. In the shot noise limit the magnetometer can reach a sensitivity of 7 fT with a 1 s integration time. We have used the device to study the magnetic field fluctuations in a three layer mu-metal shield for integration times in the range of 2-100 seconds. The lowest values of the fluctuations are traced back to the stability of the power supply used to generate the field.

physics.atom-ph↗