Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Integrated optically pumped magnetometer for measurements within Earth's
  magnetic field   We present a portable optically pumped magnetometer instrument for
ultra-sensitive measurements within the Earth's magnetic field. The central
part of the system is a sensor head operating a MEMS-based Cs vapor cell in the
light-shift dispersed Mz mode. It is connected to a compact, battery-driven
electronics module by a flexible cable. We briefly review the working
principles of the device and detail on the realization of both, sensor head and
electronics. We show shielded and unshielded measurements within a static
magnetic field amplitude of 50 uT demonstrating a noise level of the sensor
system down to 140 fT/\sqrt{Hz} and a sensor bandwidth of several 100 Hz. In a
detailed analysis of sensor noise we reveal the system to be limited by
technical sources with straightforward strategies for further improvement
towards its fundamental noise limit of 12 fT/\sqrt{Hz}. We assess the
parameters defining the sensor bandwidth by theoretical modeling based on the
Bloch equations. Finally, we compare our sensors' performance to a commercial
SQUID system in a measurement environment typical for geomagnetic observatory
practice and geomagnetic prospection.

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The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys