Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An Instrument for Investigating the Large Angular Scale Polarization of
  the Cosmic Microwave Background   We describe the design and performance of a microwave polarimeter used to
make precision measurements of polarized astrophysical radiation in three
microwave frequency bands spanning 26-36 GHz. The instrument uses cooled HEMT
amplifiers in a correlation polarimeter configuration to achieve high
sensitivity and long-term stability. The instrument demonstrates long term
stability and has produced the most restrictive upper limits to date on the
large angular scale polarization of the 2.7 K cosmic microwave background
radiation.

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The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th