Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The optical module of the Baikal deep underwater neutrino telescope   A deep underwater Cherenkov telescope has been operating since 1993 in stages
of growing size at 1.1 km depth in Lake Baikal. The key component of the
telescope is the Optical Module (OM) which houses the highly sensitive
phototube QUASAR-370. We describe design and parameters of the QUASAR-370, the
layout of the optical module, the front-end electronics and the calibration
procedures, and present selected results from the five-year operation
underwater. Also, future developments with respect to a telescope consisting
from several thousand OMs are discussed.

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The categories of this paper are: math
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The categories of this paper are: cs
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
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The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys