Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Performance of new silica aerogels in a threshold Cerenkov counter   New highly transparent, hydrophobic silica aerogels with refractive indices
of 1.01 to 1.07 have been produced by Aspen Aerogels, Inc., and select tiles
have been tested using an electron beam at the DESY, Hamburg facility. A
diffusively-reflective threshold Cerenkov counter was designed and constructed
for the purpose of evaluating the aerogels, and can accommodate aerogel tile
areas of up to 20 cm by 20 cm. Measurements of the performance of the counter
using the new aerogels as Cerenkov radiators are given in terms of
photoelectron yields and a figure of merit.

31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat