Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Compact, directional neutron detectors capable of high-resolution
  nuclear recoil imaging   We report on the design, production, and performance of compact 40-cm$^3$
Time Projection Chambers (TPCs) that detect fast neutrons by measuring the
three-dimensional (3D) ionization distribution of nuclear recoils in
$^4$He:CO$_2$ gas at atmospheric pressure. We use these detectors to
characterize the fast-neutron flux inside the Belle II detector at the
SuperKEKB electron-positron collider in Tsukuba, Japan, where the primary
design constraint is a small form factor. We find that the TPCs meet or exceed
all design specifications, and are capable of measuring the 3D surface shape
and charge density profile of ionization clouds from nuclear recoils and
charged tracks in exquisite detail. Scaled-up detectors based on the detection
principle demonstrated here may be suitable for directional dark matter
searches, measurements of coherent neutrino-nucleus scattering, and other
experiments requiring precise detection of neutrons or nuclear recoils.

35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
6
The categories of this paper are: astro-ph