Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Why carbon dioxide makes stellarators so important   The increasing level of atmospheric carbon dioxide has driven public
discourse throughout the world. An immediate implementation of carbon-free
energy sources is demanded with little discussion of costs, technical
constraints on the sources, or implications of high residual levels of carbon
dioxide. Residual carbon-dioxide can be removed from the air, but the cost to
remove the carbon-dioxide produced by human activity during a year is thought
to be trillions of dollars---otherwise it remains in the atmosphere for
centuries. Economic considerations may limit wind and solar sources to less
than 40\% of the electricity production. Fission or fusion may be the only
choice for most of the rest. Development costs are orders of magnitude smaller
than implementation costs, which are tens of trillions of dollars for fission.
A needless delay in the development of fusion has enormous financial
implications. As will be shown stellarators are better positioned than any
other concept for a fast path to fusion. A computationally derived conceptual
design for a stellarator reactor may allow final design and construction to be
initiated without the delay of intermediate generations of experiments. The
most urgent issue is the development of conceptual designs.

17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio