Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Status of the RFD Linac Structure Developement   The Proof-of-Principle (POP) prototype of the Rf-Focused Drift tube (RFD)
linac structure is currently under test at Linac Systems, after years of delay
due to a variety of technical problems. A discussion of these technical
problems and their solutions will be presented. The status of these tests will
be reported. Plans for future development of this linac structure will be
revealed. Potential uses of this linac structure for a variety of scientific,
medical, and industrial applications will be described, including: proton linac
injectors for proton synchrotrons, compact proton linacs for PET isotope
production, epithermal neutron sources for the BNCT application, energy
boosters for proton therapy, compact portable neutron sources for thermal
neutron radiography, and pulsed cold neutron sources for cold neutron physics
and related applications.

32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph