Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Generation and measurement of sub-picosecond electron bunch in
  photocathode rf gun   We consider a scheme to generate sub-picosecond electron bunch in the
photocathode rf gun by improving the acceleration gradient in the gun, suitably
tuning the bunch charge, the laser spot size and the acceleration phase, and
reducing the growth of transverse emittance by laser shaping. A nondestructive
technique is also reported to measure the electron bunch length, by measuring
the high-frequency spectrum of wakefield radiation which is caused by the
passage of a relativistic electron bunch through a channel surrounded by a
dielectric.

1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin