Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Study on the multi-pass, multi-bunch beam breakup for 9-cell TESLA
  cavities in ERL   Generally, Energy Recovery Linac (ERL) needs special designed high current
superconducting RF cavities. In this paper, the threshold current of BBU for
compact ERL facilities with 9-cell Tesla type cavities are investigated. The
results show that it is feasible to adopt 9-cell Tesla cavity for compact ERL
test facilities with just a few cavities and beam current around tens mA.

15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga