Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Impedance modelling and collective effects in the Future Circular
  e$^+$e$^-$ Collider with 4 IPs   The FCC-ee impedance model is being constantly updated closely following the
vacuum chamber design and parameters evolution. In particular, at present, a
thicker NEG coating of 150 nm (instead of previous 100 nm) has been suggested
by the vacuum experts, and a more realistic impedance model of the bellows has
been investigated. Moreover, also the transverse impedance has been updated by
considering the same sources as for the longitudinal case. Therefore, the
FCC-ee impedance database is getting more complete and the impedance model is
being refined. In this paper we describe the presently available machine
coupling impedance in both longitudinal and transverse planes, and study the
impedance-driven single bunch instabilities (with and without beam-beam
interaction) for the new FCC-ee parameter set with 4 interaction points (IPs).
The results are compared with the previously obtained ones and a further
possible mitigation of the beam-beam head-tail instability (X-Z instability) is
proposed.

8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn