Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Achievement of Ultra-High Quality Factor in Prototype Cryomodule for
  LCLS-II   Quality factor is a primary cost driver for high energy, continuous wave (CW)
SRF linacs like the LCLS-II X-ray free electron laser currently under
construction. Taking this into account, several innovations were introduced in
the LCLS-II cryomodule design to push substantially beyond the previous
state-of-the-art quality factor achieved in operation. This includes the first
ever implementation of the nitrogen doping cavity treatment, the capability to
provide high mass flow cooldown to improve expulsion of magnetic flux based on
recent R&D, high performance magnetic shielding, and other critical
subcomponents. To evaluate the implementation of these new cryomodule features,
two prototype cryomodules were produced. In this paper, we present results from
the prototype cryomodule assembled at Fermilab, which achieved unprecedented
cavity quality factors of 3.0e10 at a nominal cryomodule voltage. We overview
cavity performance, procedures to achieve ambient magnetic field < 5 mG at the
cavity wall, and the successful demonstration of high mass flow cooldown in a
cryomodule. The cavity performance under various cool down conditions are
presented as well to show the impact of flux expulsion on Q0.

34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga