  Multipacting (MP) is a phenomenon which can affect stability in particle
accelerators and limit performance in superconducting radio frequency cavities.
In the TESLA shaped, 1.3 GHz, 9-cell cavities used in the LCLS-II (L2) and
LCLS-II-HE (HE) projects, the MP-band (~17-24 MV/m) lies within the required
accelerating gradients. For HE, the operating gradient of 20.8 MV/m lies well
within the MP-band and cryomodule testing has confirmed that this is an issue.
As such, MP processing for the HE cryomodule test program will be discussed.
Early results on MP processing in cryomodules installed in the L2 linac will
also be presented, demonstrating that the methods used in cryomodule acceptance
testing are also successful at conditioning MP in the accelerator and that this
processing is preserved in the mid-term.
