Speaker
Description
LCLS-II is an X-Ray Free Electron Laser (XFEL) com-
missioned in 2022, being the first Continuous Wave (CW)
hard XFEL in the world to come into operation. To accel-
erate the electron beam to an energy of 4 GeV, 280 TESLA
type superconducting RF (SRF) cavities are used. A Loaded
Q (𝑄𝐿 ) of 4×10^7 is used to drive the cavities at a power level
of a few kilowatts. For this 𝑄𝐿 , the RF cavity bandwidth is
32 Hz. Therefore, keeping the cavity resonance frequency
within such bandwidth is imperative to avoid a significant
increase in the required drive power. In superconducting
accelerators, resonance frequency variations are produced
by mechanical microphonic vibrations of the cavities. One
source of microphonics noise is rotary machinery such as
vacuum pumps or HVAC equipment. A possible method
to reject these disturbances is to use Narrowband Active
Noise Control (NANC) techniques. Such a technique was
already tested at DESY/CMTB and Cornell/CBETA.
This proceeding presents the implementation of a NANC
controller using the LCLS-II Low Level RF (LLRF) control
system. Tests on the rejection of LCLS-II microphonics
disturbances are also presented.
