||A cryomodule housing two strongly
HOM-damped 352 MHz superconducting (SC) Nb/Cu single-cell-cavities has
been developed within the framework of the SOLEIL project design phase.
In 2002, the prototype was installed in the ESRF storage ring and
tested with beam in the accelerating regime, the cavities being cooled
down to 4.5 K by means of liquid helium from Dewars. Four series of
tests have been carried out at the end of scheduled shutdowns. In order
not to disturb the ESRF machine performance during the user mode of
operation, the cavities were maintained detuned at room temperature.
In this passive regime, they remained transparent to the beam
with less than 100 W of deposited power, evacuated by a warm helium gas
flow. Up to 170 mA of beam could be accelerated with a peak RF
voltage of 3 MV and a power of 360 kW from the SC module. This
corresponds to the performance required for the first SOLEIL operation
phase. The concept of effective HOM damping was validated up to the
maximum ESRF intensity of 200 mA. A few week points already identified
at previous CERN tests were confirmed: high static cryogenic losses,
poor cooling of one HOM coupler and too high fundamental power through
the dipolar HOM couplers.