| Paper | Title | Page |
|---|
| TUP47 | Diagnostic Instrumentation for the Fermilab Vertical Cavity Test Facility | 235 |
| | - C. M. Ginsburg, R. Carcagno, M. Champion, N. Dhanaraj, A. Lunin, A. Mukherjee, R. Nehring, D. Orris, J. P. Ozelis, V. Poloubotko, D. A. Sergatskov
Fermilab - W. -D. Moeller
DESY
| |
| | We describe the design and initial test results of the
Fermilab vertical cavity test facility (VCTF) diagnostic
instrumentation which is used to understand cavity
performance, including thermometry to detect hot spots
caused by quenches or field emission, and a variable RF
input coupler to facilitate the TM010 passband mode
measurements used to isolate poorly performing cells. | |
| TUP57 | First Fermilab Results of SRF Cavity Lorentz Force Detuning Compensation Using a Piezo Tuner | 259 |
| | - R. Carcagno, J. Branlard, B. Chase, H. Edwards, D. Orris, Y. Pischalnikov, A. Makulski, J. Reid, W. Schappert
Fermilab
| |
| | Lorentz force detuning compensation of TESLA type
cavities using commercially available piezo electric
actuators was first demonstrated at DESY [1].
Compensating for Lorentz force detuning to avoid
excessive RF power requirements is critical for high
gradient cavities such as the ones proposed for the ILC.
For this reason, Fermilab is working on issues related to
range, reliability, and automation of SRF cavity fast
tuners. A mechanical resonance excitation method is used
to increase the piezo tuner range. In order to study the
long-term reliability of the design a strain-gauge based
sensor was developed, which monitors the piezo tuner
preload continuously. A feed forward Lorentz force
detuning compensation algorithm using the forward
power signal, the field probe signal, and the phase
difference between them has been developed. This
algorithm is being implemented in a hybrid PC/FPGA
based control system providing automated signal
acquisition, system identification, and waveform
playback. In parallel, an FPGA based real-time cavity
simulator has been developed to validate the performance
of the system prior to its deployment and to provide a testbed
for further detuning and microphonics algorithm
development. The control system will be used to
compensate for cavity detuning in the first cryomodule
installed in the ILC Test Area at Fermilab. In tests of the
algorithm using CCII at a gradient of 26 MV/m,
compensation with a fast piezo tuner reduced the Lorentz
Force detuning from 275 Hz to 20 Hz. This compensation
resulted in a corresponding decrease of the peak klystron
power requirement from 120% to 105% of the nominal
power on resonance. | |