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Poloubotko, V.

Paper Title Page
WEPMN106 Design and Commissioning of Fermilab's Vertical Test Stand for ILC SRF Cavities 2283
  • J. P. Ozelis, R. H. Carcagno, C. M. Ginsburg, Y. Huang, B. Norris, T. Peterson, V. Poloubotko, R. Rabehl, I. Rakhno, C. Reid, D. A. Sergatskov, C. Sylvester, M. Wong, C. Worel
    Fermilab, Batavia, Illinois
  Funding: Operated by Universities Research Association, Inc. for the U. S. Department of Energy under contract DE-AC02-76CH03000

As part of a program to improve cavity performance reproducibility for the ILC, Fermilab is developing a facility for vertical testing of SRF cavities. It operates at a nominal temperature of 2K, using an existing cryoplant that can supply LHe in excess of 20g/sec and provides steady-state bath pumping capacity of 125W at 2K. The below-grade cryostat consists of a 4.9m long vacuum vessel and 4.5m long LHe vessel. The cryostat is equipped with external and internal magnetic shielding to reduce the ambient magnetic field to <10mG. Internal fixed and external movable radiation shielding ensures that radiation levels from heavily field-emitting cavities remain low. In the event that radiation levels exceed allowable limits, an integrated personnel safety system consisting of RF switches, interlocks, and area radiation monitors disables RF power to the cavity. In anticipation of increased throughput requirements that may be met with additional test stand installations, sub-systems have been designed to be easily upgradeable or to already meet these anticipated needs. Detailed facility designs, performance during system commissioning, and results from initial cavity tests are presented.

WEPMN108 A Technique for Monitoring Fast Tuner Piezoactuator Preload Forces for Superconducting RF Cavities 2289
  • Y. M. Pischalnikov, J. Branlard, R. H. Carcagno, B. Chase, H. Edwards, A. Makulski, M. McGee, R. Nehring, D. F. Orris, V. Poloubotko, C. Sylvester, S. Tariq
    Fermilab, Batavia, Illinois
  Funding: Work supported by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy.

The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities*. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant preload force on the piezo stack in the range of 10 to 50% of its specified blocking force. Determining the preload force during cooldown, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. This paper will address the design and testing of piezo actuator preload sensor technology. Results from measurements of preload sensors installed on the tuner of the DESY Capture Cavity II tested at Fermilab will be presented. These results include measurements during cooldown, warm-up, and cavity tuning along with dynamic Lorentz force compensation.

* M. Liepe et al," Dynamic Lorentz Force Compensation with a Fast Piezoelectric Tuner" PAC2001