| Paper | Title | Page |
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| WEPMN094 | Experience with Capture Cavity II | 2251 |
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Funding: This work supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U. S. DOE. Valuable experience in operating and maintaining superconducting RF cavities in a horizontal test module has been gained with Capture Cavity II. We report on all facets of our experience to date. |
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| WEPMN103 | Mechanical Stability Study of Capture Cavity II at Fermilab | 2274 |
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Problematic resonant conditions at both 18 Hz and 180 Hz were encountered and identified early during the commissioning of Capture Cavity II (CC2) at Fermilab. CC2 consists of an external vacuum vessel and a superconducting high gradient (close to 25 MV/m) 9-cell 1.3 GHz niobium cavity, transported from DESY for use in the A0 Photoinjector at Fermilab. An ANSYS modal finite element analysis (FEA) was performed in order to isolate the source of the resonance and directed the effort towards stabilization. A novel idea was implemented, by using a fast piezoelectric tuner to excite (or shake) the cavity at different frequencies (from 10 Hz to 200 Hz) as a low-range sweep for analysis purposes. Both warm (300 K) and cold (1.8 K) accelerometer measurements at the cavity were taken as the resonant 'fix' was applied. FEA results, cultural and technical noise investigation, and stabilization techniques are discussed.
Operated by Universities Research Association, Inc., under Contract No. DE-AC02-76CH03000 with the U. S. Department of Energy#mcgee@fnal.gov |
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| WEPMN104 | Mechanical Stability Study of Type IV Cryomodule (ILC Prototype) | 2277 |
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An ANSYS modal and harmonic finite element analysis (FEA) was performed in order to investigate cryomodule design mechanical stability for the proposed International Linear Collider (ILC). The current cryomodule, designated Type IV or T4CM, closely follows the Type III TESLA Test Facility (TTF) version used at DESY, with the exception of a proposed location of the superconducting (SC) quadrupole at the center. This analysis considered the stringent stability criteria established for the ILC, where vertical motion for the SC quad is limited to the micron range, at a few Hz. Model validation was achieved through Type II cryomodule vibration measurement studies performed at DESY. The effect of support location, support stiffness and other important parameters were considered in a parametric sensitivity study. FEA results, fast motion investigations and stabilization techniques are discussed.
Operated by Universities Research Association, Inc., under Contract No. DE-AC02-76CH03000 with the U. S. Department of Energy#mcgee@fnal.gov |
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| WEPMN108 | A Technique for Monitoring Fast Tuner Piezoactuator Preload Forces for Superconducting RF Cavities | 2289 |
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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 |
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| WEPMN092 | Capture Cavity II Results at FNAL | 2245 |
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Funding: FRA As part of the research and development towards the International Linear Collider (ILC), several test facilities have been developed at Fermilab. This paper presents the latest LLRF results obtained with Capture Cavity II at these test facilities. The main focus will be on controls and RF operations using the SIMCON based LLRF system. Details about hardware upgrades and overall system performance will be also explained. Finally, design considerations and objectives for the future test facility at the New Muon Laboratory (NML) will be presented. |