3.9 GHz 3rd Harmonic Cavities

1. 3.9 GHz 3rd Harmonic Cavities • HOM coupler status -- FE analysis by Salman Tariq indicates Formteil leg fractures most likely due to high thermal stresses induced by overheating of the Formteil when RF power was applied -- thermal stresses were highest at the same location where the fractures occurred -- multipacting between Formteil and HOM housing possible cause of overheating. • Second FEA model under development (Sergi Segreto, Salman Tariq and Tom Peterson) will evaluate residual stresses arising during cooldown directly following welding of Formteil to HOM housing.

2. 3.9 GHz 3rd Harmonic Cavities • New HOM designs with modified Formteil geometry to alleviate multipacting and larger diameter legs to provide better heat sinking are under investigation. • These design variations will be evaluated for RF characteristics using a copper model with removable HOMs. • Cavity No. 3 (Jlab) is in preparation for testing -- RF power will be controlled to avoid excessive heating of Formteil.

3. 3.9 GHz 3rd Harmonic Cavities • Work on center sections of cavities No. 7 and No. 8 will continue at Sciaky -- these two cavities will not be completed until a new HOM design is approved. • Work on cavities No. 4-6 at Jlab is on hold until a new HOM design is approved. • Cavities No. 1 and No. 2 will be repaired. • SCHEDULE Completion dates for cavities No. 4-8 and repair of cavities No. 1 & 2 is unknown at this time -- a new HOM design will entail rebuilding all of the end tubes.

4. 1.3 GHz Cavity Fabrication: FY06 • OBJECTIVES Jlab is fabricating two Tesla cavities (asymmetric end tubes) from fine grain niobium and two ILC cavities (symmetric end tubes) from large grain niobium. AES is fabricating four Tesla cavities from fine grain niobium. • STATUS Jlab -- work is progressing on the two ILC cavities -- estimated completion date is late November or December 2006 -- material for two Tesla cavities has been shipped to Jlab -- estimated completion date for the two Tesla cavities is unknown at this time.

5. 1.3 GHz Cavity Fabrication: FY06 • STATUS AES -- end groups complete -- hydroforming of all half cells is complete -- iris and equator weld parameters have been developed -- welding of dumbbells is in progress this week -- estimated delivery date for the four cavities is January 2007. • ADDITIONAL CAVITY ORDERS PO to be issued for four ILC cavities will be sole sourced to AES. Bids solicited for fabrication of eight ILC cavities -- five positive responses were received and evaluated.