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The 2nd video conference meeting for the SPL cavity working groups took place on February 8th 2010.
Participants:
CERN: E. Chiaveri, O. Capatina, M. Schuh, R. Calaga, T. Renaglia, S. Calatroni, V. Parma, W. Weingarten (from home)
TRIUMF: R. Laxdal
CEA Saclay: G. Devanz; S. Chel
CNRS Orsay: F. Bouly, H. M. Gassot, G. Orly<o:p></o:p>
TU Darmstadt: W. Mueller (audio only)
Royal Holloway London: Steve Molloy (audio only)
The proposed agenda was:<o:p></o:p>
. Approval of minutes/agenda<o:p></o:p>
. beta = 0.65 SPL cavity design features<o:p></o:p>
.. Final RF design, Frederic Bouly (IPN, Orsay (France))<o:p></o:p>
.. Mechanical calculations, Hui Min Gassot (IPN, Orsay (France))<o:p></o:p>
.. Cavity + Helium vessel technical drawings, Guillaume Olry (IPN, Orsay (France)) <o:p></o:p>
. Fabrication of Nb and Cu SPL cavities and required tools (resumed from 1st meeting), Ofelia Capatina (CERN) <o:p></o:p>
. Mechanical layout and RF/cryogenic/vacuum interfaces of SPL cavities inside cryomodule, Ofelia Capatina (CERN),<o:p></o:p>
. First estimations of external Q-values for specific HOM damping schemes (2nd part), Rama Calaga (Brookhaven National Lab (USA))<o:p></o:p>
. AOB<o:p></o:p>
. Date of next meeting and agenda topics<o:p></o:p>
<o:p></o:p>
Detailed discussions:<o:p></o:p>
. Approval of agenda => the agenda was approved<o:p></o:p>
. beta = 0.65 SPL cavity design features<o:p></o:p>
.. Final RF design (Frederic Bouly). Design specifications / input parameters are listed in slide #2. Simulations have been carried with 2D and 3D codes, and results correspond (field flatness 2.55% vs. 6.3 %) within the inherent uncertainties of the codes. Calculation have been performed with 1 mm antenna penetration into beam pipe.<o:p></o:p>
.. Mechanical calculations (Hui Min Gassot). Calculation of deformations have been made by 3D mechanical code using the above results as input for the EM forces. The position of the stiffening rings and the thickness of the Nb sheet has been optimized to minimize frequency shift. It results a niobium sheet thickness of 4 mm, and 5 mm for the outer half cells, no ribs on end cells.<o:p></o:p>
.. Cavity + Helium vessel technical drawings (Guillaume Orly). Several evolutions of the design have been illustrated. The main coupler port is not integrated in the He vessel, and has been shifted away 15 mm. New calculations of the Qext as a function of penetration have been carried out (16mm for 1E6). S. Calatroni suggests to evaluate the heat dissipation for the coupler region. R. Calaga suggests considering a smaller diameter for the coupler.<o:p></o:p>
. Fabrication of Nb and Cu SPL cavities and required tools (Ofelia Capatina). The present status of the design, specifications of materials and tooling required for fabrication of beta=1 cavity was shown. Final minimum thickness must be 3 mm (=> starting Nb sheet is 3.5 mm thick). 8 cavities have to be fabricated, proposal is to make 2 inside CERN including tooling and 6 by industry. There are still some discrepancies between CERN and CEA designs that have to be finalized. Copper cavities will also fabricated for HOM testing purposes, with similar procedure as for Nb. S. Chel comments that CEA forecast is to subcontract all fabrication of their cavities (including tooling fabrication) to an external contractor. E. Chiaveri comments on the choice for a vertical coupler at the bottom, contrary to LEP studies and assembly experience. S. Calatroni indicates the need for electropolishing prior to welding if the Cu cavities have to be used for coating purposes. He remarks also that Nb purchase has to be done asap given the long delivery times.<o:p></o:p>
. Mechanical layout and RF/cryogenic/vacuum interfaces of SPL cavities inside cryomodule (Ofelia Capatina). A first integration design has been shown. <o:p></o:p>
. First estimations of external Q-values for specific HOM damping schemes (Rama Calaga). Postponed to next meeting due to lack of time.<o:p></o:p>
. AOB => Steve Molloy comments that they have 1 student and 1 postdoc working on SPL related issues. They are interested in the field flatness studies and are working with a UK company to obtain a grant for a Cu cavity<o:p></o:p>
. Next meeting will take place on Monday March 8th 2010.<o:p></o:p>