Tests on production cryomodules Bob Kephart Sept 30, 2006

R. Kephart LCFOA Oct 06 2 Introduction The ILC cryomodule will evolve through several versions between now and the series production used to construct the machine The homework was: –investigate what tests are needed on the final production of industrial cryomodules –and what special tests are needed when the cryomodule design gets modified to make it cheaper to manufacture. –These tests may or may not be system tests our task force is responsible for planning.

R. Kephart LCFOA Oct 06 3 Types of changes Assuming we are starting with “working” prototype one can consider the types of changes that might occur Types of changes –Changes aimed at performance improvement –Changes driven by cost reduction Reduce labor Reduce M&S costs –Changes due to region of manufacture Availability of materials ( e.g. manufacturing standards) Regional vendors ( e.g. ceramic feed throughs)

R. Kephart LCFOA Oct 06 4 Performance Improvement Changes aimed at performance improvement –Typically these occur until the project management of an “approved” project “freezes” the specification –The number of objects tested is small –The tests are extensive but focused on performance validation –Performance validation leads then to industrial production and cost reduction This is ~ where XFEL is now –TTF is the test bed ILC is not yet to this point…

R. Kephart LCFOA Oct 06 5 Performance Improvement ILC will be pushing performance for at least several years –Currently several cavity and cryomodule variants –Seems unlikely that we could adopt an untested design variant ( e.g. cavity shape, HOM change, quad location, etc.) without both cryomodule test stand AND beam tests –At least one test facility needs beam, to validate cryomodule performance improvements –This will involve swapping modules in and out… probably not consistent with use of TTF as a user facility.

R. Kephart LCFOA Oct 06 6 Cost Reduction Changes driven by Cost Reduction –Typically these occur until the project management of an “approved” project “freezes” the design for series production –The number of objects tested is still small –The tests are less extensive, more comparative vs previous successful prototype –Many improvements to cryostat, mounts, seals, feedthrus, assembly procedures can be validated on a CM test stand without beam –Intertwined with industrial production which will produce regional differences in the cryomodule

R. Kephart LCFOA Oct 06 7 Regional manufacture When CM design is “final” the project can call for international tenders. This will lead to vendor selections and “preseries” production It will be very difficult ( but not impossible) to build identical cryomodules in all 3 regions –Manufacturing capabilities of vendors ( e.g. machine tools, weld technique, experience) –Materials availability ( standard thickness mill runs vs special order = cost, delay) –Regional availability of “specialty items… eg. Feed throughs, couplers, seals, sensors, etc.

R. Kephart LCFOA Oct 06 8 Regional manufacture Likely that we will end up with 3 different but plug compatible cryomodules Each preseries unit will require extensive testing to validate its performance and reliability prior to and during mass production of series units The number of units tested should be as large as possible (determines MTBF region that can be explored) Tests should be as realistic as possible

R. Kephart LCFOA Oct 06 9 Tests vs specific changes

R. Kephart LCFOA Oct How did other projects get burned ? Tevatron –Scrapped the first 10% of dipoles. ( constr. before complete design) – Discovered two later failures lead flexing during ramped operation cold mass sag  changing skew quad… during collider run SSC –costed and launched before they had a viable magnet design –Original magnet aperture too small –Quench protection OK for single magnet, not in string – contributed to cost escalation & ultimate project cancellation LHC magnets –LHC cost estimate based on early vendor estimates –Extensive test facility  performance seems not to be an issue –Vendor bids for series production were much larger than expected –CERN assumed part of work and much of the technical risk –Cost growth and delay (ie must validate cost for actual device built) –Transfer line… small untested vendor changes  big delays SNS –TJNL rushed delivery of modules to meet schedule –vacuum leaks during cooldown –unexpected HOM problems  rework

R. Kephart LCFOA Oct LHC String test History LHC String test was designed in 1991, in operation since It has tested several versions of the the LHC magnets and operated for 12 years.

R. Kephart LCFOA Oct Picture of LHC string test

R. Kephart LCFOA Oct Conclusions A range of Test facilities are required to validate likely changes aimed at performance improvements, cost reduction, and due to regional differences Tests should be as complete and extensive as affordable with designs frozen as soon as adequate performance is achieved These validations must take place before series production or the project faces large risks In the case of LHC ( and XFEL) the test facility is a long term investment that continues to operate well into the series production of components. Seems likely that ILC will require test facilities of similar scale.