1. Beam Vacuum Interconnect Design Options Ray Veness

2. 21/2/00Ray Veness LHC Vacuum Design Meeting Contents  Open Issues from String 2 design Cooling tube connections Beam screen end flaring Manufacturing costs Leak testing  Possible solutions

3. 21/2/00Ray Veness LHC Vacuum Design Meeting Open Issues following String 2 Design  Cooling tube welding Initial specification said no welds between helium and beam vacuum This is not possible using TIG on cooling tube  End flaring of beam screen Design needs 0.5 mm radially for RF contact Impossible if beam screen / cold bore gap is 0.1 mm  Manufacture of components: cost & spec. 316LN + no welds in components = expensive  Leak testing of components Achieved leak rate ~5 x 10 -8 Pa.m 3.s -1

4. 21/2/00Ray Veness LHC Vacuum Design Meeting Possible Solutions: Cooling tube welding  Brazed cap on cooling tube end (GS) Rather complex in-situ, but possible.  Part-penetrating LASER weld (PL) Works well in lab with circular welding EST/MF looking at orbital welding in-situ  ‘Swagelock’ type fittings (GS) Preliminary tests OK Would need significant design and reliability work  Pre-forming of tube ends (NK) Sample from supplier Contract being placed for prototypes Space requirement??

5. 21/2/00Ray Veness LHC Vacuum Design Meeting Possible Solutions: Beam Screen Flare  Reduce beam screen diameter (!)  Form beam screen after insertion Tolerances? Cleanliness?  Attach transition piece after insertion

6. 21/2/00Ray Veness LHC Vacuum Design Meeting Possible Solutions: Spec. and Cost  316LN  316L (!!)  Made from forged block  Make from tube? Pull ports and transitions? Allow welds in components?

7. 21/2/00Ray Veness LHC Vacuum Design Meeting Possible Solutions: Leak testing  Weld cap on each component for testing?  Have faith in materials?  Add flanges to design…

8. 21/2/00Ray Veness LHC Vacuum Design Meeting Alternative Design  Pro: Allows pre-forming or brazing on cooling tube ‘clip-on’ transitions on beam screen, so no limit on dimensions Flanges and sub-assemblies Manufacturer can make and test sub-assembly Easier to leak test in SMI 2 Allows relaxation of spec. for sub-assembly??  Con: More radial space requirement?- TBD Re-design required (time, money and risk) More components (but higher cost??)