1. PillBox Cavity Update (Button Tests) Bob Rimmer NFMCC CM University of Mississippi Jan 13, 2009

2. Page 2 NFMCC CM, January 13, 2009 R. Rimmer Button Test Cell, aka LBL Pillbox “Button” system in pillbox cavity designed for easy replacement of test materials Tested so far: TiN-coated Cu & Mo, bare Mo and W To be tested: Cu (electro-polished & unpolished), Be Results to date indicate that TiN can improve performance at a given B field by somewhat more than 50% –16.5MV/m  26MV/m button 0.75  radius Molybdenum buttons Be window button holder (1.7x field enhancement factor on button surface)

3. Page 3 NFMCC CM, January 13, 2009 R. Rimmer 805 MHz Button (Pillbox) cavity Refurbished

4. Page 4 NFMCC CM, January 13, 2009 R. Rimmer 805 MHz Button Cell Status Due to problems obtaining vacuum integrity, the 805 MHz button cell is still at TJNL. –The technicians are trying again to seal the cell using newly machined Tin seals. This work is currently on-going. –Two attempts with new gaskets have had gross leaks on both large flanges and pick-up probes  First attempt seals were degreased with alcohol before assembly  Second attempt we deoxidized the tin deals to remove some slight discoloration  Torque is per Steve Virostek's tech note, gaskets are getting uniform crush but not very much on the large seal  Have checked that bolts are not bottoming out/ galling  Have checked that cover plates go metal to metal without gaskets, i.e. they are not hanging up anywhere

5. Page 5 NFMCC CM, January 13, 2009 R. Rimmer Status II Have inspected used gaskets for imprints with the following findings: –Viewport gaskets which DO SEAL have deep imprint of milled finish on cavity side, concentric groves on flange side. –Probe seals that leak have good imprint of machined grooves on cavity surface but they cross the seal path. Probe side similar to viewports –Cover seal has only light crush. Flange side shows machining marks. –Cavity side shows light imprint of polished mating surface. –Trying to get some optical microscope pictures of each. Speculation: –Probe port machining marks (from facing off the cavity end surface) cross the seal surface and although they imprint into the tin maybe there are leak paths at the bottom of the grooves. –Cover gasket does not get enough crush for material to flow. Cavity surface may be too highly polished with nothing to "key" into.

6. Page 6 NFMCC CM, January 13, 2009 R. Rimmer Path Forward Path forward: –Make a hand tool to put concentric grooves around each probe with texture similar to mating flange (fine machined finish). –Turn the cavity cover flange surface to mimic mating flange (fine machined finish). –Re-clean everything –Attempt another assembly –If still leaks consider trying narrower gasket or tin wire to increase material flow. –If leak tight on cover seals check coupling iris seal and if OK ship to FNAL.

7. Page 7 NFMCC CM, January 13, 2009 R. Rimmer Other activities: Have received Be and extended copper buttons and flat and profiled button holders for TiN coating. Coating system is available, waiting for some Ti Foil to shield RF contact surfaces as requested by Al. Should receive and start coating this week.

8. Seal 1: viewport (sealed) x4 Reverse side of seal

9. Seal 2 (probe port, did not seal) (x4) Flange side of seal

10. Seal 3 (big, did not seal) (x4) Cavity side of seal Flange side of seal