NL12 Girder Removal and Reinstallation Information provided by Danny Forehand and Greg Marble

Historical girder removal techniques Girder and associated area are cleaned/wipe down with Isopropyl Alcohol for beam line and H2O for girder pedestal and tunnel floor. Girder and associated area draped with cascading aluminum foil Flow hood placed over the work area and taped into place Technician dons head cover, clean room smock and gloves Floor covered with aluminum foil Another cleaned/wipe down with Isopropyl Alcohol and lint free wipes of connection/disconnection points (conflats) Pump cart connected to girder to allow for N2 bleed-up. Pump cart is pumped and purged with 3 atmosphere He five times prior to opening girder right angle valve Downstream and upstream cryomodules are isolated with the “warm” isolation valves Warm isolation valve on opposite end of the cryomodule being removed are also closed Girder being bled up is isolated from the cryomodule with cryomodule “warm” isolation valve Girder is bled up with He through right angle isolation valve located at the “A” ion pump. He is supplied through .5 micron inline filter. He supplied from cryogenic 3 atmosphere system Pump cart needle valve is cracked open to bleed up the girder. Girder beam-line flanges are removed from the warm isolation valves Blanks are installed on both the girder beam-line flange and the open “warm” isolation flange Girder is pumped down to UHV levels. Pump cart is disconnected from girder right angle isolation valve. Flow hood removed Girder is placed off to the side until the replacement cryomodule arrives for installation Repeat setup/procedure of flow hood and equipment at next girder to be removed.

Girder Removal for NL12 We set up on girder 1L13 first (upstream of NL12) Greg did a really thorough cleaning of the entire girder--including the removal of external magnets and associated wiring The surrounding floor area was mopped--including several feet under the end of the cryomodule The entire girder was wrapped with clean room bagging material and taped off leaving only several inches of beam-line exposed Greg built an addition to the flow hood adding a gowning area which was separate from the working area Clean room bagging material was taped to the floor extending beyond the boundaries of the flow hood The entire area inside the flow hoods were wiped with alcohol soaked lint free wipes Sticky mat was placed outside the gowning area of the flow hoods Technician used gowning area to don shoe covers, hair net, face mask, rubber gloves and clean room suit (in my opinion a smock would be sufficient for this operation) Lighthouse particle counter was in use the during the entire operation Particle counts inside the flow hood were zero before beginning operations Wiped the externals of the right angle girder isolation valve located at ion pump

Removed aluminum foil from the open flange Blew the internals of the valve (bellows on the stem side) with an ionized N2 gun connected to a nitrogen bottle (pressure of the local N2 was not sufficient for blowing off parts) The ionized N2 spraying is done IAW the C50R Ionized Nitrogen Cleaning procedure (paying attention to the Cavity Components Cleaning paragraph) C50 Ionized Nitrogen Cleaning Procedure Particle count data was monitored during this operation The counts were quite high (1000’s at .3 microns) in the beginning but recovered quickly to an acceptable range >20 @ .3microns Connected the portable slow bleed up system (to be covered later by Ari) Valve alignment was as follows: Cold isolation valves on NL11-8, NL12-1 & 8, NL13-1 and all cryomodule warm isolation valves were closed. Warm isolation valves at and around NL12 are known to leak through. Started the bleed up of the girder and cryomodule with a goal of less than 10mbar per minute. *The procedure for slow bleed up is still in development . Ion pump activity was being monitored on the upstream girder (VIP1L12A) and downstream cryomodule (VIP1L13B) while the bleed-up was progressing The ion pump activity indicated to us that cryomodule cold valve CV1L12-8 was leaking by. We immediately closed 1L12-7 and a few minutes later we had to close 1L12-6. We also had to open VBV1L13B and read vacuum pressure at VIP1L14A We lost communication with ion pump readout. After re-establishing we noticed a fault on VIP1L12B. Tried to restart with no success. Continued slow bleed up of girder 1L13 until it reached atmosphere. Secured system for the night

Upon returning in the morning we found the pressure in girder 1L13 was lower than atmosphere due to valves leaking through to cryomodule NL12 Verified that the pressure for both NL11 and NL13 were stable ( 8 & 9 range) Contacted M. Drury and discussed opening all valves associated with NL12 with the exception CV1L12-8 to equalize pressure in girder 1L12, cryomodule NL12, and girder 1L13 System equalized at 140 torr. Opened CV1L12-8 Continued bleed-up at a rate of <5 torr/min until everything reached atmosphere Wiped the flange and exposed pipe with alcohol soak rag Removed four bolts from the flange VBV1L12B Started spraying with ionized N2 while monitoring particle counts. Counts were as high as 3E4 @ .3 microns and sprayed for approximately 15 minutes to reach counts below 25 Removed the last two bolts and placed a conflat blank on the valve. Placed a conflat blank on the girder flange. Repeated for the other side Broke down the flow hood and started the procedure again on girder 1L12 Both girders were sent for further disassembly by the vacuum group The beam-line components were completely dis-assembled in the clean room and samples were gathered All the parts were cleaned by the chem techs and sent back into the clean room for re-assembly After successful re-assembly and leak check, the sub-assembly was sent back to the vacuum group for installation back onto girder

NL12 Girder ready for removal

Beam-line components from girder 1L12 This pic was taken prior to dis-assembly and sample gathering

Girder Reinstallation for NL12 The area around girder 1L13 was set up in the same manner as during girder removal The flow hoods were wiped with alcohol soaked lint free rags Technician donned the clean room garments in the same fashion Particle counts were monitored during the entire process Four bolts were removed from the blank on the warm cryomodule isolation valve Bolt holes were sprayed with ionized N2. Particle counts were monitored during this operation. The counts were not nearly as high as they were during the removal due to the fact they were just recently cleaned and sprayed Counts started in the 100’s @ the .3 micron size and came down to less than ten rather quickly Blank flange was removed from the gate valve Internals of the closed gate valve were sprayed with ionized N2 The external surfaces of the girder bellows flange was wiped with an alcohol soaked rag Blank was removed from the bellows flange on the girder. Replaced the conflat gasket and carefully made the mechanical connection using clean vacuum practices This procedure was repeated on the other side of the girder and then again on girder 1L12

A slow pump down by-pass was installed on the pump cart A slow pump down by-pass was installed on the pump cart. This is basically a metered needle valve that is plumbed in around the foreline valve on the turbopump. The valve is opened 2.5 microns, allowing the system the be roughed down at a much slower rate (<10mbar/min). The foreline valve can be fully opened at <20mbar and turbo started below 2mbar Although the setup might be slightly different than outlined, the basic slow pump down procedure is followed for all slow pumping Standard Slow Pump Down Procedure

Recommendations Continue the use of the two room flow hood that was built during this exercise At a minimum add the use of facemasks to the appropriate garments for clean assembly work Stop using aluminum foil as a cover for the girders and floor—although it can be wiped clean, aluminum is a terrible particle generator Static free clean room bagging material is a good option Always use a blank flange to cover open flanges—many flanges in the Linac only have aluminum foil over open flanges on the isolation valves Keep the blank flange tight and tape over the gap between flanges Always spray any flange being disassembled with ionized N2 after a majority of its bolts have been removed Use a live time particle counter to monitor this activity ensuring that the flange is properly sprayed Use the same ionized N2 spraying techniques to the internals on any closed valves that are having something attached Always use a slow bleed-up and slow pump-down system when evacuating or venting beam-line components