Raith Status 13:00 hours Friday January 18, 2008 -- System is UP tested and calibrated. Acceleration Voltage not to exceed 20 keV.

James Conway jwc at snf.stanford.edu
Fri Jan 18 13:39:10 PST 2008


Greetings Raith Community:

I wish to thank those individuals whom help me this past week in 
troubleshooting the components of the vacuum system on the RAITH tool.   
With all the software and set points that it takes to run the system 
when problems are encountered it can be difficult to trace to the actual 
problem.  I have added some more vacuum sensing to the system so we can 
more easily monitor vacuum levels at the mechanical pump lines.  There 
was a real team effort within the Maintenance Group here at SNF to help 
me get the system back up, which I very much appreciate.  Many Thanks!

The final diagnosis of what brought the system down Monday morning is 
that one of the bearings sets in the turbo pump, which was only two 
weeks old, had developed unusual wear and was working itself loose 
inside the pump. In continued operation it was eventually was unable to 
reach suitable speed and could not make the vacuum set point in the time 
allowed within the software. This event then tripped a automatic shut 
down into standby mode and took the pumps off line.  Initially it 
appeared to be a vacuum sense or mechanical pump thermal overheat problem.

Special Thanks also to Paul Flood at Pro-Vac, Santa Cruz, CA whom 
provided us with a qualified and tested rebuilt Turbo pump as goodwill 
and without having a PO in hand!
He will rebuild the old pump and return it to RAITH USA Inc.


*System is now up, tested, and calibrations have been checked and 
available to all users.  *
Users will note that FE-GUN emission levels and Beam Current 
measurements are quite low compared to the old tip we replaced at the 
Holiday shutdown. I expect it will take several weeks of gentle care and 
adjustments to approach the levels we had before.  Users are reminded 
that this will not change any dose delivered on the system just the time 
it takes to reach the specified exposure dose.
  I will continue to make regular adjustments increasing the Extraction 
Voltage applied to the FE-GUN until we reach normal levels.

*ALL USERS ARE RESTRICTED TO NO MORE THAN 20 keV ACCELERATION VOLTAGE 
UNTIL FURTHER NOTICE.* 
I PLAN TO BRING THIS UP TO 25 keV ON TUESDAY AFTERNOON NEXT WEEK AND 
TEST FOR 30 keV ONCE GUN VACUUM IS BELOW 8E-010 TORR LEVEL.

Thank you for your support!  Have a nice holiday weekend. 

James Conway


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