Update to Thread: EHT TRIPS, Please stay below 18 keV until further notice

James Conway jwc at snf.stanford.edu
Fri Apr 23 10:31:25 PDT 2004


Greetings:

Yesterday I ran at 20 keV and encountered a EHT trip after about 2 hours 
of beam on time. (Of course this was just before I was to press the Scan 
ALL button...)  This appeared as an actual EHT trip in the FE-Gun as I 
observed a slight spike in EHT current as it shut itself down.  Gun 
Vacuum remained in the 1.5E-009 mbar range and did not exhibit elevated 
levels of vacuum.

After a half hour at idle with EHT off,  I ramped back up to 18500 Volts 
and was able to resume my work and performed some test writes with no 
further EHT trips.

 The threshold of the EHT trips, and / or  arcing appears to be about 
26.5 keV, the same as the level we observed just after we brought the 
system back up.

Users are requested to carefully evaluate if they need higher 
acceleration voltages for their work.  Users are requested to operate 
the system in the range of  0.3 and 18000 volts of acceleration voltage 
and 20100 to 21000 keV.  Please do not exceed these levels.

If you experience a EHT trip:
    - Please note the voltage it tripped at in the logbook and report as 
a comment in CORAL. 
    - STOP and do not attempt to return to that voltage level that 
caused the trip, and after a 15 minute rest period to let the system 
pump, return to less than 18000 volts and resume you work if possible.
    - If the gun will not come back up after this wait period please 
call me directly my cell.

Thank you,

James Conway

 Note: BEAMER, the Hitachi HL-700 always is running at 30 keV. It  may 
also be useful for your work albeit with normal cautions and challenges 
that this system may present.

jwc at snf.stanford.edu wrote yesterday:

 Please stay below 18 keV until further notice:
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