beam current decrease?

James Conway jwconway at stanford.edu
Fri Nov 17 12:59:11 PST 2006




Hello SangBum and RAITH Users:

GREAT QUESTION for the raith at snf.stanford.edu discussion list.

Yes -- The beam current (I beam)is lower than it was with the old FE-Gun
tip.  We have been driving this FE-Gun since its installation at the
factory recommended settings conditioning and running in the FE-GUN tip. 
This conditioning has now been nearly completed and I am seeing stable
emission and great vacuum in Gun section of the column.  Emission current
of the gun is in fact still slowly increasing through the last ten days and
has gone from 0.122 nA to 0.133 nA.

As that I have been unable to get ZEISS Field service to make an
appointment,  send an experienced engineer to SNF, to increase the
Extraction Voltage and Filament Current on the FE-Gun to optimal Raith EBL
values -- I will be carefully doing this myself in small stages through the
next week before Thanksgiving.
  My target values are 0.200 - 0.225 nA at 10 keV and 30 um aperture. I have
max. limits to the extraction voltage and filament currents that I can drive
the FE-gun to in order to not burn it away or round out the tip geometry.

YOU DO NOT HAVE TO CHANGE DOSE AS YOU WILL ADJUST THE DWELL TIME OF THE
EXPOSURE TO MEET THE DOSE REQUEST IN YOUR EXPOSURE.
Remember that the area step is your dependent variable, the dose is a fixed
value, and the dwell time is the independent variable in your exposure
settings.

Hope this answers your question and if others would desire to add to this
thread just reply to raith at snf.stanford.edu.

ALL replies to JWC should ALWAYS go to jwc at snf.stanford.edu and NOT to my
web mail account that I am sending this message from.

Have a great Day!

James Conway







   Quoting SangBum Kim <kimsangb at stanford.edu>:

> Dear all,
>
>
>
>  I have a question about the status of Raith. I noticed that the beam
> current is about 0.12nA instead of 0.18nA that I used to get a few month
> ago. Can this be a problem? For example, should I change the dose?
>
>
>
> Thanks,
>
> SangBum
>
>





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