[Sneap] Varian CF3000 - Radiation Question

[steve.poisel at vsea.com]

Daniel

The radiation is most likely coming from beam strike due to suppression.
1.9kV for the Accel tube suppression and 1.2kV for the scan suppression. 
Vent and verify connections internally.
Ensure lens has entrance and exit graphite installed.
Inspect for strange beamstrike.
Verify scan system.
The resolving aperture should have a Beryllium plate to reduce X-ray, 
Alpha and Gamma in that region
The resolving aperture should not be overly worn away.
A good indicator is to compare Accel return current from new to old on the 
same recipe.
Converging magnet pole pieces are in place on the analyzer waveguide.
If the Beamfilter is used the removable snout should be in place.
If not, remove snout, add a resistor (or not) and ground ring to terminal. 

A CF5U/CF3000 has a lead panel on the door and lead was added to the 
beamline, operator side vs a DF/CF4.
I remember being well below all 12 hour daily exposure limits at 200kV, 
1.5mA, As.

Regards,

Steve Poisel
Southwest District ? Portland
Cell                (503)577-8402
eFAX             (707)490-0928
Text Pager  (503)301-3850, 5033013850 at archwireless.net



"Daniel Goberman" <daniel.goberman at uconn.edu> 
Sent by: sneap-bounces at tunl.duke.edu
06/16/2007 12:43 PM
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[Sneap] Varian CF3000 - Radiation Question






The ATF-SNEAP 2006 meeting was held in Australia and information is 
available at:
http://www.ansto.gov.au/nugeo/conference/private/ATF_SNEAP.htm

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The SNEAP 2007 meeting will be hosted by Brigham Young University in Salt 
Lake City Utah. The meeting web site is located at:
http://webpub.byu.net/wsd/.

Greetings SNEAPers -
 
    We are trying to bring a Varian CF-3000, 200keV accelerator online 
after a few years of inactivity.  When the acceleration energy is 
increased to any value above 80keV, we begin to detect X-ray radiation 
coming from the lens box and the acceleration column.  At 80 keV the 
radiation is just above background levels, but the intensity increase with 
voltage.  Knowing the general causes of radiation, we have confirmed good 
beam focus, strong ion current on target, electron suppression is working, 
and the vacuum is about 5x10-7 Torr (in the beamline). 
    My questions to the community are: 
       1) Were these instruments (CF/DF 3000, DF-4) designed for zero 
emissions of radiation?  If so, any thoughts about what could be causing 
this particular problem would be welcomed.
       2) If some emissions are expected, does anyone have radiation 
measurements for these instruments?  Even rough numbers would be helpful 
so that we can decide if this is a problem to be solved or managed.
 
    Thanks for your thoughts!
 
     - Dan Goberman :)

-- 
Daniel Goberman, Ph.D.
Laboratory Manager: Surface Science Laboratory
University of Connecticut
Institute of Materials Science 
U-Box 3136
Storrs, CT  06269-3136
email: daniel.goberman at uconn.edu
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