[Sneap] RF Puzzle

[Chris Westerfeldt]

Gerhard,
    I concur with Scott.  We have had beam exit the bottle at an angle due
to mechanical alignment
errors such as the bottle not glued perpendicular to the base or the magnets
not properly centered on the exit canal. The beam starts out OK but then
bores into the side of the canal ­ the optics in that area change and the
beam no longer can be extracted.
Only other thing that I could think of would be in the probe supply itself ­
extremely high resistance limiting the current you
can extract.  Are you using the old Selenium rectifiers or have you switched
to Silicon diodes?  We typically have a ~50K series resistor in the probe
lead ­ have seen that fail (resistance goes high).
Regards,
- Chris
-- 
Chris R. Westerfeldt
Research Scientist / T.U.N.L. Radiation Safety Manager
Duke University Physics Department &
Triangle Universities Nuclear Laboratory
Science Drive, Box 90308
Durham, NC  27708-0308
Tel: (919) 660-2600
Fax: (919) 660-2634
Email: Cwest at Tunl.Duke.Edu





From: Gerhard Randers-Pehrson <gr6 at columbia.edu>
Reply-To: Symposium of Northeastern Accelerator Personnel
<sneap at tunl.duke.edu>
Date: Tue, 3 Jul 2007 13:25:51 -0400
To: 'Symposium of Northeastern Accelerator Personnel' <sneap at tunl.duke.edu>
Subject: [Sneap] RF Puzzle

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

++++++++++++++++++++++++++++++++++++

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/.


Hello all
 
Our RF ion source is acting strangely:
 
When probe voltage is applied, we get no probe current, and there is no
change in beam current which is very small.
 
With the machine open, the voltage is present on the probe cap and the
current meter indication is consistent with the meter resistance.
 
It is as though there is a resistive layer inside the cap.
 
The bottle had been in use only 6 days before this happened and worked ok
until then.
 
Any clues or cures?
 
Gerhard


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