[Sneap] terminal current surge problem

[Albert Zondervan]

Hi Riyad

Small discharges in the accelerator tube (associated with conditioning 
effects) will cause ionisation of residual gas atoms. These can then be 
accelerated away from the positive terminal (with the electrons moving 
some distance towards the terminal). Any elements that are in-line with 
the accel-tube in which such an event has occurred, will be hit by these 
ions. The magnitude of this effect depends on many factors. I see the same 
effect in my LE-side faraday cup while conditioning the EN. If it is 
bothering your operation somehow, you might try shielding the cup in 
question with a protective shroud to ground potential. 

good luck
Albert
-- 
Albert Zondervan
National Isotope Centre
GNS Science                              A.Zondervan at gns.cri.nz
PO Box 31-312, Lower Hutt                ph: +64 4 570-4617
New Zealand                              fx: +64 4 570-4657




riyad sha <riyadsha at yahoo.com>
Sent by: sneap-bounces at tunl.duke.edu
20/08/2008 18:54
Please respond to riyadsha; Please respond to Symposium of Northeastern 
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        Subject:        [Sneap] terminal current surge problem


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Hi sneaper's: 
During the operation of the 3 Mv tandem accelerator, we experience the 
following: 
When we apply the terminal voltage, the current highly fluctuate in the 
faraday cup before the accelerator tank (when it is closed or opened) even 
the source is off in the same time we noticed a decreasing in the law 
energy column current  ? this phenomenon  disappears after a time  but as 
we go up with the terminal voltage value it appears again !!! 
so any one has experience this problem or have an idea ,could help me.


Riyad Shaban
Electronic engineer 
in AECS (atomic energy commission of syria)
Accelerators Section
mob:0963-932617224
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