[Sneap] Helium in Freeman Ion Source

[Leszek Wielunski]

I have used resonable He ion beam from Freeman ion source.
Yes it is difficult to get resonable beam.
One of my problems was vaccum level: I have cryo-pumps and one diffusion 
pump on this ion implanter.
Cryo-pumps do not pump well He gas and the vacuum is not good.
This is creating problems with ion beam and HV as well.
In order to avoid my problem, I have used He10% Ar90% mix as ion source gas 
(you can use as well He10% N90% mix).
This allows to operate in a resonable vacuum level and the starting of arc 
is much easer.

Dr Leszek Wielunski
Director Tandem Accelerator Laboratory
Physics and Astronomy Department
Rutgers State University of New Jersey
136  Frelinghuysen Rd
Piscataway , New Jersey  08854
USA


----- Original Message ----- 
From: "Shon B Gilliam" <sgilliam at physics.unc.edu>
To: <sneap at tunl.duke.edu>
Sent: Thursday, November 09, 2006 10:34 AM
Subject: [Sneap] Helium in Freeman Ion Source


> The SNEAP 2005 Meeting was held at Brookhaven National Laboratory.  Please 
> visit the meeting Homepage at: https://www.bnl.gov/sneap2005/default.asp
>
> The ATF-SNEAP 2006 web site is now available:
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> ++++++++++++++++++++++++++++++++++++
> We have an Eaton NV-3204 medium current ion implanter system which uses a 
> Freeman ion source. Does anyone have experience achieving a decent helium 
> beam current from a system such as this. Recently, the implanter has been 
> used for neon and carbon beams providing as much as ~100 uA and ~20 uA, 
> respectively. However, we never get more than ~10 nA from helium. Any 
> ideas about why we get so little helium beam and/or how to get much more?
>
>
> ============================
> Shon B. Gilliam
> Dept. of Physics & Astronomy
> UNC-Chapel Hill
> ============================
>
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