[Sneap] Helium in Freeman Ion Source

[Wills, John]

In general, helium is harder to ionize than other gasses and may require
much higher helium flow rate into the source to obtain "normal" beam
current. When operating on helium, how does your gas flow and arc current
and voltage  compare to  running with other gasses?

Sometimes, an arc discharge source will appear to run efficiently on helium
until any impurities or other residual gasses in the arc chamber are used
up. The source becomes more difficult to start and beam current falls off.

Best regards,

John Wills
Station 42
Atomic Energy of Canada Limited
Chalk River Laboratories
Chalk River, ON
Canada
K0J 1J0

Phone    613-584-3311   ext. 6061
FAX       613-584-8216
willsj at aecl.ca


-----Original Message-----
From: sneap-bounces at tunl.duke.edu [mailto:sneap-bounces at tunl.duke.edu]On
Behalf Of Shon B Gilliam
Sent: November 9, 2006 10:35 AM
To: sneap at tunl.duke.edu
Subject: [Sneap] Helium in Freeman Ion Source


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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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