[Sneap] Deuterium valve

[John Hunn]

There is a screw you can turn to tighten your thermal leak. Do this 
carefully or you may break it (I believe this is covered in the 
instruction sheet that comes with the valve). I found that I could 
get a negligible H or D cold leak rate by carefully adjusting the 
valve. Also use minimum pressure in the source bottle, this will also 
reduce cold leak rate.

>
>++++++++++++++++++++++++++++++++++++
>Dr. Friedrich,
>    We had similar experience at Bell Labs, with the D2+ ions mixing 
>in with analyzed 4He+.
>We could actually see the slight mass difference on a viewing screen 
>after the analyzing magnet.
>At 1.8 Mev, bending 30 degrees, the spots on the screen one meter 
>from the magnet, were ~1 mm apart.
>    We found it disturbing that the Pd metering valve was giving off 
>D2 molecules, even when
>it was COLD. We couldn't tolerate this situation, since the VdG was 
>used primarily for RBS.
>    So, we simply removed and discarded the Pd leak valve, and 
>substituted a conventional
>thermomechanical leak valve. Then we proceeded to shut off the D2 
>gas bottle (to the TM valve)
>until such time as we were ready to do the deuterium experiments.
>    This scheme, although somewhat cumbersome, solved the problem of 
>D2+ ions messing up our clean 4He+ spectra.
>
>                Walt Augustyniak
>                Dep't of Physics & Astronomy
>                Vanderbilt Univ., Nashville, TN
>
>----- Original Message ----- From: "Friedrich, Dr. habil. Manfred" 
><m.friedrich at fzd.de>
>To: "Symposium of Northeastern Accelerator Personnel" <sneap at tunl.duke.edu>
>Sent: Wednesday, January 17, 2007 5:19 AM
>Subject: [Sneap] Deuterium valve
>
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>>++++++++++++++++++++++++++++++++++++
>>Dear SNEAPers,
>>our 2 MV single ended VdG is mainly used for RBS with 1.7 MeV helium
>>ions (He+).
>>Sometimes we need also deuterium ions. Unfortunately, the deuterium
>>inlet valve (thermic needle valve) cannot be completely closed at He ion
>>operation.
>>A low fraction of D in the He ion source gas has a strong disturbing
>>influence on the RBS results due to reactions of DD+ ions.
>>Following we have removed the deuterium gas supply.
>>Does anybody know a safe closing type of valves?
>>Does anybody know a supplier for heated Pd valves?
>>M. Friedrich
>>
>>Dr. Manfred Friedrich
>>Forschungszentrum Dresden-Rossendorf e.V.
>>Institute of Ion Beam Physics and Materials Research
>>P. O. Box 51 01 19
>>D-01314 Dresden, Germany
>>Resident Address:
>>Forschungszentrum Dresden-Rossendorf e.V.
>>Bautzner Landstraße 128 (B6)
>>01328 Dresden
>>Phone: ++49 351 260 3284/3252      Fax: ++49 351 260 3285
>>e-mail:  M.Friedrich at fzd.de
>>http://www.fzd.de/FWI/FWII/
>>
>>
>>
>>
>>
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>
>
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-- 
John D. Hunn, Ph.D.                Phone:  865-574-2480
Oak Ridge National Laboratory      Fax:    865-574-4186
Bethel Valley Road                 Pager:  865-417-6576
P.O. Box 2008
Oak Ridge, TN 37831-6093           e-mail: hunnjd at ornl.gov