Gilles,
My concern with the Viton is that He and H2 permeation rates are much 
higher than for aluminum. This may not cause an actual vacuum problem, 
but when using a helium mass spec-type leak tester you could get leak 
indications through the Viton, making it hard to find other leaks. Also, 
o-rings should be slower to de-gas and de-water than aluminum seals.
Jon

Gilles St-Jean wrote:
>
> Hi Nabil
>
> You can replace the Al ring with a supported Viton O-ring from:
>
> A&N Corporation Headquarters
> 707 Southwest 19th Avenue • Williston, FL 32696
> Phone 352-528-4100 • Fax 352-528-3441
> Toll Free 800-352-6431
>
> Dana King, Sales Manager
> [log in to unmask] 
> <mailto:%64%6b%69%6e%67%40%61%6e%63%6f%72%70%2e%63%6f%6d>
>
> Part # LF100-400-SR-V
>
> This retrofits all instruments that have 100 size Al rings (Plus XL, 
> XP etc). You can also replace the Al ring for the Penning gauge with a 
> simple NW-25 Viton vacuum pump ring with support. The idea for the 100 
> Viton ring came from the group at Isotech Laboratories, Inc. in Illinois.
>
> Gilles
>
> Gilles St-Jean
> Chercheur / Research Scientist
> Université d'Ottawa / University of Ottawa
> Sciences de la Terre / Earth Sciences
> 140 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5
> Tel: 1-613-562-5800 xt 6830 (Bureau / Office)
> xt 6839 (Bureau / Office Lab)
> xt 6836 (IRMS lab)
> Téléc. / Fax: 1-613-562-5192
> Courriel / E-mail: [log in to unmask]
> Toile / Web: www.isotope.uottawa.ca
>
> ------------------------------------------------------------------------
>
> *De :* Stable Isotope Geochemistry [mailto:[log in to unmask]] 
> *De la part de* Nabil Saad
> *Envoyé :* 1 novembre 2007 18:20
> *À :* [log in to unmask]
> *Objet :* [ISOGEOCHEM] Delta+XP Ion Source Al seal and 253 lamp wire
>
>
> Dear all,
>
> Does any of the Delta Plus XP users know of an alternative (and 
> cheaper) source for the Ion Source Aluminum edge seal (Thermo part# 
> 0569110) and what would that part # be?
>
> Also, any alternative vendor for the 253 Lamp wire? Thermo pricing is 
> an outrageous $555.0 for a piece of metal wire and couple connectors 
> (Thermo Part# 1147320 )
>
> Thanks,
>
> Nabil
> Kinemed, Inc.
>