Dave,

I would be interested in the diamond windows (depending on how big those 4 numbers are....).  Can
you recommend a supplier?

thanks,
greg

Dave Mattey wrote:

> Kevin
>
> Have you considered using CVD diamond for a CO2 laser window?  It is the
> perfect solution (other than price) for laser fluorination as diamond is
> obviously  very tough,  transparent to a wide range of wavelengths (>70% at
> 10.6 micron), thermally highly conductive (hence immune from laser damage),
> and totally inert to fluorine or BrF5.
>
> We have used a 30mm diameter window (c. 0.5mm thick) now for nearly five
> years and the window requires only  an occasional wipe or rinse for cleaning
> between runs. The downside is that diamond is elastomer-philic and sticks
> like .... , well it forms a very good vacuum seal!
>
> Our experience with BaF2, like others, was a story of continual laser damage
> and frosting over between runs,  requiring repeated repolishing or
> replacement.  After switching to CVDD, blanks diminished, pumpout times were
> faster and the window remains clear for an entire run.
>
> Oh, and the cost I hear you ask... Prices have fallen dramatically as CVD
> production technology improves but you are looking at a four figure sum.
> The all round improvement to performance is nevertheless worth considering.
>
> Regards
>
> Dave
>
> Reader in Isotope Geology
> Director of the University of London Stable Isotope Facility
> Department of Geology,
> Royal Holloway University of London
> Egham Hill, Egham,
> Surrey TW20 0EX
>
> 07780 697564 (Mob)
> 01784 443687 (Office)
> 01784 443582 (Dept Secretary)
>
> www.gl.rhul.ac.uk/silab
>
> On 29/11/01 3:42 am, "Kevin Faure" <[log in to unmask]> wrote:
>
> > Dear Listmembers
> >
> > I am tossing-up the idea whether to buy ZnSe or BaF2 windows for our
> > CO2 laser-BrF5 extraction system. It is apparent that ZnSe has
> > several advantages over BaF2, but a little more costly. However,
> > scanning the Isogeochem archives I note that Torsten Venneman
> > commented that the ZnSe should be coated.    Is this coating for
> > reflectivity or for chemical resistance to the BrF5? If anyone has
> > experience with this I would appreciate comments on what type of
> > coating is needed.
> >
> > Thank you.
> > Kevin
> > --
> >
> > Dr Kevin Faure
> > Institute of Geological & Nuclear Sciences
> > Rafter Laboratory
> > PO Box 31-312
> > Lower Hutt
> > New Zealand
> >
> > Tel direct:     +64-4-5704638
> > Fax:    +64-4-5704657
> >

--
Dr. Greg B. Arehart
Department of Geological Sciences, MS-172
University of Nevada, Reno
Reno, NV 89557-0138
phone: 775-784-6470
fax: 775-784-1833
email: [log in to unmask]